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Software-defined radio: a new paradigm for integrated curriculum delivery

Jeffrey H. Reed, Bilén, S.G.; Wyglinski, A.M.; Anderson, C.R.; Cooklev, T.; Dietrich, C.; Farhang-Boroujeny, B.; Urbina, J.V.; Edwards, S.H.;
Conference Paper Communications Magazine, IEEE , vol.52, no.5, pp.184,193, May 2014

Abstract

Software-defined radio is a rapidly developing field that is driving the development of and innovation in communications technology, and promises to significantly impact all communications sectors. Entities developing these SDR systems require a trained workforce that has been prepared with the mindset, knowledge, skills, and tools required to address both the system (breadth) and technical (depth) aspects of SDR systems. Developing SDRs necessarily involves a collection of disciplines including, but not limited to, electromagnetics, radio-frequency engineering, communications, digital signal processing, embedded systems, computer programming, and systems engineering. Whereas electrical engineering and computer science and engineering curricula at the university level may include courses in all of these areas, a student's typical curriculum does not; nor does it usually involve the integration of all these topics. However, SDR can be employed as an integrative construct that facilitates systems thinking and cross-domain learning via peers. In this article, we present several significant educational efforts across six U.S. universities that have developed integrated curricula in SDR, most including a significant laboratory component

Impact of intermodulation distortion on spectrum preclusion for DSA: A new figure of merit

Jeffrey H. Reed, Padaki, A.V.
Conference Paper Dynamic Spectrum Access Networks (DYSPAN), 2014 IEEE International Symposium on , vol., no., pp.358,361, 1-4 April 2014

Abstract

This paper discusses the importance of understanding the vulnerability of receivers towards intermodulation distortion. Knowledge of the RF front end non-linearity from a spectrum consumption point of view is of crucial importance in efficient spectrum management. A specific case of intermodulation distortion for Low Noise Amplifier (LNA) is studied to quantify the spectrum consumption. We show that the traditional single point IIP3 definition would render insufficient information about the extent of vulnerability to adjacent channel interference. Consequently we propose a new metric as a Figure of Merit with the inclusion of variation of IIP3 with tone spacing to quantify the LNA performance or tolerance to adjacent channel interference. Example measurements of this new FOM are presented along with the discussion on its utility and importance for efficient cognitive spectrum access.

Role of receiver performance data in efficient spectrum utilization

Jeffrey H. Reed, Padaki, A.V.; Marojevic, V.
Conference Paper Dynamic Spectrum Access Networks (DYSPAN), 2014 IEEE International Symposium on , vol., no., pp.366,369, 1-4 April 2014 doi: 10.1109/DySPAN.2014

Abstract

This paper elaborates on the importance of including receiver performance characteristics to optimize for efficient spectral usage. Futuristic heterogeneous wireless networks are expected to be diverse and dynamic. Knowledge of receiver spectral performance enables the spectrum management system not only to provide adequate protection from harmful interference, but also provides an effective way to maximize the network level spectrum efficiency for networks with diverse and dynamic environments. We formulate the problem for such an inclusive optimization with several constraints and demonstrate using numerical simulations that using receiver performance characteristics for spectrum management has the potential to considerably improve the network level spectrum efficiency.

Security and Enforcement in Spectrum Sharing

Jeffrey H. Reed, Jung-Min (Jerry) Park, A. A. (Louis) Beex, T. Charles Clancy, Vireshwar Kumar, Behnam Bahrak
Conference Paper Proceedings of the IEEE, vol. 2, issue 3, pp. 270-281, 2014 doi: 10.1109/DySPAN.2014

Abstract

When different stakeholders share a common resource, such as the case in spectrum sharing, security and enforcement become critical considerations that affect the welfare of all stakeholders. Recent advances in radio spectrum access technologies, such as cognitive radios, have made spectrum sharing a viable option for significantly improving spectrum utilization efficiency. However, those technologies have also contributed to exacerbating the difficult problems of security and enforcement. In this paper, we review some of the critical security and privacy threats that impact spectrum sharing. We propose a taxonomy for classifying the various threats, and describe representative examples for each threat category. We also discuss threat countermeasures and enforcement techniques, which are discussed in the context of two different approaches: ex ante (preventive) and ex post (punitive) enforcement.

Future Radio Spectrum Access

Jeffrey H. Reed, SM Dudley, WC Headley, M Lichtman, EY Imana, X Ma, M Abdelbar, A Padaki, A Ullah, MM Sohul, T Yang, MJ Marcus, JM Park, AA Beex, TC Clancy, V Kumar, B Bahrak, G Hattab, M Ibnkahla, WJ Chappell, EJ Naglich, C Maxey, AC Guyette, L Larson, AJ Fehske, I Viering, J Voigt, C Sartori, S Redana, GP Fettweis, L Doyle, J Kibiada, TK Forde, L DaSilva, J Villasenor, A Clegg, A Weisshaar, DB Geselowitz
Conference Paper Proceedings of the IEEE, vol. 2, issue 3, Introduction and Table of Contents, 2014

Abstract

To make spectrum sharing successful, incumbent operators must have faith in the enforcement and privacy implications for new technologies. The authors present many of the opportunities and challenges.

Practical Issues for Spectrum Management With Cognitive Radios

Jeffrey H. Reed, Dudley, S.M.; Headley, W.C.; Lichtman, M.; Imana, E.Y.; Xiaofu Ma; Abdelbar, M.; Padaki, A.; Ullah, A.; Sohul, M.M.; Taeyoung Yang
Conference Paper Proceedings of the IEEE , vol.102, no.3, pp.242,264, March 2014

Abstract

The policy of permanently assigning a frequency band to a single application has led to extremely low utilization of the available spectrum. Cognitive radio, with its ability to be both intelligent and frequency agile, is thought to be one of the prime contenders to provide the necessary capabilities needed for dynamic spectrum access systems. With this in mind, this paper discusses the practical issues inherent to the deployment of spectrum management systems utilizing cognitive radios.

Relaxing Pre-Selector Filter Selectivity Requirements Using Cognitive RF Front-End Control

Jeffrey H. Reed, Eyosias Yoseph Imana, Taeyoung Yang
Conference Paper Analog Integrated Circuits and Signal Processing March 2014, Volume 78, Issue 3, pp 705-716

Abstract

This paper proposes the use of a cognitive engine to control the local oscillator and sampling frequencies in a flexible receiver RF front-end. The analysis in this paper shows that this cognitive engine has the potential to relax selectivity requirement of the pre-selector filter in receiver RF front-end. The cognitive engine is designed by modeling the RF front-end in channelized spectrum domain. The paper also develops a new spectrum occupancy model to evaluate the performance of the approach. Theoretical analysis and simulations are also carried out using the developed model. The results show that the designed cognitive engine can enable a poorly selective receiver to behave similar to highly selective receiver. Furthermore, this paper analyzes the computational complexity of the designed cognitive engine.

OTRA-THS MAC to Reduce Power Outage Data Collection LatencyIn SSmart Meter Setwork

Jeffrey H. Reed, Garlapati, S.; Kuruganti, T.; Buehrer, M.R.
Conference Paper Computing, Networking and Communications (ICNC), 2014 International Conference on , vol., no., pp.776,781, 3-6 Feb. 2014

Abstract

The deployment of advanced metering infrastructure by electric utilities poses unique communication challenges, particularly as the number of meters per aggregator increases. When there is a power outage, a smart meter tries to report it instantaneously to the electric utility. In a densely populated residential/industrial locality, it is possible that a large number of smart meters simultaneously try to get access to the communication network to report the power outage. If the number of smart meters is very high on the order of tens of thousands (metropolitan areas), the power outage data flooding can lead to Random Access CHannel (RACH) congestion. Several utilities are considering the use of cellular network for smart meter communications. In 3G/4G cellular networks, RACH congestion not only leads to collisions, retransmissions and increased RACH delays, but also has the potential to disrupt the dedicated traffic flow by increasing the interference levels (3G CDMA). In order to overcome this problem, in this paper we propose a Time Hierarchical Scheme (THS) that reduces the intensity of power outage data flooding and power outage reporting delay by 6/7th, and 17/18th when compared to their respective values without THS. Also, we propose an Optimum Transmission Rate Adaptive (OTRA) MAC to optimize the latency in power outage data collection. The analysis and simulation results presented in this paper show that both the OTRA and THS features of the proposed MAC results in a Power Outage Data Collection Latency (PODCL) that is 1/10th of the 4G LTE PODCL.

Open Source Software-Defined Radio Tools For Education, Research, And Tapid Prototyping

Jeffrey H. Reed, Jason Snyder, Deepan Seeralan, Shereef Sayed, Jeffery Wilson, Carl B. Dietrich, Stephen H. Edwards
Conference Paper International Journal on Software Tools for Technology Transfer, February 2014, Volume 16, Issue 1, pp 67-80

Abstract

Software-defined radios (SDR) offer several advantages over traditional, hardware-based radios, most notably flexibility and reconfigurability. Developing SDR applications can be a difficult process, however, for several reasons. First, much of the work involved deals with standards compliance, rather than radio functionality. This portion of the work is very detailed and error prone, leading to wasted time and effort. Second, there is little to no support available for the debugging and refinement portions of the development cycle. There is no easy way to monitor or control SDR applications at runtime. The Waveform Workshop was created to address these issues. A part of the OSSIE SDR project, the Waveform Workshop drastically reduces the time and effort involved in SDR development. It automatically generates the portions of the software related to standards compliance, letting developers concentrate on radio functionality. In addition, the Waveform Workshop provides tools for both monitoring and controlling SDR applications at runtime, making debugging much easier.

Opportunistic Channel Allocation Decision Making In Cognitive Radio Communications

Jeffrey H. Reed, Hazem Shatila, Mohamed Khedr
Conference Paper International Journal of Communication Systems Volume 27, Issue 2, pages 216–232, February 2014

Abstract

The global spread of wireless devices with mobile Internet access and the increasing demand of multimedia-based applications are fueling the need for wireless broadband networks. IEEE 802.16 and 802.20 are standards for a broadband wireless access with promising cognitive radio features to support mobile Internet access. However, because of the fast changing radio environment and the demand for dynamic spectrum allocation mechanisms, these standards must continuously readjust different radio parameters. The cognitive radio makes decisions based on its built-in inference engine, which also in time can adapt itself to different situations through the process of learning from experience. In this paper we present an automated opportunistic decision making and learning process for cognitive radio based on uncertainty reasoning algorithms. This novel approach is well suited in fast changing wireless environments with vague, incomplete, and heterogeneous information. Theory and simulations prove that decision making and learning of the cognitive radio based on the proposed approach cope with the changes in the radio environment. In this work we use fuzzy logic for the learning and decision making of the cognitive radio. Simulation also show that our approach provides accurate and precise decisions on allocating spectrum to mobile Internet users even in fast varying radio conditions.

Practical Issues for Spectrum Management With Cognitive Radios

Jeffrey H. Reed, Stephen M Dudley, William Christopher Headley, Marc Lichtman, Eyosias Yoseph Imana, MA XIAOFU, Mahi Abdelbar, Aditya Padaki, Abid Ullah, Munawwar M Sohul, Yang, Taeyoung,
Conference Paper Proceedings of the IEEE, Volume 102, Issue 3, Pages 242-264

Abstract

The policy of permanently assigning a frequency band to a single application has led to extremely low utilization of the available spectrum. Cognitive radio, with its ability to be both intelligent and frequency agile, is thought to be one of the prime contenders to provide the necessary capabilities needed for dynamic spectrum access systems. With this in mind, this paper discusses the practical issues inherent to the deployment of spectrum management systems utilizing cognitive radios.

Vulnerability of LTE to Hostile Interference

Jeffrey H. Reed, Marc Lichtman, T. Charles Clancy, Mark Norton
Conference Paper arXiv preprint arXiv:1312.3681

Abstract

LTE is well on its way to becoming the primary cellular standard, due to its performance and low cost. Over the next decade we will become dependent on LTE, which is why we must ensure it is secure and available when we need it. Unfortunately, like any wireless technology, disruption through radio jamming is possible. This paper investigates the extent to which LTE is vulnerable to intentional jamming, by analyzing the components of the LTE downlink and uplink signals. The LTE physical layer consists of several physical channels and signals, most of which are vital to the operation of the link. By taking into account the density of these physical channels and signals with respect to the entire frame, as well as the modulation and coding schemes involved, we come up with a series of vulnerability metrics in the form of jammer to signal ratios. The ``weakest links'' of the LTE signals are then identified, and used to establish the overall vulnerability of LTE to hostile interference.

A Variation-Aware Approach For Task Allocation In Wireless Distributed Computing Systems

Jeffrey H. Reed, Xiaofu Ma; Volos, H.I.; Xiangwei Zheng; Bose, T.,
Conference Paper Globecom Workshops (GC Wkshps), 2013 IEEE , vol., no., pp.5006,5011, 9-13 Dec. 2013

Abstract

Wireless distributed computing (WDC) enables the radio nodes with reduced computing abilities to cooperate in processing complex computational tasks for minimizing the overall processing latency (makespan). However, the uncertainty of the dynamic mobile wireless environment, which is not an issue for the traditional distributed computing, poses a challenge for WDC. In this paper, a variation-aware approach for WDC is proposed to determine the task allocation by considering the heterogeneous computing capability of the radio nodes as well as the impact of the radio environment. To this end, the transmission latency is characterized as a random variable that depends on the channel fading and the transport protocol. A variation-aware task graph analysis is proposed for the estimation of the makespan's distribution. The evolutionary algorithms are employed for the allocation mapping. We use simulation results to affirm makespan estimation improvement of the proposed approach compared with the traditional deterministic approach, and give insights on the dominating factors for the improvement.

Planning and Response In The Aftermath Of A Large Crisis: An Agent-Based Informatics Framework

Jeffrey H. Reed, Barrett, C.; Bisset, K.; Chandan, S.; Jiangzhuo Chen; Youngyun Chungbaek; Eubank, S.; Evrenosoglu, Y.; Lewis, B.; Lum, K.; Marathe, A.; Marathe, M.; Mortveit, H.; Parikh, N.; Phadke, A.; Rivers, C.; Saha, S.; Stretz, P.; Swarup, S.; Thorp, J.; Vullikanti, A.; Dawen Xie
Conference Paper Simulation Conference (WSC), 2013 Winter , vol., no., pp.1515,1526, 8-11 Dec. 2013

Abstract

We present a synthetic information and modeling environment that can allow policy makers to study various counter-factual experiments in the event of a large human-initiated crisis. The specific scenario we consider is a ground detonation caused by an improvised nuclear device in a large urban region. In contrast to earlier work in this area that focuses largely on the prompt effects on human health and injury, we focus on co-evolution of individual and collective behavior and its interaction with the differentially damaged infrastructure. This allows us to study short term secondary and tertiary effects. The present environment is suitable for studying the dynamical outcomes over a two week period after the initial blast. A novel computing and data processing architecture is described; the architecture allows us to represent multiple co-evolving infrastructures and social networks at a highly resolved temporal, spatial, and individual scale. The representation allows us to study the emergent behavior of individuals as well as specific strategies to reduce casualties and injuries that exploit the spatial and temporal nature of the secondary and tertiary effects. A number of important conclusions are obtained using the modeling environment. For example, the studies decisively show that deploying ad hoc communication networks to reach individuals in the affected area is likely to have a significant impact on the overall casualties and injuries.

Automatic Modulation Classification Under IQ Imbalance Using Supervised Learning

Jeffrey H. Reed, Lichtman, M.; Headley, W.C.
Conference Paper Military Communications Conference, MILCOM 2013 - 2013 IEEE , vol., no., pp.1622,1627, 18-20 Nov. 2013

Abstract

The process of classifying digital modulation schemes given IQ imbalance at the transmitter or receiver is studied using fourth and sixth order cumulants as features. Various methods of supervised learning are proposed in order to mitigate the effect of IQ imbalance at the receiver, including K-Nearest Neighbors (k-NN), Support Vector Machine (SVM), and decision tree learning. The impact of IQ imbalance at the transmitter is also observed, as well as the effect of IQ imbalance on the theoretical cumulant values for each modulation scheme. Through simulation, it is shown that supervised learning approaches are effective at compensating for the IQ imbalances that can occur at the receiver

Performance Evaluation of Hybrid Spread Spectrum Based Advanced Smart Metering Infrastructure Network With Multi-User Detection Techniques in Jamming Channel

Jeffrey H. Reed, Garlapati, S.; Monir Vaghefi, R.; Buehrer, M.R
Conference Paper Wireless Sensors and Sensor Networks (WiSNet), 2013 IEEE Topical Conference on , vol., no., pp.154,156, 20-23 Jan. 2013

Abstract

A recent research study compared different possible technologies like RF mesh, Power Line Carrier (PLC), GPRS, 3G cellular CDMA and arrived at a conclusion that the 3G cellular CDMA is an appropriate choice for smart metering application. A related work proposed a Hybrid Spread Spectrum (HSS) based Advanced smart Metering Infrastructure (AMI) network which reduces the MAC layer overhead, latency in data transfer from source to destination and improves the PHY layer security when compared to that of the 3G cellular CDMA. In this paper, we evaluate and compare the performance of the HSS based AMI network with and without Multi-User Detection (MUD) techniques in the presence of a jammer

PHY and MAC Layer Design of Hybrid Spread Spectrum Based Smart Meter Network

Jeffrey H. Reed, Garlapati, S.; Volos, H.I.; Kuruganti, T.; Buehrer, M.R.;
Conference Paper Performance Computing and Communications Conference (IPCCC), 2012 IEEE 31st International , vol., no., pp.183,184, 1-3 Dec. 2012

Abstract

The selection of the appropriate communication technology for different smart grid applications has drawn a great attention in the recent past. In this paper, we propose a Hybrid Spread Spectrum (HSS) based Advanced smart Metering Infrastructure (AMI) that reduces the overhead and latency in data transfer when compared to the use of 3G/4G technologies for smart meter data collection. We present a preliminary PHY and MAC layer design of a HSS based AMI network and evaluate their performance using matlab and NS2 simulations.

Cultivating Emerging and Black Swan Technologies

Jeffrey H. Reed, Roop L. Mahajan, Rolf Mueller, Christopher B. Williams, Thomas A. Campbell and Naren Ramakrishnan
Conference Paper ASME 2012 International Mechanical Engineering Congress and Exposition, Volume 6: Energy, Parts A and B. November 9–15, 2012

Abstract

Emerging technologies, defined as contemporary cutting-edge developments in various fields of technology, are generally associated with the potential for large impact on society. In a recent op-ed, “The coming Tech-led Boom” (Wall Street Journal, January 30, 2012), Mills and Ottino list three grand technological transformations — big data, smart manufacturing, and the wireless revolution — poised to transform this century as much as telephony and electricity did in the 20th century. This list is by no means comprehensive and most likely misses technologies that are not yet recognized, but may still carry an extreme impact — i.e., the so-called Black Swans, as defined by New York Times best-selling author, Nassim Nicholas Taleb, in his book, The Black Swan. Taleb cites the example of three recently implemented technologies that most impact our world today — the Internet, the computer, and the laser — and notes that all three were unplanned, unpredicted, and unappreciated upon their discovery, and remained unappreciated well after initial use.

Development of an Open-Source GSM Ffemtocell and Integrated Core Infrastructure

Jeffrey H. Reed, Tsou, T.; Cooper, T.; McGwier, R.; Clancy, T.C.
Conference Paper MILITARY COMMUNICATIONS CONFERENCE, 2012 - MILCOM 2012 , vol., no., pp.1,6, Oct. 29 2012-Nov. 1 2012

Abstract

Open source development applied to cellular GSM technology is a fairly recent, but growing, concept. Another trend is the continually growing capability of low-power embedded processors, which makes them increasingly suitable for open source GSM applications. This paper applies two open source software packages, OpenBTS and OpenBSC, to an readily available embedded hardware platform, the Universal Hardware Radio Peripheral (USRP) E100. The USRP E100 device is a heterogeneous processor platform designed for software-defined radio use. The result is an embedded base station that can be deployed in standalone configuration or as part of a larger GSM network. A software radio transceiver implementation is presented that leverages optimized capabilities of all available processors: a general purpose ARM processor, DSP, and FPGA. Comparative performance measures are also provided.

Antenna Design Strategy and Demonstration for Software Defined Radio

Jeffrey H. Reed, Taeyoung Yang, William A. Davis,Warren L. Stutzman, S. M. Shajedul Hasan, Randall Nealy, Carl B. Dietrich
Conference Paper SDR'10, November 30-Dec.3, 2010

Abstract

Antennas are a key enabling technology for software-defined radio (SDR). Although software is extremely flexible, SDR’s potential is limited by antenna size and performance. In this paper, we review typical antenna miniaturization techniques and fundamental theories that limit antenna size and performance including operational bandwidth, gain (or range), and radiation pattern. Possible antenna design strategies are discussed to meet the desired specifications in SDR based on observations from the limit theories. The application of strategies to enable multiband (resonant), continuous multiband (frequency independent), and instantaneous, ultra-wideband antennas are discussed qualitatively. Advantages, disadvantages, and design trade-off strategies for different types of antennas are compared from a system-level perspective. A design example for a compact ultra-wideband (UWB) antenna is presented for a software-defined platform. The example involves a direct-conversion radio developed in Wireless@VT that uses a Motorola RFIC having a 100 MHz–6 GHz operational frequency range with a 9 kHz–20 MHz channel bandwidth. The example antenna covers frequencies from 450 MHz to 6 GHz instantaneously with approximately 5-dBi realized gain over a finite-size ground plane, including return loss and omni-directional coverage.

Case Study: Security Analysis of a Dynamic Spectrum Access Radio System

Jeffrey H. Reed, Newman, T.R.; Clancy, T.C.; McHenry, M.
Conference Paper Global Telecommunications Conference (GLOBECOM 2010), 2010 IEEE , vol., no., pp.1,6, 6-10 Dec. 2010

Abstract

Dynamic Spectrum Access technology is now well beyond the developmental stages that it was several years ago. Several prototype devices have been created and have been successfully demonstrated at various venues. Recently the FCC has approved the decision for moving ahead with allowing white space devices to operate in the same frequency bands as TV transmitters. Through rigourous testing the FCC has validated the fundamental concept of these DSA radios showing that they can avoid primary users and cause a minimal amount of interference in trusted wireless environments. However, wireless environments can not always be trusted to contain naturally occuring features. Malicious users may introduce false environments such as increased noise levels or emulated primary user signals, in order to fool the DSA device. These uncontrolled environments must be explored in order to develop and embed proper security protocols within these next-generation devices to prevent future security issues. Even in the case of IEEE 802.11, the commercial world found that the security threats were severely overlooked, causing developers to play catch up while many systems were, and still are, left vulnerable. In this paper, we provide a security analysis on a well established DSA radio developed by Shared Spectrum Company under the DARPA xG program. Our analysis demonstrates the unique security vulnerabilities associated with DSA protocols and expose the extremely low barrier required for a malicious user to exploit them if not security measures are in place. We identify several of these unique vulnerabilities and suggest methods for mitigating them.

Detecting Unauthorized Software Execution in SDR Using Power Fingerprinting

Jeffrey H. Reed, Gonzalez, C.R.A.;
Conference Paper MILITARY COMMUNICATIONS CONFERENCE, 2010 - MILCOM 2010 , vol., no., pp.2211,2216, Oct. 31 2010-Nov. 3 2010

Abstract

Software-defined radios (SDRs) are able to adapt to unforeseen circumstances with a simple software update. This ability reduces development and maintenance time, but it also makes them susceptible to malicious software attacks. An exploit in SDR can potentially expose sensitive information or disrupt critical communications infrastructure. It is crucial for the success of SDR to develop adequate mechanisms to maintain execution integrity and reduce the impact of compromised systems. A novel approach called power fingerprinting has been proposed as an effective solution to provide independent integrity assessment in SDR. Power fingerprinting relies on monitoring the dynamic power consumption and using pattern recognition to detect any deviations from authorized code execution. In this paper, we present the results of two feasibility experiments performed on a basic commercial radio platform to evaluate the applicability of power fingerprinting in security areas. The results demonstrate the ability of power fingerprinting to discriminate between the execution of test code involving encrypted and unencrypted transmissions.

Energy Efficiency in Selective Decode and Forward Cooperative Communication

Jeffrey H. Reed, Gonzalez, C.R.A.; Palat, R.C.; Annamalai, A.
Conference Paper Sarnoff Symposium, 2010 IEEE , vol., no., pp.1,5, 12-14 April 2010

Abstract

Cooperative communication systems that exploit spatial diversity to improve the performance of end-to-end communication in ad hoc wireless networks have gained a lot of attention in recent years. In this article, we examine the energy efficiency of a simple selective decode and forward (SDF) protocol. Different from previous studies on energy efficiency our analysis accounts for the imperfect regeneration at the relay. We show that the cooperative system using the SDF protocol can achieve higher energy efficiency than a single-input-single-output (SISO) transmission when the transmit-power consumed by the power amplifiers become higher than the total power consumed by the analog circuitry at the nodes.

Survey of Cognitive Radio Architectures

Jeffrey H. Reed, Amanna, A.
Conference Paper IEEE SoutheastCon 2010 (SoutheastCon), Proceedings of the , vol., no., pp.292,297, 18-21 March 2010

Abstract

Cognitive Radio and Cognitive Networking are emerging fields of research that has the potential for transformative changes to the current status quo. Cognitive systems utilize environmental observations such as spectrum or network conditions to change operational configurations in order to optimize performance at individual node or over end-to-end goals. This paper surveys some of these origin cognitive frameworks and correlates these frameworks to cognitive radio implementations of today. Several definitive implementations and cognitive radio architectures are reviewed and compared. This paper also identifies area of need and suggests directions forward for novel research in this area through interdisciplinary collaboration with the cognitive sciences, integrating prediction and proactive operation into cognitive radio/network architectures and identifying less researched artificial intelligence algorithms that show promise towards cognitive radio architecture.

Onboard Cognitive Radio Architecture For Space Assets Communication

Jeffrey H. Reed, Raghunandan, S.; Sayed, S.; Bose, T.
Conference Paper Aerospace Conference, 2010 IEEE , vol., no., pp.1,11, 6-13 March 2010

Abstract

Modeling the space environment of a planet including three dimensional dynamic "imaging" of the magnetosphere warrants the use of constellations of many spacecrafts. Communication among the various space assets and exchange of mission data for more efficient storage and analysis call for a dynamic and reliable technology capable of managing ad-hoc requests subjected to system and environmental constraints. In this paper, we propose a cognitive radio architecture that can be used as an extension to space based software defined radio. Simulink is used to demonstrate the behavioral model of a system that represents the executable specifications. In order to illustrate some of the key features of the architecture, a basic model has been created in Simulink. This modeling would enable future implementation of the architecture and support any debugging or restructuring.

Wideband RF Front End Design Considerations For a Flexible White Space Software Defined Radio

Jeffrey H. Reed, Shajedul Hasan, S.M.; Nealy, R.; Brisebois, T.J.; Newman, T.R.; Bose, T.
Conference PaperRadio and Wireless Symposium (RWS), 2010 IEEE , vol., no., pp.484,487, 10-14 Jan. 2010

Abstract

This paper introduces a flexible RF front end for whitespace communication. The designed front end can operate over any frequency from 100 MHz to 2.5 GHz and the channel bandwidth can be programmable from 4.5 kHz to 10 MHz. This large frequency range and wide bandwidth makes this hardware suitable for implementing most wireless standards. A direct conversion RFIC developed by Motorola, drives the core of the RF front end. The various RF parameters can be changed by programming this RFIC through a serial peripheral interface (SPI). As part of this work we further develop an intelligent software driver to control different parameters of the RFIC. Thus the combination of highly flexible front end and flexible software driver makes this hardware an excellent choice for whitespace devices. The performance of this front end has been tested and measured and has been integrated into a daughterboard format for the Universal Software Radio Peripheral (USRP), a hardware device which enables the rapid design and implementation of software defined radio (SDR).

Cross-layer Resource Allocation For Wireless Distributed Computing Networks

Jeffrey H. Reed, Xuetao Chen; Hasan, S.M.; Bose, T.
Conference PaperRadio and Wireless Symposium (RWS), 2010 IEEE , vol., no., pp.605,608, 10-14 Jan. 2010

Abstract

The allocation of communication power consumption and computing rate is inherently one of the cross-layer problems in wireless distributed computing networks (WDCNs). This paper exploits a subgradient approach to choose the optimal power-rate pair for maximizing the network computing capability and minimizing the power consumption. The impact of heterogeneous channel conditions for different nodes are modeled as a penalty term in the objective function to balance the performance and power consumption, and increase the amount of the power for the computing task. Simulation results show that both energy efficiency and the distributed computing power ratio (DCPR) can be increased by considering the wireless channel conditions. These results provide some guidelines for designing the protocol dedicated to WDCNs.

Cognitive Engine Architecture for Railway Communications

Jeffrey H. Reed, Ashwin Amanna, Matthew J. Price, Soumava Bera, Manik Gadhiok
Conference PaperASME 2010 Rail Transportation Division Fall Technical Conference, Roanoke, Virginia, USA, October 12–13, 2010

Abstract

This paper discusses a railway specific cognitive radio that builds upon software defined radio (SDR) platforms to adapt the radio based situational awareness. Cognitive Radio incorporates artificial intelligence based algorithms with reconfigurable software-defined radios that enable automatic adjustments of the radio to improve performance and overcome obstacles the radio may confront in the field (i.e. environmental/man-made interference, occupying the same channel as a user with higher priority, etc.). This paper describes the Railway Cognitive Radio (Rail-CR) architecture and illustrates preliminary results in simulation. The proposed cognitive engine architecture consists of a case-based reasoned (CBR) and a Genetic Algorithm (GA) optimization routine. This paper discusses the overall cognitive architecture, the relationship between the CBR and the GA based on weighted objective functions, and metrics for assessing performance. Methods for case representation, quantifying similarity between cases histories, and techniques for managing case growth rate are presented as well as a proposed test bed SDR platform.

Implementation and Evaluation of Laboratory/Tutorial Exercises for Software Defined Radio Education

Jeffrey H. Reed, Carl B Dietrich, Frank E Kragh, SM Hasan, C Aguayo Gonzalez, Adeyemi A Adenariwo, Haris I Volos, Cecile C Dietrich, Donna L Miller, Jason Snyder, Stephen H Edwards
Conference PaperProceedings of the 2010 ASEE Southeast Section Conference

Abstract

Software defined radio (SDR) integrates several areas of electrical engineering, computer engineering, and computer science. Graduate courses at the Naval Postgraduate School and Virginia Tech survey SDR concepts and enabling technologies and provide hands-on experience via a project-oriented approach. The institutions have developed exercises that use the OSSIE open source SDR software, based on the Software Communications Architecture (SCA), an open U.S. Department of Defense standard and prevalent industry approach to SDR engineering. The exercises are suitable for use in university and short courses, and for individual study. Introductory exercises reinforce SDR and SCA concepts while familiarizing students with SDR infrastructure and rapid prototyping tools and preparing students for design and implementation projects. Later exercises include development of SDR broadcast receivers and digital transceivers, remote monitoring of SDR applications, and distributed SDR applications. The exercises are assessed based on retrospective pre- and post-tests, student evaluations, and analysis of download data.

Rail-CR: Cognitive Radio for Enhanced Railway Communication

Jeffrey H. Reed, Ashwin Amanna, Manik Gadhiok, Matthew J. Price, W. Pam Siriwongpairat and T. Kee Himsoon
Conference Paper2010 Joint Rail Conference, Volume 1 Urbana, Illinois, USA, April 27–29, 2010

Abstract

Robust, reliable, and interoperable wireless communications play a vital role in the success of railroad operations. This paper describes an effort towards developing a railroad-specific “cognitive radio” (Rail-CR) that can meet the needs of future wireless communication systems for railways by making positive train control (PTC) communication more interoperable, robust, reliable, and spectrally efficient, and less costly to deploy and maintain. Cognitive radios are a cutting edge research area that combines artificial intelligence (AI) with Software Defined Radios (SDRs) with the goal of improving upon existing radio performance. SDRs are radios in which capabilities are flexible due to realizing some functionality in software as opposed to a purely hardware platform. By utilizing situational awareness from the radio in the form of observable parameters, often known as ‘meters’, a cognitive engine (CE) utilizes software-based decision-making algorithms to determine if a change in the radio parameters, commonly referred to as ‘knobs’, is required based on sets of predefined goals. Additionally, learning algorithms dovetail with the decision making to enable the system to track and utilize past decisions and observations.

Waveform Level Computational Energy Management in Software Defined Radios

Jeffrey H. Reed, Dinesh Datla, Thomas Tsou, Tim Newman,and Tamal Bose
Conference PaperSDR’09 Technical Conference and Product Exposition. Washington, DC: SDR

Abstract

Unlike traditional digital radios, where the waveforms are implemented in low power hardware such as ASICs, software defined radio (SDR) designs have to be concerned with the waveform computational complexity. Consequently, in SDRs, where the system power consumption is influenced by both the computational as well as communication hardware power consumption, it is important to understand the tradeoff between the two power consumption components. In this paper, we exhibit the tradeoff in the context of channel coding where the decoder complexity can impact the transmit power required in order to meet a given bit-error-rate (BER). Specifically, we consider viterbi decoding and soft-in-soft-out (SISO) BCJR iterative decoding of minimum shift keying (MSK) symbols where the traceback length and the number of iterations of the decoder can be tweaked in order to vary the computational execution time.

The Impact of Channel Variations on Wireless Ddistributed Computing Networks

Jeffrey H. Reed, Xuetao Chen; Newman, T.R.; Datla, D.; Bose, T.;
Conference PaperGlobal Telecommunications Conference, 2009. GLOBECOM 2009. IEEE , vol., no., pp.1,6, Nov. 30 2009-Dec. 4 2009

Abstract

Wireless distributed computing has several unique problems compared with currently well investigated wireless sensor networks. These problems include the impact of channel variation on power allocation, different traffic pattern with higher utilization, and more restricted delay constraints. This paper investigates the impact of communication channel condition on the average execution time of the computing task within wireless distributed computing networks (WDCN). It has been found that the delay performance of wireless distributed computing is influenced by both the average channel condition and the variation of channels. In addition, the impact of channel heterogeneity is also investigated to show the possibility of the optimal workload distribution for energy saving and robustness. Finally, a workload distribution approach combined with a power allocation scheme exploiting the spatial heterogeneity of the channel condition is proposed to balance energy efficiency and robustness.

Protecting the Primary User's Operational Privacy in Spectrum Sharing

Jeffrey H. Reed, Bahrak, B.; Bhattarai, S.; Ullah, A.; Jung-Min Park; Gurney, D.,
Conference Paper Dynamic Spectrum Access Networks (DYSPAN), 2014 IEEE International Symposium on , vol., no., pp.236,247, 1-4 April 2014

Abstract

Although using geolocation databases is a practical approach for enabling spectrum sharing, it poses a potentially serious privacy problem. Secondary users (queriers), through seemingly innocuous queries to the database, can determine the types and locations of incumbent systems operating in a given region of interest, and thus compromise the incumbents' operational privacy. When the incumbent systems (primary users) are commercial systems, this is typically not a critical issue. However, if the incumbents are federal government systems, including military systems, then the information revealed by the databases can lead to a serious breach of operational privacy. In this paper, we propose privacy-preserving mechanisms and techniques for an obfuscated geolocation database that can enable the coexistence of primary and secondary users while preserving the operational privacy of the primary users.

Power Fingerprinting In SDR & CR Integrity Assessment

Jeffrey H. Reed, Gonzalez, C.R.A.;
Conference Paper Military Communications Conference, 2009. MILCOM 2009. IEEE , vol., no., pp.1,7, 18-21 Oct. 2009

Abstract

Integrity assessment plays a critical role in the security and regulatory certification of software-defined radio (SDR) and cognitive radio (CR). We propose a novel approach to assess the execution status of SDR and CR by monitoring their dynamic power consumption. The approach relies on extracting distinctive power consumption signatures, or fingerprints, and then using pattern recognition techniques to determine if they match expected behavior. This approach provides an external, independent monitor for assessing the integrity of SDR and CR. Feasibility experiments are encouraging and show the correct identification of basic software routines using discriminatory features extracted from the time domain.

Power Efficiency in Wireless Network Distributed Computing

Jeffrey H. Reed, Datla, D.; Xuetao Chen; Newman, T.R.; Bose, T.,
Conference Paper Vehicular Technology Conference Fall (VTC 2009-Fall), 2009 IEEE 70th , vol., no., pp.1,5, 20-23 Sept. 2009

Abstract

Advanced wireless applications such as sensor networks involve a close interaction between the communication and computation processes that deliver the services under stringent power constraints. Wireless network distributed computing (WNDC) is a potential solution to reducing the power consumption per node as well as that of the network. In WNDC, a computational task is executed among a network of collaborative nodes in a distributed manner as against performing the same task on a single node. In addition to providing power savings, WNDC enables power demand-supply matching that allows for system operation under a constrained power supply such as solar power. This paper presents fundamental power efficiency analysis of WNDC. The conditions for achieving power demand-supply matching and positive network power savings under power and computational latency constraints are derived. The results show the impact of non-linearity in the computational system characteristics and the communication overhead on the power savings.

A Hybrid Cognitive Engine for Improving Coverage in 3G Wireless Networks

Jeffrey H. Reed, Morales-Tirado, L.; Suris-Pietri, J.E.
Conference Paper Communications Workshops, 2009. ICC Workshops 2009. IEEE International Conference on , vol., no., pp.1,5, 14-18 June 2009

Abstract

Third generation (3G) wireless networks have been well studied and optimized with traditional radio resource management techniques, but still there is room for improvement. Cognitive radio (CR) technology can bring significant network improvements by providing awareness to the surrounding radio environment, exploiting previous network knowledge and optimizing the use of radio resources using machine learning and artificial intelligence techniques. Cognitive radio can also co-exist with legacy equipment thus acting as a bridge among heterogenous communication systems. In this paper, we present a hybrid cognitive radio engine for 3G wireless networks. The engine is designed using case-based reasoning (CBR) and decision tree (DT) searches, as the main blocks to the engine's reasoning, learning and optimization functions. The engine model was implemented and tested via simulation, it was applied to improve coverage in the network.

On Video Multicast in Cognitive Radio Networks

Jeffrey H. Reed, Donglin Hu; Shiwen Mao
Conference Paper INFOCOM 2009, IEEE , vol., no., pp.2222,2230, 19-25 April 2009

Abstract

We investigate the challenging problem of enabling multicast video service in emerging cognitive radio (CR) networks. We propose a cross-layer optimization approach to multicast video in CR networks. Specifically, we model CR video multicast as an optimization problem, while considering important design factors including scalable video coding, video rate control, spectrum sensing, dynamic spectrum access, modulation, scheduling, retransmission, and primary user protection. The objective is to optimize the overall received video quality as well as achieving proportional fairness among multicast users, while keeping the interference to primary users below a prescribed threshold. Although the problem can be solved using advanced optimization techniques, we propose a sequential fixing algorithm and a greedy algorithm with low complexity and proven optimality gap. Our simulations using MPEG-4 fine grained scalability (FGS) demonstrate the efficacy and superior performance of the proposed approach as compared with an alternative equal allocation scheme.

Interference Effects of Non-Ideal Dynamic Spectrum Access on Primary and Secondary User Capacities

Jeffrey H. Reed, Datla, D.; Newman, T.; Bose, T.
Conference Paper Digital Signal Processing Workshop and 5th IEEE Signal Processing Education Workshop, 2009. DSP/SPE 2009. IEEE 13th , vol., no., pp.212,217, 4-7 Jan. 2009

Abstract

Dynamic spectrum access (DSA) technology can improve the spectrum utilization significantly and is the key solution to the spectrum scarcity problem. In a typical DSA scenario, the secondary user (SU) is required to co-exist with the primary user (PU) in a non-interfering manner. However, the SU's spectrum sensing limitations can result in erroneous secondary transmissions that can affect the PU's capacity. In this paper, we model the interference caused by the SU to the PU and simulate the resulting capacity loss experienced by the PU. The trends in the PU and SU capacities that occur with variation in the system parameters such as transmit SNR, PU - SU spatial separation and the spectrum sensing time have been discussed. The results presented in this paper show that the capacity loss of the PU as well as the SU due to DSA interference is insignificant when limits are placed on the SU system parameters. Furthermore, the maximum effective throughput that can be achieved by the SU under such limited operation is also computed.

A High Efficiency Outphasing Transmitter Structure for Wireless Communications

Jeffrey H. Reed, Xuetao Chen; Bose, T.; An He
Conference Paper Digital Signal Processing Workshop and 5th IEEE Signal Processing Education Workshop, 2009. DSP/SPE 2009. IEEE 13th , vol., no., pp.212,217, 4-7 Jan. 2009

Abstract

An outphasing radio transmitter can provide high linearity. The overall system efficiency for an outphasing transmitter is constrained by the combiner at the output stage. The combiner efficiency can be as low as 20% for an OFDM signal due to its high peak-to-average power ratio (PAPR). We propose a digital signal processing approach to improve the average system efficiency of an outphasing transmitter from 20% to about 80%. The efficiency improvement is achieved by combining PAPR reduction technique with the outphasing transmitter structure. The efficiency achieved by this approach can be optimized according to the probability density functions of the input signals. This new approach is insensitive to the mismatch of the two branches in the outphasing structure.

Specific Emitter Identification for Cognitive Radio with Application to IEEE 802.11

Jeffrey H. Reed, Kyouwoong Kim; Spooner, C.M.; Akbar, I.
Conference Paper Global Telecommunications Conference, 2008. IEEE GLOBECOM 2008. IEEE , vol., no., pp.1,5, Nov. 30 2008-Dec. 4 2008

Abstract

Cognitive radio (CR) is believed to be an enabling technology for increasing spectrum efficiency. A CR collects spectrum usage information from not only its own spectrum sensing module, but also from peer CRs. The heavy dependence on spectrum knowledge from other CRs requires identification of malicious CR devices that could generate spoofed information. In addition, it also needs to track the users associated with problematic CR devices which unintentionally violate spectrum usage etiquette. The specific emitter identification (SEI) concept is applied to identification of such non-cooperative CR devices. In this paper, second-order cyclic features of OFDM signals are proposed as a means of increasing CR network security and stability through SEI. For this exploratory work, IEEE 802.11a/g signals from different WLAN cards are measured and classified using hidden Markov Models (HMMs).

On Concurrent Transmissions in Multi-Hop Wireless Networks with Shadowing Channels

Jeffrey H. Reed, Seung Min Hur; Shiwen Mao; Kwanghee Nam
Conference Paper Communications, 2008. ICC '08. IEEE International Conference on , vol., no., pp.2662,2666, 19-23 May 2008

Abstract

In this paper, we study the exposed terminal problem in multi-hop wireless networks with log-normal shadowing channels. Assuming that location information is known, we first calculate the success probability for the concurrent transmissions from exposed nodes. We then propose a new MAC protocol which schedules concurrent transmissions in the presence of log- normal shadowing, thus mitigating the exposed terminal problem and increasing network throughput. The performance of the proposed protocol is evaluated with ns-2 simulations, and it is shown to achieve considerable improvements in both end-to-end throughput and delay over the IEEE 802.11 MAC.

Precise Error Rate Analysis of Bandlimited BPSK System with Timing Errors and Cochannel Interference Under Generalized Fast Fading Channels

Jeffrey H. Reed, Palat, R.C.; Annamalai, A.;
Conference PaperVehicular Technology Conference, 2008. VTC Spring 2008. IEEE , vol., no., pp.1306,1310, 11-14 May 2008

Abstract

This paper develops an efficient analytical framework for evaluating the average bit-error probability (ABER) of bandlimited coherent binary phase shift keying (BPSK) in generalized fast fading channels, where the fading rate is approximately equal to the symbol rate, subject to timing errors and asynchronous cochannel interferers. Selected simulation and computational results are presented that are of interest for outdoor microcellular and macrocellular system studies. Aside from this, our ABER results also serve as lower performance bounds for practical realizable receivers (where ideal coherent detection is difficult to implement) and as an upper performance bound for bandlimited BPSK in slow fading channels where the fading rates are much slower than the symbol rate.

Efficient Computation of Information Outage Probability and Ergodic Capacity of OSTBC System

Jeffrey H. Reed, Palat, R.C.; Annamalai, A.;
Conference PaperVehicular Technology Conference, 2008. VTC Spring 2008. IEEE , vol., no., pp.1306,1310, 11-14 May 2008

Abstract

Outage probability and ergodic capacity are important performance measures of communication systems over fading channels. Point-to-point communication systems are known to achieve tremendous improvements in channel capacity when MIMO schemes are applied. In this paper we investigate an efficient Fixed-Talbot algorithm for numerical Laplace inversion and apply it to evaluate the outage probability and ergodic capacity of OSTBC system. The framework developed can be applied to a wide range of fading distributions (including Rice, Nakagami-m, Nakagami-Hoyt and Weibull stochastic channel models) with unequal channel gains and also to independent and non-identically distributed (i.n.d) MIMO channels.

Log-Likelihood-Ratio based Selective Decode and Forward Cooperative Communication

Jeffrey H. Reed, Palat, R.C.; Annamalai, A.;
Conference PaperVehicular Technology Conference, 2008. VTC Spring 2008. IEEE , vol., no., pp.1306,1310, 11-14 May 2008

Abstract

This paper presents exact ABER performance analysis for selective decode and forward (SDF) cooperative diversity system with BPSK modulation under Rayleigh fading where the relay has a MAP based receiver and the retransmission is based on log- likelihood-ratio (LLR) threshold. We also derive the optimum LLR threshold that minimizes ABER performance. It is shown that the LLR relay based SDF cooperative diversity system performs better than a SNR threshold based SDF system with lower implementation complexity than lambda-MRC and C-MRC schemes.

Joint Power Control and Waveform Adaptation for Distributed Networks

Jeffrey H. Reed, Menon, R.; MacKenzie, A.B.; Buehrer, R.M.
Conference PaperGlobal Telecommunications Conference, 2007. GLOBECOM '07. IEEE , vol., no., pp.694,699, 26-30 Nov. 2007

This paper presents a joint power control and waveform adaptation algorithm for networks with non-colocated receivers, amenable to a distributed implementation. The proposed algorithm allows users to meet their target signal to interference plus noise ratio (SINK) requirements while reducing the transmit power-levels in the network. The performance of the algorithm is investigated via theoretical-analysis and simulations. It is shown that the joint algorithm results in better solutions than a pure power-control or a pure waveform adaptation algorithm.

Memory Usage of a Software Communication Architecture Waveform

Jeffrey H. Reed, Philip J Balister, Carl Dietrich
Conference PaperSDR Forum Technical Conference, Denver, CO, 2007

One question commonly asked about software defined radios is “How much memory do I need?”. While the answer depends greatly on the software framework and underlying operating system, this paper describes tools used to measure memory usage on a Linux based system running the OSSIE SCA framework. In addition to the conventional tools commonly used to study memory usage, this paper introduces the exmap and exmap- console tools for performing detailed memory usage measurements.

Performance Evaluation of Radio Environment Map-Enabled Cognitive Spectrum-Sharing Networks

Jeffrey H. Reed, Youping Zhao; Raymond, David; da Silva, Claudio; Midkiff, S.F.,
Conference PaperMilitary Communications Conference, 2007. MILCOM 2007. IEEE , vol., no., pp.1,7, 29-31 Oct. 2007

In recent years, cognitive radio (CR) has been introduced as a new paradigm for enabling much higher spectrum utilization by dynamically accessing and sharing the spectrum with incumbent radio devices. This paper proposes an innovative and practical spectrum-sharing approach and evaluates its performance. The goal is to minimize CR's harmful interference to incumbent primary users and to maximize the utility of spectrum-sharing networks by exploiting the proposed radio environment map (REM). REM-enabled CR adaptation algorithms are developed for various operational environments, namely, the open area and the dense urban area. This paper also compares the performance gain when using the Global REM and the Local REM, respectively. The impact of imperfect REM information due to node mobility and REM dissemination delay is simulated. By exploiting the REM information, CR can make situation-aware adaptations in transmit power, transmit timing, routing protocol, and topology, thereby reducing interference to primary users. More importantly, the painful hidden node or hidden receiver problem can be mitigated with the help of the Global REM. REM-enabled CR could be a cost-efficient and reliable approach to "waterfilling" underutilized spectrum in both space and time domains.

Inter-Cell Interference Coordination/Avoidance for Frequency Reuse by Resource Scheduling in an OFDM-Based Cellular System

Jeffrey H. Reed, Seok Ho Won; Hyeong Jun Park; Neel, J.O.
Conference PaperVehicular Technology Conference, 2007. VTC-2007 Fall. 2007 IEEE 66th , vol., no., pp.1722,1725, Sept. 30 2007-Oct. 3 2007

This paper proposes and evaluates a new method for mitigating inter-cell interference. We show that the proposed method results in a minor degradation of block error rate under low traffic loading but results in significant improvements for high traffic loads. We also propose and compare two options for resource re-allocation following allocation conflicts: immediate (synchronous) re-allocation and round-robin re-allocation. Simulation results indicates that round-robin reallocation results in good BLER performance when the traffic load is high.

A Location-Assisted MAC Protocol for Multi-Hop Wireless Networks

Jeffrey H. Reed, Seung Min Hur; Shiwen Mao; Hou, Y.T.; Kwanghee Nam
Conference PaperWireless Communications and Networking Conference, 2007.WCNC 2007. IEEE , vol., no., pp.322,327, 11-15 March 2007

It has been shown in prior work that when used in multi-hop wireless networks, the 802.11 MAC suffers low throughput performance, especially when the number of hops is large. This paper clarifies the relation between exposed node and interference range, and proposes a location-assisted MAC protocol that schedules concurrent transmissions in a multi-hop wireless network. In the proposed algorithm, after identifying a node as an exposed node, a simple procedure is executed to validate the concurrent transmission of the exposed node (called scheduled transmission). Based on location information, the scheduled transmission is allowed if the current and scheduled transmitters are out of the interference range of each other's target receiver. Simulation results show that the proposed algorithm can effectively improve the throughput of multi-hop wireless networks.

Multi-rate Synchronization of Digital Receivers in Software-Defined Radios

Jeffrey H. Reed, Joseph Gaeddert, Haris I Volos, Drew Cormier
Conference PaperProceeding of the SDR 07 Technical Conference and Product Exposition, 2007

This paper describes a multi-rate synchronizer that makes use of a polyphase filter bank to simultaneously perform matched-filtering and interpolation to correct for symbol timing offsets observable on a sampled-data receiver. Interpolation between available sample points is achieved by selecting the appropriate filter in the bank which provides the optimal sampling time. Furthermore, carrier phase error is corrected by adding a second control loop to drive a numerically-controlled oscillator before matched filtering, mitigating distortion caused by any carrier offset. This design is tractable for burst-mode transmissions where symbol timing and carrier frequency/phase acquisition is necessary for each data frame and allows for symbol timing and carrier offset estimators to be used in conjunction with the loop control architecture provided. Simulations under various timing and carrier impairments are provided.

CTH15-6: Efficient ABER Analysis of Bandlimited Cooperative Communication under Time Synchronization Errors

Jeffrey H. Reed, Palat, R.C.; Annamalai, A.;
Conference PaperGlobal Telecommunications Conference, 2006. GLOBECOM '06. IEEE , vol., no., pp.1,5, Nov. 27 2006-Dec. 1 2006

Distributed multiple-input-multiple-output system (e.g., inter-cluster communication via cooperating nodes in a wireless network) is a topic of emerging interest. Much of previous studies assume perfect synchronization among cooperating nodes and identically distributed communication links. Such assumptions are rarely valid in practical operating scenarios. This paper develops an efficient analytical framework for computing average bit error rate of a distributed multiple-input-single- output (MISO) space-time coded system with intersymbol interference (due to imperfect location predictions and clock jitters between cooperating nodes, as well as the choice of data pulse shaping filters) over generalized fast fading channels. We show that under certain conditions distributed MISO system can outperform perfectly synchronized single-input-single-output (SISO) system.

WSN15-4: A Game-Theoretic Framework for Interference Avoidance in Ad hoc Networks

Jeffrey H. Reed, Menon, R.; MacKenzie, A.B.; Buehrer, R.M.;
Conference PaperGlobal Telecommunications Conference, 2006. GLOBECOM '06. IEEE , vol., no., pp.1,6, Nov. 27 2006-Dec. 1 2006

A framework to construct convergent interference avoidance (IA) algorithms in networks with multiple distributed receivers (as in ad hoc networks) based on potential game theory is developed in this paper. This is motivated by the fact that direct extensions of distributed greedy IA techniques for centralized networks to these de-centralized networks do not always lead to convergence. Some channel conditions that lead to non-convergence are also identified in the paper. A waveform adaptation algorithm for IA, designed on the basis of the framework, is then proposed. It is shown that this algorithm leads to a reduction of the interference in the network and also incorporates fairness in the allocation of resources.

Radio Environmnet Map Enabled Situation-Aware Cognitive Radio Learning Algorithms

Jeffrey H. Reed, Youping Zhao, Joseph Gaeddert, Kyung K Bae
Conference PaperGlobal Telecommunications Conference, 2006. GLOBECOM '06. IEEE , vol., no., pp.1,6, Nov. 27 2006-Dec. 1 2006

This paper presents an innovative and generic approach to developing cognitive radios (CR) based on the radio environment map (REM). REM is envisioned as an integrated database consisting of multi-domain information, which supports global cross-layer optimization by enabling CR to “look” through various layers. The REM, as a vehicle of network support to CR, can be exploited by the cognitive radio engine (CE) for various cognitive functionalities such as situation awareness, reasoning, learning, planning and decision support. This paper presents the system flow and framework of REM-enabled situation-aware learning algorithms. Simulations demonstrate the effectiveness and efficiency of REM-enabled CR learning algorithms. Furthermore, by sharing information about the radio environment through REM dissemination, the hidden node problem can be mitigated and the secondary users can coexist with primary users (PUs) with minimal harmful interference. Link level and network level simulations are conducted with MATLAB and NS-2, respectively.

A LOW COST MULTI-BAND/MULTI-MODE RADIO FOR PUBLIC SAFETY

Jeffrey H. Reed, SM Hasan, P Balister, K Lee, S Ellingson
Conference PaperSDR Forum Technical Conference, Orlando, FL, 2006

Existing radio communications systems employed in public safety applications today are a disparate mix of equipment operating at frequencies ranging from 25 MHz to 4.99 GHz and using modes ranging from basic analog FM to VoIP. This has created a frustrating and potentially dangerous problem in that first responders from different organizations are often unable to communicate effectively. Existing solutions to this problem are predominately network-based, which requires prior planning and coordination. So, it is desirable to implement some degree of user-based interoperability; that is, to have some radios which are capable of operating in any system without the aid of network-based infrastructure. Such radios would need to be able to operate in any frequency band using any mode that might be encountered. In this paper, we describe the requirements for such a radio and consider technical feasibility issues. Specifically, we consider a software defined radio (SDR) approach in which the radio uses a small number of RF front ends, each having relatively wide bandwidth and with tuning range sufficient to access most spectrum relevant to public safety communications. Also, two different types of baseband processing strategies will be compared to assess the advantages and disadvantages of Software Communication Architecture (SCA)-based SDR for public safety applications.

A LOW COST MULTI-BAND/MULTI-MODE RADIO FOR PUBLIC SAFETY

Jeffrey H. Reed, SM Hasan, P Balister, K Lee, S Ellingson
Conference PaperSDR Forum Technical Conference, Orlando, FL, 2006

Existing radio communications systems employed in public safety applications today are a disparate mix of equipment operating at frequencies ranging from 25 MHz to 4.99 GHz and using modes ranging from basic analog FM to VoIP. This has created a frustrating and potentially dangerous problem in that first responders from different organizations are often unable to communicate effectively. Existing solutions to this problem are predominately network-based, which requires prior planning and coordination. So, it is desirable to implement some degree of user-based interoperability; that is, to have some radios which are capable of operating in any system without the aid of network-based infrastructure. Such radios would need to be able to operate in any frequency band using any mode that might be encountered. In this paper, we describe the requirements for such a radio and consider technical feasibility issues. Specifically, we consider a software defined radio (SDR) approach in which the radio uses a small number of RF front ends, each having relatively wide bandwidth and with tuning range sufficient to access most spectrum relevant to public safety communications. Also, two different types of baseband processing strategies will be compared to assess the advantages and disadvantages of Software Communication Architecture (SCA)-based SDR for public safety applications.

Performance of Distributed Dynamic Frequency Selection Schemes for Interference Reducing Networks

Jeffrey H. Reed, Neel, J.O.
Conference PaperMilitary Communications Conference, 2006. MILCOM 2006. IEEE , vol., no., pp.1,7, 23-25 Oct. 2006

One of the more commonly envisioned algorithms for cognitive radios is spectrum filling via dynamic frequency selection. Applying the cognitive radio design framework, we formalize a low complexity distributed ad-hoc dynamic frequency selection algorithm that converges to near-minimal interference frequency re-use patterns. We then examine the performance of this algorithm in the presences of practical considerations such as intra-network policy variations and timing issues and show that while this leads to situations that violate the framework, the steady-state and convergence properties of the framework are still preserved.

On the use of Pilot-Assisted Matched Filtering in UWB Time-Interleaved Sampling

Jeffrey H. Reed, Venkatesh, S.; Anderson, C.R.; Buehrer, R.M.
Conference Paper Ultra-Wideband, The 2006 IEEE 2006 International Conference on , vol., no., pp.119,124, 24-27 Sept. 2006

A software defined radio for ultra wideband (UWB) communication systems places several stringent requirements on the analog-to-digital converter (ADC). In particular, the ADC must have sufficiently high sampling frequency-typically on the order of several gigasamples per second-to accurately reconstruct the received UWB pulse. An alternative approach to using a single expensive ADC with the above features is to sample the received signal with an array of lower speed ADCs driven by time-interleaved (TI) sampling clocks, allowing the array to operate as if it were a single ADC with a much higher effective sampling frequency. However, ADC timing, gain and offset mismatches represent significant design challenges in such architectures. In this paper, we investigate the use of a pilot-based matched-filter architecture in mitigating the impact of ADC gain, offset, and timing mismatches. The analytical results derived in this paper (a) demonstrate the efficacy of a pilot-based matched filter in mitigating the impact of timing mismatch errors on a TI-ADC array, and (b) allow for the design specification of the number of pilots required in order to achieve desired system performance

Node Density and Range Improvement in Cooperative Networks using Randomized Space-Time Block Coding with Time Synchronization Errors

Jeffrey H. Reed, Palat, R.C.; Annamalai, A.
Conference PaperSensor Array and Multichannel Processing, 2006. Fourth IEEE Workshop on , vol., no., pp.466,470, 12-14 July 2006

Cooperative communication in energy-constrained networks is a topic of emerging interest in recent years especially for sensor network applications. We consider cooperative transmission from a cluster of nodes to a remote receiver. The transmission protocol used is randomized orthogonal space-time block coding, which allows each node to randomly transmit one column of a given orthogonal space-time code matrix. Previous work on the topic has shown that the scheme can achieve maximum possible diversity order for a given SNR as the number of cooperating nodes increases. In this paper we examine the range extension achievable under realistic conditions accounting for time synchronization errors and use of pulse shaping filters. We show that the scaling of range as the number of nodes increase with timing error is not linear. It reaches a limit beyond which range improvement is not significant.

Upper Bound on Bit Error Rate for Time Synchronization Errors in Bandlimited Distributed MIMO Networks

Jeffrey H. Reed, Palat, R.C.; Annamalai, A
Conference PaperWireless Communications and Networking Conference, 2006. WCNC 2006. IEEE , vol.4, no., pp.2058,2063, 3-6 April 2006

Distributed multiple-input-multiple-output system (e.g., inter-cluster communication with cooperating nodes in a wireless sensor network) is a topic of emerging interest. Much of the previous studies in this area, however, assumed perfect synchronization among cooperating nodes and identically distributed communication links. Such assumptions are rarely valid in practical operating scenarios. This paper develops an analytical framework for computing an upper bound on the average bit error rate of a distributed space-time coded system with inter-symbol interference (due to imperfect location predictions and clock jitters between cooperating nodes and choice of data pulse shaping filters) over generalized fast fading channels. As an illustrative example, the performance of 2x1 multiple-input-single-output system that uses distributed orthogonal space-time block coding is presented, although this approach can be readily extended to analyze distributed transmit maximal ratio diversity and other variants of space-time schemes.

A Software Defined Ultra Wideband Communication System Testbed

Jeffrey H. Reed, Christopher R. Anderson
Conference PaperVirginia Space Grant Consortium Student Research Conference, 2006

Software Defined Radios (SDR) have the potential of changing the fundamental usage model of wireless communications devices, but the capabilities of these transceivers are often limited by the speed of the underlying ADCs, DSPs, and FPGAs. A SDR receiver provides tremendous flexibility and rapid prototyping capabilities over a fixed hardware implementation. Such a receiver has the capability of supporting multiple data rates, modulation or multiple access schemes, can adapt to the propagation environment, and is capable of operating with a variety of waveforms and communication standards. Currently, state-of-the-art Impulse Ultra Wideband (UWB) communication systems are composed of custom-developed hardware, and do not use SDR architectures. Several major challenges are involved in developing such a communication system— such systems require extremely high sampling rates, generate huge amounts of sample data, and require a tremendous amount of digital processing power. These challenges are particularly daunting when Commercially available Off-The-Shelf (COTS) components are used in the development of such a system. In this paper, we investigate the development of a UWB SDR Transceiver Testbed based around an 8 GHz-8 ADC Time Interleaved Sampling array. The overall objective is to develop a testbed that will allow researchers to evaluate different UWB modulation, multiple access, and coding schemes, and will support raw data rates of up to 100 MB/s.

Effect of Phase Offset on the Probability of Error of Two Co-Channel MSK Signals

Jeffrey H. Reed, Ahmed, Y.; Buehrer, R.M.,
Conference Paper9th International Multitopic Conference, IEEE INMIC 2005 , vol., no., pp.1,3, 24-25 Dec. 2005

In this paper we derive exact mathematical expressions for the probability of error of minimum shift keying (MSK) in presence of a co-channel interferer. We show that the probability of error of MSK is highly dependant on the phase difference between the two signals and with proper phase offset the two signals are quasi-orthogonal. The mathematical expressions derived here are validated through Monte-Carlo simulations

Cooperative relaying for ad-hoc ground networks using swarm UAVs

Jeffrey H. Reed, Palat, R.C.; Annamalau, A.
Conference PaperMilitary Communications Conference, 2005. MILCOM 2005. IEEE , vol., no., pp.1588,1594 Vol. 3, 17-20 Oct. 2005

Low cost UAVs have proved valuable in their use as sensor data collection systems in tactical situations. In this paper we examine their use as communication relays to improve range and reliability of ad hoc ground based network. MIMO based wireless communications are well known to improve capacity and reliability of point-to-point communication links. Recently, cooperation between distributed wireless nodes has been studied to exploit multi user macro diversity in an adhoc network. Application of MIMO techniques using distributed wireless nodes are also envisioned, where the cooperating nodes become the virtual antennas of a MIMO transceiver. Inspired by the recent advances in multi-UAV formation flights, we study the application of such distributed MIMO based relay schemes on a cluster of multiple UAVs. Specifically we look at the performance of distributed transmit beamforming and distributed OSTBC schemes under ideal and non ideal conditions of UAV flight. Simulation parameters are chosen based on literature study of air-to-ground propagation models. The results from our simulations show tremendous improvements in range and reliability when compared to direct ground based communication links.

Flow routing for variable bit rate source nodes in energy-constrained wireless sensor networks

Jeffrey H. Reed, Hou, Y.T.; Yi Shi; Sohraby, K.,
Conference PaperCommunications, 2005. ICC 2005. 2005 IEEE International Conference on , vol.5, no., pp.3057,3062 Vol. 5, 16-20 May 2005

We consider a two-tier wireless sensor network and focus on the flow routing problem for the upper tier aggregation and forwarding nodes (AFNs). Assuming each AFN is equipped with directional antennas for transmission, we are interested in how to perform flow routing at each node such that the network lifetime is maximized. We present a flow routing algorithm that provably has the following properties: (1) when the average source rate of each AFN is known a priori, the flow routing algorithm is optimal and gives maximum network lifetime performance; (2) when the average source rate of each AFN is unknown but is within a fraction, ε, of an estimated rate value, then the network lifetime given by the proposed flow routing algorithm is no more than 2ε/(1-ε) from optimal. As a result, the proposed flow routing algorithm can provide predictable lifetime performance, even when the source bit rate can be time-varying.

A game-theoretic framework for interference avoidance in ad hoc networks (2005)

Jeffrey H. Reed, Rekha Menon , Allen B. Mackenzie , R. Michael Buehrer , Rekha Menon , Allen B. Mackenzie , R. Michael Buehrer ,
Conference PaperGlobal Telecommunications Conference, 2006. GLOBECOM ’06. IEEE

It is shown in this paper that direct extensions of distributed greedy Interference Avoidance (IA) techniques for networks with centralized receivers to networks with multiple uncoordinated receivers (as in ad-hoc networks) do not always lead to convergence and some channel conditions that lead to non-convergence are identified. A framework based on potential game theory is presented which could be used to construct convergent IA games in these de-centralized networks. Example waveform adaptation games for IA are formulated according to this framework. It is shown that these convergent games lead to the maximization of global network objectives.

GAME THEORY AND INTERFERENCE AVOIDANCE IN DECENTRALIZED NETWORKS

Jeffrey H. Reed, Rekha Menon, A MacKenzie, R Buehrer
Conference PaperSDR Forum Technical Conference, 2005

In networks with transmitting users having separate uncoordinated receivers, waveform adaptation by greedy interference avoidance (IA) algorithms ([1], [2] and [3]) might not lead to fair network resource allocations. A game theoretic framework for this scenario, based on Potential game theory is presented in this paper. This model provides insight into development of algorithms that are fairer than the greedy IA algorithms and are amenable to distributed implementations.

Reverse link capacity and interference statistics of DS/CDMA with transmit diversity

Jeffrey H. Reed, Jong-Han Kim; Bae, K.K.; Annamalai, A.; Tranter, W.H.
Conference PaperVehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th , vol.6, no., pp.4320,4324 Vol. 6, 26-29 Sept. 2004

This paper examines the impact of spatial diversity implementations at both mobile handset and base stations on the interference statistics and capacity of a reverse-link direct sequence code division multiple access (DS/CDMA.) system. Several parameters that can affect the capacity are considered: transmit diversity order, spatial receive diversity order, the number of multipath channels, fade distribution and multiple intensity profile, maximum transmit power, soft-handoff, and user distribution.

Sub-band beamforming for OFDM system in practical channel condition

Jeffrey H. Reed, Alam, F.; Cheung, B.L.P.; Mostafa, R.; Newhall, W.G.; Woerner, B.D.
Conference PaperVehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th , vol.1, no., pp.235,239 Vol. 1, 26-29 Sept. 2004

Orthogonal frequency division multiplexing (OFDM) is a multi-carrier technique that has recently received considerable attention for high speed wireless communication and ad hoc networks. In this paper we develop a simple pilot symbol assisted frequency domain beamforming technique for the OFDM receiver. The weight vector estimated with the proposed scheme cancels strong interference and minimizes channel impairments. We investigate different aspects of the beamforming technique in a simple AWGN environment. The performance of the proposed beamforming scheme is demonstrated for a vector channel based on actual measurement data. The applicability of computationally simple least mean square (LMS) algorithm instead of the recursive least square (RLS) algorithm is also investigated in this paper.

Performance evaluation of 2D RAKE algorithms for WCDMA-DL applications at the handset

Jeffrey H. Reed, Mostafa, R.; Khanna, P.; Woo Cheol Chung; Jin Woo Heo; Reed, J.H.; Ha, D.S.
Conference PaperRadio and Wireless Conference, 2004 IEEE , vol., no., pp.367,370, 19-22 Sept. 2004

Several 2D RAKE algorithms have been evaluated for performance improvement over a conventional single antenna RAKE receiver at the handset for WCDMA downlink air interface. The main focus of the research is to study the feasibility of smart antenna algorithms for handset application and to identify the best candidate algorithm in terms of performance improvement (BLER) and relative hardware complexity (power and area requirements on a chip). The candidate algorithms are based on the following performance metrics: maximum signal-to-noise ratio (MSNR), maximum signal-to-interference-plus-noise ratio (MSINR) and minimum mean squared error (MMSE). The algorithms have been investigated for hardware complexity based on TSMC 0.18 μm technology. 3GPP specified propagation channels and test conditions have been employed to evaluate coded BLER performance. The improvement in error rate performance combined with relative hardware complexity are used to assess the feasibility of an algorithm for handset applications.

A model-based approach to demodulation of co-channel MSK signals

Jeffrey H. Reed, Ahmed, Y.; Reed, J.H.; Tranter, W.H.; Buehrer, R.Michael
Conference PaperGlobal Telecommunications Conference, 2003. GLOBECOM '03. IEEE , vol.5, no., pp.2442,2446 vol.5, 1-5 Dec. 2003

In this paper, we present model-based techniques for joint detection of two near equal power co-channel MSK signals. It is shown that an MSK signal is piecewise linear in the parameters of interest and therefore can be represented in the standard linear form. The problem of joint detection is then reduced to one of parameter estimation and this allows us to develop receiver architectures based on the minimum variance and minimum mean square error criterion. Simulation results have shown that model-based techniques provide a performance gain of about 12 dB for equal power signals and about 8-10 dB when the signals are near equal power (SIR∼1dB) over the conventional correlation receiver.

Wideband air-to-ground radio channel measurements using an antenna array at 2 GHz for low-altitude operations

Jeffrey H. Reed, Newhall, W.G.; Mostafa, R.; Dietrich, C.; Anderson, C.R.; Dietze, K.; Joshi, G.
Conference PaperMilitary Communications Conference, 2003. MILCOM '03. 2003 IEEE , vol.2, no., pp.1422,1427 Vol.2, 13-16 Oct. 2003

Wideband measurements were performed using a direct-sequence spread-spectrum measurement system in the air-to-ground radio environment to characterize propagation between an airborne transmitter and a ground-based receiving antenna array at a center frequency of 2.05 GHz. The transmitter was flown along constant-radius arcs at low altitudes around the receiver location to obtain measurement results for 7.5, 15, 22.5, and 30 degree elevation angles. An 80 megachip per second (Mcps) modulating PN sequence was transmitted by the airborne station. The receiver was located in a campus environment of four- to six-story buildings and rolling terrain. The receiver used a four-element antenna array and sampled received signals at 1 gigasample per second (Gsps) per channel. Power-delay profiles that approximated channel impulse responses were used to measure magnitude, phase, and delay of multipath signal components received at each element. Characterization parameters produced from the measurements include RMS delay spread, excess delay spread, multipath fading CDFs, antenna diversity gain, and gain achieved through spatial-temporal combining. The measurements presented here support analysis of wireless systems for intentional transmissions, such as data communications between ground nodes and low-altitude aircraft. In addition, these measurements support investigations into interference from ground sources to low-altitude aircraft (e.g., on instrument approaches) or interception of signals originating from ground sources.

Wideband characterization of wireless channels for smart antenna applications

Jeffrey H. Reed, Mostafa, R.; Dietze, K.; Ertel, R.B.; Dietrich, C.; Reed, J.H.; Stutzman, W.L.,
Conference Paper Radio and Wireless Conference, 2003. RAWCON '03. Proceedings , vol., no., pp.103,106, 10-13 Aug. 2003

Coherence bandwidth is an important propagation parameter that has direct impact on the design and performance of a wireless communications link contemplating performance enhancement features like smart antenna applications. This paper presents wideband characterization for indoor and outdoor-to-indoor channels and wideband vector channel measurements for an indoor environment. The results show that the coherent bandwidth of about 10 MHz associated with indoor channel can accommodate diversity operations for wideband CDMA (W-CDMA) system. In addition, a study of the envelope cross-correlation points to the feasibility of a smart antenna system. For outdoor-to-indoor channel, the coherence bandwidth indicated that some additional temporal processing would be necessary for a W-CDMA system. Existing narrowband systems, however, would suffice to use simple diversity techniques in such a channel.

Reduced complexity MIMO processing for WLAN (IEEE 802.11b) applications

Jeffrey H. Reed, Mostafa, R.; Robert, M
Conference Paper Radio and Wireless Conference, 2003. RAWCON '03. Proceedings , vol., no., pp.171,174, 10-13 Aug. 2003

In this paper, we propose and evaluate a reduced complexity multiple-input-multiple-output (MIMO) system to enhance signal to noise ratio (SNR) and throughput of a WLAN system. The algorithm is based on phase scanning at the transmitter side and maximal ratio combining (MRC) at the receiver side with feedback from the receiver to assist in setting the optimal phase value at the transmitter. This feedback channel is available in the IEEE 802.11b standard, and thus, the proposed algorithm introduces minor modifications to the existing air interface. Simulation results show that the proposed technique increases the throughput sustainability of an 802.11b system.

An overview of configurable computing machines for software radio handsets

Jeffrey H. Reed, Srikanteswara, S.; Palat, R.C.; Athanas, P.,
Conference Paper Communications Magazine, IEEE , vol.41, no.7, pp.134,141, July 2003

The advent of software radios has brought a paradigm shift to radio design. A multimode handset with dynamic reconfigurability has the promise of integrated services and global roaming capabilities. However, most of the work to date has been focused on software radio base stations, which do not have as tight constraints on area and power as handsets. Base station software radio technology progressed dramatically with advances in system design, adaptive modulation and coding techniques, reconfigurable hardware, A/D converters, RF design, and rapid prototyping systems, and has helped bring software radio handsets a step closer to reality. However, supporting multimode radios on a small handset still remains a design challenge. A configurable computing machine, which is an optimized FPGA with application-specific capabilities, show promise for software radio handsets in optimizing hardware implementations for heterogeneous systems. In this article contemporary CCM architectures that allow dynamic hardware reconfiguration with maximum flexibility are reviewed and assessed. This is followed by design recommendations for CCM architectures for use in software radio handsets.

Minimum selection GSC and adaptive low-power rake combining scheme

Jeffrey H. Reed, Suk Won Kim; Ha, D.S.;
Conference PaperCircuits and Systems, 2003. ISCAS '03. Proceedings of the 2003 International Symposium on , vol.4, no., pp.IV-357,IV-360 vol.4, 25-28 May 2003

In this paper, we investigate a new generalized selection combining (GSC) technique and an adaptive low-power rake combining scheme to save the power consumption of mobile rake receivers for wideband CDMA systems. The new GSC technique called minimum selection GSC (MS-GSC) selects a minimum number of rake fingers as long as the combined SNR is larger than a given threshold. The proposed rake combining scheme adaptively adjusts the threshold value to maintain the desired BER, in which a GSC dynamically selects rake fingers to meet the given threshold condition. The proposed MS-GSC shows a low standard deviation in bit error statistics and advantages practical implementation. The proposed adaptive scheme works well with existing GSC schemes as well as the proposed MS-GSC. The proposed scheme reduced the power consumption of a mobile rake receiver up to 67.8% by turning off unselected rake fingers.

Nonlinear tapped delay line digital predistorter for power amplifiers with memory

Jeffrey H. Reed, Nizamuddin, M.A.; Balister, P.J.; Tranter, W.H.; ;
Conference Paper Wireless Communications and Networking, 2003. WCNC 2003. 2003 IEEE , vol.1, no., pp.607,611 vol.1, 20-20 March 2003

Current bandwidth-efficient modulated signals are significantly distorted during nonlinear amplification. Memoryless digital predistortion is a cost-effective method to compensate for such distortion caused by a nonlinear amplifier. However, significant frequency-dependent effects in high power, wideband nonlinear amplifiers operating on signals such as multicarrier WCDMA reduce the effectiveness of memoryless predistortion and thus cancellation of memory effects is necessary. In this paper, we have presented a nonlinear tapped delay line (NTDL) predistorter structure with memory compensation as well as indirect learning capability, and demonstrated its performance for a 2-carrier WCDMA signal.

Bit error rate estimation using probability density function estimators

Jeffrey H. Reed, Laster, J.D.; Tranter, W.H.,
Conference PaperVehicular Technology, IEEE Transactions on , vol.52, no.1, pp.260,267, Jan 2003

The concept of real-time bit error rate (BER) estimation based on probability density function (PDF) estimators of the decision statistic is discussed. Communications systems need techniques to approximate real-time BER estimation without resorting to brute-force error counting methods. Due to the dynamic nature of the wireless channel, a priori (deductive) estimation techniques (e.g., where knowledge of signal impairments is assumed before demodulation) are often unreliable. A posteriori (inductive) estimation techniques (e.g., where knowledge of signal impairments is acquired after the signal is demodulated) are preferable because they assume no prior knowledge of the channel. Two a posteriori techniques are described that yield reliable BER estimates over small observation intervals: (1) the Gram-Charlier series approximation for PDFs and (2) Parzen's PDF estimator. Robust estimators of location and scale are also employed to improve the performance of Gram-Charlier estimation. The performance of BER estimation based on the PDF estimators is validated by simulations. A 1-bit differential demodulator (DD1) is used to demodulate a Gaussian minimum shift keying signal, and Gram-Charlier-based and Parzen (1962) based BER estimations are compared to measured DD1 results. Comparisons are made for BER estimation versus measured BER in additive white Gaussian noise (AWGN) and cochannel interference (CCI) channels and in urban multipath with AWGN and CCI.

THE ROLE OF GAME THEORY IN THE ANALYSIS OF SOFTWARE RADIO
NETWORKS

Jeffrey H. Reed, James Neel, R. Gilles
Conference Paper SDR Forum Technical Conference November, 2002

The development of software radio technology facilitates the adoption of the adaptive modulation schemes that have recently been proposed in literature which promise significant performance improvements over a link. However, alterations to one link's waveform will alter the interference seen by the other links in the network, which will in turn affect their adaptation schemes. The dynamic and interdependent nature of this network makes analysis and management of such a network difficult to perform.

Space-time block codes for eight transmit antennas

Jeffrey H. Reed, Ahmed, Y.; Buehrer, R.M.;
Conference PaperSignals, Systems and Computers, 2002. Conference Record of the Thirty-Sixth Asilomar Conference on , vol.2, no., pp.1359,1363 vol.2, 3-6 Nov. 2002

In this paper we present full-rate complex nonorthogonal codes for eight transmit antennas and compare their performance to orthogonal designs that provide the same spectral efficiency. The proposed codes have a structure that allows simplified maximum likelihood decoding at the receiver. The decoding scheme is further simplified for rectangular constellations where the real and imaginary parts can be decoded separately. Finally it is shown that the performance of the nonorthogonal codes can be improved significantly by employing a constellation rotation scheme (Sharma et al. (2002)) and this improvement can be attributed to the change in the rank distribution of the code.

A geometric air-to-ground radio channel model

Jeffrey H. Reed, Newhall, W.G.;
Conference Paper MILCOM 2002. Proceedings , vol.1, no., pp.632,636 vol.1, 7-10 Oct. 2002

Presents a geometric channel model for simulation and analysis of air-to-ground radio communications. The model represents an airborne station communicating with a ground station in a cluttered environment (e.g., ground-based, mobile transceiver in an urban or village region). The model call be used to produce multipath component delay, strength, and direction of arrival (DOA) information, and it is therefore well suited for simulating vector channels for smart antenna arrays and antenna diversity systems. This air-to-ground channel model is based on a three-dimensional ellipsoidal geometry and uses principles similar to those used by the geometrically based single-bounce elliptical (GBSBE) and geometrically based single-bounce circular (GBSBC) models. However, instead of assuming two ground-based stations, this geometric air-to,ground model uses altitude and range information. The result is the ability to simulate multipath air-to-ground channels with a geometry more appropriate for the physical configuration of the stations.

A geometric air-to-ground radio channel model

Jeffrey H. Reed, Newhall, W.G.;
Conference Paper MILCOM 2002. Proceedings , vol.1, no., pp.632,636 vol.1, 7-10 Oct. 2002

Presents a geometric channel model for simulation and analysis of air-to-ground radio communications. The model represents an airborne station communicating with a ground station in a cluttered environment (e.g., ground-based, mobile transceiver in an urban or village region). The model call be used to produce multipath component delay, strength, and direction of arrival (DOA) information, and it is therefore well suited for simulating vector channels for smart antenna arrays and antenna diversity systems. This air-to-ground channel model is based on a three-dimensional ellipsoidal geometry and uses principles similar to those used by the geometrically based single-bounce elliptical (GBSBE) and geometrically based single-bounce circular (GBSBC) models. However, instead of assuming two ground-based stations, this geometric air-to,ground model uses altitude and range information. The result is the ability to simulate multipath air-to-ground channels with a geometry more appropriate for the physical configuration of the stations.

Game theoretic analysis of a network of cognitive radios

Jeffrey H. Reed, Neel, J.; Buehrer, R.M.; Gilles, Robert P.,
Conference Paper Circuits and Systems, 2002. MWSCAS-2002. The 2002 45th Midwest Symposium on , vol.3, no., pp.III-409,III-412 vol.3, 4-7 Aug. 2002

Cognitive radio is an enhancement on traditional software radio design where observations of the operating environment are combined with knowledge of the radio's available hardware and software capabilities to form decisions as to how to modify the radio's behavior to produce a desired level of performance. This paper addresses how the insertion of cognitive radio technology into a network will impact performance and demonstrates how techniques from game theory can be used to analyze the network as a first step of shaping the decisions of the radios to achieve optimal network performance.

Background interference measurements at 2.45 GHz in a hospital environment

Jeffrey H. Reed, Seshagiri Krishnamoorthy, Chris R Anderson, Srikathyayani Srikanteswara, Max Robert,
Conference Paper Virginia Tech and University of Wake Forest Bio-Medical Symposium, 2002

In recent years, advancements in the field of wireless communication have led to more innovative consumer products at reduced cost. Over the next 2 to 5 years, short-range wireless devices such as Bluetooth and Wireless Local Area Networks ( WLANS) are expected to become widespread throughout hospital enviroments for various applications. Consequently the medical community views wireless applications as ineludible and necessary. However, currently there exist regulations on the use of wireless devices in hospitals, and with the ever increasing wireless psersonal applications, there will be more unconcious wireless devices entering and operationg in hospitals. It is feared that these wireless devices may cause electromagnetic interference that could alter the operation of medical equipment and negatively impact patient care. Additionally, unintentional electromagnetic radiation from medical equipment may have a detrimental effect on the quality of service (Q0S) of these short-range wireless devices.

On the throughput of Bluetooth data transmissions

Jeffrey H. Reed,Valenti, M.C.; Robert, M.
Conference Paper Wireless Communications and Networking Conference, 2002. WCNC2002. 2002 IEEE , vol.1, no., pp.119,123 vol.1, 17-21 Mar 2002

Analytical expressions for the throughput (in kbit/s) as a function of channel symbol signal-to-noise ratio (Es/N0) are derived for the six Bluetooth ACL packets that use automatic repeat request (ARQ). The analysis is exact under the assumptions that the outer CRC code provides perfect error detection and that the channel remains stationary for the duration of each packet. Using an expression for noncoherent correlated (h<0.5) full response FSK signals, numerical results are provided for AWGN and quasi-static Rayleigh fading channels. These curves are an appropriate benchmark against which practical demodulators and custom error control techniques may be compared.

Geometrical-based statistical macrocell channel model for mobile environments

Jeffrey H. Reed, Petrus, P.; Rappaport, T.S.,
Conference PaperCommunications, IEEE Transactions on , vol.50, no.3, pp.495,502, Mar 2002

We develop a statistical geometric propagation model for a macrocell mobile environment that provides the statistics of angle-of-arrival (AOA) of the multipath components, which are required to test adaptive array algorithms for cellular applications. This channel model assumes that each multipath component of the propagating signal undergoes only one bounce traveling from the transmitter to the receiver and that scattering objects are located uniformly within a circle around the mobile. This geometrically based single bounce macrocell (GBSBM) channel model provides three important parameters that characterize a channel: the power of the multipath components, the time-of-arrival (TOA) of the components, and the AOA of the components. Using the GBSBM model, we analyze the effect of directional antennas at the base station on the fading envelopes. The level crossing rate of the fading envelope is reduced and the envelope correlation increases significantly if a directional antenna is employed at the base station.

3G — Around the world and back again

Jeffrey H. Reed, Raqibul Mostafa, Fakhrul Alam, Kyung Kyoon Bae, WH Tranter, BD Woerner
Conference Paper Communications, IEEE Transactions on , vol.50, no.3, pp.495,502, Mar 2002

The emergence of the 3G standard is a mandate to provide higher data rate and better spectrum efficiency. This standard is designed to overcome many of the key limitations imposed by existing 2G wireless systems. Web browsing, Internet-based applications and streaming audio/video represent some examples of present-day data communications that require high data rates. Seamless global roaming is also an attractive feature of 3G systems. In the process of providing enhanced voice/data services over wireless media, several competing 3G standards have been proposed and are vying for the honor of becoming the global 3G standard.

Statistical back-off method for minimizing interference among distinct network technologies

Jeffrey H. Reed, Robert, M.; DaSilva, L.A.;
Conference PaperVehicular Technology Conference, 2002. Proceedings. VTC 2002-Fall. 2002 IEEE 56th , vol.3, no., pp.1725,1729 vol.3, 2002

With the advent of new networking technology operating over license-free bands such as Bluetooth, IEEE 802.11, and HomeRF, network co-existence has become an issue of great concern. This paper presents a method to reduce the interference issue by applying a statistical backoff algorithm to some of the devices in the network. This algorithm modifies the traffic transmitted by devices such that they transmit only when the probability of collision with other systems is lowest. An analytical description of the interference conditions of the channel can then be applied to the device queue to minimize the probability of collision. Simulation results show that, depending on the traffic model selected, this algorithm can provide increases in power efficiency while creating decreases in throughput that are dependent on the selected traffic model.

Overloaded array processing with MMSE-SIC

Jeffrey H. Reed, Hicks, J.E.; Tsai, J.; Tranter, W.H.; Woerner, B.D.
Conference PaperVehicular Technology Conference, 2002. VTC Spring 2002. IEEE 55th , vol.2, no., pp.542,546 vol.2, 2002
doi: 10.1109/VTC.2002.1002539

This paper considers the application of minimum mean squared error linear space-time processing in tandem with successive interference cancellation (MMSE-SIC) to the extraction of symbol-asynchronous π/4-DQPSK signals with RRCOS pulse shaping (35%-75% rolloff) in overloaded environments. The performance is analyzed through simulation in terms of the symbol error rate ranked by cancellation order. The effect of signal excess-bandwidth, adjacent channel interference, the number of users, SNR, and array type are considered. The channel statistics of all users are assumed known.

Channel Frame Error Rate for Bluetooth in the Presence of Microwave Ovens

Jeffrey H. Reed, Seshagiri Krishnamoorthy, Max Robert, Srikathyayani Srikanteswara, Matthew C. Valenti, Chris R. Anderson
Conference Paper Vehicular Technology Conference, 2002. VTC Spring 2002. IEEE 55th , vol.2, no., pp.542,546 vol.2, 2002
doi: 10.1109/VTC.2002.1002539

In this paper, radiation from microwave ovens is measured using PRISM, a custom-built device designed to measure transmissions in the ISM band. The measured signals, treated as a rising noise floor, are then applied to a semianalytic simulation to determine the probability of frame error rate (FER) per channel for six Bluetooth packet types.

Demonstration of real-time wideband transmit diversity at the handset in an indoor wireless channel

Jeffrey H. Reed, Mostafa, R.; Dietze, K.; Palat, R.C.; Stutzman, W.L.
Conference PaperVehicular Technology Conference, 2001. VTC 2001 Fall. IEEE VTS 54th , vol.4, no., pp.2072,2076 vol.4, 2001

The next generation CDMA standard, wideband CDMA (W-CDMA), has provision for many performance enhancement options to support high data-rate services. Transmit diversity has been proposed as one mechanism for performance enhancement. This paper presents a real-time implementation of a wideband transmit diversity system. The implementation was carried out to demonstrate transmit diversity in an indoor wireless channel at the handset with a two-element antenna array at 2.05 GHz for a bandwidth of 5 MHz. The diversity algorithm is a closed loop technique and is based on scanning the phase of signal on one antenna relative to the other. Single antenna measurements were also performed to serve as a baseline measure. Measurements were carried out both in line-of-sight (LOS) and in non-LOS (NLOS) environments. The diversity gains when assessed using a cumulative distribution function (CDF), showed gains of 2 dB and 7 dB respectively compared to individual antenna element for the LOS environment (at 1% CDF level).

Receiver structures for W-CDMA space-time processing

Jeffrey H. Reed, Vasavada, Y.M.; JeongHo Kim;
Conference Paper Vehicular Technology Conference, 2001. VTC 2001 Fall. IEEE VTS 54th , vol.4, no., pp.1965,1969 vol.4, 2001
doi: 10.1109/VTC.2001.957087

We reformulate several different models of antenna array enabled W-CDMA receivers operating in a frequency selective multipath fading channel. We study the problem of full exploitation of both spatial diversity offered by the antenna array and temporal diversity offered by the RAKE while suppressing the interference

Role of signal envelope distribution in predicting the performance of a multicarrier communication system

Jeffrey H. Reed, Balister, P.; Nizamuddin, M.; Robert, M.; Tranter,
Conference Paper Radio and Wireless Conference, 2001. RAWCON 2001. IEEE , vol., no., pp.245,248, 2001

The peak-to-average power ratio of a signal is often used to determine the output power backoff needed to prevent spectral regrowth due the effects of nonlinear power amplifiers. It has been suggested that a better measure of the impact of a nonlinear amplifier on the transmitted signal is the envelope power distribution function. This paper presents simulation results for a multicarrier communication system showing how the peak-to-average power ratio and the envelope power distribution function change as the number of carriers increases, these results show that the envelope power distribution function is a better figure of merit than the peak-to-average power ratio for determining the impact of a nonlinear power amplifier on a communication system's BER.

Spatio-temporal searcher structure for 3G W-CDMA smart antenna systems

Jeffrey H. Reed, JeongHo Kim; Vasavada, Y.M.;
Conference PaperVehicular Technology Conference, 2001. VTC 2001 Fall. IEEE VTS 54th , vol.3, no., pp.1635,1639 vol.3, 2001

Smart antenna systems have been considered for base station (BS) and mobile station (MS) to improve spectral efficiency and link quality. The newly emerging 3rd generation mobile (W-CDMA and cdma2000) systems are required to support high bit rate services. This type of high bit rate traffic inevitably consumes a significant amount of capacity and causes considerable interference to low data rate users. Under these circumstances, the smart antenna system is a good candidate to mitigate this interference and keep link quality at adequate levels. One of the crucial components, which can be very complex, is the searcher whose functionality is to continuously search for new multipath signals for combining. A spatio-temporal searcher structure is proposed to enhance the detection capability of the multipath traffic channel searcher. This structure basically employs a spatio-temporal signal structure to search for a new signal. The detection and false alarm probabilities of the new and conventional schemes are calculated and numerical examples of mean acquisition time are given

Performance comparison between pilot symbol assisted and blind beamformer-RAKE receivers at the reverse link of third generation CDMA system

Jeffrey H. Reed, Alam, F.; Zahid, K.A.; Woerner, B.D.;
Conference Paper Vehicular Technology Conference, 2001. VTC 2001 Fall. IEEE VTS 54th , vol.1, no., pp.353,357 vol.1, 2001

A beamformer-RAKE receiver allows processing of the signal in both the spatial and temporal domain by combining an adaptive antenna array with a RAKE. This can significantly improve the system performance along the reverse link of a wideband code division multiple access (WCDMA) system by providing multiple access interference (MAI) suppression and multipath diversity. We compare the performance of two different beamformer-RAKE receivers that employ the minimum mean square error (MUSE) and the maximum signal to interference and noise ratio (MSINR) criteria to form the beams in the spatial domain. The pilot symbol assisted (PSA) technique and the blind code gated algorithm (CGA) were selected to exploit the aforementioned criteria.

Soft radio implementations for 3G and future high data rate systems

Jeffrey H. Reed, Srikanteswara, S.; Neel, J.; Athanas, P.,
Conference PaperGlobal Telecommunications Conference, 2001. GLOBECOM '01. IEEE , vol.6, no., pp.3370,3374 vol.6, 2001

Recent advances in reconfigurable computing have now made it possible to implement the concept of hardware paging which has the potential to greatly advance the design of soft radios. While many soft/software radio architectures have been suggested and implemented, there remains a lack of a formal design methodology that can be used to design and implement these radios on reconfigurable platforms that exploit the latest inventions. A unified architecture, called the layered radio architecture, for design of soft radios on a reconfigurable platform was presented previously by the authors (see IEEE Communications Magazine vol.38, no.2, p.140-7, February 2000). The layered architecture makes it possible to incorporate all of the features of a software radio while keeping complexity issues at a minimal level. The layered architecture also defines the methodology for incorporating changes and updates into the system. In this paper, we implement a RAKE receiver and channel estimation for W-CDMA downlink to show how the architecture combined with the use of the Custom Computing Machine Stallion, can handle 3G and future high data rate systems

Virginia Tech Space-Time Advanced Radio (VT-STAR)

Jeffrey H. Reed, Gozali, R.; Mostafa, R.; Palat, R.C.; Marikar, S.; Robert, P.M.; Newhall, W.G.; Beaudette, C.; Tsiakkouris, S.A.; Anderson, C.; Neel, J.; Woerner, B.D.;
Conference Paper Radio and Wireless Conference, 2001. RAWCON 2001. IEEE , vol., no., pp.227,231, 2001

With the integration of the Internet and multimedia applications in next generation wireless communications, the demand for reliable high data rate services is rapidly growing. Traditional wireless communications systems use a single input single output (SISO) channel, meaning one antenna at each side of the link. Information theory research has shown an enormous potential growth in the capacity of wireless systems by using multiple element array (MEA) technology at both ends of the link. Space-time coding exploits the spatialtemporal diversity provided by the multiple input multiple output (MIMO) channel, significantly increasing both the system capacity and the reliability of the wireless link. The Virginia Tech Space-Time Advanced Radio (VT-STAR) system presents a visual demonstration of the capabilities of space-time coding techniques. The VT-STAR system has integrated an MPEG-2 video stream to show a representation of the effect of the wireless channel on a video transmission in real-time. Core algorithms are implemented on Texas Instruments TMS320C67 Evaluation Modules (EVM). Data conversion between the digital and analog domains is performed by TI THS5661 EVM and TI THS1206 EVM for the transmitter and receiver, respectively. The radio frequency subsystem is composed of multi-channel transmitter and receiver chains implemented in hardware. The capabilities of the MIMO channel are demonstrated in a non-line of sight (NLOS) indoor environment. Real-time monitoring of physical layer parameters, such as the bit error rate and diversity advantage, as well as a video display are presented on an attached personal computer

Statistics of blind spatial signature estimators

Jeffrey H. Reed, Biedka, T.E.; Tranter, W.H.,
Conference PaperSignals, Systems and Computers, 2000. Conference Record of the Thirty-Fourth Asilomar Conference on , vol.2, no., pp.847,850 vol.2, Oct. 29 2000-Nov. 1 2000

A spatial signature is used to model a communication signal that is received by an array of antennas in a multipath environment. If the transmitted waveform is not known, a blind estimate of the unknown spatial signature may be obtained by cross-correlating an estimate of the transmitted waveform with the received data. This paper presents the mean and variance of a blind spatial signature estimator that is obtained by either a constant modulus mapping or by mapping onto a known finite alphabet. These results are compared to those for an estimator that exploits a known waveform.

Code gated algorithm: a blind adaptive antenna array beamforming scheme for the wideband CDMA system

Jeffrey H. Reed, Vasavada, Y.M.; Biedka, T.E.;
Conference PaperSignals, Systems and Computers, 2000. Conference Record of the Thirty-Fourth Asilomar Conference on , vol.2, no., pp.1397,1402 vol.2, Oct. 29 2000-Nov. 1 2000

This paper describes a blind beamforming algorithm based on maximum SINR criterion applied to the reverse link of the W-CDMA system. The maximum SINR weight vector is derived by exploiting the separation of the frequency band of the desired signal from the frequency band of the interference and noise after a despreading operation on the received CDMA signal. Thus, the algorithm applies the concept of the frequency gating to the CDMA beamforming. We call this algorithm a code gated algorithm or CGA to distinguish the use of CDMA spreading code in separating the desired signal from the interference and noise.

Space, polarization, and angle diversity for cellular base stations operating in urban environments

Jeffrey H. Reed, Byung-Ki Kim; Stutzman, W.L.; Sweeney, D.G.;
Conference Paper Antennas and Propagation Society International Symposium, 2000. IEEE , vol.2, no., pp.940,943 vol.2, 16-21 July 2000

Cellular telephone systems offer high reliability in favorable environments such as open rural areas. However, in urban areas and in rough terrain mobile and personal terminals experience multipath fading. Diversity techniques are used at the base station to overcome multipath fading. Although space diversity is the most common form of antenna diversity, it is the least attractive because it requires a second antenna widely separated from the first, as well as associated cable runs and installation costs. Interest has focused on polarization diversity that uses a single dual polarized antenna in place of two space diversity antennas. Angle diversity is also effective, but is not commonly employed. No direct, simultaneous comparisons of space, polarization, and angle diversity have been reported. Virginia Tech, sponsored by Metawave, is performing measurements of the three diversities under identical conditions.

Recent results from smart antenna experiments-base station and handheld terminals

Jeffrey H. Reed,Stutzman, W.L.; Dietrich, C.B., Jr.; Kim, B.-K.; Sweeney, D.G.,
Conference Paper Radio and Wireless Conference, 2000. RAWCON 2000. 2000 IEEE , vol., no., pp.139,142, 2000

Virginia Tech is involved in both smart base station and smart terminal antenna research for wireless applications. Smart features vary from simple diversity combining to adaptive algorithm implementations. Measurement campaigns are described and results are presented.

A code tracking technique for direct sequence spread spectrum using adaptive filtering

Jeffrey H. Reed, Hosemann, M.; Srikanteswara, S.;
Conference Paper Radio and Wireless Conference, 2000. RAWCON 2000. 2000 IEEE , vol., no., pp.25,28, 2000

Synchronizing a direct sequence spread spectrum (DS-SS) system involves determining code timing in a two step procedure, acquisition of symbol timing and tracking the code timing. This paper deals with tracking issues and assumes successful initial acquisition. Tracking is necessary because code timing is not constant, due to varying channel delays and clock imperfections at the transmitter and receiver. Most tracking schemes employ matched filtering based delay-locked-loops (DLLs). However, matched filter based DLLs are susceptible to multiple access interference (MAI). For the specific needs of an adaptive demodulation also know as a linear single-user multiple access (LSUMA) a new tracking scheme is introduced and its performance is demonstrated for handling multiple access interference. The new tracking scheme does not require the use of a pilot channel or training .

Design and implementation of a completely reconfigurable soft radio

Jeffrey H. Reed, Biedka, T.E.; Tranter, W.H.,
Conference Paper Array and Multichannel Signal Processing Workshop. 2000. Proceedings of the 2000 IEEE , vol., no., pp.68,72, 2000

New analytic results on the convergence of a blind decision directed adaptive algorithm in a beamforming application are presented. The data received at multiple antennas is assumed to consist of a desired PSK signal plus additive Gaussian noise and interference. The mean improvement in output SINR obtained with one iteration of the adaptive algorithm is predicted. This is used to estimate the number of iterations required for convergence. Results are presented for BPSK and QPSK signals. The performance of the decision directed algorithm and a constant modulus algorithm is also compared.

Mean convergence rate of a decision directed adaptive beamformer with Gaussian interference

Jeffrey H. Reed, Srikanteswara, S.; Hosemann, M.; Reed, J.H.; Athanas, P.M.,
Conference Paper Radio and Wireless Conference, 2000. RAWCON 2000. 2000 IEEE , vol., no., pp.7,11, 2000

The advances in reconfigurable computing have now made it possible to implement the concept of hardware paging, which has the potential to greatly advance the design of soft radios. While many soft/software radio architectures have been suggested and implemented there remains a lack of a formal design methodology that can be used to design and implement these radios on reconfigurable platforms that exploit the latest inventions. This paper presents a unified architecture, called the layered radio architecture, for design of soft radios on a reconfigurable platform. Using the assumptions of the availability of run-time reconfigurable hardware and the use of stream-based computing, the layered radio architecture defines a soft radio architecture that is scalable in hardware and software, flexible, and capable of supporting multi-mode radios along with over-the-air updates and software validation.

Overloaded array processing in wireless airborne communication systems

Jeffrey H. Reed, Bayram, S.; Hicks, J.; Boyle, R.J.;
Conference Paper MILCOM 2000. 21st Century Military Communications Conference Proceedings , vol.1, no., pp.24,29 vol.1, 2000

In mobile cellular communications, one of the major challenges that a system designer and a DSP engineer are faced with is severe co-channel interference (CCI). This is especially true for wireless networks that employ airborne repeaters, such as the “base station in the sky” repeater proposed by SkyStation International, Incorporated. The receiver faces the challenge of demodulating the signal of interest (SOI) in the presence of excessive amounts of CCI from a large number of sources. This results in the overloaded environment where the number of near-equal power co-channel interferers, d, exceeds the number of antenna array elements, m. In this paper we first analyze a generic overloaded interference environment experienced by a wireless airborne communication receiver flying at altitudes on the order of miles above the Earth surface. A two-ray propagation model analysis shows that the antenna array mounted on an airborne receiver has to be able to recover the SOI out of hundreds of co-channel interfering signals. Due to the limitations of the array size on the surface of the aircraft, linear signal processing techniques such as space-time beamforming are not be able to perform well in such scenarios. For this reason, we show that signal extraction in overloaded environments can be achieved by employing a non-linear maximum-likelihood (ML) detector. This technique, called least squares with enumeration (LSE), is a ML joint detection approach that provides an optimum solution for overloaded antenna array scenarios in the presence of synchronous co-channel users in an AWGN channel

Joint maximum likelihood approach in overloaded array processing

Jeffrey H. Reed, Bayram, S.; Hicks, J.; Boyle, R.J.;
Conference PaperVehicular Technology Conference, 2000. IEEE-VTS Fall VTC 2000. 52nd , vol.1, no., pp.394,400 vol.1, 2000

We demonstrate that, signal extraction in overloaded environments is achieved by employing a nonlinear maximum-likelihood detector. We define the overloaded interference scenario as one where the number of near equal-power co-channel interferers exceeds the number of antenna array elements. The iterative least squares with enumeration (ILSE) technique is a maximum likelihood joint detector that provides an optimum solution for the overloaded antenna array scenarios in the presence of synchronous cochannel users in an AWGN channel. A linearized version of ILSE, called iterative least-squares with projection (ILSP) is shown to fail in overloaded environments due to an implicit beamformer assumption. ILSE is shown to extract signals with very small angular separations in highly overloaded scenarios at reasonable SNRs. We also show that when the channel is a priori unknown, ILSE can still demodulate more users than elements by incorporating short training sequences for channel estimation as well as employing a completely blind channel estimation technique

Fuzzy logic based adaptive handoff algorithms for microcellular systems

Jeffrey H. Reed, Tripathi, N.D.; Vanlandingham, H.F.,
Conference Paper Vehicular Technology Conference, 1999 IEEE 49th , vol.2, no., pp.1419,1424 vol.2, Jul 1999

Microcells increase system capacity but make resource management difficult. A fixed parameter handoff algorithm cannot perform uniformly well in various handoff scenarios encountered by a mobile station in a microcellular environment. Adaptive handoff algorithms based on fuzzy logic are proposed. It is shown that the proposed algorithms provide high performance in generic handoff scenarios in a microcellular system.

MPEG video quality prediction in a wireless system

Jeffrey H. Reed, Robert, P.M.; Darwish, A.M.
Conference Paper Vehicular Technology Conference, 1999 IEEE 49th , vol.2, no., pp.1490,1495 vol.2, Jul 1999

Wireless systems under design today promise to deliver high-bandwidth applications to mobile users in dynamic channel environments. The protocol used to control the network in a wireless system may not necessarily be able to control bit errors in its payload. Therefore, it is important to assess the impact of bit errors in a delivered data stream. This paper concentrates on the effects of bit errors on an MPEG-2 digital video sequence. A basic decoupling between bit error rate (BER) and peak signal-to-noise ratio (PSNR) was shown on previously published papers, signaling a loss of confidence on BER as a basic metric of digital system performance. This paper introduces a statistical approach to predicting video quality based solely on physical layer parameters. The mean error event length, λdistance, is a metric derived from the physical layer that can be used to predict the expected video quality across systems with different channel coding algorithms. This metric proved to be uniformly consistent in predicting video quality for sequences corrupted by additive white Gaussian noise and protected by convolutional, Reed-Solomon (RS), and concatenated (convolutional and RS) codes.

MPEG video quality prediction in a wireless system

Jeffrey H. Reed, Robert, P.M.; Darwish, A.M.
Conference Paper Vehicular Technology Conference, 1999 IEEE 49th , vol.2, no., pp.1490,1495 vol.2, Jul 1999

Wireless systems under design today promise to deliver high-bandwidth applications to mobile users in dynamic channel environments. The protocol used to control the network in a wireless system may not necessarily be able to control bit errors in its payload. Therefore, it is important to assess the impact of bit errors in a delivered data stream. This paper concentrates on the effects of bit errors on an MPEG-2 digital video sequence. A basic decoupling between bit error rate (BER) and peak signal-to-noise ratio (PSNR) was shown on previously published papers, signaling a loss of confidence on BER as a basic metric of digital system performance. This paper introduces a statistical approach to predicting video quality based solely on physical layer parameters. The mean error event length, λdistance, is a metric derived from the physical layer that can be used to predict the expected video quality across systems with different channel coding algorithms. This metric proved to be uniformly consistent in predicting video quality for sequences corrupted by additive white Gaussian noise and protected by convolutional, Reed-Solomon (RS), and concatenated (convolutional and RS) codes.

Antenna array hardware amplitude and phase compensation using baseband antenna array outputs

Jeffrey H. Reed, Ertel, R.B.; Zhong Hu;
Conference PaperVehicular Technology Conference, 1999 IEEE 49th , vol.3, no., pp.1759,1763 vol.3, Jul 1999

Most direction finding algorithms require knowledge of the array manifold. The array manifold may be estimated using expensive and time consuming array calibration procedures. An alternative is to bore-sight the array and then assume that the array manifold is ideal. Bore-sighting is often achieved by injecting a common signal into the RF front-end using a signal generator followed by a signal splitter. Unknown phase shifts through the splitter will cause errors in the bore-sighting process. In this paper we describe a simple procedure for estimating and then compensating for the non-ideal phase shifts in the splitter using complex baseband measurements at the array output.

Adaptive handoff algorithms for cellular overlay systems using fuzzy logic

Jeffrey H. Reed, Tripathi, N.D.; Vanlandingham, H.F.,
Conference Paper Vehicular Technology Conference, 1999 IEEE 49th , vol.2, no., pp.1413,1418 vol.2, Jul 1999

An overlay system is a hierarchical architecture that uses large macrocells to overlay clusters of small microcells. Resource management in the overlay system is much more complex than in pure macrocell and microcell systems. A fixed parameter handoff algorithm cannot perform well in a complex and dynamic overlay environment. This paper proposes an adaptive overlay handoff algorithm that allows a systematic tradeoff among the system design parameters and improves the overall system performance

Fast bit error generation for the simulation of MPEG-2 transmissions in wireless systems

Jeffrey H. Reed, Tripathi, N.D.; Vanlandingham, H.F.,
Conference Paper Wireless Communications and Networking Conference, 1999. WCNC. 1999 IEEE , vol., no., pp.324,328 vol.1, 1999

This paper presents alternate methods to generate bit errors that simulate the effect of a convolutional code on an MPEG-2 sequence. Given the complexity of Viterbi decoders, a fast way to generate bit errors that closely resembles the performance of a convolutional code/Viterbi decoder is desirable in order to minimize the execution time of Monte Carlo simulations. Three methods of generating the bit error sequences are presented in this paper. A simulation of a Viterbi decoder is used as a reference against which the proposed methods are compared. A two-random-variable method is presented that closely matches the performance of the simulation of the Viterbi decoder in both BER and PSNR. A simplification of the two-random-variable method is also presented, where only a single random variable is used, and a deterministic form of the behavior of the convolutional code/Viterbi decoder is used. This single-random-variable method yields results that are similar to the two-random-variable method, with comparable values of BER and PSNR. The statistics of the bit error distribution are sacrificed in exchange for a simplified model and less knowledge of the behavior of the Viterbi decoder. The third method proposed is a simplification of the single-random-variable method, where a single bit error is used to model whole bit error bursts. This method yields inaccurate BER estimates but also PSNR values that are biased but close to the behavior of the convolutional code.

Pattern classification based handoff using fuzzy logic and neural nets

Jeffrey H. Reed, Tripathi, N.D.;Van Landingham, H.F.,
Conference PaperCommunications, 1998. ICC 98. Conference Record. 1998 IEEE International Conference on , vol.3, no., pp.1733,1737 vol.3, 7-11 Jun 1998

Conventional handoff algorithms are susceptible to varying propagation environments, traffic intensities, and user speeds due to the lack of parameter adaptation. This paper proposes a new class of adaptive handoff algorithms that views the handoff problem as a pattern classification problem. Adaptive direction biasing is proposed to reduce the processing load and improve the cell membership properties. The paper shows that the desired balance among the system characteristics can be achieved by making appropriate design tradeoffs in a pattern classification based handoff framework.

An adaptive direction biased fuzzy handoff algorithm with unified handoff candidate selection criterion

Jeffrey H. Reed, Tripathi, N.D.; Vanlandingham, H.F.,
Conference Paper Vehicular Technology Conference, 1998. VTC 98. 48th IEEE , vol.1, no., pp.127,131 vol.1, 18-21 May 1998

An adaptive handoff algorithm can give high performance in dynamic and complex cellular systems. This paper proposes a new fuzzy logic based algorithm with a unified handoff candidate selection criterion and adaptive direction biasing. Known sensitivities of handoff parameters are used to create a fuzzy logic system, which serves as a mechanism to adapt handoff parameters. The unified handoff candidate selection criterion allows simultaneous consideration of several handoff criteria to select the best handoff candidate under given constraints. The proposed handoff algorithm also provides enhanced direction biasing by adapting the direction biasing parameters.

Impact of path-loss on the Doppler spectrum for the geometrically based single bounce vector channel models

Jeffrey H. Reed, Ertel, R.B.;
Conference PaperVehicular Technology Conference, 1998. VTC 98. 48th IEEE , vol.1, no., pp.586,590 vol.1, 18-21 May 1998

It has been shown that the Doppler spectrum can be related to the distribution of power over the angle of arrival at the mobile. A slightly more general expression is found which shows that the Doppler spectrum may be expressed as the product of the Doppler frequency probability density function and the conditional expected value of the power given the Doppler frequency (i.e. the average received power given the Doppler frequency). The derived relationship is used to find the Doppler spectrum for the elliptical geometrically based vector channel model, without ignoring the dependence of the received signal power on the angle of arrival which results from the distance dependent path-loss.

Blind CDMA interference rejection in multipath channels

Jeffrey H. Reed, Mangalvedhe, N.R.;
Conference PaperVehicular Technology Conference, 1997, IEEE 47th , vol.1, no., pp.21,25 vol.1, 4-7 May 1997

The performance of conventional code division multiple access (CDMA) receivers is limited by multiple access interference (MAI) and near-far effects. The severity of the problem is increased in multipath channels. A RAKE receiver exploits multipath diversity but is unable to suppress interference. Adaptive receivers can exploit multipath and suppress MAI, however this approach requires a training sequence. This paper presents a new blind algorithm that is capable of optimally combining multipath while canceling MAI

Cell average carrier-to-interference coverage improvement by using DSP interference rejection techniques

Jeffrey H. Reed, Rong He;
Conference Paper Vehicular Technology Conference, 1997, IEEE 47th , vol.2, no., pp.1079,1083 vol.2, 4-7 May 1997
doi: 10.1109/VETEC.1997.600496

The performance of a cellular phone system can be evaluated from several perspectives, one of which is the capacity. The capacity of a cellular system can be described by the cell carrier-to-interference ratio coverage (or the percentage of a cell area in which the carrier-to-interference ratio (CIR) is greater than a specific threshold). A theoretical form of the cell carrier-to-interference ratio coverage is derived for both the forward and reverse links. The cell average CIR coverage is also compared to the cell worst case CIR coverage, where the mobile is at the edge of its serving cell but is at the location closest to its interfering cell. The analysis is used to show how the coverage and the capacity can be improved by incorporating digital signal processing (DSP) interference rejection techniques, such as a time-dependent adaptive filter (TDAF). Results indicate that the average CIR coverage can be increased from 90% to 98% for the seven cell reuse pattern assuming an 18 dB threshold. For a three cell frequency reuse pattern, the average CIR coverage is increased from 73% to 96% assuming the same threshold. The improvement is significant, even when a lower frequency reuse pattern is assumed. Thus, the TDAF improves the received signal quality and provides a means to increase the system capacity by using a lower frequency reuse pattern.

Blind adaptation algorithms for direct-sequence spread-spectrum CDMA single-user detection

Jeffrey H. Reed, Zecevic, N.;
Conference Paper Vehicular Technology Conference, 1997, IEEE 47th , vol.3, no., pp.2133,2137 vol.3, 4-7 May 1997

Single-user detection techniques mitigate multiple access interference and the near-far problem in direct-sequence spread-spectrum CDMA systems. Trained adaptation algorithms are commonly used to adapt the receivers. Two blind adaptation algorithms, the Griffths' (1989) algorithm and the linearly constrained constant modulus algorithm (LCCMA), are proposed for this application. Simulation results show a performance greatly superior to that of the conventional receiver and close to the case of trained adaptive receivers. Blind adaptation allows for a much more flexible network design by eliminating the need for a training sequence

Cell average carrier-to-interference coverage improvement by using DSP interference rejection techniques

Jeffrey H. Reed, Rong He;
Conference PaperVehicular Technology Conference, 1997, IEEE 47th , vol.2, no., pp.1079,1083 vol.2, 4-7 May 1997

The performance of a cellular phone system can be evaluated from several perspectives, one of which is the capacity. The capacity of a cellular system can be described by the cell carrier-to-interference ratio coverage (or the percentage of a cell area in which the carrier-to-interference ratio (CIR) is greater than a specific threshold). A theoretical form of the cell carrier-to-interference ratio coverage is derived for both the forward and reverse links. The cell average CIR coverage is also compared to the cell worst case CIR coverage, where the mobile is at the edge of its serving cell but is at the location closest to its interfering cell. The analysis is used to show how the coverage and the capacity can be improved by incorporating digital signal processing (DSP) interference rejection techniques, such as a time-dependent adaptive filter (TDAF). Results indicate that the average CIR coverage can be increased from 90% to 98% for the seven cell reuse pattern assuming an 18 dB threshold. For a three cell frequency reuse pattern, the average CIR coverage is increased from 73% to 96% assuming the same threshold. The improvement is significant, even when a lower frequency reuse pattern is assumed. Thus, the TDAF improves the received signal quality and provides a means to increase the system capacity by using a lower frequency reuse pattern.

Cell average carrier-to-interference coverage improvement by using DSP interference rejection techniques

Jeffrey H. Reed, Rong He;
Conference PaperVehicular Technology Conference, 1997, IEEE 47th , vol.2, no., pp.1079,1083 vol.2, 4-7 May 1996

The performance of a cellular phone system can be evaluated from several perspectives, one of which is the capacity. The capacity of a cellular system can be described by the cell carrier-to-interference ratio coverage (or the percentage of a cell area in which the carrier-to-interference ratio (CIR) is greater than a specific threshold). A theoretical form of the cell carrier-to-interference ratio coverage is derived for both the forward and reverse links. The cell average CIR coverage is also compared to the cell worst case CIR coverage, where the mobile is at the edge of its serving cell but is at the location closest to its interfering cell. The analysis is used to show how the coverage and the capacity can be improved by incorporating digital signal processing (DSP) interference rejection techniques, such as a time-dependent adaptive filter (TDAF). Results indicate that the average CIR coverage can be increased from 90% to 98% for the seven cell reuse pattern assuming an 18 dB threshold. For a three cell frequency reuse pattern, the average CIR coverage is increased from 73% to 96% assuming the same threshold. The improvement is significant, even when a lower frequency reuse pattern is assumed. Thus, the TDAF improves the received signal quality and provides a means to increase the system capacity by using a lower frequency reuse pattern.

The dynamic range enhancement technique applied to an AMPS and CDMA cellular environment

Jeffrey H. Reed,Cheng, F.; Lemson, P.; Jacobs, F.,
Conference PaperVehicular Technology Conference, 1996. Mobile Technology for the Human Race., IEEE 46th , vol.2, no., pp.1057,1059 vol.2, 28 Apr-1 May 1996

The need for extremely low cost cellular systems in the PCS band can be accomplished by remote antennas which collect the radiated RF signals and forward the composite received signal over an optical fiber link to a central location for processing. Analog modulation of the RF signal for transmission over the fiber is less complex and potentially less expensive, but the drawback is the dynamic range limitation of the laser modulator. A new approach for enhancing the dynamic range of a signal that is limited by the dynamic range of the interface to the transmission channel has been introduced. This approach, called the dynamic range enhancement technique (DRET), is well suited to overcome the remote antenna performance limitation and for other similar applications. This paper evaluates and compares the performance of the DRET to the AGC approach, applied to a mixture of direct sequence spread spectrum (DS/SS) signals and AMPS signals, for dynamic range enhancement of the RF to fiber interface

Co-channel interference rejection using a model-based demodulator for AMPS and NAMPS

Jeffrey H. Reed,Welborn, M.L.;
Conference PaperVehicular Technology Conference, 1996. Mobile Technology for the Human Race., IEEE 46th , vol.2, no., pp.1312,1316 vol.2, 28 Apr-1 May 1996

Co-channel interference is a major problem that limits the cell capacity in AMPS systems. For a digital implementation of an AMPS receiver, a quadrature demodulator would typically be used. This paper details the development of a demodulator that uses model-based frequency estimation to demodulate the frequency-modulated AMPS signal. This new technique shows improved performance in the presence of cochannel interference. Additionally, this technique has been used to develop a class of extensions for a conventional quadrature demodulator that provide improved performance in the presence of channel noise

Information Assurance of LTE-Advanced Self-Organizing Networks

Jeffrey H. Reed, Munawwar Sohul; Raghuprasad Bettadapura; Aman Singhal
Conference Paper SDR-WINNFORUM, 2014; Session 4A; SDR Architectures and Implementations II

One of the most anticipated features of LTE-Advanced is Self-Organizing Network (SON) - the capability to configure and optimize the network automatically by adapting to network characteristics and failures. This capability results in reduced human intervention in network operations and is essential to achieve the capacity promise of 4G, especially for small cell deployments in a Het-Net scenario. However, SON functionalities introduce new network vulnerabilities. Network intelligence and behavior characterization could reduce throughput. Node emulation attack could decreases cell coverage, affect scheduling algorithms and serving node preferences. Automation requires measuring the environment through sensing, but an intruder can modify these measurements and control reports. Although the security implication of SON is a very important aspect, there has not been any significant research done so far. This paper investigates the security vulnerabilities of SON and identifies the point of vulnerabilities for intrusion, and possible security threats and their expected impact on system performance. A focused analysis on the impact of node emulation attack on the Inter-Cell Interference Coordination (ICIC) is presented here. Anomaly detection is used as the intrusion detection technique to identify the malicious intrusion. We devised two anomaly detectors: correlation band detection with low probabilities of false alarm and missed detection and threshold detection. Based on the decisions from the intrusion detectors necessary modification was applied to the system parameters to recover from the attack. Simulation results show reasonable improvement in system performance in terms of cell-edge users SIR and throughput due to the proposed detection and recovery scheme.

Quality of Service Assurance for Shared Spectrum Systems

Jeffrey H. Reed, Munawwar M Sohul; Xiaofu Ma; Taeyoung Yang;
Conference Paper Military Communications Conference (MILCOM), 2014 IEEE , vol., no., pp.1471,1476, 6-8 Oct. 2014

Effective duration of a spectrum opportunity is an important factor for delivering any desired level of Quality-of-Service (QoS) to the secondary users (SU) in shared bands. Previous research efforts addressing the opportunity duration primarily focus on QoS prediction by the SUs using sensing and/or database approach. However, these initiatives to predict the opportunity duration and achievable QoS have a number of issues, such as prediction errors and computational overhead. In this paper, we present a QoS Assurance (QoSA) approach, in place of QoS prediction, centered around the Spectrum Access System (SAS) to get an idea about the opportunity duration with minimal involvement from the primary user (PU). In the existing approaches, the PU is not involved in the SU operation to avoid exposure of sensitive operational information. To address this concern, we propose an "Opportunity Clustering" mechanism that reduces the likelihood of information exposure. This paper mainly focuses on the interference avoidance and achievable SU throughput improvement due to the QoSA approach. We present the QoSA approach and the SAS framework that incorporates the proposed approach. We also present different QoSA schemes to improve the achievable SU throughput. Simulation results validate the improvement offered by the QoSA approach in terms of interference avoidance and throughput achieved by the SU.

Meeting the Nation's Telecommunications Needs

Jeffrey Reed
Conference Paper Telecommunications Research and Engineering at the Communications Technology Laboratory of the Department of Commerce; December 2015

Abstract:

The 2006 National Research Council report Renewing U.S. Telecommunications Research observed that “the telecommunications industry remains of crucial importance to the United States as a society, that a strong telecommunications research capability continues to be essential to the health and competitiveness of this U.S. industry internationally, and that the health of this industry strongly affects the U.S. economy in many ways.”1 In recent years, use of radio-frequency (RF) communications has grown tremendously, making it especially important to use the RF spectrum more efficiently.

The Department of Commerce (DOC) operates two laboratories concerned with communications technologies collocated at its Boulder, Colorado, campus (referred to collectively in this report as the Boulder telecommunications laboratories). The National Telecommunications and Information Administration (NTIA) operates a telecommunications research and engineering laboratory, the Institute for Telecommunication Sciences (ITS). ITS serves as a principal federal resource for solving the telecommunications concerns of federal agencies, state and local governments, private corporations and associations, standards bodies, and international organizations. ITS helps carry out NTIA’s mission by performing research and engineering to support government and private industry in managing the radio spectrum and making effective use of new technologies. Much of the ITS annual operating budget comes from federal and private research sponsors rather than NTIA’s direct appropriation. In 2014, the National Institute of Standards and Technology (NIST) established the Communications Technology Laboratory (CTL) to merge several current NIST laboratories into a single laboratory and to promote standards and metrology in the area of communications technologies. CTL develops appropriate measurements and standards to enable interoperable public safety communications, effective and efficient spectrum use and sharing, and advanced communication technologies. In June 2013, NTIA announced an agreement with NIST to establish a national Center for Advanced Communications (CAC) to better coordinate telecommunications-related research and engineering activities of ITS and NIST (now CTL). Figure P.1 outlines the organizations of the Boulder telecommunications laboratories. This study originates in part from language in House Report 112-463,

Defining Incumbent Protection Zones on the Fly: Dynamic Boundaries for Spectrum Sharing

S. Bhattarai, A. Ullah, J. Park, J. Reed, D. Gurney, and B. Gao
Conference Paper2015 IEEE International Symposium on Dynamic Spectrum Access Networks (DySPAN), Sweden, Oct. 2015

Abstract

In spectrum sharing, a spatial separation region is defined around primary users (PUs) to protect them from secondary user (SU)-induced interference. This protection region— referred to by a number of names, such as an exclusion zone (EZ) or a protection zone (PZ)—has a static boundary, and this boundary is determined very conservatively to provide an additional margin of protection for the PUs. This legacy notion of interference protection is overly rigid, and often results in poor spectrum utilization efficiency. In this paper, we propose a novel framework for prescribing interference protection for the PUs that addresses some of the limitations of legacy EZs. Specifically, we introduce the concept of Multi-tiered Incumbent Protection Zones (MIPZ), and show that it can be used to dynamically adjust the PU’s protection boundary based on the radio environment, network conditions, and the PU interference protection requirement. MIPZ can serve as an analytical framework for quantitatively analyzing a given PZ to gain insights on and determine the tradeoffs between interference protection and spectrum utilization efficiency. It allows a number of SUs, say N, to operate closer to the PU, and improves the overall spectrum utilization efficiency while ensuring a probabilistic guarantee of interference protection to the PU. We leverage the combined power of database-driven spectrum sharing and stochastic optimization theory for dynamically computing the zone boundary and the value of N. Using extensive simulation results, we demonstrate that the proposed framework improves spectrum utilization efficiency by adapting to the changing interference environment through dynamic adjustments of the zone boundary.

Coexistence between Radar and LTE-U Systems: Survey on the 5 GHz Band

Mina Lbib, Jeffrey Reed, Anthony Martone, Amir Zaghloul
Conference PaperAccepted to the International Union of Radio Science (URSI), 2016

Abstract

LTE (Long Term Evolution) technology is unarguably becoming the primary standard for 4G cellular networks. But due to the tremendous growth in data traffic, LTE for Unlicensed Spectrum (LTE-U) has been proposed to allow cellular network operators to meet such high demands in data traffic. The initial studies for the choice of the unlicensed frequency bands for LTE-U suggested using the 5 GHz frequency band. The 5 GHz band is mainly occupied by different radar systems and by the 802.11 technology (Wi-Fi). There are different regulations imposed by the Federal Communication Commission (FCC) for each sub-band of the 5 GHz band to allow fair spectrum sharing. In this paper, we present a survey about the RF regulations and the different radar types within the different sub-bands of the 5 GHz band and we introduce the major approaches for spectrum sharing techniques.

Analyzing and Enhancing the Resilience of LTE/LTE-A Systems to RF Spoofing

Mina Labib, Jeffrey Reed, Vuk Marojevic
Conference Paper IEEE Conference on Standards for Communications and Networking,

Abstract:

Abstract Unavailable