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For information on the Wireless @ Virginia Tech Seminar Series, please contact Dr. Harpreet Dhillon.

2015 Seminars have now been archived here.

2014 Seminars are archived here.


Spring, 2018

Date: March 30, 2018

Speaker: Dr. Sudeep Bhattarai, Wireless@VT

Time: 2:40 - 3:40. Lavery Hall, Room 330

Title: Performance Analysis of IEEE 802.11ax in a Heterogeneous Wi-Fi Network

Abstract: Legacy Wi-Fi technologies are inept at coping with the traffic demands of users in a congested environment because their medium access technique, which is common to all legacy technologies, is suboptimal in terms of spectrum utilization efficiency. To address this limitation, the next generation Wi-Fi technology-referred to as IEEE 802.11ax-introduces some key features, most notably the use of Multi-User Orthogonal Frequency Division Multiple Access (MU-OFDMA) technology in its medium access control (MAC) layer. MU-OFDMA allows multiple users to transmit simultaneously in smaller sub-channels (a.k.a. resource units (RUs)) in the uplink (UL) as well as the downlink (DL), thereby improving the 802.11ax MAC efficiency, especially when the network size is large. Furthermore, for UL MU-OFDMA transmissions, in order to provide a flexible support to all stations (STAs) in the network, 802.11ax provisions Random Access (RA) RUs as well as Scheduled Access (SA) RUs. In this talk, we first present our analysis on the MAC layer performance of the new MU OFDMA-based 802.11ax and summarize our findings. Second, we discuss the impact of different RA RU and SA RU distributions on the network performance and devise an algorithm for optimal RU allocation such that the overall 802.11ax throughput is maximized. Third, we study how to share the airtime between legacy 802.11 and 802.11ax transmissions fairly when both categories of STAs are jointly served by a single access point (AP) that can support both 802.11ax and legacy Wi-Fi. Finally, we present our results, based on our implementation of the proposed 802.11ax MAC on network simulator-3 (NS-3), and validate our analysis by comparing theoretical results with those obtained from extensive NS-3 simulations.

Sudeep Bhattarai received his Bachelor’s degree in electronics and communication engineering from Tribhuvan University, Nepal, and his Master’s degree in electrical engineering from Tennessee State University, USA, in 2011 and 2013, respectively. He recently defended his Ph.D. in Electrical Engineering at Virginia Tech. Sudeep was a research intern at AT&T Labs and Google in summer 2014 and summer 2016 respectively. Sudeep is a recipient of the best paper award at IEEE DySPAN 2014. His current research interests include dynamic spectrum sharing, coexistence among heterogeneous wireless technologies, next generation wireless networks, and privacy issues in wireless communications.

Date: March 23, 2018

Speaker: Vishnu Vardhan Chetlur, Wireless@VT

Time: 2:40 - 3:40. Lavery Hall, Room 330

Title: Modeling and Analysis of Vehicular Communication Networks: A Stochastic Geometry approach

Abstract: Vehicular communication, which collectively refers to vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication, has enabled the vehicular nodes to share information with each other and also with roadside units (RSUs) to improve the road safety and transport efficiency. With autonomous vehicles becoming a reality in the near future, the data traffic originating from vehicular networks is expected to increase many folds while also putting more stringent latency and connectivity constraints compared to the networks of today. In the latest 3GPP release, the support for vehicle-to-everything (V2X) communication has also been added to the long term evolution (LTE). Vehicular networks have a peculiar spatial geometry as the locations of nodes is restricted to the roadways. In this talk, we will discuss a doubly stochastic spatial model that can capture this coupling between the nodes and the underlying infrastructure. We will then analyze the signal-to-interference ratio (SIR) based coverage of a typical vehicular user in the network. The analysis reveals some interesting trends in the coverage as a function of density of nodes and also the layout of roads. These results also underline the importance of the doubly stochastic model for the analysis of vehicular networks.

Vishnu Vardhan Chetlur received the B.E. degree (Hons.) in electronics and communications engineering from the Birla Institute of Technology and Science (BITS), Pilani, India, in 2013. He graduated top of his class in the Department of Electrical Engineering at BITS, and received the institute Silver Medal for being ranked second in the whole institute. He was a recipient of the BITS Merit Scholarship for his excellence in academics. After his bachelor's graduation, he was a Design Engineer with Redpine Signals Inc., for two years. He is currently pursuing the Ph.D. degree with Virginia Tech under the supervision of Dr. Harpreet S. Dhillon. His research interests include wireless communication, vehicular networks, stochastic geometry and smart cities.



Date: February 23, 2018

Speaker: Dr. Mahi Abdelbar, Wireless@VT

Time: 2:40 - 3:40. Lavery Hall, Room 330

Title: : Pedestrian GraphSLAM using Smartphone-based PDR in Indoor Environments

Abstract: Simultaneous Localization and Mapping (SLAM) for pedestrians is a relatively new approach for the indoor localization problem. Adopted from robotics, SLAM for indoor pedestrians presents a new and efficient framework for tracking users’ movement trajectories within buildings. With the advancements in smartphone technology, pedestrian SLAM has transitioned towards utilizing smartphones’ integrated sensors through Pedestrian Dead-Reckoning (PDR) techniques. GraphSLAM models the spatial structure of a sequence of user’s positions inside a building as a graph optimization problem, based on estimated positions through PDR. In addition, GraphSLAM depends on loop-closures and/or landmarks as constraints in the trajectory estimation problem, which in pedestrian SLAM is still very challenging.

In this talk, we first present an overview of the pedestrian SLAM problem and its challenges, as a solution to the indoor localization problem. This work comes at the intersection of indoor localization using movement trajectories, pedestrian dead-reckoning (PDR) and Graph Simultaneous Localization and Mapping (GraphSLAM). We will present an improved approach for processing measurements from smartphones’ integrated sensors, more specifically accelerometers and gyroscopes. Next, we will integrate the smartphone sensors’ measurements into a pedestrian GraphSLAM optimization problem. Finally, we present a new collaborative framework for optimizing multiple users’ movement trajectories using Bluetooth Low Energy (BLE) detection between smartphones.

Mahi Abdelbar graduated with honors and received the M.S. degree from the Electronics and Communications Department at the Engineering Faculty, Mansoura University in Egypt. She recently defended her PhD at the Wireless@VT lab, Bradley Department of Electrical and Computer Engineering at Virginia Tech. Her research interests include indoors positioning and localization, distributed signal detection and classification, sensor fusion, and machine learning algorithms.



Date: February 16, 2018

Speaker: Atieh R. Khamesi, Visiting Ph.D. student, Wireless@VT

Time: 2:40 - 3:40. Lavery Hall, Room 330

Title: : Energy Harvesting and Cell Zooming in Heterogeneous Random Cellular Networks

Abstract: In this talk, we investigate network efficiency and green communications in heterogeneous cellular networks (HetNets) as a promising network structure for the 5G using stochastic geometry. We introduce two Cell Zooming (CZ) techniques applying to HetNets. With focus on green communications, we present a K−tier HetNet in which BSs are only powered by energy harvesting. Despite the uncertain nature of energy arrivals, combining two CZ techniques, namely telescopic and ON/OFF scenarios, enables us to achieve higher network performance in terms of the coverage and blocking probabilities while reducing the total power consumption and increasing the energy and spectral efficiencies.

Atieh R. Khamesi is a Ph.D. student at University of Padova, Italy, advised by Prof. Michele Zorzi. She is currently a visiting student in the Bradley Department of Electrical and Computer Engineering at Virginia Tech. She received her B.Sc. degree in Electrical Engineering from Ferdowsi University of Mashhad, Iran in 2011 and M.Sc. degree in Communication systems from University of Tehran, Iran in 2014. She was visiting researcher at University of Padova from Sep. 2013 to Feb. 2014. Her research interests include green communication, energy harvesting and stochastic geometry.



Date: February 9, 2018

Speaker: Peter Delos, Technical Lead at Analog Devices Inc., Aerospace and Defense Group

Time: 2:40 - 3:40. Lavery Hall, Room 330

Title: Phased Arrays: Fundamentals and the Enabling RF Electronics

Abstract: A large proliferation of digital beamforming phased-array technology has emerged in recent years. The technology has been spawned by both military and commercial applications fueled by the rapid advancements in RF integration at the component level. This presentation will review the radio frequency electronics behind the antenna elements making the phased array advancements possible. Benefits and challenges of varied architecture choices will be described along with technology advancements enabling the next generation of digital beamforming phased arrays.

Peter Delos is a Technical Lead at Analog Devices, Inc., in the Aerospace and Defense Group. He received his BSEE from Virginia Tech in 1990 and MSEE from NJIT in 2004. He has over 25 years of industry experience. Most of his career has been spent designing advanced RF/Analog systems at the architecture level, PWB level, and IC level. His career includes various positions in the Naval Nuclear Power submarine program, and at Lockheed Martin, Moorestown, NJ, working on multiple Radar and EW programs. In 2016, he accepted his current position with Analog Devices in Greensboro, NC. He is focused on miniaturizing high performance Receiver, Waveform Generator, and Synthesizer designs for Phased Array applications.

Date: january 26, 2018

Speaker: Prof. Lingjia Liu, Associate Professor, Wireless@VT, Department of ECE, Virginia Tech

Time: 2:40 - 3:40. Lavery Hall, Room 330

Title: Rateless Coding-based Cooperative Transmission/Routing for Wireless Networks

Abstract: Cooperation among the nodes of wireless networks can increase communication reliability, reduce energy consumption, and decrease latency. The possible improvements are even more significant when nodes perform mutual-information accumulation, e.g., by using rateless codes. In this talk, we investigate communication problems in such networks. That is, we investigate how advanced physical (PHY) layer coding techniques (e.g. rateless coding) would impact various network layers of a wireless network (e.g., resource allocation and routing strategies). Rateless coding-based cooperative communication for 1D line network, 2D grid network, 2D random network, and dynamic spectrum access network will be presented and hardware demo using USRP N210s will be discussed. All these findings suggest that rateless coding-based cooperative routing can significantly improve network performance in an efficient and robust way.

Dr. Lingjia Liu is an Associate Professor in the ECE Department at Virginia Tech (VT). He received the B.S. degree in Electronic Engineering from Shanghai Jiao Tong University, Shanghai, China and Ph.D. degree in Electrical Engineering from Texas A&M University, College Station, Texas. He spent the summer of 2007 and spring of 2008 in the Mitsubishi Electric Research Laboratory (MERL). Prior to joining VT, he was an Associate Professor in the EECS Department at the University of Kansas (KU). He spent 3+ years working in the Standards & Mobility Innovation Lab of Samsung Research America (SRA) where he received Global Samsung Best Paper Award twice (in 2008 and 2010 respectively). He was leading Samsung’s efforts on multiuser MIMO, coordinated multipoint (CoMP), and heterogeneous networks in LTE/LTE-Advanced standards.

Dr. Liu is currently an Editor for the IEEE Trans. Wireless Commun., an Editor for the IEEE Trans. Commun. and Associate Editor for the EURASIP J. on Wireless Commun. and Netw. and Wileys Intl J. on Commun. Systems. His general research interests mainly lie in emerging technologies for 5G cellular networks including machine learning for wireless networks, massive MIMO, massive MTC communications, and mmWave communications. Dr. Liu received Air Force Summer Faculty Fellow from 2013 to 2017, Miller Scholar at KU in 2014, Miller Professional Development Award for Distinguished Research at KU in 2015, and 2016 IEEE GLOBECOM Best Paper Award.



Fall, 2017

Date: December 8, 2017

Time: 2:35 - 3:35. Lavery Hall, Room 330

Title: Wireless Communications with Unmanned Aerial Vehicles: Fundamentals, Deployment, and Optimization

Abstract: The use of aerial platforms such as unmanned aerial vehicles (UAVs) and drones is a promising solution for providing reliable and cost-effective wireless communications. In particular, UAVs can be quickly and efficiently deployed to support cellular networks and enhance their quality-of- service (QoS) by establishing line-of-sight (LoS) communication links. With their inherent attributes such as mobility, flexibility, and adaptive altitude, if properly deployed, UAVs admit several key potential applications in wireless systems. For instance, UAVs can be deployed to complement existing cellular systems by providing additional capacity to hotspot areas as well as to provide network coverage in emergency and public safety situations. Despite the several benefits and practical applications of using UAVs as aerial base stations, one must address many technical challenges such as three-dimensional (3D) deployment, performance analysis, mobility, air-to-ground channel modeling, user association, and flight time optimization.

This presentation will include an overview on the UAV-based communication systems, along with their key opportunities and challenges. Furthermore, two technical challenges in UAV-enabled wireless networks are investigated. In the first work, UAV communications under flight time considerations is studied. In particular, a novel framework for optimizing the performance of a UAV-based wireless system in terms of the amount of data transmitted to users as well as UAVs’ hover duration is proposed. In the second work, the efficient deployment and mobility of multiple UAVs used to collect data from ground Internet of Things (IoT) devices, is investigated.

Bio: Mohammad Mozaffari received his BSc in Electrical Engineering from Sharif University of Technology in Iran, and his MSc in Geomatics Engineering from University of Calgary, Canada. He is currently a PhD candidate at the Bradley Department of Electrical and Computer Engineering at Virginia Tech. His research interests include wireless communications and statistical signal processing with focus on unmanned aerial vehicle (UAV) communications, 5G networks, satellite communications and localization.




Date: November 10, 2017

Time: 2:35 - 3:35, Lavery Hall, Room 330

Title: Modeling and Analysis of Emerging Trends in Device-to-Device Networks

Abstract: Device-to-device (D2D) communications enabling direct communication between devices located in close proximity have several benefits compared to the conventional approach of communicating through a base station in a cellular network. First, the spectral efficiency of the direct link is typically much higher due to a smaller link distance. Second, this circumvents the need to establish an end-to-end link through a base station, thereby offloading traffic from cellular networks. Third, while the D2D network can be visualized as an ad hoc network, it incurs a much lower protocol overhead due to the assistance it gets from the existing cellular network. All these benefits make it an attractive component for both the current 4G and the future 5G networks. In this talk, I will present a new comprehensive framework for the analysis of D2D networks in which the device locations are modeled by a Poisson cluster process. This model accurately captures the fact that the devices engaging in D2D communication typically form small clusters. Using this model, we characterize the performance of a variety of device and cluster-centric content placement strategies. One of the key outcomes of our analysis is evaluating an optimum number of D2D transmitters that must be simultaneously activated per cluster to maximize area spectral efficiency.


Mehrnaz Afshang received her B.E. degree in Electrical Engineering from Shiraz University of Technology, Iran, in 2011 and her Ph.D. degree from Nanyang Technological University, Singapore, in 2016. During her Ph.D., she was a recipient of the SINGA Fellowship. Since January 2015, she has been a visiting student and later a postdoctoral associate in the Bradley Department of Electrical and Computer Engineering at Virginia Tech working with Dr. Dhillon. Her research interests include communications theory, stochastic geometry, device-to-device networks, and wireless ad hoc and heterogeneous cellular networks. She was selected as one of the 60 world’s brightest women to participate in the Rising Stars Workshop in 2016.




Date: November 3, 2017

Time: 2:45 - 3:45

Title: Parametric Channel Estimation for 3D mmWave Massive MIMO/FD-MIMO Systems

Abstract: In order to meet the challenge of increasing data-rate demand as well as the form factor limitation at the base station (BS), 3D massive multiple-input multiple-output (MIMO)/full dimensional(FD) MIMO has been introduced as one of the enabling technologies for fifth-generation mobile cellular systems. In 3D massive MIMO systems, especially in TDD mode of operation, a BS will rely on the uplink sounding signals from mobile stations to obtain the spatial information for downlink MIMO operations. Accordingly, multi-dimensional parameter estimation for the massive MIMO channel becomes crucial for such systems to realize the predicted capacity gains.

In this talk, we will be presenting a channel estimation framework for 3D massive MIMO/FD-MIMO systems under parametric channel modeling. We will first introduce a separate low-complexity parameter estimation algorithm based on unitary transformation. We will then present some analytical characterizations for the channel estimation performance in terms of mean squared error (MSE), and highlight on the key system-level intuitions we can have from these analytical results. We will demonstrate how a matrix-based joint parameter estimation can achieve superior performance than the separate estimation method. Finally, we will conclude the presentation by showing how the channel parameters estimated in the uplink can be utilized in optimum downlink precoder design.

RubayetRubayet Shafin received his BS degree in Electrical and Electronics Engineering from Bangladesh University of Engineering and Technology in 2013, and MS degree in Electrical Engineering from University of Kansas (KU) in 2017. From 2014 to 2017, he was affiliated with Information and Telecommunication Technology Center (ITTC) at KU, where he worked on wireless channel estimation, precoder design, and performance characterization for 3D mmWave and massive MIMO systems. He spent his summer 2017 as a research intern at Huawei R&D, USA, where he worked on the development of a novel channel estimation framework for 5G system. His present research interests include different physical layer aspects of 5G network and application of machine learning in wireless communication. He is currently a PhD student in the ECE department at Virginia Tech, and is advised by Dr. Lingjia Liu.


Date: October 27, 2017

Time: 2:35pm-3:35pm

Title: Integrated mmWave Access and Backhaul in 5G: Bandwidth Partitioning and Downlink Analysis

Abstract: With the increasing network densification, it has become exceedingly difficult to provide traditional fiber backhaul access to each cell site, which is especially true for small cell base stations (SBSs). The increasing maturity of millimeter wave (mmWave) communication has opened up the possibility of providing high-speed wireless backhaul to such cell sites. Since mmWave is also suitable for access links, the third generation partnership project (3GPP) is envisioning an integrated access and backhaul (IAB) architecture for the fifth generation (5G) cellular networks in which the same infrastructure and spectral resources will be used for both access and backhaul.

In this talk, I will be presenting our recently developed analytical framework for IAB-enabled cellular network using which we can accurately characterize its downlink rate coverage probability. For this model, we study the performance of two backhaul bandwidth (BW) partition strategies, (i) equal partition: when all SBSs obtain equal share of the backhaul BW, and (ii) load-based partition: when the backhaul BW share of an SBS is proportional to its load. Our analysis shows that depending on the choice of the partition strategy, there exists an optimal split of access and backhaul BW for which the rate coverage is maximized. Further, we have found that there exists a critical volume of cell-load (total number of users) beyond which the gains provided by the IAB-enabled network disappear and its performance converges to that of the traditional macro-only network with no SBSs. We will conclude the talk by demonstrating our initial results on the impact of different cell association strategies using sub-6 GHz and mmWave signalling on the rate coverage probability.

Interested readers can refer to for more rigorous details.

Bio: SahaChiranjib Saha received the Bachelor in Engineering degree in electronics and telecommunication engineering from Jadavpur University, India, in 2015. He is a third year Ph.D. student in the Bradley Department of Electrical and Computer Engineering, Virginia Tech, advised by Dr. Harpreet S. Dhillon. He was the recipient of the Wireless Fellowship Award by Wireless@VT, Virginia Tech, in 2015. His research interests have been broadly focused on modelling and analysis of heterogeneous cellular networks using the tools of stochastic geometry and the theory of point processes. He is currently working on the backhaul design aspects of 5G HetNets using mmWave communication.




Two Seminars This Week!

Date: October 6, 2017

Time: 3 pm. - 3:40 p.m., at Lavery Hall,, Room 330

Title: Spectrum Sharing Test & Demonstration - LTE Field Measurement

Abstract: As part of the DoD Transition Plan for the Advanced Wireless Services (AWS) -3, the Defense Information Systems Agency (DISA) Defense Spectrum Organization (DSO) has sponsored the Spectrum Sharing Test & Demonstration (SST&D) program. The current objectives of the SST&D Program include:

· Facilitating expedited and expanded entry of commercial wireless network deployments into the 1755-1780 MHz band.

· Identify, demonstrate, and operationalize interference mitigation techniques consistent with commercial Long Term Evolution (LTE) standards that support increased sharing between LTE and incumbent DoD systems

· Prototype and demonstrate advanced sharing concepts for long-term sharing in the 1755-1780 MHz band.

The SST&D LTE Characterization activity is focused on understanding LTE uplink emissions under a variety of operating conditions (e.g., traffic loading; ISD; power control algorithms; resource allocation algorithms; etc.) and in the presence of interfering signals (e.g. DoD SATOPS). As part of the LTE Characterization activity, the team is deploying LTE Field Measurement Systems to perform LTE network testing and measurements providing real network operation statistics to inform our LTE network modeling efforts and enhance spectrum coexistence assessments.

The LTE Field Measurement System provides a means to collect and record sector DL and UL control signaling and simultaneous UL RF emissions. This measurement system paired with our developed field measurement data analysis and reporting capability provides the ability to generate network UL parameter statistics from real LTE networks.


Mike SmithMr. Mike Smith is a Senior Systems Engineer for the Virginia Tech Applied Research Corporation (VT-ARC). Mr. Smith is an experienced Systems Engineer with functional expertise in Wireless Networking, Communication Systems, RF Design, Semiconductor Manufacturing, and Satellite Communications. He has demonstrated experience in planning, analysis, design, and delivery of communications systems for the DoD and Commercial Service Providers. Prior to joining VT-ARC, Mr. Smith was a Systems Engineer at Harris Corporation Electronic Systems focused on developing and managing Software Defined Tactical Radios and Power Amplifiers for DoD and foreign military customers. Earlier in his 22-year Harris career, Mike focused on business development for Harris commercial satellite systems, serving as Lead Systems Engineer on several payload programs and proposals emphasizing the application of phased array antenna systems. Earlier in his career, Mr. Smith also successfully led the development and implementation of semiconductor manufacturing yield management methodologies at Filtronic Solid State and Zeevo, Inc. Mr. Smith received a B.S. degree in Electrical Engineering from Virginia Tech in 1985.


Date: October 6, 2017

Time: 4:00 pm. - 5 pm. Location: Goodwin Hall, Room 190

Title: Dependability for Computer Systems meets Data Analytics

Abstract: We live in a data-driven world as everyone around has been telling us of late. Everything is generating data, sometimes volumes of it, from the sensors embedded in our physical spaces to the large number of machines in data centers which are being monitored for a wide variety of metrics. The question that we pose is: Can the volume of data be used for improving the dependability of computing systems?

Dependability is simply the property that the system continues to provide its functionality despite the introduction of faults, either accidental faults (design defects, environmental effects, etc.) or maliciously introduced faults (security attacks, either external or internal). The computing systems that we target have been increasing in scale, both in terms of the number of executing elements and the amount of data that they need to process. For example, a large number of data-spewing sensors on mobile and embedded devices coupled with the large number of such devices show such increases in scale. We have been addressing the dependability challenge through large-scale data analytics in three broad domains: embedded and mobile networks, scientific computing clusters and applications, and computational genomics. In this talk, I will first give a high-level view of the dependability challenges in these three domains, how data analytics has been brought to bear on these challenges, and some of our key results. I will then go into two recent developments: dependability in a cellular network and dependability through approximating computation. In the first development, we answer the question – can the cellular network and the smart mobile devices working together mitigate the problem of network outages or reduced data bandwidth. In the second development, we answer the question – can the limitations of human perception be leveraged to approximate certain computation and thus allow the computation to meet timing guarantees, even when executing on resource-constrained platforms. A common example is video processing where the human visual system is forgiving for certain kinds of inaccuracy. I will conclude with some insights about how the power of data analytics can help us create more dependable systems.


Saurabh BagchiSaurabh Bagchi is a Professor in the School of Electrical and Computer Engineering and the Department of Computer Science at Purdue University in West Lafayette, Indiana. He is the founding Director of a university-wide resiliency center at Purdue called CRISP (2017-present). He is an ACM Distinguished Scientist (2013), a Senior Member of IEEE (2007) and of ACM (2009), a Distinguished Speaker for ACM (2012), and an IMPACT Faculty Fellow at Purdue. He is the recipient of an IBM Faculty Award (2014), a Google Faculty Award (2015), and the AT&T Labs VURI Award (2016). He was elected to the IEEE Computer Society Board of Governors for the 2017-19 term.

Saurabh's research interest is in distributed systems and dependable computing. He is proudest of the 18 Ph.D. students who have graduated from his research group and are in various stages of building wonderful careers in industry or academia. In his group, he and his students have far too much fun building and breaking real systems. Saurabh received his MS and Ph.D. degrees from the University of Illinois, Urbana-Champaign and his BS degree from the Indian Institute of Technology Kharagpur, all in Computer Science.



Title: Spectrum Sharing Test & Demonstration - LTE Field Measurement

Date: September 29, 2017

Title: Adaptive Pilot Patterns for CA-OFDM Systems in Vehicular Channels

Abstract: 5G is expected to bring vast performance improvements in various aspects, particularly in user data rates. At the PHY layer, enhancements in spectral efficiency are achieved by a combination of technologies, such as massive MIMO, carrier aggregation, higher-order modulation and spectrally efficient multicarrier waveforms. Minimizing the system overhead is one of the critical challenges that standardization bodies are facing to meet the performance criteria promised for 5G. In this regard, pilot overhead is a major design issue at the PHY layer. Pilots (or reference signals) are necessary for mobile communication in dynamic environments and, therefore, cannot be eliminated. They enable accurate estimation of the channel state information (CSI) and hence, are necessary to truly realize the performance gains promised by these technologies. In this talk, we present our method to maximize throughput using pilot pattern adaptation in a MIMO-OFDM point-to-point link. Our algorithm is based on adapting the pilot density and power as a function of the channel fading characteristics using feedback of indices from a 'channel-statistics codebook' known to the transmitter and receiver. We demonstrate the throughput gains of our scheme when compared to LTE, in terrestrial and aerial vehicular channels. We extend this scheme to carrier aggregation (CA)-OFDM systems, and leverage knowledge about the frequency dependence of the channel statistics to minimize the feedback requirements. We conclude with a discussion on important practical considerations to realize adaptive pilot patterns in future wireless networks. This work was carried out under the supervision of Dr. Vuk Marojevic and Dr. Jeffrey H. Reed and has been accepted in a future issue of the IEEE Transactions on Vehicular Technology. Interested readers are encouraged to read the prepub versions on


IEEE Xplore: (DOI: 10.1109/TVT.2017.2751548)


Raghunandan RaoRaghunandan M. Rao received the B.Eng. degree in Telecommunication engineering from R V College of Engineering, Bangalore, India, in 2011, the M.Tech. degree in Laser Technology from the Indian Institute of Technology Kanpur, India in 2013, and the M.S. degree in Electrical Engineering from Virginia Tech (VT), Blacksburg, VA, USA, in 2016. He is currently working towards the Ph.D. degree in the Bradley Department of ECE, VT and is affiliated with the Wireless@VT research group. In the past he has worked as a summer intern at Blue Danube Systems Inc, Santa Clara, CA, USA. His research interests include LTE and 5G NR, mmWave wireless communications, massive MIMO, and spectrum sharing.



Date: September 15, 2017

Title: 3GPP-inspired Stochastic Geometry Models for Cellular Networks

Abstract: The growing complexity of heterogeneous cellular networks (HetNets) has necessitated a variety of user and base station (BS) configurations to be considered for realistic performance evaluation and system design. This is directly reflected in the HetNet simulation models used by the standardization bodies, such as the third generation partnership project (3GPP). Complementary to these simulation models, stochastic geometry-based approach, modeling the locations of the users and the K tiers of BSs as independent and homogeneous Poisson point processes (PPPs), has gained prominence in the past few years. Despite its success in revealing useful insights, this PPP-based model is not rich enough to capture all the spatial configurations that appear in real world HetNet deployments (on which 3GPP simulation models are based).

In this talk, we will demonstrate that modeling a fraction of users and some BS tiers alternatively with a Poisson cluster process (PCP) captures the aforementioned coupling, thus bridging the gap between the 3GPP simulation models and the PPP-based analytic model for HetNets. For this model, we will show that the downlink coverage probability of a typical user under maximum signal-to-interference-ratio association can be expressed in terms of the sum-product functionals over PPP, PCP, and its associated offspring point process, which are all characterized as a part of our analysis. Special instances of the proposed model will be shown to closely resemble different configurations considered in 3GPP HetNet models. Our analysis concretely demonstrates that the performance trends are highly sensitive to the assumptions made on the user and BS configurations. We will conclude the talk by elaborating on this by going into the scaling laws for such models, which will also reveal useful performance trends in the "ultra-dense" HetNet setting.

This is joint work with Chiranjib Saha and Mehrnaz Afshang. Interested readers can refer to,, and for more rigorous details.


Dr. DhillonHarpreet S. Dhillon received the B.Tech. degree in Electronics and Communication Engineering from IIT Guwahati in 2008, the M.S. degree in Electrical Engineering from Virginia Tech in 2010, and the Ph.D. degree in Electrical Engineering from the University of Texas at Austin in 2013. In academic year 2013-14, he was a Viterbi Postdoctoral Fellow at the University of Southern California. He joined Virginia Tech in August 2014, where he is currently an Assistant Professor of Electrical and Computer Engineering. He has also held short-term visiting positions at Alcatel-Lucent Bell Labs, Samsung Research America, and Qualcomm. His research interests include communication theory, stochastic geometry, and wireless ad hoc and heterogeneous cellular networks.

He is a recipient of five best paper awards including the 2016 IEEE Communications Society (ComSoc) Heinrich Hertz Award, the 2015 IEEE ComSoc Young Author Best Paper Award, the 2014 IEEE ComSoc Leonard G. Abraham Prize, and conference best paper awards at IEEE ICC 2013 and European Wireless 2014. His other academic honors include the 2017 Outstanding New Assistant Professor Award from the Virginia Tech College of Engineering, the 2013 UT Austin WNCG leadership award, the UT Austin MCD Fellowship, and the 2008 Agilent Engineering and Technology Award. He currently serves as an Editor for the IEEE Transactions on Wireless Communications, the IEEE Transactions on Green Communications and Networking, and the IEEE Wireless Communications Letters.


Spring, 2017

Date: Friday April 21, 2017

Title: Stochastic Geometry-based Modeling and Analysis of Citizens Broadband Radio Service System

Abstract: In April 2015, FCC approved (along with certain guidelines) the co-existence of the commercial networks alongside the incumbent systems in the underutilized 3.5 GHz band, a.k.a citizens broadband radio service (CBRS) band. In this talk, we will discuss the co-existence performance between a licensed and an unlicensed operator in this band. The focus of this talk will be on the successful application of tools from stochastic geometry to model and analyze the above system adhering to the key guidelines from the FCC such as protection zones around each licensed BS where the unlicensed BSs operation is prohibited and the use of contention-based channel access mechanism (CSMA-CA) among the unlicensed BSs. To this end, we will explore a couple of interesting point processes such as Poisson hole process and Matern hard-core process that are helpful in accurate modeling of the above system. We will also discuss the effect of different system parameters, such as protection zone radius, carrier sense threshold on the performance of both the operators in terms of their coverage probabilities and area spectral efficiencies.


PriyaPriyabrata Parida is a Ph.D. student in the Department of ECE at Virginia Tech. He is advised by Dr. Harpreet S. Dhillon. He received his bachelor’s degree in Electronics and Communications Engineering from the National Institute of Technology, Durgapur, India, in 2010, and his master’s degree in Telecommunications from the IIT Kharagpur, India, in 2015. His research interest includes modeling and analysis of fifth-generation cellular networks using tools from stochastic geometry, multi-antenna communication systems, and resource allocation in wireless systems. He has held summer internship position at MediaTek Inc., San Jose, USA, during 2016. In the past, he has worked at Idea cellular, a cellular operator in India, as an Assistant Manager, and at IIT Kharagpur as a Research consultant.


Date: Friday, April 7, 2017

Title: Joint Uplink and Downlink Coverage Analysis of Cellular-based RF-powered IoT Network

Abstract: Ambient radio frequency (RF) energy harvesting has emerged as a promising solution for powering small devices and sensors in massive Internet of Things (IoT) ecosystem due to its ubiquity and cost efficiency. In this presentation, a stochastic geometry-based analysis of the joint uplink and downlink coverage of cellular-based ambient RF energy harvesting IoT will be discussed. In the considered system, the cellular network is assumed to be the only source of RF energy. A time division-based approach is assumed for power and information transmission where each time slot is partitioned into three sub-slots: (i) charging sub-slot during which the cellular base stations (BSs) act as RF chargers for the IoT devices, which then use the energy harvested in this sub-slot for information transmission and/or reception during the following sub-slots, (ii) downlink sub-slot during which the IoT device receives information from the associated BS, and (iii) uplink sub-slot during which the IoT device transmits information to the associated BS. For this setup, the key technical challenges in deriving the joint uplink and downlink coverage probability are discussed.


Mustafa KishkMustafa Kishk is a Ph.D. student in the Bradley Department of Electrical and Computer Engineering at Virginia Tech under the supervision of Prof. Harpreet Dhillon. He received his B.Sc. and M.S. degrees in Electronics and Electrical Communications Engineering from Cairo University, Egypt, in 2013 and 2015, respectively. His research interests include stochastic geometry, energy harvesting communication networks, cognitive radio, physical layer security, and multi-user communications.



Date: Friday, March 31, 2017

Title: Robust Communications with Paramorphic Multicarrier Waveforms

Abstract: A method for constructing robust multicarrier waveforms through cyclostationary properties is proposed. Spectral redundancy is created through symbol repetition in both time and frequency, and the optimal filter is presented which combines the redundancies. The method is compared against other filtering techniques and error correcting codes. A background on cyclostationarity and Frequency Shift (FRESH) filtering is given to provide context.

Bio: Matt Carrick is a Ph.D. student studying under Dr. Jeff Reed. He received his BSEE from George Mason University in 2007 and his MSEE from Virginia Tech in 2009. He is interested in cyclostationarity, digital signal processing and multirate signal processing.




Date: Friday, March 3, 2017

Location: Room 155, Goodwin Hall

Time: 2:35 p.m.

Title: Coexistence of Dedicated Short Range Communications (DSRC) and Wi-Fi: Implications to Wi-Fi Performance

Abstract: The 5.9 GHz band is being actively explored for possible spectrum sharing opportunities between Dedicated Short Range Communications (DSRC) and IEEE 802.11ac networks in order to address the increasing demand for bandwidth-intensive Wi-Fi applications. This talk discusses our study on the implications of this spectrum sharing to the performance of Wi-Fi systems. Through experiments performed on our testbed, we first investigate band sharing options available for Wi-Fi devices. Using experimental results, we show the need for using conservative Wi-Fi transmission parameters to enable harmonious coexistence between DSRC and Wi-Fi. Moreover, we show that under the current 802.11ac standard, certain channelization options, particularly the high bandwidth ones, cannot be used by Wi-Fi devices without causing interference to the DSRC nodes. Under these constraints, we propose a Real-time Channelization Algorithm for Wi-Fi Access Points operating in the shared spectrum.


GuarangGaurang Naik is currently a Ph.D. candidate in Electrical Engineering at the Advanced Research in Information Assurance and Security (ARIAS) Lab at Virginia Tech. He is advised by Dr. Jung-Min (Jerry) Park, and his research focuses on problems related to dynamic spectrum sharing. He received his B.E. degree from the University of Mumbai, India, in 2012, and his M. Tech. degree from the Indian Institute of Technology Bombay in 2015.




Date: Friday, February 24, 2017

Speaker: Sundar Aditya (visiting Ph.D. student, University of Southern California)

Time: 2:35 p.m

Location: Goodwin Hall, Room 155

Title: Bayesian Multi-Target Localization under environment-induced correlated blocking


The canonical localization problem involves determining the position of one or more targets in an environment by analyzing wireless signals emanating from them at known receiver/anchor locations. This talk addresses the problem of localizing an unknown number of passive (i.e., reflecting) targets, all having the same radar signature, by a distributed radar consisting of single antenna transmitters and receivers that cannot determine directions of departure and arrival. Furthermore, the presence of multipath propagation and the possible (statistically dependent) blocking of the direct paths (DPs) are also considered. In its most general form, this problem can be cast as a Bayesian estimation problem where every multipath component is accounted for. However, when the environment map is unknown, this problem is ill-posed and hence, a tractable approximation is derived where only DPs are accounted for. In particular, we take into account the dependent blocking by distributed (i.e., non-point) obstacles in the environment which appears as a prior term in the Bayesian estimation framework. A sub-optimal polynomial-time algorithm to solve the Bayesian multi-target localization problem with dependent blocking is proposed and results show that when the DP blocking events are highly dependent, assuming them to be independent and having constant probability (as was done previously) resulted in poor detection performance, with false-alarms more likely to occur than detections.


Sunda AdityaSundar Aditya obtained his B. Tech and M. Tech degrees in electrical engineering from the Indian Institute of Technology, Madras, in 2011. He is currently a Ph.D. candidate at the Wireless Devices and Systems (WiDeS) lab at the University of Southern California (USC), where his research focuses on problems pertaining to multi-target localization and tracking as well as the design and performance analysis of localization networks using stochastic geometry. He is jointly advised by Prof. Andreas F. Molisch from USC and Prof. Harpreet S. Dhillon from Virginia Tech.




Date of the presentation: 01/ 27/ 2017

Speaker: Prof. Georgios B. Giannakis, ADC Chair in Wireless Telecommunications and McKnight Presidential Chair in ECE, University of Minnesota

Title: Inference and Learning over Large-Scale Social Networks


Social networks are pervasive and encompass interactions over online social media, human links in epidemic processes, terrorist cells, and collaborations among researchers. The value in understanding and predicting complex network behavior cannot be understated, thanks to the growing role of search engines, cyber warfare, online marketing, and social recommendation tools. Real-world social networks are fraught with unique challenges that limit the efficacy of contemporary tools. For example, such networks are big (billions of nodes), evolve over time, and are often not directly observable. Viewed through a statistical learning lens, many network analytics problems boil down to (non-) parametric regression and classification, dimensionality reduction, or clustering. Adopting this point of view, this talk will put forth novel learning approaches for network visualization, anomaly and community detection, prediction of network processes, and dynamic network inference. Key emphasis will be placed on parsimonious models exploiting sparsity, low rank, or low-dimensional manifolds, attributes that have been shown useful for complexity reduction. The merits of the novel schemes will be demonstrated on both simulated and real-world social networks.


Georgios B. Giannakis (Fellow’97) received his Diploma in Electrical Engr. from the Ntl. Tech. Univ. of Athens, Greece, 1981. From 1982 to 1986 he was with the Univ. of Southern California (USC), where he received his MSc. in Electrical Engineering, 1983, MSc. in Mathematics, 1986, and Ph.D. in Electrical Engr., 1986. He was with the University of Virginia from 1987 to 1998, and since 1999 he has been a professor with the Univ. of Minnesota, where he holds a Chair in Wireless Telecommunications, a University of Minnesota McKnight Presidential Chair in ECE, and serves as director of the Digital Technology Center. His general interests span the areas of communications, networking, and statistical signal processing – subjects on which he has published more than 400 journal papers, 680 conference papers, 25 book chapters, two edited books and two research monographs (h-index 119). Current research focuses on big data analytics, wireless cognitive radios, network science with applications to social, brain, and power networks with renewables. He is the (co-) inventor of 25 patents issued, and the (co-) recipient of 8 best paper awards from the IEEE Signal Processing (SP) and Communications Societies, including the G. Marconi Prize Paper Award in Wireless Communications. He also received Technical Achievement Awards from the SP Society (2000), from EURASIP (2005), a Young Faculty Teaching Award, the G. W. Taylor Award for Distinguished Research from the University of Minnesota, and the IEEE Fourier Technical Field Award (2015). He is a Fellow of EURASIP, and has served the IEEE in a number of posts including that of a Distinguished Lecturer for the IEEE-SP Society.




Fall, 2016

Date: November 18, 2016

Title: Resource Allocation in Wireless Networks Under Uncertainties: A Stochastic Optimization Framework

Speaker: Dr. Mohammad J. Abdel-Rahman

Abstract: Emerging wireless networks operate using dynamic and uncertain resources that render them susceptible to severe performance degradation. Managing stochastic resources in such networks while ensuring a certain level of network performance is challenging. In this talk, I introduce stochastic optimization as a powerful tool to handle resource allocation in uncertain networks, discuss various approaches to modeling uncertainty, and explain different feasibility and optimality approaches under uncertainty. I will talk about both static and adaptive stochastic optimization approaches. In particular, I focus on (i) chance-constrained, (ii) simple recourse, and (iii) multi-stage stochastic optimization approaches. Throughout the talk, I will illustrate how to use some of the aforementioned stochastic optimization techniques to formulate example resource allocation problems in emerging wireless networks. Specifically, I will consider: (i) Joint channel and base station allocation in opportunistic LTE networks, (ii) orchestrating a robust virtual LTE-U network from hybrid half/full-duplex Wi-Fi APs, (iii) adaptive link scheduling and beam-steering in millimeter-wave networks, (iv) adaptive controller assignment in software-defined cellular networks, and (v) stochastic resource allocation with slicing in virtualized wireless access networks.


Dr. Abdel-RahmanMohammad J. Abdel-Rahman is currently a Research Associate in the Department of Electrical and Computer Engineering at Virginia Polytechnic Institute and State University. He received his PhD degree from the Electrical and Computer Engineering Department at the University of Arizona in 2014. He is the recipient of the College of Engineering 2014 Outstanding Graduate Student Award. He received his MSc degree from the Electrical Engineering Department at Jordan University of Science and Technology, Jordan, in 2010, and his BSc degree from the Communication Engineering Department at Yarmouk University, Jordan, in 2008. Dr. Abdel-Rahman’s research is in the broad area of wireless communications and networking, with particular emphasis on resource management, adaptive protocols, and security issues. He serves as a reviewer for several international conferences and journals. He is a member of the IEEE.



Date: November 11, 2016

Title: Spectrum Sharing Test and Demonstration: LTE- DoD Coexistence

Speaker: Mike Smith


On November 13, 2014, the Federal Communications Commission (FCC) initiated the Advanced Wireless Services (AWS) - 3 Auction (“Auction 97”), to competitive bidding. Auction 97 has provided new wireless service licenses in the 1695-1710 MHz (Uplink), 1755-1780 MHz (Uplink), and 2155-2180 MHz (paired downlink) bands for AWS-3. Auction 97 generated more than $42B in revenue. As a result, many DoD communications systems are required to relocate out of these spectrum bands in accordance with established DoD Transition Plans over the next 10 years.

As part of the DoD Transition Plan for AWS-3, the Defense Information Systems Agency (DISA) Defense Spectrum Organization (DSO) proposed the development of a Spectrum Sharing Test & Demonstration (SST&D) program. The current objectives of the SST&D Program include:

· Facilitating expedited and expanded entry of commercial wireless network deployments into the 1755-1780 MHz band.

· Identify, demonstrate, and operationalize interference mitigation techniques consistent with commercial Long Term Evolution (LTE) standards that support increased sharing between LTE and incumbent DoD systems

· Prototype and demonstrate advanced sharing concepts for long-term sharing in the 1755-1780 MHz band.

To meet these objectives, the SSTD program has been partitioned into activities which address all aspects of the signal interference scenario between these to-be-deployed wireless networks and to-be-displaced DoD transceivers.

This presentation provides a description of the LTE Characterization activity which is focused on understanding how LTE network operations (today and in the future) establish uplink emissions under a variety of operating conditions (e.g., traffic loading; ISD; power control algorithms; resource allocation algorithms; etc.) and in the presence of interfering signals (e.g. DoD SATOPS). To do this, the team is developing LTE network models that can enhance spectrum coexistence assessments and performing LTE network testing and measurements providing real network operation statistics to inform these modeling efforts.


Mike SmithMr. Smith is a Senior Systems Engineer for the Virginia Tech Applied Research Corporation (VT-ARC). Mr. Smith is an experienced Systems Engineer with functional expertise in Wireless Networking, Communication Systems, RF Design, Semiconductor Manufacturing, and Satellite Communications. He has demonstrated experience in planning, analysis, design, and delivery of communications systems for the DoD and Commercial Service Providers.

Prior to joining VT-ARC, Mr. Smith was a Systems Engineer at Harris Corporations Electronic Systems focused on developing and managing Software Defined Tactical Radios and Power Amplifiers for DoD and foreign military customers. Earlier in his 22-year Harris career, Mike focused on business development for Harris commercial satellite systems, serving as Lead Systems Engineer on several payload programs and proposals emphasizing the application of phased array antenna systems. Earlier in his career Mr. Smith also successfully led the development and implementation of semiconductor manufacturing yield management methodologies at Filtronic Solid State and Zeevo, Inc.

Mr. Smith received a B.S. degree in Electrical Engineering from Virginia Tech in 1985.



Date: November 4, 2016

Title: ETSI’s RRS Solution for MD Reconfiguration: Standard Architecture & Interfaces.

Speaker: Dr. Seungwon Choi from Hanyang University, South Korea


This talk summarizes the standardization activities in TC(Technical Committee) RRS(Reconfigurable Radio System) of ETSI(European Telecommunications Standard Institute) for determining a standard architecture for reconfigurable mobile device and related interfaces. Firstly, we briefly introduce the standardization procedure within ETSI and documents that have been published within Working Group 2 of TC-RRS of ETSI. Then, MD reconfiguration class is discussed in order to summarize how the SDR technologies for MD are evolved in terms of the degree of reconfigurability. Standard architecture of reconfigurable MD is introduced showing each component of radio computer needed for the radio reconfiguration. Then we consider three cases of distributing the radio application code, i.e., in the form of executable code, source code and Intermediate Representation. Then, operational structure of unified radio application are shown for the three cases. Finally, we introduce the standard interfaces defined for the standard architecture of the reconfigurable MD, i.e., multiradio interface, reconfigurable RF interface, unified radio application interface and radio programming interface. The concept of radio virtual machine is also introduced of which the objective is to resolve the problem of portability between the radio application code and hardware platform whose granularity might vary depending upon different manufacturers.



Bio: Dr. Seungwon Choi received the BS degree from Hanyang University, Seoul, Korea, and the M.S. degree from Seoul National University, Korea, in 1980 and 1982, respectively, both in electronics engineering, the MS degree (computer engineering) in 1985, and the PhD degree (electrical engineering), in 1988, both from Syracuse University, Syracuse, NY, USA. Between 1988 and 1989, he served as an assistant professor in Syracuse University. He Joined Hanyang University as an assistant professor in 1992 and he is now a full professor in the Department of Electrical and Computer Engineering of Hanyang University. He was the director of HY-SDR Research Center between 2002 and 2010 during which he actively participated WINNF (Wireless Innovation Forum) as a board of director. Currently, he is the director of HY-MC Research Center in which 13 professors and 98 graduate students are engaged with researches on mobile communication-related fields including reconfigurable communication systems. Since 2011, Dr. Choi has been actively participating the standardization activities in ETSI (European Telecommunications Standards Ins.) and now he is serving as the chairman of WG2 of TC-RRS of ETSI. His research interests include digital communications and adaptive signal processing with a recent focus on the implementation of Software Defined Radio systems for both base station and mobile devices. He has published about 90 international journal papers and held nearly 50 patents.

Date: Friday, October 7, 2016

Title: Automatic Generation of Efficient Parallel Streaming Hardware.

Speaker: Thaddeus Koehn


Digital signal processing systems demand higher computational performance and more operations per second than ever before, and this trend is not expected to end any time soon. Processing architectures must adapt in order to meet these demands. The two techniques most prevalent for achieving throughput constraints are parallel processing and stream processing. By combining these techniques, significant throughput improvement have been achieved. These preliminary results apply to specific applications, and general tools for automation are in their infancy. In this presentation techniques are developed to automatically generate efficient parallel streaming hardware architectures.


Bio: Thaddeus Koehn is a Ph.D candidate at Virginia Tech as well as a Senior Research Associate at the Virginia Tech Ted and Karyn Hume Center. His advisor is Prof. Peter Athanas. He received his B.S. from University of Rhode Island in 2006, and his M.S. E.E. from University of Illinois in 2009. His research interests include digital signal processing, high performance computing, computer architecture and computer-aided design.

Date: Friday, September 23, 2016

Title: Cache Aided Networks: From Practice to Theory?

Speaker: Avik Sengupta


In this talk we will focus on recent advances in cache-aided networks which has been the topic of a vast body of recent research both in academia and industry. Cache-aided systems aim to exploit available network resources to increase efficiency in content distribution by effectively converting "memory into bandwidth". We will focus on the applications of reinforcement learning techniques and the role of optimization in caching. A number of practical system settings will be studied, which gives rise to the need for deeper understanding of theoretical limits of caching and delivery methods. To this end, we will reflect on an information theoretic perspective of caching and cache-aided interference management, highlighting recent interesting results in this paradigm.

Bio: Avik Sengupta is a Ph.D. candidate in ECE at Virginia Tech, working with Wireless@VT and the Hume Center. He received the B.Tech degree in Electronics and Communication Engineering from West Bengal University of Technology, India, in 2010 and the M.S. degree in Electrical and Computer Engineering from Kansas State University in 2012. His research interests include wireless communication systems with an emphasis on caching and content distribution in wireless networks. He has interned with Blackberry, Huawei Research and Qualcomm working on LTE PHY-layer systems design. Avik's advisor is Dr. Charles Clancy.



Date: Friday, September 16, 2016

Title: An OFDM Scheme for 3.5 GHz LTE

Speaker: Seungmo Kim


In April 2015, the FCC voted to approve rules for the new Citizens Broadband Radio Service (CBRS) service, incorporating smaller exclusion zones and setting the stage for commercial deployment in 3,550–3,700 MHz (the 3.5 GHz band). Primary radio systems currently operating in this band are pulse radars. When sharing spectrum between a radar and a digital communications system, a problem arises: it is more likely that the communications system experiences higher interference, due to very high transmit power of a radar compared to a digital communications system. In this talk, we discuss an OFDM scheme that is more robust against interference from pulsed radar. Moreover, applying the 3.5 GHz LTE rule that has recently been finalized, we also discuss the impact of imperfect sensing by Environment Sensing Capability (ESC), the spectrum sensing capability in the 3.5 GHz LTE spectrum sharing architecture.


Mo KimSeungmo Kim received his B.S. and M.S. from the Korea Advanced Institute of Science and Technology (KAIST) in 2006 and 2008, respectively. He worked for Samsung in 2008 through 2012 on development of embedded software of MAC and NWK protocol stack for IEEE 802.15.4 and ZigBee. He is currently a Ph.D. candidate in the Dept. of Electrical and Computer Engineering at Virginia Tech. His research interests include spectrum sharing, 3GPP, 5G, and millimeter wave bands. Mo's advisor is Dr. Carl Dietrich.






SPRING, 2016


Date: Friday, April 29, 2016

Title: Information theoretic and control theoretic problems motivated by energy harvesting communications

Speaker: Venkat Anantharam, EECS, University of California, Berkeley

The seminar this week is merged with the Bradley Distinguished Lecture. The location will be at Goodwin Hall, Room 190 (Quillen Family Auditorium) at 4 p.m. For more information please visit


The Internet of Things is expected to lead to an increase by orders of magnitude in the number of networked devices. Many of these devices, such as sensors, are expected to be energy limited.Partly to avoid constant maintenance of these devices and also because of its increasing technological feasibility, there is a growing interest in the development of energy harvesting technologies, where the energy to power a device or to augment its existing capabilites is derived from the environment from solar, mechanical, or other means. An energy harvesting device typically will have a battery of limited capacity, which can store harvested energy to smooth out the fluctutations in the energy harvesting process.

The introduction of energy harvesting aspects in devices poses many interesting new challenges for the analysis and design of communication and control systems. Depending on the time scale of variations in energy harvesting relative to the time scale of the dynamics of the systems being monitored, both information theoretic and control theoretic models are of interest.

As an example, the study of the Shannon capacity of communication with an energy harvesting transmitter requires an understanding of how to design transmission codebooks subject to the requirement that each transmitted codeword meets the available energy budget at every moment during the course of its transmission. We will discuss our recent results on problems of this flavor.

From a mathematical point of view, the problem is one of high dimensional geometry, where the high dimensional unit balls of traditional Shannon theory are replaced by certain high dimensional polytopes defined by the real time nature of the constraints on the available energy. A remarkable parallel between convex sets in high dimensions and large deviations theory emerges in this regime. This is joint work with Varun Jog.

At the other extreme of time scales, packet drop models are more appropriate to study the overall system design. We will discuss how the theory of estimation of state over packet drop channels needs to be modified when the sensing infrastructure that communicates its observations to a remote estimator is of an energy harvesting type. This is joint work with Omur Ozel.


Venkat Anantharam is on the faculty of the EECS Department at the University of California, Berkeley. His research interests include coding theory, communication networks, information theory,and stochastic control.

He received the Philips India Medal and the President of India Gold Medal from IIT Madras in 1980 and an NSF Presidential Young Investigator award in 1988.He is a corecipient of the 1998 Prize Paper Award of the IEEE Information Theory Society, and a corecipient of the 2000 Stephen O. Rice Prize Paper Award of the IEEE Communications Theory Society. He received the Distinguished Alumnus Award from IIT Madras in 2008.


Student Panel On 5G This Friday, APRIL 22!

Submit Your 5G Questions for our Panelists

About the Student Seminar

5G wireless is a wide research area, as some of the goals of 5G are to simultaneously increase network speeds, connection density and spectral efficiency while also significantly reducing latency and energy consumption of wireless devices. 5G wireless communications are also expected to occur throughout the spectrum at frequencies from 1 to 100 GHz.

At the panel, you’ll have the opportunity to hear your fellow student’s thoughts on the directions for 5G technology and contribute your questions and thoughts to the discussion, too. To start the conversation, please take a moment to submit a question you have about 5G technologies to the panel. 

Student Panelists


Avik Sengupta

Avik Sengupta is a Ph.D. candidate in the Department of Electrical and Computer Engineering at Virginia Tech, working with Wireless@VT and the Hume Center for National Security and Technology. He received the B.Tech degree in Electronics and Communication Engineering from West Bengal University of Technology, Kolkata, India, in 2010 and the M.S. degree in Electrical and Computer Engineering from Kansas State University, Manhattan KS, USA in 2012. His research interests include design and information theoretic modeling of wireless communication systems with an emphasis on content distribution and caching in 5G wireless networks. He was a research intern with the Advanced Technology Group at Blackberry and with the Wireless Access Lab at Futurewei Technologies (Huawei R&D).

Daniel Jakubisin

Daniel received his BSEE from UNC Charlotte in 2006 and his MSEE from Virginia Tech in 2012. He is currently a PhD candidate under the supervision of Dr. Michael Buehrer within the Wireless @ Virginia Tech research group. His research is in applying iterative probabilistic processing to the design of communications receivers with a focus on multi-user detection and co-channel interference. His interests in 5G include the PHY/MAC developments taking place and their impact on receiver design.

Priyabrata Parida

Priyabrata joined Wireless@VT as a PhD student during Fall 2015 after graduating with MS degree in Telecommunication from Indian Institute of Technology, Kharagpur, India. He conducts his research activities under the supervision of Dr. Harpreet Singh Dhillon. His research interest includes MIMO, stochastic geometry, and optimization of wireless communication systems. In the past, he has worked as an Assistant Manager as a part of 3G network operation and maintenance team for Ideal Cellular, a leading telecom provider in India.

Abid Ullah

Abid is currently working toward the Ph.D. degree in electrical engineering at Virginia Polytechnic Institute and State University. His research interests include multi-antenna resource allocation for spectrum management, and he is advised by Dr. Jeffrey H. Reed.


Event Details

Date: Friday, 22 April 2016

Location: Goodwin Hall, Rm. 155

Time: 2:45 pm - 3:45 pm


Date: April 8, 2016

The seminar this week is merged with the Bradley Distinguished Lecture. The location will be at Goodwin Hall, Room 190 (Quillen Family Auditorium) at 4 p.m. For more information please visit


Speaker: Dr. Aylin Yener

Title: Towards Design Principles of Next Generation Networked Systems: Information Security and Energy Sustainability

Next generation networked systems are expected to have several salient features that require new paradigms in related systems research areas. These systems are expected to contain a large number of connected nodes of various heterogeneous capabilities. They are expected to be dynamic, self-organizing networks that operate in the wireless medium. Operating in a vulnerable medium with many others of various trust levels, they call for new security measures, that are low overhead and scalable, yet powerful in their guarantees. Similarly, they are expected to be energy self-sufficient with extended life times. In this talk, we will focus on two system-level directions that are promising in each of these concerns: physical-layer security and energy harvesting communication networks.

Physical layer security aims to provide secure communication guarantees built in to the network design at its foundation. Having its roots in existence results in information theory and incubated in the information theory community for close to a decade, wireless physical layer security research has grown to be a vibrant area in communications, information theory, coding theory and signal processing for communications. In this talk, we will provide an overview of our results in physical layer security in the last decade, and the resulting design insights. These include insights related to inducing judicious interference for confidentiality, i.e., cooperative jamming, structured signaling, multi-antenna signaling strategies and merits of bidirectional transmission. We will then overview some of the more recent advancements towards relaxing some of the idealized assumptions in earlier problem constructs, notably those related to the channel state information, as well as research efforts towards getting close to practical system design.

Energy harvesting communications offers the possibility of perpetual network operation without adverse effects on the environment and will lead to the green future of wireless. Energy harvesting brings new considerations, most notably, intermittency of available energy and its temporary storage. Communication and network theoretic design of such networks is an emerging area. In this talk, we will present an overview of our results in this emerging area, and the ensuing algorithmic design insights. The focus will be on transmission scheduling policies that amortize the energy expenditure for optimum system operation, highlighting the trade-offs arising from practical considerations in these systems, notably the role of the size and the storage efficiency of the battery. We will also briefly mention the new information theoretic capacity problems that arise in this setting.

Time permitting, we will present an additional important direction relevant in these cyber-physical networked system, namely the role of humans and their social interactions.

Bio:  Dr. YenerAylin Yener is a professor of Electrical Engineering at The Pennsylvania State University, University Park, PA since 2010, where she joined the faculty as an assistant professor in 2002. During the academic year 2008-2009, she was a Visiting Associate Professor with the Department of Electrical Engineering, Stanford University, CA. Her research interests are in information theory, communication theory and network science with recent emphasis on green communications, information security and networked systems.  She received the NSF CAREER award in 2003, the best paper award in Communication Theory in the IEEE International Conference on Communications in 2010, the Penn State Engineering Alumni Society (PSEAS) Outstanding Research Award in 2010, the IEEE Marconi Prize paper award in 2014, the PSEAS Premier Research Award in 2014, and the Leonard A. Doggett Award for Outstanding Writing in Electrical Engineering at Penn State in 2014.  She is a fellow of the IEEE.

Dr. Yener is an elected member of the board of governors of the IEEE Information Theory Society for the term 2015-2017. Previously, she served on the same board of governors as the treasurer (2012-2014). She served as the student committee chair for the IEEE Information Theory Society 2007-2011, and was the co-founder of the Annual School of Information Theory in North America co-organizing the school in 2008, 2009 and 2010.  For the IEEE Communications society, she was a technical (co)-chair for various symposia/tracks at IEEE ICC, PIMRC, VTC, WCNC and Asilomar (2005-2014). She served as an editor for IEEE Transactions on Communications (2009-2012), an editor and an editorial advisory board member for IEEE Transactions on Wireless Communications (2001-2012), a guest editor for IEEE Transactions on Information Forensics and Security (2011) and a guest editor for IEEE Journal on Selected Areas in Communications (2015).  Presently, she serves as an editor for the IEEE Transactions on Mobile Computing. Additionally, she is a senior editor for the IEEE Journal on Selected Areas in Communications.

The wireless seminar series is planning to host a special student question and answer forum about 5G technologies and directions on Friday, 15 April. We are actively looking for student panelists to discuss perspectives on 5G topics.

A few example topics are below, and you can submit more 5G topics via the nomination form:

5G Use Cases

•Enhanced mobile broadband

•Massive machine to machine (M2M) communications

•Ultra reliable and low latency communications

Potential 5G Performance Goals

•10x data rate •3x Spectral efficiency

•~1.5x Mobility Velocity

•10x Latency Improvement

•10x connection density

•100x network energy efficiency

•100x Area traffic capacity

•20x peak data rate

We will be accepting nominations until Friday, 1 April. Please take a moment to consider nominating a student (self nominations are welcomed) to talk about 5G:


No seminar is scheduled for Friday, March 4. Have a safe and relaxing Spring Break!


Every Friday from 2:45 PM - 3:45 PM in Goodwin Hall, Room 155

Date: February 26, 2016

Title: Moon Bounce: Hokies go to the Moon Without Leaving Blacksburg

Speaker: Dr. Dennis Sweeney


Moon Bounce or Earth-Moon-Earth (EME) communications uses the moon as a passive reflector. A radio signal goes out 400,000 km, bounces off the moon, and returns 400,000 km. The round trip takes about 2.5 seconds. EME is an interesting footnote in the history of satellite communications and it has been taken up as a challenge by the amateur radio community. It has has been done on every amateur band from 28 MHz through 47 GHz. There is a current effort to extend this to 76 GHz.

EME is a major engineering challenge requiring high power transmitters, large antennas, and ultra low noise receivers. It has been described as the amateur radio equivalent of climbing Mt. Everest. Every 0.1 dB counts! Advanced DSP is being used to permit EME with smaller antennas and lower powered transmitters and to mitigate the effects of libration fading and Doppler shift.

This presentation will look at some of the history of EME and the engineering challenges that accompany it. It will look at the hardware currently under development to do EME at 10 GHz.


Dr. SweeneyDr. Sweeney is currently Professor of Practice and the Director of Instructional Labs (DIL) for the Electrical and Computer Engineering (ECE) Department. He is responsible for maintaining the teaching labs and managing the undergraduate lab program. Dr. Sweeney is no stranger to VA Tech. He got his undergraduate EE degree at VA Tech in 1971 and returned in the 1980's to earn his PhD. He worked for the VA Tech Satellite Communications Group managed by Dr. Pratt, Bostian, and Stutzman. Upon completing his PhD, Dr. Sweeney held an instructor appointment in the ECE department. He then went to the Jet Propulsion Laboratory where he worked on GPS applications. Returning in 1994, he joined Dr. Bostian in the Center for Wireless Telecommunications (CWT). After 11 years with CWT, he went to the Aerospace Corporation in northern Virginia. There he worked on a number of space related projects. The last project was a flight mission launched in January of 2011 just before he returned (again!) to VA Tech as the DIL.

Dr. Sweeney is an avid builder of microwave hardware and he is an active amateur radio operator. His interests are in microwave radio technology and teaching students how to build things. He and his wife Betsy, who is an equally avid quilter, live here in Blacksburg.


Date: February 19, 2016

Title: Second EARS Workshop: An Overview and Grand Challenge Forum

Speaker: Thaddeus Czauski


Wireless connectivity is fueling the growth of Internet of Things (IoT) devices, applications and services. By one estimate there will be 40 billion active wireless devices in the world by 2020. Supporting all of these wireless devices presents an important challenge: How to ensure that ample spectrum resources are available for each of these wireless devices?

To address this paramount issue academic researchers, industry experts, and policy makers met at the Second Enhancing Access to the Radio Spectrum (EARS) workshop to discuss open challenges and promising research that will facilitate spectrum sharing between wireless devices. The EARS workshop resulted in the formation of several grand challenges that will guide and shape the future of wireless devices and applications. This week’s Wireless Seminar will be a forum discussion about spectrum sharing including a brief overview of findings from the Second EARS workshop, and an opportunity for the audience to choose one or two grand challenges to discuss.


Thaddeus CzauskiThaddeus Czauski received the B.S. degree in Computer Engineering and Certificate in Nuclear Engineering from the University of Pitsburgh, and the M.S. degree in Computer Engineering from Virginia Tech. He has previously held positions at Northrop Grumman, General Electric, and the Sandia National Laboratories. He is currently pursuing his Ph.D. degree under the mentorship of Dr. Jeffrey Reed in the Wireless @ VT research center. His current research includes spectrum sharing architectures, low-latency communications. cyber-physical systems, and mobile cloud computing. Additionally, his interests and background include software engineering; user-experience assessment and design; privacy, security, and trust in computing; context aware computing; software patterns and architectures; mobile and wireless healthcare; and mobile security.

FIRST SEMINAR THIS SPRING - February 12, 2016, Dr. Jeffrey Reed

Prospective of Current and Future Wireless Research: Technical Needs and Policy Challenges

This presentation will overview a few of the current research initiatives from Prof. Reed’s students and anticipated future research directions. The justification for current and future research directions, both from the prospective of technological needs and policy directions, will be addressed in the context of anticipated directions of the wireless industry.


Dr. ReedDr. Jeffrey H. Reed is the Willis G. Worcester Professor in the Bradley Department of Electrical and Computer Engineering at Virginia Tech. He currently serves as Founding Director of Wireless@Virginia Tech, one of the largest and most comprehensive university wireless research groups in the US which he founding in 2006 and served as its first director. In 2010, he founded the Ted and Karyn Hume Center for National Security and Technology and served as its Interim Director. Dr. Reed is co-founder of Cognitive Radio Technologies (CRT), a company that is commercializing of the cognitive radio technologies produced for military applications, Federated Wireless, a company that is developing spectrum sharing technologies; and for PFP Cybersecurity, a company that specializes in security for embedded systems, including Android platforms. He has also served as a consultant for approximately thirty organizations, covering topics such as merger evaluation, network neutrality, and band planning. Dr. Reed served on the President’s Council of Advisor in Science and Technology (PCAST) Advisory Group on how to transition federal spectrum for commercial economic benefits. In 2014, Dr. Reed was selected to be a member of CSMAC, the advisory group on spectrum issues for the US Department of Commerce. In 2014, Dr. Reed served as co-general chair for the IEEE Dynamic Spectrum Access Network (DySPAN) conference. In the fall of 2015, Dr. Reed testified before Congress on Improving Federal Spectrum Systems. You can read his testimony here!