SPAWC 2015 - The 16th International Workshop on Signal Processing Advances in Wireless Communications, June 28 - July 1, Stockholm.

Tutorials

The workshop featured 3 parallel tutorials. The tutorials were 3 hours in length, with a half hour break in the middle, and were included in the workshop registration fees for all participants.


Millimeter Wave Wireless Communications

Presenter: Robert W. Heath Jr. (The University of Texas at Austin, USA)

Slides

View slides

The PDF file is password protected. See the Tutorials page in the USB proceedings for the password.

Summary

Communication at millimeter wave (mmWave) frequencies is defining a new era of wireless communication. The mmWave band relieves spectral gridlock at lower frequencies by offering much higher bandwidth communication channels than presently used in commercial wireless systems. The next generation of wireless local area networks is exploiting the mmWave unlicensed band at 60 GHz to provide multi-gigabit-per-second data rates. There is also growing interest in using mmWave licensed spectrum for 5G cellular systems at other mmWave frequencies. The potential for mmWave is immense.

Signal processing is critical for enabling the next generation of mmWave communication. Because of the wide bandwidth, overall complexity and mixed signal power consumption are significant concerns. This motivates developing MIMO signal processing techniques for example that operate with few high resolution or many low-resolution analog-to-digital converters. The propagation channel characteristics lead to sparsity in the channel, which can be exploited in channel estimation, signal detection, and equalization. System analysis of mmWave wireless systems is more complicated due to the use of compact antennas, sensitivity to blockages, and distance dependent propagation effects. Because of the higher carrier frequencies, supporting mobility becomes a significant challenge requirement the development of time-varying signal processing techniques such as rapid beam adaptation.

This tutorial will provide an overview of mmWave wireless communication from a signal processing perspective. Note that this will not be a review of contents from the author’s book, which has a lot of background on propagation and circuits. Rather it will emphasize more specific lines of research inquiry of interest to signal processing researchers especially those working on MIMO communication and array processing.

Outline

Time Title Topics
15 min Introduction
  • Motivation for communication at millimeter wave frequencies
  • The importance of antenna arrays
  • Applications of millimeter wave to WPAN, WLAN, cellular communication, and vehicular
20 min Channel propagation
  • Large-scale path loss
  • Small scale fading
  • Channel models
  • Sparsity in the channel
10 min Hardware constraints
  • Typical transceiver structure
  • Power consumption of different components
  • RF phase shifters
  • ADC resolution
  • RF impairments
15 min Modulation considerations
  • Single carrier with cyclic prefix
  • Single carrier with null prefix
  • OFDM with cyclic prefix
  • OFDM with null prefix
20 min Analog beamforming
  • Typical array structures
  • Beam training
  • Hierarchical approaches
30 min Hybrid precoding
  • Combining analog and digital precoding and combining
  • Approximating the ideal precoder with a hybrid solution
  • Extensions to multi-user processing
10 min Low resolution ADCs
  • Capacity upper and lower bounds
20 min Channel estimation
  • The sparse channel model
  • Compressive estimation of the mmwave channel
  • Channel estimation for hybrid precoding
  • Channel estimation for 1 bit ADC architectures
15 min IEEE 802.11ad
  • Review of key components of the MAC and PHY of this commercial mmWave standard
15 min mmWave for 5G cellular
  • Application of mmWave for 5G cellular, including network architectures
  • Coverage and rate analysis
10 min Current directions and open problems
  • Review of different research directions and open problems in these different areas

Biography

Robert W. Heath Jr.Robert W. Heath Jr. (IEEE Fellow) received the B.S. and M.S. degrees from the University of Virginia, Charlottesville, VA, in 1996 and 1997 respectively, and the Ph.D. from Stanford University, Stanford, CA, in 2002, all in electrical engineering. From 1998 to 2001, he was a Senior Member of the Technical Staff then a Senior Consultant at Iospan Wireless Inc, San Jose, CA where he worked on the design and implementation of the physical and link layers of the first commercial MIMO-OFDM communication system. Since January 2002, he has been with the Department of Electrical and Computer Engineering at The University of Texas at Austin where he is a Cullen Trust for Higher Education Endowed Professor, and is a Member of the Wireless Networking and Communications Group. He is also President and CEO of MIMO Wireless Inc. and Chief Innovation Officer at Kuma Signals LLC. His research interests include several aspects of wireless communication and signal processing: limited feedback techniques, multihop networking, multiuser and multicell MIMO, interference alignment, adaptive video transmission, manifold signal processing, and millimeter wave communication techniques. He is a co-author of the book “Millimeter Wave Wireless Communications” published by Prentice Hall in 2014.

Dr. Heath has been an Editor for the IEEE Transactions on Communication, an Associate Editor for the IEEE Transactions on Vehicular Technology, lead guest editor for an IEEE Journal on Selected Areas in Communications special issue on limited feedback communication, lead guest editor for an IEEE Journal on Selected Topics in Signal Processing special issue on Heterogeneous Networks, and lead guest editor for an IEEE Journal on Selected Topics in Signal Processing special issue on Millimeter Wave Wireless Communication. He currently serves on the steering committee for the IEEE Transactions on Wireless Communications. He was a member of the Signal Processing for Communications Technical Committee in the IEEE Signal Processing Society and is a former Chair of the IEEE COMSOC Communications Technical Theory Committee. He was a technical co-chair for the 2007 Fall Vehicular Technology Conference, general chair of the 2008 Communication Theory Workshop, general co-chair, technical co-chair and co-organizer of the 2009 IEEE Signal Processing for Wireless Communications Workshop, local co-organizer for the 2009 IEEE CAMSAP Conference, technical co-chair for the 2010 IEEE International Symposium on Information Theory, the technical chair for the 2011 Asilomar Conference on Signals, Systems, and Computers, general chair for the 2013 Asilomar Conference on Signals, Systems, and Computers, founding general co-chair for the 2013 IEEE GlobalSIP conference, and was technical co-chair for the 2014 IEEE GLOBECOM conference.

Dr. Heath was a co-author of best student paper awards at IEEE VTC 2006 Spring, WPMC 2006, IEEE GLOBECOM 2006, IEEE VTC 2007 Spring, and IEEE RWS 2009, as well as co-recipient of the Grand Prize in the 2008 WinTech WinCool Demo Contest. He was co-recipient of the 2010 and 2013 EURASIP Journal on Wireless Communications and Networking best paper awards, the 2012 Signal Processing Magazine best paper award, a 2013 Signal Processing Society best paper award, the 2014 EURASIP Journal on Advances in Signal Processing best paper award, and the 2014 Journal of Communications and Networks best paper award. He was a 2003 Frontiers in Education New Faculty Fellow. He is also a licensed Amateur Radio Operator and is a registered Professional Engineer in Texas.

Massive MIMO for 5G: Fundamentals and Recent Theory

Presenters: Erik G. Larsson (Linköping University, Sweden), and Emil Björnson (Linköping University, Sweden)

Slides

View slides (part 1) View slides (part 2)

The PDF files are password protected. See the Tutorials page in the USB proceedings for the password.

Summary

The next generation wireless networks need to accommodate 1000x more data traffic than contemporary networks. Since the spectrum is scarce in the bands suitable for coverage, the main improvements need to come from spatial reuse of spectrum; many concurrent transmissions per area unit. This is made possible by the massive MIMO technology, where the access points are equipped with hundreds of antennas. These antennas are phase-synchronized and can thus radiate the data signals to multiple users such that each signal only adds up coherently at its intended user.

Over the last the couple of years, massive MIMO has gone from being a theoretical concept to becoming one of the most promising ingredients of the emerging 5G technology. This is because it provides a way to improve the area spectral efficiency (bit/s/Hz/area) under realistic conditions, by upgrading existing base stations. In other words, massive MIMO is a commercially attractive solution since 100x higher efficiency is possible without installing 100x more base stations.

This tutorial introduces the basic communication theory and motivation behind massive MIMO, as well as recent theoretical results on power control, energy efficiency, and impact of hardware impairments.

Outline

Part 1 (First 1.5 hours given by Erik G. Larsson)
Title Topics
Motivation and Case Studies
  • Expectations on 5G networks
  • Basic idea and operation of Massive MIMO
  • Case studies and motivating examples
Models and Fundamental Assumptions
  • Channel coherence time and bandwidth
  • Time division duplex (TDD) operation, reciprocity
  • Frame structure, pilots and payload
  • TDD versus FDD
Favorable Propagation
  • The concept of “favorable propagation”
  • Capacity bounds and the meaning of channel singular values
  • Case studies: Independent Rayleigh fading, and line-of-sight propagation
Single-Cell Operation
  • Uplink and downlink capacity with linear reception/precoding algorithms and estimated channels
  • The limiting factors of Massive MIMO: Channel coherency, available spatial degrees of freedom, uplink pilot quality
  • Power control as a linear programming problem
Multi-Cell Systems
  • Pilot reuse and pilot contamination
  • Single-cell vs. multi-cell: Similarities and differences
Part 2 (Second 1.5 hours given by Emil Björnson)
Title Topics
Uniform User Performance
  • Power-control policies
  • Pilot Reuse Patterns
  • How many users can be served?
Impact of Hardware Impairments
  • Modeling different types of impairments
  • New expressions and asymptotic results
  • Hardware Scaling Laws
Energy Efficiency
  • Power consumption model
  • Power scaling laws
  • Radiated vs. total power
  • Massive MIMO vs. small cells
Myths around Massive MIMO
  • What are the common misconceptions?

Biographies

Erik G. LarssonErik G. Larsson is Professor and Head of the Division for Communication Systems in the Department of Electrical Engineering (ISY) at Linköping University (LiU) in Linköping, Sweden. He joined LiU in September 2007. He has previously held positions at the Royal Institute of Technology (KTH) in Stockholm, University of Florida, George Washington University (USA), and Ericsson Research (Stockholm). He received his Ph.D. from Uppsala University in 2002.

His main professional interests are within the areas of wireless communications and signal processing. He has published some 100 journal papers on these topics, he is co-author of the textbook Space-Time Block Coding for Wireless Communications (Cambridge Univ. Press, 2003) and he holds 10 issued and many pending patents on wireless technology.

He is Associate Editor for the IEEE Transactions on Communications and he has previously been Associate Editor for several other IEEE journals. He serves as vice chair of the IEEE Signal Processing Society SPCOM technical committee in 2014. He also serves as chair of the steering committee for the IEEE Wireless Communications Letters in 2014-2015. He is active in conference organization, most recently as the General Chair of the Asilomar Conference on Signals, Systems and Computers 2015 (he was Technical Chair in 2012).

Emil BjörnsonEmil Björnson is Assistant Professor at the Division of Communication Systems at Linköping University, Sweden. He received the M.S. degree in Engineering Mathematics from Lund University, Sweden, in 2007. He received the Ph.D. degree in Telecommunications from the Department of Signal Processing at KTH Royal Institute of Technology, Stockholm, Sweden, in 2011. From 2012 to July 2014, he was a joint postdoc at the Alcatel-Lucent Chair on Flexible Radio, Supélec, Paris, France, and the Department of Signal Processing at KTH Royal Institute of Technology.

His research interests include multi-antenna cellular communications, massive MIMO techniques, radio resource allocation, green energy efficient systems, and network topology design. He is the first author of the book “Optimal Resource Allocation in Coordinated Multi-Cell Systems” published in Foundations and Trends in Communications and Information Theory, 2013. He is also dedicated to reproducible research and has made a large amount of simulation code publicly available.

Dr. Björnson has received 4 best paper awards (as first author or co-author) for novel research on optimization and design of multi-cell multi-antenna communications: IEEE WCNC 2014, IEEE SAM 2014, IEEE CAMSAP 2011, and WCSP 2009.

MIMO Broadcast and Interference Channels Towards 5G: Feedback, Performance and Topological Considerations

Presenters: Dirk Slock (EURECOM, France) and Petros Elia (EURECOM, France)

Slides

View slides (part 1) View slides (part 2)

The PDF files are password protected. See the Tutorials page in the USB proceedings for the password.

Summary

There is general consensus that any attempt to meaningfully improve the current performance of wireless communications, must surpass two fundamental challenges; the challenge of inventing communication schemes that properly manage interference, and the challenge of efficiently disseminating and utilizing feedback that may be delayed and imperfect. In the center of this effort, are revolutionary new algorithms that employ multiple antennas; an approach that continues to offer paradigm shifts in wireless communications and penetrate its standards.

The tutorial will provide an overview of the latest efforts to design such new schemes that manage to handle multiuser interference, as well as the latest efforts in understanding and meeting the fundamental learning-vs-using tradeoff; i.e., the latest efforts on finding ways to manage interference in the presence of reduced and delayed feedback. In the process, the tutorial will touch upon many new methods used over many different settings relating to multi-user (MU) MIMO in single and multiple cells, and hetnets. We elaborate on the design of spatial(-temporal) communication schemes, the concepts of signal space/scale Interference Alignment (IA), (Delayed) Channel State Information at the Transmitter (D-CSIT), channel training and feedback overhead, ergodic and retrospective IA, as well as summarize the latest results on topological interference networks, where we will consider the effect of imperfect CSI in topological interference networks where link strengths are affected by many topological factors.

This tutorial will focus on providing an insightful exposition of the latest exciting findings, as well as will place heavy emphasis on exposing new challenges and open questions on the role of feedback in modern and envisioned multiuser wireless communications, focusing on broadcast and interference channels.

In this exposition we will focus on new tools and methods on how to:

In the process we will seek answers to different practical questions such as:

Attendees will take away an understanding of the challenges associated with the joint design of transmit and receive beamformers, the possibilities of spatial multiplexing between interfering cells, the crucial importance of channel state information at the transmitter in multi-user and multi-cell configurations, the impact of delay, the tradeoff between performance and feedback precision, the extent of communication overhead in obtaining CSIT, the latest advances in interference alignment techniques, and the latest progress in capturing the role of network topology in communications. These hot topics are currently shaping the evolution of modern wireless and are expected to play a major role in 5G systems.

Outline

Part 1 (First 1.5 hours given by Petros Elia)
Title Topics
Basic exposition to the challenges of modern wireless communications
  • Brief introduction to different practical multiuser settings
Fundamentals of classical channels: the broadcast channel and the interference channel
  • Importance of DoF
  • Why feedback is important
  • Examples of importance of feedback in different settings
Learning the tools of the trade in feedback and precoding
  • Basics of multi-user MIMO
  • Basics on multi-cell MIMO
  • Single cell MU MIMO downlink
Fundamentals of feedback: the tradeoff between learning and using wireless networks
  • Delay and precision effects of feedback
  • Periodic feedback
  • Feedback with delays
  • CSIT and global CSIR
  • CSIT vs other feedback
  • Connections between IA and feedback
  • Role of antennas in reducing the need for feedback
Effects of network topology
Part 2 (Second 1.5 hours given by Dirk Slock)
Title Topics
Interference single cell: Broadcast Channel (BC)
  • Utility functions: SINR balancing, (weighted) sum rate (WSR)
  • BC with user selection: Dirty Paper Coding (DPC) vs beamforming (BF)
  • MIMO: role of receive (Rx) antennas
Interference multi-cell/HetNets: Interference Channel (IC)
  • Degrees of Freedom (DoF) and Interference Alignment (IA), IA feasibility
  • IA forms: asymptotic symbol extension, decomposition, ergodic, signal scale, MIMO
  • Multi-cell multi-user: Interfering Broadcast Channel (IBC)
  • Max Weighted Sum Rate (WSR), min Weighted Sum MSE (WSMSE), UL/DL duality
  • Difference of Convex functions approach, relation to max Signal-to-Leakage-plus-Noise Ratio (SLNR)
  • Deterministic Annealing to find global maximum
  • FIR IA for Asynchronous FIR Frequency-Selective IBC
Max WSR with Partial CSIT
  • CSIT: perfect, partial, Line-of-Sight (LoS), pathwise and non-Kronecker covariance
  • Expected WSR, Expected WSMSE, Massive MIMO limit, large MIMO asymptotics
CSIT acquisition and distributed designs
  • Distributed global CSIT acquisition, netDoF
  • Topology, rank reduced, decoupled Tx/Rx design, local CSIT
  • Massive MIMO, mmWave and covariance CSIT
  • Pathwise CSIT, BF as Dual UL pathwise LMMSE Rx
  • Distributed designs

Biographies

Dirk T. M. SlockDirk T. M. Slock received an engineering degree from the University of Gent, Belgium in 1982. In 1984 he was awarded a Fulbright scholarship for Stanford University, USA, where he received the MSEE, MS in Statistics, and PhD in EE in 1986, 1989 and 1989 resp. While at Stanford, he developed new fast recursive least-squares algorithms for adaptive filtering. In 1989-91, he was a researcher at the Philips Research Laboratory Belgium. In 1991, he joined EURECOM where he is now professor. At EURECOM, he teaches statistical signal processing (SSP) and signal processing techniques for wireless communications. He invented semi-blind channel estimation, the chip equalizer-correlator receiver used by 3G HSDPA mobile terminals, spatial multiplexing cyclic delay diversity (MIMO-CDD) now part of LTE, and his work led to the Single Antenna Interference Cancellation (SAIC) concept used in GSM terminals.

In 2000, he cofounded SigTone, a start-up developing music signal processing products. He has also been active as a consultant on xDSL, DVB-T and 3G systems. He is the (co)author of over 400 technical papers. He received one best journal paper award from IEEE-SP and one from EURASIP in 1992. He is the coauthor of two IEEE Globecom'98, one IEEE SIU'04 and one IEEE SPAWC'05 best student paper award, and a honorary mention (finalist in best student paper contest) at IEEE SSP'05, IWAENC'06 and IEEE Asilomar'06. He was an associate editor for the IEEE-SP Transactions in 1994-96 and the IEEE Signal Processing Letters and EURASIP Signal Processing in 2009-10. He is an editor for the EURASIP Journal on Advances in Signal Processing (JASP). He was a member of the IEEE-SPS Awards Board 2011-13 and currently of the EURASIP JWCN Awards Committee. He was the General Chair of the IEEE-SPS SPAWC'06 and IWAENC’14 workshops, and the upcoming EUSIPCO’15. He is a Fellow of the IEEE and of EURASIP.

Petros EliaPetros Elia received the B.Sc. degree from the Illinois Institute of Technology, and the M.Sc. and Ph.D. degrees in electrical engineering from the University of Southern California (USC), Los Angeles, in 2001 and 2006 respectively. Since February 2008 he has been an Assistant Professor with the Department of Mobile Communications at EURECOM in Sophia Antipolis, France.

His latest research deals with the role of feedback and complexity in multiuser communications, MIMO, cooperative and multiple access protocols and transceivers, complexity of communication, as well as with isolation and connectivity in dense networks, queueing theory and cross-layer design, coding theory, information theoretic limits in cooperative communications, and surveillance networks. He is a Fulbright scholar, the co-recipient of the SPAWC-2011 best student paper award on the topic of reduced complexity bidirectional communication with limited feedback, and of the NEWCOM++ distinguished achievement award 2008-2011 for a sequence of publications on the topic of reduced complexity multimode communications in the presence of little or no feedback.

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