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


The workshop featured five plenaries.

5G for the Networked Society

Speaker: Sara Mazur (Ericsson, Sweden)


The digitalization and mobility provided by ICT are key enablers for the transformation of industries and society. It is essential to provide efficient and highly capable solutions for the connectivity requirements that we anticipate in the coming years. The development of the 5G concept is done in parallel with design of test beds and the key technology components are identified.


Sara MazurSara Mazur is Vice President and Head of Research at Ericsson.

Prior to taking up this position, Mazur was Head of System Management within Ericsson's Business Unit Networks, focusing on unit-wide technology and research coordination and strategic management of technologies, a post she held since 2007. Mazur has worked throughout her career on advanced technology to strengthen Ericsson's technical excellence. She started at Ericsson Research in 1995 and has since held many management positions in the group that have kept her very close to the development of the telecommunications industry.

Mazur holds a Master's degree in science and a Ph.D. in electrical engineering from the KTH Royal Institute of Technology in Sweden. She is also an appointed Associate Professor in Fusion Plasma Physics in the same institute.

Mazur is the inventor of 69 granted patents and has authored several journal articles in international physics journals and conference papers on international conferences. She is the co-author of the book Handbook of antennas in wireless communication. She maintains close ties with several universities and is a member of the strategic advisory board of the School of Electrical Engineering in the KTH Royal Institute of Technology in Sweden and member of Royal Swedish Academy of Engineering Sciences (IVA) on Education and Research. Mazur is since 2013 a member of the Board of Directors of Saab AB.

On Pilot Contamination in Massive MIMO

Speaker: Wolfgang Utschick (Technische Universität München, Germany)


Massive MIMO is a promising technology for the next generation of cellular wireless networks. The idea is basically to deploy a large number of antennas at each base station such that the number of antennas is at least an order of magnitude larger than the number of simultaneously served users. As a desired consequence the resulting array gain leads to an increased energy efficiency and, more importantly, for a typical wireless channel, the large number of antennas leads to approximately orthogonal channel vectors for two different users due to the law of large numbers. This enables robust spatial multiplexing with simple signal processing methods. For perfect channel state information, the typical interference phenomena are negligible due to the mentioned mutual orthogonality of channel vectors. However, for a block fading channel model with limited coherence time and frequency, the limited number of available channel accesses per channel realization results in a dimensionality bottleneck. This dimensionality bottleneck gives rise to the pilot contamination effect which has been observed in the classical massive MIMO setup. Pilot contamination describes the interference in the channel estimates obtained in the uplink that is caused by the fact that the number of channel accesses in one coherence block is too small to give every user an orthogonal training sequence. The interference in the channel estimates in turn leads to interference during data transmission, which ultimately limits the performance of a massive MIMO system even for an unlimited number of antennas at each base station. Fortunately, this is not the final word on massive MIMO, however, since the typical rich channel structure in massive MIMO scenarios can be taken into account to mitigate the undesired consequences of pilot contamination. In this talk, we discuss two directions how to suppress or at least to lessen the detrimental effects of pilot contamination. To this end, we firstly introduce novel blind and semi-blind channel estimation methods for cellular time- division duplexing systems. The methods are based on the maximum a- posteriori principle given a prior for the distribution of the channel vectors and the received signals from the uplink training and data phases. Contrary to the state-of-the-art massive MIMO channel estimators, the proposed semi-blind method efficiently suppresses most of the interference caused by pilot- contamination. In the second part of the talk, we show how to push the limits of massive MIMO systems by exploiting the statistical properties of the channels. We propose a novel precoding approach for massive MIMO systems, which extends the conventional pilot contamination precoding idea. To this end, we introduce an additional precoding stage, which is independent of the instantaneous CSI, but depends solely on channel distribution information. The proposed technique completely removes the interference caused by pilot contamination. Simulations results will show the effectiveness of this technique for a pilot contamination limited massive MIMO systems.


Wolfgang UtschickWolfgang Karl Utschick completed several accredited industrial training programs in electronics before he received the diploma and doctoral degrees in electrical engineering, both with honors, from Technische Universität München (TUM). In 2002 he has been appointed Professor at TUM where he is director of the Fachgebiet Methoden der Signalverarbeitung (Signal Processing). Wolfgang teaches courses on Signal Processing, Stochastic Processes, and Optimization Theory in the field of Wireless Communications and Signal Processing applications. Since 2011 he is serving as a regular guest professor at Singapore's new autonomous university, Singapore Institute of Technology (SIT). He holds some 20 patents in the field of multiantenna signal processing and has authored and co-authored more than 300 technical articles in international journals and conference proceedings. He edited several books and is founder and editor of the Springer book series "Foundations in Signal Processing, Communications and Networking". Dr. Utschick has been Principal Investigator in multiple research projects funded by the German Research Fund (DFG). He is currently the coordinator and spokesman of the national DFG priority program "Communications over Interference limited Networks" (COIN) which is dedicated to topics as cooperative communications, crosslayer design, ad-hoc wireless networks, etc. He is a member of the VDE and senior member of the IEEE, where he serves as an elected member for the IEEE Signal Processing Society Technical Committee on Signal Processing for Communications and Networking since 2010 during his second term. He has been serving a full term as chairman of the deans of study affairs at TUM, and since 2011 he is member of the steering committee of the Department for Electrical and Computer Engineering at TUM.

One Decade of 'Sensorless Sensing': Wireless Networks as Human Context Sensors

Speaker: Neal Patwari (University of Utah, USA)


Standard radio transceivers make radio channel measurements which change due to the movements of people; thus a deployed wireless network can be used as a “sensorless sensor” to estimate the locations, activities, and gestures of people in the area in which the devices are deployed. The term was coined in 2006 by Woyach, Puccinelli, and Haenggi to describe how a wireless sensor network serves as a sensor even if no specific sensors are attached to the wireless devices. The area is also referred to as “device-free” because the people being sensed carry no radio device. In the past decade of sensorless sensing, a variety of experimental research has shown that people can be located with sub-meter accuracies, their activities, poses, and gestures they are performing can be distinguished from each other, and their breathing rate estimated. The results have application in health care, security, logistics, and in general in context aware computing. We describe the progress that has been made in exploiting channel measurements for human context sensing and the significant open challenges that remain.


Neal PatwariNeal Patwari received the B.S. (1997) and M.S. (1999) degrees from Virginia Tech, and the Ph.D. from the University of Michigan, Ann Arbor (2005), all in Electrical Engineering. He was a research engineer in Motorola Labs, Florida, between 1999 and 2001. Since 2006, he has been at the University of Utah, where he is an Associate Professor in the Department of Electrical and Computer Engineering, with an adjunct appointment in the School of Computing. He directs the Sensing and Processing Across Networks (SPAN) Lab, which performs research at the intersection of statistical signal processing and wireless networking. Neal is the Director of Research at Xandem, a RF sensing technology company. His research interests are in radio channel signal processing, in which radio channel measurements are used to benefit security, networking, and localization applications. He received the NSF CAREER Award in 2008, the 2009 IEEE Signal Processing Society Best Magazine Paper Award, the 2011 University of Utah Early Career Teaching Award, and best paper awards at SenseApp 2012 and IPSN 2014.

Cooperative Radar and Communications Signaling

Speaker: Daniel W. Bliss (Arizona State University, USA)


Historically, radar and radio operations have been adversarial. Because each system typically considers the other to be a source of unacceptable interference, the systems are traditionally allocated independent spectrum in any given region of space. Consequently, these systems compete for scarce spectral resources. As the demand for wireless communications has increased, the competition between the systems has become more raucous.

Fundamentally, we challenge the premise that these systems should be adversarial. By blurring the line between radar and communications systems, the performance of both systems can be improved potentially. One simple example is the parasitic radar, which is sometimes denoted a passive or “green” radar. In this example, a communications broadcast signal is employed as a radar illuminator. There are a variety of limits to this approach. First, the “radar” receiver has to construct a reference of the broadcast signal. Second, the communications system parameters may not have the most desirable characteristics for radar performance. Despite these concerns, this limited approach is a useful example of significant potential performance improvements as a radar capability is enabled in a spectral allocation where none existed previously.

We suggest a more fundamental level of cooperation for which the distinction between nodes traditionally identified as radar and radio is removed. A simple example, is using the “radar” as a communication relay. We suggest a joint estimation and communication RF energy employment that is cognitive in a more general sense than is used typically. This suggestion invites the investigation of the fundamental limits of performance for these joint systems.

Immediately, the question of specific metrics for joint performance presents itself. Communications systems can be characterized by a number of metrics, including latency and data rate. Radar systems are often characterized by detection and estimation performance. Combining these metrics to produce a joint performance metric is an open area of research.

In our research, we investigate system concepts and the fundamental bounds on joint radio and radar performance by using an analogy to the communications multiple-access channel. We propose a novel joint estimation and information theoretic bound formulation for a receiver that observes communications and radar return in the same frequency allocation. To enable this joint bound, we construct a novel metric, which we denote estimation rate. The joint performance bound is presented in terms of bounding surfaces for the communications rate and estimation rate of the system.

In this talk, we present an overview of the current state of research for joint communications and radar operation with an emphasis on joint performance bounds. We also identify opportunities for future research directions.


Dan BlissDaniel W. Bliss is an Associate Professor in the School of Electrical, Computer and Energy Engineering at Arizona State University. Dan received his Ph.D. and M.S. in Physics from the University of California at San Diego (1997 and 1995), and his B.S. in Electrical Engineering from Arizona State University (1989). His current research topics include statistical signal processing, multiple-input multiple-output (MIMO) wireless communications, MIMO radar, cognitive radio and radar systems, radio network performance bounds, geolocation techniques, channel phenomenology, and signal processing and machine learning for anticipatory physiological monitoring. Dan has been the principal investigator on numerous programs with applications to radio, radar, and medical monitoring. He has made significant contributions to robust multiple-antenna communications including important theoretical results, multiple patents, and the development of advanced fieldable prototype systems. He is responsible for some of the foundational MIMO radar literature, and was the principal investigator on an airborne ground moving target indicator (GMTI) MIMO radar program that demonstrated experimentally the validity of the theoretical results.

Before moving to ASU, Dan was a senior member of the technical staff at MIT Lincoln Laboratory (1997-2012) in the Advanced Sensor Techniques group, where he performed research in the areas of communications, radar, and anticipatory physiological monitoring. Between his undergraduate and graduate degrees Dan was employed by General Dynamics (1989-1991), where he designed avionics for the Atlas- Centaur launch vehicle, and performed research and development of fault-tolerant avionics. As a member of the superconducting magnet group at General Dynamics (1991-1993), he performed magnetic field calculations and optimization for high-energy particle-accelerator superconducting magnets. His doctoral work (1993-1997) was in the area of high-energy particle physics, searching for bound states of gluons, studying the two-photon production of hadronic final states, and investigating innovative techniques for lattice-gauge-theory calculations. He has published a graduate-level textbook on adaptive wireless communications, has published over 80 technical articles and conference papers, and he received the Best Lecture Award for his 2008 Tri-Service Radar paper that discussed MIMO radar. He is a Fellow of the IEEE.

5G The Ultimate Wireless Platform

Speaker: Klaus Doppler (Nokia Research Center, USA)


Cellular networks have evolved from a voice centric design to a wireless platform for a diverse set of applications. The evolution of 4G/LTE will support operation in licensed as well as unlicensed band, direct communications between devices and machine type communication with up to 10 years of battery life. 5G will be the next major wireless standard extending the success story of 4G/LTE. It will power 50bn+ connected devices and enable for example extreme mobile broadband, tactile internet experience and mission critical communication to autonomous vehicles. Key performance targets include peak data rates beyond 10Gbps and latency below 1ms. In this plenary talk we will introduce the motivation for 5G, example use cases and the main design parameters. We will also present key technology enablers, the 5G ecosystem and its expected timeline. We will put a special emphasize on Device-to-Device communications.


Klaus DopplerKlaus Doppler is heading the Radio Communications research in Nokia LABS, part of Nokia Technologies. His team is responsible for the 3GPP LTE, WLAN and 5G research and standardization of Nokia Technologies and explores new opportunities in radio implementation. In the past he has been leading the Wireless Systems team at Nokia Research Center in Berkeley, CA which contributed to IEEE802.11ah standardization and to the establishment of a new business line in Nokia Technologies. He led and contributed to several research activities on the design and integration of novel radio concepts into wireless systems, including device-to-device communication, (cooperative) relaying and multiband operation. He received several inventor awards at Nokia between 2007 and 2011. Klaus received his PhD. from Helsinki University of Technology, Finland in 2010 and his MSc. in Electrical Engineering from Graz University of Technology, Austria in 2003. He has more than 75 pending and granted patent applications and he has published 30 journal and conference publications and book chapters.

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