Research Overview:

My research interests include wireless communications, information theory and communication theory. Below are some of my research projects with links to relevant publications. A chronological list can be found in my publications page. For a less technical overview, please check the article in Poly’s Cable Magazine.

· Cooperative Communications

· Joint Source and Channel Coding for Wireless Networks

· Wireless Physical Layer Security

· Power Efficient Multimedia Communications

· Preamble and Feedback Design in Multiple Antenna Systems

· Spread-Spectrum Techniques for Multiple Transmit Antennas

· Low Complexity Multiuser Communications

v Cooperative Communications

Wireless communication systems suffer from fading and multipath distortion, as well as interference caused by multiple users operating over a limited bandwidth. Cooperation of users, by enabling wireless terminals to assist each other in transmitting information to their desired destinations, provides a good solution to the problems that current wireless technologies face. At the physical layer, terminals overhear one another’s signals, process and retransmit to form a virtual antenna array. Through cooperation, it is possible to obtain the spatial diversity benefits of multi-input multi-output (MIMO) systems without necessarily having a physical antenna array at each terminal. Furthermore, unlike MIMO systems, cooperation is able to successfully mitigate shadow fading. Cooperative communication techniques can easily adapt to the changing environment by opportunistically redistributing network resources such as energy and bandwidth. Incorporating the notion of cooperation at the medium access control (MAC) layer extends the benefits to large networks resulting in high throughput, low delay, reduced interference, low transmitted power and extended coverage. Cross-layer design between the application layer and the physical layer enables high quality multimedia transmission over cooperative wireless links.

Our work in this area spans multiple layers of the protocol stack including physical, MAC, networking and application layers as well as cross-layer design. We are interested the theory of cooperative networking (such as information theoretic aspects) as well as implementation (such as a cooperative networking testbed). Our paper “User cooperation-diversity: Part I and II” won 2004 Communications Society Stephen O. Rice Paper Prize in the Field of Communications Theory, as the best original paper published in IEEE Transactions on Communications in 2003. The paper “Diversity-multiplexing tradeoff in half-duplex relay systems” was selected as the best paper of the Communication Theory Symposium of ICC 2007.

This research is partially funded by NSF, Philips, WICAT, CATT and Othmer Institute for Interdisciplinary Studies.

Related Publications:

Journal:

v Submitted:

• O. Alay, T. Koarkis, Y. Wang, E. Erkip and S. Panwar. Layered wireless video multicast using relays. Under review, IEEE Transactions on Multimedia.
• T. Korakis, M. Knox, E. Erkip and S. Panwar. Cooperative network implementation using open source platforms. Under review, IEEE Communications Magazine.
• F. Verde, T. Korakis, E. Erkip and A. Scaglione. A simple recruitment scheme of multiple nodes for cooperative MAC. Under review, IEEE Transactions on Communications.

v Published:

• M. Yuksel and E. Erkip. Multi-antenna cooperative wireless systems: A diversity multiplexing tradeoff perspective. IEEE Transactions on Information Theory, Special Issue on Models, Theory, and Codes for Relaying and Cooperation in Communication Networks, vol. 53, no. 10, pp. 3371-3393, October 2007.

• D. Gunduz and E. Erkip.  Source and channel coding for cooperative relaying. IEEE Transactions on Information Theory, Special Issue on Models, Theory, and Codes for Relaying and Cooperation in Communication Networks, vol. 53, no. 10, pp. 3453-3475, October 2007.
• A. Chakrabarti, E. Erkip, A. Sabharwal and B. Aazhang. Code designs for cooperative communication. IEEE Signal Processing Magazine, Special Issue on Signal Processing for Multiterminal Communication Systems, vol. 24, no. 5, pp.16-26, September 2007.
• H.Y. Shutoy, D. Gunduz, E. Erkip and Y. Wang. Cooperative source and channel coding for wireless multimedia communications. IEEE Journal on Selected Topics on Signal Processing, Special Issue on Network-Aware Multimedia Processing and Communications, vol. 1, no. 2, pp. 295-307, August 2007.

• D. Gunduz and E. Erkip. Opportunistic cooperation by dynamic resource allocation. IEEE Transactions on Wireless Communications, vol. 6, no. 4, pp. 1446-1454, April 2007.
• P. Liu, Z. Tao, Z. Lin, E. Erkip and S. Panwar. Cooperative wireless communications: A cross-layer approach. IEEE Communications Magazine, vol. 13, no. 4, pp. 84-92, August 2006. (invited paper).
• Z. Lin, E. Erkip and A. Stefanov. Cooperative regions and partner choice in coded cooperative systems. IEEE Transactions on Communications, vol. 54, no. 7, pp. 1323-1334, July 2006.
• A. Stefanov and E. Erkip. Cooperative space-time coding for wireless networks. IEEE Transactions on Communications, vol. 53, no. 11, pp. 1804-1809, November 2005.
• A. Stefanov and E. Erkip. Cooperative coding for wireless networks. IEEE Transactions on Communications, vol. 52, no. 9, pp. 1470-1476, September 2004.
• A. Sendonaris, E. Erkip and B. Aazhang. User cooperation diversity-Part I: System description. IEEE Transactions on Communications, vol. 51, no. 11, pp. 1927-1938, November 2003. (2004 Communications Society Stephen O. Rice Paper Prize)
• A. Sendonaris, E. Erkip and B. Aazhang. User cooperation diversity-Part II: Implementation aspects and performance analysis. IEEE Transactions on Communications, vol. 51, no. 11, pp. 1939-1948, November 2003. (2004 Communications Society Stephen O. Rice Paper Prize)

Book Chapter:

• M. Yuksel and E. Erkip. Information Theoretical Limits on Cooperative Communications. To appear in Cooperative Communications for Improved Wireless Network Transmission, edited by Murat Uysal, IGI-Global (invited).
• E. Erkip, A. Sendonaris, A. Stefanov and B. Aazhang. Cooperative Communication in Wireless Systems. In Advances in Network Information Theory, edited by Piyush Gupta, Gerhard Kramer and Adriaan J. van Wijngaarden, pp. 303-320, AMS DIMACS Series, 2004.

Conference:

v 2008:

• P. Liu, Y. Liu, T. Korakis, A. Scaglione, E. Erkip, S. Panwar. Cooperative MAC for rate adaptive randomized distributed space-time coding. To appear, in Proceedings of 2008 GLOBECOM Wireless Networking Symposium, New Orleans, Lousiana, November 2008.
• O. Alay, K. Guan, Y. Wang, E. Erkip, S. Panwar, R. Ghanadan. Wireless video multicast in tactical environments. To appear in Proceedings of MILCOM 2008, San Diego, California, November 2008.
• O. Sahin and E. Erkip. Cognitive relaying with one-sided interference. To appear in Proceedings of Forty Second Annual Asilomar Conference on Signals, Systems and Computers, Pacific Grove, California, October 2008 (invited).
• O. Alay, R. Ding, E. Erkip, Y. Wang, A. Scaglione. Layered randomized cooperation for multicast. To appear in Proceedings of Forty Second Annual Asilomar Conference on Signals, Systems and Computers, Pacific Grove, California, October 2008 (invited).
• K. Bakanoglu, S. Tomasin, E. Erkip. Resource allocation for the parallel relay channel with multiple relays. To appear in Proceedings of Forty Second Annual Asilomar Conference on Signals, Systems and Computers, Pacific Grove, California, October 2008.
• D. Gunduz, E. Erkip, A. Goldsmith and H.V. Poor. Lossy source transmission over the relay channel. In Proceedings of IEEE International Symposium on Information Theory, Toronto, Canada, July 2008.
• F. Verde, T. Korakis, E. Erkip and A. Scaglione. On avoiding collisions and promoting cooperation: Catching two birds with one stone. In Proceedings of 2008 International Workshop on Signal Processing Advances for Wireless Communications (SPAWC), Recife, Brazil, July 2008.
• O. Sahin and E. Erkip. Cooperative interference management: The role of cognitive relaying. Presented at the 2008 IEEE Communication Theory Workshop (invited talk), St. Croix, USVI, May 2008. Click here for the slides.
• O. Alay, T. Korakis, Y. Wang, E. Erkip and S. Panwar. Layered wireless video multicast using omnidirectional relays. To appear, Proceedings of ICASSP, Las Vegas, NV, April 2008.

• J. Yang, D. Gunduz, D.R. Brown III, E. Erkip. Resource allocation for cooperative relaying. In Proceedings of 2008 Conference on Information Sciences  and Systems, Princeton, NJ, March 2008.

v 2007:

• O. Sahin and E. Erkip. Achievable rates for the Gaussian interference relay channel. In Proceedings of 2007 GLOBECOM Communication Theory Symposium, Washington D.C., November 2007.
• O. Sahin and E. Erkip. On achievable rates for interference relay channel with interference cancellation. In Proceedings of Forty First Annual Asilomar Conference on Signals, Systems and Computers, Pacific Grove, California, November 2007 (invited paper).
• O. Alay, E. Erkip and Y. Wang. Cooperative transmission of correlated Gaussian sources. In Proceedings of Forty First Annual Asilomar Conference on Signals, Systems and Computers, Pacific Grove, California, November 2007.
• K. Bakanoglu, D. Gunduz, E. Erkip. Dynamic resource allocation for the broadband relay channel. In Proceedings of Forty First Annual Asilomar Conference on Signals, Systems and Computers, Pacific Grove, California, November 2007.
• M. Yuksel and E. Erkip. Secure communication with a relay helping the wiretapper. In Proceedings of 2007 Information Theory Workshop, Lake Tahoe, California, September 2007 (invited paper).
• D. Gunduz and E. Erkip. Reliable cooperative source transmission with side information. In Proceedings of 2007 Information Theory Workshop, Bergen, Norway, July 2007 (invited paper).
• M. Yuksel and E. Erkip. Diversity-multiplexing tradeoff in half-duplex relay systems. In Proceedings of 2007 ICC Communication Theory Symposium, Glasgow, Scotland, June 2007. (Best Paper Award, ICC 2007 Communication Theory Symposium)
• D. Gunduz, C. T. K. Ng, E. Erkip and A. J. Goldsmith. Source transmission over relay channel with correlated relay side information. In Proceedings of IEEE International Symposium on Information Theory, Nice, France, June 2007.

• M. Yuksel and E. Erkip. The relay channel with a wiretapper. In Proceedings of 2007 Conference on Information Sciences  and Systems, Baltimore, MD, March 2007.

• O. Sahin and E. Erkip. Dynamic resource allocation for multi source-destination relay networks. In Proceedings of 2007 Conference on Information Sciences and Systems, Baltimore, MD, March 2007.

v 2006:

• Z. Lin, E. Erkip and M. Ghosh. Rate adaptation for coded cooperative systems. In Proceedings of 2006 GLOBECOM Communication Theory Symposium, San Francisco, December 2006.
• H. Shutoy, Y. Wang and E. Erkip. Cooperative source and channel coding for wireless video transmission. In Proceedings of IEEE International Conference on Image Processing, Atlanta, Georgia, October 2006 (invited paper).
• M. Yuksel and E. Erkip. Diversity-multiplexing tradeoff in multiple-antenna relay systems. In Proceedings of 2006 IEEE International Symposium on Information Theory, Seattle, July 2006.
• M. Yuksel and E. Erkip. Diversity-multiplexing tradeoff in cooperative wireless systems. In Proceedings of the 2006 Conference on Information Sciences and Systems, Princeton University, New Jersey, March 2006.

v 2005:

• Z. Lin and E. Erkip. Relay search algorithms for coded cooperative systems. In Proceedings of  2005 GLOBECOM Communication Theory Symposium, St. Louis, December 2005.
• M. Yuksel and E. Erkip. Can virtual MIMO mimic a multi-antenna system: Diversity-multiplexing tradeoff for wireless relay networks. Presented at the 2005 IEEE Communication Theory Workshop (invited talk), Park City, Utah, June 2005. Click here for the slides.
• D. Gunduz and E. Erkip. Outage minimization by opportunistic cooperation. In Proceedings of 2005 WirelessCom, Symposium on Information Theory, Maui, Hawaii, June 2005.
• Z. Lin, E. Erkip and M. Ghosh. Adaptive modulation for coded cooperative systems. In Proceedings of 2005 International Workshop on Signal Processing Advances for Wireless Communications (SPAWC), New York City, June 2005.
• D. Gunduz and E. Erkip. Source and channel coding for cooperative relaying. In Proceedings of 2005 International Workshop on Signal Processing Advances for Wireless Communications (SPAWC), New York City, June 2005 (invited paper).
• X. Xu, D. Gunduz, E. Erkip and Y. Wang. Layered cooperative source and channel coding. In Proceedings of 2005 ICC Multimedia Communication and Home Networking Symposium, Seoul, Korea, May 2005 (invited paper).
• D. Gunduz and E. Erkip. Opportunistic cooperation and power control strategies for delay-limited capacity. In Proceedings of the 2005 Conference on Information Sciences and Systems, Baltimore, March 2005.

v 2004:

• X. Xu, Y. Wang and E. Erkip. Layered cooperation for wireless multimedia communications. In Proceedings of 2004 Picture Coding Symposium, San Francisco, December 2004 (invited paper).
• Z. Lin, E. Erkip and A. Stefanov. Cooperative regions for coded cooperative systems. In Proceedings of  2004 GLOBECOM Communication Theory Symposium, Dallas, December 2004.
• M. Yuksel and E. Erkip. Broadcast strategies for the fading relay channel. In Proceedings of 2004 Military Communications Conference, Monterey, November 2004 (invited paper).
• Z. Lin, E. Erkip and A. Stefanov. Exact pairwise error probability for the MIMO block fading channel. In Proceedings of 2004 International Symposium on Information Theory and its Applications, Parma, Italy, October 2004.
• Z. Lin, E. Erkip and A. Stefanov. An asymptotic analysis on the performance of coded cooperation systems. In Proceedings of 2004 Fall Vehicular Technology Conference, Los Angeles, September 2004.
• D. Gunduz and E. Erkip. Joint source-channel cooperation: Diversity versus spectral efficiency. In Proceedings of 2004 International Symposium on Information Theory, Chicago, June 2004.
• M. Yuksel and E. Erkip. Diversity gains and clustering in wireless relaying. In Proceedings of 2004 International Symposium on Information Theory, Chicago, June 2004.

v 2003:

• M. Yuksel and E. Erkip. Diversity in relaying protocols with amplify and forward. In Proceedings of 2003 GLOBECOM Communication Theory Symposium, San Francisco, December 2003.
• Z. Lin, E. Erkip and A. Stefanov. Simple derivation of exact pairwise error probability for Rayleigh block fading channels. In Proceedings of 41st Annual Allerton Conference on Communication, Control and Computing, October 2003.
• A. Stefanov and E. Erkip. Cooperative Coding Theory and Applications. Presented at the 32nd Annual IEEE Communication Theory Workshop (invited talk), Mesa, Arizona, April 2003.
• A. Stefanov and E. Erkip. Cooperative Space-Time Coding for Wireless Networks. In Proceedings of IEEE Information Theory Workshop, La Sorbonne, Paris, France, April 2003.
• A. Stefanov and E. Erkip. On the performance analysis of cooperative space-time coded systems. In Proceedings of IEEE Wireless Communications and Networking Conference (WCNC 2003), New Orleans, Lousiana, March 2003.

v Prior to 2003:

• A. Stefanov and E. Erkip. Cooperative coding for wireless networks. In Proceedings of IEEE Conference on Mobile and Wireless Communications Networks, Stockholm, Sweden, September 2002.
• A. Stefanov and E. Erkip. Cooperative information transmission in wireless networks. In Proceedings of 2002 Asian-European Information Theory Workshop, Breisach, Germany, June 2002.
• E. Erkip. Capacity and power control for spatial diversity. In Proceedings of the 2000 Conference on Information Sciences and Systems (invited talk), pp. WA4-28/WA4-31, Princeton University, New Jersey, March 2000.
• A. Sendonaris, E. Erkip and B. Aazhang. Increasing uplink capacity via user cooperation diversity. In Proceedings of 1998 IEEE International Symposium on Information Theory, page 156, MIT, August 1998.

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v Joint Source and Channel Coding for Wireless Networks

Transmission of multimedia signals over wireless networks poses several challenges that do not exist in wired networks. Bandwidth limitations of the wireless channel, interference from multiple users operating in the same band and channel variations due to fading become bottlenecks for typical multimedia applications that require high bandwidth and an error resilient communication medium.

This research outlines a cross-layer approach between the application layer and the physical layer to maintain desired end-to-end signal quality for multimedia transmission over bandwidth and power limited multiuser wireless channels. The objective is to design joint source and channel coding techniques to minimize the end-to-end source distortion. A general source and channel separation theorem for wireless networks does not exist; optimality of Shannon's separate source and channel code design fails for non-ergodic fading channels or for multiuser communication systems. On the other hand, even when source and channel separation is not optimal, it is desirable to have only a loose coupling between the source and channel coders to simplify the designs.

This project addresses joint source and channel coding for the fundamental building blocks of a wireless network, including single user (point-to-point), multiple access and relay channels. The system model is general to encompass different communication scenarios: Correlation among the source signals is allowed, the receivers may have correlated side information, the channel can be time-invariant or fading may be present, links can have multiple degrees of freedom such as multiple antennas or multiple fading blocks. This project investigates the design of optimal joint source and channel coding strategies, and performance improvements when minimal interaction among the source and channel coders is allowed. The goal is to discover scenarios under which separation is optimal, or close to optimal.

Our project also considers practical applications, in particular unicast and multicast wireless video. The emphasis is on cross-layer design to improve the quality of wireless video transmission using cooperative networking.