1 Cooperative Wireless Networking Elza Erkip Department of Electrical and Computer Engineering Polytechnic Institute of New York University

2 Motivation Future of internet: Wireless Wireless channels Bandwidth limited Limited battery life devices Multi-user interference Unreliable due to signal fading Vulnerable to attacks Multimedia applications High data rates Error sensitive, delay intolerant How to overcome these obstacles?

3 Cooperative Networking Wireless devices helping each other communicate with other devices or fixed infrastructure Cooperation provides a good solution to many of the problems arising in wireless systems

4 How Does Cooperation Work? Wireless antennas transmit in all directions Signals transmitted towards the base station can be “overheard” at the relay Relay processes this overheard information and re- transmits towards the destination –Total resources (energy, bandwidth) are same as non- cooperative case Base station processes signals from both mobiles Mobile Relay Base Station

5 Benefits of Cooperation Robustness to fading Opportunistic use of network energy and bandwidth Higher data rates, fewer retransmissions so less network delay Higher signal quality Lower total transmitted energy which reduces interference and extends the battery life Extended coverage

6 Cooperative Networking Applications Currently a “hot” research topic Also interest in industry, standardization –4G cellular Applications –Cellular Other mobiles can relay Fixed (cheap) relays: Femtocells

7 Cooperative Networking Applications WiFi Enterprise networking Vehicular ad-hoc networks Tactical networks

Cooperative Networking Applications Wireless Body Sensor Networks 8 Figure from Sun et. Al, IEEE Wireless Communications Magazine, February 2010

9 Poly’s Accomplishments Poly has pioneered research in cooperative communications IEEE paper award, cited extensively, top 10 downloaded article in IEEE Xplore A. Sendonaris, E. Erkip and B. Aazhang. User cooperation diversity- Part I and Part II, IEEE TCOM 2003 One of the first papers looking at system level issues –Top 100 downloaded article in IEEE Xplore P. Liu, Z. Tao, Z. Lin, E. Erkip and S. Panwar. Cooperative wireless communications: A cross-layer approach, IEEE Wireless Magazine, IEEE ICC Conference Best Paper M. Yuksel and E. Erkip. Diversity-multiplexing tradeoff in half-duplex relay systems, Proceedings of ICC, One of the first groups to implement a cooperative networking testbed

10 Cooperative Poly Goal: A complete cooperative networking solution –Establish the theory –Develop algorithms –Study applications –Implementation Multiple Poly faculty and students –Bertoni, Erkip, Knox, Memon, Panwar, Wang Government and industrial funding

Testbed Facilities 11

Testbed Facilities

Experimental Results

14 Conclusions Cooperation: Paradigm shift in wireless communications Offers –Spatial diversity –Higher throughput –Lower delay –Reduced energy consumption –Extended coverage –Higher quality multimedia –Improved security Cooperation in 4G cellular wireless standards Many exciting projects studying cooperation at all layers of the protocol stack –Theory + implementation Still many challenges