Title: "Distributed control of physical carrier sense in wireless networks"
Speaker: Dr. Kyung-Joon Park (UIUC)
Date: 10. 25 (Sat) 10:00am

The performance of carrier sense multiple access (CSMA) wireless networks depends heavily on the level of spatial reuse, i.e., how many concurrent transmissions can be allowed in the network.  The level of spatial reuse is primarily determined by physical carrier sense, and a key parameter for physical carrier sense is the carrier sense threshold. Our focus in this talk is on how to control the carrier sense threshold for improving network performance. We present a noncooperative game-theoretic framework, which leads to a fully distributed algorithm for tuning the carrier sense threshold of each node. We introduce a utility function of each node, which is a nondecreasing concave function of the carrier sense threshold. By incorporating a collision probability threshold, a pricing function is further introduced for each node to mitigate severe interference among nodes. Then, a cost function for each node is defined as the difference between the pricing and utility functions. We prove that the noncooperative carrier sense game admits a unique Nash equilibrium (NE) for uniformly strictly concave utility functions under some technical conditions. We derive sufficient conditions that ensure the convergence of the synchronous and asynchronous update algorithms for the carrier sense threshold.  Based on the analysis, we propose a fully distributed algorithm, called noncooperative carrier sense update algorithm (NCUA),  for tuning the carrier sense threshold.

Bio:
Kyung-Joon Park received his B.S., M.S. and Ph.D. degree in Seoul National University, Seoul, South Korea in 1998, 2000, and 2005, respectively. He worked at Samsung Electronics from 2005 to 2006. Currently, he is a postdoctoral researcher in the Department of Computer Science, University of Illinois at Urbana-Champaign, USA since 2006.