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Home | Seminars and Symposia | Past seminars/symposia: Monday, September 15, 2008

Communicating Delay-Sensitive and Bursty Information over an Outage Channel


Tara Javidi
UC San Diego

Monday, September 15, 2008
2:00 pm

402 Walter Library

In this talk, we consider the classic (cross-layer) queue-channel optimization problem for bursty and delay-sensitive information sources. In particular, we are interested in communications over outage-limited channels (with no feedback) when the number of bits that arrive at the transmitter during any time slot is random but the delivery of bits at the receiver must adhere to a strict delay constraint. In this setting, the errors experienced by the source of information, concatenated with an infinite buffer and a constant-rate outage-limited channel, are caused by either erroneous decoding at the receiver or violation of the delivery deadline. It is intuitive, then, that there is a trade off between reliability over the channel and timely delivery of information. After briefly revisiting the difficulty in quantifying the above trade-off in its classical Shannon Theoretic context, we take advantage of the recently developed high SNR analysis of outage-limited channels to go around this difficulty. Hence, the focus of the talk becomes to characterize the error performance of the overall system in the high SNR regime. We will see that the optimal decay behavior of the asymptotic error probability depends on how fast the burstiness of the source scales down with its mean, which itself scales with SNR. We will focus on a particular scaling under which the optimal exponent of the total error probability reveals a tradeoff addressing the following classical question: How much of the delay budget and channel capacity should be utilized for gaining reliability over the channel versus accommodating the burstiness of the delay sensitive source? Time permitting, we will address the extension of this work to a multi-user scenario and the resulting many flow large deviation analysis of multi-queue systems with interacting service.


Tara Javidi studied electrical engineering at Sharif University of Technology, Tehran, Iran from 1992 to 1996. She received the MS degrees in electrical engineering (systems), and in applied mathematics (stochastics) from the University of Michigan, Ann Arbor. She received her Ph.D. in electrical engineering and computer science from the University of Michigan, Ann Arbor, in May 2002. From 2002 to 2004, she was an assistant professor of electrical engineering at the University of Washington, Seattle. She joined University of California, San Diego, in 2005, where she is currently an assistant professor of electrical and computer engineering. She was a Barbour Scholar during 1999–2000 academic year and received an NSF CAREER Award in 2004. Her research interests are in communication networks, stochastic resource allocation, and wireless communications.