On the End-to-End Distortion for a Buffered Transmission over Fading Channel

In this paper, we study the end-to-end distortion/delay tradeoff for a analogue source transmitted over a fading channel. The analogue source is quantized and stored in a buffer until it is transmitted. There are two extreme cases as far as buffer delay is concerned: no delay and infinite delay. We observe that there is a significant power gain by introducing a buffer delay. Our goal is to investigate the situation between these two extremes. Using recently proposed effective capacity concept, we derive a closed-form formula for this tradeoff. For SISO case, an asymptotically tight upper bound for our distortion-delay curve is derived, which approaches to the infinite delay lower bound as D∞ exp( C τn ), with τn is the normalized delay, C is a constant. For more general MIMO channel, we computed the distortion SNR exponent – the exponential decay rate of the expected distortion in the high SNR regime. Numerical results demonstrate that introduction of a small amount delay can save significant transmission power. The material in this paper was presented in part at the International Symposium on Information Theory (ISIT), Seattle, WA, July 2004 The authors are with the Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX, USA. E-mail: {qiangli, georghiades}@ece.tamu.edu.