Adaptive Mode- and Diversity-Control for Video Transmission on MIMO Wireless Channels

Video transmitted over wireless channels incurs both encoder-induced distortion and distortion caused by transmission errors. To address these problems, we propose a framework to transmit video reliably over a Rayleigh-fading wireless channel employing multiple transmit and receive antennas. Although the formulation makes no assumptions about specific video-coding standards, it does presuppose some variation of motion-compensated block-transform coding. The scheme proposed here minimizes cumulative distortion over a window spanning multiple video units, and does so by adaptively controlling the diversity- and multiplexing-gain of the multiple-input multiple-output (MIMO) system. Crucially, this is done jointly with loss-aware rate-distortion optimization (LA-RDO) techniques at the video encoder. It turns out that MIMO and LA-RDO techniques, working in tandem, are more effective in minimizing distortion. The framework also ensures that delay and buffer constraints are satisfied for real-time transport. Numerical results with H.264-coded video show that adaptive MIMO and LA-RDO control yield tangible benefits (PSNR improvement), but only up to a point. Beyond this, real-time and buffer constraints limit what can be gained, even when the number of antennas is increased. In terms of solution approach, we show that the problem can be modelled as a sequence of geometric programs. Each problem can be solved optimally by a class of convex techniques known as primal-dual algorithms.