Cross-Layer Optimization for H.264/AVC Video Transmission Over Space-Frequency (SF) Coded MIMO-OFDM Systems

Multicarrier communication becomes a natural choice to transmit multimedia content at high data rates. Among multicarrier communication techniques, the combination of orthogonal frequency division multiplexing (OFDM) technology with multiple input multiple output (MIMO) systems is very effective for high data rate wireless communication. In this paper, we propose a cross layer optimization technique for transmitting H.264/AVC video data over a MIMO-OFDM wireless channel. A set of fast time-varying and frequency selective fading channels is considered. The channel is assumed to be unchanged for the duration of one OFDM block and change independently from one OFDM block to the other. The number of pilot symbols for each OFDM block is held constant and they are dispersed throughout the block for efficient channel estimation. The video transmission system uses a jointly optimal space frequency (SF) code design and pilot placement scheme. Rate compatible punctured convolutional (RCPC) codes are used for channel protection. The problem formulation selects the set of source and channel coding rates along with the optimal pilot placement for a total bit rate constraint. The performance of the optimal power allocation case is compared with the equal power distribution case. At the transmitter, we have developed a method for the estimation of the video distortion at the receiver for given channel conditions. The accuracy of this method is validated using experimental results. Computer simulation results are shown for a 2 x 2 MIMO-OFDM system but the results can be extended to MIMO-OFDM systems with any number of transmit and receive antennas.