Progressive image transmission over space-time coded OFDM systems with adaptive modulation

This paper considers a progressive image transmission system over wireless channels by combining joint source-channel coding (JSCC), space-time coding and orthogonal frequency division multiplexing (OFDM) and evaluate its performance. The BER performance of space-time coded OFDM is first evaluated analytically by assuming perfect channel state information at the receiver for coherent detection. Then for a given average SNR (hence BER), a fast local search algorithm is applied to optimize the unequal error protection design in JSCC. With this end-to-end system performance measurement, an adaptive modulation scheme is proposed by assigning different constellation sizes to various SNR ranges to achieve the best image quality. Simulation results confirm the effectiveness of our proposed adaptive modulation scheme.