Reduced-complexity power allocation and modulation scheme for image transmission over wireless channels

In this paper, a low-complexity power allocation scheme for M-QAM is proposed with no need for feedback of channel state information. The Optimization is based on bit power allocation according to the importance of bits to the overall image quality. An iterative off-line algorithm is presented to find the optimum power and modulation level allocated to different bits. Our results show that the proposed scheme performs similar to the optimized M-QAM scheme over slow fading channel, yet with much lower complexity. For the case of the variable M-QAM system, a slight degradation of about 2 dB for high Eb/N0 is experienced by the proposed scheme which is again compensated for by the lower complexity of the system.