An Adaptive Hybrid Digital-Analog Modulation Scheme

Hybrid Digital-Analog (HDA) transmission has been proved to be an effective technique to overcome the "cliff effect" in wireless video communication. In this paper, we propose a novel HDA modulation scheme. The phase of modulation symbol is used to carry the digital signal while the amplitude of modulation symbol is used to carry analog signal. In order to make full use of channel capacity, the bit loading is utilized to adjust digital modulation order (M-PSK) based on effective channel, which is combination of channel state information (CSI) and analog signal. A SNR GAP approximate algorithm is used to implement the adaptive bit loading in OFDM system to reduce the computational complexity of bit loading. Our experimental results show that proposed HDA-MPSK modulation scheme under different SNR values can get linear effect of the image quality of reconstruction, which is much more stable. Meanwhile the adaptive bit and power allocation algorithm raise the channel capacity and bandwidth usage.