Joint source-channel coding based on adaptive wavelet pretreatment for image transmission over frequency selective fading channel

In order to improve the error resilient ability and transmission efficiency for image transmission over wireless frequency selective fading channels, a joint source-channel coding (JSCC) scheme was proposed. In which, MIMO-OFDM and adaptive wavelet pretreatment were combined together. MIMO-OFDM was used to deal with frequency-selective,time dispersive characterize of wireless fading channels;adaptive wavelet pretreatment was adopted to decrease the encoder complexity whilst maintaining the transmission quality to acceptable level. To guarantee the quality of reconstructed image, the wavelet pretreatment block was adopted or removed adaptively according to the variety of channel condition. Here, the channel condition was indicated by the variety of the source packet size allocated to OFDM sub-channels, rather than the feedback information from the receiver as usual. Simulation results show that: the proposed scheme can support robust image transmission with high quality and low complexity in various channel conditions; When the channel condition is good (SNR= 9dB) the complexity of the encoder decrease to 1/3, but the PSNR of the received image lose less than 3 unit; When channel is worse (SNR<4dB) the pretreatment block is removed adaptively.