Joint source-channel rate allocation with unequal error protection for space image transmission

High reliable and efficient image transmission is of primary importance for space communications. In the traditional space image transmission system design, the source coding module and channel coding module are separated. This separate design, although simple to be implemented, cannot explore the transmission performance to the most. In this article, we propose a joint source-channel rate allocation framework to improve the space image transmission performance. A joint rate allocation algorithm based on the packet loss rate is proposed. For certain required system transmission rate, the optimal source coding and channel coding rate pair can be selected from pre-configured code rate sets by sliding search. In addition, our design has taken into account the progressive scalability feature of the image compression results. Each of the source coding output packets is divided into several sub-packets with different levels of significance and then channel coding with different rates is applied on these sub-packets to achieve unequal error protection. Simulation results show that the proposed joint design can significantly improve the image reconstruction quality. Compared with the traditional separate design, the proposed joint design can achieve 3-5 dB performance gain in terms of peak signal-to-noise ratio.