一种用于星地高速通信的Raptor码设计

Design of Raptor Code for Space-to-Ground High Speed Communication

利用空间网络进行中继通信是未来星地通信的主要方式,而空间网络环境存在链路不稳定、传输距离大等缺陷,这些缺陷使得星地通信效率较低,且通信质量不理想。为了解决上述问题,提出一种适合空间网络中继通信的R印tor码作为前向纠删码。首先,以简化的LDGM码为外码、以弱化的LT码为内码得出Raptor码的编码结构,其次,为了适应中继星受限的星上存储与处理能力,对Shokrollahi提出的截短度分布函数进行改进,得出一个适合小文件传输的截短度分布函数作为内码的度分布函数。仿真结果表明,Raptor码能有效提高传输效率,编译码复杂度低,且译码开销较小。在星地中继通信时,Raptor码能满足高速通信的要求。

Relay communication by space network is the main method of future space - to - ground communication, however, space network has low stability and huge transmission distance, which results in low efficiency and poor quality of space - to - ground communication. A kind of Raptor code was designed as forward erasure code for space network to solve these problems. Firstly, using simplified LDGM as outer code and truncated LT as inner code, the coding structure of Raptor code was obtained. Secondly,in order to adapt to limited on - board storage and processing capability of relay satellites, a degree distribution function for small file was obtained by improving the truncated distribution function raised by Shokrollahi. Simulation results show that the Raptor code can effectively improve transmission effficiency,and has low complexity, besides, its decoding overhead is less than 15%. This Raptor code can meet the requirements of high - speed communication in space - to - ground relay communication.