Research On Adaptive Transmission Algorithm Based On Rateless Codes Under Satellite Channel

Adaptive transmission technology can adjust the data transmission rate according to real-time channel status, so that the data transmission parameters dynamically match the current channel conditions, and it is an effective technique to improve channel utilization of the time-varying radio channel. Aiming at long delay satellite channel, this paper gives a rateless based adaptive transmission algorithm. The algorithm can get maximum throughput in the transmission delay and the decoder actual capacity constraints, and has great significance to improve the of transmission efficiency of satellite communication.Firstly, this paper introduces the satellite communication scene and channel characteristics, and gives the basic knowledge of rateless codes, hybrid automatic repeat request and the principle of rateless codes based adaptive transmission, and then describes the design of adaptive transmission protocol for long delay RTT satellite communication system. Secondly, this paper gives a detailed design of the adaptive algorithm, the algorithm adaptively adjust the size of the new package and incremental packet size based on real-time CDF table, as a result, it can achieve the design goal of gaining maximum throughput under the constraints of average transmission delay and cumulative decoder complexity. Finally, in order to better follow the channel change and reduce the frequency of new packet size Ping pong, this paper adds the SNR estimation algorithm, shift threshold technology and lagging technology, and verify by simulation that SNR estimation algorithm and shift threshold technology can further improve the throughput without increasing the decoder complexity and transmission times, and that lagging technology can effectively reduce the frequency of Ping pong of new packet size at a small expense of throughput decrease.The adaptive transmission algorithm in this thesis is suitable for non-SW protocol satellite communications, the CDF table based new packet size and increment packet size adaptive scheme can gain maximum throughput within the constraint of average number of transmissions and decoder complexity.