Adaptive Transmission Scheme Design Based On Satellite Cooperation

With the rapid development of technology,a series of demands for satellite communication is increasing.However,the high delay,multipath fading,and shadow fading of the satellite link have constrained the development of satellite communications.Therefore,it's very important to design satellite cooperative communication systems with high-quality satellite communications.In satellite cooperative communication,to cope with these problems we mentioned above.There are multiple candidate cooperative nodes in satellite cooperative communications.Therefore,choosing the right cooperative node to maximize system performance has become a research hotspot.In addition,the channels in satellite cooperative communications have time-varying characteristics.To improve system performance,an adaptive transmission scheme needs to be designed.This paper designs an adaptive satellite cooperative transmission scheme for the above two points.First,in order to solve the single-attribute spatial cooperative node selection strategy cannot balance the reliability and lifetime of the system.this paper proposes a Subjective and Objective Weighting Based Multi-attribute Cooperative Node Selection.In a space cooperative communication system,the cooperative relay-destination node and source node-destination node channel obey the Loo,Corazza two-state shadow fading model,and the source node-Cooperative relay channels are free-space channels.Firstly,the candidate cooperative relay transmits the cooperative request information including the three attributes to the destination node;next,use AHP and IE to establish the subjective and objective weight vector of attributes;then,calculate the subjective and objective weight vector using the maximum entropy and the dispersion and the maximum two objective functions;finally,us the weight vector to obtain the evaluation value for the attribute of each candidate cooperative relay node,and then select the best cooperative node to participate in the cooperative communication.The simulation results show that compared with BQ-CNS,EF-CNS and R-CNS,SOW-CNS improves system stability and lifetime.Second,aiming at the problem of low efficiency and unstable channel quality between inter-satellite communication systems,an adaptive transmission scheme based on space cooperation is prpposed.Firstly,the mutual information based HARQ and cooperative communication are combined,and the mutual information is used to predict the amount of redundant information that the destination node successfully decodes in the next retransmission with a preset probability and improves system efficiency.Secondly,an adaptive modulation and coding scheme based on spatial cooperation is designed based on the satellite shadow-fading channels of satellite-ground station and high-altitude platform-ground station.The bit error rate is simulated by using seven selected coding modulation methods.Calculate the signal-to-noise ratio range corresponding to each coded modulation method,and finally select the coding and modulation method through the SNR range in which the SNR estimate value falls.The simulation results show that MI-HARQ can effectively improve the system efficiency.The adaptive coded modulation scheme can reduce the systematic bit error rate and improve the system throughput.