一种基于认知无线电的卫星网络信道接入策略

针对可用无线信道资源紧张与固定信道分配方式导致卫星网络信道利用率低下的问题，提出一种基于认知无线电的卫星网络信道接入策略。卫星用户以分时多址（TDMA）方式接入卫星信道，认知用户通过频谱感知发现卫星网络闲置信道资源，并以S-ALOHA方式接入信道。通过建立基于频谱感知与具有捕获效应的认知用户信道接入模型，分析认知用户最佳频谱感知时间，推导干扰信号在相干叠加与非相干叠加条件下的卫星网络吞吐率性能，并对影响网络吞吐率的因素进行仿真分析。结果表明，该信道接入策略能够在不明显降低高负载时卫星网络吞吐率的前提下有效提高低负载条件下的卫星网络吞吐率，且干扰信号相干叠加比非相干叠加对网络吞吐率性能的提升更为显著。

A Channel Access Strategy Based on Cognitive Radio for Satellite Communication Network

A channel access strategy based on the cognitive radio technique for satellite communication networks is proposed in order to solve the contradiction between limited wireless channel resource and low utilization ratio of assigned satellite spectrum caused by fixed channel allocation scheme. Satellite′s terrestrial users access to channels in time division multiple address (TDMA) mode, and cognitive users find out the idle channel first through spectrum sensing and then access to channels in S-ALOHA mode. The channel access models based on spectrum sensing and packet transmitting with capture effect are established and optimized spectrum sensing time is analyzed. Performances of throughput rate under the conditions of both incoherent and coherent superposition of interference signals are derived and factors affecting throughput rate are analyzed by simulations. The results indicate that the throughput rate of whole network has been promoted effectively when the traffic load of satellite networks is light while the influence on the throughput rate of satellite networks under heavy traffic load can be ignored, and the throughput rate of satellite networks is improved more remarkable under the condition of coherent superposition of interference signals compared with incoherent superposition of interference signals.