低轨卫星移动通信系统中译码前传协作策略的性能研究

摘要

The wireless channel in satellite mobile communication system is typical fading channel. The channel impairments can be usually described by three fading phenomena, including Rayleigh fading, Rician fading and shadowed Rician fading in different environments. To obtain reliable communications, there is a significant need for method to combat detrimental effects in this wireless fading channel. Recently,the eooperative diversity transmission technique has attracted considerable research attention as it is capable of significantly improving the performance of wireless communication systems. Several cooperation strategies with different relaying techniques, including amplify-and-forward ( AF) .decode-and-forward (DF) and Coded-Cooperation ( CC) , have been studied in Laneman Sendonaris and Hunter et al. 's seminal paper. In this paper,cooperative diversity technology was considered in the user downlink of the low Earth orbiting ( LEO) sateUite mobile communication system to reduce the influence of channel fading. The system model was given and the general error probability for decode-and-forward was analyzed.then the system errar probability over Rayleigh, Rician and shadowed Rician fading channels in the user downlink were obtained. The simulation results can coincide with the theory analysis. What's more, the results show that the proposed system can outperform the traditional system without the cooperative diversity technology.%卫星移动通信信道是典型的衰落信道,其信道特性在不同的环境中通常被表述为三种衰落形式,即Rayleigh 衰落、Rician衰落和遮蔽Rician衰落.为了保证可靠的通信,系统需要采用具有较强抗衰落能力的技术来进行信号的传输.近年来,协作分集技术因其能显著地提高无线通信系统的性能而吸引了大量的研究关注.莱曼等人的研究中提出了多种协同策略,包括放大前传,译码前传和编码协同等.本文中提出将协作分集技术应用在低轨卫星移动通信系统用户下行链路(卫星和终端用户之间的通信链路)中以减小信道衰落的影响.建立系统模型,分析得出该系统采用译码前传协作策略的通用误码率公式,由此推导出用户下行链路在Rayleigh衰落信道、Rician衰落信道、遮蔽Rician衰落信道条件下的系统误码率公式.仿真结果表明,理论分析和仿真结果完全吻合,本系统相对于传统无协作系统有较大的性能优势.