一种 SC-CFDMA 卫星通信系统及其性能分析

摘要

To deal with the large peak to average power ratio (PAPR)of MC‐CDMA (multi‐car‐rier CDMA)and performance sensitivity to on‐board nonlinear high power amplifier (HPA),the pa‐per introduces a new communication system called single carrier code and frequency division multiple access (SC‐CFDMA),a kind of MC‐CDMA system which has signal characteristic of single carrier. This paper studies the mathematical model and analytical bit error rate (BER)of SC‐CFDMA system and probes into its adaptability to nonlinear satellite channel and its sensitivity to earth‐space trans‐mission delay.Research results show that:for linear channel,SC‐CFDMA and MC‐CDMA show e‐quivalent BER performance,besides,their simulated and analytical BER curves coincide.For nonlin‐ear channel,if with perfect synchronization,the interleaved SC‐CFDMA presents the lowest PAPR and BER,the localized SC‐CFDMA takes the second place,and MC‐CDMA is the poorest performer;If not,the timing offset in A/D sampling front end will be passed on to the dispreading section of in‐terleaved SC‐CFDMA and localized SC‐CFDMA totally or partially,thus generating multi‐user inter‐ference (MUI),with interleaved SC‐CFDMA bearing the most obvious performance degradation. However,such MUI can be shield off by zero correlation zone (ZCZ)codes.%针对 MC‐CDMA 信号峰均比较大、传输性能易受星上非线性功放影响的问题,提出一种信号呈现单载波特性的 MC‐CDMA 系统,即单载波码分与频分多址(SC‐CFDMA)系统。研究了 SC‐CFDMA 系统的数学模型和理论误码率,探讨了其对非线性卫星信道的适应性,分析了其对星地传输时延的敏感性。研究结果表明：在线性信道下,SC‐CFDMA 与 MC‐CDMA 的误码率性能一致,且理论和仿真误码率曲线吻合；在非线性信道下,若同步理想,则交织式 SC‐CFDMA 具有最低的峰均比和误码率,集中式 SC‐CFDMA 次之,MC‐CDMA 最高；若同步不理想,则由星地传输时延造成的定时偏差会分别等量和少量地传递至交织式 SC‐CFDMA 和集中式 SC‐CFDMA 的解扩环节,从而产生多用户干扰(MUI),其中交织式 SC‐CFDMA 的性能恶化最明显,而采用零相关区扩频码则可屏蔽这种 MUI。