一种GEO卫星移动通信信道质量近似方法

A New Approximation Method for GEO Satellite Mobile Communication Channel Quality

在LTE移动通信系统中信道质量指示参数(Channel Quality Indicator,CQI)是自适应调制编码(AdaptiveModulation and Coding,AMC)技术的一项重要参数。由于GEO卫星信道存在较长的传输时延,为保证有效的AMC调整,对CQI进行预测是非常必要的。但是大多数预测算法的可预测时长受到输入序列的相关时间限制,而含有小尺度衰落影响的信号的CQI序列的相关时间远远小于所需预测时长,对获得的CQI序列进行预测是不现实的。针对这一问题,提出了一种使用仅含有大尺度衰落的CQI数据进行预测的近似方法。将获得的CQI序列平滑后去掉小尺度衰落的影响,余下的数据可以认为是只受大尺度衰落影响,其相关时间可以大大延长。通过对GEO卫星信道信道质量进行建模分析,对使用近似方法处理前后的CQI序列数据差距以及相关时间的变化进行了数值仿真,结果表明所提出的近似方法不会导致CQI数据产生较大的偏差,且近似后的序列具有较长相关时间。在此种近似方法处理下的CQI数据相关时间能够满足预测模型的需要,从而为保证GEO卫星移动通信系统中使用AMC的可行性和可靠性提供可能。

CQI（ Channel Quality Indicator）is an essential indicator for AM C （Adaptive Modulation and Coding）technique in LTE. Due to the long delay of GEO satellite channel,CQI prediction is necessary to ensure effective AMC when applied to satellite system. However most prediction algorithms＇ prediction ability are limited by input sequences＇ correlation time,and the correlation time of CQI sequence containing small scale fading is much shorter than required prediction range, so it is difficult to do prediction. Large scale fading can be obtained by smoothing out the small scale fading from the real data, and its correlation time increases significantly. After the channel model is analyzed,an approximation method containing large scale fading is proposed. The concrete coarelation features and the difference between the approximation and the original data are all analyzed. Simulation is done for confirmation. The simulation results show that the approximate large scale CQI data is feasible and rational for prediction and ensuring AMC efficiency.