时变信道下ADF协作车载通信误码率分析

智能车载协作系统中车辆快速移动使得无线通信信道具有时变特性,为有效评估系统的误码性能,给出了符合车载时变信道的一阶自回归(AR1)模型,提出了一种基于AR1模型的自适应解码转发(ADF)协作误码率分析方法.该方法通过AR1模型的多普勒频偏相关系数来刻画时变信道特性,根据中继译码结果自适应选择是否协作转发,提升了智能交通系统的可靠性.此外,利用矩生成函数(MGF)推导出ADF协作下多进制正交幅度调制(M-QAM)信号误码率封闭表达式,并分析了车载移动速度和信道状态信息(CSI)估计精度对误码性能的影响.数值仿真结果表明,车载系统能通过增加CSI估计精度,有效地减少车载快速移动引起的误码平顶值.该方法相对于放大转发(AF)协作通信方式,平均误码性能提高约8.7 dB.

Symbol error rate analysis of adaptive decode-and-forward vehicular cooperative communication in time-varying channels

In intelligent vehicular cooperative systems, wireless communication channels are characterized as time-varying fading channels due to the rapid motion of vehicles. To evaluate symbol error rate( SER) performance,a first-order autoregressive(AR1) process is presented for the vehicular time-varying chan-nels,and an analytical approach of the AR1 process based on adaptive decode-and-forward( ADF) is pro-posed. In this method,the time-varying characteristics are described by correlation coefficient of Doppler shift,and whether the relay forwards information adaptively according to decoding result or not. As a re-sult,the reliability of the system can be enhanced. In addition,moment generating function( MGF) is used to derive the closed-form expressions for SER of M-ary quadrature amplitude modulation( M-QAM) under ADF cooperative strategy,and the influence of vehicular velocities and channel state information( CSI) esti-mation accuracy on SER performance is also analyzed. The results of numerical simulation show that the error floor value caused by high velocity can be reduced by increasing the CSI estimation accuracy. Com-pared with amplify-and-forward( AF) strategy,the average SER performance of the proposed strategy can be increased by 8. 7 dB.