多径信道下MIMO系统发送天线数估计

摘要

Under the condition of unauthorized receivers and cognitive radios,the problem of detecting the number of transmit antennas in MIMO system with multi-path channel is to be solved.To achieve this goal,we analyze the invalidation of presenting model and transform the MIMO multi-path channel model into virtual channel matrix to create the model of detec-ting the number of transmit antennas in MIMO system with multi-path channel.Then,the result of least eigen-value of covari-ance in random matrix theory is applied to the proof,which shows that the least eigen-value of channel covariance whose ele-ment obeys the Rayleigh distribution,converges in distribution to the Tracy-Widom law TW2. The effect on detecting the num-ber of transmit antennas of this property is analyzed and an improved algorithm based on RMT,which could detect the number of transmit antennas in MIMO system with multi-path channel,is proposed.At last,the simulation shows that compared with the RMT algorithm the improved algorithm has better performance,in the condition of low SNR and small data size.%为了解决认知无线电或信号截获中多径信道下MIMO系统发送天线数估计问题，首先分析了现有模型在多径信道下失效的原因，将MIMO多径信道模型等效变换出一种虚拟信道矩阵，从而建立多径信道下MIMO系统发送天线数估计模型；然后，利用随机矩阵理论中协方差矩阵最小特征值分布的相关研究结果，证明了时不变瑞利信道的协方差矩阵最小特征值收敛于第二类Tracy-Widom分布，分析了该特点对发送天线数估计的影响，并提出一种改进的RMT估计算法来估计多径信道下MIMO系统发送天线数。最后对改进算法进行了仿真验证，结果表明在低信噪比和小数据条件下，改进算法的估计性能相比RMT算法有较大提升。