信道反馈延迟的V-BLAST系统功率分配算法

Power Allocation Algorithm for V-BLAST System with Channel Feedback Delay

针对信道反馈的延迟问题,以降低误比特率(BER)为优化目标,提出一种适用于垂直分层空时编码系统的自适应发送功率分配算法。假设接收端可以得到完全的信道状态信息,并通过反馈链路将信道信息反馈至发送端。在接收端采用迫零检测算法,给出系统瞬时信噪比(SNR)与估计SNR的表达式推导过程,根据系统瞬时SNR的条件概率密度函数求出系统总BER的表达式;发送端在总功率约束条件下,采用拉格朗日极值法计算出自适应功率分配矩阵的闭式解。仿真结果表明,当归一化反馈迟延因子等于0.000 1、误比特率为10^(-3)时,该算法的系统性能比等功率分配算法提高约5 dB。

An Adaptive Transmission Power Allocation（ATPA） algorithm is presented for Vertical-bell Laboratories Layered Space Time（V-BLAST） system with feedback delay. The aim of proposing this algorithm is to minimize the overall Bit Error Rate（BER）. At the receiver, Zero Forcing（ZF） detection technology is proposed and assuming that full channel state information can be obtained. The transmitter gets the information through a time delay feedback link. The algorithm computes the conditional Probability Density Function（PDF） of the real Signal Noise Ratio（SNR） according to the PDF of the SNR estimation, and the overall BER expression is worked out. At the transmitter, the transmit power of each antennas is obtained by solving the optimization problem under the total power constraint. Simulation results show that the proposed ATPA algorithm can effectively improve the BER performance. It is proved that if the performance requirement of BER=10^- 3, the normalized feedback delay factor is equal to 0.000 1, the modified V-BLAST system with adaptive transmit power allocation outperforms the conventional V-BLAST system about 5 dB when the feedback links with a delay.