时变信道中非理想反馈条件下波束成形的误码率分析

在基于信道信息有限反馈的无线多入单出系统中，发射机可采用简单的波束成形技术实现发射分集增益和阵列增益。已有的相关研究大多包含块衰落信道、准确信道估计或无反馈延迟等理想假设。该文建立了更为实际的Jakes时变信道中存在信道估计误差和反馈延迟的系统模型，分析了方形和矩形正交幅度调制星座图的平均误码率。研究表明：误码率的理论分析和仿真结果完全相符；增加反馈比特数可提高阵列增益，但不能增加分集增益；在慢变信道中，波束成形要显著优于正交空时分组码；误码率受信道估计误差和反馈延迟影响，且对后者尤为敏感。

BER of Beamforming with Imperfect Feedback over Time-Varying Channels

In wireless Multiple-Input Single-Output (MISO) systems with limited feedback of channel information, transmit beamforming can provide both transmit diversity gain and array gain with simple implementation. Most of prior research includes several ideal assumptions, such as block-fading channels, perfect channel information at the receiver, or error-free and zero-delay feedback link. This paper investigates a more realistic Jakes’ time-varying channel with estimation error and feedback delay, and analyzes the average Bit Error Rate (BER) of the system with square/rectangle Quadrature-Amplitude-Modulation (QAM) constellations. The results show that the analyses are fully consistent with simulations, increasing feedback bits only brings array gain while no diversity gain to the system, beamforming outperforms orthogonal space-time block coding remarkably in slow fading channels, the BER is affected by both channel estimation error and Doppler spread, especially sensitive to the latter.