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.