Capacity bounds of transmit beamforming over MISO time-varying channels with imperfect feedback

Abstract

In wireless multiple input single output (MISO) systems, transmit beamforming using feedback of quantized channel state information (CSI) can provide both diversity gain and array gain with simple implementation. Most of previous researches include several ideal assumptions, such as block-fading channels, perfect CSI at the receiver, or error-free and zero-delay feedback link. This paper investigates a more realistic Jakes’ time-varying MISO Rayleigh fading channel with CSI estimation error and feedback delay, derives the upper and lower bounds on the ergodic capacity, and obtains the optimal frame length according to the capacity lower bound given the normalized feedback bits. The numerical and simulation results show that the derived upper and lower bounds on the capacity is quite close, increasing channel estimation error or Doppler spread will reduce the capacity bounds, and the optimal frame length can maximize the capacity lower bound.