Impact of Limited Feedback on MIMO-OFDM Systems Using Joint Beamforming

摘要

In multi input multi output antenna systems, beamforming is a technique forguarding against the negative effects of fading. However, this techniquerequires the transmitter to have perfect knowledge of the channel which isoften not available a priori. A solution to overcome this problem is to designthe beamforming vector using a limited number of feedback bits sent from thereceiver to the transmitter. In the case of limited feedback, the beamformingvector is limited to lie in a codebook that is known to both the transmitterand receiver.When the feedback is strictly limited, important issues are how toquantize the information needed at the transmitter and how much improvement inassociated performance can be obtained as a function of the amount of feedbackavailable.In this paper channel quantization schema using simple approach tocodebook design (random vector quantization)is illustrated. Performance resultsshow that even with a few bits of feedback, performance can be close to thatwith perfect channel knowledge at the transmitter.