A Feedback Update Control Scheme for Limited Feedback Multiple Antennas Systems

Allowing the receiver in a multiple antenna wireless system to send a limited amount of channel state information (CSI) feedback is an effective way to enable channel adaptive signaling. This paper addresses the problem of controlling the feedback update period and feedback rate of limited feedback multiple antennas systems in temporally correlated channels. The challenge in our problem is how to assign the feedback update period and feedback rate subject to a constraint on feedback overhead. The presented approach analyzes the required CSI feedback rate and feedback update period by maximizing a lower bound on the average normalized effective signal-to-noise ratio. By imposing the channel evolution structure and employing a random quantization argument, we are able to determine a closed-form solution. This result leads to a bound on the feedback rate that characterizes when the proposed feedback update control scheme outperforms the conventional feedback scheme. Both analytical and numerical results demonstrate that the proposed feedback control strategy improves the average effective SNR with a relatively small amount of feedback overhead.