Space-time block coded rate-adaptive modulation with uncertain SNR feedback

Channel state information (CSI) at the transmitter can be used to adapt transmission rate or antenna gains in multi-antenna systems. However, the CSI that is fed back will get outdated if the channel is changing rapidly. We propose a rate-adaptive M-QAM technique equipped with space-time block coding with signal to noise ratio (SNR) feedback as opposed to full channel feedback. We obtain closed-form expressions for the average BER and average throughput for our scheme. We illustrate the performance gains achievable through the rate adaptation and possibly delayed SNR feedback. Our numerical results illustrate the immunity of our proposed technique to error caused by time-delayed feedback.