Joint SNR Target and Rate Adaptation Based on Bit Error Rate Estimation

We derive the joint optimisation of signal-to-noise (SNR) target and rate adaptation for maximum spectral efficiency based on a bit error rate (BER) estimate. We consider a code division multiple access (CDMA)-based system with two levels of power control: channel inversion or truncated channel inversion is used for the fast inner-loop power control, and SNR target setting in the outer-loop is performed jointly with transmit rate adaptation based on the estimate of BER. We use the joint distribution of the channel gain and its estimate to obtain maximum likelihood estimation of the BER. We show that our proposed scheme achieves higher spectral efficiency when compared to an adaptive rate and power scheme with fixed SNR target.