Link adaptation method based on mutual information for BDMA massive MIMO transmission system

Massive Multiple-Input and Multiple-Output (MIMO) technology that employs a very large number of antennas at the base station (BS), serves relatively fewer users jointly and simultaneously. Adaptive transmission technique in a large-scale MIMO wireless communication systems, can further enhance the reliability of the transmission links and improve the spectrum efficiency. This paper is based on beam division multiple access (BDMA) transmission scheme that simultaneously serves a small number of users via different beam set. We first introduce the massive MIMO model, then propose an effective adaptive transmission method to select channel quality indicator (CQI) parameter. In the proposed scheme, user equipment (UE) is required to calculate the mutual information (MI) between the finite discrete constellation input and the corresponding output over complex-valued vector channels, and compare with different mutual information thresholds, then feed back a CQI for each codeword to signal the supported adaptive modulation and coding scheme (MCS) to satisfy a given target codeword error ratio (CWER) constraint. Finally, simulation results show that the proposed adaptive transmission method combined with iterative receiver can obtain a high spectral efficiency while guaranteeing the given CWER target.