SER Reduction in NLOS MM Wave Links Using Minimally Equicorrelated MIMO-MRC System

5G and next-generation physical layer advancements have being made at a breakneck speed. At the heart of it is millimeter wave technology, which uses extremely high frequency transmissions at 28, 38, and 72 GHz. These MM wave channels utilize approximately 20 GHz of spare spectrum to enable faster data rates to a larger number of mobile subscribers. In multiple-input multiple-output (MIMO) systems, transmit beamsteering through directional antenna arrays supported by maximal ratio combining (MRC) receivers is used alongwith MM wave technology to investigate link performance as a function of unfavourable inter-antenna correlations. In this paper, the system is modelled for short-range MM wave communications under separately correlated, non-line-of-sight (NLOS) Rayleigh environments. Here, exact closed form expressions are presented for the symbol error rate (SER) and asymptotic (high signal-to-noise ratio (SNR)) SER of the beamsteered MM wave model. The dependency of SER on transmit-receive correlations is seen in the derivations. The results are analyzed using double-correlated statistics for the maximum eigen value of complex Wishart matrices. Specifically, in the MM wave regime, correlation matrix entries vary with steering/response vectors. This does not hold true in the case of microwave links. It is therefore proposed to effectively adjust these vectors to attain novel minimized equicorrelations at the transmit and receive sides of the MM wave MIMO link. The minimally tuned MIMO-MRC model demonstrates significant average SER and asymptotic (high SNR) SER reductions under both uplink and downlink scenarios with two (02) antennas at the transmitter and receiver, respectively. The proposed model also showcases drastically lower average SER levels compared to those of existing non-equicorrelated systems. Simulation results validate the analytical study.