LAUSR

This letter presents a set of 60 GHz multiple-input–mutiple-output (MIMO) channel measurements to investigate the diversity gain in an underground mine. A 2 × 2 MIMO propagation measurements were performed in line-of-sight (LOS) within an underground gold mine to investigate the frequency selectivity in the 57–64 GHz band. The measured coherence bandwidth and the excess delay were evaluated to determine the optimal subcarrier spacing and cyclic prefix length of multicarrier systems. A space-time block coding (STBC) based on an orthogonal frequency-division multiplexing scheme is then evaluated to determine the MIMO diversity gain. It is shown that the diversity gain through STBC enhances significantly links reliability in an underground channel and, therefore, the spectral efficiency and achievable data rates. The results and inferred conclusions are valuable in implementing the next-generation 60 GHz IEEE802.11ay and the upcoming 5G new radio-unlicensed links in underground mines.