A New Designed MIMO-NOMA Scheme for HSR System with Distributed Antennas

This paper investigates the MIMO-NOMA transmission scheme for high-speed railway (HSR). To the best of our knowledge, this is the first work that attempts to implement NOMA principle into HSR wireless system. Attracted by the technological superiority of distributed antenna system (DAS) and MIMO-NOMA, we propose a new transmission scheme and compare it with the conventional transmission strategy. We treat each antenna unit of the distributed antenna system as an independent user, group these users at each time slot, and apply NOMA principles within each group. We adopt a simple method to ensure that users with large channel state differences are grouped into the same cluster, and introduce average service rate to measure the system performance. At the same time, we have discussed the effect of fixed power allocation and dynamic power allocation on the system transmission rate within MIMONOMA and MIMO-OMA. The simulation results illustrate that the dynamic power allocation scheme is superior to the fixed power allocation, and the MIMO-NOMA system we proposed is always superior to the conventional MIMO-OMA scheme in high speed railways.