Nonorthogonal Random Access for 5G Mobile Communication Systems

This correspondence paper proposes two nonorthogonal random access (NORA) techniques for 5G mobile communication networks, where user equipments (UEs) make use of the channel inversion technique such that their received power at the base station (BS) can be one of the two target values. It enables the BS to decode two packets simultaneously with the successive interference cancellation (SIC) technique if a different power level is chosen. We propose two NORA systems; that is, UEs choose one of the two target power levels based on the channel gain or the region where they are. The performance of the proposed systems is analyzed in terms of access delay, throughput, and energy efficiency. Through analysis and extensive computer simulations, we show that the maximum throughput of the proposed NORA techniques can exceed 0.7, which is a significant improvement compared to the maximum throughput of conventional random access 0.368.