Experimental Evaluation of UL-NOMA System Employing Correlated Receive Diversity

Abstract

The number of Internet-of-Things (IoT) devices will increase rapidly. In next generation mobile communication systems, base stations (BSs) must effectively accommodate signals from massive IoT devices. In addition, some IoT devices will require low latency communication for quasi-real-time control systems. Hence, we have proposed a low latency no-orthogonal multiple access (NOMA) uplink system named the system simultaneous transmission access boosting ultra-low-latency (STABLE). We employed successive interference cancellation (SIC) for NOMA. We have also researched a receive space diversity (SD) which combines signals in a frequency domain to enhance system reliability. This paper shows experimental results when 5 users simultaneously transmit signals to a BS. We conducted two types of experiments, using a fading emulator and in the real field. In the fading emulator experiment, we evaluated the effect of antenna correlation on SD and investigated appropriate SIR for SIC. We confirmed that SD was effective even if the correlation is 0.8 and that appropriate SIR was about 4 dB when 5 users suffered from fading. From the results of the real field experiment where 3 fixed users and 2 mobile users sent signals, we confirmed that the system without SD could decode 3.5 users’ signals in average while the SD could make the number increase up to 4.1 in average. The antenna correlation is 0.33 in the environment.