Experimental Evaluation of UL-NOMA system with FD-STBC

In this paper, we propose a novel uplink non-orthogonal multiple access (UL-NOMA) for massive communications under the number of user equipments (UEs) that send signals simultaneously is larger than the number of receive antennas. The base station (BS) separates the superimposed signals through minimum mean square error (MMSE) spatial filtering with successive interference cancellation (SIC). In order to improve the signal separation performance, frequency domain-space time block coding (FD-STBC) is adopted as transmit diversity in the uplink. As FD-STBC, we examine two ways of transmit power allocation method for each UE. The proposed methods are evaluated by computer simulations and also experiments, which were performed under condition when up to 6 UEs transmit signals simultaneously. Performance evaluation is given by packet error rate (PER) by sending 16 bytes a packet as the signal. The results of the computer simulation and the experiments show good agreement, and the experimental results with the power difference for each UE, show that PER is less than 10% in single transmission without repetition when the number of UEs is up to 6. These are the results when the overloaded ratio, which is the ratio of the number of UEs to the number of the receive antennas, is up to 300%. And these results showed that it is effective to make a power difference for each UE.