Downlink Multiuser Superposition Using QPSK and 256-QAM in Mobile Communication Systems

Non-orthogonal multiple access (NOMA) is a potential candidate for the 5th-generation mobile systems (5G). In NOMA, two types of modulation signals are superposed for two different user equipment (UEs) in the power domain. The use of higher-order modulation such as 256-QAM is an also important technique under consideration for 5G. In this paper, we propose superposed modulation using QPSK and 256-QAM for downlink NOMA, and demonstrate the performance by link-level simulation under static propagation condition. The BER performance is investigated for the “superposed QPSK and 256-QAM” transmission as parameters of power allocation sets. From these results, we clarify the requirements for paired NOMA UEs when the superposed QPSK and 256-QAM is used in downlink NOMA.