No abstract

This paper proposes a high performance wireless commmunication technology in MU-MIMO systems. The millimeter wave (mmWave) communication technology was considered for the future wireless communication systems such as the fifth-generation new radio (5G NR). In 5G NR, the mmWave communication technology was studied to increase the use of wide bandwidth and the data rate. Therefore, MU-MIMO systems can be used in mmWave. To decrease the complexity of conventional digital beamforming system, the hybrid beamforming system was studied. In particular, the proposed hybrid beamforming system improves the error performance and average sum rate in partially connected structure (PCS) hybrid beamforming system. The proposed PCS hybrid beamforming system forms variously combined beam patterns using the information of azimuth and elevation angles for the multi-paths according to the number of bits. In addition, the azimuth and elevation angles among the formed beam patterns are estimated according to the received signal strength (RSS). In the simulation results, the proposed PCS hybrid beamforming system has better error performance and the average sum rate than the conventional hybrid beamforming system.

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Cooperative communication is a novel approach utilizing limited resources to get reliability. However, overall transmissionrate is reduced to have decomposable composition at the destination node in time-division multiple access (TDMA) system, which diminishes the advantage of cooperation. Recently, a novel use of layered modulation and an adequate cooperative space-time block code (C-STBC) were proposed to solve this drawback. Even though it provided certain level of diversity gain without transmission-rate loss, there is room for improvement. In this paper, we enhance it through the constellation modification and adaptive cooperation schemes. Their effectiveness is evaluated for the multiband orthogonal frequency-division multiplexing (MB-OFDM) system.