Robust beamforming and spatial precoding for quasi-OSTBC massive MIMO communications

Abstract

This paper considers the problem of massive multiple-input-multiple-output (MIMO) wireless communication systems with quasi-orthogonal space-time block code (QOSTBC) transmission in the presence of spatial correlation effect (SCE) and mutual coupling effect (MCE). Conventional MIMO channels with QOSTBC transmission suffer from several drawbacks. The number of transmit antennas is restricted to a few in order to achieve full transmission rate. Therefore, it is difficult to make a quasi-orthogonal space time block coded massive MIMO system to achieve full transmission rate. Moreover, MIMO channel with QOSTBC transmission is usually considered for the case where the number of user equipments (UEs) is one. We present a joint beamforming and spatial precoding method to deal with the above drawbacks. The proposed method incorporates a beamforming scheme and spatial precoding to formulate an appropriate optimization process to effectively alleviate the considered problems. The resulting optimization problem will be solved by using a cooperative coevolutionary particle swarm optimization algorithm under two proposed fitness functions. During the optimization process, the proposed method finds the optimal beamforming coefficients of the precoding matrix, the optimal normalized positions of transmit and receive antenna elements for the case of using linear antenna arrays, and the optimal angle differences of transmit and receive antenna elements for the case of using circular arrays. Based on the proposed method, we are able to cure the performance degradation of a quasi-orthogonal space time block coded massive MIMO system due to the SCE and MCE. Moreover, the proposed method makes QOSTBC MIMO communications with full transmission rate for any number of transmit antennas achievable. Several simulation examples are presented to show the superior bit error rate (BER) performances of QOSTBC wireless MIMO scenarios with linear as well as circular antenna arrays by using the proposed method as compared to the existing methods.

Millimeter Wave MISO-OFDM Transmissions in an Intra-Wagon Environment

“…The applicability of quasi-orthogonal STBC (QSTBC) in mMIMO has been analyzed in [15], and the performance of QSTBC algorithms in mmWave at the 94 GHz in indoor environments has been studied in [16]. It has also been demonstrated that QSTBC techniques can be applied in mMIMO [17] together with beamforming techniques achieving full transmission rate for any number of transmit antennas. On the other hand, it is known that in mmWave mMIMO systems hybrid analog and digital beamforming (HBF) based techniques are used to mitigate the effect of the propagation loss and the hardware cost and power consumption [18].…”

“…The authors have chosen these algorithms because these are common and simple techniques to implement in MIMO systems. In future works more complex techniques mentioned above [17], [18], will be applied in mMIMO systems, which will be compared with the ones used in the present paper.…”