Enhanced Transmit Antenna Selection Using OSTBC Scheme with SVD-Based Hybrid Precoding for 5G Millimeter-Wave Communications

Transmit Antenna Selection using Orthogonal Space-Time Block Codes (TAS-OSTBC) aided Millimeter-wave (mmWave) communications is proposed in this paper. The TAS transmitter is characterized by a lower number of Radio Frequency (RF) chains than the number of transmit antennas, hence it is capable of reducing both the energy consumption as well as the transmitter cost. The proposed scheme combines TAS-OSTBC system with Hybrid Analog-Digital Beamforming for 60 GHz mmWave communications and using Hadamard transform. The computer simulation results demonstrate that the TAS-OSTBC scheme with fully digital SVD-based precoding has better Bit Error Rate (BER) performance than that of the conventional TAS system with OSTBC scheme. Furthermore, the error performance is significantly improved by applying Uniform Linear Array (ULA) antennas which improve the system performance as the number of array elements increases due to providing a beamforming gain. It is also found that the BER performance is further improved by applying Hadamard transform with an SNR improvement of about 3dB over the conventional systems without using Hadamard transform.

I. Introduction

In Multiple-input Multiple-output (MIMO) systems, the data rate enhancement is normally associated with extra complexity, size and high cost in the system hardware design since a Radio Frequency (RF) chain is required to be connected to each antenna port. To circumvent this issue, a subset of antennas can be selected for transmission. Such technique is called Antenna Selection (AS) which can reduce the cost and attain many of the advantages of MIMO systems. Transmit Antenna Selection (TAS) is one of MIMO categories where a subset of the transmit antennas are activated for transmission, and retaining a full diversity benefits as if all the transmit antennas were in use [1]. The most well-known TAS scheme where an Orthogonal Space-Time Block Code (OSTBC) is used along with the optimal subset of transmit antennas has been proposed by Gore and Paulraj in [1]. A rapid development has been gained and a closer research attention has been paid for TAS systems since it was proposed. However, in order to exploit the benefits of TAS and OSTBC systems, both have been combined to improve the multiplexing gain and the diversity gain simultaneously, and to reduce the number of RF chains in order to reduce the transmitter cost [2]. In this system, OSTBC signal matrices are transmitted over a selected subset of transmit antennas, which is a practical technique for achieving a full diversity order. However, two transmit antennas out of total antennas are selected for transmission [3], [4], and hence only two RF chains are required.