Efficient antenna selection schemes for MIMO systems

Abstract

Multiple input multiple output (MIMO) is a technique that refers to the use of multiple antennas both at the transmit and receive ends of a wireless link. MIMO technologies can improve the throughput and reliability of a radio system. Given the nature of MIMO, it is not limited to wireless communications, and it can be used in radar applications as well. This thesis studies the MIMO signal processing strategies for both wireless communications and radar applications. Major limiting factors in the deployment of MIMO systems are the physical limitation of wireless devices and the cost of the multiple radio frequency (RF) chains (such as low noise amplifier, mixers and A/D converters). Antenna selection is considered as a low-cost low-complexity alternative. In this thesis, we focus on the antenna selection schemes to capture the advantages of MIMO systems such as diversity gain and spatial multiplexing gain with reduced RF hardware complexity. Furthermore, we apply the MIMO techniques to radar systems in order to improve the detection and resolution performances. To begin with, we investigate two efficient join transmit and receive antenna selection algorithms to maximize the channel capacity for different degrees of channel state information (CSI) available at the transmitter side. The proposed CSI-based and channel correlation information (CCI) based schemes can achieve near optimal capacity performance with a much lower computational complexity compared to the optimal full search scheme both in practical uncorrelated and correlated scenarios. Based on the error rate selection criterion, we develop antenna selection algorithms and performance analysis for a spatial multiplexing system with linear receivers and for space-time block coded systems with single-symbol maximum likelihood detection. Since practical systems usually need both multiplexing and diversity advantage, we combine adaptive transmit antenna selection with adaptive modulation for a spatial multiplexing system to maximize the average spectral efficiency (throughput) for a given bit error rate constraint and to lower the hardware in complexity. In addition, we present performance analysis for space-time block coded systems with complex orthogonal designs (CODs) and generalized coordinate interleaved orthogonal designs (GCIODs). We then use these results to develop antenna selection algorithms. These are either based on minimizing error rate or maximizing the received SNR criterion. At last, we extend the MIMO concept to radar systems and investigate the potential gains of a MIMO radar. Two system models are studied to explore the spatial diversity gain and resolution gain, respectively. With proper design of the transmitted signals and antenna configuration, MIMO radar systems yield higher performance in target detection, range resolution and angular resolution.