Performance Analysis Of Antenna Selection For Multiple-Antenna Technology

Multiple antenna techniques can either increase the capacity or improve the reliability for wireless communication system. To use these techniques, they require the system deploy multiple antenna elements, each with a radio frequency (RF) unit. However, in some application scenarios, it is desirable to have less RF units for the reason of costs, size, complexity or other practical limits. For this reason, antenna selection techniques are proposed, which can improve the communication quality with limited RF. This thesis focuses on antenna selection techniques for diversity system. The main contributions include:1. The performance of selective transmit diversity (STD) with feedback delay was investigated under time varying Rayleigh channel. First, the closed-form expressions of the receiver output signal-to-noise ratio (SNR) distribution are derived and validated via simulation. Based on these results, the average bit error rate (ABER) of BPSK modulation is then obtained. The analytical results show that the BER of STD system consists of two parts:the BER of an ideal STD system without feedback delay plus an error floor caused by delayed feedback.2. An iterative method has been proposed to derive the general formulas of the output SNR distribution, outage rate and ABER for switch and stay combining (SSC) diversity system under time varying flat fading channels. Based on these, the numeral and simulated analyses are given for Rayleigh channel. The results show that the performance of the SSC system increases with the increase of channel correlation in neighboring slots and number of antenna branches. In particular, both SSC and selection combining (SC) have the same diversity order and, for the time invariant channels, the same outage rate.3. A simple adaptive SSC scheme is proposed to avoid the complex search of the optimal threshold. With this scheme, the SSC do not need to know the optimal threshold and the channel distribution. The simulated results show that the performance of the proposed scheme is near to that of the SSC with the optimal threshold under Rayleigh channel.4. A new scheme for transmit antenna selection (TAS) is proposed to reduce the overhead for pilot symbols and feedback signaling. With the proposed scheme, channel estimation is only considered for a subset of all antennas in each slot and such subset will be changed in each following slot. In this way, the overhead can be reduced significantly. Simulation results show that the performance of the proposed scheme is near to that of the traditional ideal TAS.5. A new spatial diversity technique is considered in some scenarios where it is suitable for mechanical movement of antenna. By replaced selecting antenna with selecting spatial location, the proposed technique can save not only the costs of the RF units but also the antennas and feeder cable. Simulation results show that, with the same geographical span, the proposed method can achieve the same or even better performance as that of traditional diversity technique.