Performance Analysis of Cooperative Relay Networks with Multiple Source and Destination Antennas

Abstract

Cooperative communications use one or more relays to forward signals transmitted from the source to the destination. In recent years it has received considerable attention for increasing the reliability of wireless networks, because it is a way to obtain diversity using distributed relays. Several researchers have investigated the performance of cooperative communications over fading channels using the derived expressions of outage probability. The outage probability, defined as the probability that the output signal-to-noise ratio (SNR) or mutual information falls below a specific threshold value, and has been used extensively as a way to measure the systems over fading channels. Various cooperative relay networks have been proposed in multiple relays scenario with single source and destination antennas, such as distributed space-time coded cooperative relay networks and cooperative relay selection. In the distributed space-time coded cooperative relay networks, multiple relays decode the source signal and retransmit distributed space-time coded source signal to the destination. In cooperative relay selection, one of multiple relays is selected to retransmit the source signal to the destination. The diversity-multiplexing tradeoff of the cooperative relay selection was identical to that of the more complex distributed space-time coded cooperative relay networks. In this dissertation, to improve the end-to-end outage performance of cooperative relay networks, we consider multiple source and destination antennas based on the cooperative relay selection. We expect the system to obtain additional transmit diversity gains on the outage probabilities from source antennas to relays using space-time block code (STBC) without loss of rate and additional receive diversity gains on the outage probabilities from relays to destination antennas using maximal-ratio combining (MRC). After we describe the system model for the cooperative relay networks with multiple source and destination antennas, we derive an exact closed-form expression of the outage probability for the proposed system over independent and identically distributed (i.i.d.) Nakagami-m fading channels. It has great flexibility and accuracy in matching various experimental data and represents a wide variety of realistic line-of-sight and non-line-of-sight fading channels encountered in practice. The i.i.d. Nakagami-m fading channels from multiple source antennas to the relay and from the relay to multiple destination antennas for a fixed relay have same values of fading parameters. To analyze the diversity order of the proposed cooperative relay networks, we present the diversity-multiplexing tradeoff for the proposed system over i.i.d. Nakagami-m fading channels. We then analyze the effects of number of source and destination antennas on the outage probability and diversity-multiplexing tradeoff. We extend the proposed cooperative relay networks to independent and non-identically distributed (i.n.i.d.) Nakagami-m fading channels. It does not have necessarily the same values of fading parameters for all links. We derive the exact expression of outage probability for the cooperative relay networks with multiple source and destination antennas over i.n.i.d. Nakagami-m fading channels. To analyze the diversity order of the proposed system with different numbers of relays, source antennas, and destination antennas, we describe the diversity-multiplexing tradeoff over i.n.i.d. Nakagami-m fading channels. We then analyze the effects of various parameters such as fading conditions, number of relays, and number of source and destination antennas on the outage probability and diversity-multiplexing tradeoff. This dissertation contributes the guidelines of system design and architecture for cooperative communications with the effects of fading conditions, number of relays, and number of source and destination antennas. From the derived exact expressions of outage probability and diversity-multiplexing tradeoff, we have the insight into the design of practical cooperative relay networks such as mobile multi-hop relay networks, wireless ad-hoc networks, wireless mesh networks, and wireless sensor networks. The hardware implementation of radio and network is an important and fruitful area for future research on cooperative relay networks and related topics.