Performance Analysis For Mulit-antenna Relay Network

Relaying technologies have attracted considerable attention due to their promising potential of increasing the coverage and improving the system performance. In order to enhance the capacity of the relay network, using multiple antennas at the transmitter and/or receiver has been identified as a key enabling technique for future generation networks. How to analyze and measure the system per-formance of multi-antenna relay system is the fundamental problem. Based on the multi-antenna relay networks model, we investigate the system performance of one-way amplify-and-forward (AF) relay networks and two-way AF relay net-works in practical applications including antenna correlation, channel estimation errors, feedback delay, and multiple co-channel interferers. Specifically, the main contributions of this thesis are summarized as follows:1. For antenna correlation, we investigate the performance of antenna selec-tion/multiuser Opportunistic scheduling two-way amplify-and-forward (AF) re-laying system. We consider the case when there is antenna correlation at the base station (BS). A single multi-antenna base station exchanges informantion with mul-tiple single-antenna users via a single-antenna relay station over a Rayleigh flat-fading environment. The lower bound expression for outage probability and the sum rate are derived. To gain better insights and identify key parameters, the asymptotic expressions of the sum rate are analyzed for the symmetric and asym-metric properties of the practice relay channel when the number of mobile stations K is sufficiently large. Analysis and simulation results indicate that the achievable sum rates depend on the degree of spatial correlation and the number of mobile stations K. Especially, our results reveal the impact of the relay location with unbalanced hops on the sum rates.2. For channel estimation errors (CEE) and feedback delay (FD), we investi-gate the outage performance and average bit error rate (BER) of multiple-input multiple-output (MIMO) two hop beamforming AF relay networks. To quantify the effect of CEE and FD on our considered network, we derive the closed-form expression for the outage probability and average BER. To gain more insight, we also present an asymptotic analysis for the outage probability and average BER in the high-SNR regime, which provides the details of the diversity order and array gain, and insightful discussions and observations on the impact of CEE and FD on the system are presented. Through our works, one can see the effect of CEE and FD on the system as well as the benefits of deploying multiple antennas at the terminals. Our results show that both CEE and FD degrade significantly the system performance, and there is no diversity gain improvement even though multiple antennas are employed at the source and the destination. Numerical and simulation results are provided to verify the analysis and compare the performance of the considered network for two different models for channel estimation error.3. For co-channel interferers (CCI) and imperfect channel state information (imperfect CSI), we investigate the performance of transmit antenna selec-tion/receiver maximal-ratio combining (TAS/MRC) in a dual-hop MIMO AF re-lay network. We consider a more general scenario, where all nodes are affected by co-channel interference and all the nodes are equipped with multiple antennas. Motivated by this system model, a new type of end-to-end signal-to-interference ratio (SIR) expression is obtained, based on which the tight lower bound and asymptotic expression for the outage probability are derived. The diversity or-der and coding gain of the system with/without imperfect CSI in the presence of multiple CCI is further discussed. Through our work, we can see that interference signals do not provide any diversity gain but worsen outage performance with increasing number of antenna at terminal. Only under the effect of interference, the diversity gain is Gd= Nrmin(Ns,Nd). However, under the combined effects of interference and outdated CSI, the imperfect CSI has a significant detrimental effect on the outage performance, and the diversity gain reduces to min(Nr, Nd), Nr and min(NsNr, Nd) as ρ1< 1 and ρ2< 1, ρ1< 1 and ρ2= 1, and ρ1= 1 and ρ2< 1, respectively. Numerical and simulation results are presented to validate our analysis and to demonstrate the effect of outdated CSI and multiple CCI on the system performance.