Performance Analysis For Multi-Antenna Two-Way Relating Networks

The fading in wireless channel is one of the main factors which affect the reliability and validity for wireless communication systems. In order to improve the transmission signal quality, efficient measures must be adopted to resist channel fading. Relay based cooperative communication is an effective method for resisting fading, though the traditional one-way relay increase the communication range、validity and reliability for the system, it doesn’t make full use of system time resource which results in low spectral efficiency. Two-way relaying is a promising spectral efficient transmission protocol for wireless networks with half-duplex terminals. By using network coding at the relay, where multiple data streams arriving from multiple sources are mixed or network-coded before being broadcasted, the transmission phases required is reduced, resulting in an improved spectral efficiency. On the other hand, the combinations of multi-antenna technology with two-way relaying can further improve the system performance. The paper focus on the three key technologies for multi-antenna two-way relay system, such as relay selection、limited feedback beamforming、antenna selection, combining performance analysis and power allocation schemes, and mainly study the performance analysis and optimizations problem for different transmission strategies under different scenarios.The main contributions of this paper can be concluded as follows:(1) Performance evalution for the relay selection strategies in AF two-way relaying networking. We studied the performance analysis and optimization problem for AF TWRNs with opportunistic relay selections (ORS) over two-wave with diffuse power (TWDP) fading. For two-way relaing transmitting symmetric data, we derived an easy-to-compute expression for the exact outage probability to provide a convenient and accurate approximation at first.Then compact expressions for the asymptotic outage probability and asymptotic SER were derived, from which we can conclude that the diversity order is determined by the number of relays, while the coding gain is tightly related to the channel fading scenario and the number of relays. Besides, we have also proposed an optimal power allocation scheme which shows that the power should be shared equally between the sources on one side and the relay on the other side in order to minimize the overall outage probability. For the situations transmitting asymmetric data, we study the outage performance under different transmission rate for the two sources.Simulation results verify the theoretical derivations. Our resulting expressions are applicable for TWRNs over TWDP channels, and remain valid in Rayleigh and Ricain fading scenarios.(2)Performance analysis for limited feedback beamforming (LFBF) based two-way relaying.We study the performance of fixed DF two-way relay cooperative networks with multi-antenna sources employing LFBF for signal transmission. Firstly, we devire the overall outage probability expressions for the proposed LFBF protocol using under Rayleigh fading channel. Then the expressions of the sum symbol error rate are derived. Further, an optimal power allocation scheme which minimizes the OOP is proposed. Both the theoretical and numerical results demonstrate that LFBF can achieve well performance while it is less complex and less expensive to implement. Also, it can be concluded that the proposed optimal power allocation scheme provides obvious gain to system performance.(3)Studies for joint relay-antenna selections for multi-relay multi-antenna two-way relay networks. For the characteristics that the system have centralized antenna and distributed nodes, we propose the transmission schemes which combining relay selections and antenna selections, and analyze the transmission performance for the porposed schemes.For AF multi-antenna multi-relay TWRNs, we present a joint relay-and-antenna selection and power allocation strategy. In our approach, we firstly obtain the closed-form solution for optimal power allocation, then with the optimal allocation solution we proposed a joint relay-and-antenna selection scheme with low feedback spending and computation complexity. At last, the overall outage probability is investigated under the optimal power allocation and a tight closed-form approximation is derived which provide a method to evaluate the outage performance easily and fast.For DF multi-relay multi-antenna TWRNs, we propose two novel joint relay-and-antenna strategies are proposed. Specifically, we extend the two major relay selection schemes for the DF protocol: opportunistic relaying (OR) and selection cooperation (SC) to multiple-relay MIMO DF TWRNs, and combine them with TAS. Then we get two schemes, namely, joint OR-TAS (Opportunistic Relaying Transmit Antenna Selection) and joint SC-TAS (Selection Cooperation-Transmit Antenna Selection). For each joint selection scheme, the best transmit antenna at the two sources, a best relay, and a single best antenna at the selected relay are jointly determined in an optimum sense. The performance of these strategies is quantified by deriving the overall outage probability. For OR-TAS, we derive its outage probability directly, while for SC-TAS, we obtain its outage probability by proving that it is identical to that of OR-TAS.