Research On Cooperative Relay For Wireless Communication Systems

Cooperative relay is a cooperative multiple antenna technique, which can significantly increase data rate and reliability of wireless link, and can enlarge the coverage and improve the robustness of the systems.Cooperative relay is mainly based on the nature of broadcast, which can reduce the consumption of energy, bandwidth of the terminal, and can also significantly improve the spectral efficiency, throughput, and the capacity of the system. To date, cooperative diversity has been widely used in wireless sensor networks, wireless Ad hoc networks, wireless Mesh networks, and wireless cellular networks. Obviously, cooperative communication will be the key technology for convergence of various heterogeneous networks, so, in this dissertation we will consider the special issues of cooperative relay communication.Outage probability and error symbol rate (SER) are two mostly used performance metrics for wireless communication sytstems. For outage probability and SER performance analysis of amplify-and-forward (AF) and decode-and-forward (DF), the traditional methods are based on approximation at high signal-to-noise ratio (SNR) for the exact expressions are still unknown at arbitrary SNR regime. Accordingly, we investigate the performance of outage probability and SER for DF diverstiy protocol of Rayleigh fading channel. We first derive the closed-form expression for outage probability of DF through analysis of the distribution of the linear function of two independent exponential random variables. We further use movement generation function (MGF) method to obtain the closed-form expression of symbol error rate for system based on MPSK modulation. The simulations reveal that the analytic results are exact the same with the numeric result at arbitrary SNR regime. The proposed expressions of outage probability and SER are of great value for investigating special issues associated with DF diversity protocol.Based on the feedback of all channels, choosing the higher achievable rate transmission mode between decode-and-forward (DF) and direct transmission (DT) can derive an outage minimization system. In order to reduce feedback overhead and computation complexity, on the channel gain coordinates plane, we first investigate the division of optimal transmission mode region. Accordingly, the destination can easily derive the transmission mode by checking the optimal transmission mode region of the channel state information. Then, we can further reduce the outage of the system through feedback the parameter of power allocation. Based on the proposed algorithm, the destination only needs to feedback a transmission parameter to the source and the relay, which can derive an outage minimization strategy.Hunter et al. first combined cooperative communication with existing channel coding methods, and proposed coded cooperation (CC) strategy based on rate-compatible punctured convolution (RCPC) code. Based on CC scheme, the codeword is divided into different parts, which arrive at the base station through different fading channels. In their system model, they consider that the pairwise error probability (PEP) is only proportional to the length of the corresponding symbol part while neglecting the influence of different channel quality, which is unreasonable in many practical scenarios. There is no need to transmit data for a user in the cooperative frame when the based station can recover the user's data only based on the direction transmission. Thus, through the investigation of codded cooperation, we propose a new codded cooperation strategy, which is based on limited feedback from the base station. The base station feedback the decode result of the direct transmission to the users, and then the users adaptively change the data transmission in the cooperative frame. The simulation results reveal that our proposed scheme achieves impressive gains in contrast with the existing cooperative schemes, while not only saving considerable power and bandwidth but also improving the throughput and spectral efficiency.In wireless cooperative systems, the cooperative node should adjust data packet transmission and data packet reception with high flexibility, then, we need a scalable and compatible algorithm for the implementation of the cooperative node. Thus, based on the module design scheme, we first propose a transparent sending mechanism, which could adjust the sending data packets format by means of bitmap. Next, we propose an optimal adaptive data receive mechanism for multiple channels in a round robin fashion from multiple cooperative nodes. Based on the proposed mechanisms, only modifying several variables can support any data transmission and data reception protocols of cooperative node. The proposed mechanisms not only fit for wireless communication system but also for any systems with similar requirements. Based on the high speed serial transceiver technique, the algorithms have been applied in B3G TDD system.From the dissertation we can find that, in cooperative communication system, selecting suitable cooperative schemes and data processing algorithms for specific transmission strategies can make full use of antennas of different user terminals, and thus achieve cooperative diversity, which can significantly improve the performance and reduce the cost of the systems.