Researches On Schemes Of Cooperative Diversity In Wireless Communication Systems

In wireless communication systems, the signal of wireless channel is impaired by the random fluctuations across space, time and frequency. The diversity is a powerful technology to combat the fading. Space or multi-antenna diversity techniques are particularly attractive as they can be readily combined with other forms of diversity, e.g., time and frequency diversity, and still offer dramatic performance gains under these bases. One of the traditional technologies of space diversity is antenna array, which is studied and utilized in 3G and beyond 3G systems , e.g., MIMO (Multiple Input Multiple Output). Due to the size, energy, cost limitations, the deployment of antenna array is difficult to realize. Recently a brand-new solution scheme is put forward basing on the user cooperation, relay cooperation, or antennas cooperation etc. which is called cooperative diversity technology. The essence of this technology is that users in a group sharing their antennas and resource through distributed process and transmition to form a "virtual array", forming the virtual MIMO system. This dissertation develops the research according the schemes starved for the solution to cooperative diversity.The characteristic of cooperative diversity is introduced at first in this dissertation and the current research situation is present . Some questions need to be further solved are summarized.The basic two schemes of cooperative diversity, AF (Amplify-and-Foreword) and DF (Decode-and-Forward) are studied deeply at the second part of this dissertation. The performance and realization are studied in detail. Also the theoretic analyses and simulations are presented .The comparison between AF and DF is list deeply . Also comparisons between AF and some other corresponding MIMO technologies are done. Aiming the DF model, the analysis is given about the relay nodes with CRC (Cyclic Redundancy Check) and without CRC . About the power allocation of AF model, the method of combining the transmit-MRC and MRC at the receiver is put forward to allocate the power jointly.Aiming the frequency selective fading channel, the multi-carrier cooperative diversity is put forward. The system of cooperative differential detection OFDM (Orthogonal Frequency Division Multiplexing), combining the differential detection OFDM and the cooperative diversity, is put forward. Also the performance is analyzed. The selection of cooperative partner based velocity and distance is a key problem. The method of partner selection based on BER is discussed and used into the V2V system.Aiming the increasing of the communication of multimedia, a new distributed scheme is put forward. Only the main part through DCT and recombined is transmitted cooperatively, at the little performance cost, the energy and the frequency band are saved.In the cooperative network, the selection of cooperative partner is a very key problem all along. All the former solutions to this problem in essence base on the performance of the transceiver while neglecting the fairness among the cooperative partners. In the end, a new scheme through cross layer design to obtain the dynamic balance among the performance, the fairness and the lifetime of the network. So it is advantage of the fairness of the network.