| Fading is the primary factor which encumbers the increasing of wireless channel capacity and improving the quality of service. MIMO technique is the most effective method to cope with fading. However, in MIMO system, each node must be equipped with multiple antennas, which is uneasy to be applied in reality. Cooperative communication is exactly under this kind of background to emerge with the tide of the times. The concept of cooperative communication is based on relay channel model and inspired by MIMO technique. In cooperative communication, the wireless channel, wireless networks and physical layer techniques are integated for designing and optimizing, which brings many merits. Such as increasing wireless channel capacity, decreasing the outage probability, improving the connectivity in wireless networks and minimizing energy consumption. Cooperative communication is not just a technique, it can be regard as a method of communication, a kind of thought. Cooperative communication can inosculate with other techniques and be broadly applied in wireless communciation. Cooperative communication is becoming one of the most important theme in next generation research field on wireless communication.With a view to the design of strategies and protocols, this thesis focuses on four key problems in cooperative communication. First, investigate how to choose the appropriate protocol based on the spatial distribution of relay nodes. Then, analyse the relationship between cooperative communication and interference problem and how should cooperative communication cope with the interference problem. Aiming at heterogenous cooperative communication, a new research field in cellular networks, this thesis analyzes two cooperative modes and the corresponding performances can be achieved. In the end, a MAC layer protocol which can support cooperative communication is introduced, and its feasibility is verified by simulation results.The contributions of this thesis include:1 Recur to geometric analysis and information theoretic formulas, it is proved that which cooperative protocols can bring larger maximum mutual information has tight relation with the spatial distribution of relay nodes. Then, a strategy for cooperative protocols selection based on spatial distribution of relay nodes is given. Next, an opportunistic dis- tributed space-time coding cooperative protocol is introduced, which can achieve the tradeoff between better performance and complexity.2 The interference induced by relay nodes has effects on the system performance and it can be mitigated by choosing different relay nodes. A relay assignment algorithm with interference mitigation is provided, where the nodes can utilize the opportunity caused by interference to negotiate, looking for more suitable relay nodes. The simulation results verify that this new relay assignment algorithm can enhance average wireless channel capacity by 7%.3 Introduce two cooperative modes: VAA_DSTC and VAA_BLAST, which are suitable for heterogenous cooperative communication. Describe the work flows of these two modes and utilize diversity-multiplexing tradeoff (DMT) to evaluate the performances of them. Put forward and prove that the difference between heterogeneous interfaces of mobile equipment can bring extra multiplexing gain.4 Introduce an generic architecture which can support cooperative communication and investigate a cooperative MAC layer protocol compatible with legacy MAC layer protocol of 802.11. This cooperative MAC layer protocol can support different cooperative protocols and different number of relay nodes. Moreover, this cooperative MAC layer protocol concerns how to mitigate interference problem by selecting different relay nodes.The entire works of this thesis are exploring four key problem in cooperative communciation, which is helpful for the reseach on cooperative communication from theory to practice. The research will accelerate the pace of research on cooperative communication, has forward-looking in theory and practicability in reality.
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