In this dissertation the main contents are:(1) By analyzing and summarizing the current researches of cooperative diversity schemes in cognitive radio, we have established the mathematical models of AF (Amplify - and -Forward)、DF (Detect - and - blog lace wedding dresses Forward) and CC (Code Cooperation), focusing on the situation that there is only one relay between source node and destination node. At the same time, we have analyzed and compared the transmission performance of the three cooperative diversity schemes in Rayleigh channel, proving that they could provide cooperative diversity to combat fading.(2) Power allocation method is one of key technologies to put cooperative diversity into practice. It can efficiently improve the useage of resource by blog new shirts 2010 optimizing the transmit power for each user according to channel conditions. Taking the condition of one relay between source node and destination node for example, when the total transmission power keeps the same, we have put forward and analyzed the optimistic power allocation method for wedding gowns dresses and DF by minimizing average bit error rate. (3) We have expanded the condition of one relay to multi-relays, and all the relays arranged in parallel. Then we have established the mathematical models of new shoes 2010、DF and CC, analyzed and compared the transmission performance and application of the three cooperative diversity schemes in Rayleigh channel.(4) People have paid more attention to the transmission of multi-hop new wedding dresses in wireless system. Therefore, when all the relays are in series, we have established the mathematical models of AF、DF and CC, analyzed and compared the transmission performance of the three cooperative diversity schemes in Rayleigh channel.
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