Study On The Relationship Between The Relay Node Mobility And Collaboration Mode Of

Third generation mobile communication (3G) technology has been commercially available on a global scale, it has brought people a relatively higher rate of internet access. and compared with the second-generation mobile communication technology, it has great progress. But people demands higher-speed, wide range of network coverage, multi-service and low cost. So the fourth generation mobile communication systems have been attracted people’s attention. Cooperative relay network is an economic and new network architecture, in which the direct link between the base station and terminal is divided into two-hop or multi-hop transmission link, can improve the efficiency and quality of communication between the traditional station and base, and also expand its wireless network coverage. So it was used in the next-generation wireless mobile communication network for a wide range of coverage and higher-speed transmission. Cooperative communication technology is current research focus. This thesis focus on the origin background of cooperative communications technology. antenna diversity, methods of cooperative diversity and the effect brought by the movement of cooperative relay in the network.Firstly, this thesis introduces the origin and development, including antenna diversity and merge technology. and then gain expressions of the diversity combining technologies (maximum ratio combining, equal gain combining, selection combining and switch combining) are derived and analyzed. Secondly the basic principles of cooperative communication and several collaborative approaches are analyzed. According to signal processing methods in the relay node. cooperative diversity is divided into three strategies including fixed relaying, incremental relaying and selection relaying. Based on the theoretical knowledge of information theory. mutual information and outage probability formulas of each cooperative diversity method are derived. In this paper, our modulation has only one single relay, and the two classical methods:amplify and forward (AAF) and decode-and-forward (DAF) are used as examples to research the effect brought by the movements of the relay in networks. And the performance of several diversity combining technologies are showed in the thesis to compare their performances. Simulation results show that the maximum ratio combining (MRC) has the best anti-fading characteristics compared with other combing technologies. We also found that cooperative communication gets the best performance and lowest bit error rate (BER) when the position of the relay is in the midpoint between the source and destination. After many modulation results are compared and analyzed, we found that in order to get some cooperative diversity gain, the location of the relay should be roughly in a an elliptical region between base and mobile, otherwise the cooperative communication is not necessarily to improve the system performance. In conclusion. various locations of the relay in the networks can bring different impact on the networks. which can provide useful theory and data supports for relay selection.