Research On Relay Selection And Network Coding-Cooperation Diversity For Cooperation Communication Systems

With the development of various wireless technologies, the requirement for mobile communications is becoming more and more high. The majority of users are not satisfied with mere voice, text, images and video transmission speed, what we need now is a new communication service with higher quality of service, higher speed, and supporting more business kinds.Cooperative diversity has been recently proposed as a way to form virtual antenna arrays that provide dramatic gains in slow fading wireless environments. Various results show that cooperative diversity can increase the capacity of communication system, higher the data rate, lower the outage probability of service, combat fading effectively, and increase the quality of service and reliability. Cooperative communication is a virtual MIMO technology which provides spatial diversity gain without requiring the establishment of multiple antennas on the source or destination nodes, and thereby boost the transmission performance significantly. Among various cooperative communication protocols, opportunistic relaying scheme is more attractive than others due to the avoidance of coordination among relay nodes and its superior performance. The key technology in opportunistic relaying is the way to select the best relay out of all available relays, which even determines whether the performance gain of cooperation can be obtained. This thesis focuses on relay selection algorithms and explores the ARQ protocol to improve the channel freedom and higher the spectral efficiency of system.Network coding is an important breakthrough in the field of network communication technology which reduces the energy consumption of the network transmission and improve the system capacity. The relay nodes in the network not only store and transmit packets, but also encode the information that passes by. The effective of network coding into cooperative communication can get a better diversity performance at a lower hard cost and a higher spectral efficiency.The main work in this thesis is as follows. Firstly, the theoretical basis and various protocols used in cooperative communications are introduced. The classical relay selection algorithms for cooperative communication systems are summarized. The procedures and existing problems of are analyzed in details. Secondly, in order to solve the problem of collision in opportunistic relaying scheme in actual channel, a spectrally-efficient relay selection algorithm is proposed by applying the ARQ technology and introducing a channel gain threshold and control channels in opportunistic relay communications. The proposed algorithm improves the spectral efficiency and performance gain, and decreases the collision probability of wireless distributed network. Finally, aiming to solve the error propagation problem of the traditional network-coded cooperative diversity scheme, we proposed a opportunistic network-coded cooperative diversity algorithm by introducing "opportunistic" at the relay nodes. The proposed algorithm, due to incorporating erroneous data into network-coded data, error propagation problem can be avoided and the performance of system is significantly improved.