Research On Network Selection Strategy And Cooperative Relay Technology In Heterogeneous Wireless Network

With the emerging and development of all kinds of wireless access technology,wireless networks overlap and complement each other, and form a hybrid wireless network called heterogeneous wireless network. In order to achieve complementary advantages and coordinated management for heterogeneous resources, integration and cooperation for heterogeneous wireless networks are the development trend of future mobile broadband wireless communication. The integration between different wireless access networks will face a lot of technical problems, such as joint radio resource management, heterogeneous multimode terminal and access selection mechanism, software radio and reconfiguration technology, etc. On the other hand, cooperative relay is a critical technology for realizing cooperative communication between heterogeneous wireless access network, its research contents include power allocation and resources allocation、cooperative coding and relay selection strategy, etc. To build advanced wireless communications networks, key technologies of integration and cooperation for heterogeneous wireless network remain to be further in-depth study.In heterogeneous wireless networks, for the conditions that mobile terminals may be in overlapped coverage area of several different wireless access networks, or mobile terminals can not connect to the base station due to geographical location, decline and other reasons, network selection strategy and cooperative relay technology were in-depth studied for heterogeneous wireless networks. The main contributions of this thesis are summarized as follows.1、In heterogeneous wireless network selection algorithm, for not considering that real-time state of mobile terminals has effect on parameter setting of utility function when attribute datas are standardized by utility function, a method for parameter setting of utilityfunction based on fuzzy inference system is proposed. Through the simulation analysis,terminal power can be used more reasonably when considering effect of remaining power on utility of power consumption, handoff frequency can be reduced and system performance can be improved when considering effect of terminal speed on utility of distance which terminal move to drive away alternative networks.2、To work out the problem that terminal may access the pseudo optimal network with best overall performance and worst performance for individual attribute by using Multiple Attribute Decision Making(MADM) in heterogeneous wireless networks, the performance of four methods SAW、TOPSIS、GRA and MEW accessing the pseudo optimal network is discussed, and wireless network selection algorithm based on MEW and combination weights is proposed. This algorithm can avoid well to access the pseudo optimal network,and its performance of balancing network load and reducing ping-pong effect is superior to other three methods.3、With the objective of minimizing the sum transmit energy at the required data rate,the optimal relay positioning and power allocation problem is investigated in one-way multi-relay transmission system. A sub-solution for the optimal relay positioning and power allocation problem for a two-relay channel is firstly proposed, due to no close-form optimal solution.Then, the optimal relay positioning and power allocation problem for one-way N-relay(N>1) channel is discussed and the sub-solution is extend to one-way N-relay channel.The simulation results demonstrate a consistence with our proposed schemes.4、The principle of two-way relay trassimission based on Analog Network Coding(ANC) is firstly studied. Then, solution for the optimal relay positioning and power allocation problem for a two-way two-relay channel is proposed, and it is extended to two-way N-relay channel, including N is even and odd. The simulation results demonstrate a consistence with our proposed schemes.