Study On Resource Allocation Strategy In Cooperative Relay Network

Cooperative relay network is a wireless communication system which implements spatial diversity by forwarding among the users. Through sharing their antennas, users implement the reuse of the spatial resource, and improve the capacity and the reliability. In cooperative relay network, the resource such as power, bandwidth and time slot, is limited. Thus, the inappropriate resource allocation will incur the reduction of the performance of the users and the relays, which may be smaller than the non-cooperative case. Thus, resource allocation is a key problem for making the cooperative relay network effective, where the users and the relays can both improve their performance. Resource allocation has already becomes one of the most challenging topics. The thesis studies the resource allocation strategy for symmetric and asymmetric cooperative relay network, and presents the corresponding power allocation, relay selection and bandwidth allocation algorithm. Then, the results are extended to the spectrum sharing between the primary user and the cognitive user in cognitive cooperative relay network, and the optimal time slot allocation strategy is shown.Firstly, the thesis considers the asymmetric cooperative relay network composed of one relay and several users, where the relay not only forwards other users'data, but also transmits its own data to the base station. Thus, in order to earn larger profit, the relay's power allocation strategy should achieve a trade-off between the relaying and the direct transmission. The power allocation is first cast into a Stackelberg game. Based on the backward induction, the Nash equilibrium of the non-cooperative payment selection game is obtained, and then the optimal power allocation of the relay is calculated. Numerical results show that the relay can improve its performance with the power allocation based on Stackelberg game.Secondly, the thesis studies the joint relay selection and power allocation problem for asymmetric cooperative relay network composed of multiple users and multiple relays. Aiming at maximizing the total transmission rates, the joint design problem is formulated as a non-convex optimization problem, which includes both real and combinatorial variables. Based on the dual decomposition, the sub-optimal joint relay selection and power allocation solutions are obtained, and the distributed implementation and admission control algorithm are also shown, such that users participated in cooperation can obtain larger transmission rates than the minimal rate requirement. Numerical examples show that the joint design approach is more accurate than the isolated design method, and improves the total network transmission rates.Thirdly, the thesis considers the symmetric cooperative relay network composed of two users. The cooperative condition is established based on Raiffa-Kalai- Smorodinsky bargaining solution, and the optimal bandwidth allocation is obtained. Numerical results indicate that the utility allocation obtained by Raiffa-Kalai- Smorodinsky bargaining solution shows better fairness than that based on Nash bargaining solution. Then, the results are extended to the networks with multiple users. To make the cooperation feasible for the users, the grouping and admission control algorithm is presented and the optimal bandwidth allocation is obtained by Nash bargaining solution and Kalai-Smorodinsky bargaining solution in each group. Numerical results show that the grouping and admission control algorithm can put the users into different cooperative groups, where the users can improve their performance through cooperation.Finally, the thesis studies the time slot allocation strategy for spectrum sharing between the primary user and the cognitive user in cognitive cooperative relay network. To overcome the unfeasible time slot allocation solution obtained from Stackelberg game, the time slot allocation is formulated as a bargaining problem. Then, the cooperative condition is established based on Nash bargaining solution, and the optimal leasing time slot allocation and cooperative time slot allocation are obtained. Numerical results show that the time slot allocation strategy is an efficient spectrum sharing method between the primary user and the cognitive user.