Research On Power Allocation And Security Strategy In Relay Coordination Network Based On Network Coding

With the development of microelectronics and digital signal processing technology in recent years, mobile communication technology has achieved unprecedented success, a dramatic rise can be seen in the number of mobile users and people have increasingly higher requirements for the wireless communication. In this situation, the extensive application of cooperative relay technology has significantly improved the quality of cellular mobile communication because this technology has made a "virtual MIMO" system by the collaboration between the source and the relay. In this way, Assist relay technology can not only expand the coverage of communication, but also enhance the reliability of communication by diversity gain. The uplink multiple access relay channel model, as a classic cooperative relay network topology, consists of two transmitting nodes: one is the relay and the other is the base station. Besides, MARC communications system can combine cooperative relay technology and network coding technique, which results in the breaking of limited defect system capacity of cooperative relaying technology and further improvement of the channel capacity of the system. However, a number of problems still exist in current research on the uplink. For example, because of the existence of numerous nodes in the MARC system, and limited power resources, it is necessary to reasonably distribute power among nodes. In addition, the source node and the base station in MARC system need to transmit useful information multiple times, and the broadcast nature of wireless channel makes it possible for eavesdroppers to eavesdrop useful information without being detected, which has caused a huge threat to the security for the uplink. To solve the above two issues, this dissertation will explore the power allocation of optimal system channel capacity and optimization of secrecy capacity of the system security strategy based on the introduction of wireless relay coordination model in cellular network which uses network coding. The main study of this dissertation includes:(1) According to the MARC model utilizing network coding technology and for the purpose of maximizing the channel capacity of the system, the power allocation schemes of two sources and relay will be analyzed under certain conditions of system power. Additionally, through numerical simulation and comparison with the relay system that does not adopt the network coding technique, it can be concluded that the utilization of network coding technology has led to the gain of system channel capacity.(2)In response to the situation that eavesdroppers exist in MARC system, this dissertation will put forward various cooperative jamming schemes, which are artificial jamming from base station and friendly collaboration interference node respectively. Then, secrecy capacity formulas that correspond to different schemes will be deduced. Finally, by the comparison of numerical simulation, the best artificial jamming scheme can be obtained. At the same time, through the combination with allocation results of the letter source and the relay when the main channel capacity owns the maximum power in the first part, this scheme realizes the rational allocation of emission of the signal and the interference power and achieves the goal of lifting system resources to the maximum secrecy capacity.From the point of optimizing transmission performance and safety features of the MARC system, this dissertation firstly will solve the problem of uplink resource constraints in the multi-node power distribution of the MARC system adopting network coding technology, and verify that the reasonable power allocation can greatly enhance the channel capacity of system. Moreover, this dissertation will propose diverse cooperative jamming schemes based on the issue of eavesdropper in the uplink, and analyze the improvement of secrecy capability of the system resulted from the usage of different jamming strategies.