Research On Cooperative Interference Techniques In Wireless Relay Systems

Compared with conventional wired communication systems,wireless communication systems face more serious security issues due to its openness.Most traditional information security techniques are deployed in the upper level protocols,and the physical security technology research is lack of attentions.In recent years,cooperative jamming/interference techniques in wireless communication systems have become a hotspot in the physical layer security field.This thesis utilizes cooperative interference techniques to make use of wireless channel resources,so as to enhance the secrecy capacity of the wireless relay systems.Firstly,this thesis introduces the related knowledge and the research status of cooperative interference techniques.The research scenarios of this thesis are wireless bi-directional single-relay and wireless bi-directional multi-relay systems.For the wireless bi-directional single-relay system,two kinds of cooperative interference schemes are designed in this thesis.They are two-phase cooperative interference scheme and three-phase cooperative interference scheme.Both schemes include the power allocation scheme with power limit of each nodes and the relay selection algorithm.In this thesis,the proposed cooperative interference schemes have been simulated to verify their reliability and validity.For the wireless bi-directional multi-relays system,we make some simplification of the problem firstly.The cooperative interference scheme of bidirectional two-relay system is studied,which includes cooperative interference method and phase selection(PS)algorithm.Then the scheme of bi-directional two-relay system is extended to solve security issues of bi-directional three-relay system,using a relay polymerization(RP)method.At last,two relay merging(RM)sequences are designed.The PS algorithm can determine the phases of two relays transmission signals,and make the relays cooperative with each other.The RP method combines two relays to a new 'relay',and then gradually simplifies the system model.The RM strategy rules the order to combine multi-relay system(more than two relays).The combination of the PS algorithm,the RP method,and the RM sequences is just the cooperative interference scheme for bi-directional multi-relay system.Through the simulation,these cooperative interference methods are effective to enhance the secrecy capacity performance of wireless relay systems.