Physical Layer Security Of Cognitive Radio Networks Based On Energy Harvesting

The huge consumption of energy,the lack of spectrum resources,and the security of information transmission are the main issues which restrict the development of wireless communication.Energy harvesting can slow down the consumption of energy sources(to some extent)and extend the life of communication equipment without changing the battery.Cognitive radio can solve the lack of spectrum resources by improving the utilization rate of the spectrum.In the cognitive network,the transmission power and time are usually limited,so the use of energy harvesting on the transmitter can save energy and improve the utilization of the spectrum.But the implementation of energy harvesting makes the network safety more vulnerable.Physical layer security(PLS)can achieve safe communication by the time variation prosperity in wireless channel without using secret keys,hence is an important research direction to achieve safe communication.The use of PLS can ensure the safety of cognitive networks based on energy harvesting.The thesis will model and analyze the physical layer security performance of cognitive radio networks based on energy harvesting and improve the performance by antennas selection.The main contents are as follows:1.The mathematical modeling and analysis of the physical layer security performance of the cognitive radio network based on energy harvesting are carried out.The system model consists of a pair of primary users,a pair of cognitive users,and eavesdroppers which are adjacent to the receiver of the cognitive user.For some reasons(such as the battery drains),the cognitive user needs to harvest energy from the wireless signal to send messages.The closed-form expression of the secrecy outage probability of the cognitive user is obtained in this thesis.The simulation result certifies the correctness of the theoretical analysis.It shows that the secrecy performance of the cognitive user is affected by the state of the information channel,the transmission power of the main user and the interference temperature threshold.The proper allocation between energy harvesting time and information sending time while the information transmission time of cognitive user is limited is also analyzed.2.Diversity and antenna selection technology can improve the performance of wireless communication systems.This thesis assumes that antenna selection and the maximum ratio combining technology are applied in the sender and receiver of the cognitive user,respectively.Based on the analysis of the physical layer security performance of the system under different antenna selection strategies,the closed-form expressions of the exact and asymptotic safety interrupt probability of the system are deduced respectively.The hierarchical order and diversity gain of the system are also obtained.3.The implementation of the transmit antenna selection strategy is achievable while the transmitter obtains the channel state information fed back by the receiver.When the feedback is no delay,no error,the sender can choose the optimal antenna to transmit.However,in practice,ideal feedback is difficult to achieve due to the influence of information feedback delay,channel estimation error and other factors,which will make the channel state information owned by the sender be outdated.The thesis analyzed the physical layer security performance of the cognitive user network under the transmission antenna selection strategy when the channel state information is outdated,and the influence of the delay parameter on the security performance of the system is also analyzed.