Transmit antenna selection to improve physical layer security for MIMO-CR systems

In this paper, we consider a multi-input-multi-output cognitive radio (MIMO-CR) system which consists of one secondary user (SU) and one secondary destination (SD), in which one eavesdropper (E) attempts to tap the information from SU to SD. All of the aforementioned nodes are equipped with multiple antennas. For enhancing physical layer security, we propose so-called optimal antenna selection (OAS) and suboptimal antenna selection (SAS) schemes, which assume that the instantaneous wiretap channel information is known and unknown, respectively. We carry out the secrecy outage probability analysis for the proposed OAS and SAS schemes. In order to make a performance comparison, we also discuss the secrecy outage probability of single-input-single-output cognitive radio (SISO-CR) system. The secrecy outage performance of SAS is better than SISO but worse than OAS. Furthermore, as the numbers of antennas of SU and SD increase, the secrecy outage probability of OAS and SAS both have significant improvements.