On Secrecy of a Multi-Antenna System with Eavesdropper in Close Proximity

This letter investigates secrecy performance of a wiretap channel where an eavesdropper is located in close proximity to legitimate receiver. In the system, both receivers equip multiple antennas and use maximal ratio combining (MRC) to harvest diversity gains. In order to analyze the impact of eavesdropping in close proximity, we derive closed-form expressions for the system performance in terms of both secrecy capacity and outage probability. Since the derived expressions involve infinite series sums, finite series approximations are then presented with guaranteed truncation error. Moreover, we also characterize the asymptotic behavior of secrecy outage. Some insightful observations are accordingly manifested with numerical verifications.