Wireless Security with Beamforming Technique

This thesis focuses on the wireless security in the physical layer with beamformingtechnique. As the wireless communications grow more important, a higher level ofsecurity is more demanding as well. New techniques have been proposed in complementto the existing encryption-based methods in the communications protocols. One of theemerging areas is the security enhancement in the physical layer, which exploits theintrinsic properties of the wireless medium. Beamforming, which has been proved tohave many advantages, such as increasing data rates and reducing interference, can alsobe applied to enhance the wireless security.One of the most common threats, i.e., passive eavesdropping, is addressed in thisthesis. Passive eavesdroppers bring significant challenges to the system design, becausethe knowledge of their locations and channel condition is generally difficult to acquire.To reduce the risk of leaking information to the eavesdroppers, the physical regionwhere the transmission is exposed to eavesdropping has been studied. In this thesis, theexposure region based beamforming technique is proposed to combat the threat fromthe randomly located eavesdroppers in a fading channel.A stochastic geometry tool is used to model the distribution of the passive eaves-droppers. In this system model, the large-scale path loss and a general Rician fadingchannel model are considered. The exposure region is established to describe thesecrecy performance of the system, based on which the probability that the secrecyoutage event occurs is defined to evaluate the security level of the exposure region.The antenna array is one of the most important factors that affect the secrecyperformance of the exposure region based beamforming technique. The potential ofusing different array geometry and array configuration to improve security is explored.