LAUSR

This paper examines the role of full-duplex radio for securing wireless network from a new perspective. It first studies the secrecy capacity of two single-antenna full-duplex users against a multi-antenna eavesdropper (Eve) who has the perfect knowledge of the channel state information (CSI) from users to Eve. It is shown that if Eve uses a basic matched-filtering, the probability of zero secrecy (or outage) can be made small by a large jamming power from both users and a small gain of residual self-interference (RSI) power. But if Eve uses the optimal matched-filtering, the probability of outage grows rapidly as either the jamming power from the users increases or the number of antennas on Eve increases, regardless of the RSI gain. To prevent any Eve from obtaining its CSI, this paper then proposes a novel anti-eavesdropping channel estimation (ANECE) method, which allows users to obtain their own CSI while keeping all Eves in handicap. This method also prevents Eves from colluding with each other at any layer. The design of ideal pilots for ANECE for multiple multi-antenna users and multiple broadband multi-antenna users is discussed. It is also shown that the capacity of Eve with any number of antennas but without its CSI can be virtually eliminated over a time window corresponding to the number of antennas at the transmitter for each realization of the CSI.