Anti-Eavesdropping Channel Estimation Using Multi-Antenna Half-Duplex Radios

This paper reviews the basic principles of prior methods for the purpose of wireless anti-eavesdropping channel estimation (ANECE), and highlights their major shortcomings and limitations such as failure for carrier synchronization without a pilot and limited transmission range of a full-duplex radio. This paper also proposes and analyses a new scheme of ANECE using multi-antenna half-duplex radios. This new scheme consists of three phases of transmissions between two radio nodes (Alice and Bob). In phase 1, Bob sends out a pilot via one of his antennas so that Alice can carry out carrier synchronization and channel estimation. In phase 2, Alice sends out a pilot via one of her antennas so that Bob can carry out carrier synchronization and channel estimation. In phase 3, perfectly synchronized with phase 2, Alice applies transmit beamforming and sends out a stream of information via all her other antennas. This new scheme of ANECE for multi-antenna half-duplex radios is derived from an ANECE design for antenna-isolation based full-duplex radios.