Secure Degree of Freedom of Wireless Networks Using Collaborative Pilots

TL;DR

This paper analyzes the secure degree-of-freedom (SDoF) in wireless full-duplex networks using collaborative pilots, providing bounds and conditions for optimal secure communication regardless of eavesdropper capabilities.

Contribution

It introduces novel bounds and conditions for SDoF in multi-user ANECE, demonstrating improved schemes for secure wireless communication.

Findings

Multi-user ANECE achieves the same phase-1 SDoF with fewer time slots.

In three-user networks, all-user ANECE has larger phase-2 SDoF than pair-wise.

Modified two-user ANECE with square pilot matrices yields higher total SDoF.

Abstract

A wireless network of full-duplex nodes/users, using anti-eavesdropping channel estimation (ANECE) based on collaborative pilots, can yield a positive secure degree-of-freedom (SDoF) regardless of the number of antennas an eavesdropper may have. This paper presents novel results on SDoF of ANECE by analyzing secret-key capacity (SKC) of each pair of nodes in a network of multiple collaborative nodes per channel coherence period. Each transmission session of ANECE has two phases: phase 1 is used for pilots, and phase 2 is used for random symbols. This results in two parts of SDoF of ANECE. Both lower and upper bounds on the SDoF of ANECE for any number of users are shown, and the conditions for the two bounds to meet are given. This leads to important discoveries, including: a) The phase-1 SDoF is the same for both multi-user ANECE and pair-wise ANECE while the former may require only a fraction of the number of time slots needed by the latter; b) For a three-user network, the phase-2 SDoF of all-user ANECE is generally larger than that of pair-wise ANECE; c) For a two-user network, a modified ANECE deploying square-shaped nonsingular pilot matrices yields a higher total SDoF than the original ANECE. The multi-user ANECE and the modified two-user ANECE shown in this paper appear to be the best full-duplex schemes known today in terms of SDoF subject to each node using a given number of antennas for both transmitting and receiving.