Guaranteeing Positive Secrecy Capacity with Finite-Rate Feedback using Artificial Noise

TL;DR

This paper analyzes the ergodic secrecy capacity of MIMOME channels with finite-rate feedback, proposing bounds and efficient quantization methods to ensure positive secrecy capacity using artificial noise.

Contribution

It refines the analysis of RVQ-based artificial noise schemes, providing a lower bound on ergodic secrecy capacity and an efficient codebook construction for two antennas.

Findings

Lower bound on ergodic secrecy capacity derived

Secrecy capacity approaches perfect CSI case asymptotically

Efficient quantization codebook for two antennas proposed

Abstract

While the impact of finite-rate feedback on the capacity of fading channels has been extensively studied in the literature, not much attention has been paid to this problem under secrecy constraint. In this work, we study the ergodic secret capacity of a multiple-input multiple-output multiple-antenna-eavesdropper (MIMOME) wiretap channel with quantized channel state information (CSI) at the transmitter and perfect CSI at the legitimate receiver, under the assumption that only the statistics of eavesdropper CSI is known at the transmitter. We refine the analysis of the random vector quantization (RVQ) based artificial noise (AN) scheme in [1], where a heuristic upper bound on the secrecy rate loss, when compared to the perfect CSI case, was given. We propose a lower bound on the ergodic secrecy capacity. We show that the lower bound and the secrecy capacity with perfect CSI coincide asymptotically as the number of feedback bits and the AN power go to infinity. For practical applications, we propose a very efficient quantization codebook construction method for the two transmit antennas case.