Secure Degrees-of-Freedom of the MIMO X Channel with Delayed CSIT

TL;DR

This paper characterizes the secure degrees-of-freedom for the MIMO X channel with confidential messages and delayed CSIT, proposing a new transmission scheme that optimizes artificial noise duration to maximize secure throughput.

Contribution

It introduces a generalized transmission scheme for secure MIMO X channels with delayed CSIT, including a security analysis and optimal artificial noise duration, deriving a new lower bound on sum-SDoF.

Findings

Derived the sum-SDoF lower bound for the secure MIMO X channel.

Identified the minimum number of transmit antennas needed for maximum sum-SDoF.

Proposed a generalized transmission scheme extending previous non-secure methods.

Abstract

In this paper, we study the secure degrees-of-freedom (SDoF) characterization for the multiple-input multiple-output (MIMO) X channel with confidential messages and delayed CSIT. In particular, we propose a transmission scheme, which can be regarded as a generalization of the state-of-the-art scheme without security and with delayed CSIT. The key of this generalization is performing the security analysis, by which we derive the optimal duration of the artificial noise transmission phase. As a result, we derive the sum-SDoF lower bound. Furthermore, we reveal that if the number of receive antennas, denoted by N, is fixed, the minimum number of transmit antennas achieving the maximum of the lower bound is $\frac{7+\sqrt{33}}{8}N$.