On Secure Degrees of Freedom of the MIMO Interference Channel with Local Output Feedback

TL;DR

This paper investigates the secure degrees of freedom in MIMO interference channels with local output feedback, proposing new transmission schemes and optimizing their performance for future vehicular communication systems.

Contribution

It introduces two novel transmission schemes and provides a sum-SDoF lower bound, enhancing understanding of secure MIMO interference channels with local feedback.

Findings

Sum-SDoF lower bound established for specific antenna configurations.

Optimal M to maximize sum-SDoF is at least twice the number of antennas N.

Local output feedback improves secure sum-rate over delayed channel state information.

Abstract

This paper studies the problem of sum-secure degrees of freedom (SDoF) of the (M,M,N,N) multiple-input multiple-output (MIMO) interference channel with local output feedback, so as to build an information-theoretic foundation and provide practical transmission schemes for 6G-enabled vehicles-to-vehicles (V2V). For this problem, we propose two novel transmission schemes, i.e., the interference decoding scheme and the interference alignment scheme, and thus establish a sum-SDoF lower bound. In particular, to optimize the phase duration, we analyze the security and decoding constraints and formulate a linear-fractional optimization problem. Furthermore, we show that the derived sum-SDoF lower bound is the sum-SDoF for M <= N/2, N=M, and 2N <= M antenna configurations, and reveal that for a fixed N, the optimal M to maximize the sum-SDoF is not less than 2N. Through simulations, we examine the secure sum-rate performance of proposed transmission schemes, and reveal that using local output feedback can lead to a higher secure sum-rate than that by using delayed channel state information at the transmitter.