Fading Cognitive Multiple-Access Channels With Confidential Messages

TL;DR

This paper analyzes the secrecy capacity of fading cognitive multiple-access channels with confidential messages, deriving optimal power allocation strategies to maximize secrecy in the presence of channel fading and known CSI.

Contribution

It establishes the secrecy capacity region for parallel and fading CMAC-CM with known CSI, including a closed-form power allocation solution for optimal secrecy performance.

Findings

Secrecy capacity region for parallel CMAC-CM with degraded subchannels.

Secrecy capacity region for parallel Gaussian CMAC-CM.

Optimal power allocation functions for maximizing secrecy in fading channels.

Abstract

The fading cognitive multiple-access channel with confidential messages (CMAC-CM) is investigated, in which two users attempt to transmit common information to a destination and user 1 also has confidential information intended for the destination. User 1 views user 2 as an eavesdropper and wishes to keep its confidential information as secret as possible from user 2. The multiple-access channel (both the user-to-user channel and the user-to-destination channel) is corrupted by multiplicative fading gain coefficients in addition to additive white Gaussian noise. The channel state information (CSI) is assumed to be known at both the users and the destination. A parallel CMAC-CM with independent subchannels is first studied. The secrecy capacity region of the parallel CMAC-CM is established, which yields the secrecy capacity region of the parallel CMAC-CM with degraded subchannels. Next, the secrecy capacity region is established for the parallel Gaussian CMAC-CM, which is used to study the fading CMAC-CM. When both users know the CSI, they can dynamically change their transmission powers with the channel realization to achieve the optimal performance. The closed-form power allocation function that achieves every boundary point of the secrecy capacity region is derived.