Broadcast Cooperation Strategies for Two Colocated Users

TL;DR

This paper explores multi-layer broadcast cooperation strategies for colocated users over Rayleigh fading channels, demonstrating how layered transmission and multi-session cooperation improve achievable rates.

Contribution

It introduces a multi-layer broadcast approach combined with multi-session cooperation techniques like AF, CF, and DF for colocated users, extending existing methods with closed-form and recursive expressions.

Findings

Multi-session cooperation enhances achievable rates.

Broadcast approach improves user cooperation efficiency.

Numerical results confirm the effectiveness of the proposed strategies.

Abstract

This work considers the problem of communication from a single transmitter, over a network with colocated users, through an independent block Rayleigh fading channel. The colocation nature of the users allows cooperation, which increases the overall achievable rate, from the transmitter to the destined user. The transmitter is ignorant of the fading coefficients, while receivers have access to perfect channel state information (CSI). This gives rise to the multi-layer broadcast approach used by the transmitter. The broadcast approach allows, in our network setting, to improve the cooperation between the colocated users. That is due to the nature of broadcasting, where the better the channel quality, the more layers that can be decoded. The cooperation between the users is performed over an additive white Gaussian channels (AWGN), with a relaying power constraint, and unlimited bandwidth. Three commonly used cooperation techniques are studied: amplify-forward (AF), compress-forward (CF), and decode-forward (DF). These methods are extended using the broadcast approach, for the case of relaxed decoding delay constraint. For this case a separated processing of the layers, which includes multi-session cooperation is shown to be beneficial. Further, closed form expressions for infinitely many AF sessions and recursive expressions for the more complex CF are given. Numerical results for the various cooperation strategies demonstrate the efficiency of multi-session cooperation.