Multiaccess Communication via a Broadcast Approach Adapted to the Multiuser Channel

TL;DR

This paper introduces a novel broadcast strategy for multiaccess channels with slow fading, where transmitters adapt to combined channel states, leading to improved rate regions over existing single-user adaptation methods.

Contribution

It proposes a multiuser broadcast approach that considers all users' channel states, expanding the set of information streams and enhancing achievable rate regions.

Findings

Achievable rate region surpasses existing single-user adapted strategies.

The proposed method captures the trade-off among multiple information layers.

The rate region includes known capacity regions as special cases.

Abstract

A broadcast strategy for multiple access communication over slowly fading channels is introduced, in which the channel state information is known to only the receiver. In this strategy, the transmitters split their information streams into multiple independent information streams, each adapted to a specific actual channel realization. The major distinction between the proposed strategy and the existing ones is that in the existing approaches, each transmitter adapts its transmission strategy only to the fading process of its direct channel to the receiver, hence directly adopting a single-user strategy previously designed for the single-user channels. However, the contribution of each user to a network-wide measure (e.g., sum-rate capacity) depends not only on the user's direct channel to the receiver, but also on the qualities of other channels. Driven by this premise, this paper proposes an alternative broadcast strategy in which the transmitters adapt their transmissions to the combined states resulting from all users' channels. This leads to generating a larger number of information streams by each transmitter and adopting a different decoding strategy by the receiver. An achievable rate region and an outer bound that capture the trade-off among the rates of different information layers are established, and it is shown that the achievable rate region subsumes the existing known capacity regions obtained based on adapting the broadcast approach to the single-user channels.