Power Control and Soft Topology Adaptations in Multihop Cellular Networks with Multi-Point Connectivity

TL;DR

This paper explores how allowing UEs in multihop cellular networks to connect to multiple points and adapt their transmit power can significantly increase network capacity, with decisions converging without explicit cooperation.

Contribution

It introduces a model for UEs to split transmit power over multiple links and adapt their point of access, demonstrating substantial capacity gains and deriving closed-form power allocation solutions.

Findings

Network capacity increases with multipoint connectivity.

Decentralized power and access decisions converge.

Closed-form expressions for optimal power levels are derived.

Abstract

The LTE standards account for the use of relays to enhance coverage near the cell edge. In a traditional topology, a mobile can either establish a direct link to the base station (BS) or a link to the relay, but not both. In this paper, we consider the benefit of multipoint connectivity in allowing User Equipment (UEs) to split their transmit power over simultaneous links to the BS and the relay, in effect transmitting two parallel flows. We model decisions by the UEs as to: (i) which point of access to attach to (either a relay or a relay and the BS or only the BS); and (ii) how to allocate transmit power over these links so as to maximize their total rate. We show that this flexibility in the selection of points of access leads to substantial network capacity increase against when nodes operate in a fixed network topology. Individual adaptations by UEs, in terms of both point of access and transmit power, are interdependent due to interference and to the possibility of over-loading of the backhaul links. We show that these decisions can converge without any explicit cooperation and derive a closed-form expression for the transmit power levels.