Coordinated Scheduling for the Downlink of Cloud Radio-Access Networks

TL;DR

This paper proposes a graph-theoretic coordinated scheduling method for downlink C-RANs, optimizing user-BS-PZ associations to maximize network utility with low-complexity heuristics.

Contribution

It introduces a novel scheduling graph and formulates the problem as a maximum weight clique, providing near-optimal heuristics for practical implementation.

Findings

Heuristic algorithms perform near optimally in low shadowing environments.

The graph-based approach effectively models user-BS-PZ associations.

Simulation results validate the efficiency of the proposed methods.

Abstract

This paper addresses the coordinated scheduling problem in cloud-enabled networks. Consider the downlink of a cloud-radio access network (C-RAN), where the cloud is only responsible for the scheduling policy and the synchronization of the transmit frames across the connected base-stations (BS). The transmitted frame of every BS consists of several time/frequency blocks, called power-zones (PZ), maintained at fixed transmit power. The paper considers the problem of scheduling users to PZs and BSs in a coordinated fashion across the network, by maximizing a network-wide utility under the practical constraint that each user cannot be served by more than one base-station, but can be served by one or more power-zone within each base-station frame. The paper solves the problem using a graph theoretical approach by introducing the scheduling graph in which each vertex represents an association of users, PZs and BSs. The problem is formulated as a maximum weight clique, in which the weight of each vertex is the benefit of the association represented by that vertex. The paper further presents heuristic algorithms with low computational complexity. Simulation results show the performance of the proposed algorithms and suggest that the heuristics perform near optimal in low shadowing environments