User Assignment in C-RAN Systems: Algorithms and Bounds

TL;DR

This paper addresses user assignment in C-RAN systems by formulating an integer optimization problem, proposing an iterative algorithm, deriving bounds using decomposition and duality, and demonstrating significant sum-rate improvements with lower complexity.

Contribution

It introduces a new user assignment algorithm for C-RAN, derives tighter bounds using Dantzig-Wolfe decomposition, and compares its performance and complexity to existing schemes.

Findings

Significant sum-rate gains over comparison schemes.

Proposed scheme achieves similar performance to W-MMSE with lower complexity.

Derived bounds provide insights into interference leakage and solution optimality.

Abstract

In this work, we investigate the problem of mitigating interference between so called antenna domains of a cloud radio access network (C-RAN). In contrast to previous work, we turn to an approach utilizing primarily the optimal assignment of users to central processors in a C-RAN deployment. We formulate this user assignment problem as an integer optimization problem, and propose an iterative algorithm for obtaining a solution. Motivated by the lack of optimality guarantees on such solutions, we opt to find lower bounds on the problem, and the resulting interference leakage in the network. We thus derive the corresponding Dantzig-Wolfe decomposition, formulate the dual problem, and show that the former offers a tighter bound than the latter. We highlight the fact that the bounds in question consist of linear problems with an exponential number of variables, and adapt the column generation method for solving them. In addition to shedding light on the tightness of the bounds in question, our numerical results show significant sum-rate gains over several comparison schemes. Moreover, the proposed scheme delivers similar performance as W-MMSE with a significantly lower complexity (around 10 times less).