Load Optimization with User Association in Cooperative and Load-Coupled LTE Networks

TL;DR

This paper addresses load balancing in LTE networks by optimizing user association considering joint transmission and load coupling, proposing NP-hard problem formulations, MILP-based solutions, and conditions for performance improvement.

Contribution

It introduces novel optimization problems for load balancing with joint transmission and load coupling, providing MILP solutions and partial optimality conditions.

Findings

Proposed MILP-based schemes effectively reduce network load.

Derived conditions guarantee performance improvements.

Simulation confirms the effectiveness of the approaches.

Abstract

We extend the problem of optimizing user association for load balancing in cellular networks along two dimensions. First, we consider joint transmission (JT), which is one of the coordinated multipoint (CoMP) techniques, with which a user may be simultaneously served by multiple base stations. Second, we account for, mathematically, the coupling relation between the base stations' load levels that are dependent on each other due to inter-cell interference. We formulate two optimization problems, sum load minimization (MinSumL) and maximum load minimization (MinMaxL). We prove that both MinSumL and MinMaxL are NP-hard. We propose a mixed integer linear programming (MILP) based scheme by means of linearization. This approach also leads to a bounding scheme for performance benchmarking. Then, we derive a set of partial optimality conditions. Fulfillment of the conditions will guarantee performance improvement for both MinSumL and MinMaxL. A solution algorithm is then derived based on the conditions. Simulation results are provided to demonstrate the effectiveness of the approaches.