Use of Ant Colony Optimization (ACO) for Post-Deployment Replanning of UMTS Networks

Abstract

Inherent dynamism in user movement demands for post-deployment tuning of UMTS networks to minimize the total cost of ownership (TCO). Conventionally, UMTS operators so far have considered many-to-one mapping of RNCs to MSCs. However, such single-homed networks do not remain cost-effective over the passage of time, typically when subscribers later on begin to show specific mobility patterns such as diurnal movement. This necessitates topological extension of the network in terms of dual-homing of some selected RNCs to two MSCs simultaneously via direct fibre links, resulting in a many-to-two mapping in parts of the network. The aim of such selective dual-homing is to reduce handoff cost maximally at the expense of minimal increase in link cost, thereby reducing the TCO optimally. In this article, the authors have formulated the scenario as an integer linear programming problem, converted it into a state space search and then solved it using Ant Colony Optimization (ACO) technique. Compared to Simulated Annealing (SA) and Tabu Search (TS), ACO exhibits 10% to 15% improvement in solution quality.