W-CDMA network design

Abstract

In this investigation, the W-CDMA network design problem is modelled as a discrete optimisation problem that maximises revenue net the cost of constructing base stations, Mobile Telephone Switching Offices (MTSOs) and the backbone network to connect base stations through MTSOs to the Public Switched Telephone Network (PSTN). The formulation results in a very large scale integer programming problem with up to 18,000 integer variables and 20,000 constraints. To solve this large scale integer programming problem, we develop a pair of models, one for the upper bound and one for the lower bound. The upper bound model relaxes integrality on some of the variables while the lower bound model uses a 5% optimality gap to achieve early termination. Additionally, we develop a heuristic procedure that can solve the largest problem instances very quickly with a small optimality gap. To demonstrate the efficiency of the proposed solution methods, problem instances were solved with five candidate MTSOs servicing some 11,000 simultaneous cellular phone sessions on a network with up to 160 base stations. In all instances, solutions guaranteed to be within 5% of optimality were obtained in less than an hour of CPU time.