Local base station assignment with time intervals in mobile computing environments

Several telecommunication service providers are currently supplying data access services to mobile users who may connect and disconnect at any time. In order to ensure a high level of service, these firms must consider both load management issues as well as data access costs. We formulate several combinatorial optimization problems that arise in this context. In these problems, each user specifies a time interval during which data access is needed. The focus of our work is on two types of offline problems where each mobile user must be assigned a local base station. The first type considers this assignment problem under load constraints. The other seeks to minimize data access costs while satisfying the load constraints. When all the users connect at the same time, we show that the problems can be solved efficiently. However, if there are two or more distinct connect times, the problems become computationally intractable. For such problems, approximation algorithms with proven performance guarantees are presented. We also identify some special cases which can be solved efficiently. (C) 2003 Elsevier B.V. All rights reserved.