Fault-Tolerant Wireless Access Network Design for Dual-Homed Users

Abstract

In this paper, we study the survivability problem in hierarchical wireless access networks with dual-homed end users, who are connected to two base stations (BSs), a primary BS and a backup BS. The dual homing mechanism is resilient to a single failure of a BS. However, if a failure occurs at the base station controller (BSC) layer or at the mobile switching center (MSC) layer, dual-homing may not prevent connection loss. We address the problem of routing from BSs to BSCs and from BSCs to MSCs, with the objective of minimizing the maximum number of connections lost due to a single failure of BS, BSC, or MSC. We first formulate the problem using Integer Linear Programming (ILP). We then prove that this optimization problem is NP-hard by showing some of its subproblems with relaxed constraints are still NP-hard. A Tabu Search (TS) based heuristic is then proposed for the problem, which provides near optimal results in most cases.