A Mixed Integer Programming Model for Optimum Placement of Base Stations and Optical Network Units in a Hybrid Wireless-Optical Broadband Access Network (WOBAN)

The concept of a hybrid wireless-optical broadband access network (referred to as WOBAN here) is a very attractive one. This is because it may be costly in several situations to run fiber to every home from the telecom central office (CO); also, providing wireless access from the CO to every end user may not be possible because of limited spectrum. Thus, running fiber as far as possible from the CO towards the end user and then having wireless access technologies take over may be an excellent compromise. How far should fiber penetrate before wireless takes over is an interesting engineering design and optimization problem, which our study is focussing on. We propose and investigate the characteristics of a "mixed integer programming (MIP)" model for optimum placements of base stations (BS) and optical network units (ONU) in a WOBAN (primal problem). We develop several constraints to be satisfied: BS and ONU installation, user and channel assignment, and signal-quality and interference constraints. To solve this MIP with reasonable accuracy, we use "Lagrangean relaxation" to obtain the corresponding "Lagrangean dual" problem. Via simulation experiments, we verify how sensitive is the placement problem with respect to a set of chosen metrics.