Wireless Network Design: Optimization Models and Solution ...

136 Jeff Kennington, Jason Kratz, and Gheorghe Spiride
6.2.6 Current State-of-the-Art
Based upon the experience of deploying WLANs on our own campus and the literature
in the previous sections, we conclude that IT professionals use a combination
of three basic strategies to design WLANs: i) they arbitrarily decide where to locate
APs, ii) they conduct site-surveys, or iii) they use the assistance of software tools.
Over the course of the last 10 years, WLAN access has evolved from a somewhat infrequent
feature of an enterprise network to a “must-have”. Practical WLAN design
approaches have mirrored this evolution path. Initially, simple designs involving
only a few APs were put together by simply select the APs’ location and assigning
frequencies that appear appropriate. This sort of ad-hoc design approach evolved to
support more complicated designs, where site-surveys would be undertaken. Geier
[4] - the principal consultant and founder of Wireless-Nets, Ltd. - illustrates the
recent state-of-the-art in the practice of site surveys for WLAN design.
The proliferation of low-cost WLAN hardware “bundled” along with portable
computers, smartphones, appliances, game consoles, etc. contributes to the increase
in complexity of WLAN designs, especially within the scope of large enterprise deployments.
Many hardware vendors provide proprietary software tools for use with
their products. The tools described by Longo [11] (OPNET Technologies) and Skidmore
et al. [19] (Wireless Valley Communications, Inc.) represent the current stateof-the-art
of these types of tools. The initial efforts outlined in [3] were augmented
by the development of the Site-Specific System Simulator for Wireless Communications
(S 4 W) at Virginia Tech [19]. Funded by a grant from the NSF Next Generation
Software program, this PSE allows IT personnel to run simulation models that may
be used to design WLANs that minimize costs, or maximize capacity or coverage.
S 4 W also provides support for the data management tasks that simplify the maintenance
of a large WLAN design in practice.
6.3 A Maximimum Capacity-Oriented Model
A simple coverage model was presented in Section 6.2.2 and a coverage model that
also involved channel assingment was developed by Bahri and Chamberland [2].
However, to our knowledge, the literature does not contain a model that attempts to
determine the location and channel assignment of APs that yields a network having
maximum capacity. The problem of interest may be defined as follows:
Given a fixed number of APs that can be deployed in a given site with static MD locations,
determine the location and channel assignment for each AP that results in the maximum
throughput.
A new optimization-based model for this problem will be described in this section.
Solving this problem for a given building requires determining i) the number of
access points (APs) to install, ii) the location of these APs, iii) the transmission
power assigned to each AP, and iv) the frequency assigned to each AP. A mobile