Position location systems are becoming increasingly important as add-ons to today’s pervasive wireless technology. Location – aware services are based on some form of positioning techniques. Positioning systems enable context – aware computing with location awareness . Information such as location, group, object that are directly related to an application’s operating environment are often referred to as context of that application which can detect the control and modify its behaviour based on dynamic content is called a contact-aware application . Location in one such context can be of great significance for wireless applications.
An indoor Positioning System (IPS) is a system that “continuously and in real –time can determine the position of something or someone from a distance within a physical space”. An example of a physical space can be a factory, warehouse, hospital, etc. The three key words in the definition are continuously, real-time and distance. ← Continuously means that the system is “on” at all times although it can be turned “off” when a person chooses to “opt out” for privacy reasons. ← Real-time means that the system will update the position of an object or person on a frequent basis, ideally second-by-second. ← Distance means that people or objects can be located within a physical space without having to move through a particular portal (such as the entrance to a building or room).
Applications of indoor location systems consists of three main categories; commercial, public safety and military applications. In commercial applications, the main need is for locating patients in a hospital, or important objects in warehouse. Public safety application comprises of locating inmates in prison or fire fighters in a building. In military applications, the main interest is tracing soldiers in combat .
In the last couple of years, location fingerprinting techniques using existing wireless local area network (WLAN) infrastructure has been suggested for indoor areas where the global positioning system (GPS) does not work well. The fingerprinting technique is relatively simple to deploy compared to the other techniques such as angle-of-arrival (AOA) and time-of-arrival (TOA). Moreover, there is no specialized hardware required at the mobile station (MS). Any existing wireless LAN infrastructure can be reused for this positioning system.
Bluetooth specification [4,5] provides no specific support for positioning service. In the absence of such support, various research efforts have been made in the area with alternating conclusions. Patil used Bluetooth signal strength information to create a system for locating and tracking users inside buildings . Patil introduced the concept of reference tags and readers that work with both possibilities of Bluetooth supporting and not supporting the signal strength parameter On the other hand, work by Hallberg, Nilsson, and Synnes suggests an unreliable relationship between the positioning and the signal strength and hence avoids this parameters for positioning with Bluetooth .
The flow-chart of the system illustrated by figure (1.1) presents an overview of the operation breakdown.
Figure (1.1) Flow chart of the Bluetooth-based positioning system.
In this paper, we will investigate the Bluetooth adhoc network and its ability to be used for more accurate and low cost positioning as compared to other methods. Specifically, we will focus primarily on RSS/fingerprinting method for the positioning service, but will consider other available Bluetooth metrics such as link quality (LQ) and bit-error rate (BER).
2. LOCALIZATION TECHNIQUES:
Depending on the electromagnetic signal parameter chosen for the position determination, Caffery and Stuber  and Tahvildari  identified three fundamental approaches to radiolocation system: