ABSTRACT
With the emergence of enhanced services in third-generation (3G) wireless communications systems comes the necessity of developing technologies that will enable and support those services. In many applications, wireless position location, or geolocation, is a key component. For wireless communication networks, an inherently suitable approach for wireless geolocation is known as radiolocation, in which the parameters that are used for location estimation are obtained from radio signal measurements between a target and one or more fixed stations. In the realm of cellular and PCS systems, the mobile subscribers, or mobile stations (MSs), serve as the target, while the base stations (BSs) serve the role of the fixed stations. Geolocation, then, can be categorized in two ways: handset-based location and network-based location. For handsetbased location, parameters that are used to compute an MS’s position are measured at the MS and either used to calculate position in the MS or transferred to a central processing facility for position estimation. In network-based solutions, the parameters used for computing location are measured at the BSs and transferred to the central facility for location determination. Both approaches have their advantages and drawbacks. Network-based solutions do not require modifications to the handset but may be limited in
their utility due to the “hearability” problem (see Section 21.5.2). Handset-based solutions, on the other hand, require handset modification but have the potential of greater location accuracy when modified with a Global Positioning System (GPS) capable receiver. Both approaches take advantage of the existing wireless communications infrastructure without the need for supplementary technology such as dead reckoning.
