A first position (104) of the mobile client is determined at least in part by utilizing first signals received from at least one first signal source. The first signal source operates in a first location determination system (114). A second position (106) of at least one second signal source (120) is determined by utilizing both the determined first position of the mobile client and second signals received from the at least one second signal source (120). The second signal source (120) operates in a second location determination system. A third position (116) of the mobile client is determined utilizing the second signal source (120).

In many situations, a mobile client moves between or within different types of systems and networks. For example, a mobile client such as a cellular phone, pager, personal digital assistant, or personal computer may move from a satellite communication system to a Wireless Local Area network (WLAN). In another example, a mobile client may move between access points that are positioned within a WLAN. Today's networks also support services such ubiquitous computing, context aware services, and the seamless mobility of mobile clients. In order to provide and support many of these services, it is often desirable and/or necessary to be able to track and/or determine the location of the mobile client quickly and efficiently.
When a mobile client moves between systems or within systems, the location of the mobile client may sometimes become undetermined due to poor or non-existent network coverage or because of other conditions. For instance, a mobile client may operate within a satellite system and there may be locations where coverage from the satellite system is not provided. In another example, when a mobile client operates within a WLAN that provides coverage for a building, the mobile client may transition between different access points within the WLAN, and may be sometimes unlocatable during these transition periods. Consequently, network services that depend upon knowing the location of the mobile client may be difficult or costly to provide.
Previous systems have attempted to address these situations and provide for the effective and continuous location determination of mobile clients. For example, previous WLAN systems have utilized different types of mapping approaches. In some of these previous approaches, the mobile client was carried through the building in order to learn the location of the access points of the WLAN. Unfortunately, these approaches were expensive, time consuming, and inconvenient to implement. Additionally, these previous mapping approaches were often unsuccessful because the location of the access points was assumed to be known, when, in fact, the location of the access points was sometimes not known. As a result, these previous approaches have been unable to allow mobile clients to seamlessly move between different systems and within different systems. Additionally, since the location of the mobile client often became unknown, providing network services that depended upon knowing the mobile client location became expensive, difficult, and/or impossible to achieve.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein.

System and method for location determination for mobile clients