Chapter 9: Device Interactions in Location Determination

Overview

The HELD- and FLAP-based architecture discussed in previous chapters describes a structure whereby location measurement information is extracted from the access network, correlated with the device address information, and used to calculate the location of the device. This is the domain of the FLAP protocol. Device-LIS interaction occurs with the HELD protocol, but this is used for the conveyance of calculated location information, as opposed to the exchange of location measurements.

Any architecture that did not include the facility to utilize device-specific capabilities would be incomplete. Device measurements offer a greater range of options for location determination. Location determination techniques described thus far focus on the access network, where the final responsibility for location lies. This guarantees success to the extent that the network is in control of the available facilities, but device-based methods can improve the overall quality of the location information that is produced. This chapter will examine some of the options for using the device in location determination and investigate how this affects the location architecture.

The book has, until this point, concentrated on the way that the access network determines location. However, as introduced in Chapter 1, it must also be recognized that devices are capable of taking part in the location determination process. A device has a distinct advantage in this regard by virtue of the fact that it is actually at the location of interest. This fact can be exploited to improve the accuracy, precision, and reliability of location information.

A device may be able to take additional measurements that are not available to the access network. These measurements can be provided to the LIS in such a way that the device effectively acts as an ALE.

For example, devices may take measurements from nearby Radio Frequency Identifier (RFID) tags. RFID tags may only be readable to devices at a short range, and since RFID tags are passive, they cannot provide measurements to the LIS independently as an ALE.

Some devices are able to determine their own location. Devices with Global Navigation Satellite System (GNSS) capability, such as GPS devices, can take location measurements and calculate their position autonomously. This chapter describes how GNSS can be used by the LIS, including Assisted-GPS.