Ad-Coop Positioning System: Embedded Kalman Filter Data Fusion

Abstract

In this entry, we propose an innovative solution for positioning determination in 4G wireless networks by introducing the ad-coop positioning system (ACPS). The ACPS is supported by a hybrid cellular ad hoc architecture, where the cellular network has a centralized control over the ad hoc connections among pairs of mobiles. Specifically, P2P communications are exploited in a mesh fashion within cellular-established clusters for cooperation-aided localization purposes (from that, the word ad-coop is derived). The major contribution of this work is the design of an embedded Kalman filter data fusion (EKDF) method for the ACPS, which appropriately combines the available longand short-range location information. The numerical results shown in the entry demonstrate that the ACPS enhances the location estimation accuracy with respect to conventional hybrid positioning techniques in cellular networks. The rationale for introducing short-range communications within the cellular framework is mainly due to the need: 1) to support P2P high-speed wireless links between the MSs in the cell; and 2) to enhance the communication between an MS and the home base station (BS) by fostering cooperative communication protocols among spatially proximate MSs. The communication enhancement primarily refers to a higher link reliability, a lower energy consumption, a larger coverage, and a higher spectral efficiency, which can be achieved by exploiting exclusive cooperative stations [e.g., relay stations (RSs) strategically deployed by the operator] or short-range communications among neighboring MSs. Since the work on wireless location has mainly concerned the previous generations, how to implement the location service in such a system is an open area for research. Usually, wireless location technologies mainly involve the measurements of the time of arrival (TOA), the time difference of arrival (TDOA), the angle of arrival (AOA), or the received signal strength (RSS) of radio signals either received or transmitted by an MS. Specifically, it can be recognized that: 1) The dominant wireless location technologies for cellular networks are based on TOA, TDOA, and AOA measurements. Whereas TOA-based schemes require a tight synchronization between the clocks of the transmitting BS and the receiving MS, TDOA-based schemes are free from this restriction, but their accuracy is highly dependent on the relative geometric location of the BSs. Generally, both TOAand TDOA-based schemes achieve better accuracy than AOA-based schemes, but they both require at IntroductIon Geolocation, i.e., location estimation in terms of geographic coordinates of a mobile station (MS) with respect to a fixed reference point (FRP), has gained considerable attention over the past decade, especially since the FCC passed a mandate requiring cellular network providers to generate accurate location estimates for Enhanced 911 (E-911) services. This has boosted the research in the field of wireless location as an important public safety feature, which can also add many other potential applications to future cellular network systems: user routing and navigation, location-sensitive billing, information browsing, fraud protection, user/asset tracking, fleet management, ITSs, mobile yellow pages, planning for networking, catching of information closer to the user, managing and enhancing wireless resource allocation, and system design and management. Unlike the existing 2G and 3G wireless networks, which achieve low data rates and are mainly aimed, respectively, at voice and video communications, the 4G wireless network is expected to supply the increasing population of mobile users with a various range of appealing services (from pop-up advertisements to locationbased and interactive or on-demand services—so called IP datacasting), which will definitely require a technological improvement in terms of localization accuracy, data rate, energy consumption, coverage, and spectral efficiency. Interesting solutions to achieve such requirements rely on the use of a combination of the cellular network model with the P2P one, which is usually used only in a special class of wireless networks called ad hoc networks. Ad-Coop Positioning System: Embedded Kalman Filter Data Fusion