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Ubiquitous positioning requires services that are supplemental to the existing Global Positioning System (GPS). For spaces where GPS does not work (indoors, canyons, etc.) augmented or enhanced positioning systems are necessary. For such systems to function appropriately users must have a GPS-like experience. In essence, users of supplementary positioning systems must trust the information these systems deliver. In order to develop systems that mimic the trust generated by GPS and to better understand the implications of features or changes to such a positioning system we believe a conceptual model of positioning system trust is necessary. Such a conceptual model must consider several aspects of the user and the system. The system must be accurate, with an informative User Interface that is transparent (provides context and background on positions and how they are calculated), it must use verified source data, and provide information that supports a range of users. In this paper we present the essential elements of trust for enhanced or supplementary positioning systems.

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Location Based Services (LBS), which are supported by ubiquitous location finding and positioning information, have become increasingly popular. These services are integrated with various wireless technologies (i.e. cellular, WiFi, and Bluetooth) on mobile devices that establish necessary location information. While each of these technologies contributes to the integration, development and success of LBSs, WiFi has been the most widely employed as an alternative to the Global Positioning System (GPS). Several commercial WiFi-based positioning systems (WPS) are available to the public to extend positioning coverage to places where GPS is unreliable or unavailable; however, these commercial WPSs often fail to deliver GPS-like positioning. The coarse positioning accuracy of commercial WPSs may be caused by unreliable or unsecured databases, which contain the essential WiFi-array information to produce local positioning. Knowing this, the quality of WiFi-based positioning services can be enhanced by improving the quality of a database with well-surveyed and accurate information. The Saskatchewan Enhanced positioning System (SaskEPS) is designed to reduce common errors in WPS. SaskEPS's positioning accuracy and consistency is supported by a thoroughly validated Access Point (AP) database. It has been tested in several buildings at the University of Saskatchewan and successfully provides GPS-like positioning accuracy. Our tests have also begun to elucidate the role of WiFi density in ensuring GPS-like positioning accuracy in indoor spaces. In this paper, we investigate the quantitative relationship between WiFi density and SaskEPS's overall positioning accuracy.

In this study, an integer programming approach is introduced to construct unequal error protection (UEP) codes for a multiuser broadcast communication system. The authors establish integer programming models for both binary and non-binary UEP codes. The results show that optimal UEP codes can be constructed such that their code lengths achieve the integer programming bounds. Based on the bounds, the authors investigate asymptotic behaviour of code rates with symbols in GF(q), and the authors present performance analysis of multiuser communications over a degraded broadcast channel with the optimal UEP codes.