2004), "GNSS Indoor Location Technologies

Abstract. This paper presents an overview of GNSS-based indoor location technologies. Current and emerging users and their potential requirements are first discussed. Signal attenuation and multipath caused under indoor environments are described. The basic method to acquire and track attenuated signals, namely longer integration of signal measurements, is summarized. The need for assisted GPS is addressed. Availability and accuracy performance currently achievable under various conditions (wooden structure building, single family residence, large sport facility) are illustrated through selected test results. The limitations of current technologies and potential enhancements are discussed. These include measurement noise, existing signal structure and future enhancements, frequency and time errors, user motion, sensor aiding such as ultra-tight integration, and solution reliability and continuity. The paper concludes with a discussion of receiver testing standards. The possibility of using a GNSS hardware simulator to create reproducible indoor environments in order to overcome the controllability issue encountered with real environments is analysed