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Abstract-Nowadays, several systems are available for outdoor localization, such as GPS, assisted GPS and other systems working on cellular networks. However, there is no proper location system for indoor scenarios. Research into designing location systems for 802.11 networks is being carried out, so locating mobile devices on global networks (GSM/cellular + GPS + WLAN) finally seems feasible. The technique presented in this paper uses existing wireless LAN infrastructure with minor changes to provide an accurate estimation of the location of mobile devices in indoor environments. This technique is based on round-trip time (RTT) measurements, which are used to estimate distances between the device to be located and WLAN access points. Each RTT measurement estimates the time elapsed between the RTS (Request-to-Send) and the CTS (Clear-to-Send) frame of the 802.11 standard. By applying trilateration algorithms, an accurate estimation of the mobile position is calculated.

Abstract-The state-dependent rejection scheme (SRS) provides a common framework for analysing existing handoff schemes and for designing new ones easily. Designing new schemes is made simple by determining the appropriate set of state-dependent probabilities. The Markov analysis of SRS is simple and useful for drawing initial conclusions on handoff strategies. The analysis and simulations carried out here demonstrate the capability of SRS to adapt to different mobility and load scenarios and to achieve good performance while targeting quality of service performance metrics.

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