Wireless Communications: Principles and Practice
Wireless Communications: Principles and Practice
Relative location estimation in wireless sensor networks
IEEE Transactions on Signal Processing
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In this report we introduce a "QoS Seeker" system for VoIP over 802.11b. QoS Seeker addresses the realistic situation where the QoS delivered to an end user's wireless VoIP application is a complex function of location and time. It attempts to dynamically inform the user of the location he should go to in order to obtain the optimal QoS for the current VoIP connection. To achieve its goals QoS Seeker continuously collects position information and VoIP QoS metrics - such as packet loss, packet delay, and received signal strength, from all connected users. This information is coupled to adaptive prediction technology in order to predict the future QoS metrics at all locations within the area spanned by the wireless network. We present results from various experiments of this system, where the positioning information is obtained from GPS devices embedded on mobile laptop systems and smaller hand-held devices. We also present simulations of a large scale QoS Seeker system which determines the conditions under which QoS Seeker would not function usefully. The effect of realistic position errors are also investigated on both real data and simulated data, and the usefulness of the predictive algorithms embedded within QoS Seeker are analyzed. Both the experiments and simulations show the viability and usefulness of the QoS Seeker system for VoIP applications in a wide range of circumstances.