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Recently, Ultra Wideband (UWB) Time of Arrival(ToA)-based localization in Wireless Sensor Networks (WSNs)have received considerable attention. For a typical WSN operating in indoor environments, the localization performance can be degraded considerably due to the existence of non-line-of-sight (NLOS) channel conditions between the sensor nodes. In these(More)
A novel empirical approach is presented for modelling the path loss behaviour of the direct path (DP) between the transmitter and receiver, which is important for time-of-arrival-based indoor geolocation coverage characterisation. Using ultra wideband (UWB) measurements in four sites and three ranging scenarios, pathloss models at 500 MHz and 3 GHz system(More)
In this paper, we present a complete framework for accurate indoor positioning and tracking using the 802.11a WiFi network. Channel frequency response is first estimated via the least squares (LS) method using an orthogonal frequency division multiplexing (OFDM) pilot symbol. For accurate time of arrival (ToA) distance estimates in multipath environments,(More)
Distance based localization techniques have always been of interest among researchers. The free received signal strength index (RSSI) requires no extra hardware for distance measurement. Authors in this paper assume that RSSI based distance estimation technique will have some error due to noisy RSSI readings. The localization algorithm proposed here takes(More)
In this paper, cooperative spectrum sensing under perfect and imperfect feedback channels is investigated. In particular, the optimal number of cognitive radios (CRs) required to minimize the total error of the sensing process when a perfect/imperfect reporting channels is derived. We show that the total error is always greater than zero regardless of the(More)