BITS Faculty Publications
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Item A TDOA measurement technique for asynchronous indoor localization system using UWB-IR(IEEE, 2016) Vashistha, AnkushIn this paper we have proposed a Time Difference of Arrival (TDOA) measurement scheme for practical asynchronous systems using low cost low power target nodes (called tags). The system performs localization of transmit only tags using an ultra wide band Impulse radio (UWB - IR). We use a known location reference node for synchronization between the receiving (or anchor) nodes. The clock of the reference node is considered to be a perfect clock whereas clocks of all other nodes, anchor nodes as well as target node, is assumed to imperfect. We formulated the equations to synchronize the clocks of the anchor nodes and estimate the TDOA range measurements between the anchor nodes. The equations were analyzed with the practical measurement results.Item Self calibration of the anchor nodes for UWB-IR TDOA based indoor positioning system(IEEE, 2018-02) Vashistha, AnkushThe problem of anchor nodes placement in indoor positioning systems is labor intensive and time consuming process. A self-calibrating scheme is proposed to determine the position of the anchor nodes using Ultra-Wide band impulse radio (UWB-IR). These positions can be further used to determine the position of the target nodes. The time difference of arrival measurement technique is employed to self-calibrate the anchor nodes. The proposed scheme is verified with the simulation results, as well as with an in house designed sensor nodes experimental setup.Item A novel E-DTDOA based one-way ranging using uwb-ir with unsynchronized anchors(IEEE, 2021) Vashistha, AnkushIn this article, a novel analytical equation is proposed to determine the equivalent time of arrival (E-TOA) for achieving sub-ns resolution, with much reduced analog-to-digital converter sampling frequency (in the order of 2-3 MHz). The timing information is extracted from high resolution channel impulse response, which is obtained using an equivalent time sampling (ETS) technique. The proposed E-TOA equation is different from the conventional real-time sampling equation due to the presence of an additional transmitter clock drift, and thus sensitive to both the transmitter and receiver clock drift variations. The validation of the E-TOA equation is carried out numerically using simulations along with experimental validation. The effect of timing uncertainties relating to the transmitter clock start time and the receiver clock offset is analyzed with variations in the transmitter and receiver clock drifts. With E-TOA measurements, an equivalent differential time difference of arrival based one-way ranging scheme for unsynchronized anchors is further proposed. It is thus demonstrated, using in house designed sensor nodes, that high ranging accuracy, in the order of few centimeters, can be achieved by utilizing the proposed analytical E-TOA technique, even with low sampling rate.