Localization Of Unknown Emitter In Urban Environment

Localization of unknown wireless emitter nodes has received extensive attention over the last decades.It has taken the shape of the backbone of a growing number of the position-based applications in commercial networks,public services networks as well as military networks.To avoid disrupt and interference to systems,it is very important to localize unknown emitter nodes in wireless communication.The unknown emitter nodes may include radios operating without proper license and jammers causing to create disturbance in the communication of other systems.In urban environment,the localization of these emitters is difficult because of the interference caused by the buildings and towers.Several localization techniques have been developed to address this issue in the past.This thesis proposes a localization scheme that includes the characteristics of many proven localization and error correction techniques to estimate the location of the target unknown emitter in a Non-Line of Sight(NLOS)condition.The proposed localization scheme employs a Time-Difference of Arrival(TDOA)method to determine the position of the target emitter.TDOA method measures the difference in the arrival time of the received signal from the target object between synchronized and spatially separated receivers.Multiple sensors at known locations are used and the estimated TDOAs are obtained from the received signals by using the cross-correlation function at all the receivers.One of the sensors is taken as a reference sensor and the arrival signal delay time is calculated between the reference sensor and all other sensors.TDOA hyperbolas are calculated and plotted to estimate the location of the target emitter.NLOS error is added to one receiver and a Distribution Function(DF)is constructed to quantify the distribution density of the intersections of hyperbolas.A range measurement contained a positive NLOS error will be pushed far away from the estimated target emitter location.For NLOS identification,first the NLOS corrupted TDOA is calculated and then the LOS TDOA is subtracted from it which gives the NLOS error.NLOS error is subtracted from the corrupted TDOA to achieve the required estimated location.Modeling and simulation method is used to assess the performance of TDOA scheme.The simulation results confirm the validity of identifying the Non-Line of Sight(NLOS)error,hence the accuracy of the localization system is improved in noisy urban environment.