TDOA Indoor Localization System Based On Multipath Time Delay Estimation

With the growing demand for localization, indoor localization system is increasingly being used in daily life. Among them, TDOA indoor localization has been paid more and more attention for its high positioning accuracy, low complexity, easy to deploy, low cost. The key algorithm of TDOA localization system is time delay estimation(TDE) algorithm. For achieving better positioning accuracy in the indoor multipath environment, TDE algorithm used in the system is required to have a super-resolution capability and anti-multipath interference.Through analyzing and researching the existing super-resolution TDE algorithm and multipath TDE algorithm, this paper presents a super-resolution multipath TDE algorithm——Time Delay Grid(TDG) Algorithm. It is a TDE algorithm based on the cost function for minimizing the cost function as the guidelines for solving multipath signal parameters. By introducing a phase compensation matrix in the cost function model, the algorithm will separate phase noise caused by the frequency offset from the signal noise, so that the algorithm has strong anti-offset ability. To reduce the complexity of the algorithm, the algorithm through the least squares method and the one-dimensional iterative optimization method to achieve lower dimensional optimization, cost function value is only relate with multipath time delay point, we succeeded in reducing the number of parameters to be evaluated. For overcoming the low time resolution caused by the low sample rate of the device, the algorithm uses spline interpolation algorithm to obtain high temporal resolution and multipath signal delay value quantize multipath time delay as time delay grid points. The algorithm uses the optimal gradient descent as the search algorithm, which searches optimal delay grid point from the cost function profile corresponding to delay gird and uses its main signal path delay value as the delay estimate.In this paper, with the MATLAB simulation, it has been showed TDG can has good TDE ability in the effect of noise, short delay multipath, frequency offset, time drift and so on. Then, we do TDOA localization experiment by software radio in indoor environment. The result show that the TDOA indoor localization system based on TDG can achieve localization accuracy within 1m in indoor environment.