Doppler Location Based on Two-Dimension Searching in Orthogonal Complement Space in DAS

A location method of the user equipment (UE) in distributed antenna system (DAS) is presented, which uses the technique of the velocity measurement based on Doppler frequency shift. The location equations are formed from Doppler shifts of remote antennas (RAUs). Due to the nonlinear nature of the problem, the solution must be found by the grid searching. However, when the error of the Doppler measurement is a Gauss random variable, the solution can be achieved easily by a two- dimension searching in orthogonal complement space, i.e. the search is only performed in a two-dimension space (the position space) instead of the normal four-dimension space (both the position and the velocity spaces). Simulation results show that the proposed method can approach to a high precise of the UE location.