Study On Time Difference Of Arrival Based Wireless Positioning Algorithms In Cellular Networks

With the increasing development of the mobile communication technology, wireless positioning technology has attracted wide attention from many researchers and research institutions; it has become a novel focus in the field of wireless communications. The wireless positioning technology is by evaluating the wireless signal measurement of the wireless cellular network, such as the TDOA (Time Difference of Arrival), AoA (Angle of Arrival) etc., in order to directly or indirectly locates the mobile station position. TDOA positioning method is researched deeply in this article, the main innovations is summarized as follows:Introduces the basic principles of positioning technologies in LTE network and the basic knowledge about positioning in the LTE-A system, including positioning processes and frameworks in the LTE-Advanced system, and new positioning reference signal.Analyzes the mathematical model of the TDOA hyperbolic equations and does a detailed analysis of the Chan algorithm and its characteristics, points out the major technical difficulties to achieve the precise positioning of the mobile station in a mobile communication system and the measures to improve the accuracy. Then focus on analyzing3GPP Release9how to get the OTDOA positioning processes. By reading a lot of3GPP proposals and contributions to analyze the OTDOA simulation assumptions and simulation methods, and then build up a system-level platform and link-level platform. OTDOA positioning accuracy in the LTE system performance is obtained by simulation. Besides examine the theoretical lower bound of the TDOA method CRLB (Cramer Rao Lower Bound). Compare the simulation result of Cramer-Rao lower bound and the simulation result OTDOA positioning accuracy. Final chapter gives some innovative point of this thesis and introduces TDOA location algorithm in LTE-A network. By system level and link level simulation validates the positioning accuracy of the heterogeneous network Het-Net (Heterogeneous Network) CA (Carrier Aggregation) network. And then focus on TDOA enhancement algorithms. Due to the far and near effect in the mobile network, it leads to the difference of the reference signal’s SINR of serving cell and the reference signal’s SINR of neighboring cell is bigger than the threshold. The positioning accuracy is deteriorated. So this article the use of power control and beam forming algorithms can greatly lower down the SINR difference between the two reference signals from two different base stations in order to improve the positioning accuracy.