Research Of Terminal Localization Technology In LTE System

As a new generation of mobile communication system, Long-term evolution(LTE) technology will be the core of the network to carry mobile data services and as an extension of 3rd generation technology, it has been deploymented commercially both at home and abroad. At present, location based service applications emerge in endlessly, such as electronic maps, good food guide, travel guide and so on. With the rapid development of mobile communication network, people’s demand for terminal localization accuracy is growing, so the research of LTE user terminal position technology has an important practical significance and applicable value.According to the LTE positioning protocol, there are three types of LTE positioning technologies: Assisted Global Navigation Satellite System(A-GNSS), Enhanced Cell ID(E-CID) and Observed Time Difference of Arrival(OTDOA). Among which, E-CID positioning technology is easily to be implemented and it has a low hardware requirement, but its positioning accuracy depends on the the cell area, but the localization of terminals can only be estimated roughly in the positioning process. A-GNSS positioning technology has a high positioning accuracy, but its power consumption is larger and the implementation complexity is higher, and the positioning estimation of terminals can’t be realized in some places such as indoor or downtown, where the satellite signal can’t coverage. OTDOA positioning technology is the most used method in LTE positioning system. Compared with E-CID technology, its positioning performance is better. Compared with A-GNSS technology, it needn’t change terminals, thus, OTDOA positioning technology has become a hot research direction of LTE user terminal positioning technology. The main contents of this paper are as follows:Firstly, the research background and research significance of positioning technologies are introduced in this paper. And the research statues at home or abroad of all positioning algorithms in cellular network is stated, Then wireless positioning systems and algorithms that suit for LTE positioning are stated. The research difficulties that LTE positioning technology faced are analyzed. The LTE positioning solutions, hyperbolic positioning model based on OTDOA, eNodeB(Base station) distribution topology structure in LTE positioning system and the evaluation indexes for terminal positioning accuracy are all discussed in this paper.Secondly, the positioning principle and the advantages and disadvantages of existed classical positioning algorithms in cellular network are stated in this paper. Meanwhile, the influences of different numbers of eNodeB, different cell radius, difference measure noise on the typical positioning algorithms are verified under idea channel environment.Then, the NLOS error model is introduced in this paper, the influence of NLOS error on LTE user terminal positioning performance is stated, and a method to identify the NLOS error is analyzed and discussed. The eNodeB that contains NLOS error is identified through the simplified residual analysis decision method. Aiming at the non-line-of-sight propagation situation, an improved LTE user terminal positioning algorithm based on the classical algorithms is used to suppress the influence of NLOS error on the positioning accuracy. The OTDOA error priori information of improved algorithm needn’t to be known, the LTE user terminal localization is accurately estimated using the idea of hierarchical coordination location, and a localization problem when the eNodeB combination is a linear array in residual weighting algorithm is resolved at last.Finally, this paper summarizes the full text, and makes a summary for the future research direction.