Research On Indoor Mobile Terminal Positioning Technology Based On The Inverse Propagation Model

Recently years, with the continuous development of communication technology,people’s demand for indoor positioning has become more and more strong. However,the accuracy problem is still a difficulty of indoor positioning. Many of the existinglocalization methods have various positioning limitations. Global positioning system isthe present most widely positioning technology. Its good positioning accuracy hassolved many practical problems. But its signal reaches the ground is weak, so it is notsuitable for indoor positioning. Therefore, we must study the new indoor positioningtechnology to make up for the inadequacy of GPS.Research shows that the main reason of the existing indoor positioning technologyprecision insufficient ideal is that we can’t obtain the accurate indoor channel model.Time reversal can overcome the multipath effect and accurately locate the targetposition under the known channel information. If we can find a way to predict indoorenvironmental information, then the indoor positioning accuracy will be greatlyimproved. Therefore, this paper presents a new positioning method, TR-FMM, indoorpositioning method based on inverse propagation model. TR-FMM is a positioningmethod through combining the inversion technique of time reversal and fast marchingmethod. The so-called inversion is actually TR, the meaning of time reversal, a kind ofpositioning technology by channel reciprocity principle between receiver andtransmitter to achieve time and space focusing at emission source location. Propagationmodel refers to the signal transmission channel. Because high precision positioning oftime reversal rely on accurate environment model, this paper improves the FMMalgorithm into the indoor to estimate channel model. TR-FMM method first obtainaccurate indoor channel model by FMM algorithm, then using the TR technology tolocate the indoor terminal accurately. Regard small mobile terminal (generally in the8*12cm) as the positioning target, the main work of this paper include:(1) Interpolation method improves the FMM algorithm to estimate the indoorchannel model which is the most close to the actual environment. From the wirelesselectromagnetic theory, the indoor channel information mainly depends on thedistribution of permittivity, so this paper will estimate indoor channel model by solvingtheεdistribution of indoor object. Not only creating the positioning environment for the inversion of TR, but also providing a new research idea for predicting indoorpropagation model.(2) The simulation positioning of TR-FMM has been made for indoor staticterminal (including the conditions of single terminal and multiple terminals) and mobileterminal. The results show that, the method can effectively locate and track mobileterminals, the average positioning error is about2cm, and the positioning error of theconventional TR method is about89.7cm, which greatly improves the positioningaccuracy of indoor small mobile terminal.(3) The simulation and comparison analysis on the performance of TR-FMMpositioning method has been made. Include the feasibility of the method, the stability,superiority, positioning high efficiency. Various aspects verify the location advantage ofinverse propagation model method.TR-FMM positioning method plays the advantages of TR and FMM. It not only canprovide the most close to the actual propagation model of the indoor environment, butalso can achieve precise positioning of the indoor small mobile terminals on the basis ofthe model, and has a high practical value.