Study On The Key Technology Of TC-OFDM For High Precision Indoor Positioning Based On Mobile Base Station

In recent years,outdoor LBS(Location Based Services)has been widely applied in people’s lives with the application of GNSS(Global Navigation Satellite System).More than 80%time of people’s daily lives is in indoor environment.With the modernization of the cities,the number of large buildings is rapidly increasing,and the requirement of indoor LBS is dramatically increasing.GNSS can’t be used in indoor positioning because its’signal is too weak.Nowadays,indoor positioning systems are based on Wi-Fi,Zigbee,UWB(Ultra WideBand)and so on.However the coverage of these systems is too small,which makes the cost of indoor LBS is too much.So the indoor LBS application is hard to be popularized now.Mobile base station has wide indoor signal coverage,so,the indoor LBS can be popularized if the promble of high precision indoor positioning based on mobile base station be solved.In order to solving the prombles in indoor positioning based on mobile base station,such as NLOS(None Line Of Sight),multipath interference and user experience in indoor positioning,the key technology of TC-OFDM(Time&Code Division-Orthogonal Frequency Division Multiplexing)for high precision indoor positioning based on mobile base station was researched.And this work was supported by the national high technology research and development program of China under Grant No.2012AA120800.The main innovation and contributions in the dissertation are as follows:1)From the perspective of signal system,research has been done for the problems of multipath and cross-correlation interference faced in indoor positioning based on mobile base station.Firstly,the ranging performance of OFDM(Orthogonal Frequency Division Multiplexing)signal(mainstream in communication)and CDMA(Code Division Multiple Access)signal(mainstream in navigaion)were compared and analysed.And the complementary ranging features of the two signal systems in different multipath environment were found.Secondly,an analysis of CDMA cross-correlation-interference was made which comprised of 3 factors:signal frequency interval,spreading code period and integration time.Based on that,a micro-frequency-division signal system based solution was proposed to mitigate cross-correlation-interference.The above research laid the foundation of the the signal design and ranging which integrated OFDM and CDMA.2)For the requirement of integrated navigation and communication service,TC-OFDM signal was designed.TC-OFDM signal multiplexes communication(OFDM)and navigation(CDMA)signal in the some frequency and promoted navigaion performance without bad effecting on communication.A novel ranging method coupling of CDMA and OFDM was proposed base on TC-OFDM signal.It made the complementary ranging features of CDMA and OFDM to promote ranging performance in multipath environment.3)Reasearch has been done for the mitigating of NLOS error in TC-OFDM indoor positioning system based on mobile base station.NLOS model for high precision positioning was proposed.It fit NLOS distribution model and got the NLOS distribution in the area around user’s location.And the positioning equations with NLOS distribution function were established.The tests verified that the new method have a better performance than the positioning method based on fingerprint.4)Assisted TC-OFDM positioning based on IMU(Inertial Measurement Unit)and electronic map was reasearched for the improvement of user experience.Firstly,a novel method to detect moving direction through difference cross-correlation characteristics of accelerations was proposed.It can effectively detect pedestrian direction with sensors carried in uncertain attitude,which is a problem in PDR(Pedestrian Dead Reckoning)technique based on IMU now.Then,an indoor map matching method based on pedestrian motion was proposed to promote probability of success matching.It can be applied in indoor environment which has dense road network and rooms.Through the integration of PDR,map matching and wireless positioning technology,the indoor positioning performance was promoted effectively.5)The TC-OFDM experimental system was development and built in BUPT(Beijing University of Posts and Telecommunications).The indoor positioning profermance based on mobile base station was tested.The test result shows that the indoor positioning precision is better than 3m.This work laid the foundation of the application of TC-OFDM system.