Research On Seamless Position Techniques In Ubiquitous Environment

With the rapid development of wireless communication network,the location information is becoming more and more important for people's life,which makes the demand for location based service(LBS)in various fields increase.The current Global Navigation Satellite System(GNSS)has been able to satisfy most of the outdoor navigation requirements.At the same time,indoor positioning techniques have also been rapid development in recent years.However,indoor localization and outdoor localization are developed independently,and there does not exist mature technology to realize the perfect integration of them.Therefore,the study of seamless position technique in ubiquitous environment has become a new hot point of wireless positioning technology.According to the study and review of the related literature,this paper analysis the developing situation of the current wireless positioning and seamless positioning technologies,and the seamless handover technologies in typical urban environment is studied,the specific work is listed as follows:Firstly,this paper introduces the key technology of seamless positioning handover between heterogeneous positioning systems,and the performance of GNSS under various typical positioning scenarios is analyzed.The signal-to-noise ratio(SNR)of the global positioning system(GPS)is then measured,and this paper analyzes the effect of GPS satellite elevation angle on SNR variation during indoor and outdoor handover;aiming at the defects of SNR value detection handover algorithm based on GPS signal,this paper proposes a positioning handover algorithm based on GPS,Wi-Fi and motion sensor.In this algorithm,the positioning terminal continues to detect the state of the GPS satellite signal,then the dual-threshold scheme decision method and the motion state monitoring are used to accomplish the handover decision in the transition area.The algorithm can effectively improve the stability of the whole switching algorithm and suppress the ping-pong effect that may occur during the switching process.Secondly,according to the proposed localization handover algorithm,an Android-based indoor and outdoor seamless positioning system software is designed,which includes the functions of signal fingerprint management,outdoor and indoor positioning,and positioning scene handover.In addition,this paper select the indoor positioning experiment environment,the collection of Wi-Fi signal fingerprint and the establishment of the fingerprint database are carried out;at last,the concrete realization method and key technology of each part are introduced.Finally,the performance of the designed seamless positioning system in this paper is test and analyzed in the experiment environment.The test results show that the system can realize the function of signal fingerprint information management and the indoor-outdoor seamless positioning.Compared with the conventional GPS cutoff handover decision method,the proposed method has higher stability and smaller handover time errors,and the precision of indoor localization can reach about 3m.