| As a kind of new strategic industry,location based service(LBS)has been widely applied in our daily lives which is indispensable in economic development and social activities.With the rapid promotion of society and economy,the quantity of large buildings is increasing fast and the requirement of high precision indoor positioning is urgent in anti-terrorist operation,emergency rescue,wireless sensor network,personal LBS and so on.Indoor Positioning Supplement System(IPSS)is one of the main components and effective supplement for indoor positioning signal resource to resolve the positioning signal coverage of blind area in complicated indoor environment based on current 2G/3G communication network and existing equipment.This paper focuses on the key technologies of IPSS and the prototype system is designed which is tested in actual application environment.The detailed research contents and achievements are as follows:(1)An acquisition method of high accuracy frequency source in IPSS is researched in detail.Positioning signals from outdoor base stations are acquired by RF front end and tracked by the carrier loop and code loop adjusting.After that,positioning signals are locked and synchronized to extract the high accuracy frequency source applied for IPSS in low cost and high accuracy unified with outdoor positioning system.In practical test,the method satisfies the need of the accuracy and stability in time-frequency reference for IPSS with high frequency accuracy,quick start and low drift rate.(2)According to the problem of time synchronization between two indoor positioning systems,the characters which effects time synchronization of replication importantly are analyzed in code loop.Based on establishing address mapping relationship between external and internal code in one to one correspondence,Accumulation errors in code can be removed to realize excellent synchronous replicating between external and internal codes.(3)According to the problem of signal coverage in Indoor Mobile Communication Supplement System,through establishing indoor signal fading model MRLM,we analyzed positioning signal strength vertical and horizontal distribution in four situations including single indoor supplement antenna in one floor,single antenna in several floors,multi-antennae in one floor and multi-antennae in several floors in section II.In the fading model,we considered propagation effects from Rice fading for light-of-sight(LOS)condition and Rayleigh fading for non-light-of-sight(NLOS)condition.Meanwhile,considering the difference between positioning and communicating(mainly on number of received signals and D-value of strong to weak),we simulated current antennae distribution of IMCSS to judge whether they satisfy positioning demand in section III.And test in actual indoor environment was accomplished.The results demonstrate that current indoor antennae can meet positioning demand basically which can cover most inner area in large buildings.Indoor positioning for LBS can be realized based on current communication infrastructure.(4)The structure of IPSS on utilization of current Indoor Mobile Communication Supplement System(IMCSS)is proposed.The system including indoor multichannel amplified and synchronized positioning signal from single source is designed and realized based on supplement antenna and Repeater(RPT)in IMCSS.The message frame in broadcasting system is designed.The production standard and antenna naming rules are proposed.The actual performance of IPSS is tested to realize seamless coverage of indoor positioning signal in large buildings. |
