Location Based Services

With the development of GIS (Geographic Information System) and mobile communication, the need for the mobile information services grows rapidly. In the case of the limit of LBS (Location Based Services) bandwidth, how to provide high-quality and high-efficiency geographic information service to users is the task we will face.A LBS system's simulation is implemented in this article, which consists of data-base server, GIS server, communication platform and mobile terminal. The whole steps of the simulation is as the followings: Firstly, data transmission on wideband CDMA communication platform is simulated by Matlab; Secondly, the SQL Server database is managed with ArcSDE; Finally an integrated system model is set up on ArcGIS platform using ArcObjects component technology. A service mode of push technique combined with adaptation method is used for the system's simulation. In the meanwhile, for saving channel resource, an information exchange scheme trying to minimize the exchanging frequency while satisfying QOS is presented in this paper.The functions implemented contain two aspects. On the one hand, the main functions on mobile terminals are designed for users, including map-scaling, map-roaming, distance-measuring, query operation, displaying the current location of the user, etc. On the other hand, the functions of information exchanging between the terminals and the server are realized on the server, such as users tracking, information report processing, etc. In addition, the functions such as the query and management of map data and user's track enquiry are also realized. In the last part of this paper, several main factors that may affect the efficiency of the algorithm are analyzed based on the study of the conventional shortest path algorithm-Dijkstra algorithm, and then the optimized arithmetic of shortest path planning is presented according to the city traffic network's character. The experimental results show that the efficiency of modified algorithm is dramatically improved.