Research On Mobile Computing And Location-dependent Information Services

Mobile communication technology becomes a hotspot of modern communication engineering development. Therefore its leading actor - personal communication system, with convenience and efficiency, is under developing. Wireless position technology and digital geographical information integrated mobile communication technology provide users a inteactive environment anytime and anywhere. This system can offer different information services, including mobile client's geographical location related services - location dependent information services, to different users. This is the focused issue of this paper.Toward wireless communication, position technology and digital geography information, this paper develops a location dependent information services system based on free open software. The aspects researched are:It introduces the concept of location dependent information services with its service platform, GIS, position system and wireless communication, to find research issue.System scheme design. According to different applications, it summarizes the configurations and features of mobile computing environment to provide data access at anytime and anywhere. Then it educes system requirements, using free open software - GRASS GIS, MapServer etc. to design location information services system which supports wire/wireless access.Constructing geographical information data. To satisfy user's demands is why the technology develops. According planar point query, it takes the method of membership function in fuzzy set theory to provide a more user-oriented approach to construct overlapping location-dependent data regions, called complementary void overlapping data regions. This structure, carrying more information with lessadditional storage, brings balance between perceived usefulness and responsiveness, energy consumption, and bandwidth contention in wireless communications.Client cache management. Cache technology can extend the user's mobility and decrease communication cost. Considering the features of location dependent data and the influences of data access probability, valid scope and storage size, it uses Rough Set to increase the cache hit rate.Finally this paper uses J2ME to simulate cache replace policy, and integrating GRASS GIS, MapServer and apache etc. to implement Internet-based WebGIS system under wireless LAN environment, easy-extending and replantable.