Research On Queris For Location-Based Services

Location-based services bring convenience to peoples’real life. For example, navigation services can provide people path-guide help so that people can never lose their way in a trip. Taxi services in smartphones can help people find taxis and thus save much time for taxi calling. Location-based service systems that record a great number of trajectory data can offer great support to governments and enterprises. For instance, governments can query and analyze trajectory data to find the migration tendency of people. Companies can mine users’trajectory information and further provide personalized services. Therefore, location-based service has becoming a hot research issue in both academia and industry.Previous location-based services are mostly towards outdoor environments. With the rapid development of RFID and blue-tooth technologies, indoor positioning becomes possible, leading to the development of indoor location-based services such as indoor navigation, object tracking, and location-based marketing in shopping malls.This paper mainly focuses on two types of queries in location-based services, i.e., volunteered location-based query and indoor spatio-temporal range query. Query is a key technology to support location-based services. As there are various user demands for location-based queries, we have to explore new location-based query processing techniques for different queries. The two queries discussed in this paper are both new problems, which have not been studied in previous researches. This paper aims at providing new references for the development of location-based services.The main contributions of this paper are summarized as follows:(l)We study a new kind of query called Volunteered Location-based Query and provide a processing framework based on weighted imprecise Voronoi cells. First, we give the definition for Volunteered Location-based Query and introduce the concept of weighted imprecise Voronoi cells. Then, we propose a processing framework for Volunteered Location-based Query and filter-refinement algorithms for weighted imprecise Voronoi cells. Finally, we conduct experiments to evaluate the performance of weighted imprecise Voronoi cells and the effectiveness of the volunteered location-based query.(2) We study the problem of spatio-temporal range query in the scenario of indoor space, and propose an algorithm of probabilistic threshold spatial-temporal range querying based on CR-Tree. Aiming to resolve the shortcomings of indoor location-aware technologies, we define the probabilistic threshold spatio-temporal range query in the context of indoor space. Then, we analyze the uncertainty of indoor moving objects’ locations by combining indoor space and the features of moving object trajectories, and further propose the probabilistic estimation of spatial-temporal range querying. Finally, we design a new trajectory index based on CR-Tree and propose a kind of two-step query architecture to solve the range query. We perform experiments on synthetic data and the results suggest the effectiveness of our proposal.