Research On Nearest Neighbor Location-based Spatial Query In Mobile Enviroment

Mobile environment is an irresistible trend of network development. And applications under this environment are becoming more and more popular. Location-based spatial query is an essential application in mobile environment while nearest neighbor query is one of the most important kinds of location-based spatial queries. The primary target of nearest neighbor query is to make mobile users acquire location information more quickly and accurately. Though traditional nearest neighbor query techniques have been successfully employed in practical application fields, and the query performances obtained by them are recognized to some degree, however, people put forward the higher requirements towards the technological achievements. This implies that it needs to develop new nearest neighbor query approaches to meet the demands of people with the progress of the times and the development of science and technology. Therefore, the research on the corresponding project has great theoretical significance and widespread application prospect.This paper comprehensively reviews abroad and domestic research status and basic knowledge of nearest neighbor query under mobile environment. The emphasis is placed on the nearest neighbor query under static environment and dynamic environment. For the former, the query mode is established as the focused research, and then a new query algorithm based on sharing the information of adjacent mobile clients is put forward, which makes full use of time interval of waiting for the results to obtain shared information for the sake of reducing repose time. For the latter, index technique of mobile objects is selected as the key research issue. A new continuous nearest neighbor query algorithm based on the improved index structure is presented, which enhances query efficiency.The main achievements about this paper are described as follows:1. Present related knowledge of nearest neighbor query under mobile environment. According to the nearest neighbor query under static environment and the location of spatial query results, P2P technique is introduced to share the information of adjacent mobile clients.2. A new query nearest neighbor algorithm called SRNN, which is based on sharing the information of adjacent mobile clients, is put forward. Meanwhile, nearest neighbor query process under static mobile environment is illustrated. Simulation experiment is conducted in order to validate the performance of the proposed method. Experimental results show that the method can reduce the waiting time of mobile clients and make information for users obtained in time.3. Considering the specificity of velocity distribution of mobile objects and the diversity of direction of movements, an indexed structure called MDTPR-tree is presented.4. A continuous nearest neighbor query algorithm based on MDTPR-tree named MDCNN is raised. In addition, nearest neighbor query process under dynamic mobile environment is illustrated. Simulation experiment is conducted in order to validate the performance of the proposed method. Experimental results demonstrate that MDCNN can reduce disk accesses.5. An application example of nearest neighbor query is given, which shows that the proposed methods in this paper are feasible and effective.