移动计算系统中的自适应位置更新策略

移动计算系统中一个很重要的问题就是管理移动客户机的实时位置.在现有商业的移动计算系统中,采用一种两层的体系结构.这种两层的结构不具有可扩展性,因而不能适应具有大量移动用户的新型移动计算应用.人们提出了一种新的层次结构的位置数据库结构,系统中的位置数据库组成一个树形结构以方便移动用户位置查找.尽管这种结构把位置更新及查询的任务在系统中的所有位置数据库中进行了分摊,它也有其自身的弱点:位置更新的代价较大及位置查询的延迟较长.研究了树形位置数据库结构中的位置更新策略,给出了一个位置变更的阈值计算方法,以使得位置管理的代价最少.

Adaptive Generation of Location Update in Cellular Mobile Computing Systems

An important issue in the design of a mobile computing system is how to manage the real-time locations of mobile clients. In the existing commercial cellular mobile computing systems, a two-tier architecture is used. However, the two-tier architecture is not scalable and is not suitable to the new mobile computing applications in which there are a very large of mobile users. In the literatures, a hierarchical database structure is proposed. The location databases of different cells are organized into a tree structure to facilitate the search of mobile clients. Although this architecture can distribute the update and searching workload amongst the location databases in the system, it has the problem of heavy location update overhead and long search delay. This paper studies how to generate location update based on the distance-based update method in the tree structure. A location update generation method is proposed to calculate the optimal distance threshold with the objective to minimize the total location management cost.