Showing papers by "Takeshi Kubo published in 2015"

Mean free path applied to message dissemination in opportunistic networks

Abstract: Opportunistic networking including Delay-/Disruption-Tolerant Networking (DTN) has become an increasingly real possibility since there are a huge number of mobile devices, such as smartphones, all over the world. DTN is expected to find promising applications, such as message dissemination in a disaster-struck area, and offloading mobile data traffic onto DTNs in urban areas. One of the potential issues that may confront these applications is that opportunities for message relaying are limited since smartphone users are sparsely distributed among base station cells. In order to disseminate message efficiently, it is important to be able to accurately evaluate DTN performance, such as message dissemination coverage, and time. In this paper, we propose a novel yet simple analytical model of message dissemination in DTNs by applying the concept of mean free path. The mean free path is the average distance that a particle (e.g., an atom or a molecule) travels between successive collisions (in physics jargon). The basic idea is that by mapping a particle in three-dimensional space to a node in two-dimensional space, a meeting between two nodes is represented as a collision between two particles. We also perform simulation experiments in order to validate our model.

Method for generating graph information and node device

Abstract: PROBLEM TO BE SOLVED: To provide a method by which a node device generates graph information for specifying a convex closure-shaped area and corresponding to the relative physical relations of nodes, and the node deviceSOLUTION: In a method according to the present invention, each node device searches for one or more groups including a plurality of node devices corresponding to a prescribed range of coordinates relative to the node device itself and saves the searched group In this method, each node device determines, on the basis of the searched group, a grid node device present in an XY coordinate plane associated with a starting-point node device and included in a grid graph generated starting from the starting-point node device On that occasion, each node corresponding to coordinates other than the X-axis and Y-axis coordinates determines the device itself to coordinates of the grid graph after both of upstream nodes, among one hop node included in the searched group, are determined as nodes on the grid graph

Position management server, program and method for transmitting acquisition range list to mobile terminal

Abstract: PROBLEM TO BE SOLVED: To provide a position management server and the like that are capable of reducing the whole number of processes of position registration processing and paging processing without increasing a processing load on the position management server.SOLUTION: A position management server for transmitting an acquisition range list of base stations with which a mobile terminal can communicate to the mobile terminal includes: base station storage means for storing the position of each base station relative to the whole of a management position range regarding a plurality of base stations within the management position range the server manages; acquisition base station number setting means for setting an acquisition base station number included in the acquisition range list less for a mobile terminal that communicates via a base station situated in the fringe of the management position range; and acquisition range list creation means for creating an acquisition range list on the basis of the acquisition base station number per mobile terminal.