Shigeaki Tagashira

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As microblog services become increasingly popular, spatial-temporal text data has increased explosively. Many studies have proposed methods to spatially and temporally analyze an event, indicated by the text data. These studies have aimed a extracting the period and the location in which a specified topic frequently occurs. In this paper, we focus on a(More)
In this paper, we propose a new routing protocol for mobile ad-hoc networks (MANET), which have attracted considerable attentions in recent years as a tool to realize flexible and robust communication environments in many critical application fields. The proposed protocol, called LQ-routing, is a proactive routing protocol based on the Q-routing protocol(More)
In this paper, we propose several distributed zone partitioning schemes for content-addressable networks (CAN), that is known as a pure peer-to-peer system based on the distributed hash table (DHT). The main objective of the proposed schemes is to balance the load of nodes in the CAN system, in such a way that every node receives almost the same number of(More)
Multipoint relays (MPRs) support efficient flooding of topology control messages in OLSR. Since the shortest path is constructed as a sequence of MPRs, MPRs are the nodes of the backbone network. In this paper, we explore dense wireless multi-hop networks, and analyze the density of MPRs in such networks. We explain three properties to increase the number(More)
In this paper, we propose a new localization scheme for wireless sensor networks consisting of a huge number of sensor nodes equipped with simple wireless communication devices. The proposed scheme is based on the point-in-triangle (PIT) test proposed by He et al. The scheme is actually implemented by using Bluetooth devices of Class 2 standard, and the(More)
A critical problem with location fingerprinting is the considerable time and effort spent measuring received signal strengths at all location candidates to create the survey database. To reduce this cost, existing methods use a signal path loss model to interpolate part of the survey database from data actually measured at location candidates. However, the(More)
In this paper, we propose three heuristics for highefficiency selections of MPRs (multipoint relays) in link state QoS routing protocol: MIMS (maximizing integration metric selection), MQES (maximizing QoS-efficiency selection), and MCIS (minimizing cost-inefficiency selection). The basic approach of these selections is to determine a smaller set of MPRs(More)