Yoichi Shinoda

Information filtering based on user behavior analysis and best match text retrieval

Information filtering systems have potential power that may provide an efficient means of navigating through large and diverse data space. However, current information filtering technology heavily depends on a user’s active participation for describing the user’s interest to information items, forcing the user to accept extra load to overcome the already loaded situation. Furthermore, because the user’s interests are often expressed in discrete format such as a set of keywords sometimes augmented with if-then rules, it is difficult to express ambiguous interests, which users often want to do. We propose a technique that uses user behavior monitoring to transparently capture the user’s interest in information, and a technique to use this interest to filter incoming information in a very efficient way. The proposed techniques are verified to perform very well by having conducted a field experiment and a series of simulation.

An energy efficient routing scheme for mobile wireless sensor networks

Research on wireless sensor networks has recently received much attention as they offer an advantage of monitoring various kinds of environment by sensing physical phenomenon. Among various issues, energy consumption is one of the most important criteria for routing protocol in wireless sensor networks (WSNs). This paper introduces an energy efficient clustering algorithm for mobile sensor network based on the LEACH protocol. The proposed protocol adds feature to LEACH to support for mobile nodes and also reduces the consumption of the network resource in each round. The proposed protocol is simulated and the results show a significant reduction in network energy consumption compared to LEACH.

StarBED and SpringOS: large-scale general purpose network testbed and supporting software

New technologies for the Internet should be evaluated on environments dedicated to experiments, in order to avoid influences to critical services on the Internet. Generally software simulation and small testbed using real nodes are used to satisfy these requirements. There are several stages in developing new technologies, however, and these technologies may not satisfy requirements for all stages.We pointed the gap between the Internet and environment for experiment, especially in aspects of scale, complexity and reality. We proposed and implemented StarBED which is a testbed based on lots of actual nodes, in order to build large-scale, complex and realistic environments for experiments. StarBED consists of 512 PCs and switches which connect these PCs. The PCs on StarBED are designed to run 10 virtual PCs on a physical PC. It enables to build a topology for experiments using up to 5120 nodes. It is difficult to manage and control such a lot of nodes. We also designed and implemented SpringOS, which is a supporting software for making experiments. SpringOS makes the topology and drives the scenario for experiment according to the users configuration automatically.Many experiments were performed on StarBED, and this shows StarBEDs effectiveness.

Automatic configuration and execution of Internet experiments on an actual node-based testbed

Software simulators are widely used for validation and evaluation of new network technologies and services. Using software simulators is a good way to validate algorithms or observing microbehavior of communication protocols. There are, however, problems with software simulators. Most software simulators require target systems to be described under their own modelling scheme, often using their own modelling language. These descriptions are usually different from what will actually be running as products. It is clear that these products should be validated someway. Time required to run software simulation become problematic also, as we try to simulate realistic target system under realistic environment where nontrivial aggregation of complex network services come into play. We adopt an approach to prepare a configurable testbed using actual nodes. Experiment topologies are created on this testbed virtually without changing physical connections, because the cost of building such experiment environments is very large. Since users of such testbed have to perform many steps to execute the desired experiments on such environment, we design the system that supports the users to execute their experiments. Using our system, all the user have to perform is preparing a experiment configuration file. Our system will execute experiments according to the configuration file. This paper shows the design of our supporting system models, steps of experiment with our system and an example of users scenario.

A load-aware routing metric for wireless mesh networks

Routing metrics play a critical role in wireless mesh networks (WMNs). Several metrics have already been proposed but none of them can effectively capture both local traffic load and hidden node issues. This paper proposes a load and interference-aware routing metric for wireless mesh networks, named contention window based (CWB) metric. Our metric assigns weights to individual links based on both channel utilization and the average contention window used on these links. The individual link weights are combined into path metric that accounts for load balancing and interference between links that use the same channel. Thus the CWB metric helps the routing protocol to balance traffic and improve network capacity by avoiding routing traffic through congested areas. The preliminary quantitative experiments show significant improvement over hop-count based method when using the proposed metric.

A Multi-Purpose Wireless Network Emulator: QOMET

In this paper we present the design and usage of the multi-purpose wireless network emulator that we develop, QOMET. QOMET implements a two-stage scenario-driven approach to wireless network emulation. We give here the details of the improved model and additional functionality that make it currently possible to use QOMET to convert a real- world scenario to a sequence of network-condition descriptors for a wide range of experiments. QOMET was used on a real network testbed to perform experiments involving emulated 802.11 a/b/g WLAN technology over wired networks for several types of scenarios. We shall illustrate this in the final part of the paper, with emphasis on networked robot emulation.

QOMET: A Versatile WLAN Emulator

In this paper we present the design of QOMET, the wireless LAN (WLAN) emulator that we develop. Our approach to WLAN emulation is a versatile two-stage scenario-driven design. In the first stage a real-world scenario representation provided by the user is converted successively into physical, data link and network layer effects that correspond to the emulated WLAN scenario. The output of the first stage is a description of the network states at successive moments of time, which is used in the second stage to accurately reproduce the wireless environment conditions by means of a wired-network emulator. We give here the details of the overall model that makes it possible to accomplish this conversion in QOMET. We then present our test methodology and illustrate our approach by several experimental results.

Experiments of collecting WWW information using distributed WWW robots

This paper presents the experiments of collecting the documents on the WWW using distributed WWW robots. We propose distributed WWW robots to collect the documents quickly. Our final goal is to collect all of the documents on the WWW in Japan within one day. Currently, eight distributed WWW Robots are running in Japan. The experimental results show that we are able to gain 5.8 to 9.7 times speedup when four distributed WWW robots are placed at different places in comparison with when only one WWW robot is used.

QOMB: A Wireless Network Emulation Testbed

In this paper we present QOMB, a testbed we designed and implemented for the evaluation of wireless network systems, protocols and applications. The testbed uses the wireless network emulation set of tools QOMET so as to reproduce in a wired network, in real time, the wireless network conditions corresponding to a given scenario. In this context QOMET also provides support for features such as realistic virtual 3D environments, and node mobility generation. The infrastructure of QOMB is StarBED, the large-scale network experiment testbed at the National Institute of Information and Communications Technology, Hokuriku Research Center, in Ishikawa, Japan. The multi-hop wireless network emulation experimental results related to OLSR performance analysis in mesh networks and MANETs illustrate the main features and the usability of QOMB.

An interference and load aware routing metric for Wireless Mesh Networks

This paper proposes a load and interference-aware routing metric for wireless mesh networks, named Channel Utilisation and Contention Window Based (C2WB) metric. Our metric assigns weights to individual links which are proportional to the links service times estimated from both channel utilisation and the average contention window of the CSMA/CA mechanism. The path metric, combined from individual link weights, accounts for both load and interference of the links on the path. Thus the C2WB metric helps the routing protocol to balance the traffic and to improve the network capacity by avoiding routing the traffic through congested areas.