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A lot of people have suffered and died due to sudden disasters (fire, earthquake, terrorism, etc) in the world. In sudden disasters, it is very important for evacuees to find out appropriate evacuation routes. We previously proposed the evacuation support system named as Emergency Rescue Evacuation Support System (ERESS). This system is based on MANET and aims to dramatically reduce the number of victims in sudden disasters. This paper deals with the evacuation route search which is one of the most important functions of ERESS. In this paper, we propose a new evacuation route search algorithm for route distribution of evacuees groups in fire disasters. In this algorithm, evacuees can evacuate more safely and immediately by avoiding the congestion passage. To show the validity of the proposed algorithm, we carry out performance evaluations by computer simulations. As the results, we show that more evacuees can evacuate effectively compared with the previous route search algorithm.

In recent years, transportation convenience is improved significantly by the spread of the automobile. However, traffic violation vehicles passing on the signal, hit-and-run, etc. are increasing with the increase of vehicles. To track a violation vehicle, recognition systems of the license plate using the image processing technology and cameras have been developed. However this system becomes expensive and complicated. To solve these problems, we have proposed a recognition method of the vehicle code using infrared laser radar. We set up a one-dimensional code created by reflectors on the vehicle, and acquire the vehicle information by reading the vehicle code by infrared laser radar. It can be constructed inexpensive system by using infrared laser radar. However, there is a problem that the number of code patterns is small, so the system cannot accommodate too many vehicles. In this paper, we propose a new code recognition method using time-sequence processing for infrared laser radar. We create a two-dimensional code by setting different type reflectors on vertical positions. Thereby we increase the number of code patterns. Through experiments, we demonstrate the effectiveness of the proposed method.

We have proposed a simple vehicular information acquisition scheme using infrared radar and reflector code in order to recognize vehicle information with low cost. However, since the size of the reflector code is so large and the number of code patterns is not so large, it is necessary to reduce the size and increase the patterns in order to be attached with vehicles. So we propose a new scheme using subdivided reflector code.

In this paper, various actions of a pedestrian with danger of leading to a traffic accident are analyzed. We have proposed a collision avoidance support system between pedestrian and vehicle. It is important to estimate the danger of the pedestrian. So we propose a new system by using pedestrian moving record.

Recently, indoor mobile robot navigation systems have been developed all over the world as the technology for assisting aged and physically handicapped people. Especially, the systems using passive RFID with features of low cost and simple composition have attracted attention over the years. However, in these systems, there are two serious problems. 1) A mobile robot performs the meandering moving. 2) A mobile robot is difficult to avoid obstacles. Hence, a moving correction method is required very much to solve the above two problems. In this paper, we propose a new moving correction method of a mobile robot using only passive RFID to improve the moving trajectory. This method reduces the serpentine moving of mobile robot and avoids obstacles by predicting obstacles and walls in front of the mobile robot. To show the effectiveness of the proposed system, we carry out the performance evolutions by computer simulations and experiments. As the results, we show that the proposed method can reduce the serpentine moving of the mobile robot compared with the conventional method and also can avoid obstacles.

The authors have proposed the Emergency Rescue Evacuation Support System (ERESS) for reducing human damage at disasters. The ERESS primarily intended to reduce the number of victims in panic-type disasters (e. g., fire, terrorism) and works under mobile ad-hoc networks (MANET). This system uses ERESS Mobile Terminals (EMTs) like smart phones and tablets. EMTs have an advanced disaster detection algorithm and sensors. They get data from sensors such as acceleration, angular velocity, and terrestrial magnetism. EMTs classify behavior of EMTs holders like walking and running, and detect disasters from escape actions. In this paper, the authors propose a new effective disasters detection method using statistics and a support vector machine (SVM). In this method, we introduce weight coefficient for each EMT holder according to his behavior statistics. Disasters simulation experimental results show the effectiveness of the proposed method.

Many people have got injured or lost their lives by sudden occurrences of serious disasters such as fires and terrorism. The fires spread from hour to hour. People may lose ways and have fatal damages. If people take a way, they meet with a terrorist, people are taken as hostages or killed. In these disasters, it is important to detect them and got information about them as quickly as possible. To cope with this problem, we have been developing ERESS (Emergency Rescue Evacuation Support System). This system is based on Mobile Ad-hoc NET works (MANETs). Mobile terminals with this system exchange the information that associate with mobility sensors among them. ERESS is updated continually via real time processing. Even when they detect a disaster, people search an appropriate evacuation route in real time. We are developing important portion of ERESS say Pre-ERESS, for automatic disaster detection in real time. The objective of this paper is to develop a new effective algorithm which detects people's exact extraordinary condition using Skin Potential Level (SPL). It will also be able to detect disasters from disaster experiments.

Many people have faced mortal risks due to sudden disasters such as fires, earthquakes, and terrorisms all over the world. To solve this kind of problems, we are developing ERESS (Emergency Rescue Evacuation Support System). This system consists of only mobile terminals with various sensors. In ERESS, these sensor data are exchanged and analyzed using only ad-hoc communication among nearby mobile terminals. ERESS aims to reduce the number of victims by supporting real-time evacuation in the critical situation for less than 30 seconds immediately after disaster outbreaks. The conventional ERESS recognized the disaster outbreaks by behavior analysis of terminal holders from sensor data using SVM (Support Vector Machine). However, there was a problem that it is difficult to obtain high reliability of judging disaster outbreak. In this paper, we propose a new method by buffering judgment results of SVM. We carry out experiments on the emergency evacuation with more than 200 examinees. We investigate the judgment accuracy of the proposed method and the time required for recognition of disaster outbreak.

Previously, the authors have proposed the Emergency Evacuation Support System (ERESS) for reducing disaster damage. The ERESS runs under Mobile Ad-hoc Networks (MANET) and primarily aims to reduce the number of victims in panic-type disasters. This system uses ERESS Mobile Terminals (EMT) which are mobile terminals assuming smartphones and tablets. EMT is provided with an advanced disaster detection algorithm and acquires sensor information such as acceleration, direction difference and walking steps. However, disaster detection of conventional ERESS is needed the information of all members existing on the same floor. In this paper, we propose a new disaster detection method using the positioning area information. Location information of the terminal holders are obtained by Radio Frequency Identification (RFID). In this method, we separate a number of areas in the floor and detect a disaster by the information of evacuees in the presence of each area. We show the effectiveness of the proposed method by panic-type experiments.

The RFID (Radio Frequency Identification) is considered as one of the most preferable ways for the position estimation in indoor environments, since GPS does not work in such situations. In RFID system, an RFID reader enables to estimate the position of RFID tags easily and inexpensively. In applications with the position estimation of RFID tags, indoor robot navigations are very important for human society. The problem is how to obtain the position estimations of RFID tags as accurately as possible.

In recent years, there are many collision accidents between vehicles due to human errors. As one of measures against the collision accidents, a radar system mounted on a vehicle has been attracting attention. By the radar mounted on a vehicle, it is possible to recognize the situation around the vehicle. The ranging with automotive infrared radar is very accurate, and able to understand the object existence in the observation around the vehicle. However, in order to grasp the situation around the vehicle, it is necessary to be aware of the attribute of the detected object. The information obtained by the automotive radar vehicle is only the direction and the distance of the object. Thus, the determination of the attribute of the detected object is very difficult. In this paper, we propose a vehicle recognition method by using reflectors. Through experiments, we show that the proposed method is effective for vehicle recognition.

Recently, the radio frequency identification (RFID) system is paid attention as an identification source that can realize a ubiquitous environment. One of the important technologies that apply the RFID system is the indoor position estimation of RFID tags. For example, it can be applied to an indoor navigation system for handicapped person and recognition of ambient environment by a mobile robot, etc. In this paper, we propose a new positional estimation method to estimate the RFID tag position by using the tune of the antenna directivity of the RFID reader (D-CRR). This method controls the directivity of the antenna by dynamically changing the distance between the antenna elements of the RFID reader. We show the effectiveness of the proposed method by computer simulations.

In this study, we focus on Pedestrian-Vehicular Collision Avoidance Support System (P-VCASS). P-VCASS is a system to support collision avoidance between vehicles and pedestrians. P-VCASS grasps the relative locations of vehicles and pedestrians by exchanging the GPS information with each other. P-VCASS warns drivers if it estimates the possibility of their collisions. The former P-VCASS is intended for adult pedestrians who are sensible to dangerous actions. In this paper, we propose a new activity estimation method of pupil/infant pedestrians who are not sensible to dangerous actions with coordination between intersections in P-VCASS. This method has two advantages. First, it is able to prevent the jumping out accidents of the pedestrians. Second, it is able to apply to the complex intersections by sharing a traffic situation between intersections. We show the validity of the proposed method by experiments using a vehicle which carries an in-vehicle apparatus in a intersection with roadway and sidewalk. As a results, we found that the recognition of a vehicle driver is possible before pedestrian jumps out to roadway in a complex intersections.

The objective of this paper is to developed a collision avoidance support system between pedestrians and vehicles in intersections. The authors have already developed VCASS (Vehicular Collision Avoidance Support System) [3], [4] and P-VCASS (Pedestrian-Vehicular Collision Avoidance Support System) which extends the functions of VCASS for pedestrians [6], [7]. This paper focuses on P-VCASS. There are two problems to develop P-VCASS. 1) It needs a long time for P-VCASS to be widely used in the society. 2) The GPS measurement error is not negligible in urban areas. Hence, P-VCASS lacks the reliability to prevent collisions between pedestrians and vehicles particularly in intersections. In this paper, we propose an effective back-up support system of P-VCASS. The approach is using laser scanners in intersections and can be broadly used in urban areas. The system is setting the infrastructure equipped with laser scanners and the communication facility around intersections. By using this system, it is able to judge correct pedestrian's position and situation by detecting pedestrians. If the system detects high possibility of collision, it will send a warning message to vehicles. We show the validity of the proposed system by experiments using a laser scanner.

IVC (Inter-Vehicular Communications) is a key technology to realize the next generation of ITS. The authors have developed Vehicular Collision Avoidance Support System (VCASS) based on IVC in order to prevent a vehicular accident beforehand. The system grasps the relative locations of vehicles by exchanging the GPS information with each other. The system warns drivers if it estimates the possibility of vehicular collisions. VCASS can drastically reduce the potential accidents of vehicular collisions. Advanced safety technologies such as VCASS will popularize in future. However, it is hard to expect that all vehicles in the world will have the VCASS system in short time. Thus, we have proposed S-VCASS (Substitution Vehicular Collision Avoidance Support System) for mobile terminal holders (MTH), and vehicles whose drivers have S-VCASS in their MT (Mobile Terminal) will be able to work like VCASS-equipped vehicles. In this paper, we propose effective algorithms for S-VCASS in the environment of mixed VCASS and non-VCASS vehicles. S-VCASS by MT has two problems. (1) S-VCASS by MT has no detecting function of possible vehicular collisions beforehand. (2) MT has small battery capacity. To solve these problems, we propose two effective algorithms for S-VCASS. The first is to add simple position estimation by LSM (Least Square Method) to MT for the collision detection. The second is a transmit control algorithm for the power saving. By these methods, MT with small battery capacity can do collision avoidance with other vehicles. We evaluate the performances of a position estimation by LSM and a transmit control algorithm. As a result, we show that the proposed algorithms are able to accurately warn a vehicle driver.

RFID (Radio Frequency Identification) systems have become meaningful as a new identification source that is applicable in ubiquitous environments. Each RFID tag has a unique ID, and is attached to an object. A user reads the unique ID of an RFID tag with RFID readers and obtains the information of the object. One of the most important technologies that use the RFID system is the position estimation of RFID tags. The position estimation means to estimates the location of the object with the RFID tag. It is very useful to acquire the location information of RFID tag. If a user understands the position of the RFID tag, a new navigation system for persons in complex buildings. In this paper, we propose a new method for accurate indoor position estimation of passive RFID systems named as the Sliding-Typed CRR method. In this method, the position of an RFID tag is estimated by using S-CRR (Swift Communication Range Recognition) method. The proposed method is capable of accurate position estimation in any directions of RFID tags.

In this paper, we propose network construction methods of sensor nodes for Border Security Systems. A Border Security System watches intruders by using sensor nodes with communication function. The detection of some intruders and the use of a long-term operation system are required in this system. In this paper, we propose two methods to reduce the power consumption of the whole network system by effective control of sensor nodes. By computer simulation, we show that the proposed network construction methods are suitable for Border Security Systems.

The RFID (Radio Frequency IDentification) system is paid attention to as a new identification source that achieves a ubiquitous environment. Each RFID tag has the unique ID, and is attached to some object. A user reads the unique ID of a RFID tag with RFID readers and obtains the information on the object. One of the most important technologies that use the RFID system is the position estimation of RFID tags. The position estimation means to estimates the location of the object with the RFID tag. It can be very useful to acquire the location information of RFID tag. If a user can understand the position of the RFID tag, the position estimation can be applied to a navigation system for walkers. In this paper, we propose a new method named as Swift Communication Range Recognition (S-CRR) method as an extended improvement of the previous CRR method on the estimation delay. In this method, the position of RFID tag is estimated by selecting the communication area model which corresponds to those boundary angles. We carry out the performance evaluation by the experiments of RFID system and show the effectiveness of S-CRR for position estimation.

RFID (Radio Frequency IDentification) systems have become meaningful as a new identification source that is applicable in ubiquitous environments. Each RFID tag has a unique ID, and is attached to some object. A user reads the unique ID of a RFID tag with RFID readers and obtains the information on the object.

Vast number of victims have damaged and died due to a lot of large-scale disasters (earthquake, fire, and terrorism, etc.) up to the present time. In disasters that most victims become panic, two matters are necessary to evacuate efficiently. The first is to estimate the location of the disaster occurrence. The second is to construct the evacuation support system that searches a safe and efficient evacuation route. In this paper, we propose Emergency Rescue Urgent Communication - Evacuation Support System (EUC-ESS) based on Mobile Ad-hoc NETworks (MANETs) composed of a lot of mobile terminals. By computer simulation, we show that this system would work to support the disaster victims regardless of situations (indoor, urban, basement, etc.)

In recent years, researchers have studied extensively about vehicle collision avoidance. The authors have developed Vehicular Collision Avoidance Support System (VCASS) based on Inter –Vehicle Communications (IVC) in order to prevent a vehicular collision beforehand. The system grasps the relative locations of vehicles by exchanging the GPS information in each vehicle. Then the system warns drivers if it detects a danger of collision. VCASS can drastically reduce the potential accidents of vehicular collisions. However, VCASS can not avoid collisions between vehicles and pedestrians, but avoid collisions just between vehicles. About 34% of fatal accidents by vehicles happen with pedestrians in Japan. So it is necessary to develop a new system for pedestrians. This paper deals with collision avoidance between pedestrians and vehicles. There are problems to develop such system. It is necessary to consider the mobility characteristics of pedestrians. In this paper, we propose a new collision judgment algorithm for Pedestrian-Vehicular Collision Avoidance Support System (P-VCASS) which extends VCASS. This algorithm considers the mobility of pedestrians. We show the validity of the proposed system by experiments using vehicles and pedestrian terminals.

In recent years, many researches and developments on ITS have been carried out to solve many problems in road traffic. IVC (Inter-Vehicular Communications) is the key technology to realize the next generation ITS. Vehicles install telecommunication equipments, and exchange safety information directly with each other.

The RFID (Radio Frequency IDentification) tag is expected to be used as a tool of localization. With the localization of RFID tags, a mobile robot with an installed RFID reader can recognize the surrounding environment. In addition, it can be applied to a navigation system for walkers. In this paper, we propose a new scheme named Communication Range Recognition (CRR) in order to localize RFID tags effectively. In this scheme, the RFID reader finds the edges of the communication range when its position is moved appropriately by the robot. We evaluate the performance of the estimated position error through numerous experiments. We show that our proposed scheme can reduce the moving distance of the RFID reader without degrading the accuracy of localization in comparison with the conventional schemes.

This paper focuses on the localization technology of passive RFID (Radio Frequency IDentification) tags. By this technology, we will be able to detect some target, to get information on it, and to find the position and the distance of it. This paper proposes a novel scheme named Communication Range Recognition (CRR) in order to localize RFID tags effectively. This scheme finds the edges of the communication range of the RFID reader antenna when its position is moving by the robot appropriately. We evaluate the performance of the estimated position error through numerous experiments. We show that our proposed scheme can reduce the moving distance of the RFID reader without degrading the accuracy of localization in comparison with the conventional schemes.

Optical Burst Switching (OBS) has been proposed to realize the next generation Internet on the Wavelength Division Multiplexing (WDM) network technology. Optical Burst Switching is an ultra high speed switching technology for optical fiber networks but has the data burst contention problem. In this paper, we introduce Virtual Path (VP) concept addressing burst contention resolutions in OBS networks. We propose two novel flow control schemes, named Static Inter Arrival Time Flow Control (S-IAT) and Dynamic Inter Arrival Time Flow Control (D-IAT). S-IAT keeps the data burst contention rat e in an acceptable level on OBS networks. Based on S-IAT, D-IAT achieves almost the same data burst contention rate and higher throughput than S-IAT by using the data burst loss rate threshold. We will show the availability of proposed schemes by computer simulations.

Recently, the RFID tag system is paid attention to as an identification source. Each RFID tag is attached to some object. With the unique ID of RFID tag, a user identifies the object provided with the RFID tag, and derives appropriate information about the object. One of the important applications of RFID technology is the position estimation of RFID tags. It can be very useful to acquire the location information concerning the RFID tags. It can be applied to navigation systems and positional detection systems for robots etc. In this paper, we propose a new position estimation method of RFID tags by using a probabilistic approach. In this method, mobile objects (person and robot, etc) with RFID readers estimate the positions of RFID tags with plural communication ranges. We show the effectiveness of the proposed method by computer simulations.

In recent years, researches and developments on ITS are carried out to solve many problems in road traffic. IVC (Inter-Vehicular Communications) is the key technology to realize the next generation ITS. Vehicles install telecommunication equipment, and exchange safety information directly with each other. The authors have developed Vehicular Collision Avoidance Suppor t System (VCASS) based on IVC in order to prevent a vehicular accident beforehand. The system grasps the relative locations of vehicles by exchanging the GPS information in each vehicle. The system warns drivers if there is a danger of collision. VCASS can drastically reduce the potential accidents of vehicular collisions. However, VCASS makes false warnings and unnecessary warnings due to the position estimation error of vehicles. In this paper we propose an extended collision judgment algorithm in order to solve these problems of VCASS. We evaluate the performances of conventional and proposed methods with real vehicles.

The objective of this paper is to exchange the position information between pedestrians and their nearby vehicles effectively, in order to protect the pedestrians from serious traffic accidents. We deal with direct communications between pedestrians and vehicles. We call this kind of communications as VPEC (vehicule-pedestrian communications). In this paper, we propose a cooperative reflect transmission scheme which is transmission control protocol using road infrastructure information. This scheme provides real-time communications between vehicles and pedestrian terminals, and enables to save both the transmission capacity and the power consumption of pedestrian terminals. We also show the validity of this scheme in VPEC by experiments with real vehicles.

The connected dominating set (CDS) has been extensively used for routing and broadcast in mobile ad hoc networks. While existing CDS protocols are successful in constructing CDS of competitive size with localized information, they either lack the mechanism to properly handle nodal mobility or require lengthy period of time to recover when CDS becomes corrupted. In this paper, a novel protocol, namely Multi-Initiator Connected Dominating Set protocol (MI-CDS), is proposed that constructs and maintains CDS of competitive size efficiently without introducing much communication overhead. The simulation results demonstrate that MI-CDS permits CDS to be available for the highest percentage of time in the mobile network scenario compared with the other CDS protocols.

Disastrous accidents (fires, earthquakes, chemical releases, terrorist attacks, indiscriminate gun-shootings, etc.) in local area (urban cities, residential buildings, department stores, etc.) usually result in tragic consequences for people and environments. Such accidents have clearly shown that the necessity for reliable systems supporting evacuation is quite urgent. Particularly choosing safety evacuation route is the most important for persons in affected area. In this paper we propose Emergency Urgent Communication -Evacuation Support (EUC-ES) system based on Mobile Ad-hoc NETworks (MANETs) among many mobile terminals. This system will works anywhere regardless of situations (indoor, urban, basement, etc.) as far as mobile terminals grasp their own positions. From the computer simulation results, it is shown that EUC-ES can evacuate affected persons in safety from the fire which occurred accidentally by using an algorithm to search for evacuation routes.

The RFID (radio frequency identification) tag is expected as a tool of localization. By the localization of RFID tags, a mobile robot which installs in RFID readers can recognize surrounding environments. In addition, it can be applied to a navigation system for walkers. In this paper, we propose an adaptive likelihood distribution scheme for the localization of RFID tags. This method adjusts the likelihood distribution depending on the signal intensity from RFID tags. We carry out the performance evaluation of estimated position error by both computer simulations and implemental experiments.

Recently, we need high bit rate transmissions of the wireless LAN to access the internet at offices and houses. Multi-Poll access scheme has been proposed as an efficient access control scheme for these necessities. The scheme is a central control scheme using Polling system. In order to establish a high speed multimedia transmission, we need to integrate the required quality of services effectively. In this paper, we propose QoS (Quality of Service) guaranteed Multi-Poll access scheme for multimedia services in wireless LAN. We evaluate the transmission performances of the proposed scheme for effectiveness by computer simulations. We have clarified that the proposed scheme has the outstanding performances on the throughput, delay time, and frame drop rate comparing to the conventional scheme.

Today, ITS (intelligent transport systems) is paid attention by people all over the world. ITS is the system that solves the road traffic problems by using communications technology of vehicles. IVC ( inter vehicle communications ) is the communications technology that vehicles exchange the information by using wireless LAN without any base stations. VANET ( vehicular ad-hoc network ) have been expected to provide new applications for passengers of vehicles, by enabling vehicles to communicate with each other via IVC as well as with roadside base stations via RVC ( roadside-to-vehicle communications ). We propose the COC ( contents oriented communications ) system on VANET via IVC. With COC, each vehicle collects original information that each vehicle has by communicating each other, and creates contents which may be useful for drivers, by analyzing original information. COC deliver the analyzed contents to other vehicles. The simulation results show that COC provide timely information of vehicular accidents and congestion to drivers.

In recent years, researches and developments on ITS are carried out to solve many problems in road traffic. IVC (inter-vehicular communications) is the key technology to realize the next generation ITS (Tokuda et al., 2002 and Morioka et al., 2000). Vehicles install telecommunication equipments, and exchange information directly with each other. The authors have developed vehicular collision avoidance support system (VCASS) based on IVC in order to prevent a vehicular accident beforehand. The system grasps the relative location of vehicles by exchanging the GPS information in each vehicle. Then the system warns drivers if there is a danger of collision. In this paper we propose two schemes in order to improve the accuracy of VCASS. We evaluate the performance of conventional collision judgment algorithm and the proposal scheme for VCASS. We have verified the effectiveness of the new VCASS in typical road environments.

Optical Burst Switching (OBS) has been proposed to realize the next generation Internet on the Wavelength Division Multiplexing (WDM) network technology. In OBS, the burst contention is the major problem. The deflection routing has been designed for resolving this problem. However the deflection routing cannot prevent the burst contention as the network load becomes high. In this paper, we show that a flow-rate control is essential for OBS. We propose Leaky Bucket Deflection method (LB Deflection method). In LB Deflection method, edge nodes which generate data bursts carry out a flow-rate control based on Leaky Bucket method. In order to verify the effectiveness of a flow-rate control in OBS, we show that LB Deflection method improves the network utilization and reduces the burst loss probability through computer simulation

Optical burst switching (OBS) has been proposed for an effective optical switching technology of WDM networks in broadband Internets. OBS has the advantages, i.e. 1) the high usage rate of the bandwidth and 2) no necessity of optical buffer. However, OBS has the burst-contention problem in control packet phase, and faces to the reduction of the network performance. Recently, slotted OBS has been proposed. The basic performance of slotted OBS is superior to the original OBS. However, slotted OBS itself cannot overcome the burst-contention problem, either. In this paper, we will adapt BECN/CRN typed deflection routing to slotted OBS to obtain the large improvement of the optical network performance. We also present two new schemes for slotted OBS to improve the burst contention problem, i.e. a) enforced waiting control and b) scheduling.

An optical burst switching (OBS) network provides preferable broadband infrastructure, and is a promising strong candidate for the future optical Internet. However, there is a major deficiency of the OBS, which occurs when multiple bursts contend for the same link and leads to bursts loss. As an effective method to resolve the above important issue of OBS networks, deflection routing has been proposed. A simple deflection routing without proper routing control cannot sufficiently distribute the traffic of bursts and guarantee ideal performance of OBS particularly for heavy traffic condition. In this paper, we propose a new approach for deflection routing in order to reduce the burst loss and minimize end-to-end delay. The simulation results show that the proposed scheme improves the network utilization and minimize both the burst loss probability and end-to-end delay

In the conventional WWW search or P2P file sharing systems, users search for some information by using the explicit information such as keywords, addresses or content names. However, it is very difficult to obtain real-time information immediately just after serious accident (i.e. fires, earthquake, explosion by terrorism, traffic accidents and so on) happens suddenly. The conventional information systems, whether it is centralized nor distributed, cannot support user accesses, since they cannot provide any contents with the Explicit Information, in such short time. In this paper, we propose a new communication scheme named COC - content oriented communications. In COC, distributed information systems don't observe the explicit information (keywords, addresses, content names, etc.) but the implicit information (locations, time, speed, etc.). This is why we call our system content oriented. In this paper, we introduce COC, which enables us to decrease the personal damage of a disaster in a local area where the disaster occurs by searching and getting some information for the evacuation.

In order to achieve a safe automotive society, it is necessary to develop an on-board intelligent system with inter-vehicle communications (IVC). We want to avoid vehicle collisions under most situations, such as intersections, highways, and blind corners, by using IVC technology through wireless ad hoc networks. The paper describes a vehicular collision avoidance support system (VCASS), and shows its performance by various experiments with two real vehicles. We have installed personal computers, telecommunication equipment, and GPS in the vehicles. A vehicle exchanges location information and velocity vectors with the other by a UDP broadcast, and calculates the relative position/speed. Vehicles warn the drivers of the possibility of collision. We verify the validity and effectiveness of VCASS by experiments.

Inter-vehicle communications (IVC) is one of the most important technologies for realizing advanced intelligent transport systems (ITS). We deal with Vehicle-PEdestrian Communications (VPEC) as communication between vehicles and pedestrians. The objective of VPEC is to protect pedestrians from traffic accidents. In VPEC without any controls, pedestrians (p-nodes) transmit many packets to vehicles (v-nodes) to provide the position information of p-nodes. But, the battery capacity of p-nodes is small. It is necessary to suppress the transmission of p-nodes to obtain proper information exchanges. We present effective reflect-transmission schemes which can reduce needless transmissions from p-nodes on VPEC. In addition, we present silent control protocol, mask control protocol and distance-based priority control protocol as more effective protocols for the reflect-transmission scheme. The proposed protocols can operate the reflect-transmission scheme more efficiently. Further, we have carried out a VPEC experiment to verify the control behavior of VPEC. We outline the experiments and show some results obtained.

The anycast communication protocol is to select the best server and the best route for a particular client from a group of replicated servers with the same contents. As users have come to demand contents with high QoS, the necessity to support the anycast communications in QoS networks has grown. In this paper, we propose a server and route selection method with application-level QoS-based anycast protocol. The protocol we propose has the following advantages: 1) the latest server and route information can be constantly acquired through distributed resource management by E-BB; 2) the server and route selection algorithm enable us to consider both the server load and network load simultaneously; and 3) high reliability can be guaranteed by decentralized control.

In recent years, WDM networks have received much attention as the Internet backbone networks because of the explosive growth of the Internet IP-based traffic. The optical burst switching (OBS) has been proposed as an effective optical switching technology in the WDM networks (C. Qiao and M. Yoo, 1999). OBS has the advantages in 1) the high usage rate of the bandwidth, and 2) no necessity of optical buffer. However OBS has the burst-contention problem in the networks. The deflection routing is proposed as one of means to solve this problem. In this paper, we propose a new routing method of using deflection routing. In addition, we propose a QoS/CoS control method using a new routing algorithm. Finally, we show the variety of the proposed methods by computer simulations.

Bluetooth utilizes fast frequency hopping to mitigate interference from other wireless devices and other Bluetooth piconets that share the same frequency range. However, it still can not avoid the interference between piconets entirely. In our simulation, we observed that the inter-piconet interference can significantly degrade the system throughput by more than 30%. The system throughput within a piconet can be improved by a proper arrangement of the segmentation/reassembling (SAR) policy and a good selection of MAC scheduling protocols. Many SAR policies and MAC scheduling protocols were proposed, but none of them takes the inter-piconet interference into consideration. In this paper, we study the impact of the interference on the performance of TCP traffic over a Bluetooth scatternet with multiple overlapping piconets. To alleviate the impact, we propose interference-aware SAR policies as well as the interference-aware MAC scheduling protocols. The simulation results show that our schemes help reduce the impact of the inter-piconet interference by more than 50%.

This paper deals with an effective method to share various kinds of vehicular information among a great number of vehicles for advanced inter-vehicle communications (IVC). We present a simple and effective communication scheme named two-way approached information spreading system (TWAIS) in order to provide high quality communications service in ITS. It makes smooth communications and high availability suitable for IVC.

The inter-vehicle communications (IVC) is one of the most important technologies to realize advanced intelligent transport systems (ITS). Conventional IVC is vehicle-to-vehicle communication through line of sight communication by millimeter wave in a narrow area. Here, we deal with more progressive IVC in a wide area. In this paper, we propose Dynamic Integrated Transmission Control (DITRAC) for IVC. DITRAC optimizes transmission power and transmission interval of vehicles according to the fluctuation of the communications circumstance of the ad-hoc vehicular communications network. In order to estimate the fluctuation of the neighboring communications, we present an effective and simple method, the road-weight with receiving history (WH) method. The simulations are conducted to show the validity of DITRAC for IVC.

In distributed network systems, one of the most important problems is how to assign the files to servers in view of cost and delay. It is obvious that there is a trade-off relationship between costs and delays in these systems. In order to evaluate the optimal file allocation such that the total cost is minimized subject to the total delay, we have presented a system model that can cover a wide range of multimedia network applications like VoD (video on demand), corporation information networks, and so on. We have solved the optimization problem as 0-1 integer programming, have found the optimal file allocation, and have investigated the general characteristics in distributed systems. In this model, we have introduced many cost and delay parameters to evaluate the total cost and delay in the system more exactly. In constructing practical systems, it is necessary to investigate the weight and the contribution of each parameter to the total cost. It is very useful to show how to estimate cost and delay parameters on the basis of this analysis. In this paper, we analyze the sensitivity of these parameters and make clear the influence between principal parameters.

A control scheme to significantly reduce the packet collision in multiple-access networks with random-access protocols is proposed. The scheme intensively enforces the capture effect by controlling packet transmission power increasingly as time. As a result of this power control, if the first packet in collision arrives earlier than the others by a certain amount of time, the difference in power necessary for the capture effect is retained during the whole colliding period, and the first packet can capture the channel. The essential point of the scheme is that the difference in the packets' arrival times causes the difference in power between packets. The scheme is thus named the power control during transmission (PCT) scheme. >

The authors present a new access scheme for packet radio networks with variable length packets, called S-ALOHA/IT (slotted ALOHA with immediate transmission) in which a packet can be sent immediately unless it overrides the slot boundary. In the s-ALOHA/IT, the PCT (power control during transmission) method is added for improving efficiency. The basic idea of the PCT method is to control the packet transmission power increasingly as a time function and to lead the capture effect. By the PCT method, some packets are successfully transmitted even when packet collisions occur. In addition, the initial power is also varied to introduce the capture effect among collided packet. A performance comparison of the s-ALOHA/IT is carried out with the conventional s-ALOHA by using computer simulation. In all cases, the throughput of s-ALOHA/IT is about twice that of the conventional s-ALOHA. >

Presents a new access control scheme for the wireless communication packet networks of variable packet length environment, s-ALOHA/PAIT (slotted ALOHA with power assigning and immediate transmission controls). The scheme improves channel throughput in two aspects, capture effect and reuse of vacant period of a slot. For reuse of vacant period of a slot, a packet can be transmitted immediately unless it overrides the slot boundary even though the timing is not at the beginning of the slot. It enables more than one packet to be transmitted successfully in a slot. Transmission power is varied to lead capture effect among packets transmitted at the beginning of a slot and also between a packet at the beginning of a slot and one transmitted in the middle of the same slot. The authors evaluate the performance of s-ALOHA/PAIT compared with the conventional s-ALOHA and show that s-ALOHA/PAIT obtains considerable improvement of the throughput performance. >

In the ATM network, various kinds of traffic will be supported. This includes traffic which requires high quality of service. For example, coded HDTV requires no cell loss because of high compression and no possibility of retransmission. CBR (constant bit rate) services require no delay jitter. Thus, it will be required to support some class of services with no cell loss and no delay jitter. This paper proposes a new transmission method Q-STM, with which no cell loss and no delay jitter can be supported in the ATM network. The Q-STM introduces two new concepts into the ATM networks; frame structure and time slot reservation. A frame structure itself is similar to the framed ATM. However, in the Q-STM, a frame is divided into some subframes and each subframe is a unit of time switching in intermediate switching nodes. This leads to smaller end-to-end delay than that of the framed ATM. Time slots in a frame are reserved for each Q-STM call in a call setup phase and this leads to no delay jitter and no cell loss. Ordinary ATM service class is also supported and this kind of cell uses an empty slot which is not reserved or is not used because of fluctuation of Q-STM call transmission rate.