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.

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.

Nowadays, a lot of people die or are injured due to sudden disasters. In these disasters, it is important to discover them early and evacuate people quickly. To cope with these problems, we are developing ERESS (Emergency Rescue Evacuation Support System). Mobile terminals with this system exchange their information that associate with their sensors among them by MANET. When they detect a disaster occurring, they search an appropriate evacuation route in real time, and can reduce the number of victims. To realize this system, we need to analyze evacuees' behavior and establish a new judgment method of the disaster occurrence. Therefore, we are developing a system named Pre-ERESS, for collecting and analyzing the evacuees' behavior in emergency. We'll demonstrate this system.

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. Previously S-CRR (Swift Communication Range Recognition) has been proposed for the appropriate estimation method of this kind of applications. This method is capable of the accurate position estimation of an RFID tag in very short time. The disadvantage of S-CRR is that the mobile robot must stop to search RFID tags accurately at each position. In indoor robot navigations, mobile entities like robots have to move continuously because they need to navigate smoothly and safely. In this paper, we propose a new position estimation method of RFID tags with continuous moving only using RFID technology. We call this Continuous Moving CRR (CM-CRR). CM-CRR uses two communication ranges, long and short ranges and switches them appropriately. The system estimates the position of RFID tags using their approaches and continuous moving. To show the effectiveness of CM-CRR, we evaluate the estimation error of an RFID tag by computer simulations. From the results, CM-CRR can accurately estimate the position of RFID tags with continuously moving of the mobile robot and be applied to indoor robot navigations.

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.

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. One of the important technologies that use the RFID systems is the indoor position estimation of RFID readers. If a user can understand a position of an RFID reader, the position estimation can be applied to a navigation system for walkers. Using conventional methods, the system needs more than two RFID tags for the accurate indoor position estimation, and the accuracy itself of position estimation is not so high. In this paper, we propose a new method for accurate indoor position estimation of passive RFID systems. In this method, the position of an RFID reader is estimated using SCRR (Swift Communication Range Recognition) method. The proposed method is capable of accurate position estimation in near real time regardless for large numbers of RFID tags.

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.

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 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.

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.

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 (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 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.

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.

We present a novel access scheme called CDMA/CS-CF (code division multiple access/code sense for collision free access), which can transmit two kind of traffic i.e. voice and data efficiently. This scheme avoids the collision of packets that occur in CSMA (code sense multiple access), and can assign codes fairly to terminals. This assignment of codes to terminals is operated autonomously by terminals themselves. This scheme can improve the characteristics of throughput, access delay and packet loss rate. We evaluate the performances of CDMA/CS-CF compared with CDMA/PRMA, and show the validity, numerically. Moreover, we consider enhanced CDMA/CS-CF and show the effectiveness in the environment with hidden terminals.

A wireless adhoc network consists of mobile nodes that may move often. The mobility of nodes results in a change in routes, requiring some mechanism for determining new routes. A number of routing protocols have already been proposed for wireless Ad-hoc networks. In these conventional protocols, transmission power of each node is kept constant This paper proposes an approach to control transmission power to improve the performance of routing protocols. By controlling power, the proposed Power Control Routing (PCR) improves the network capacity and power consumption. Simulation experiments show that PCR has high network capacity and low power consumption.

This paper deals with inter-vehicle communications (IVC) for an advanced intelligent transport systems (ITS). The IVC makes it possible to exchange real-time information among vehicles. We focus on the packet-based IVC, where intelligent equipments in vehicles communicate with each other automatically in wireless channels to exchange their transportation information. The authors presented Vehicular Information BROadcasting Relay (VIBROR) protocol in order to realize the multi-hop transmission scheme for broadcasting information without any complex negotiation among vehicles. We deal with priority control and filtering control of relayed information as effective buffer management on the VIBROR protocol.

We present a novel access scheme called CDMA/CS-CF (code division multiple access/code sense for collision free access), which can transmit two kind of traffic i.e. voice and date efficiently. This scheme avoids the collision of packets that occur in CSMA (code sense multiple access), and can assign codes fairly to terminals. This assignment of codes to terminals is operated autonomously by terminals themselves. This scheme can improve the characteristics of throughput and access delay. We evaluate the performance of CDMA/CS-CF compared with CDMA/PRMA, and show the validity, numerically.

We consider the optimal mirror allocation problems for the purpose of load balance in network servers. We focus on constructing high-reliability networks, and propose the optimal mirror allocation model such that the system reliability is maximized subject to costs and delays, in view of the trading-off relationship between the reliability and cost. This optimization model is capable of dealing with various kinds of network topology. We formulate this optimization problem as a 0-1 integer programming in this model, and we can find the place where each mirror server should be and the concrete assignment of files to mirror servers. Our objective is to find the optimal mirror allocation by solving this model, and to show the general characteristics about the load balance and the improvement of the system reliability by the distributed mirror allocation, quantitatively.

Intelligent Transportation Systems (ITS) have become a focus for many countries. To achieve ITS, Inter Vehicle Communication (IVC) is required for the exchange and distribution of data such as congestion or emergency information. If this communication can be done without fixed infrastructure, the systems can be deployed quickly and on a larger scale. Ad hoc networking technologies are one such technology to achieve IVC. However, if generic ad hoc network solutions are applied directly to IVC, performance can degrade quickly as the system scales particularly for broadcast type messages. In this paper we propose two new broadcast protocols that reduce bandwidth required for broadcast communication by taking advantage of a vehicle's highly directional movement and Global Positioning Information. To show the performance of our new protocols, we compare our approach with generic ad hoc broadcasting techniques. Our results show that it is possible to achieve several hundred percent improvement of bandwidth utilization with very slight sacrifice of reachability.

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.

This paper proposes a new organizing method for packet radio networks: layered self-organizing method. In the layered self-organizing network, a whole service area is divided into multiple sub-service areas and one base station is settled in each sub-service area. Base stations are connected to the backbone network, a high-speed wired network. A base station covering area is tuned to be less than a sub-service area. Mobile stations that stay in the outside area of a base station covering area are connected with one of the near base stations through several repeating mobile stations in a self-organized fashion. So a layered self-organizing wireless network can cover a wide area with fewer base stations than the conventional cellular networks. This paper evaluates the network connectivity by computer simulation and shows the effectiveness of the method. Furthermore, the paper presents an additional power-control protocol to obtain almost complete connectivity in the whole network.

Optical switching networks to transport vast amounts of information are important for B-ISDN services. Wavelength division multiplexing (WDM) is emerging as the dominant technology for future optical networks. A large capacity photonic ATM switch architecture using WDM technology is proposed in this paper. The proposed switch is suitable for WDM optical ATM networks, that is, the input and an output of the switch are wavelength division multiplexed. The switch can provide very large ATM cell switching capacity, for instance, 10 Tbit/s, with reasonable complexity. The basic switch module of the proposed switch has a simple architecture, and reduces the amount of a buffer hardware by introducing the WDM concept.

Using the rate control to restrict the peak cell rate of traffic is addressed. The asynchronous transfer mode (ATM) environment is considered as a discrete-time environment in which one slot is equal to one cell transmission time. A rate control that can restrict the number of cells during any fixed-length time interval in a discrete-time environment is studied. The scheme is realized by means of simple counter accumulation per slot, and it is easy to synchronize with slots. The simplicity of this scheme may make possible the flexible restriction of the peak cell rate according to network conditions. The scheme is analyzed, using matrix analytic techniques, in order to investigate the smoothing effect of bursty traffic and the queue length required to satisfy a certain quality of cell loss probability. Numerical results show the effect of restricting the peak cell rate of bursty traffic and the tradeoff between the smoothing effect and the required queue length.>

A traffic control scheme for FDDI (fiber distributed data interface) interconnection through an ATM (asynchronous transfer mode) network is presented. The scheme consists of two parts, a VP (virtual path) bandwidth allocation algorithm and a feedback type buffer protection flow control. Both use the acknowledge for the frame of FDDI as a control unit. Simulation results show that VP bandwidth allocated by the scheme increases according to arrival traffic when the destination FDDI has enough capacity and allocated bandwidth is not increased when its capacity is less than arrival traffic. Thus, the scheme has desirable VP bandwidth allocation characteristics. Simulation results also show that the scheme prevents cell loss at a destination gateway completely.>

The authors propose two multicast routing algorithms which distribute copy operation of packets over all nodes along the multicast path: a link-added type algorithm and a loop-constructed type algorithm. Both algorithms, at first, derive an approximate solution for minimum cast path, and then improve the solution to prevent concentration of packet copy operation at one switching node at a little sacrifice of total cost along the path. Computer simulation results show that too much copy operation per node can be avoided by these algorithms. Compared to the minimum cost solution of the tree-shaped multicast path, the solution of the proposed algorithms makes the average distance connecting a source-destination pair longer, but the sacrifice of total cost is verb small. These algorithms can be applied not only to packet networks but also asynchronous transfer mode (ATM) networks.>

A novel packet switch architecture is proposed based on a channel grouped virtual circuit (CG-VC) scheme for high-speed communication networks. The case is considered in which there are several parallel channels between two switching nodes. The CG-VC scheme allows a packet to select an available channel in such a way as to avoid congested channels using a simple, hardware-based, self-routing mechanism. As a result, the architecture provides efficient channel use and low switching delay. The performance of the proposed switch is evaluated by simulation. The results show the proposed switch significantly improves channel utilization and switching delay compared with conventional single-channel allocation transmission policies.>

An asynchronous transfer mode (ATM) switch architecture that uses the broadcasting transmission medium for transmission of cells from input ports to output ports is introduced. Cell transmission and its control are separated completely, and cell transmission control, i.e. header operation, is executed before cell transmission (control ahead). With this operation, cell transmission and its control can be executed in a pipeline style, allowing high-speed cell exchange and making transmission control easier. One of the essential problems for ATM switches which use the broadcasting transmission medium is high-speed operation of the transmission medium. The switch fabric performance is analyzed according to its switching speed. Numerical results show that the ATM switch proposed shows good cell loss performance even when its switching speed is restricted, provided that switch utilization is below 1. Extensions to the switch that lead to robustness against bursty traffic are shown.>

The objectives of this study are: (1) to show numerically the performance advantages of the resolvable-contention-ring (ReC-ring) in comparison with typical ring control methods like IEEE 802.5 token-ring, ANSI FDDI I token-ring, slotted-ring and contention-ring, and (2) to consider the possibility of using the priority mechanism of the ReC-ring for multimedia high-speed communications networks. The authors present a simple priority control mechanism based on the time-token scheme for multimedia communications of ReC-rings. The performance of the prioritized and nonprioritized ReC-rings is compared by computer simulation, and the priority mechanism presented is proved to have sufficient validity for multimedia communications networks.>

The objective of this paper is to provide insight into the basic behavior of an integrated voice/data multiplex structure by using a two-dimensional Markov analysis. The model for analysis is restricted to the movable boundary case, where the unused capacity for voice traffic is dynamically reassigned to data traffic. Numerical analysis shows a quasicapacity-limit characteristic for the data delay performance. This paper denotes this characteristic as the multi-capacity-limits (MCL) property and investigates it from a number of viewpoints.