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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.

This paper proposes a prioritized resolvable-contention-ring scheme for high-speed optical communication networks and investigates its performance. The priority mechanism is based on the time-token control scheme. This mechanism attempts to guarantee the frame delay of time-critical traffic by controlling the frame transmission of noncritical traffic. The noncritical frame can be transmitted only if token rotation time is faster than target rotation time. This paper examines the priority mechanism in the case of two priority levels and also in the case of four priority levels. System performance is studied using a computer simulation method with a time-continuous simulator. The validity of the priority mechanism is demonstrated in a comparison with a fiber distributed data interface (FDDI) and the nonprioritized resolvable-contention ring. Efficient operation of the priority mechanism is investigated by considering the buffer overflow rate of each priority class. The proposed scheme performs effectively. Moreover, the performance of FDDI is comparatively degraded because of long token waiting time and large token capture time.

This paper discusses the channel assignment problem in the multichannel, high-speed packet network. It is assumed that multiple channels exist between a pair of switches in the network. It is expected that by regarding those channels as a single channel group and executing the packet transmission, a more efficient high-speed and large-capacity transmission will be realized. This paper newly introduces, in contrast to the virtual circuit in the multichannel network, the concept of a channel group-virtual circuit (CG-VC) for the multichannel network, where the packets are assigned to the channels based on the concept of the overflow traffic. To realize the CG-VC system in the high-speed environment, a simple and practical switch structure is proposed. The switch uses optical fibering as the basic module and the system is constructed by superposing the basic modules. Each packet automatically selects an appropriate channel from the set of output channels belonging to the same channel group. It is shown as a result of performance evaluation that, compared to the conventional VC packet switching system, the proposed system greatly improves the transmission delay and utilizes efficiently the channel.

This paper proposes two new access protocols, wherein the power control during transmission (PCX) scheme attempts improvement of the throughput by capture effect; this scheme is applied to s-ALOHA. Either method solves the problem of contradiction between the packet transmission time difference required in PCT scheme and the synchronized transmission as the basic requirement in PCT scheme and the synchronized transmission as the basic requirement in s-ALOHA. The first protocol is the s-ALOHA with capture interval (s-ALOHA/CI), which is concerned with the fixed-length packet format. A capture interval is provided in the first part of the slot, wherein the transmission time is selected at random to provide the transmission time difference. The second protocol is s-ALOHA with tail synchronization (s-ALOHA/TS), which is concerned with the variable-length packet format. Utilizing the variable-length property, the tail of the packet is synchronized to the tail of the slot and the packet is transmitted. Then the packet length difference produces the transmission time difference. It is verified through evaluation by analysis and simulation that the throughput performance of traditional s-ALOHA is greatly improved in either protocol by the capture effect. Especially, in contrast to the deterioration of the effective throughput of the traditional s-ALOHA due to the slot loss, it is verified that the performance of s-ALOHA/TS is better than that of the fixed-length packet scheme. These high-performance protocols will serve as a powerful means of realizing the effective operation of VSAT network, etc., with the synchronization function.

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.

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. >

Leaking glaucoma filtering blebs with scleral perforation were successfully repaired in two patients using amniotic membrane transplantation. The amniotic membrane was placed into the subconjunctival space to cover the perforated scleral area. The edge of the limbal conjunctiva was sutured to the peripheral cornea with conjunctival advancement over the amniotic membrane. The bleb leaks were successfully closed. In addition, good and functioning filtration was maintained during a follow-up period of 12 months in both cases. Amniotic membrane transplantation may be effective for the surgical management of high risk of leaking glaucoma blebs with scleral perforation.

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.

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 generally used for routing and broadcasting in mobile ad hoc networks (MANETs). To reduce the cost of routing table maintenance, it is preferred that the size of CDS to be as small as possible. A number of protocols have been proposed to construct CDS with competitive size, however only few are capable of maintaining CDS under topology changes. In this research, we propose a novel extended mobility handling algorithm which will not only shorten the recovery time of CDS mobility handling but also keep a competitive size of CDS. Our simulation results validate that the algorithm successfully achieves its design goals. In addition, we will introduce an analytical model for the convergence time and the number of messages required by the CDS construction.

The advent of VSAT (very small aperture terminal) has made it possible to consider a new utilization of satellite communication. This paper proposes a new access protocol v-ALOHA, which is matched to the characteristics of the packet switching network based on VSAT. p-ALOHA is used as a means to cope with the requirement for simplification. To complement its disadvantage of low through-put, a new control scheme is combined based on the new utilization. The performance is improved by the capture effect. The basic idea of the control scheme is to vary the power with time while transmitting packets. The difference in the transmission-start time is converted into the power difference and produces the capture effect, thereby improving the performance. Thus, an access protocol is realized which improves the low throughput of p-ALOHA while preserving its simplicity. This paper describes the basic idea of this v-ALOHA and the protocol structure, indicating qualitatively its features. Then the throughput performance is formulated through a quantitative analysis. It is shown from the numerical results for the fixed-length packet that the performance of the proposed scheme is better than other capture schemes, approaching sufficiently the performance of s-ALOHA. For the case of the variable-length packet, there is no slot loss as in s-ALOHA, and the proposed scheme is shown, using an example, to be better sometimes than s-ALOHA.

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.

A surface profiler system with a high accuracy of the order of nanometers has been developed for a half-meter-long X-ray mirror. This system is based on microstitching interferometer (MSI) and relative angle determinable stitching interferometer (RADSI). Using elastic hinges and linear actuators, we designed the 5-axis- and 6-axis stages for the MSI and RADSI, respectively, for the half-meter-long X-ray mirror. A test mirror of length 0.5 m was used to measure the height accuracy (1.4 nm in rms) and lateral resolution (36 μm) of the proposed system.

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.

The L-rhamnose isomerase gene (L-rhi) encoding for L-rhamnose isomerase (L-RhI) from Bacillus pallidus Y25, a facultative thermophilic bacterium, was cloned and overexpressed in Escherichia coli with a cooperation of the 6xHis sequence at a C-terminal of the protein. The open reading frame of L-rhi consisted of 1,236 nucleotides encoding 412 amino acid residues with a calculated molecular mass of 47,636 Da, showing a good agreement with the native enzyme. Mass-produced L-RhI was achieved in a large quantity (470 mg/l broth) as a soluble protein. The recombinant enzyme was purified to homogeneity by a single step purification using a Ni-NTA affinity column chromatography. The purified recombinant L-RhI exhibited maximum activity at 65 degrees C (pH 7.0) under assay conditions, while 90% of the initial enzyme activity could be retained after incubation at 60 degrees C for 60 min. The apparent affinity (K(m)) and catalytic efficiency (k(cat)/K(m)) for L-rhamnose (at 65 degrees C) were 4.89 mM and 8.36 x 10(5) M(-1) min(-1), respectively. The enzyme demonstrated relatively low levels of amino acid sequence similarity (42 and 12%), higher thermostability, and different substrate specificity to those of E. coli and Pseudomonas stutzeri, respectively. The enzyme has a good catalyzing activity at 50 degrees C, for D: -allose, L-mannose, D-ribulose, and L-talose from D-psicose, L-fructose, D-ribose and L-tagatose with a conversion yield of 35, 25, 16 and 10%, respectively, without a contamination of by-products. These findings indicated that the recombinant L-RhI from B. pallidus is appropriate for use as a new source of rare sugar producing enzyme on a mass scale production.

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.

OBJETIVO: o presente trabalho de pesquisa analisou os efeitos da tração reversa da maxila associada à anquilose intencional dos caninos decíduos superiores, mediante o emprego da cefalometria. METODOLOGIA: o protocolo de tratamento incluiu: 1) anquilose intencional dos caninos decíduos superiores; 2) expansão rápida da maxila e 3) tração reversa da maxila, imediatamente após o término da fase ativa da expansão. A amostra foi composta de 18 crianças nos estágios de dentadura decídua e dentadura mista, com idade média inicial de 7 anos e 1 mês. O intervalo médio de tratamento com a tração reversa da maxila foi de 1 ano e 1 mês. As telerradiografias laterais foram obtidas na documentação inicial e após a correção da Classe III. RESULTADOS E CONCLUSÕES: os resultados demonstram que os ângulos representativos da convexidade facial, NAP e ANB, aumentaram de 0º para 6,6º e 3,5º, respectivamente. Isso significa dizer que a face transformou-se de reta ou côncava, peculiar na Classe III, para uma face convexa, característica de normalidade no estágio avaliado. Essa melhora na convexidade facial é atribuída ao avanço da maxila, registrado tanto na região alveolar (ângulo SNA e as distâncias Co-A e NPerp-A) como na região basal (ângulo SN.ENA). A maxila deslocou-se para frente, enquanto a redução do ângulo SNB de 80,56º para 79,61º demonstrou um retroposicionamento mandibular. Além da mudança no sentido sagital, houve rotação da mandíbula no sentido horário, com aumento dos ângulos SN.GoGn e SN.Gn. Somado aos efeitos ortopédicos, houve inclinação vestibular dos incisivos superiores. AIM: the current article analyses the effects of maxillary protraction associated to the intentional ankylosis of the deciduous canines on the basis of cephalometric measurements. METHODS: the treatment protocol included: 1) intentional ankylosis of the upper deciduous canines; 2) rapid palatal expansion and 3) maxillary protraction performed immediately after the end of the expansion. The sample was comprised of 18 patients equally divided according to gender, in the primary and mixed dentition. The mean treatment time with maxillary protraction was 1 year. The lateral radiographs were taken in the beginning of the treatment and after correction of the Class III malocclusion. RESULTS AND CONCLUSION: the results show that the facial convexity angles - NAP and ANB - increased from 0º to 6.6º and 3.5º, respectively. This means that the patients’ profile changed from straight or concave, which is typical in the Class III malocclusion, to convex, which is typical in normal occlusion. Such an improvement in the facial convexity is due to the maxillary advancement, evidenced both in the dentoalveolar (SNA angle and Nperp-A measurement) and in the basal areas (SN.ANS angle). The maxilla was anteriorly displaced while the reduction of the SNB angle from 80.56º to 79.61º demonstrated a mandibular retropositioning. Besides the sagittal alterations, the mandible presented a clockwise rotation, with increase in the SN.GoGn and SN.Gn angles. Dental compensation was also noticed, represented by the buccal inclination of the upper incisors.

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.

Eight distinct and potentially causative mutations were identified in eight unrelated Japanese patients with protein S (PS) deficiency, by direct DNA sequencing of the protein Salpha (PSalpha) gene-specific polymerase chain reaction products of all 15 exons and exon/intron boundaries. There were five missense mutations, including two novel mutations (Cys80Tyr and Arg314His), and three showed a major impact on the expected gene products: novel mutations of a 5-bp deletion (delCTCTG887:Cys206Stop) and a nonsense mutation (Glu208Stop), as well as a previously reported splice site (exon 10 +5 A--G) mutation. One of the patients showed compound heterozygosity for delCTCTG887 and 732A--G. Investigation for the cosegregation state of these two mutations with PS deficiency in the patient's family suggested that the delCTCTG887 mutation was responsible for the abnormal phenotype and that the 732A--G (Lys155Glu) mutation did not appear to play a key role. However, we also identified the same 732A--G (Lys155Glu) mutation in an unrelated patient with apparent PS deficiency with severe pulmonary embolism, and found that this mutation seemed to cosegregate with a PS-deficient state in her family members. These data implied that unknown factor(s) other than the 732A--G mutation itself might influence phenotypic expression of PS status in different individuals.

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. >

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 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.

We study allocation problems of multimedia files in distributed network systems. In these systems, the files are shared by users connected with different servers through high-speed communication networks. One of the most important problems in distributed systems is how to assign the files to servers in view of costs and delays. In these systems, it is obvious that there is a trading-off relationship between costs and delays. Our objective is to find the optimal file allocation such that the total cost is minimized subject to the total delay. In order to evaluate the optimization, we present a system model that can cover a wide range of multimedia network applications such as VoD (video on demand), corporation information networks, and so on. We introduce a 0-1 integer programming formulation for the optimization problem. We find the optimal file allocation by solving these formulae, and quantify the general tendency in distributed systems. Moreover, we make a comparison between the exhaustive search and the approximate method that we use for optimization.

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.

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.

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.