Ken-ichi Baba

Proposal of an Initial Route Establishment Method in Wireless Mesh Networks

Hybrid wireless mesh protocol (HWMP) is consists of on demand routing protocol RM-AODV and pro-active routing based on tree-base routing. When a mesh portal exists as a gateway of a wireless mesh network, tree-based routing is very efficient in fixed mesh deployments. However, with the distance vector routing method, all mesh points need route metrics based on the network topology and many packets are consumed to build the topology. To solve these problems, we define a new address space based on the link state and propose an initial route establishment method with greedy forwarding by using addresses as positional information. From simulations results, we confirmed that the proposed routing method can build the routing topology before the entire wireless mesh network is constructed and reduce the number of control packets for routing, and it also has scalability.

QoS control method to reduce resource reservation failure in datagrid applications

Large scale grid computing uses a broadband link for high performance computing. However, since this approach is extremely costly, it would be more ideal to use a network that is inexpensive and that at the same time guarantees good computation quality. While the scheduler of grid can reserve many computing resources to achieve this goal, the prevention of resource reservation failure remains to be an issue at hand. We examined the dynamic bandwidth adjustment method used in DataGrid application. Guaranteeing the quality of each data transmission, this method operates by reserving bandwidth for each data flow using the Diffserv AF service and adjusting reserved bandwidth periodically. Three methods, the EF based method, the AF based method and the proposed method, were simulated for performance comparison and evaluation. The results show that the proposed method had the same, if not better, performance.

GMPLS Control Plane With Distributed Multipath RMSA for Elastic Optical Networks

Elastic optical networking (EON) has the constraint that all flows must have contiguous allocated frequency slots across all fiber links end-to-end, hence, the routing, modulation and spectrum assignment (RMSA) is one of the most important considerations in EON. This paper proposes and demonstrates a design of a generalized multiprotocol label switching (GMPLS) control plane for EON with distributed RMSA. The proposed approach uses an extended RSVP-TE to find multipath by broadcasting PATH message, using tentative reservation to avoid setting up multipath for one request. The proposed method also overcomes challenges faced by the previously pursued GMPLS-EON methods which relied on dynamic OSPF-TE where control plane overhead and the collision among lightpath requests caused by signaling latency. Simulation results based on the proposed GMPLS-EON method on different network scenarios reveal that our proposed design reduces the blocking probability by 4.56 and 3.86 when compared with the conventional GMPLS and GMPLS/PCE approaches, respectively, in the NSF topology at the network offered load of 60 Erlang. It also reduces signaling time by a factor of 1.84 compared with conventional GMPLS/PCE approach in the same network condition.

Fully-distributed control plane for elastic optical network with GMPLS with RMSA

This paper proposes a fully-distributed GMPLS framework through the use of extended RSVP-TE both for signaling and for routing, modulation and spectrum assignment (RMSA). Our proposed solution achieves lower blocking probability and shorter signaling-latency than does the state-of-the-art GMPLS/PCE architecture.

Performance Evaluation of Advanced High-Speed Data Transfer Methods in Long-Distance Broadband Networks

Remote backup and some grid applications transfer large amounts of data over long distance networks. The throughput of TCP Reno and NewReno over LFNs (large fat pipe networks) is much smaller than application requirements. High speed protocols are being developed to overcome this problem. However, the fairness of these high speed protocols with conventional TCP (Reno or NewReno) is not sufficient in LFN. Some TCP based high speed protocols (e.g., TCP Westwood and BIC TCP) estimate available bandwidth to improve fairness. These protocols estimate available bandwidth on the sender side by using Ack packets, while UDT (UDP based data transfer protocol) is a high speed protocol that estimates available bandwidth on the receiver side by using packet pair algorithms. Estimating available bandwidth on the receiver side should be more accurate than estimating it with Acks. However, the fairness of UDT with conventional TCP and UDT itself over an LFN is not good enough. The UDT protocol estimates a much greater value than the actual available bandwidth when a network is congested. The UDT detects congestion too late in LFN environments. We propose gUDT (gentle UDT) and ERED to improve fairness over that currently provided in LFNs.

Exact mean packet delay for delayed report messages multipoint control protocol in EPON

The infrastructure to develop the next generation optical access network is the Ethernet passive optical network (EPON). Interleaved polling with adaptive cycle time (IPACT) is a common polling method of an EPON. However, the mean waiting time of packets (= the mean packet delay) with IPACT is large depending on the arriving time of the packets. In this paper, a novel media access method for IPACT is proposed in order to minimize the mean packet delay. The mean packet delay with the proposed method is also derived as the exact solution. This solution is based on the non-trivial simplification of the previous work on the analytical solution for general IPACT. We confirm a close match between simulation and our theoretical results and show the effectiveness of our method.

Why are so many lines still reserved for emergency telephone calls in emergency situations

We propose a threshold relaxation and holding time limitation for general telephone calls under trunk reservation control in emergency situations. This TR-HTL method aims to accept more general calls while required emergency calls are still accepted. Computer simulation with a queueing system model of a telephone exchange showed that the threshold relaxation increased the number of accepted general calls while still enabling the required number of emergency calls to be accepted. Comparison between two strategies to set the holding time limit of general calls showed that the value of the limit and the call-blocking rate are in a strong trade-off relationship when the limit is short. An investigation of the relationships between the threshold relaxation rate and the call-blocking rate showed that reserving just 5% of the estimated traffic intensity of emergency calls enabled the required number of emergency calls to be accepted, increasing the number of accepted general calls. Moreover, we showed that much fewer reserved lines are needed for guaranteeing emergency calls.

Exact Mean Packet Delay Analysis for Long-Reach Passive Optical Networks

The long reach passive optical network (LR-PON) is a promising scheme for access networks that cover large areas. For designing an access network, an exact solution of the network performance (e.g., mean packet delay) is useful. Since long propagation delay causes unused time slots (idle time), and its effect on performance degradation is difficult to analyze, existing analysis of the LR-PON is done only for the no-idle time situation with modified optical line terminal (OLT) and each optical network unit (ONU). In this paper, we propose an exact solution of the mean packet delay for LR-PON with idle time. Our analytical solution is derived by a non-trivial extension of the existing work for the short range PON. We confirm a good match between the mean packet delay derived by the simulation and our analytical solution.

Threshold configuration of emergency trunk reservation considering traffic intensity for accepting more general telephone calls

We propose a threshold configuration and holding time limitation for general telephone calls under trunk reservation control in emergency situations. Our proposed method aims to accept more general calls while required emergency calls are still accepted. With our method, the threshold is configured in consideration of the ratio of traffic intensities which are estimated in advance. Computer simulation with a queueing system model of a telephone exchange showed that the general call-blocking rate was much lower than that without threshold relaxation or trunk reservation, while the emergency call-blocking rate was reduced to almost zero unless the sum of estimated traffic intensity was nearly equal to the number of lines. Moreover, we confirmed that the threshold was appropriately configured by using the proposed method, from the comparison between the result of the proposed method and that obtained by using the fixed value of a threshold.

Computational oral and speech science on e-science infrastructures

We demonstrate an oral scientific simulation and its visualization based on E-science. This oral scientific application will become an essential key component for medical and dental clinic in the near future because Bio-Medical simulations will provide a clinical index considering a prognostic of a disease. In this case, it was shown that the physical theory of sound production of speech sound, sibilant. However, it is difficult to acquire the computational and storage resources in the hospitals. Our E-science infrastructure enables scientists and clinicians to achieve the advanced information produced by simulations. As the result of this phase implementation for Bio-Medical simulation on E-science infrastructure, we could extract the scientific findings about the oral science. Moreover, this infrastructure can be used more generally because of the divided architecture between applications and E-science infrastructure.