To address the rapid increase in communication traffic, optical backbone networks are focusing on technologies such as Elastic Optical Networks (EON) and Space Division Multiplexing (SDM), which enable higher-speed and higher-capacity transmission. Previous studies have proposed a frequency allocation method for a distributed-controlled SDM-EON using a 4-core Multi-Core Fiber (MCF). This method utilizes information on the usage status of multiple cores, where the impact of crosstalk (XT) is negligible. However, recent advancements in fiber technology have led to research on fibers with more cores. In the future, resource allocation methods will need to be considered that account for XT in environments with MCFs containing a greater number of cores. In this study, we propose a frequency allocation method that considers inter-core XT in a distributed-controlled SDM-EON composed of a 7-core MCF. Simulation results revealed that the capacity of accepted path requests varies depending on the core allocation algorithm. Furthermore, by employing a frequency allocation method that selects between First-Fit (FF) and Last-Fit (LF) on the basis of the XT tolerance of new optical paths, the call blocking probability was reduced compared to using only FF.

In optical core networks, Elastic Optical Networks (EON) are gaining attention for efficiently accommodating the continuously increasing communication traffic. Path establishment methods for applying a superposition coding technique to EONs have been proposed. However, they are limited to application during the accommodation of new requested paths. We propose a path establishment method for applying superposition coding not only during the accommodation of new requested paths but also between already accommodated optical paths by reallocating the optical paths. This is expected to increase the number of optical paths applying superposition coding, leading to a more efficient use of frequency resources. We conducted evaluations on combinations of optical paths where superposition coding is applied, the impact of changes in conditions for superposition coding, and impact of the time required for reallocation. The evaluation results indicate a 34.5% decrease in the path-call-blocking probability and a maximum of 25.8% decrease in frequency-slot fragmentation.

The frequency of VoIP calls on IP networks is increasing. The maximum number of VoIP sessions for a given quality of service guarantee does not necessarily match the number obtained by dividing the link bandwidth of the VoIP session because of the statistical multiplexing effect. For reducing the blocking probability of VoIP calls, we propose a VoIP admission control with a state probability. We determine the maximum number of VoIP calls by using the expected packet loss rate. We show the effectiveness of our method in a numerical analysis comparing it with the conventional method. The analysis shows that the maximum number of connections derived by our method is larger than that of the conventional method. Therefore, our method decreases the blocking probability.

Service chaining composed of several different virtual network functions (VNFs) constitutes a use case of Network Functions Virtualization (NFV). In a conventional method, the optimal allocation of VNFs and logical paths was resolved by using integer linear programming. However, because the approach did not consider that the required resources of each service differ, the residual resources of the links or physical machines were dispersed as the number of allocated services increased. Therefore, the method did not efficiently allocate resources to services requiring many resources. In this paper, in order to accommodate such services, we propose novel resource allocation methods that consider the residual link bandwidth. We evaluated the performance of the proposed methods through a simulation. The results show that our methods can allocate resources to services requiring many resources more efficiently than can conventional methods.

The distributed control in elastic optical networks proposed in our previous work can reduce call blocking probability and connection establishment time by booking a reservation path and a tentative (second candidate) reservation path at a time. However, there is a possibility of failure in establishing both the reservation path and the tentative reservation path because reservation paths are decided independently. Therefore, in this paper, we propose an advanced optical frequency spectrum allocation method which allocates different optical frequencies to the reservation path and the tentative reservation path as much as possible and allocates the spectrum considering link utilization. Through, simulations, we show that proposed method can reduce the failure rate of the tentative reservation path in NSF topology compared with the previous method.

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.

Optical circuit switching (OCS) technology is mostly used in all-optical network. Most OCS networks use WDM on fibers and one wavelength is assigned to one connection. However, OCS technology needs to pre-configure a lightpath before transmitting data, and the pre-configuring overhead takes more than round trip time between the source node and destination node. This pre-configuring overhead also exists when we set up optical CDM paths on a wavelength of a WDM network. Therefore, when the data size is small, the influence of the pre-configuring overhead becomes large relatively. In this paper, we propose a hybrid optical network architecture and a control method to reduce this influence. Our hybrid architecture includes a broadcast network in addition to an OCS network, an all traffic is transferred on the selected network according to the traffic characteristics. We evaluate the basic performance of the OCS network and the broadcast network and show that the broadcast network can transfer data more efficiently than the OCS network when the data size is small.

We generally utilize high-speed transport protocols to transfer and share large-scale data in long-distance broadband networks. However, the difference in performance between protocols when some kinds of protocols share the same link increases. Consequently, we propose a control method of discarding packets corresponding to protocol types that takes into consideration high-speed performance and fairness of flows. We evaluated the efficiency of our method in simulations. As a result, we found that it could allocate bandwidth equally while retaining high link utilization.

Grid technology has been studied and developed by numerous researchers in recent years. Data in conventional grid environments are changed by using TCP/IP. However, as long as the architecture is based on packet switching, highly efficient computing is difficult to achieve. We thus propose a new architecture, the λ computing environment, where network switches and computing nodes are connected to one another with optical fibers, thereby offering high-performance computing by establishing an optical wavelength path between shared memories on computing nodes. We established the lambda computing environment using the AWG-STAR system, and designed a data-sharing structure for the OpenMP library, which is a parallel-computing programming language utilizing shared memory. Moreover, we evaluated its performance against existing parallel computing in a PC-cluster environment by executing OpenMP applications.

Various multimedia streaming have started to be offered in Internet protocol (IP) networks. However, since current networks cannot operate well if the consumers' end system sends multimedia stream at will, an admission control is becoming an important part of IP networks. Therefore, we previously proposed an admission control scheme we call tentative accommodating and congestion confirming strategy (TACCS). The basic idea is to accommodate incoming flows tentatively and then confirm congestion after a certain period. In TACCS, the ingress nodes of a domain make flow-accommodating decisions based on information about packet-loss events. The information is assumed to be advertised from congestion detection agents (CDAs) located in the domain. If comparable performance could be achieved without adding CDA functions to core nodes, the cost of deploying would be reduced and its scalability would be improved. We have thus developed an enhanced called TACCS that achieves admission control based on cooperation of high functional edge nodes and does not depend on CDAs in the core network. Simulation showed that the performance of edge-based is comparable to that of conventional that depends on CDAs in the core network.

Internet protocol (IP) networks need admission control mechanism to provide full-fledged multimedia services. Therefore we previously proposed an admission control scheme called the "tentative accommodating and congestion confirming strategy (TACCS)". The basic idea of TACCS is to tentatively accommodate incoming flows and then, after a certain period, determine whether accommodating them has created congestion. In this scheme, the ingress nodes of a domain make flow- accommodation decisions based on packet-loss event information. The information is assumed to be advertised from congestion detection agents (CDAs) located in the domain. However, adding CDA functionality to core nodes is a barrier to deploy TACCS and limits its scalability. Thus, we furthermore developed an enhanced version called "edge-based TACCS" that performs admission control on the basis of only cooperation between edge nodes- it does not depend on CDAs in the core network. In this paper, we compared the operation of the edge-based version with that of the core-node-supported TACCS and investigated a problem: some flows, which should be rejected in the core- node-supported version, could be wrongly accommodated in the edge-based TACCS. Theoretical analysis of this "rejection failure" problem showed that it does not significantly degrade flow quality, meaning that edge-based TACCS is feasible.

In our previous studies, an optical-code-division multiplexing (OCDM)-based network architecture has been proposed to improve the wavelength utilization and to provide finer bandwidth granularities to users. However, since up-to-date all-optical regeneration technologies are still immature, signal quality degradation at intermediate nodes is considered as a crucial problem in transparent optical networks. Because the remaining noises may propagate, and be accumulated along the light-path, which eventually result in unacceptable signal quality. In this paper, we first define a cycle attack problem due to multi-access interference (MAI) propagation in transparent OCDM-based networks, which may cause severe service disruption. A depth-first-search (DFS)-based algorithm is proposed to diagnose such cycle attacks and a heuristic wavelength assignment called advanced first-fit (AFF) scheme taking cycle attacks into account is found to be a simple but effective approach mitigating the cycle attack impacts by computer simulations.

In this paper, an OCDM-based multi- granularity optical cross-connect (MG-OXC) is proposed to enable the optical path switching in bandwidth granularity finer than the wavelength-based path. Such an optical path switched by OCDM-based MG-OXC is called OCDM label-switched path (OCDM-LSP), which is capable of hybrid optical code (OC)/wavelength conversion along the path from a source to destination. With distinct OCs, OCDM-LSPs can share a single wavelength without any synchronization mechanism and be discriminated by ultra- fast optical correlation. The asynchronous ability and OC conversion distinguish the OCDM-LSP from Packet-LSP or TDM-LSP in resolving granularity problem in wavelength- based path. Based upon our proposal, all-optical optical path provisioning including F-LSP, WB-LSP, L-LSP and OCDM- LSP can be realized in the transport layer. Simulation is conducted and the results show the proposed OCDM-switching has gained a 2 order of blocking probability reduction even though only 5 OCs are employed. Furthermore, OC conversion in OCDM-LSP is proved to be another benefit for high flexibility in optical path provisioning and blocking performance improvement comparing to TDM-LSP.

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.

We previously introduced a concept for admission control in packet switching networks that makes deploying a centralized management agent and collecting resource information in advance unnecessary. The new concept is to tentatively accommodate incoming flows and decide whether or not they can be accommodated after an observation period. We called the admission control scheme based on this concept as tentative accommodating and congestion confirming strategy (TACCS). We have now modeled a TACCS system by combining M/sup X/ /M/c/c loss and M/G/1/K queuing systems and mathematically analyzed its performance and characteristics. The analytical results showed that TACCS enables a domain to control admission without using a signalling scheme or a centralized management agent. We have also provided guidelines for configuring the values of parameters for TACCS.