Taiju Mikoshi

Optimization of input admissible traffic flow guaranteeing QoS

We propose an admission control method at edge nodes. This method aims at maximizing network throughput and calculates an input traffic limitation ratio at each edge node, which is used for admission control. Since the proposed method only uses input traffic volume information, it does not need to take into account the traffic matrix among edge nodes. Therefore, this method can be easily applied to actual networks in a practical way. We formulate a linear programming (LP) to solve the optimization problem of the input traffic limitation ratio of each node for any traffic matrix. This problem cannot be solved as it is, so we modify the LP problem by applying a duality theorem in the field of LP problems.

PARC: Power aware routing and clustering scheme for wireless sensor networks

In wireless sensor networks constructed from battery driven nodes, it is difficult to supply electric power to the nodes. Because of this, the power consumption must be reduced. To cope with this problem, clustering techniques have been proposed. EACLE is a method that uses a clustering technique. In EACLE, the route selection is executed independently after the CH (Cluster Head) selection. These two phase controls increase overheads and reduce the battery power, which leads to shorten the lifetime of wireless sensor networks. This paper proposes a novel routing and clustering method called PARC for wireless sensor networks that reduces these overheads by integrating the cluster selection phase and the route construction phase into a single phase. However, PARC has a following weak point that the batteries of CHs around the sink node are depleted earlier than the other nodes and the sink node cannot collect sensing data. This phenomenon is called a hot spot problem. In order to cope with this problem of PARC, we propose PARC+, which extends the CH selection method of PARC such as more nodes around the sink can be selected as a CH node. We evaluate our proposed methods by simulation experiments and show its effectiveness.

Improvement of burst transmission delay using offset time for burst assembly in optical burt switching

We propose a novel algorithm for reducing burst transmission delay and packet loss rate. In optical burst switching (OBS), a certain offset time and burst assembly period are needed, leading to transmission delay. In order to reduce the delay, the proposed method transmits a control packet before the burst assembly period expires. Due to this mechanism, a method is needed to estimate burst length. To estimate burst length, the proposed method adopts the Jacobson/Karels algorithm used in TCP. Moreover, to reduce the estimation error, the proposed method uses a head-dropping algorithm for the burst collision procedure. We evaluate packet delay, packet loss rate and estimation error rate by simulation experiments. The simulation results show that the proposed method has a lower packet loss rate and delay than the conventional method and burst estimation error can be neglected.

High-speed calculation method for large-scale multi-layer network design problem

Multi-layer network optimization has been studied for efficient use of network resources by solving Mixed Integer Linear Programming (MILP) problem. Here, the multi-layer network consists of lambda-layer network and IP-layer network. However, when applying this MILP problem for a large-scale network with a few hundred nodes, huge amount of variables are used and cannot be handled by middle size computers. In order to cope with this problem, some heuristic methods have been proposed and evaluated from viewpoints of accuracy and calculation time for their computation results. These heuristic methods reduce variables at lambda-layer and also decompose the original MILP problem into smaller sub-problems and induce an approximate solution by solving these smaller MILP problems. However, these heuristic methods cannot obtain accurate results in many cases. In this paper, we propose a novel variable reduction method at both lambda-layer and IP-layer by excluding long hop routes. We evaluate our proposed method and the conventional methods and show the availability of our method.

High-speed topology construction method for network power saving

Recently a drastic increase of power consumption of network devices has been big problem in the green ICT field. In order to cope with this problem, some power saving method has been proposed, where traffic aggregations are executed and the powers of unnecessary links are turned off. In this method, every links are tried to be turned off and are checked whether traffic congestions are caused or not and whether network disconnections occur or not. However, this method causes frequent change of link on/off and induces network instabilities in the actual network environment, where traffic conditions change in real time. Moreover, in this method, since the shortest hop routing has been adopted, traffic congestions might occur in specific links. In this paper, in order to cope with these problems, we propose a High-Speed Topology Construction method, where an initial topology is constructed by a minimum spanning tree algorithm in order to maximize sleep links. When traffic congestions are caused, a proper link addition proposed in this paper is executed in order to resolve traffic congestions. We evaluate our proposed methods by simulation experiments and show its effectiveness.

Improvement of consumer satisfaction level by energy storage system in smart houses

Recently, due to the stop of the nuclear power plant operations, the shortage of electric power and the increase of electricity prices have become big problems in Japan. The technologies of smart house have attracted great attention to reduce power consumption. Smart houses can reduce the power consumption and electricity costs by optimizing operation times of electric home appliances and by supplying energy from the energy storage system such as battery power supply and electrical vehicles (EV). In this paper, we formulate a mixed integer liner programming (MILP) to minimize electricity costs and maximize consumer satisfaction level in smart houses. We evaluate our proposed MILP from viewpoints of electricity cost and consumer satisfaction level and show that consumer satisfaction level is improved by introducing an energy storage system in smart houses.

Lifetime prolongation of PARC-based wireless sensor networks by mobile sink method

In a wireless sensor network composed of battery-powered sensor nodes, the saving of battery power consumptions of sensor nodes is essential to prolong the lifetime of a wireless sensor network. For this purpose, we have proposed the PARC method, which improves the efficiency of multi-hop communication in wireless sensor networks. However, even in case of using the PARC method, a hot spot problem occurs at node around a sink. Due to this problem, batteries of nodes around the sink are depleted early, and the sink cannot collect any sensing data. In this paper, in order to cope with this problem, we introduce a mobile sink method for the PARC method. The proposed mobile sink moves around plural pre-assigned data collecting points periodically. In order to balance the load among nodes, the data collection times at each stopping point should be optimized. We propose a simple optimization method of data collection times and show the effectiveness of our method by simulation experiments.

Virtual network designs and evaluations for IP over WDM networks

In recent years, the virtual network (VN) for services by IP over WDM has been studied for the flexible and efficient use of network resources. The VNs are constructed by optical paths on the WDM network. Furthermore, by configuring VNs dynamically, resources which have been used for some VN at previous period can be allocated to another VN at the next period, which improves the utilization ratio of network resources. In this paper, we propose the SVN (Static Virtual Network configuration) method and the DVN (Dynamic Virtual network configuration) method for the VN configuration method. We formulate the MILP (Mixed Integer Linear Programming) for the SVN method and the DVN method and evaluate them from viewpoints of resource cost and availability by calculation experiments.

Resilient multi-layer network designs and evaluations

In recent years, multi-layer network (MLN) design methods have attracted great attentions of backbone carriers for their networks designs. In the MLN design, IP networks are constructed on optical path networks on the WDM (Wavelength Division Multiplexing) networks. In the MLN designs, the resilience against link failures is also required. The shared restoration method has been studied to achieve the resilience against link failures. In this method, the same wavelength is shared among plural optical paths, and the backup optical path is set up against link failure using the shared wavelength. In this paper, we formulate an Integer Liner Programming (ILP) for the MLN design using shared restoration method, and also propose a heuristic method for the MLN design. We evaluate these design methods from viewpoints of cost performance and calculation times and show the effectiveness of these design method.

Shared-Tree selection method for aggregated multicast

Aggregated multicast methods have been proposed in order to reduce the size of routing tables in routers for multicast communications, where plural multicast sessions share a single multicast tree called Shared-Tree. STA (Scalable-Tree-Aggregation) method has been proposed as a Shared-Tree selection method, where a minimum size Shared-Tree has been selected among Shared-Trees which contain all destination nodes of a multicast session. In the STA method, the selected Shared-Tree sometimes contains invalid destination nodes for the multicast session and causes the unnecessary traffic load. In this paper, we proposed a novel Shared-Tree selection method which makes it possible to select smaller size Shared-Tree compared with the multicast session by a grafting method. By the grafting method, destination nodes not involved in the selected Shared-Tree can be connected to the Shared-Tree. We can expand the search range of Shared-Trees by the grafting method and select a Shared-Tree, destination nodes of which overlap those of the multicast session as many as possible. In our proposed selection method, Shared-Trees are selected by the measurement of overlapping degree, which indicates how many destination nodes in the multicast session overlap with those in Shared-Trees. Moreover, we introduce a replacement method for reducing the entry size of Shared-Trees. We evaluate our selection method by simulation experiments and show the effectiveness of our proposed method.