Sang-Baeg Kim

An optimal establishment of virtual path connections for ATM networks

A number of optimization models for the establishment of virtual path connections (VPCs) with reserved capacity have been proposed in the literature. All of them, however, failed to reflect the trade-off between increased capacity costs and reduced control costs explicitly in their formulations. the present authors develop a mathematical formulation for an optimal strategy for the reservation of capacity on VPCs, considering the trade-off between increased capacity costs and reduced control costs. In this formulation, they also consider the reservation of buffers on VPCs. Algorithms and numerical results are presented.

/spl Sigma/-matching technique for MMPP modeling of heterogeneous ON-OFF sources

It has been believed that the MMPP (Markov modulated Poisson process) model is inadequate for describing heterogeneous sources because of the complexity of the parameter matching. The authors develop a simple and good parameter matching technique, called the X-matching, for the MMPP modeling of heterogeneous ON-OFF sources. It is based upon the well known property of MMPPs that the superposition of MMPPs is MMPP; each traffic class is modeled by a 2-state MMPP using average matching and then their superposition becomes a 2/sup L/-state MMPP where L is the number of traffic classes. The authors evaluate the performance of the /spl Sigma/-matching for various traffic classes.

Design of local networks using USHRs

We consider the problem of designing a local network in a two‐level telecommunication network. Given one or two hub nodes, central offices (COs) and conduits, the problem is to find a set of unidirectional self‐healing rings (USHRs) which covers all COs and satisfies all demands at minimum cost. The solution approach used is the decomposition and column generation. Master problem and subproblem are modeled as integer programming models. After the optimal solution to linear programming relaxation of the master problem is obtained, a branch‐and‐bound algorithm is used to get an integer solution. A set of valid inequalities for a subproblem is given and a branch‐and‐cut algorithm is used to find an optimal solution to the subproblem. Computational results using real data are reported.

Mathematical models for dimensioning of ATM networks

The dimensioning problem of asynchronous transfer mode (ATM) networks is considered to be complicated due to the heterogeneity of services and the statistical multiplexing gain resulting from the resource sharing of connections. In ATM networks, each connection can require a different bandwidth and the necessary bandwidth for connections is a complicated function of the number of connections, traffic parameters of each connection, and cell level quality of services, which makes the dimensioning problem considerably more difficult. In this paper, we propose mathematical models for dimensioning ATM networks, based on the virtual channel assignment problem, introduced by Kim (1995). Algorithms and numerical results are also presented.

An optimal VP-based multicast routing in ATM networks

A number of multicast tree algorithms have been proposed in the literature. Their approach to modeling the problem has some drawbacks in applications for ATM networks since only a single multipoint connection request is considered in the presence of link capacity constraints. In this paper, we present a detailed mathematical model for the generalized multicast arborescence (i.e., a roofed out-tree) problem in which there are a number of concurrent multipoint connections of various traffic types. Point-to-point connections are also considered as a special case of multipoint connections. A solution to the model determines, in the most economical way, an establishment of VPCs with reserved capacity and multicast arborescences using the established VPCs for multipoint connections. This model is a natural extension of the virtual channel assignment problem introduced by Kim (1995). Algorithms and numerical results are presented.

Additional Channel Assignment in a Cellular System by Graph Theoretic Model

This paper presents graph theoretic models for assigning the additional channels into the traffic congested cells in a cellular system. We investigate the relationships between the suggested models and other optimization problems.We show that the additional channel assignment problems can be solved efficiently for many special cases and use this property to develop heuristic methods for the general case.

Optimization models and algorithms for planning ATM networks

The network planning problems for ATM networks are completely different from conventional ones because ATM networks must support various types of traffic, each of which has different characteristics such as holding time, average bit rate, and peak bit rate. In the initial deployment of ATM networks, basic network planning problems are to determine the locations of switching nodes and link capacities between selected nodes. We propose detailed mathematical models and algorithms useful for the problems encountered in planning ATM networks. These models include the facility location and dimensioning problems. We also consider routing problems which are closely related to the dimensioning problem.

An optimal deployment strategy for ISDN switches in metropolitan networks: modeling and algorithm

In the initial stage of ISDN, ISDN switches (hosts) are installed in the main areas and the other areas are covered by remote systems. As the number of subscribers of a remote system increases this remote system will be replaced with a host, considering costs of hosts and remote systems. We formulate the problem of finding an optimal deployment strategy of ISDN facilities, mainly switch and remote systems, over a planning horizon using an integer programming and develop a heuristic algorithm for the problem. The heuristic algorithm developed here uses a backward approach from the final time of the planning horizon and can be efficiently implemented for determining the ISDN switch installation time.

Towards real-time optimal management of virtual paths in ATM-based B-ISDN's

We propose a static routing model for finding an optimal logical network configuration of a given ATM-based B-ISDN. The model is essentially identical to the model proposed by Kim (1995) which finds a virtual path configuration in which an optimal trade-off is achieved among the relevant gains of ATM technology. Unlike Kims model, however our model explicitly considers the VPs quality of service to enhance the practicality and the bandwidth utilization. We propose a heuristic algorithm tailored to the computational structure of the model. A computational experiment shows that the algorithm finds good solutions in dramatically reduced computation time compared to the existing algorithm. This suggests the possibility of a real-time VP management system in which optimal routing is implemented on-line with dynamic routing, to maintain the optimality of the current solutions.

An optimal dimensioning of ATM networks

A number of optimization methods for the dimensioning problem of ATM networks have been proposed in the literature. Two important constraints mentioned in the Recommendations for the dimensioning of ATM networks (e.g., E.735, E.736, E.737) but missed in most of the literature are the modularity of resources allocated to a transmission path (TP) and the non-bifurcation of a VP link over more than one TP. Most of the existing dimensioning methods simply allocate resources to established VPCs and link groups without considering the module sizes of the resources and the non-bifurcation of the VP link. We propose mathematical models for dimensioning ATM networks, based on the network synthesis methods and a generalized bin packing problem, where the modularity of resources allocated to a TP, the non-bifurcation of a VP link over more than one TP, and the concept of bandwidth modules are taken into account. Algorithms and numerical results are also presented.