Kiyoshi Maruyama

A general packing algorithm for multidimensional resource requirements

Many problems in resource allocations, memory allocation, and distributed computer system design can be formulated as problems of packing variablesized items into fixed-sized containers in order to minimize the total number of containers used. In this paper, a generalized packing algorithm that encompasses many well-known heuristic packing algorithms is proposed. Simulation results on this generalized packing algorithm are described, and their implications are discussed. The objective of this paper is to investigate the performance of various heuristic packing algorithms within a general framework, to obtain numerical estimates on their efficiency, and to provide guidelines on the use of these algorithms.

Wireless message courier

Wireless coverage is often problematic. This is especially true for mobile radio networks, e.g., cellular networks. It is a very frustrating experience for a mobile user finding out that he is out of the coverage of his wireless service provider when he needs to send an emergency message. This paper proposes a method and system for delivering electronic messages over a wireless cellular communications network when the sender of a message is out of the coverage area. With this method the message is broadcasted repeatedly until a mobile wireless courier receives the message and stores the message. When the courier is within range of a base station of the cellular communication network, it then transmits the stored message to the base station for delivery.

Discrete link capacity and priority assignments in communication networks

This paper deals with the problem of discrete link capacity assignment in store-and-forward packet switching communication networks. Our problem formulation calls for minimizing the network cost while satisfying all the average packet delay constraints specified for different classes of packets. Heuristic algorithms which give near-optimal solutions of the problem are developed. We first describe a discrete link capacity assignment algorithm for networks with arbitrarily defined classes of packets having individual delay constraints. The problem of priority assignment on different classes of packets is then investigated, and an algorithm is developed which assigns suboptimal priorities on classes of packets based on parameters such as delay requirement, path length, packet length, and packet rate. These two algorithms for capacity assignment and priority assignment are combined and tested over a number of examples. It is found that a substantial reduction on network cost can be achieved by the use of a simple priority queuing discipline.

Heuristic design algorithm for computer communication networks with different classes of packets

A typical operating environment of a packet switching (store-and-forward) computer communication network is that it is shared by many users with different classes of packets. Packets may be classified in a very general fashion by types of users, messages, applications, transactions, response time requirements, packet parameters such as packet rate and length, and by network parameters such as source-destination and path length. A well-designed network must provide access and performance assurance to all packet classes. This paper presents a heuristic algorithm for designing such a communication network. The algorithm presented contains heuristic algorithms for discrete link capacity assignment, priority assignment, and flow assignment problems with an additional feature which allows one to alter network topology interactively. Sample results from application of the overall network design are also given.

On the selection of primary paths for a communication network

Abstract This paper deals with a non-bifurcated flow assignment problem in communication networks in which communication paths are limited to a set of pre-selected paths for each node pair. This problem is formulated as a mixed 0–1 linear model with multiple-choice constraints. A heuristic algorithm is presented, which takes a straightforward iterative approach, conceptually similar to that of the Simplex method, for finding the characterized local optimal solution. Several subprocedures which exploit the special structure of the model are included to make the algorithm computationally efficient. The relaxed linear programming model is used for the analysis of the algorithm, and its solution is found to be a tight lower bound. Applications of the algorithm to problems with other performance criteria are also suggested. Computational experience obtained thus far indicates that the algorithm almost always guarantees a quick convergence to a good suboptimal solution.

An approximation method for a class of queueing systems

Abstract We consider a queueing system with an ordered hunt. Specifically, we consider a communication system in which messages arrive at a node that has n output links numbered 1,…,n, and an arriving message is processed by the lowest numbered idle link. Obtaining such steady-state parameters as the expected delay of an arbitrary message and the utilization factor of each link requires knowledge of the complete state space of the system and the solution of 2 n linear equations. In this paper we develop a method of computing the approximate values of these parameters without the need for the knowledge of the complete state space and the solution of 2 n linear equations.

Optimization of mixed-media communication networks

Abstract In the design of a communication network one may consider, among others, response time, cost, throughout, reliability, availability as performance parameters. Satellite communication technology introduces new opportunities to satisfy these considerations by taking advantage of characteristics inherent in satellite links as well as that in terrestrial links (e.g., satellite links have greater inherent delays but may have more cost effective channel bandwidth than terrestrial links.) In this paper, we describe an algorithm for the problem of designing a store-and-forward packet-switched computer communication network with multiple packet classes using both terrestrial and satellite links. The algorithm is heuristic in nature and is an extension of the design algorithm which has been developed for designing terrestrial networks to include satellite links. As for satellite access methods, only dedicated channel access methods are considered. Some design examples are also given.

Zephyr: toward true compiler-based programming in Prolog

Prolog is widely used in prototyping, especially in artificial intelligence, but it has yet to gain widespread acceptance in application development. We think that the problems in this area result from the programming style enforced in existing Prolog systems. Zephyr is a new Prolog system refined and enhanced to help solve such problems. It allows users to do modular programming by always using a compiler instead of an interpreter. In this paper, we describe the unique features of Zephyr which make this possible, focusing especially on package, metafunctions, and tables, and the implementation of the system on OS/2®.

Dynamic route selection algorithms for session based communication networks

A session-based communication network is a store-and-forward message (or packet) switching network in which each session (conversation from logon until logoff) is assigned to a single communication route (or path) until its termination. Examples of such networks are TYMNET and SNA. A route selection algorithm can be either static or dynamic. A static selection is based on given route selection tables which are usually provided to the system by the system generation process. A dynamic selection uses dynamically changing information of the network for determining an optimal route for the new session to be assigned to. This paper develops both static and dynamic route selection algorithms which may be used in a session-based communication network. Route selection algorithms will be classified into several classes depending on the network work-load information available for making decisions. It will be shown that very simple algorithms give good robustness with good response time.