This paper deals with a study of a problem for finding the minimum-cost spanning tree with a response-time bound. The relation of cost and response-time is given as a monotonous decreasing and convex function. Regarding communication bandwidth as cost in an information network, this problem means a minimum-cost tree shaped routing for response-time constrained broadcasting, where any response-time from a root vertex to other vertex is less than a given time bound. This problem is proven to be NP-hard and consists of the minimum-cost assignment to a rooted tree and the minimum-cost tree finding. A nonlinear programming algorithm solves the former problem for the globally optimal solution. For the latter problem, different types of heuristic algorithms evaluate to find a near optimal solution experimentally.

A distributed power supply system with highly efficient characteristics has been developed to replace conventional centralized power systems in telecommunications offices. In this system as in conventional centralized power systems, a stand-by energy system composed of batteries and engine-generator sets is used as a back-up system for the commericial power lines. However, the distributed power system, except for the engine-generator set, is installed in the telecommunications room. Thus, the floor load limitation is an important design factor. This paper describes a stand-by energy system design that considers floor load conditions and is based on reliability analyses. These analyses show that the distributed power system should be designed as follows: (1) Using a fully duplicated engine-generator set. (2) With battery reserve time reduced to one sixth that of conventional centralized power systems. (3) With transfer switch unavailability designed to be less than one half of the existence switch unavailability.

The stage method used in the analysis of traffic or reliability models causes an increase in the number of state. For example, the k2-stage Erlang distribution is used to approximate the general type of distribution which has a coefficient of variation β1/k (ex. the 100-stage Erlang distribution is used for β0.1). This paper proposes a new type of stage method that needs only two stages to approximate a general distribution with arbitrary coefficient of variation β(0β) and presents some useful applications.

Multimedia applications such as music or video streaming, video teleconferencing and IP telephony are flourishing in packet-switched networks. Applications that generate such real-time data can have very diverse quality-of-service (QoS) requirements. In order to guarantee diverse QoS requirements, the combined use of a packet scheduling algorithm based on Generalized Processor Sharing (GPS) and leaky bucket traffic regulator is the most successful QoS mechanism. GPS can provide a minimum guaranteed service rate for each session and tight delay bounds for leaky bucket constrained sessions. However, the delay bounds for leaky bucket constrained sessions under GPS are unnecessarily large because each session is served according to its associated constant weight until the session buffer is empty. In order to solve this problem, a scheduling policy called Output Rate-Controlled Generalized Processor Sharing (ORC-GPS) was proposed in [17]. ORC-GPS is a rate-based scheduling like GPS, and controls the service rate in order to lower the delay bounds for leaky bucket constrained sessions. In this paper, we propose a call admission control (CAC) algorithm for ORC-GPS, for leaky-bucket constrained sessions with deterministic delay requirements. This CAC algorithm for ORC-GPS determines the optimal values of parameters of ORC-GPS from the deterministic delay requirements of the sessions. In numerical experiments, we compare the CAC algorithm for ORC-GPS with one for GPS in terms of schedulable region and computational complexity.

In recent years, studies on multi-hop wireless networks have been made by many brilliant researchers. Such a network consists of a set of mobile nodes having wireless communication devices, and is constructed by the nodes autonomously. The most serious problem on the network is the difficulty of network topology management. All nodes are freely movable and their topology is dynamically changing continuously, so it is difficult to determine the paths to any nodes in the network. Although a classical flooding algorithm is a robust algorithm in that situation, the number of retransmitting nodes increases beyond what is necessary. In this paper, a new and more efficient information dissemination algorithm called WDD is proposed, which can substitute for various broadcasting algorithms by just selecting an appropriate waiting-time function. The algorithm is implemented and its applicability is evaluated on a network simulator.

This paper discusses a formulation of a basic theory of the information systems, where information is not only transmitted, but is also processed and memorized during the transmission. A deterministic procedure applied by an information system is defined as a logical work, and two measurements with information X, information quantity I(X) and information vitality T(X), are introduced. A system with the ability of transmitting, processing and memorizing information is called an information engine. A system of interconnected information engines is called an information network. The power of an information engine is defined as the maximum capacity of the logical works performed by the engine, and important properties of total power of information network are derived. Response time characteristics and cost minimizing problems of an information network are also discussed.