Network planning for a public switched telephone network is essentially the same as the company's business strategy. The social environment providing the market for communications services is undergoing rapid change in Japan as it evolves from an era of one basic mainstay service-namely, plain-old telephone service-to one in which a wide range of advanced new services are, or soon will be, available and there is fierce competition to provide those services. This paper covers some of the thinking behind NTT's strategy to put in place a flexible and effectual network that fully reflects the needs and desires of customers in this fast-changing environment.

The globalization of business where single products and services are designed, developed, and manufactured in many different countries signals a significant need for cost-effective and reliable information movement and management capabilities. Similarly, consumers are seeking technologies which will allow them to visit the Smithsonian, scan a book in the Oxford Library, and interview a Japanese monk for a school report, all from the comfort of home. A necessary ingredient for realizing this global society is a strong telecommunications infrastructure. Our paper describes some of the customer needs and technology advances that are causing a revolution in planning global telecommunications networks. We present a new telecommunications paradigm and study its impact in two key areas: multi-country network routing at both the traffic and facility levels, and global network robustness.

The introduction of Integrated Services Digital Networks (ISDNs) poses a variety of new questions on telecommunications network design and planning. Furthermore, the formulation of traditional network design and planning problems need to be revisited in the ISDN context. This paper presents an overview of the recent progress and new challenges in developing ISDN design and planning methodologies that exploit revolutionary new telecommunications technologies. It will cover some important issues for ISDN design and planning, and will concentrate on three issues that are of particular importance: Design of networks with digital information transfer capabilities, design of networks with advanced network/traffic control techniques, and use of reliability objectives for network design and planning.

In an ATM network, there are quality impairments particular to the ATM network such as cell loss and delay variation. During ATM network planning, therefore, various causes of quality impairments should be clarified. This paper overviews ATM network performance issues, and discusses performance requirements for the SDH network which will be applied as a physical layer of the ATM network. It also presents ATM network performance planning methods on cell loss and cell delay.

The Asynchronous Transfer Mode (ATM) is expected to be the basic transmission technology for B-ISDN. Before this happens, however, it will be necessary to predict the impact of fully-deployed ATM-based networks quantitatively. This paper compares the cost-efficiency of an ATM-based network with that of an STM-based network and clarifies the applicable areas of ATM network configurations, in terms of required facilities and considering the effect of statistical multiplexing. It shows cost-effective network configurations based on different service classes and a network configuration suited to ATM. It also discusses the effect of a Synchronous Digital Hierarchy architecture for Virtual Path dimensioning.

This paper describes a method of evaluating operations effort for fiber optic subscriber loops, such as the Central Terminal/Remote Terminal (CT/RT) system, which can economically provide a variety of telecommunication services. Four system configurations with different operation procedures are evaluated by simulation. By evaluating the operating costs associated with service provisioning, it is shown that automatic distributing frames are cost effective in subscriber loops with CT/RT systems. Moreover, the most economical operation strategies for installing and extending subscriber boards are discussed in terms of facility and operations cost.

Over the past few years, the drive towards optimization and globalization of business activities has mandated the integration of various services, an increase in system scale, and the networking of a variety of systems. These requirements can only be satisfied by the introduction of systems that are able to accommodate and control multiple media and integrate LANs and PBXs synergistically. This paper proposes an architecture for next generation private networks called ANS (Areal Networking System) that is targeted at achieving flexible customization in an effort to meet a wide variety of user requirements as well as the ability to efficiently handle multimedia services. Based upon the clarification of various requirements on the ANS architecture, this paper defines two models for the ANS architecture. These models introduce modular building blocks in hierarchical structures that facilitate the custom design of networks. The key technologies for the ANS architecture are also discussed; for example, schemes for logically networking control functions by using virtual connections and a way to implement the LAN function.

We have developed an advanced tool for dimensioning circuit-switched networks, called CNEP (Circuit-Switched Network Evaluation Program) , for effective design of digital networks. CNEP features a high-reliability network structure (node dispersion, double homing, etc) , both-way circuit operation, and circuit modularity (or big module size), all of which are critical for digital networks. CNEP also solves other dimensioning problems such as the cost difference between existing and newly installed circuits, and handles multi-hour traffic conditions, dynamic routing, and multiple-switching-unit nodes. Operations Research techniques are applied to produce exact and heuristic algorithms for these problems. Algorithms with good time-performance trade-off characteristics are chosen for CNEP.

This paper discusses a computer-aided network planning support system called PIGEON that has been developed primarily for advancing countries implementing the applicability to various types of networks and the supportability to the sensitivity analysis. For the implementation of the applicability, the customization by reflecting existing network facilities and their accompanying restrictive conditions into a design result is focused. A case study on the customization shows the effectiveness of the reflection. The procedures are given of the sensitivity analysis in order to examine and to evaluate the effect of the uncertain factors in network planning. In particular, a method called "network modification" is proposed for the sensitivity analysis for uncertain factors associated with a partial network. The network modification efficiently integrates network planner's judgments into a design result by the interactive method. In addition, this paper describes the importance of streamlining the data input and the evaluation of design results, showing the operating time required for each work phase in network planning.

There has been much interest in building corporate private communication networks. This aim requires a method that optimizes the economical aspect of network configurations. The authors propose a network design method supported by knowledge-base. This method is used to design a cost-effective corporate communication network, using leased lines. The knowledge-base description depends on the production rule. The network configuration is improved by introducing expert knowledge, after designing the network by a conventional algorithm. Design results show the advantages of the proposed method.

The establishment of an intelligent network service operation architecture is important for facilitating development and integration of service operation systems. To do this, the basic concepts and goals of service operation items must first be clarified. Then, the necessary procedures as well as the required data on the behaviors of customers, operators and operation systems must be described. These various points are discussed based on an operation study methodology.

This paper proposes design schemes which obtain an efficient spare-channel assignment against single and double link failures for a self-healing network. Spare-channel design problems can be formulated as a linear-programming (LP) problem when variables are assumed to be continuous. For the problem, the proposed algorithm effectively solves a sub-set of whole constraints by making use of a maximum-flow algorithm in an iterative manner. It is shown that the maximum number of iteration times is limited by the number of links in the network. Moreover, the relation between the design function and the self-healing function is discussed. It is also shown that the cooperation of the two functions can realize more effective control in large scale networks.

This paper describes the application of a neural network to the optimal routing problem in broadband multimedia networks, where the objective is to maximize network utilization while considering the performance required for each call. In a multimedia environment, the performance required for each call is different, and an optimal path must be found whenever a call arrives. A neural network is appropriate for the computation of an optimal path, as it provides real-time solutions to difficult optimization problems. We formulated optimal routing based on the Hop field neural network model, and evaluated the basic behavior of neural networks. This evaluation confirmed the validity of the neural network formulation, which has a small computation time even if there are many nodes. This characteristic is especially suitable for a large-scale system. In addition, we performed a computer simulation of the proposed routing scheme and compared it with conventional alternate routing schemes. The results show the benefit of neural networks for the routing problem, as our scheme always balances the network load and attains high network utilization.

This paper provides an analytical method to evaluate the cell loss probability in ATM (Asyncronous Transfer Mode) networks employing statistical cell multiplexing. A fairly simple design procedure for path/link capacity is also developed. It is demonstrated that the proposed method yields a conservative capacity value over the entire range examined. This was confirmed by comparing the results obtained through the proposed method with computer simulation results. The method yields a link capacity design approach that can effectively handle different bandwidth and types of VPs within the same link. Evaluations show that the method allows 10% to 1400% more traffic than possible with the peak bandwidth allocation scheme in the parameter range we examined; the specified cell loss probability is set at 10^-9. As a result, it is shown that the proposed analytical procedure to evaluate the cell loss probability in statistical cell multiplexing, and the path/link capacity design method are effective and practical even though they use fairly simple procedures.

In this paper, restricted overflow strategy is proposed as a novel channel access strategy for the queueable hierarchical channel structure, which has been proposed as one of "Wideband-ISDN" channel structures. In this policy, overflow from higher bit rate channels to lower bit rate channels is partly restricted by the number of waiting customers in the higher channel's buffer. Therefore, thresholds, which restrict overflow, are considered on the buffer. First, we present the system model with two types of services and restricted overflow strategy. Next, we provide a queueing analysis of this strategy. After that, some numerical results of both conventional overflow strategy and restricted overflow strategy are presented, and we compare the average holding times under these strategies. Finally, we show that, if we choose appropriate thresholds, the average holding time of higher level traffic is improved.

An integrated multiplexer in intermediate node is analyzed. The multiplexer is modeled as a system with multiple synchronous servers (channels) and having two kinds of customers. Between the two, one is wideband (WB) and the other is narrowband (NB); they are queueable with the same deterministic service time. The WB customer is given higher priority of channel access than the NB. To incorporate the delay constraint of WB, we use a simple instant discarding scheme for WB. As a result, the system states defined just after the beginning of a slot form an one-dimensional embedded Markov chain. This makes the analysis computationally tractable. The performance measures such as queue length distribution, average blocking probability, and average waiting time are obtained, particularly, the waiting time distribution. Some interesting numerical examples are discussed. Simulation results are also provided to help verify the validity of analysis.

Voyager Neptune radio science data were collected using three antennas on Earth on August 25, 1989. A parabolic antenna at Canberra, Australia, of 70 meter diameter received 2.3GHz and 8.4GHz carriers. The 64 meter parabolic antennas at Parkes. Australia and Usuda, Japan, received only the 8.4GHz and only the 2.3GHz carriers, respectively. It is necessary to reduce the frequency variation in the received signal carrier to extract accurate information on physically interesting objects such as Neptune's atmosphere, ionosphere, or the rings. After the frequency stabilization process, the frequency drift was reduced from 180Hz down to a maximum of 5Hz, making it possible to reduce the data bandwidth and, consequently, the data volume, by a factor of 30. The uncertainty of the signal frequency estimates were also reduced from 5 down to 510^-3Hz/sec above the atmosphere, from 5 down to 0.5Hz/sec in the atmosphere, and from 50 down to 3Hz/sec at the beginning and the end of the atmospheric occultation. Much of the remaining uncertainty is due to scintillations in Neptune's atmosphere and cannot be reduced further. The estimates are thus meaningfully accurate and suitable for scientific analysis and coherent arraying of data from different antennas. Two results based on these estimates are shown: a preliminary temperature-pressure (T-p) profile of Neptune's atmosphere down to a pressure level of 2 bar computed using the Usuda 2.3GHz data, and a multipath phenomenon in the atmosphere seen in Canberra 8.4GHz data. Our T-p profile shows good agreement with the results presented by Lindal et al. within 1K below 100mbar pressure level, even though our result is based on an independent data set and processing. A comparison of the multipath phenomena at Neptune with that at Uranus implies that it was created by a cloud layer with a smaller scale height than the atmosphere above and below it. The processing methods described were developed in part with the interest to coherently array Canberra, Parkes and Usuda data. In this sense, while this paper does not extend any science results, the observations and results are derived independently from other published results, and in the case of Usuda, are completely new.