In the basic user/network interface of ISDN (ITU-T Recommendation I. 430), the D-channel is shared by up to 8 terminals for signal and data packets. An analytical model is proposed to reveal the performance characteristics of the access control scheme for the D-channel. Numerical and simulation results are shown to demonstrate the performance differentiation of the terminals with different priorities. It is observed that the mean signal delay at low load may become large because of long service time for packets, and that the priority mechanism may not work properly when the loads at terminals are very asymmetric.

ATM technology can integrate not only new multimedia services but also existing services such as plain old telephone services (POTS) and narrow-band ISDN (N-ISDN) services. We developed ATM subscriber line interface circuits (ATM-SLIC), which can accommodate POTS or N-ISDN subscribers, and a trial ATM access switching system using the ATM-SLICs. This paper proposes embedded trunk functions, a message-type signaling transfer method, an economical ATM interface structure, and a cell-based system control method. Moreover, it shows the main characteristics and efficiency of these proposals in terms of experimental data.

The ATM switching system accommodating the public switched telephone network (PSTN) and narrowband ISDN (N-ISDN) subscribers should ensure the continued support of existing services and applications and guarantee the same quality of voice services for the telephone users. The voice message connection control discussed in this paper is one of the various technical issues for voice services in the interworking function unit, IWF between asynchronous transfer mode (ATM) node and existing synchronous transfer mode (STM) node [2]. We describe the technical points for the implementation of the voice message connection control with the consideration of the development time and cost. And then we discuss several technical problems such as mapping pulse code modulation PCM coded voice data into an ATM cell, different switching operation, keeping performance of the ATM-PSTN interworking system and then present benefits of the voice message connection control processing from the hardware/software point of views.

Realizing an effective channel connection scheme and a useful human-machine interface is important for popularizing the audio-visual communication services that should become significant in the near future. This paper describes a terminal design that is applicable to various audio-visual communication services. First, future audio-visual services are classified into three types: Videophone, Tele-monitoring and Video On Demand(VOD). The requirements for these services are discussed in detail. Second, a channel connection scheme is specified taking into consideration for the requirements and characteristics of various networks such as N-ISDN and LANs. Terminals based on these specifications are developed as prototypes and demonstrated to confirm the validity of these specifications.

This paper deals with network performance of 64kbit/s-based services supported in an ATM network and an ATM interworking network with 64kbit/s-based networks. It first clarifies network performance issues giving a model and objectives of study and experiment. A result of computational analysis is then presented, where a cell loss ratio of an order of 10-4 or 10-5 is obtained to give a performance equivalent to that currently used as objective values in existing networks for a 64kbit/s digital level. In order to capture the impact of cell loss and associated performance for application levels, an experimental test has been carried out using typical applications. Test results show that the cell loss ratio needs to be approximately ten times better than the bit error ratio for comparable performance for application levels. A cell loss ratio of better than 10-5, or an order of 10-6 considering an interworking situation, seems to be necessary according to the test results. It is further clarified by the test that a single cell is more valuable than a multiplexed cell for providing better cell loss resilience characteristics. Although not all applications of 64kbit/s networks have been tested, it is expected that the test results can be used as guidance for considering the support of 64 kbit/s services in an ATM and interworking networks.