This paper investigates the effectiveness of a network that uses unspecified bit rate (UBR) for a virtual channel (VC) accommodating AAL2 connections. AAL2 is a new ATM adaptation layer that has recently been standardized. Since it is designed to carry low-bit-rate voice signals efficiently, it should be used in the ATM backbone for mobile networks, especially in the IMT-2000 network (International Mobile Telecommunication in the Year 2000 network). Normally, constant-bit-rate (CBR) VCs or variable-bit-rate (VBR) VCs are used to accommodate AAL2 connections. In our previous work, however, we showed that using UBR VCs (equivalent to no VC-level bandwidth management) to accommodate AAL2 connections needs much less VP bandwidth than using CBR or VBR VCs. In this paper, the previous results are extended to the network and the network bandwidth reduction is shown to be larger than that of the virtual path. In addition, the bandwidth reduction achieved by using UBR VCs is comparable with that achieved by introducing AAL2 switching nodes. Based on these results, the core network of the IMT-2000 is discussed.

This paper describes key technologies for establishing a large-scale public switching node system architecture for handling voice and telephony over ATM (VTOA). VTOA is one of the most promising ATM applications, which allows network operating companies to provide a less-expensive but relatively high quality telephone service, by employing voice-data compression and the efficient transmission capabilities of AAL2. We discuss several technical aspects of VTOA handling system architecture, such as the optimum basis for the node, i. e. , STM versus ATM, the appropriate network structure, and suitable signalling. These key points are evaluated from the standpoints of economy, ease of implementation, and extensibility. Our proposed methods should provide the basis for constructing an efficient and cost-effective VTOA handling network.

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.

This paper presents novel multimedia ATM networks which are capable of transmitting voice data efficiently and unify the switching methods among heterogeneous traffic. Fully ATMized multimedia networks are using fellow cell switches. The proposed assembly method can pack plural calls which have different virtual channel connection (VCC) into one cell. Every call in cells is able to be dynamically rearranged by the fellow cell switch to achieve an efficient use of network resources. The switching functions are supported by shared virtual channel identifier (VCI) cells and fellow cells in it. The fellow cell switch for 622 Mbps links is integrated into a single chip. The multimedia ATM networks including voice transmission can be constructed by the fellow cell switches being attached to the standard ATM switches.