A VIRTUAL STM TRANSMISSION METHOD BASED ON ATM NETWORK

This paper considers a new transmission method (quasisynchronous trans fer mode, Q-STM), as a means to eliminate both the cell loss and the n etwork delay fluctuation in an ATM network. The concept of time-switch in circuit switching is introduced into the ATM switching framework. A switching structure and the call establishment procedure are propose d. In the proposed method, the time-switch is introduced, which elimin ates in principle the output port contention in the ATM switching fabr ic. By preparing a buffer with a certain capacity, cell loss due to bu ffer overflow in the output port of the ATM switch can be completely e liminated. The concept of subframe is newly introduced, which serves a s the unit of time-switching. A three-layered structure is applied to the frame structure, composed of the frame, the subframe, and the slot . This helps to reduce delay due to time-switching, compared to the ca se in which the concept of subframe is not introduced, while maintaini ng the flexibility of bandwidth allocation. Additionally, the method i s based on ATM switching, and the ordinary ATM cells not bound to the frame can be transmitted and ATM-switched by the idle slot in the fram e. This enhances the features of ATM, i.e., effective use of the circu it by the statistical multiplexing effect. The basic characteristics c oncerning the quality of the ordinary ATM cell are analyzed by simulat ion.