An integrated access terminal for wideband packet networking: Design and performance overview

Abstract

In order to provide for more eficient means of handling the changing nee& of voice, data, and image trafic, ATdT has introduced the Integrated Access and Cross-connect System (IACS). This paper will focus on the design and performance of a component of the UCS. the Integrated Access Terminal (IAT) which performs the integration and packet multiplexing @nctions, and also provides circuit and packet cross-connect capabilities. Based on packet switching, proven digital signal pmcesn'ng techniques, and standard protocols, the U T extends packet switching of data to voice and to image, and provides a variety of techniques to optimize the use of bandwidth and the quality of service. Congestion control and bandwidth allocation are critical issues in the integration of diflerent troffic types. One of the congestion control schemes used in the U T is block dmpping on voice packets. The IATalso usesa dynamic bandwidth allocation scheme which efficiently integrates packetized voice and data traffic. This allocation scheme guarantees a certain bandwidth to both voice and data queues, and at the same time allows each queue to use any bandwidth momentarily unused in the other queue. We present results k e d on modeling and subjective listening tests of voice quality when subjected to block dropping in a network. The results show that excellent performance is achiewd in the IATfor both voice anddata. We demonsrate that packetized voice is technologically ideal for integration of services, and one can expect (at better than 4:1 compression ratios) a voice quality virtually indistinguishable from that of the best circuits in an existing digital network