No.4 ESS: The Switched Digital Network Plan

Abate, Joseph; Brandenburg, L.; Lawson, Jamie; Ross, W. L.

doi:10.1002/j.1538-7305.1977.tb00564.x

Cited by 19 publications

(1 citation statement)

References 2 publications

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“…They are not restricted to switching just the standard 3 or 4 kHz voice channel. Instead, the 24 channel digroup, consisting of the p = 255 PCM format of the D2 channel bank, becomes the basic unit in facilities provisioning [2]. Significant economies have been demonstrated by directly terminating the digroup carried on 1.544 Mbits/s facilities.…”

Section: Technological Developments Among Commercial Carriers and mentioning

confidence: 99%

The Next Generation CONUS AUTOVON

Shimabukuro

1980

IEEE Trans. Commun.

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Section: Technological Developments Among Commercial Carriers and mentioning

confidence: 99%

The Next Generation CONUS AUTOVON

Shimabukuro

1980

IEEE Trans. Commun.

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A Subjective Comparison of Selected Digital Codecs for Speech

Daumer¹,

Cavanaugh²

1978

Bell System Technical Journal

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Technological advances are continually increasing the economic viability of efficient codecs in telephone networks. A subjective evaluation is described here of the μ255 Pulse Code Modulation (PCM) algorithm and three more efficient techniques, Nearly Instantaneous Companding pcm (nic pcm), Cummiskey‐Jayant‐Flanagan Adaptive Differential pcm (adpcm), and Subscriber Loop Carrier Adaptive Delta Modulation (SLC* adm). These codecs are compared under the conditions of: (i) single encodings as a function of line bit rate, input level, received volume, and error rate, (ii) tandem encodings with intermediate baseband conversion, and (iii) local, exchange, and toll network reference connections where mixed tandem encodings might be found along with typical analog impairments such as loss and random noise. The simulation of the codec algorithms on a minicomputer facility enabled the production of subjective test tapes containing speech processed under these conditions. These tapes were then evaluated in listening‐type subjective tests. It is shown that (i) nic pcm, adpcm, and SLC adm have approximately a 12‐ to 16‐kb/s advantage over μ255 pcm for equivalent subjective ratings, (ii) nic pcm, adpcm, and SLC adm perform comparably over the range of conditions tested; and (iii) 64‐kb/s μ255 pcm can be deployed in a multiple encoding environment with very few restrictions, whereas the use of lower bit rate nic pcm, adpcm, and SLC adm codecs would necessitate more stringent application rules to avoid excessive degradation in tandem encoding situations.

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Synchronization in Intelligent Digital Networks

Grimes

Russo

Lanzafame

et al. 1991

At&T Technical Journal

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Customer expectations regarding the performance of intelligent digital networks can be met only if careful consideration is given to synchronization at every level in the network. This includes synchronization of the public switched and private networks, and performance of the clocks that control customer premises equipment (CPE). Poor synchronization planning at the public or private network level, as well as poor CPE clock performance can degrade customer applications such as video, facsimile, digital data, encryption, voice‐band data, and voice transmission. In this paper, we consider the synchronization philosophies and implementation of both AT&T's national telecommunications network and private customer‐owned networks. We will also discuss the performance of typical CPE clocking systems and describe the synchronization systems used in AT&T's line of Definity® business communications systems.

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No.4 ESS: The Switched Digital Network Plan

Cited by 19 publications

References 2 publications

The Next Generation CONUS AUTOVON

The Next Generation CONUS AUTOVON

A Subjective Comparison of Selected Digital Codecs for Speech

Synchronization in Intelligent Digital Networks

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