Large-Scale Integration of Hybrid-Method Digital Subscriber Loops
Agazzi, O.
Hodges, D.
Messerschmitt, D.
Univ. of California, Berkeley, CA, USA;
This paper appears in: Communications, IEEE Transactions on
Publication Date: Sep 1982
Volume: 30,
Issue: 9
On page(s): 2095- 2108
ISSN: 0090-6778
Current Version Published: 2003-01-06
Abstract
This paper reports on studies concerning the feasibility of large-scale integrated realization of the circuits needed to provide hybrid-mode full-duplex digital transmission at 80 kbits/s or higher rates over standard local telephone loops. Alternative means of achieving the required 60 dB or so of echo cancellation have been studied in detail. The conclusion is that a combination of analog and digital circuit techniques permit practical MOSLSI realization of the complete modem, including filters, echo canceller, timing recovery, and A/D and D/A converters, without need for external circuit elements, trimming, or adjustments. The preferred system configuration has been evaluated by means of analysis, simulation, and laboratory and field measurements. A complete full duplex system, including an experimental NMOS integrated circuit echo canceller, was built and tested. Measurements showed a bit error rate lower thanl0^{-8}with line attenuation up to 40 dB, operating at 80 kbits/s. We conclude that a fully integrated MOSLSI ciruit to implement all functions for a hybrid-mode digital local loop is entirely feasible.
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