Pulse or digital communications – Transceivers – Modems
Patent
1997-07-15
2000-07-11
Tse, Young T.
Pulse or digital communications
Transceivers
Modems
370282, H04L 2726, H04B 320
Patent
active
060883863
ABSTRACT:
A modulator/demodulator (MODEM) is equipped with a rotation circuit (TROT) in its transmitting part (TP) and a rotation circuit (RROT) in its receiving part (RP). To compensate for clock speed differences between the clocks of two communicating modems, the receive rotation circuit (RROT) of one of them rotates the phase of received data carriers in proportion to their respective frequencies. Furthermore, to align transmit data symbols with received data symbols, the transmit rotation circuit (TROT) of one of the modems rotates the phase of the transmit data symbols. Thereto, the phase rotation applied to each carrier whereon the transmit data symbols are modulated, is proportional to the frequency of this carrier and to a phase difference measured between a received pilot carrier (PT) and an expected received pilot carrier (PT.sub.-- E). When the rotation to be applied to a transmit data symbol corresponds to a time shift of half the length of one sample, a sample is duplicated or deleted in a transmit data symbol by transmit skip/stuff circuit (TSS).
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patent: 5331670 (1994-07-01), Sorbara et al.
patent: 5872810 (1999-02-01), Philips et al.
"Frequency Domain Echo Cancellation for Discrete Multitone Asymmetric Digital Subscriber Line Transceivers" by David C. Jones, from IEEE Transactions on Communications, vol. 43, No. 2/4, Feb. 1995, New York, pp. 1663-1672.
"Echo Cancellation for Asymmetrical Digital Subscriber Lines" by Younce et al. Supercomm/ICC, 1994 pp. 301-306.
"VLSI DMT Implementation for ADSL" by John Cioffi et al, in the ADSL Standard TiE1.4 with reference No. T1E1.4/93-025.
Modification to DMT Synchronization Pattern Insertion: by John Cioffi et al in ADSL Standard, reference No. T1E1.4/93-089.
"Asymmetric Digital Subscriber Line (ADSL) Metallic Interface Specification", published by American National Standards Institute (ANSI) in Apr., 1994.
"A Multicarrier E1-HDSL Transceiver System with Coded Modulation" by Chow, et al. Published in the issue Nr. 3, May/Jun. 1993 issue of the Journal of European Transactions on Telecommunications and Related Tech. pp. 257-266.
"Performance Evaluation of a Multichannel Transceiver Systems for ADSL and VHDSL Services" by Chow et al., published in NR 6, Aug. 1991 issue of Journal of European Transactions on Telecommunications and Related Tech. pp. 909-919.
Reusens Peter Paul Frans
Spruyt Paul Marie Pierre
Alcatel
Tse Young T.
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