High speed dial-up telephone circuit full duplex data transmissi

Details High speed dial-up telephone circuit full duplex data transmissi High speed dial-up telephone circuit full duplex data transmissi

1982-04-01

1984-11-06

Olms, Douglas W.

Multiplex communications

Wide area network

Packet switching

370 32, H04B 150

Patent

active

044816227

ABSTRACT:
A 4800 bit-per-second full duplex modem is described which utilizes the full bandwidth of ordinarily available dial-up telephone circuits for transmission of data in both directions in different pass-band portions thereof. The two pass-bands overlap in about the middle of the telephone band in order to fully utilize that bandwidth for high speed data transmission. The overlap is less than that which will cause a greater error rate than desired from remote echos of transmitted data. Local echos, which are much stronger, resulting from the overlap bandwidth portion are cancelled by an echo cancelling technique. Local echo cancelling is accomplished at the baud rate, generated in each modem, for substraction from a received signal; a cancellation signal is generated from a time varying system that depends upon the modulating and demodulating carrier signals.

REFERENCES:
patent: 3226480 (1965-12-01), Wright et al.
patent: 3655915 (1972-04-01), Liberman et al.
patent: 4101833 (1978-07-01), Bingham et al.
"Design and Simulation of a Digital DPSK Modem for 80 kbit/s Full Duplex Data Transmission on the Subscriber Loop" by di Tria et al, Conference: 1981 International Conf. on Communications, Denver, Colorado, U.S.A., June 14-18, 1981.
"A Microprocessor Implementation of a Switched-Network Full-Duplex 2400 BPS Modem" by Kurzweil et al, IEEE 1981 National Telecommunications Conference, Innovative Telecommunications-Key to the Future; New Orleans, La., U.S.A.; Nov. 29-Dec. 3, 1981.

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