Pulse or digital communications – Systems using alternating or pulsating current – Plural channels for transmission of a single pulse train
Patent
1994-04-14
1996-05-21
Chin, Stephen
Pulse or digital communications
Systems using alternating or pulsating current
Plural channels for transmission of a single pulse train
375240, 375285, 375296, 375340, 375346, 370 6, 370 70, 348388, 348436, 379 93, H04K 110
Patent
active
055197310
ABSTRACT:
An improved discrete multi-tone transmission scheme is describe that contemplates encoding digital data and modulating the encoded data onto a discrete multi-tone signal having a total bandwidth of at least 1.6 MHz. The modulation system is capable of dynamically updating the subcarriers used and the amount of data transmitted on each subcarrier during transmission in order to accommodate real time changes in the line quality over particular subcarriers. In one preferred embodiment of the invention the multi-tone encoding and modulation is done in substantial compliance with the ATIS North American Asymmetric Digital Subscriber Lines standard although a total of 512 subchannels each having a bandwidth of approximately 4.3125 kHz are used. In this system, the subchannels that occur at frequencies above those set forth in the standard are treated similarly to those within the standard range in terms of subcarrier selection criteria. This embodiment contemplates the use of a discrete multi-tone signal having an available bandwidth of 2.208 MHz. The described system permits transmission of digital data at transmission rates of 6 Mbps over telephone lines at distances of two miles even on lines that experience significant T1 crosstalk noise. In one application of the invention, it may be used with ordinary telephone lines such as twisted pair lines to transmit data to remote receivers located up to six thousand feet from the transmitter at digital data transmission rates of at least ten million bits per second (10 Mbps). With more subchannels provided, the number of subchannels available for upstream communications may also be increased.
REFERENCES:
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patent: 4980897 (1990-12-01), Decker et al.
patent: 5285474 (1994-02-01), Chow et al.
patent: 5313467 (1994-05-01), Varghese et al.
Amati Communications Corporation
Chin Stephen
Le Amanda T.
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