Importance

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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. In some embodiments bandwidths of 8 MHz or more are provided. 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. However, additional subchannels (such as a total of 512 subchannels) may be used and/or subchannel bandwidths of greater than 4.3125 kHz may be 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. The described system permits transmission of digital data at transmission rates of six to 55 Mbps over twisted pair telephone lines at distances of 1200 meters even on lines that experience significant crosstalk noise such as T1 or E1. In another application, the invention may be used with ordinary telephone lines such as twisted pair lines to transmit data to remote receivers located up to 2000 meters from the transmitter at digital data transmission rates of at least ten to fifty million bits per second (10-50+ Mbps). With such an arrangement, the bandwidth available for upstream communications may also be increased.

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First Claim