A group of 18 datacoms companies have unified round a standard for asymmetric digital subscriber line transmission, capable of spectacular speeds along conventional copper cables. Their move creates the basis for mass deployment of ADSL for the first time, but leaves supporters of rival systems, such as the one put forward by AT&T spin-off Paradyne Corp, out in the cold (CI No 3,017). The 18 companies have backed DMT Discrete Multi Tone transmission standard for asymmetric digital subscriber line and have made this the basis for their proposed re-write of the American National Standards Institute standard for transmissions – ANSI T1E1.4. Proponents of DMT has been fighting it out since 1993 with two main rival proposals for phone line transmission standards including CAP Carrierless Amplitude/Phase modulation – developed by Paradyne Corp, and QAP Quadrature Amplitude Phase. But the strength of support for DMT means that backers of the other systems face an uphill struggle. Amati Communications Corp, of San Jose, California developed the DMT algorithms, and has licensed the technology to a number of heavyweight companies, including Motorola Inc, Siemens AG, Texas Instruments Inc and Northern Telecom Ltd. Supporters of DMT are claiming a download capacity of 8Mbps and upload of 640Kbps, compared to ISDN-2’s 128Kbs. The advantage of DMT is that the whole frequency is broken into 4KHz channels which are tested for Signal to Noise ratio, and an appropriate quantity of data is piped down each frequency channel. DMT leaves 0-4Khz of line frequency for voice traffic, with the remaining 4KHz to 1.1GHz for data. The new standard will make high speed links to the internet possible. US Robotics Corp and Texas Instruments Inc are producing a ADSL/x2 modem, with Aware Inc’s flavor of DMT. All the companies predict that an ADSL service will be available to customers later this year, at a cost of between $1,000 and $2,000 per line, though the costs should fall, as the market develops, to $500 by late 1997.
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