Updated cable model standard tries to outrun DSL
By Will Wade
EE Times
(09/21/00, 6:30 p.m. EST)
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SAN MATEO, Calif. — Samples of the first chip sets adhering to an upgraded version of the standardized format for cable modems are appearing, even as digital subscriber lines, cable modems' main competitor, are making gains in bringing high-speed digital data to the home.
Both Broadcom Corp. and Philips Semiconductors are sampling integrated chips for cable modems based on the 1.1 version of the data over cable system interface specification (Docsis), completed earlier this year. While the initial Docsis spec simply defined the format for sending digital data over standard coaxial cable, piggybacked atop TV programming, the newer one also includes encryption, telephony service and quality-of-service to support videoconferencing or video on demand.
Philips' position as a supplier to the cable modem chip market contrasts sharply with that of Broadcom, currently the market's leading supplier, with more than 90 percent of total market sales, according to some analysts. "Cable modems are a very attractive market for us," said Rich Nelson, director of marketing for Broadcom's cable TV unit. "They are ideal for systems such as home gateways, which can route digital data and entertainment all through the home."
Philips claims a significant presence in the market with proprietary designs sold into non-Docsis modems. That business has been invisible to most observers because customers have not wanted to disclose their silicon suppliers. The Docsis-compliant move effectively means entering a new market, said Peter Brown, director of marketing for the cable networking group at Philips.
Home gateways
Broadcom is pushing the home gateway vision with its new part, the BCM3352. Besides a high-bandwidth connection for Internet access, the chip also supports voice services and can carry up to four separate phone channels, so a home can have four phone numbers, with each in use simultaneously. The chip supports a home networking capability, using the Home Phone Networking Alliance (HomePNA) format, that will let PCs, peripherals and other devices tie in to the system.
The basic idea is for the single-chip BCM3352 to sit at the heart of a home gateway box, which could be attached to the side of a house, with the internal phone lines becoming both the home network and the voice telephone system, said Nelson. "This is the first single-chip part to incorporate all of these functions," he said.
Philips' PTD1100 Venus chip is similar, but does not feature the integrated HomePNA cores or telephony functions. It supports both PCI and USB connections for linking other systems. Upcoming versions of Venus will be aimed at the set-top box segment, with companion chips acting as television tuners and the USB links used to connect PCs and other peripherals, Brown said. Philips also sees cable modems as the entry point for a broadband pipe into the home, and Docsis as key to transforming these systems into minirouters to direct digital traffic throughout the house. "This part is ideal for a home gateway," he said.
Texas Instruments Inc. and Conexant Systems Inc. are also expected to introduce similar devices in the next few months. The Broadcom chip is expected to ramp into volume production by the second quarter of next year, although Nelson said system makers are still testing their designs for the revised Docsis format, and are not likely to need the chip in volume until the second half of 2001. Production volumes of the Philips chip are scheduled to be available early next year.
Cable modem systems generally offer bandwidth as high as 40 Mbits/second, which is higher than the speeds typically offered to consumers through DSL. Both Nelson and Brown said that was a key to making cable the better delivery vehicle for advanced functions supported by Docsis 1.1.
But even with higher speeds, DSL may be overtaking cable in the consumer market, said Mike Paxton, senior analyst for converging markets at Cahners In-Stat Group (Scottsdale, Ariz.). DSL subscribers worldwide are forecast to surpass cable modem users by next year, according to Cahners In-Stat. By 2002, there will be almost twice as many DSL users as cable modems, Paxton predicted, "but the total market is probably big enough to support both of them." |
