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The March 17, 2003 Issue Provided by System Dynamics Inc.
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A Different Approach to DSL - An Interview with Celite Systems

In last month's issue, we briefly mentioned Celite Systems a start-up company with a new approach to broadband over phone lines. Celite (pronounced seh-LEET) says its approach blends the best elements of standard DOCSIS cable modem technology with the best elements of standard VDSL technology. Although the company is a relative newcomer to the industry, its team is composed of industry veterans, including CEO Roger Dorf who founded Promontory and sold it to Nortel.

Since it was novel to hear DSL and DOCSIS mentioned in the same sentence, we decided to learn more about their technology, and arranged a phone interview with Tim Waters, Celite's Vice President, Marketing and Business Development.

Celite architecture --> Click for larger pictureCelite's approach, while operating over twisted-pair phone lines, is more like a cable approach than the traditional DSL approach. Celite hangs a metal box it calls a "DSL headend" on each neighborhood cross-connect cabinet. This box is pre-connected to a subscriber pair for each home in the neighborhood, so a new subscriber can self-install the matching Celite broadband modem. The backhaul side of the DSL headend is connected to the CO by up to eight ADSL or T1/E1 lines with the subscriber load shared across the group.

This is in marked contrast to the usual DSL approach, where each subscriber DSL modem is connected to a dedicated port on a DSLAM on a one-to-one basis. The Celite DSL headend functions much like the cable modem termination system (CMTS) in a cable system: it provides a set of downstream and upstream VDSL modems used in common by a group of subscriber modems on a one-to-many basis. The current models of the DSL headend can be equipped with 2 or 4 VDSL modems, each providing 10 Mbps downstream and 1.8 Mbps upstream and designed to support 108 subscriber lines over a distance of 6,000 feet (1,800 meters).

Like a cable system, the LEC bears a front-end cost to install the DSL headend and pre-provision the cross-connections to the subscriber lines - and then reaps the benefit in reduced time and cost for each incremental customer installation. Tim said that the cost to pre-provision a neighborhood would run about $30 per household, including installation, based on 400 homes per cross-connect cabinet.

Celite says its solution is much more cost-effective than traditional DSL for mass-market penetration. It claims a cost cross-over at a 10% take rate, and half the cost per subscriber at 20%.

Tim told us that the system is "out of the lab" and that Celite is in discussion "with every RBOC, IOC and PT&T to get into a lab trial". He says Celite is talking with several major chip vendors to bring the deployment cost down.

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