In the competitive cable modem market, chipmakers are differentiating themselves with proprietary technologies that coexist with DOCSIS

Vendors that sell cable modems aren't the only folks who are feeling the pain of competition in the highly competitive field of broadband.

The chipmakers are waging their own wars on the DOCSIS battlefield, hoping to gain market share and design wins. DOCSIS certainly has played a significant role in establishing a stout sector of cable modem makers, but those same specs can also make it more difficult for them to stand apart from their rivals. If everyone has the same technical blueprint, it's especially challenging to raise the bar.

Because the need for chipmakers to differentiate themselves has never been greater, many have started to inject modems (and in some cases, cable modem termination systems) with some high-octane additives designed to make high-speed data services really scream. And they're doing this without violating sacred DOCSIS specifications.


Texas Instruments Inc. has made the loudest roar in this area in recent months with TurboDOX, an acceleration software package that lives inside the modem and makes cable's upstream much more efficient.

Cohabitating with DOCSIS, TI's technology doesn't eat up much Flash or SDRAM, but lives comfortably off five percent of the total image size for the host processor. TurboDOX's main mechanism prioritizes and combines TCP (Transfer Control Protocol) acknowledgements in order to utilize upstream bandwidth more efficiently.

Depending on how the network is provisioned and the type of user traffic traversing the network, TurboDOX can improve performance in the range of three-to-10 times, TI claims. And it may be even better than that. "There are certain scenarios for 20 times," says Dennis Rauschmayer, TI's director of product marketing. "We saw 22X in one scenario."

Different than some bandwidth-efficiency methods, TurboDOX need only be present in the CPE. "There's no element necessary at the CMTS," Rauschmayer explains.

It's up to the vendor whether the equipment ships with TurboDOX switched on or off, but operators can also turn it on or off via special configuration files, which are not accessible by consumers.

TI has touted TurboDOX for years, but not until recently has it become "real," at least in relation to DOCSIS certifications and production-readiness. CableLabs awarded certification to a TurboDOX-enabled reference design following certification wave 24. In wave 25, models embedded with TI's technology from Hitron, Motorola Broadband, NetGear, SMC Networks and Toshiba got the DOCSIS greenlight from CableLabs.

There is an incremental cost for TurboDOX–a "small percentage" of the overall cost of the cable modem. "We're talking something well south of a dollar," Rauschmayer says.

But that hasn't slowed adoption of it by cable modem vendors. TurboDOX "is certainly helping us in the MSO world," says Christopher Boring, marketing communications manager for Toshiba, which is shipping several modems that incorporate the technology.

SMC Networks, a self-described "underdog in cable," is also hoping to make some waves with TurboDOX, which is available in its Model 8013 WG (wireless gateway).

"We moved to TI [silicon] for strategic reasons," says Kelaine Hamilton, product line manager for SMC's broadband business unit. "We've heard from MSOs that TurboDOX is compelling and important for MSOs [as they] bring a more robust product to their customers."


Broadcom Corp.'s approach to dilating broadband is a bit different than TI's, but the name of the technology that does it, "Propane," would probably make Hank Hill proud.

Broadcom added Propane to its roster in the heady days of early 2000 after snapping up start-up Digital Furnace for $136 million.

Propane, a form of header suppression, examines redundant elements in voice and data packets. Information that is suppressed is not transmitted over the broadband network. Propane, unlike TurboDOX, must be present in both the CPE and at the CMTS for it to work.

The upside, though, is that it's optimized to handle both data and voice packets. Propane focuses on suppressing headers and eliminating saturation in the return path. TCP, explains Ernie Bahm, director of marketing for Broadcom's headend products division, sends packets in the downstream. The modem on the other end detects it, and the protocol sends an acknowledgement packet in the reverse path.

"If I'm struggling in the reverse path for an acknowledgement packet, my downstream is waiting as well. They're not independent at all," Bahm says. The result is a more efficient upstream path (up to a factor of three, depending on traffic patterns), with a by-product improvement in the downstream.

Today, Propane is a standard feature in all of Broadcom's CMTS and cable modem chipsets, Bahm says. Every Broadcom cable modem can support Propane. Even chipsets that weren't shipped with it installed can support it via a software-based upgrade.

Bahm acknowledges, though, that adding Propane software to the CMTS is more problematic because the technology has to touch every packet. "But it absolutely could be done," Bahm says.

Com21 already has the Propane component turned on and is deploying it in its CMTSs. Others, such as Arris and ADC, have announced intentions to support Propane in some of their respective headend equipment.

Propane isn't the only trick Broadcom has up its sleeve.

Broadcom has incorporated into its new "TurboQAM" CMTS chipset (a combo of the BCM 3214 QAMLink MAC, BCM3140 QAMLink Dual

A-TDMA/S-CDMA burst receiver and BCM3040 QAMLink modulator) the ability to handle broadband line rates of 100 Mbps downstream/40 Mbps upstream. DOCSIS 2.0 specs, in comparison, support 40 Mbps downstream/30 Mbps upstream. Broadcom's DOCSIS 2.0-based modulator chip supports modulation formats up to 1024 QAM.

Not just a two-horse race

TI and Broadcom aren't the only chipmakers that are offering or working on technologies that go above and beyond DOCSIS specs. Conexant Systems, for one, is also working on a TCP acceleration layer and is currently applying for some patents based on the technology.

What Conexant is dabbling in "could be added to DSL or cable modems," says Al Servati, director of Conexant's cable modem business. "It's ready for deployment, but you just don't add features because you can sell it to the end customer. You need MSO input to see if they can benefit from that feature and determine the cost of ownership to that feature."

Imedia Semiconductor, a Terayon Communication Systems spin-off, is also working on new features and capabilities that ride on top of DOCSIS 2.0.

Details of those efforts and a timeframe for their release are still to be determined. "But it's along the lines of what [Imedia's] competition is doing," assures a Terayon spokesman.


A 1024 QAM equivalent?

Although most cable modem silicon makers are focusing most of their energy on dilating the upstream, fabless semiconductor startup Broadband Physics Inc. is setting its sights on morphing a 30 Mbps pipe to one that spits out packets at 180 Mbps-plus.

To do that, the company is employing Sub-band Division Multiplexing (SDM), a modulation technique that turns the frequency spectrum into independent sub-bands.

"It's equivalent to 1024 QAM, with an option to go to an equivalent of 4096 QAM, if noise conditions permit," says company CEO Mark Laubach, a former Com21 co-founder and CTO. The difference is that Broadband Physics' approach doesn't require too many network alterations.

"Architecturally, it fits in the same spot as the current modulators and demodulators," he says. "There's no change to any architecture. What we provide is fatter pipes."

But the technology would have to live on both sides of the cable network—at the modulator at the headend and in the demodulators in the set-top or cable modem. Broadband Physics aims to supply both the modulators and demodulators.

Laubach knows, though, that he will need plenty of support and industry buy-in for the technology of Broadband Physics to really take off. "In order to make it successful for the cable operators and their customers, it has to go to standard and have multiple vendors as quickly as possible," Laubach says. "We're committed to do that."

Although Laubach wasn't willing to discuss specific vendors the company is already talking to, he is optimistic that Broadband Physics will be ready for lab and technical trials by late September.

"Small companies don't make things happen on their own even though they have a very good thing," Laubach says. "You've got to get to the point where people can evaluate it and throw stones at it."