Breaking the 3 Meg Barrier

At this past Spring's FastNet Futures conference in Santa Clara, Calif., one of the more interesting moments came when representatives of both Ikanos and Metalink stood before several dozen fellow broadband executives and demonstrated competing chipsets that could send data through copper at 100 Mb/s downstream and 50 Mb/s upstream. While staged under conditions that weren't exactly real world — Ikanos sent data over 1500 feet of 26 gauge twisted pair while Metalink did the same over 984.25 feet of 26 gauge wire — the event in the convention center ballroom was meant more as a showcase of what will be possible for telcos worldwide in a few years.

Since that time, though, the road map that brings the industry to 100/50 appears to have sped up significantly. Korea Telecom and Japan Telecom, early adopters of any technology that will give them a speed edge over competitors, already are deploying the technology using both Ikanos' and Metalink's chipsets. However, carriers in the U.S., save for the few that are deploying fiber to the premises (FTTP), likely won't be approaching those speeds anytime soon. However, there's increasing evidence that many may be deploying technology that pushes them beyond their current typical DSL offerings that top out at 3 Mb/s or so.

And though users' appetites for raw data bandwidth continues unabated, it's the prospect of offering high-definition television (HDTV) that is pushing carriers to move beyond their current capacity limitations. The biggest question for carriers, though, is whether the latest technology they're installing will have enough capacity to send HDTV over copper.

“As we get more vocal on the TV over IP bit of this, with HD being a clear competitive advantage for wired telcos, bandwidth becomes an issue fairly quickly,” said Jeff Paine, vice president of strategic marketing for UTStarcom. “At some point, you're going to be looking at a 30 meg per second requirement.”

Like most previous technology pushes, numerous competitive forces are having a significant impact on the decision to move beyond the 3 Mb/s threshold. First and foremost is the increased pace of erosion that carriers are seeing in their core voice revenues as a result of aggressive voice-over-IP deployments.

“It used to be people would let you in because they wanted to roll the video; now it's because of the AT&T Call Vantage,” said Kevin Brown, vice president of marketing for Pannaway Technologies.

On a more directly competitive level, cable operators' fast rollout of HDTV is giving some forward-looking telcos a sense of urgency. According to figures released last month by the National Cable & Telecommunications Association, consumers in 177 out of 210 local TV markets now can receive HDTV from their cable operators. What's more, of the 108 million U.S. TV households, 90 million are now passed by a cable system that offers a package of HDTV programming, an increase of more than 28% over the 70 million mark since last December.

No telco has announced the availability of HD in part because there aren't any set-top boxes on the market that can display HD compressed with the Windows Media 9 or MPEG-4 that telcos are expected to use. Additionally, most large telcos are not busy figuring out the mechanics of video with satellite partners.

Perhaps most important — and more expensive to remedy — is the fact that few telcos have deployed access infrastructure capable of carrying HDTV signals.

ADSL where S equals one-half, the dominant residential flavor of DSL typically deployed by independent telcos delivering video service, can run at about 10.5 Mb/s on average loop lengths (see chart). That won't allow for HDTV, but ADSL2+, which is being deployed quickly in the same segment, has been defined to operate at the 24 Mb/s range and can transmit HD with current compression methods. Both MPEG-4 and Windows Media 9 will bring the bandwidth requirement down even further.

“We're running HD over ADSL2+ today not even relying on MPEG-4 or Windows Media 9,” said Kevin Walsh, vice president of marketing for Calix. “We've seen MPEG-4 down in the 9-megabit range, and our expectations is that it will get down to 6 megabit. The bandwidth requirement curve is coming down at a pretty healthy pace.”

Indeed, the amount of bandwidth needed to run standard definition video has come down with better compression techniques.

“Just to run video is in the [4 Mb/s] area,” Brown said. “We've seen excellent video in that range.”

Calix, which counts CenturyTel among its larger customers, has seen a jump lately in the number of carriers wanting to offer HD video in both broadcast and video-on-demand (VOD) formats. In broadcast mode, carriers using ADSL 2+ under good conditions could offer a single stream of HDTV, one standard definition stream and still have enough capacity for high-speed data and voice. In VOD format, where content is static and sits on a server until requested, the amount of capacity required could be cut to as low as 2 Mb/s, Walsh said.

“The discussion is beginning of, do you need to support multiple HD streams simultaneously?” he said. “I think you do, but the question is when.”

Based on the most recent sales figures, that time may be sooner than you think. While HDTV's are still relative expensive at a minimum of $2000, the Consumer Electronics Association reported that 328,838 units were bought in the U.S. during August. That's up 10% from the same period in 2003. Sales also are expected to pick up steam with price drops in the same way that large-screen TVs shot through the roof once they dipped into the sub-$1500 range.

For now, though, ADSL2+ appears capable of fulfilling most telco video needs, even if it includes HDTV.

“The magic number seems to be 20 Mb/s,” said Daniel Marcus, product marketing manager, broadband products for UTStarcom. “Currently, that's what we're moving forward with.”

The ability to bond, where carriers use two pairs of copper to transmit data, in the ADSL2+ specification gives the technology an extra speed boost and is particularly useful in areas where the copper plant might not be in the top condition, according to several vendors.

Ultimately, fiber all way to the home will give carriers the biggest jump in speed and will allow for multiple HD streams. Verizon's initial launch of FTTP in Keller, Texas, includes a data option for heavy users that will deliver speeds of 30 Mb/s downstream. The company has yet to announce its video strategy but should have capacity to burn.

Carriers in that situation, however, are few and far between, and almost no one expects FTTP to become a copper replacement any time soon. In fact, during the past six months, there has been a marked increase in activity around copper-based VDSL and VDSL2, which would seem to indicate that vendors don't believe there will be a critical mass of FTTP deployments for many years.

VDSL has been around for several years and, in fact, was the first copper-based technology to allow telcos into the video world. Both KT and Japan Telecom are deploying systems based on the technology, though most industry watchers don't expect the technology to be a significant player outside of Asia because of the short loop lengths it requires. More damaging to its global prospects, though, is the fact that VDSL only recently was approved as a standard by the ITU, and many system level vendors still view the technology as proprietary.

VDSL2, by contrast, is still in the development stage and appears to have significant participation from all sectors of the industry. System vendors such as Alcatel, Adtran and Calix all have VDSL2 figured into their plans, as do smaller vendors.

“We haven't seen a huge demand for it yet, but the emphasis is on getting the loop lengths shorter,” said Dominic Imbrogno, senior product manager of the access and transmission business unit for Charles Industries. “VDSL2 is on the product road map. It's something we see getting next year.”

When fully developed, VDSL2 is expected to match VDSL in terms of speed, with perhaps slightly better reach. The standard also will allow for bonding copper pairs and may become backward compatible with VDSL, said Peter Chow, chief technology officer of TI's DSL Technology Center.

“There's some push to have a mode in VDSL2 that can talk to VDSL1,” he said. “But I don't really believe that a lot of people will deploy VDSL in volume outside of Korea and Japan.”

TI, which is one of the major ADSL chipset vendors, is pushing its own version of VDSL2 called uni-DSL (UDSL), which would provide 200 Mb/s in aggregate on the downstream and upstream paths. The technology, which is still more of a concept than anything, eventually could disappear if TI gets its way with VDSL2.

“We got a lot of good feedback, and right now we're pushing to get part of the UDSL included as part of the VDSL2 standard,” Chow said, noting that the standard committees editor is a TI employee. “Ideally, we'd like to get everything that is important from UDSL into the VDSL2 standard. That's going better than we had hoped.”

However, the timeframe in which VDSL2 chipsets will be available is forcing the industry to rely on ADSL2+ for the moment.

“We do also see interest in VDSL2,” Walsh said. “I don't when that gets fully baked into chips and handed to us, but it's got to be at least a year before it starts shipping. For now, we're looking at broadcast, a single HD stream, healthy Internet access [3 to 5 Mb/s], plus VoIP and VOD, and it fits nice one ADSL2+ connection at 8000 to 10,000 feet.”

Ultimately, carriers must decide not only what is possible but also what's economically feasible, Walsh said.

“You will reach a point that eventually we'll be able run 100 meg per second over copper with real loop lengths,” Walsh said. “But what will happen is that the economics will start to bump up against fiber.”