AT&T VDSL2 bonding trial slips into 2009

AT&T plans to conduct a trial early next year of bonded VDSL2, the company told Telephony last week, after having previously targeted late 2008 (and before that, late 2007) to start deploying the bandwidth-boosting technology.

Over the years, AT&T has repeatedly cited the promise of bonded VDSL2 when asked about the bandwidth limitations of its fiber-to-the-node architecture. The technique effectively combines the bandwidth of multiple copper pairs, treating them as a single line and boosting the capacity of those lines by an amount that depends on their length. But today the company downplays pair-bonding’s role.

“Pair bonding isn't necessary for all customers, nor are things like two [high-definition video] streams or faster Internet tiers dependent on pair bonding,” an AT&T spokesperson said last week. “Rather, we'll use pair bonding where needed as a way to expand our U-verse service area to customers at longer loop lengths. It will allow us to reach a broader customer base.”

Outside AT&T, other industry executives, such as Qwest Communications’ chief technology officer, have seen bonded VDSL2 as “a 2009 thing” for some time. According to several accounts, the gating factor has been the availability of customer premises equipment (CPEs) that supports the technology.

"CPEs that support VDSL2 bonding will become available over the next months and need to go through test before they will actually be commercially deployed,” said a spokesperson for Alcatel-Lucent, whose access gear, deployed by AT&T today, already supports bonding. “We are expecting the first bonded VDSL2 deployments to arrive on the scene towards [the middle] of 2009."

Meanwhile, some industry sources say CPE vendors haven’t moved quickly with these products (Alcatel-Lucent has been calling for this gear since at least 2007) because they don’t see much volume in the business nor much commitment from carriers.

The technology is limited by a few factors, including the challenge inherent in avoiding interference when bonded pairs are housed in the same binder. Perhaps a more pressing limitation, however, is the simple requirement for extra pairs of existing copper, which are not in plentiful supply in AT&T’s network outside the territory of the former BellSouth, where extra pairs were deployed extensively in the 1990s to accomodate dialup and fax services. And even in BellSouth territory, analysts say, AT&T is expected to focus on bonding ADSLx, a technology that is the subject of more activity today than VDSL2.

“Whenever bonding has been discussed, it’s been with ADSL2+,” said Erik Keith, an analyst with Current Analysis.

For example, in October, SureWest Communications launched 10-Mb/s and 6-Mb/s broadband services over a bonded ADSL2+ network in its incumbent territory, reaching more than 37,000 potential customers. One day, SureWest has said, it may even explore offering video services over that network.