DSL Prime: VDSL2

VDSL2 is delivering high speeds, but in some cases it's less than the hype suggested.

by Dave Burstein of DSL Prime and Future of TV [May 5, 2005]

50 Million Sockets for VDSL2 Shout "Test Now"
"We are ready to start. If someone wants to bring a board to our lab, we'd welcome them." Rajesh Vashist, CEO of Ikanos, knows the sales potential of his first to market DMT VDSL chips, already designed in at crucial customers. But the vast majority of deployments currently scheduled are for ADSL2+, which will cover almost all of France in the next year. BellSouth and Bell Canada also plan wide ADSL2+ installs, using bonding where necessary for greater speed. They are in a "show me" stage, ready to switch over to VDSL2 when it's proven, affordable and interoperable.

So Vashist is supporting long time standards expert Ed Eckert in a plan to have a plugfest test document ready ASAP, with results likely for the next DSL Forum meeting in September, following the ITU-T in May. Ikanos intends to "lead the charge" and work so that everything is "done well and quickly." He'll strongly support the DSL Forum and UNH.

I asked Vashist how he would respond if another chipmaker called and wanted to begin preliminary testing. Three have told me they are ready, although they haven't formally announced the chips. Vashist pointed out Ikanos had already proven interoperability with ST in an earlier VDSL configuration. "Tell them to call me, and we'll find a way to speed things up. The industry will gain, and it will be good for Ikanos as well."

"VDSL2 is the last chance to get things right," Vashist believes. "VDSL2 will be clean and interoperable. It will also have better reporting and management tools crucial to carrier OPEX."

Say "VDSL2", Think "ADSL3"
Low profile successor to ADSL2+, somewhat improved
There are darn good reasons to update ADSL2+ standards. Telus' Ibrahim Gideon wants better diagnostics. So do the Chinese. SBC wants an extra few megabytes for video, so they don't send an HD signal inferior to cable. Europe in particular needs the ADSL2+ interoperability problem solved, because regulators require allowing consumers a choice of modems to buy. So nearly everyone hopes ITU comes to a decision at the coming meeting.

Many will be confused with the announcement (as I initially was), because most "VDSL2" chips will fit into networks and serve customers in the same way ADSL does—downstream, passive users—and not match the speeds VDSL reached three years ago. They will be ideal upgrades for ADSL2 deployments, and the natural cycle will be to substitute low profile, 8 MHz "VDSL2" chips for ADSL2 as soon as the price and reliability are right. "Low profile" chips are designed to deliver 10 to 25 Mbps paid services "as far as possible" with some people expecting that to go 2,500 feet and others confident of 4,000 feet or more. DSM will add to that.

VDSL2 will also have a higher speed, 30 MHz 100 Mbps version, with 30+ Mbps upstream, such as Ikanos is shipping today. That's what most people expect from "V"—very high speed. Speeds like that are at 100 and 300 meters, and are represented in a "high profile" part of the standard, initially at the request of the Japanese. Those speeds make a profound difference in video download times and ability to match competition, compared to which the "low profile" is essentially a maintenance upgrade.

The confusing name comes from the politics of the committee, which took precedence over the common usage of "V" for very high speed. The new proposal will probably use a line code developed initially for VDSL, but that was resisted by several chipmakers who wanted to continue using ADSL codes. The result is a standard with two parts (profiles), but calling one VDSL2 and the other ADSL3 might have affected the line code argument. Everything was called "VDSL2", even chips not by coming standards very fast. Organizing standards committees requires the skills of Solomon, including frequent compromises like this one.

BSNL Saying "We're Not Ready" to 125,000
3 out of 4 customers disappointed
National telco BSNL is requesting bids on 5 million DSL lines, but operational problems are slowing the ramp and disappointing customers. Indranil Chakraborty in the Financial Express cites "lack of motivation among its ground staff to quickly lay the network and the delay in replacing the old copper wire" as problems the company is working to solve. The problems in India remind me of five years back in the U.S., where the telcos, especially Verizon, struggled painfully to train staff and develop procedures. BSNL still hopes to reach a million homes this year, out of 40 million served by BSNL landlines. They plan to double investment to $4 billion, with major growth in cell phones also planned.

Copyright 2005 Dave Burstein.
The DSL Prime Newsletter is reprinted with permission.

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