DSL Prime: DSM Doubles Speeds

This is truly nifty. Dynamic Spectrum Management really can double DSL speeds.

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

U.S. Public Television "should make sure their programming better reflected the Republican mandate."
—Kenneth Tomlinson, Bush's CPB Chairman (NYT)

I don't believe the government should control what I watch on TV, nor should Brian Roberts, Ivan Seidenberg, or Ed Whitacre. That's why I'm going to ask SBC's Dorothy Attwood Wednesday how Lightspeed will deliver their promise to Mike Powell, "SBC does not plan to give meaningful preference (in terms of bandwidth allocation) to any particular video service or video content provider." Microsoft IP TV, announced for Lightspeed, will break that commitment. Even with sufficient "up to" DSL bandwidth, the QOS design for SBC's chosen video will hog the bandwidth that may be required for live TV over the internet. So will the refusal of a telco to peer with video programmers who deliver to the edge of the carrier's network.

The speed that video will require—especially upstream when a consumer creates and shares—needs even more performance than most ADSL networks offer. Aktino is the first to document dramatic performance improvements with DSM/MIMO in a shipping product. Similar work is underway at three telcos for (more modest) speedup of consumer DSL as well, but none is publicly disclosed. Ikanos' diplomatic offer to do what it takes to test and improve VDSL2 is another important step to the speeds needed.

New advertiser Zoomlink/Global Village has an offer to bundle VOIP service with their modems that's very attractive financially for telcos and ISP. Do check them out.

Wish I could be at the always useful DSL Forum meeting in Budapest next week, and the ITU-T in Geneva the week after. I'll have to sell some more ads to support my travel budget. This week, a quick trip to DC for Pulver's policy event—come and cheer on free speech and the open internet.

Beyond simple bonding: Aktino DSM doubling speeds
10 to 50 Mbps over bonded copper
Aktino is now shipping an 8 to 12 port bonded system that is proving in the field the lab results of John Cioffi at Stanford. "Captain Mimo" Mikhail Tsatsanis while at Voyan developed the initial chip design, and industry veterans including Ben Itri and David Kimble have developed a small unit, now shipping, that connects up to 12 pair to deliver dozens of megabytes with excellent reach. The AK3000, under $10,000 for both ends, is a high-performance way to deliver speed where it's too expensive to run fiber. Yossi Saad of Actelis confirms from their similar work that DSM and MIMO can significantly improve performance past the unitary gains of simply bonding pair. Actelis, which recently raised another $20 million, is delivering gear to several dozen customers.

One small telco, according to Aktino, is in production delivering 45 megabits 15,000 feet over 14 pair of copper. It took only hours to install.

Dynamic Spectrum Management, MIMO applied to DSL
DSL performance is limited by noise, which is profoundly affected by the amount of power used for the signal. Higher speeds can be achieved by reducing effective noise (echo cancellation), reducing power of adjacent services (Cioffi's "politeness"), and compensating for the actual noise in the binder by measuring several lines. Because "everyone knows" MIMO is improving wireless performance, people are ready to accept that similar techniques will make a major difference in DSL. The most extraordinary improvements come when interference is produced by remote terminal line merging in a binder with lines from the central office, which requires DSM adjustments to avoid disaster.

Both Aktino and Actelis tell me they are generally getting 50+ percent increases in performance when as many as a dozen pair are coordinated, and that the advantage over simple bonding increases as more wires are included. The performance gains on when just two or three pair are joined is less dramatic, raising questions about how this will be utilized for consumer service. Hamid Lalani has interesting speculation about how their achievements will reach the mass, more likely achieved through licensing, not Aktino built equipment. Cioffi has proposed several effective methods of applying these ideas to actual networks. He's convinced DSM will allow 20 to 25 Mbps speeds up to 6,000 feet, although that may require more processing power than practical in today's chips.

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

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