Wednesday, February 6, 2008

Stretching copper

When AT&T moved the goalposts back again on its expected deployment of bonded VDSL2, the industry seemed to collectively shake its head in frustration. Yet another delay in the carrier’s fiber-to-the-node initiative. And yet another return to the inconvenient truths about the bandwidth limitations of copper.

“AT&T will need to do something dramatic in order to find the bandwidth to deliver multi-stream high-definition [TV], especially since the cable and satellite competition have expanded their HD channel line-ups and/or VoD libraries substantially,” said Erik Keith, an analyst at Current Analysis. “MPEG-4 will help, but FTTN DSLAMs will not be the best strategy long-term. FTTP is really the best way to go.”

However, a few developments this week are aimed at not giving up on copper so quickly.

Rim Semiconductor is testing a new specification known as Internet Protocol Subscriber Line, or IPSL, that it expects will dramatically improve broadband performance over existing copper. Rim claims its Cupria processor can send traffic down a 26-gauge copper pair at 40 megabits per second over 5,500 feet. The company tested its wares a few months ago on the network of Monroe Telephone, a small telco in Monroe, Oregon not far from Rim’s headquarters in Portland.

John Dillard, Monroe’s president, told me Rim’s creation was “still in the breadbox stage,” but added that the Rim folks seemed to be very pleased with the results of their tests, promising more tests to follow.

Meanwhile, Alcatel-Lucent said this week that it expects to introduce equipment late next year that uses Dynamic Spectrum Management, or DSM, to aid VDSL2 performance by reducing noise in the network. But even that is described by Alcatel as a way to get a few more years of life out of existing copper before the inevitable transition to fiber.

These are only the latest such efforts to stretch copper’s limits. Last year, researchers at Penn State, working with cable vendor Nexans, designed a transmitter and receiver to send data at 100 Gb/s over Cat 7 copper.

Considering the expense of deploying FTTP and the amount of copper wire strewn across the country, it’s no surprise to see vendors focus on squeezing ever more bandwidth out of copper. As I’ve pointed out before, no matter what analysts say about the clear superiority of FTTP, the favorite triple-play access architecture of U.S. carriers continues to be FTTN–and copper the rest of the way.

Ikanos VDSL2 and FTTH Gateway Processors Awarded 2007 Product of the Year

EN-Genius Selects Fusiv(R) Vx180 VDSL2 and Vx170 FTTH Gateway Processors as Best LAN Products

FREMONT, Calif., Feb. 4 /PRNewswire-FirstCall/ -- Ikanos Communications, Inc. , a leading developer and provider of Fiber Fast(TM) broadband solutions, announced today that its Fusiv(R) Vx180 VDSL2 and Vx170 FTTH gateway processors have been awarded "2007 Product of the Year -- Best LAN Product" by EN-Genius Network.
The Vx180 single chip multimode VDSL2 gateway processor and Vx170 FTTH gateway processor are designed to provide the features, performance, security and scalability required to deliver advanced triple play services over broadband pipes. Both solutions offer 2.7 GHz of processing power, integrated Voice over Internet Protocol (VoIP) and security features while supporting best-in-class Quality of Service (QoS) with wire-speed performance. Moreover, the Fusiv Vx180 also integrates Ikanos' industry-leading multimode VDSL2 technology to offer unsurpassed performance and physical layer integration for a triple play residential gateway.
"The Vx180 VDSL2 and Vx170 FTTH gateway processors help customer premises equipment (CPE) manufacturers address the double-edged challenge of providing multi-service capable products that help boost revenue, while keeping equipment costs under control," said Lee H. Goldberg, senior technical editor, EN-Genius Network.
The Vx180 and Vx170 residential gateway processors enable superior support of advanced triple play services through their unique and innovative distributed Accelerated Processor (AP) architecture. Differing from traditional multi-core and multi-thread approaches, Ikanos' powerful AP architecture offers a tremendous amount of processing performance in a small silicon area, while operating at very low power. These Accelerator Processors come equipped with local program and data memory to avoid resource conflicts and carry the entire bridging and routing effort, leaving 500 MHz of processing power available to support other advanced triple play services.
"We are very pleased that the editors at EN-Genius have awarded our high performance Vx180 VDSL2 and Vx170 FTTH gateway processors with their prestigious Product of the Year award," said Piyush Sevalia, Ikanos' vice president of marketing. "EN-Genius' endorsement validates Ikanos' leadership in providing innovative, high performance, integrated residential gateway platforms that enable service providers to launch triple play services more quickly and cost-effectively."
Instituted in 2003, EN-Genius Network's Product of the Year award recognizes data acquisition, audio/video technology, green tech, green-power engineering DSP, wireless connectivity, networking, passives, and low and high power products that best demonstrate strong technical merit, innovative design and exceptional marketability.

A closer look at 40 Mb/s DSL

What’s behind Rim Semiconductor’s recent claims of superfast DSL?

Rim Semiconductor turned some heads in January with a claim that its new chip can send traffic at 40 Mb/s over 5,500 feet of 26-gauge copper wire. The chip, which the company said will be commercially available later this year, promises big jumps in bandwidth for carriers such as AT&T that are trying to cram as much traffic as they can down existing copper lines.

But Rim’s approach is such a departure from currently dominant access technologies that it will have to work hard to establish new industry standards in order to get widespread deployment by major telcos.

Part of Rim’s technology involves changing how upstream and downstream bandwidth is allocated. The company is proposing an alternative to discrete multi-tone (DMT) line-coding, the encoding standard commonly employed in DSL networks including VDSL. Rather than reserve fixed allocations of upstream and downstream bandwidth, as DMT does, Rim’s chip uses time-division duplexing (instead of the frequency-division duplexing used in VDSL2) so that, when needed, downstream traffic can use bandwidth that would otherwise be reserved for upstream traffic, and vice versa. And it uses “rapid bi-directional switching” to transition in milliseconds from upstream and downstream transport.

“DMT’s fixed ratio of downstream and upstream [bandwidth] was absolutely appropriate at the time [it was created], but video has changed it all,” said Brad Ketch, Rim Semiconductor’s chief executive officer. “We feel and have felt that ultimately DMT would come to a point of diminishing returns.”

Redoing DMT is just part of Rim’s approach, said Ketch, a veteran of access vendor Advanced Fibre Communications (now Tellabs). Ketch is careful not to divulge too much about the company (which, despite not having a commercial product, has issued more than 30 press releases in the past two years). According to the firm’s Web site, Rim’s technology “defines” not just the encoding algorithms inside transport processors but also “the signal stream waveform.” Rim attacked rate and reach limitations in several ways, the company says, increasing payloads and decreasing noise and latency. Along the way, it made a few acquisitions to aid the effort, including that of 1020 Technologies and Broadband Distance Systems (a subsidiary of Utek).

The company has also hired Telcordia to, as Ketch put it, “study the impact of this technology in a binder group…to work over our shoulder make sure it makes sense to tier-one telcos.”

Ketch acknowledges that, in order to be useful, Rim’s technology would need to be deployed both in access networks and in customer premises gear, underscoring the need for standardizing the nascent technology.

“As far as the market goes, they’re sailing into the wind,” said Kermit Ross, a consultant with Millenium Marketing. “Given that the phone companies have a mix of [DSL] platforms in their networks as it is and a mix of different suppliers of DSL modems, there’s an awful lot of current flowing against making a thing like this work.”

To develop an industry standard for its technology, dubbed Internet Protocol Subscriber Line (IPSL), Rim has convened a group called the IPSL Special Interest Group, or IPSLSIG. Embarq is one of the few publicly named members of the group, which plans to meet a few times a year (its next meeting, slated for Europe, is being scheduled now, Ketch said).

“We invented IPSL, but we’re committed to making it available to other vendors because we’d like to see the ITU-T bring it in and standardize it,” Ketch said.

“Getting IPSL standardized will be one of the biggest hurdles for Rim Semi as it looks to bring its technology to market,” said Erik Keith, an analyst with Current Analysis.

Rim’s technology also requires IP DSLAMs rather than the legacy model based on ATM, though the majority of DSLAMs deployed today are IP-based..

Rim is currently testing a field-programmable version of its chip in the networks of small telcos such as Oregon’s Monroe Telephone. But with the help of partner eSilicon, Rim expects to introduce a less expensive ASIC version commercially this year.

Ketch imagines Rim’s gear making it possible for carriers to add more high-bandwidth service such as IPTV over existing copper, but he’s less certain about the technology’s potential to bring DSL to areas currently beyond reach. “That’s one application for the technology, but I think there are some question marks about the economics of it,” he said.

Meanwhile, vendors across the industry are working on separate efforts to increase the performance of DSL and copper. Established vendors are fine-tuning technologies such as Dynamic Spectrum Management and VDSL2 pair-bonding (Ketch says IPSL could potentially work in conjunction with both those technologies), while newcomers like Xtendwave and Phylogy promise their own new approaches.

“Since FTTP is prohibitively expensive for most telcos, getting more out of the existing copper access network is their most cost-effective option," Keith said.