Speeding the Last Mile

FRAMINGHAM (05/01/2000) - Widespread broadband access is becoming a reality, but it's the last-mile products and services of the future that customers will find most intriguing, industry experts say.

Vendors behind cable modems, digital subscriber line (DSL) technology and fixed wireless services are scrambling to boost the speeds of their technologies and extend services to more-remote business sites. Their strategies include:

- Lengthening the reach and boosting the bandwidth of DSL technology.

- Better managing the limited bandwidth available on cable access loops.

- Bouncing wireless signals off fixed objects so it is easier to lay out wireless networks.

In addition, vendors are tuning up their access networks to provide the service-level guarantees that corporations demand for high-performance virtual private networks and e-commerce. To support these services, providers are looking to deploy equipment that imposes priorities on their access lines.

"You need a gadget between the access network and the service core that creates explicit service grades," says Tom Nolle, president of CIMI Corp., a technology assessment firm in Voorhees, New Jersey.

These devices will guarantee customers the level of service they need for the applications they run, and at the same time make carrier networks more efficient, keeping down costs.

Broadband devices

The equipment will come in many forms. For example, start-up Quarry Technologies will announce this month a router designed to inspect packets down to the application layer. The gear will enable service providers to offer quality guarantees for specific applications, as opposed to a single quality for all traffic on a given access link.

The Quarry gear, as yet unnamed, can sit behind any broadband access network.

Another start-up, RiverDelta Networks, is developing a broadband router specifically for traffic running over cable nets. The Broadband Services Router (BSR) 64000 will manage customer traffic as it comes off cable loops where bandwidth is limited. Because cable capacity is shared, people who use high-bandwidth applications can drag down the access speeds of everyone else on the same loop.

BSR 64000 will monitor traffic on service provider networks, and allow customers to send and receive traffic in accordance with the service quality they have signed up for, the company says. The router is being built to DOCSIS requirements, which describe how to ensure quality of service (QoS) within cable access networks.

RiverDelta's router translates DOCSIS QoS levels to the schemes that are used in backbone networks to speed traffic such as Diff-Serv, Multi-protocol Label Switching and service qualities defined by ATM. These DOCSIS QoS features are expected to be included in customer cable modems later this year. RiverDelta's gear will also be customized later to manage wireless access networks.

The RiverDelta router is being designed with an eye toward the open cable access movement, an effort being pushed community by community that could change the face of cable services.

Under open access, the owners of cable networks will be forced to lease capacity to competitors so they can offer competing services. Backers say such competition will drive down prices and accelerate deployment of new services.

Cable network owners say it would dampen plans to upgrade their networks to support cable modems.

Should open access come about, the BSR 64000 could be partitioned so different Internet service providers can offer services over the same cable network.

These ISPs will be able to manage bandwidth for their customers, while being restricted from encroaching on bandwidth designated to other carriers, RiverDelta says.

Equipment makers are pushing similar service-quality technology into DSL networks. Last week, for example, Alcatel announced ATM Subscriber Access Multiplexer, which supports multiple service qualities based on ATM. These boxes can work with various flavors of DSL, including asymmetric DSL, G.lite DSL, and two-wire, high-bit-rate DSL (HDSL2). The box also supports ATM voice channels over DSL lines.

CrossKeys, a maker of network management software for service providers, last week introduced Dyband, software that can manage cable modem, DSL and fixed wireless traffic to deliver separate classes of service. Dyband will smoothly throttle traffic during congestion, so customers don't suffer broken connections or dramatic dips in performance, CrossKeys says.

Wireless options

Wireless providers are struggling with similar issues. Nortel is adding new technology to its Reunion fixed wireless gear so it can provide dedicated links for high-priority traffic, but also shared connections for customers who require a lower service quality.

The company already supports frequency division multiple access (FDMA) technology, which is suited to dedicating frequencies for use by a single customer. But it is also adding time division multiple access (TDMA) technology to its products. TDMA will allow wireless service providers to share access bandwidth among customers for traffic that is not as time-sensitive, such as e-mail.

Customers that need guaranteed performance could buy service based on FDMA, and those with less-stringent demands could buy a service based on TDMA, says John Skoro, marketing director for Nortel's broadband wireless group. TDMA will allow carriers to use available wireless bandwidth more efficiently, Skoro says.

Meanwhile, wireless equipment makers are still shopping around for a method of ensuring absolute QoS. Many LMDS vendors use ATM, says Jim Lawrence, program director at Stratecast Partners.

Other vendors are considering tapping into IP or cable's DOCSIS standard for their QoS schemes. The best QoS mechanism for wireless is not likely to be determined for a while, Lawrence says.

Wireless vendors also will develop point-to-multipoint equipment that communicates with several users via a single receiver, rather than point-to-point, which requires a separate receiver for each customer. Service provider Teligent is well along in its deployment, and WinStar and Nextlink are rolling it out now.

MCI is said to be testing prototype point-to-multipoint gear made by Cisco. It is not clear when that equipment will be available. Cisco bought fixed wireless expertise last year with its purchase of Clarity.

Overcoming hurdles

While managing the flood of broadband customer traffic is a top priority for vendors, they are also trying to overcome shortcomings of the access technologies themselves.

For instance, wireless vendors are close to beating a restriction that requires a clear line of sight between transmitters and receivers. They have figured out a way to bounce signals off fixed objects, such as buildings and trees, and still get an intelligible signal. Products that do this are not on the market yet.

But Cisco is using the technology, called vector orthogonal frequency division multiplexing (VOFDM), which came along as part of the Clarity deal. VOFDM delivers two-way data, voice and video communications over the air at high speeds. Texas Instruments and Samsung have announced they also plan to support VOFDM.

On the DSL front, vendors are pushing to extend the reach of the technology to more customers. DSL comes in many flavors, most of which slow down as the length of the phone line increases. Depending on the flavor, most DSL services peter out somewhere between 12,000 and 24,000 feet.

Equipment makers and service providers are ready to pounce on a promising new variety called symmetric high-bit-rate DSL (SHDSL). It is a variant of HDSL2, which is locked in to supporting 1.5M bit/sec downloads and uploads at up to 12,000 feet.

SHDSL is unfettered from having to provide 1.5M bit/sec, and can support varying degrees of high-speed service depending on the distance. It does this without disrupting services running on nearby wires in phone company cables.

Vendors are also starting to boost the speed of the DSL flavor that requires no service technician visit to customer homes. That type of DSL, known as G.Lite, is being pushed from 1.5M bit/sec downloads to 3M bit/sec downloads by Copper Mountain, which makes carrier gear. Copper Mountain says customer G.Lite modems made by 3Com, Efficient Networks and Cayman Systems can handle the extra speed.

The refinement of the technologies will continue, but the ingenuity of service providers and their ability to give customers what they want will determine the success or failure of broadband in the last mile, says Ray Keneipp, an analyst with Burton Group.

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More about 3Com Australia3M AustraliaAlcatel-LucentBurton GroupCayman SystemsCIMIEfficient NetworksMCINextLinkOpen AccessQuarry TechnologiesRiverDelta NetworksSamsungSECTeligentTexas Instruments AustraliaWireless Group

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