BWA vendors work toward standards, commercial deployments

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The enthusiasm surrounding the emerging broadband wireless access industry is creating an opportunity for a variety of new and established equipment vendors hoping to cash in on what is expected to be a lucrative market.

Vendors are scrambling to get systems ready for BWA deployments. Yet, while numerous trials are under way, relatively few commercial systems have been deployed.

Operators appear to be taking a conservative approach to deploying systems, weighing the merits of the available technologies before making any commitments.

The challenge

BWA vendors face practical challenges, including disparate frequency allocations around the world that could result in higher prices and potential signal degradation caused by rainfall and foliage.

However, the biggest challenge BWA vendors face is creating a solution that effectively handles traffic that is becoming increasingly data-oriented. Unlike voice traffic, which is symmetrical and predictable, data traffic tends to be highly asymmetrical and bursty. With data traffic, for instance, a customer might need a big chunk of downlink to access a Web page but only require a small chunk of uplink for navigating the Web. The situation would reverse if the customer sent a large document.

BWA technologies must be flexible enough to deal with data’s intricacies while making efficient and cost-effective use of the available spectrum.

Religious wars

BWA equipment vendors have separated themselves into two basic camps: those that support an air interface based on Frequency Division Duplexing technology and those that support Time Division Duplexing technology. The two groups are waging a sometimes-bitter battle that is akin to the early religious wars that characterized the debate over Code Division Multiple Access and Time Division Multiple Access technologies in mobile systems.

The established model is FDD, which divides the available spectrum into separate channels-one for transmitting traffic and one for receiving traffic, with a guard band in between to protect against interference. FDD vendors, such as Newbridge Networks and Netro Corp., appear to have a head start in the market because the technology has been used for years and is proven.

Newbridge, which is being acquired by Alcatel, has announced several contracts with BWA operators. Most recently, the company agreed to supply equipment valued at $17 million to Hong Kong’s SmarTone. Newbridge also recently signed an agreement to supply a nationwide BWA system, including technology, financing and professional services, for BT Belgium.

In total, Newbridge said it has shipped more than 500 broadband wireless base station sectors to more than 60 customers.

Netro also has announced several deployments, including eight commercial pilot installations in Argentina, the United Kingdom, Spain, Peru, two in the Middle East and two in Germany. In addition, the company last week announced it has begun shipping an initial system for customer trials of its AirStar product for the 28 GHz local multipoint distribution services band in the United States.

TDD, on the other hand, is a newer technology, backed by tenacious startups Ensemble Communications Inc. and Wavtrace Inc. The technology allows traffic to flow in either direction on the same channel, but in different time slots. TDD proponents compare their technology to a highway on which traffic moves in both directions with the median moving back and forth in near real-time, allowing large amounts of traffic to get through in either direction.

TDD technology has been used on a limited basis, primarily in Japan’s Personal Handyphone System and Europe’s Digital European Cordless Telecommunication system, but it has yet to be commercially deployed in a BWA system.

Wavtrace, which has a strategic alliance with Harris Corp., has trial deployments operating with BWA providers Formus Communications Inc. and Nextlink Communications Inc.

Ensemble in December secured $25 million in financing, which it plans to use to commercially launch its Fiberless BWA system during the second quarter.

Standards

The TDD vs. FDD debate is spilling over into the year-old standardization process taking place through IEEE’s 802.16 working group. Launched in April 1999, the 802.16 group is focused on standardization of fixed BWA systems in an effort to bring down costs and promote widespread adoption of the technology.

“We have two existing projects and a third in development,” said Roger Marks, chairman of the 802.16 working group, which grew out of the National Wireless Electronic Systems Testbed. N-WEST, which also is led by Marks, is a measurements and standards resource for the BWA industry.

“I think we’re on a faster track than any other comparable standard,” said Marks.

The first project, called 802.16.1 is a standard for a BWA air interface that covers frequencies between 10 GHz and 66 GHz, including the LMDS band in the United States, said Marks. The group is considering proposals covering the physical and medium access control air interface layers.

Marks said the group received considerable response to requests for proposals late last year. The group received 20 physical layer proposals and 15 MAC proposals in all. Since then, said Marks, the group has voluntarily consolidated the proposals into two for each layer.

One set of proposals is associated with the FDD position and is supported in the standards group by companies including Newbridge, Nortel Networks and SpectraPoint Wireless L.L.C. The other set of proposals is based around Ensemble’s system architecture, although the company notes the proposal is duplex-independent, and is supported in the standards group by Nokia and BreezeCom.

The group is scheduled to make a final decision during a May meeting. Whichever proposal the group chooses will become the foundation of the standard, which Marks said could be drafted by the end of the year.

Industry observers say they aren’t sure what the result of the standardization effort will be. However, some indicated it is possible and even likely both proposals will be deemed acceptable and the ultimate shakeout will occur in the marketplace.

The second project is a recommended practice for coexistence among systems, which is being developed under the 802.16.2 tag. The initiative is a document providing guidelines operators and vendors can use to ensure that one operator’s BWA deployment won’t interfere with another operator’s deployment.

Under the group’s current development plan, the coexistence project is scheduled to be completed sometime this summer.

The 802.16 group also is beginning work on a third project-a BWA air interface for frequencies below 10 GHz, which includes the Multichannel Multipoint Distribution Service spectrum.

The standard will be designed to complement the work of 802.16.1.

Meanwhile, standardization efforts are under way elsewhere around the world.

The European Telecommunications Standards Institute is studying the issue via its Broadband Radio Access Networks group. ETSI BRAN and the 802.16 group are working together on aspects of BWA technology standardization. In addition, the Japanese standards group ARIB also is working with the 802.16 group.

“It’s a very cooperative situation,” said Marks. “It’s quite the opposite of the experience we’ve seen with other standards. There has been a lot of acrimony in other standards efforts.”

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