Two digital access technologies, along with variations of each, of course, are fighting it out for dominance in a new wireless market. Proponents for each one are touting why and how their technology is best for the frequencies that were auctioned off by the FCC. One is an older, already tested technology; the other a newer concept that hasn't been proved commercially yet.

The FCC has left it up to the market to determine which technology is used, and proponents of each are busy campaigning to explain how and why their technology is best for the market.

But wait a minute. It's not 1995, and the market is not PCS. It's 2000 this time, and it's fixed broadband wireless. Although some of the letters in the technologies' acronyms are the same -- T and D namely -- it's an entirely new marketplace with its own unique issues that will determine which, if any, technology gains the most market share. Mobility or the lack thereof is the defining factor on a number of issues that separate how the mobile digital market developed and how the newer fixed digital market will evolve.

WEALTH OF OPPORTUNITIES A $7.4 billion market for services. The possibility of $3.4 billion in revenues.

Sound like a market you'd like to get into? Well, according to International Data Corp. (IDC) and The Strategis Group, respectively, that's what the fixed broadband wireless market will be all about in 2003.

Evidence of its growth already is surfacing. To ring in the new year, Winstar, a fixed wireless provider in more than 70 worldwide markets, announced a deal with the Port Authority of New York and New Jersey. The carrier will provide its communications network to about 11 million square feet of office space at the World Trade Center Complex in New York City.

Billions of dollars are up for grabs in the fixed broadband wireless market, and it is clear more than one technology will be there to divvy it up. What is unclear is whether one technology will dominate the marketplace or whether more than one technology will divide up the shares equally.

LET'S GET TO THE TECHNOLOGIES What would a wireless technology be without its snappy acronym? The fixed market won't let you down. The more tried-and-true technology, which already has been deployed in markets across the United States, in Canada and elsewhere, is called FDD, or frequency division duplexing. This way of dividing bandwidth has been used at other frequencies and has been picked up by LMDS and other fixed providers because it has been proved to work.

In an FDD system, two antennas, each with its own frequency, are used at every site: one for solely handling transmitting signals; the other for receiving. FDD systems have been implemented in the wireline world and some vendors such as Newbridge have taken what was created for that sphere and adapted it for wireless use.

The newer technology, which technically isn't necessarily new but is being developed for this application, is TDD, or time division duplexing. It uses one antenna that divides its time between the transmitting and receiving of signals. It has been used in DECT systems in Europe as well as Japan's personal handyphone systems.

As with the GSM/TDMA and CDMA debate in the PCS and digital cellular markets, claims of each technology being more cost efficient and spectrally efficient are rampant. As one of the main differences to the digital mobile field, fixed wireless systems are what the name implies -- fixed -- and that means differences in how the market develops. Although, as with mobile wireless, businesses are the first targets of fixed wireless carriers, contrary to the voice-centric mobile world, fixed wireless' largest market will be data. IDC says the growth of Internet traffic will be a major driver of this.

IDC sees the primary market for broadband wireless traffic in the next five years will be small- and medium-size businesses. In 2003, they will account for 70% of service revenue. In addition, The Strategis Group reports that by 2003, broadband wireless networks will service at least 34% of U.S. households and 45% of U.S. businesses.

Being data-centric, traffic on the network looks different. TDD vendors tout the ability of the technology to better handle the asynchronous demand of uplinking and downlinking of information on the mostly data networks as one of its biggest advantages. They explain that TDD can allocate bandwidth on an as-needed basis, changing the make up of the traffic flow as demand warrants it. For example, if, at one moment, a user downloads a large data file, as much bandwidth as is needed and is available can be allocated to the transfer. Then, at the next moment, if a file is being uploaded, that same bandwidth can be allocated to that transfer. FDD technology, because of its division of frequencies for sending and receiving information, has a more fixed allocation of bandwidth in each direction, and therefore, TDD proponents say, it isn't as spectrally efficient.

LMDS carrier Teligent is online in 36 markets delivering service to its target market of small- to medium-size businesses. Hamid Akhavan, Teligent CTO, said the asynchronous assumption doesn't seem to be as true for businesses as it may be for residential applications.

He said it depends on the type of business the customer is involved in. For example, a small e-commerce company will need to do a lot of uplinking, rather than downlinking, which a home user browsing the Internet would need. That doesn't mean the issue is invalid, however.

"What is the mix today, will not be the mix tomorrow," Akhavan said. "We need to look ahead at the technologies."

As for cost issues, vendors on each side can provide a variety of outlines to show their technology is more cost-efficient. It is easiest to calculate if initial equipment and software costs compare by determining how much equipment will be needed for an installation, and adding up the prices. This varies for each installation, not to mention each vendor's equipment, because of factors unique to each one, such as coverage area, number of customers and terrain of the area. But those are not the only costs that need to be considered. Other issues to consider when determining the price of a system are the cost and ease of deployment and maintenance, not just the initial equipment investment, Akhavan said.

INTERFERENCE ISSUES When working in the world of radio waves, which see no arbitrary boundaries, and geographic licensing, interference issues always will crop up. In the PCS atmosphere, the issue was most evident when carriers were working with incumbent licensees on the spectrum to prevent interference. As co-locating of equipment on rooftops and towers has become more prevalent in cellular and PCS networks, again interference issues come up because of the proximity of the equipment at various frequencies.

For providers in the fixed sphere, interference also is an issue. How large of an issue, however, depends on whom you talk to. As with all wireless technologies working within geographic boundaries, the potential for interference is there in a couple of scenarios. At the fringes of licensed BTAs, the potential is there for interference from a carrier in one BTA and on a particular frequency to interfere with a carrier in the adjacent BTA on the same frequency. Within a BTA, carriers with adjacent frequencies can cause interference if one carrier's signal leaks into the adjacent carrier's frequencies.

Erik Boch, executive vice president of wireless systems for Newbridge Networks, an FDD vendor, sees a large interference problem between TDD and FDD networks. He said the company believes interworking between co-located FDD and TDD systems is not feasible. Also, Boch believes, especially in the fringe areas of BTAs, that interfering signals from a carrier in an adjacent BTA will cause problems.

"Radios in the air don't care about the (geographic) borders," he said.

Striking agreements with neighboring license holders regarding interference is a must, and Boch contends that it is easier to do when each license holder is using the same access technology.

"Carriers have to make arrangements with each other," he said. "Once they've figured out the recipe, it is much easier to do additional ones."

He explained that it is easier to work out these agreements when the same technologies are being used because both sides have the same set of concerns.

TDD vendors, however, play down this problem by saying no matter what technologies are used, there will be interference issues, and they can be worked out.

Thomas Van Overbeek, Wavtrace CEO, a TDD vendor, said, "Without proper planning there is potential for interference whether it's TDD or FDD. I don't believe (interference between access technologies) is an issue. You have to plan; you have to deal with it."

Carlton O'Neal, Ensemble Communications vice president of marketing, an adaptive TDD vendor, said interference is an issue that standards need to address, especially to deal with signals in adjacent frequencies in one geographic area.

"Co-existence should be the top focus of standards," he said.

O'Neal said standards could spell out just how a signal needs to be cut off in order to prevent it from bleeding over into adjacent frequencies.

"If you have reasonable carriers working with technology interference, it will work out," he said. "It's just frequency coordination."

However, he said boundary issues will be big near BTA dividing lines, especially with FDD having one frequency constantly receiving and if the adjacent BTA's carrier at the same frequency is using TDD, which varies its transmitting and receiving.

Again, O'Neal said, more standards will have to be developed to address that issue.

THE ISSUE OF STANDARDS Developing a standard is a top issue in the fixed wireless sphere. Although some companies, such as Ensemble, see it as a way to allow carriers -- and specifically their equipment -- to co-exist, others don't see the need for standards in this fixed wireless space. And others want the standards to be a way of dictating which air interface can be used.

"The whole standards thing is another phony issue," Van Overbeek said. "If you have a mobile network, it is more of an issue. In fixed wireless, you generally have one vendor (in a particular network). Interoperability is not as big of an issue."

Teligent's typical method of setting up a network is in accord with this opinion, Akhavan said. The carrier generally buys the radio equipment for the customer side and the node side of a network from the same vendor, eliminating interoperability issues between vendors' equipment.

Newbridge's Boch said the company is co-chair of the interoperability working group for the IEEE committee developing the 802.16 broadband fixed-wireless standard. He contends a single air interface would make interoperability easier.

Boch also suggested that if the standard further allocated specific spectrum for uplinking and downlinking of signals, interworking becomes still easier.

IS TECHNOLOGY REALLY AN ISSUE? TDD vendors are not quiet about their beliefs that this technology is what the LMDS market needs to advance.

"LMDS has gone nowhere because of the misapplication of technology," said Ensemble's O'Neal.

He said FDD is not the solution for fixed networks; it was just available first, so it is being implemented.

Wavtrace's Van Overbeek sees TDD as the better, more advanced newcomer on the field. He said, "You don't want to be flying a biplane, when everyone else has jets."

However, in the fixed market, carriers have an advantage that their mobile predecessors did not have. Because of the systems' structure -- it is fixed so users won't be roaming around the country -- a carrier does not have to be loyal to one technology to serve its customers.

"We don't have to select one technology as a fixed wireless company," Teligent's Akhavan said. "We don't have to be labeled as one of three types of technology."

This fact bodes well for there being a place for each digital technology; even FDD vendor Newbridge, according to Boch, is looking at all technologies and will develop systems it believes will be the most viable.

Nextlink provides testimony to various technologies earning a part in the future. The largest holder of fixed wireless spectrum in the United States, which covers 95% of the population in the top 30 markets, is field testing broadband fixed wireless equipment from Ericsson, SpectraPoint Wireless, Wavtrace and Digital Microwave in a variety of wireless environments.

"I clearly see all of these technologies in the market," Teligent's Akhavan said. "You can have people argue to no end that one is better than another. They both have places.

"Time will tell to what degree each technology plays out. I don't think any will die."

Teligent's strategy is to deploy the technology that is best for a market, for the applications and the customers, Akhavan said.

A technology debate does not interest customers. As for any communications system, the customers don't care what technology is used as long as it delivers what it is contracted to provide in an efficient, cost-effective manner.

Isn't that what wireless communications is all about? And, isn't that what the industry should deliver?