WiMAX will sweep the nation, bringing cheap mobile broadband to the masses — at least that's the story. The truth is that Mobile WiMAX's scope is a bit more limited than the hype would suggest. WiMAX may be a revolutionary step in broadband, but according to some vendors, the revolution will be confined to the metropolitan centers of the U.S. The rest of the great American interior may be left with Mobile WiMAX's predecessor, fixed wireless.

The fact is, Mobile WiMAX by definition is a technology meant for very dense environments, said Carlton O'Neal, vice president of marketing for WiMAX vendor Alvarion.

“All of the higher-order features of mobile WiMAX are associated with mobility, while outside of the city the goal is broadband access,” O'Neal said. “The rest of the benefits come from its additional capacity, which you just don't need in a rural area.”

However, the rural case for the first generation of Fixed WiMAX, the broadband wireless technology based on the IEEE 802.16d, or 2004 standard, is an entirely different matter, O'Neal said.

Although many of the big carriers serving major markets are holding out for Mobile WiMAX, based on the 802.16e, or 2005 standard, the rest of America is moving forward with fixed deployments. In fact, Alvarion and other vendors have sold hundreds of Fixed WiMAX and other fixed wireless systems to smaller carriers and Internet service providers throughout North America.

Tom Gruba, senior director of marketing for Motorola, said that the demand for fixed or portable broadband deployments is not only stronger in non-urban areas, but the spectrum situation in those markets is much more conducive to those technologies. Most of the major mobile broadband spectrum, he said, is owned by a few large carriers: Sprint and Clearwire own most of the 2.5 GHz spectrum, and a handful of carriers own spectrum in 2.3 GHz.

Although Mobile WiMAX is possible in the cellular and PCS bands, the same situation applies: Those licenses belong to the Tier 1 carriers and major regional players. That leaves unlicensed spectrum in the 900 MHz, 2.4 GHz and 5.8 GHz bands, ideal for fixed non-line-of-site deployments, but because of interference issues with the orthogonal frequency division multiplexing (OFDM) technology used by Mobile WiMAX, it's not so ideal for mobile broadband, Gruba said.

He noted that the WiMAX Forum hasn't even set a Mobile WiMAX profile for the 5.8 GHz band, the most commonly used unlicensed band for broadband wireless. If the forum does pursue a profile in that frequency, Motorola will certainly investigate a possible product line, Gruba said, but for now, it believes that its proprietary Canopy line of broadband wireless equipment is optimal for any non-urban broadband wireless scenario.

“The question is, will the standards bodies write a spec at 5.8 GHz?” Gruba asked. And if the answer is yes, then the rural carriers have to decide if they want to deal with possible interference issues of an unlicensed Mobile WiMAX deployment.

“Therein lies the conversation the industry needs to have,” Gruba said.

Alvarion's O'Neal, however, added one caveat. It's very likely that Mobile WiMAX will make it to the rural markets, but it will be in a form very similar to the fixed wireless deployments of today. A rural carrier or ISP could deploy Mobile WiMAX in a fixed mode, using stand-alone customer premises equipment and upgraded WiMAX base stations. There is no inherent technical advantage in using 802.16e versus 802.16d equipment in a fixed deployment except for a boost in aggregate capacity, but there may be an economic advantage, O'Neal said.

Mobile WiMAX is expected to proliferate much further than Fixed WiMAX and create economies of scale that will drive down the price of mobile gear. Carriers could take advantage of those economies of scales to deploy a cheaper network, O'Neal said.

The rural carriers will have to make that decision very carefully, O'Neal said. Many of them will have significant investments in Fixed WiMAX or a proprietary technology so the cost savings will have to be high for them to justify a network overhaul, he said.

“If you're a carrier in L.A., you have a large margin of error,” O'Neal said. “If you're in Amarillo, Texas, or even a carrier serving a community outside of Amarillo, you're in a very dollar-and-cents market. Those guys are very practical.”