WiMAX Bridges the Last Mile in Broadband

Wednesday May 19th 2004 by Steven J. Vaughan-Nichols
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WiMAX is slated to provide high-speed connectivity over distances that dwarf 802.11's effective range. Of course, it also promises to keep things interesting for network administrators just coming to grips with Wi-Fi.

When you want broadband today chances are you're locked to a landline connection with a T1, DSL or cable modem. WiMAX (Worldwide Interoperability for Microwave Access), an evolving standard for point-to-multipoint wireless networking, may change that for the last mile in the same way that Wi-Fi has changed the last one hundred feet of networking.

Microwave broadband is actually a very old technology. Your author has some not-so-fond memories of setting up T-1 (1.54Mbps) microwave connections in the early 80s. Proprietary point to multipoint microwave networks from companies like Alcatel and Siemens have existed for decades. But the technology has also been extremely proprietary and that has limited its popularity. What WiMAX brings to the plate is that it's attempting to standardize the technology.

Now, WiMAX may change that not only for rural areas, but for anyplace where the cost of laying or upgrading landlines to broadband capacity is prohibitively expensive.

Craig Mathias, an analyst for the FarPoint Group, says that WiMAX is the commercialization of the maturing IEEE 802.16 standard. In short, "WiMAX is the marketing arm of 802.16."

802.16 is, according to its charter, "a standard, which specifies the WirelessMAN Air Interface for wireless metropolitan area networks." The standard, which was published on April 8, 2002 is meant to "address the 'first-mile/last-mile' connection in wireless metropolitan area networks (MAN)."

WiMAX is more than just 802.16 though. According to Dean Chang, Director of Product Management for Aperto Networks and WiMAX board member, "it's both a standardization effort between IP over 802.16 and the ETSI High-Performance Radio Metropolitan Area Network (HiperMAN) broadband wireless MAN (WMAN) standards and an industry group devoted to that goal." Thus, "WiMAX compliant equipment will interoperate with both the European HiperMAN and 802.16."

What's driving WiMAX, according to Edward Rerisi, Director of Research for Allied Business Intelligence is that, "From an operator's standpoint, it gives them a standard that will lower the cost of equipment. Today, this is equipment is very expensive now. A common standard should lead to a more competitive, and cheaper, marketplace." The market will grow enough as a result though that "Equipment vendors will be able to sell more equipment, thus leading to more revenue for them." At the same time, "consumers are very thirsty for broadband."

Mathias sees WiMAX as having two drivers: lower cost for fixed-point to fixed-point wireless and interoperability. "In short, the common benefits of standards." But, he adds, "Fixed microwave has been around for more than 50 years, so one possible scenario is that it's not a price sensitive market at all." Still, he thinks that while "Some will embrace it, some will oppose it, and some will play to see if they get a better Return on Investment (ROI), but the handwriting is on the wall, WiMAX will happen."

Continued on Page 2: What's WiMAX, Anyhow?

Continued From Page 1

So what is WiMAX exactly? Unlike the wireless technology standards that most of us know, such as 802.11b or 802.11a, WiMAX covers several different frequency ranges. The base 802.16 standard is for the 10 to 66 GHz range. 802.16a added coverage for the 2 to 11 GHz range. WiMAX, and most commercial interest, covers these lower ranges.

It's more than that though. Chang explains, "Unlike 802.11, when you have one frequency and energy, WiMAX range and performance can vary quite a bit depending on the number of frequency bands supported, the frequency itself—the maximum range of the 2.5Ghz is much longer than 5.8GHz—and the power."

Generally speaking, WiMAX has a range of up to 31 miles, which can be used to provide both campus-level network connectivity and a wireless last-mile approach that can bring high-speed networking and Internet service directly to customers.

In practice, Rerisi expects WiMAX's base stations to cover areas with a radius of ten miles. "It really depends on the number of subscribers. To guarantee high speed to users, since the WiMAX pipe is only so big, and its bandwidth is shared with subscribers, the target is to have no more than 500 subscribers per base station. "

Because the standard has not yet been finalized, Mathias thinks, "Mass deployment is a couple of years away." The WiMAX group, Chang explains, won't even release WiMAX certification tests until late in 2004.

Once it's here though, many broadband users may want it. 802.16 can give users high capacity links on both the uplink and the downlink of up to 75 Mbits per second (Mbps) data-transfer rates on a single channel, compared with 802.11b's theoretical 11 Mbps.

802.16 obtains these speeds in the 2 to 11 GHz range by using Orthogonal Frequency Division Multiplexing (OFDM). OFDM is a spread-spectrum technology that bundles data over narrowband carriers transmitted in parallel at different frequencies.

"In practice," Chang continues, "the channels won't be able to deliver 75Mbps per channel because radio frequency licensing makes the channels narrower than the 802.16 standard allows. Channels can be bonded together to provide higher bandwidths. Thus, for example, six channels can be used to provide an effective bandwidth of 250 to 350 Mbps."

WiMAX may turn out to be more than just a broadband backbone though. Intel, in particular, hopes that WiMAX proponents will complement Wi-Fi. The company plans to create chipsets that can handle both the 802.11 and 802.16 technologies. Laptops with these chipsets would use whichever signal was strongest in a given area.

While Wi-Fi and WiMAX may end up complementing each other, another growing technology may give both competition in the years to come: IEEE 802.20. This standard, like 802.16 is aimed at wireless high-speed connectivity to mobile consumer devices—such as cellular phones, PDAs, and laptops.

802.20 will run in the 500 MHz to 3.5 GHz range and is being led by Flarion Technologies and ArrayComm. While officially, the two standards are not trying to do the same thing or compete for the same audience, not everyone agrees that that is the case. Rerisi says, "They do have some minor differences, but they both are aimed to serve similar users."

Mathias comments, "Both attempt to deal with mobile broadband. My feeling about it is 'may the best man win.'" That, he thinks will be, "Whoever does the best marketing job wins. The conventional wisdom is that 802.16 will win but I think it's too early to handicap this race."

With the strong support of Intel—with its considerable resources, marketing muscle, and influence—most analysts believe that WiMAX will become successful and popular. As Mathias observes, "the real question will be how effective will WiMAX be in the mobility end of things and for that we don't have an answer, but I wouldn't bet against it."

Article courtesy of EnterpriseITPlanet.com

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