Wireless Systems Design

Unrealistic Expectations Threaten WiMAX's Success

The industry must stop hyping WiMAX in order to recognize where the specification is now, what it must overcome, and the other issues that stand between it and world domination.

Despite some great charitable and technological efforts, the disparity between the world's networked and non-networked populations seems only to have worsened. The better-connected populations are enjoying a move to next-generation cellular standards and wireless personal-area networking. Meanwhile, many impoverished areas don't even have landlines or Internet access. In the countries that do have a communications infrastructure, only the cities and their surrounding areas enjoy the newest, higher-speed services. In the rural areas, high-speed access is unattainable—for now.

Thanks to an emerging broadband-wireless-access (BWA) technology, such rural areas may soon enjoy high-speed access. Known as WiMAX (IEEE 802.16), this specification was spawned out of the ever-multiplying IEEE 802.xx family. According to the WiMAX Forum (www.wimaxforum.org), 802.16 can be used to backhaul 802.11 hot spots and wireless-local-area networks (WLANs) to the Internet; provide campus connectivity; and enable a wireless alternative to cable and DSL for last-mile broadband access (SEE FIGURE).

Of course, the capabilities that are described above only apply to one form of WiMAX: the 2-to-11-GHz specification for wireless-metropolitan-area-network (WMAN) technology. Even in this early, pre-product stage, multiple WiMAX variations are already being tossed around (SEE SIDEBAR).

Ken Wetherell, Wi-LAN, Inc.'s (www.wi-lan.com) VP of Corporate Communications and Investor Relations, summarizes them this way:

  • 802.16a addresses 2-to-11-GHz, licensed (2.5-, 3.5-, and 10.5-GHz), and unlicensed (2.4- and 5.8-GHz) frequencies. It is non-line-of-sight (NLOS) compatible.
  • 802.16b targets license-exempt applications around 5 to 6 GHz (the U-NII bands).
  • 802.16c adds interoperability with other frequencies (10 to 66 GHz).
  • 802.16d, which has been renamed 802.16-2004, consolidates 802.16, 802.16c, and 802.16a with an expansion of the band to include all frequencies below 2 GHz.
  • 802.16e adds mobility enhancements for the media-access-controller (MAC) layer. It is expected to be ratified by the third quarter of next year.

Thanks to the consolidation within 802.16-2004, that specification and 802.16e have now become WiMAX's two main focuses. Yet people are still confusing early facts about 802.16a with the evolution of WiMAX now. If the current confusion over WiMAX isn't resolved, it could hurt the specification's progress. According to Phil Belanger, BelAir Networks' (www.belairnetworks.com) VP of Marketing, "WiMAX can operate from 2 to 11 GHz. (Newer 802.16 variants cover some higher-frequency bands.) It can be licensed or unlicensed. It can be fixed wireless or mobile. It uses FDD or TDD, depending on the frequency band. It operates at 70 Mbps at ranges up to 50 km. The hype about WiMAX takes all of the capabilities and rolls them into one."

Obviously, the industry at large needs to get better acquainted with WiMAX and all of its nuances. Many are looking to the WiMAX Forum for this clarification. It's widely noted that this forum has largely followed the successful model of Wi-Fi standards development. From those roots, it continues to flourish. The WiMAX Forum has gained the backing of leading wireless-chip-set companies like Intel and Fujitsu as well as more enterprise-focused companies, such as Proxim. Recently, many service providers also have become involved. Impressively, the forum has succeeded in getting this wide range of companies—many of them competitive—to agree on a single standard.

Many believe, however, that the forum hasn't done enough to get the public better acquainted with WiMAX. If it doesn't more clearly and realistically communicate the specification's capabilities, the current hype could affect WiMAX's future success. (Think back to the excitement that almost killed Bluetooth before it was born.)

Both the industry and the public need to know the truth about WiMAX: the real potential of its variants, its known limitations, potential areas of concern, and the specification's roadmap. Like every other technology, WiMAX is sure to encounter problems and obstacles. Doug Grant, Analog Devices' (www.analog.com) Director of Business Development, RF & Wireless Systems, lists a few areas of concern: "It might be oversold and set unrealistic expectations for consumers. All wireless systems—particularly in the UHF/microwave spectrum—have limitations. Obstacles like trees and buildings can block signals and result in a frustrated user. Unlike satellite-based systems, in which a directional antenna can be aimed at the sky, terrestrial systems have local impairments. There is also danger in people using unlicensed spectrum and being disappointed in the performance in environments where there are other users in the same (unlicensed) frequency band."

Physical obstacles and other users probably aren't the only path to unhappy consumers, however. The old RF enemy, interference, is very likely to rear its head in the unlicensed spectrum. Every RF technology is susceptible to interference. The question is what will cause it. WLANs are one potential culprit. Despite the hype, WiMAX is predicted to work with wireless LANs—not make them obsolete. Due to this co-existence, WLANs could act as interferers. The same can be said of cordless phones.

Essentially, interference could arise between WiMAX and any wireless service that inhabits the same frequency bands—including itself. Airpath Wireless' (www.airpath.com) CEO, Todd Myers, notes that WiMAX could interfere with other WiMAX hot zones due to a lack of regulation regarding potential placement opportunities.

The issues surrounding WiMAX's use of unlicensed spectrum will undoubtedly be critical to its performance and—by extension—its success. Yet WiMAX also must arm itself for the global spectrum battle. Walt Burns, Director of IT Wireless Network Solutions for Unisys Corp. (www.unisys.com), notes, "International spectrum allocations are anything but uniform. WiMAX technology can utilize a wide swath of both licensed and unlicensed bands. But regulatory issues in various countries have the potential to box it in and limit its potential for performance, reliability, and ubiquity. This translates into fewer companies making new product with lower volumes and higher costs."

The threat of limited market penetration is the thread that runs through all of the potential obstacles to WiMAX. The first WiMAX products are expected toward the end of this year. More products are on the horizon for 2005. If these products aren't widely adopted, the specification's ability to target new applications will be hindered.

This issue brings another often-overlooked fact to light: Fixed-wireless products already exist. They're just limited by their proprietary nature. As stated by Dr. Jack Winters, Chief Scientist at Motia (www.motia.com), "Despite a standards-based and interoperable approach to fixed wireless, WiMAX is competing against a number of other viable, fixed-wireless approaches. Those approaches have products that are either being deployed, such as EV-DO, or are closer to product deployment like Flarion OFDM. WiMAX requires widespread deployment in both clients and base stations to be successful, and widespread user/service-provider acceptance is not certain."

If it works harder on clarifying its message, WiMAX should reach the necessary level of market penetration. On the technology end, it is already working hard to fulfill its current performance and interoperability promises. The standards committee's plugfest is scheduled for the first quarter of 2005. Certification for systems, CPEs, and base stations also is slated to take place next year. At the end of 2005 and through 2006, competitive equipment and service pricing should emerge.

Obviously, the WiMAX Forum has charted a clear course for the specification. But can WiMAX accomplish so much in such a short time? It all depends on whether the different parts of the industry can each meet their own respective deadlines. Jeff Orr, Proxim's (www.proxim.com) Senior Product Marketing Manager, Broadband Wireless, says, "There is still a lot of work to be done before products can be lab tested in early 2005. For system vendors to be successful, ASIC suppliers must provide their components. Doing so will provide adequate time for integration by system vendors into their platforms and software development to be completed and tested. In parallel, service providers must determine their business plans to enable early success using broadband wireless. Those who have already deployed proprietary systems will be looking for efficiencies gained using WiMAX Forum Certified products. Those who have not yet deployed need to identify their service model, deployment capabilities, tower/roof rights, and backbone requirements."

In summary, this specification is still growing up. Like a gifted child who isn't yet ready for the spotlight, WiMAX must first bear the weight of the hype that surrounds it. WiMAX won't replace WLANs or cell phones. Nor will it eliminate 3G. Yet it should replace existing, proprietary fixed-wireless technologies—thanks to its spectral efficiency, interoperability, extended range, lower cost, and NLOS coverage. If it moves forward as planned, WiMAX will deliver last-mile access to rural locations. After some initial success, the 2-to-11-GHz version will be superceded by new versions and standards. Those future BWA standards could eventually provide access to the non-networked parts of the world.


An often overlooked fact about WiMAX is that it has numerous variants. The industry hasn't always differentiated between these specifications, leaving them partially to blame for the confusion surrounding WiMAX's overall capabilities. Here, the two main forms of WiMAX at this time—802.16d (now 802.16-2004) and 802.16e—are described with the help of Margaret LaBrecque, Director of WiMAX Spectrum Policy, Intel Broadband Wireless Division, and Chair of the WiMAX Forum Regulatory Working Group:

  • The fixed-wireless 802.16a has been replaced by 802.16d. 802.16d is 802.16a + improvements and errata. Theoretically, 802.16d will have 75 Mbps of peak data throughput in 20 MHz of spectrum. Note that many factors can impact that throughput, such as the amount of frequency re-use and the exact frequency band. It also depends on whether the usage is indoor or outdoor and close in or far out.
  • The portable variation of WiMAX, dubbed 802.16e, has a target standard-completion date of the first quarter of next year. Systems based upon the standard should begin appearing in 2006. The frequency is below 6 GHz per the standard, as the 2-GHz lower bound was removed. Right now, the prediction is that 802.16e will boast 30 Mbps of peak data throughput in 10 MHz of spectrum. (There isn't any equipment yet, so one has to base these estimates upon industry-accepted models.) Again, many factors are involved here: frequency re-use, whether the user is indoors or outdoors, moving or stationary, close-in or far out, etc.

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