Taking wireless to the max: is WiMAX the next big thing in high-speed wireless access?

IF YOU'RE READING this magazine, chances are good you're familiar with Wi-Fi. However, you're probably less familiar with its cousin, WiMAX. It's easiest to understand WiMAX in relation to Wi-Fi. Think of it this way: WiMax offers the same kind of high-speed wireless connection as Wi-Fi, but on a larger scale. Whereas Wi-Fi is a way to wirelessly connect local area networks (LANs), WiMAX offers a way to wirelessly connect metropolitan area networks (MANs)--not to be confused with wide area networks (WANs), which imply the kind of nation-wide networks you get with technologies such as EV-DO.

Industry consortiums, take 2

The comparisons to Wi-Fi don't stop there; as technology standards, Wi-Fi and WiMAX have evolved in much the same way. Technology standards are meaningless without interoperability testing and certification. And, although the Institute of Electrical and Electronics Engineers (IEEE) excels at publishing standards and building engineering consensus for technical protocols, it doesn't test products to ensure their compliance with the published specifications. Enter the Wi-Fi Alliance. The goal of the Wi-Fi Alliance is to enhance the user experience through product interoperability. It does this by making sure that all Wi-Fi certified products conform to the IEEE 802.11 protocol.

So, what Wi-Fi has done for 802.11, Wi-MAX is doing for the IEEE 802.16 protocol (http://www.wimaxforum.org). Simply stated, WiMAX is an industry trade group created to perform interoperability testing and certification and to help promote the 802.16 standard.

The WiMAX acronym actually stands for Worldwide Interoperability for Microwave Access. (Yes, somehow that spells WiMAX.) The reason for all of the attention is that there is enormous potential for this technology to provide a last-mile solution for delivering high-speed Internet access in cities everywhere. This category of network deployment is often referred to as Broadband Wireless Access (BWA).

According to John Muleta, Chief of the Wireless Telecommunications Bureau at the Federal Communications Commission (FCC), BWA technology represents a real threat to the Cable Modem/DSL duopoly. At a recent industry trade show, Broadband Wireless World 2004, in San Diego, Mr. Muleta commented "No more cables, no more fiber optics, no more wires at all!" According to Mr. Muleta's vision, we could see 100 million BWA households (150-200 million subscribers) by the year 2010, or earlier.

BWA also has the potential to reach rural areas where high-speed options aren't always available. From a carrier perspective, BWA could fill the gaps in their existing operating areas where subscribers are too far from a central office (CO) to get DSL service, or too far from the CO to get the highest speed DSL options. (The closer you are to the CO, the faster your DSL service).

Where WiMAX differs from Wi-Fi

As you've seen, WiMAX and Wi-Fi share many traits. However, when you dig around under the hood, you'll notice a number of engineering details that differentiate WiMAX (802.16) from Wi-Fi (802.11). Perhaps the two most interesting elements relate to the channel width (as measured in MHz) and the possible range of frequencies where WiMAX can be applied. For technical details, see the Wireless 101 sidebar.

In the U.S., all Wi-Fi products ship with configurable channels, from 1-11. Each channel represents a specific 22MHz block of frequencies. The entire 802.11b/g band is 83.5MHz wide, with each channel 22MHz wide. You may be wondering, how we fit 11 22MHz-wide channels into a space that's 83.5MHz wide. The answer is we "cheat." Every channel overlaps with other adjacent channels. Each channel's center frequency is separated by only 5MHz. This means the only true non-overlapping channels are 1, 6, and 11.

For 802.11a, the entire band is 300MHz wide. Each channel is 20MHz wide, and center frequencies are spaced 20MHz apart from each other. This means all 12 channels are non-overlapping. Note that 802.11 a frequencies reside in the 5GHz spectrum.

What makes WiMAX interesting and unique is that it can live in a variety of frequencies. In fact, the specification defines potential frequency usage anywhere from 211GHz--a huge range! This range encompasses both licensed and unlicensed potential uses. Furthermore, the channel width under WiMAX is variable. Channel widths of 1.75, 3.5,7, and 10MHz are defined. This provides an extraordinary amount of flexibility for licensed providers. If a particular carrier has purchased 14MHz of frequencies in a particular geographic region, that carrier could deploy two 7MHz channels, or four 3.5MHz channels, etc. This gives network designers many choices when trying to find the most efficient way to utilize the available spectrum.

In terms of performance, WiMAX will define and certify a variety of profiles. The most optimistic of these scenarios calls for speeds upwards of 70Mbps with a range of 30 miles. Furthermore, WiMAX doesn't require line of sight, which is a bonus in metropolitan areas where trees, buildings, and other obstructions prevent a direct line-of-sight link between two locations.

Where this is taking us

With wireless broadband, voice, video, and all manner of data services become global and ubiquitous. Forget about delivering data over your coaxial Cable TV line or delivering data over your copper telephone line. With WiMAX, the tables are turned. WiMAX could deliver your telephone and television services over the data network connection (in this case, it just happens to be wireless). So, a data link is no longer just about providing an Internet connection to surf the Web.

With all that available data bandwidth, be prepared to see IP-based video services take off. According to lack Chung, President of MatrixStream Technologies, the secret to delivering video is to provide localized content, all on demand. "Imagine being able to view your local sports team as easy as your favorite sitcom ... all in high definition!" He continues, "Now all programming can truly be on-demand. It will bring a revolution to the way we think of television and all media." With WiMAX, the future may be coming to a TV set near you. Wirelessly!

By creating an alliance to develop standards and, more importantly, provide interoperability testing and certification, the WiMAX Forum can help usher in the new era of broadband wireless access and choices for consumers. Compliance testing and certification gives users confidence in their purchases. Just as the Wi-Fi user knows that one Wi-Fi-Certified device will work with another Wi-Fi-Certified device, so too can operators begin deploying Wi-MAX solutions with confidence that all the components will work in harmony. Standards will bring competition, which will in turn, bring low prices, which will in turn, fuel greater adoption. It's a virtuous cycle we've seen before.

I want my WiMAX TV (now!)

Companies such as Intel, Alvarion, Aperto, Atheros, Proxim, WiLAN (and 70 more) have signed up for membership in the WiMAX forum. With Intel promising chipsets in July, WiMAX has scheduled the first "plugfest" (an industry bakeoff/testing party) for December 6th, 2004. The first WiMAX certification testing has been slated to take place on January 10th, 2005. Sure, the goals are ambitious, but with such enormous potential, this is a definitely a space to keep your eye on. If WiMAX gains traction and reaches critical mass in the marketplace, the next few years are a whole new ballgame for wireless.

MOBILE BUSINESS BENEFITS

Ultra-high-speed wireless access could be just around the corner.

Wireless 101

What are radio frequencies? In an RF context, a channel represents a particular frequency or range of frequencies. For example, if your favorite FM radio station is 91.1 on your stereo, the "91.1" represents the center frequency of the station, 91.1 MHz. When creating the FM system, the FCC determined that each radio station should be allocated a range of frequencies .2 MHz wide in a space from 88MHz to 108MHz. This means the first possible station (88.1 MHz) can transmit between 88.0 MHz and 88.2MHz. The next possible station (88.3 MHz) can transmit between 88.2MHz and 88.4MHz. (In practice, FM stations only use. 1MHz and leave a .05 MHz buffer on each side of their frequency range to help reduce channel interference).

Shifting gears to how 802.11b/g uses RF, you have to move into the GHz range. (MHz stands for MegaHertz, or Millions of Cycles per Second, while GHz stands for GigaHertz, or Billions of Cycles per Second.) In the U.S., all Wi-Fi products ship with configurable channels, from 1-11. Due to regulatory requirements, channel allocations may be different depending on the rules in your particular country.

Each channel represents a specific 22MHz-wide block of frequencies in the range of 2.4000GHz--2.4835GHz. For example, the center frequency for channel 6 is 2.437GHz, but the entire channel spans from 2.426GHz to 2.448GHz. So, the only non-overlapping channels are 1, 6, and 11.

Channel       Frequency Range
              (in GHz)
1             2.401 - 2.423
6             2.426 - 2.448
11            2.451 - 2.473

Lee Barken, CISSP, CCNA, MCP, CPA, is the co-director of the Strategic Technologies And Research (STAR) Center at San Diego State University. He has worked as an IT consultant and network security specialist for Ernst & Young's Information Technology Risk Management (ITRM) practice and KPMG's Risk and Advisory Services (RAS) practice. Lee is the cofounder of the San Diego Wireless Users Group and writes and speaks on the topic of wireless LAN technology and security. He is the technical editor for MOBILE BUSINESS ADVISOR MAGAZINE, and the author of How Secure Is Your Wireless Network? Safeguarding Your Wi-Fi LAN (ISBN 0-13-140206-4).