While unified communications vendors have begun to incorporate mobility over wireless LANs, the real vision of UC is to provide those rich communications capabilities wherever the user is located. One of the unfulfilled promises for delivering wireless connectivity over the wide area has been WiMAX. Short for Worldwide Interoperability for Microwave Access, WiMAX describes wireless access networks built on the IEEE’s 802.16 standards. The WiMAX standards describe two separate technologies that can operate in a variety of channel sizes, using licensed or unlicensed radio spectrum, running anywhere between 2 GHz and 66 GHz. The IEEE is currently developing a radio link interface for the recently auctioned 700 MHz channels. While we have a lot of options, in this US we don’t have much in the way of actual WiMAX services.

The first thing to recognize about WiMAX is that it has virtually nothing to do with Wi-Fi. Although I have heard the dull-witted regularly describe WiMAX as “Wi-Fi on steroids”, the two technologies are positioned to serve completely different requirements. Wi-Fi is a private network technology designed to provide mobility on unlicensed channels over a relatively short range- around 100m. WiMAX is intended as a technology to be used by carriers to deliver last-mile (actually several miles) connectivity. To make it simpler: Wi-Fi is a product, and WiMAX is a service.

The lines have gotten somewhat blurred as operators like AT&T, T-Mobile, and Wayport now use Wi-Fi to provide Internet access service at Hot Spots. However, the business model for WiMAX is more along the lines of a cellular carrier. The carrier would buy the WiMAX base station equipment, build a network complete with backhaul connections, and offer a wide area wireless service to users for a fixed monthly fee. The user would have to buy a WiMAX-compatible radio modem to subscribe to the service, though the hope is that the WiMAX modem will eventually be built into every laptop, much the way Wi-Fi is today.

What is “WiMAX”?

While that’s the overall plan, the picture gets murkier when you try to figure out what that WiMAX service actually is. The WiMAX standards describe two completely different networks. The original objective for WiMAX was a fixed location broadband wireless access service, something akin to wireless ADSL. Along the way the committee decided to expand the focus to address mobile applications, and developed a second, incompatible version of WiMAX. Mobile WiMAX networks would have the ability to hand off connections between base stations as a user moved through the coverage area much like a cellular 2.5G or 3G service. The standard for the fixed version is described in IEEE 802.16-2004 (formerly 802.16d) and the mobile version is 802.16-2005 (formerly 802.16e).

The trouble is that neither of the WiMAX standards is widely deployed in the US. There are a number of carriers offering fixed location wireless access services, but the vast majority of those use technologies that pre-date WiMAX. The largest of these carriers is Clearwire Communications who has 394,000 subscribers. Clearwire targets smaller markets where the availability of broadband ADSL and cable modem services is limited. Clearwire’s service offers downstream data rates of 512 Kbps and 1.5 Mbps for $30 and $40 per month including the modem rental. While the WiMAX community likes to claim these as “WiMAX subscribers”, in reality the vast majority of Clearwire’s subscribers are supported on equipment manufactured by NextNet Wireless (now a division of Motorola) that does not conform to the WiMAX standards. Without standards, we lose the advantage of lower-cost products and inter-carrier roaming.

While WiMAX could operate at any frequency between 2 GHz and 66 GHz, the primary target is the Broadband Radio Services (BRS) band that runs from 2495-2690 MHz (shared with Educational Broadband Service). The two largest holders of that spectrum are Sprint (who acquired it with the acquisition of Nextel) and Clearwire. The two then went through an on-again, off-again joint marketing agreement in 2007 that is “off” for the moment though it may be resurrected. In the joint network agreement, Sprint would cover the big cities and Clearwire would cover the smaller ones. The networks would use compatible implementations of mobile WiMAX, so users could roam between them.

For their part, Sprint had committed to spend $5 billion to make mobile WiMAX service available to 100 million people in the US by the end of 2008. However, those 100 million people would be in located in major metro areas. To make the service attractive to most travelers, the WiMAX device would also require a 3G cellular data capability (e.g. HSDPA or more likely EV-DO in Sprint's case), and a service plan that included 3G access when the user was in an area without WiMAX coverage. Even if financially troubled Sprint could pull this off (an unlikely prospect) that would still leave the vast majority of the US geography uncovered for years to come.  

Conclusion

When I started this article I had to decide if the title should be “Whither WiMAX” or “WiMAX Withers”. I picked the former because there does seems to be an area where WiMAX is taking root. While mobile WiMAX is struggling to gain traction in the US, fixed WiMAX is catching on in lesser-developed countries. India’s Tata Communications has recently announced a nationwide rollout plan for fixed WiMAX, and similar plans are being unfurled in other countries who lack the copper wire or coaxial cable facilities needed to support ADSL or cable modem services.

I’m afraid that US-based enterprise organizations looking for wide area mobility options will have to look at a range of options that do not include WiMAX in the near term. However, mobility is still a key element of unified communications, and there are other available wireless network options an enterprise can pursue today.