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WiMax: A Spec Divided

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LR Mobile News Analysis
Light Reading
7/6/2005

Initial mobile WiMax products will not be backwards compatible with products based on the existing fixed-wireless specification, a fact that could set major WiMax deployments back months – even years, Unstrung has learned.

Fixed WiMax products – some of which are ready for initial interoperability tests by the WiMax Forum this month – are based on the Institute of Electrical and Electronics Engineers Inc. (IEEE) 802.16-2004 specification, otherwise known 802.16d (see WiMax: How Far? How Fast?).

Mobile WiMax products are going to be based on the 802.16e specification, which hasn't yet been ratified by the IEEE. Initial products using this specification are expected to be on the market late in 2006 or early 2007.

The fact that carriers won't initially be able to connect to a fixed WiMax base station using a mobile WiMax modem (and vice versa) is a big deal. It may even hold some carriers back from implementing WiMax, when fixed products become available late 2005 and into 2006, because the carriers would prefer to wait for mobile productions. And that would mean that WiMax rollouts would be delayed until in 2007 or even later.

U.S. operator Sprint Corp. (NYSE: FON), which is working with Intel Corp. (Nasdaq: INTC) on the 802.16e spec, says that it doesn't anticipate commercial WiMax deployments until 2007 or 2008 (see Sprint Firms Up WiMax Plans). But the firm is anticipating offering fixed and mobile, along with so-called "portable" services.

As the coming edition of the Unstrung Insider monthly research report notes, the two specifications were originally supposed to be backwards compatible.

"802.16 Task Group E (802.16e) is charged with developing an amendment to the current 80.16-2004 standard that covers 'Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands.' This implies 802.16e would be used for both fixed and mobile access – and according to several sources, dual fixed-mobile operation is still the goal," writes the report's author, Gabriel Brown, chief analyst for the Unstrung Insider.

But it's an open secret in the industry that the mobile specification will not initially interoperate with the fixed WiMax products.

The mobile standard will implement a new physical (PHY) layer on the chipset and enhancements to the media access control (MAC) to make it more suitable for mobile applications. "In effect then, there will be two types of incompatible WiMax – one that’s been widely implemented today for fixed use, and another that is still in draft form for mobile/portable," writes Brown.

Chipmaker Intel Corp. (Nasdaq: INTC), one of the leading proponents of mobile WiMax, confirms that the two specifications will not work together.

"Yes, that's exactly right, they do use different PHYs," an Intel spokeswoman tells Unstrung. She describes the two specs as "separate but complimentary," saying that Intel envisages fixed WiMax being used as a system to backhaul data for mobile WiMax, when 802.16e products become available.

And Brown notes that there may be some move towards backwards compatibility in the future:

"Sources say that... both sets of specifications may be consolidated into one über-standard document that will likely be known as 802.16-2005. They say this could happen at the next IEEE meeting in July 2005. Other sources also say there is a slim, outside chance that a mode that is backward compatible with 802.16-2004 could be introduced to the 802.16e specifications at the last minute – this is considered unlikely, however."

But all these industry moves will – like the development of 802.16 itself – take several years. Meanwhile, WiMax, which initially promised a common platform for broadband wireless vendors to build to, will stand as a specification divided.

— Dan Jones, Site Editor, Unstrung

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