FEATURE: The Evolution of WiMax Certification

The initial wave of WiMax certification is coming to an end, and we're all eagerly anticipating the first WiMax-certified products by the end of the year. This is an important moment for the entire WiMax community: After much hype and anticipation we will be able to assess WiMax performance in real networks, instead of making educated guesses from abstract specifications. 

These first WiMax products, however, mark only the beginning of a certification process that will ultimately include numerous "waves" of testing. Each wave will include new certification profiles and or new functionality to support new frequencies and different access modes (fixed, nomadic, portable, and mobile). The changes in the program are driven mostly by technological advances and product availability. They are crucial for ensuring that certified products have the functionality that the market requires and can support new applications and services. Understanding how the certification process evolves is necessary if we are to have accurate expectations of certified products. 

Product certification is an inherently complex process, especially when it involves interoperability among vendors, as is the case for WiMax. The Wi-Fi Alliance, for instance, has been very successful in guaranteeing interoperability for certified products. But this has required a constant expansion of the number of profiles and the functionality that is tested and has taken more than five years to get to where we are today. Some of the additions are certified as optional add-ons, but in some cases they soon become an integral part of the basic test suites. 

The WiMax Forum is following a similar path. It is defining different system and certification profiles for classes of products that interoperate with each other, and setting subsequent certification waves, each including additional functionality.

System profiles set a basic level of common requirements that all WiMax systems have to meet. To date, only one system profile has been defined and it is based on the 802.16-2004 version of the IEEE 802.16 standard. A second system profile is currently being defined and will be based on the 801.16e amendment. The first system profile is optimized for fixed and nomadic access, the second for portable and mobile access.

For each system profile there are multiple certification profiles. For the 802.16-2004 system profile, five certification profiles have been defined so far. No certification profiles have been announced yet for the 802.16e system profile since the overall specification is not expected to be ratified until the end of this year, but the first ones will probably be for the 2.3 GHz and 2.5 GHz bands. Certification profiles are defined by a system profile, the relevant spectrum band, what kind of duplexing is used (time division duplexing, TDD, or frequency division duplexing, FDD), and the channel width. 

The changing scope of certification

The WiMax certification program has been split into several waves with each successive wave adding new profiles and functionality along the way. The products certified under the initial wave undergo an early and more limited set of tests. This is a wise choice as it focuses on the air interface protocol of WiMax and sets the entire program on a solid footing. In subsequent waves, new profiles and functionality will be added. This means that interoperability between a product certified during the first wave and one certified during the second wave will be limited to the basic set of features tested during the initial wave. 

The 802.16-2004 products submitted for certification in the first wave entered the certification lab in July and August 2005. The first certified products are expected to be announced by the end of 2005, with commercial availability starting in early 2006 and deployments later in the year. Certification of 802.16-2004 products will continue in wave two during the first half of 2006, and it will include QoS, security and advanced radio features. QoS is needed to support VoIP and, more generally, to prioritize access based on users or applications (e.g. for subscribers that pay higher fees, or for real-time applications). The third wave of certification will extend support to indoor customer premises equipment (CPE) and PCMCIA cards to allow nomadic access. The first certified products are expected for the second half of 2006.           

Certification for profiles based on 802.16e is planned to start in the third quarter of 2006, with the first certified products expected in 2007. Initially, 802.16e profiles will support only simple mobility, which supports handoffs across cell and sector boundaries, but not real-time applications. Subsequent waves will include support for full mobility, including real-time applications and soft handoffs. 

The choice for operators 

Where does all this complexity leave those operators that are trying to decide what solutions to deploy and when to do so? They will certainly have some homework to do if they want to deploy gear from different vendors. The level of interoperability among different products may not initially cover features they consider essential or desirable (e.g., QoS or sub-channelization in the uplink). After multiple certification waves, the degree of interoperability may vary depending on the wave during which the products involved were certified. Operators will need to look beyond the certification stamp and understand what features are covered by certification and whether they match their requirements.

Monica Paolini is president of Senza Fili Consulting.

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