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The 802.16 standard covers a lot of ground. When the IEEE approved it in 2001, it addressed wireless communications in the 10-66 GHz range and targeted line-of-sight, point-to-point applications. In January 2003, the IEEE approved an amendment, 802.16a, which expanded the scope to include the 2-11 GHz range and, more important, set the stage for point-to-multipoint, non-line-of-sight applications.
Figure 2.12 WiMAX forum - interoperability
WiMAX IN DEPTH
The WiMAX Forum is focusing on 802.16a as of now and more specifically on one of the four PHYs that the standard allows. As
802.16 is very flexible, the only way to achieve interoperability is to narrow it down to a certain set of system options. Since 802.162004 addresses the entire sub-11 GHz frequency range, there is an inherent need for a number of different solutions or profiles to use the vernacular of the WiMAX Forum. Therefore, the WiMAX Forum has devised system profiles that specify combinations of parameters, such as operating frequency, modulation scheme and channelization. Presently, the WiMAX Forum has identified five profiles for 802.16-2004 that allow the technology to accommodate different frequency bands, channel bandwidths and duplexing schemes (TDD/FDD).
Interestingly, the 20 MHz radio channel that was required to achieve 70 Mbps of throughput is not one of the focus points at the moment. Some equipment providers are also currently targeting a 700 MHz solution for use in rural deployments, although it remains to be seen when, or even if, a profile is developed for this spectrum. (Note: 700 MHz is a very favourable spectrum for mobile use.)
When equipment companies unveil products built to these profiles, the forum will test them - in laboratories being set up now - for both conformance with the profiles and interoperability. The forum will credit products that pass with a ‘WiMAX Certified’ label.
The use of profiles is clearly needed in order to support a wide range of deployment options; in particular it reduces the abundance of options to a manageable number and also causes the industry to focus on those profiles that should be implemented first. WiMAX Forum has released profiles based on three spectrum bands for global deployment: 5, 3.5 and 2.5 GHz. Each of these bands is briefly discussed below.
Unlicensed 5 GHz
This frequency range includes bands between 5.25 and 5.85 GHz. In the upper 5 GHz band (5.725-5.850 GHz), many countries allow higher power output (4 W) which makes this band more attractive to WiMAX applications globally. Because much of this spectrum is unlicensed in the USA, it is readily available for WiMAX deployment without individual FCC licensing.
Licensed 3.5 GHz
Bands between 3.4 and 3.6 GHz have been allocated for BWA in the majority of countries, with the exception of the USA. In the USA, this spectrum is designated for use by the Federal Government. Because the WiMAX Forum is focusing its efforts internationally, however, much of this spectrum is available for WiMAX use in Europe and elsewhere.
Licensed 2.5 GHz
The bands between 2.5 and 2.69 GHz have been allocated in the USA, Mexico, Brazil and some Southeast Asian countries. In the USA, much of this spectrum has been licensed for use in the multipoint distribution service (MDS) and the instructional television fixed service (ITFS; Table 2.7).
Forum Certified™ Products
WiMAX Forum CertifiedTM products will be based upon a single global standard enabling complete interoperability worldwide. In an 802.16-based network, a network provider would set up base stations consisting of one or more sectors that are connected to their edge and core networks via wireless or wireline connections as appropriate. Each base station, capable of supporting hundreds of products vs. proprietary wireless access technologies, creates a strategic option for the network planner focused on developing a network fabric that is capable of scaling over time.
Products that have been through the WiMAX Forum CertifiedTM process will reduce investment uncertainties for all parties in the access network value chain, from technology providers to service providers to end users. For network operators, equipment and component
Table 2.7 Worldwide allocation of licensed and licence-exempt bands
Country/geographic area Bands used (licensed and licence-exempt)
North America, Mexico 2.5 and 5.8 GHz
Central and South America 2.5, 3.5 and 5.8 GHz
Western and Eastern Europe 3.5 and 5.8 GHz
Middle East and Africa 3.5 and 5.8 GHz
Asian Pacific 3.5 and 5.8 GHz
WiMAX IN DEPTH
manufacturers, and ultimately, for subscribers, products that are WiMAX Forum Certified™ will deliver wireless broadband access with a range of interoperable components.
Further, the evolution of a service provider’s network over time being a key concern, especially the multi-vendor network that might result from standards-based products being available, will be solved by WiMAX Forum Certified™ products. For example, one of the building blocks of the IEEE 802.16 standard is the concept of a ‘variable burst length,’ a feature adopted to ensure a migration path from ATM networks to IP networks. With WiMAX Forum CertifiedTM products, service providers can be sure that this type of evolution can occur in their network even when it is made up of products from multiple vendors as certified interoperability will guarantee a known interoperability level between systems.