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Although the initial “Wave 1” version of mobile WiMAX made its commercial debut last summer, vendors and service providers are focused on the next-generation “Wave 2” version that includes many of the high-performance smart antenna features. Major service providers, such as Sprint Nextel and KDDI, prefer Wave 2 to the point that they are not likely to certify devices for use on their networks that do not support Wave 2 capabilities.

As a result, WiMAX solution providers who plan to target the mass-market segment of the 802.16e application need to focus on developing Wave 2 products because mobile WiMAX networks are being prepared for launch in Asia and the United States. For that, one must understand Wave 2's key smart antenna feature as defined by the WiMAX Forum: multiple-input, multiple-output (MIMO) antenna technology.

Compared to a fixed environment, mobility has more variables that affect signal propagation between the base station and the terminal, which affects performance. To accommodate these variables, and to optimize performance under fast-changing channel conditions, Wave 2 requires user devices to have receive 2 antennas to maximize the benefit the user can derive from advanced antenna technologies such as MIMO and beamforming. These technologies improve the user experience in terms of signal coverage and user throughput by addressing co- and adjacent-sector interference, as well as the signal distortions that stem from the various types of fading, including angle, delay and Doppler spreads.

Consequently, designers should look for suppliers who have extensive MIMO experience, when selecting Wave 2 chipsets.

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