Even as Worldwide Interoperability for Microwave Access (WiMax) technology begins riding its first wave of deployment, second-generation equipment design is entering the water. WiMax developers are targeting what they call Wave 2 development, which aims to increase security and performance in fixed and mobile applications. Test equipment vendors are releasing new and upgraded equipment that addresses Wave 2 test needs throughout the development cycle, from design through production to field installation.
WiMax is just about ready to enter the wireless data communications marketplace--and make a splash doing so. According to estimates from an independent research study (due out this month) that the WiMax Forum commissioned, more than 133 million WiMax users will surface across the globe in the next four years. Forecasts also predict at least 250 service providers emerging in 110 countries worldwide, mostly in the Asia-Pacific region and the Americas. Such numbers indicate ample opportunity for developers creating chips, modules, end-user devices and basestation equipment.
Fixed and mobile
Two types of WiMax systems are involved in this opportunity, and they have different system requirements. Fixed WiMax (IEEE 802.16-2004) provides line-of-sight connections between the basestation and customer premises over a range of 30 miles, providing a wireless alternative to cable and DSL. Mobile WiMax (IEEE 802.16e-2005) uses additional modulation schemes to provide improved performance within a 10-mile radius for non-line-of-sight applications in which the user may be mobile. The WiMax Forum's study indicates that fixed and mobile WiMax will split the user market, with 70 percent going mobile. The forum anticipates that the first certified mobile WiMax user products will become available this quarter.
WiMax is still in early development, however, and design opportunities remain. Both the fixed WiMax and mobile WiMax communities are actively pursuing technology enhancements to support Wave 2, for which test equipment is becoming available.
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End-to-end system test for Wave 2 mobile WiMax is possible using Agilent's E6651A RF emulator and protocol certification software. |
For fixed WiMax, Wave 2 refers to protocol enhancements that provide quality-of-service controls to support real-time applications such as voice-over-IP (VoIP), streaming media and gaming. It also includes security enhancements such as adoption of the enhanced encryption standard (AES).
For mobile WiMax, Wave 2 further includes support for system designs that use multiple-input, multiple-output (MIMO) antennas to increase performance through active beam forming and increased spectral efficiency.
The enhancements of WiMax Wave 2 have created new test needs for developers working on every aspect of WiMax deployment, including the design of chips, end-user devices and provider basestation equipment. The range of test capabilities required by developers is substantial because of the existence of two WiMax approaches and the many system elements needed for end-to-end communications.
While they share radio frequencies, for example, fixed and mobile WiMax use different modulation schemes and thus different RF test capabilities. Further, mobile WiMax requires testing RF elements for multipath, fading and hand-off behaviors that arise from the user's changing location. The two approaches also use different protocols for encapsulating data and handling connection control. Basestation and user equipment also differ in behavior and hence test needs.
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Field personnel can test WiMax basestation transmissions using handheld testers like this BumbleBee-EX from Berkeley Varitronics Systems. |
Test equipment vendors are rising to the occasion with new products and product enhancements to address the increasingly complex requirements of development, verification and certification of WiMax designs. Test equipment is becoming available for everything from parameter measurement through turnkey conformance testing in the R&D, manufacturing and field environments. Recent introductions for Wave 2 WiMax test include station RF emulation for receiver module testing, fixed- and mobile-protocol conformance testers to exercise baseband processors and software, and end-to-end testing for systems and applications evaluation.
Richard A. Quinnell (RichQuinnell@att.net) is a contributing technical editor located in Gardiner, WA.
