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.

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.

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.

To address the changes that Wave 2 brings to mobile WiMax receiver design, Agilent Technologies has updated its E6651A mobile WiMax test set to incorporate MIMO functionality. The test set can perform both RF parametric characterization and basestation emulation, so transmitters and receivers can be evaluated both as RF components and as system elements. Agilent also offers Wave 2 protocol conformance test software to exercise the entire end-to-end transmission of information through the design. The upgrade further automates the task of testing the finished design against standards before applying for certification.

Aeroflex, working with AT4 (formerly Cetecom, Spain), is making several pieces of equipment available for RF conformance testing. The Mint E1130 signaling unit can emulate basestations and mobile stations for testing equipment at either end of a mobile WiMax link; the Mint T2110 RF conformance test unit automates conformance testing at both ends. The two companies also offer protocol conformance test gear for mobile Wave 2 WiMax. The WiMax Forum recently designated the Aeroflex/AT4 test equipment as the official test equipment for WiMax product certification.

The Anite Group, for its part, has released basestation and mobile-station emulators for both fixed and mobile Wave 2 WiMax. In addition, Anite has released what it says is the first protocol conformance tool set to automate fixed Wave 2 WiMax certification testing. The tool set is intended for use by subscriber-station and basestation system vendors, chip-set and stack developers, system operators, and test labs.

Rohde & Schwarz has upgraded its CMW270 communications tester to support evaluation of mobile WiMax user-station chip set designs for Wave 2 operation. Combining signal generation and signal analysis in a single unit, the CMW270 functions as a basestation emulator with the ability to change transmission parameters during operation to simulate real operating conditions. Similarly, the recently upgraded Azimuth Systems 400WB channel emulator supports as many as 4 x 4 MIMO bidirectional channels for real-time emulation of over-the-air conditions such as multipath.

The newly introduced LitePoint IQnxn and the recently upgraded Spirent Communications SR5500 also address MIMO test needs.

Developers are not the only ones benefiting from the recent wave of WiMax test equipment. Service providers are also seeing new test capabilities reach the market. Recent examples are WiMax upgrades for the Anritsu BTS Master and Spectrum Master handheld spectrum analyzers and the new BumbleBee-EX handheld WiMax spectrum analyzer from Berkeley Varitronics Systems. All allow field testing of WiMax basestation installations, evaluating signal power and spectral characteristics and helping locate sources of interference.

Most of these upgrades and product introductions have been released in just the past two months, and they likely represent the tip of an iceberg. As WiMax gears up for deployment, developers seeking to catch Wave 2 should already be entering the design stage. Those that do can be certain that the test tools they will need to refine and certify their design efforts quickly will be ready and available when needed.

WiMAX Wave 2 Test Equipment Vendors

Aeroflex
www.aeroflex.com
(800) 843-1553