Tools measure Mobile WiMax
Deployment of Mobile WiMax is on the rise, as is the number of WiMax chips supporting the IEEE 802.16e Mobile WiMax specs. The equipment market for the emerging high-speed mobile wireless standard, including basestations and customer premises equipment, is expected to reach $2.53 billion by 2012, according to Juniper Research. The market research firm also projects that the number of subscribers will ramp up from 1.7 million in 2007 to 21.3 million by 2012.
"There is considerable and growing interest in Mobile WiMax. A lot of customers are interested in understanding it and making sure they have tools that they will be able to use for WiMax test, even though they aren't yet doing it," said Jennifer Stark, industry marketing engineer at Agilent Technologies Inc. (Santa Rosa, Calif.).
The scope of Mobile WiMax test solutions extends to protocol and radio conformance testing, interoperability testing and regulatory testing at different stages of product development--R&D, design verification, manufacturing, installation and maintenance. Test gear capabilities include support for physical-layer signal generation, analysis for Wave 2 system profiles, and 4x4 multiple-input, multiple-output (MIM0) multi-antenna technology.
Basic measurements at the networking and physical layers are simple modulation and demodulation accuracy tests, called error vector magnitude (EVM), along with power-level testing, said Walt Strickler, worldwide sales development manager for Keithley Instruments Inc. (Cleveland). When the modulation becomes more complex, the EVM measurement likewise increases in complexity; the name changes to relative constellation error (RCE), but it's the same basic concept, he said.
"In testing of modulation, you can look at lots of different aspects of that to get more details, depending on whether you're doing R&D or manufacturing," added Strickler. Since WiMax is still maturing, many R&D tests are still done in the manufacturing phase, he said.
Commonly performed WiMax tests include DUT (device under test) RX/TX testing, sensitivity, strong signal level, adjacent and alternate adjacent channel rejection, output power, subcarrier flatness, RCE, carrier feedthrough, frequency offset and spectrum mask. Additional MIMO testing includes port isolation, cross correlation and channel condition number.
The WiMax Forum has created a certification program to ensure that all certified equipment will interoperate with devices from different vendors. There are three parts of conformance testing associated with the WiMax Forum Certified Program, said Stark: radio conformance test, protocol conformance test (PCT) and interoperability test.
"All of those come to bear in trying to get your products WiMax Forum certified," she said. Test equipment and chip sets aren't certified; only end-user mobile stations and basestations would go through certification steps. Nonetheless, there is a desire to check the performance of all of the constituent elements" that go into the end product.
Wave 2, 4x4 MIMO support
MIMO technology uses multiple radios for transmitting and receiving data in RF communications devices and delivers higher data rates and more-efficient bandwidth. All the buzz is in Wave 2 WiMax, which is a MIMO 2x2 approach with two transmitters and two receivers, said Strickler. "The only reason Wave 2 is only 2x2 is that it's very difficult to make anything larger," he said.
Keithley has released a 4x4 MIMO RF test system for R&D and production testing of next-generation RF communications equipment and devices. The test system consists of the Model 2920 vector signal generator (VSG), Model 2820 vector signal analyzer (VSA), Model 2895 MIMO synchronization unit and MIMO signal analysis software.
LitePoint Corp. (Sunnyvale, Calif.) has released its IQmax MIMO test system, aimed at WiMax devices with Wave 2 functionality. The IQmax MIMO solution combines multiple IQmax-500 hardware units with the latest version of IQsignal software. Both have been updated to include the new MIMO requirements.
While a basic system includes a pair of IQmax-500s plus a new synchronizing unit along with IQsignal, creating a 2x2 configuration, it can be expanded with up to two more IQmax-500s to implement a 4x4 setup.
Agilent Technologies Inc. (Santa Clara, Calif.) has added MIMO and Wave 2 test support to its VSA, Signal Studio and Mobile WiMax Test Set measurement solutions for testing the WiMax Forum's Wave 2 system profiles. Providing tools for engineers who require signal analysis, signal generation and end-to-end functional test of Mobile
WiMax, the 89601A VSA and N7615B Signal Studio measurement products offer a range of test capabilities that support physical-layer signal generation and analysis for Wave 2 system profiles. Specific capabilities include matrix A and matrix B signals for downlink, uplink collaborative MIMO, and creation of HARQ bursts and uplink sounding zones.
One-box testing
A few test providers also offer one-box testing, which generally consists of a source, or signal generator, an analyzer and software to test Mobile WiMax devices or modules. Agilent, for example, offers a wireless networking test set and OFDMA measurement application software as a complete one-box transmitter and receiver test solution for Mobile Wi- Max. The tool is designed for testing of WiMax mobile subscriber devices or modules that use IEEE 802.16e-2005. The N8300A one-box parametric WiMax test set provides a standard-compliant 802. 16e-2005 physical-layer test tool. The N6301A measurement application delivers analysis of Mobile WiMax signals.
The N8300A architecture integrates Agilent's vector signal analysis and VSG hardware, and features a front-panel graphical user interface and SCPI command set. Measurement algorithms and software leveraged from WiMax R&D test tools enable fast test development and measurement traceability through the product life cycle, Agilent said.
LitePoint offers the IQmax-100 one-box manufacturing test solution. With integrated VSA and VSG resources, the system offers test results for fixed and Mobile WiMax physical-layer parameters, including all bandwidth and data rate options for product development, volume manufacturing and quality assurance. The software-upgradable tester is positioned to support future WiMax implementations, including beam forming and MIMO. It also supports optional Wi-Fi and Bluetooth capability to test any WiMax, Wi-Fi, Bluetooth or combination product.
Partnering with chip makers
Test vendors are collaborating with chip makers to create and integrate test solutions. Agilent recently teamed with Fujitsu Microelectronics Pacific Asia Ltd. to integrate Agilent testers into Fujitsu's chip-set test solution for Mobile WiMax, enabling what the companies claim is the highest measurement throughput available in the industry. The Agilent MXZ-1000, an optimized turnkey solution for high-volume manufacturing, now features the Fujitsu chip-set library. Also included in the system is the Agilent E6651A test set for Mobile WiMax, which allows equipment developers and test houses to run validated protocol test cases to verify implementation conformance to the WiMax IEEE standards.
Agilent and GCT Semiconductor Inc. announced plans to implement a manufacturing test system for GCT's WiMax chip sets. Agilent will support the chip sets with its E6651A Mobile WiMax test set and MXZ-1000 WiMax manufacturing test system. The initial GCT chip set supported will be the 2.3-GHz Wave 1 Mobile WiMax products, comprising the GDM- 7201S baseband device and the GRF7201 RF chip. Volume deployment of 2.5-GHz Wave 2 chip sets will follow.
The Mobile WiMax test set, equipped with a Wireless Test Manager and auto- mation software package, can be used to calibrate and verify performance of GCT-based devices and to test many aspects of functionality, such as network entry. The MXZ-1000 WiMax manufacturing test system is optimized to control GCT chip sets directly.
Agilent also recently announced an extended collaboration with Sequans Communications to address Wave 2 Mobile WiMax mobile station and basestation protocol testing. Agilent describes PCT as a vital part of the WiMax certification process in ensuring a high degree of device interoperability.
The Agilent N6430A WiMax protocol conformance test and development solution, based on Agilent's E6651A Mobile WiMax test set, a full suite of RF
measurements for characterization, calibration and verification purposes, is undergoing prevalidation testing at a WiMax Forum testing laboratory using mobile terminals based on Sequans' Mobile WiMax chips. Se- quans' newest chip, the SQN1130 Wave 2-ready MIMO chip for WiMax mobile stations, is said to deliver more than 30-Mbit/second throughput while drawing less than 280 mW of power.
When equipped with the PCT capability, Agilent's E6651A Mobile WiMax test set allows equipment developers and test houses to run validated protocol test cases to verify that their implementations conform to WiMax standards.
LitePoint's one-box IQfact test software, meanwhile, now handles products based on Sequans' WiMax chip sets for turnkey testing in R&D and manufacturing applications.
The turnkey software package runs on IQmax-500 R&D and IQmax-100 WiMax manufacturing one-box test solutions. The first IQfact release supports products based on the Sequans SQN1110 Mobile WiMax chip and will be extended to support other Sequans fixed and mobile chips.
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