Demand for test solutions in the communications and wireless sector continues to soar. Not only has there been an explosion in the adoption rate of new wireless technologies, but couple that with tough standards, multiple radios per product, and millions of devices to test, and it quickly becomes evident that testing capability is critical to the success of any wireless device today.
Not to fret, though. Test and measurement companies are on top of the situation. A steady stream of new equipment and software continues to flow into the hands of engineers to help test almost any wireless product.
WI-FI TESTING
David Hall, National Instruments’ RF & communications product manager, thinks that the two most influential factors impacting new test equipment are systems-on-a-chip (SoCs) and the need for shorter test times.
The latest wireless SoCs put a complete transceiver and all ancillary circuits on a chip. In fact, it’s common to see multiple radios per chip. Just look at the combo chips that put Wi-Fi, Bluetooth, GPS, and an FM radio, or some combination thereof, on a single chip for advanced cell phones. How does one test that chip after it’s manufactured and in the handset?
Second, with fewer circuits in a product, the cost of that product is being influenced more and more by the amount of time needed to test it. Test time has grown to be a greater percentage of the cost than the bill of materials (BOM) in some products. Hall says NI is helping to solve these problems with its software-defined approach.
NI’s Wi-Fi wireless local-area networking (WLAN) test solution can generate and analyze RF signal measurements four times faster than other modular instrumentation solutions and up to 10 times faster than traditional box instruments. It combines the NI WLAN Measurement Suite software for the LabVIEW and LabWindows/CVI development environment with the NI 6.6-GHz PXI Express RF hardware to deliver increased speed and flexibility for testing IEEE 802.11a/b/g standards.
Because this solution is software-defined, engineers can easily configure the same measurement hardware to test more than six other RF communications standards, including Bluetooth, GPS, RFID, and WiMAX. It comprises the NI PXIe-5663 6.6-GHz RF vector signal analyzer, the PXIe-5673 6.6-GHz vector signal generator, the PXIe-1075 18-slot chassis, and the PXIe-8106 dual core controller (Fig. 1).
The software component consists of the NI WLAN Generation Toolkit and the WLAN Analysis Toolkit. Both come with several example programs to help you get started quickly with automated test applications. Physical-layer (PHY) measurements like power, error vector magnitude (EVM), and spectrum mask margin can be made up to 10 times faster than available alternative measurement solutions. For example, an EVM measurement can be done in as little as 8 ms.
LTE TESTING
Perhaps the hottest area in wireless test is equipment and software for testing Long-Term Evolution (LTE) 4G cellular products. Basestation and handset manufacturers are now making the products for LTE, which may show up as early as next year. LTE is a complex wireless technology that requires leading-edge test equipment to ensure compliance with the new 3GPP standard as well as country regulatory requirements.
Anritsu showed off a promising LTE tester at April’s International CTIA Wireless conference in Las Vegas. It won second place in the 4G Service Creation & Development category of the show’s E-Tech Awards. The MD8430A Signalling Tester, an LTE basestation simulator, is designed for users who need to test wireless LTE chips and mobile end products like handsets (Fig. 2).
Thanks to the MD8430A’s four RF units, it can be used for 2x2 multiple-input multiple-output (MIMO) testing, including system handover tests in a simulated network environment. The simulator can conduct end-to-end testing at downlink speeds up to 100 Mbits/s and uplink speeds to 50 Mbits/s.
All critical 3GPP air interface LTE protocol tests are supported, including baseband coding/decoding; processing tests; protocol sequence tests such as position registration, origination, termination, handover, terminal, and network disconnect tests; and applications tests. L1 and L2 cache analysis functions are also provided. Moreover, the unit supports handover tests with UTRAN/GERAN systems.
The MD8430A can be integrated with Anritsu’s MD8480C WCDMA Signal l ing Tes ter to simulate both WCDMA and HSPA (up to release 7) and GSM/ GPRS/EGPRS basestations. It’s also usable with the company’s Protocol Test System and Rapid Test Designer.
MIMO TESTING
While LTE testing is complex, it intensifies further when MIMO antenna technology is added to the mix. MIMO testing often requires multiple pieces of equipment. One of the best ways to test the MIMO capability of a device is to use a channel emulator, which is a box of hardware and software that acts like the wireless path through the ether itself.
Channel emulators can be programmed to simulate the noise, spatial differences, attenuation, multipath, and other characteristics that vary during a connection. One of the companies specializing in MIMO channel emulation, Azimuth Systems, is known for its Wi-Fi and WiMAX emulators. Yet its ACE MX MIMO system uses all of LTE’s features with orthogonal frequency-division multiplexing (OFDM) and MIMO for testing LTE products (Fig. 3).
Continue to page 2
Reprints
