Automating wireless RF test
Richard A. Quinnell, Contributing Editor -- Test & Measurement World, 9/1/2005
The testing of wireless networking designs has been getting simpler as companies have begun offering specialized test equipment for the task. Wireless standards are still evolving, however, which makes it challenging for test equipment vendors to keep pace. One recent entry into the market, from National Instruments, uses a PXI-based approach that can evolve to match changes in the standards.
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| Combining SeaSolve’s WiPAN and WiLANTA measurement software with NI’s vector signal generator, vector analyzer cards, and Modulation Toolkit makes for a modular platform capable of handling a variety of wireless networking RF tests. |
The NI setup handles two wireless standards: IEEE 802.11 (WiFi) and IEEE 802.15.4 (ZigBee). The hardware consists of a PCI chassis, an NI PXI-5660 vector signal analyzer, and an NI PXI-5670/1 vector signal generator. The core of the design is not the hardware, however. It's the software.
To meet the needs of wireless networking test, NI joined forces with software developer SeaSolve Software. The SeaSolve WiPAN and WiLANTA software includes compliance test packages for both WiFi and ZigBee as well as software packages for implementing the protocols in chip designs. The SeaSolve software, combined with NI's LabView graphical development tool and NI's Modulation Toolkit, gives developers a suite of tools for developing customized wireless measurement systems.
"As product technology evolves, so does test," said Darcy Dement, product marketing manager for NI's modular test instrument team. "Often the product is software driven to enable upgrades, so the test has to be software driven, too." Dement also pointed out that the wireless networking products are evolving rapidly and that software-driven testing is the only way to keep up.
Software keeps things flexibleThe open nature of LabView-based software is a key component of NI's product offering, said Dement. "The open architecture allows you to get into the parameters so that you can do something out of the norm that standards-based testing won't." She noted that traditional instruments use firmware, so if standards change, developers must wait for the instrument maker to offer a new firmware release.
The foundation hardware, being PXI-based, is able to handle the needs of wireless testing, said NI's RF product marketing manager Joseph E. Kovacs. "These products lend themselves to test because of PXI's speed—132 Mbps. It's much faster than the 1 to 3 Mbps available over GPIB." The PXI and LabView base also means that developers will be able to use any other test software developed by members of the NI Alliance program.
The open and modular nature of the platform was a significant factor in SeaSolve's decision to port its test software to the NI system, according to SeaSolve's business development manager Nadeem Sayed. "We chose to develop this solution on the NI platform because of PXI's inherent speed advantage as well as the short time to market that the platform offers as a whole."
The modular nature also means that the hardware platform's utility is readily extended with software. For example, developers can compensate for frequency deviations in the device under test by using the Modulation Toolkit software rather than having to adjust the hardware. They also can change the filters used in the simulation of channel fading, choosing Rayleigh and Gaussian filters as well as custom ones.
The software-based platform also leaves the door open to adding other wireless system tests. One such test currently under development at SeaSolve would handle testing for the IEEE 802.16 WiMax standard. Other Alliance members are investigating GSM test using the platform.
