Wireless PHY test software works in LabVIEW

SeaSolve Software Inc. (SSI) provides test-and-measurement bits supporting development of a number of IEEE-defined wireless standards. These include IEEE-802.11a/b/g, IEEE-802.15.4, and WiMax.

Significantly, SeaSolve's test suite is tightly coupled with existing—and proven—signal analyzer and signal generator hardware. This hardware comes from well-known companies such as National Instruments (NI) and Tektronix.

In this case, the company's product is intimately tied to NI's hardware as well as its popular PC-hosted LabVIEW environment. As you might expect, SSI is part of the NI Alliance Program (it's also a Tektronix OpenChoice partner, but that's another story). Finally, SSI also offers services for developing test gear based on proprietary and third-party instruments.

A toolset

The three items briefly described in the company's press release comprise a rather comprehensive set of tools that rely on PCs configured with NI's LabVIEW 7.0 (or higher). A LabVIEW workstation for SSI's tools needs to run Windows 2000, Windows NT, or Windows XP. The machine will also need to be equipped with a Gbyte of RAM (or at least 512MB), and 100MB of spare disk space.

Beyond that, you'll also need an NI PXI-5660 RF Signal Analyzer plug-in and an NI PXI-5670 RF Signal Generator. Of course, you'll also need to load the drivers for those cards. Then you'll be all set for wireless personal area network (WPAN) testing.

The WiPAN LVCT tool comprises a software test environment to exercise a WPAN DUT (device under test) to see if it meets the emerging IEEE-802.15.4 standard.

The hardware side of this tester works in the 2.4GHz PHY (physical layer). The 2.4GHz band is the ISM (industrial, scientific, medical) band where unlicensed WPAN equipment is used.

A generator and analyzer

Let's look at the WiPAN LVCT suite. It consists of a WiPAN LVSA signal analyzer and the WiPAN LVSG signal generation software. WiPAN LVCT performs ten tests on any one of sixteen RF channels that are at 5MHz intervals.

For its part, WiPAN LVSA is the LabVIEW-based signal analyzer. It's what handles both baseband and RF analysis. It captures signals, and performs EVM (error vector magnitude) calculations. WiPAN LVSA provides a realtime data display, with realtime simulation of results.

In use, you can use a zoom function to see detail, and you can automatically fit the display to a window. The system lets you examine symbol behavior with eye diagrams, and look at EVM spectrum and time plots. Constellation diagrams can also be displayed.

Time and frequency domains

Because this system works in both the time domain and the frequency domain, you can analyze changing phase, magnitude and frequency of 2.4GHz signals quite readily. In use, the Windows/LabVIEW WiPAN LVSA environment lets you do expected things such as change plot color, or add markers. But, it also displays frame lengths, and provides a way to detect packets, do offset correction, and handle channel estimation and correction, too.

The associated WiPAN LVSG baseband PHY signal generation software also provides a LabVIEW interface. Using that, the WiPAN LVSG signal generation tool, along with NI's RFSG driver, gives you a concise way to generate IEEE-802.15.4-compliant modulated baseband test signals and RF signals.

WiPAN LVSG lets you model and add impairments such as AWGN ((additive white Gaussian noise) and fading. You can also crank in frequency offsets and/or corrections, and establish I/Q (in-phase and quadrature) gain imbalances. The WiPAN LVSG tool also lets you set parms such as phase noise, quadrature skew, and DC offsets, and do things like establish power-amplifier back-offs.

In short, the suite will let you graphically evaluate parameters such as spectrum masks, EVM, transmit center-frequency tolerances, and transmit power. You can also check symbol rates, receiver RF sensitivity, adjacent channel and alternate channel jamming resistance, and Rx/Tx (receiver-transmitter) turn-around timing.

The SSI press statement says the system has a $40,000 price tag, however the software suite comprising WiPAN LVCT, WiPAN LVSA, and WiPAN LVSG is really priced at about $10,000. The total set-up that costs $40 grand includes the NI PXI plug-ins and drivers, but you may already have some of that hardware. If so, this can be a cost-effective addition to existing PC-hosted engineering software tools.

Whether you're an intellectual property developer, a chip designer or a WPAN end-equipment maker, you can likely reduce development and compliance testing time with this product. Moreover, SSI's wares can be used through many phases of a product's life cycle, from R&D through to manufacturing. Even at $40,000, it looks like it can be a cost-effective and versatile product.

- Alex Mendelsohn

eeProductCenter