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WLAN test suite runs on Windows PCs

Posted: 28 Apr 2005 ?? ?Print Version ?Bookmark and Share

Keywords:wlan? wireless local area network? lyocom? software? test suite?

Offering a suite of software tools that can help generate and analyze WLAN (wireless local area network) signals, Lyocom now provides a range of testing capabilities that can run on PC platforms.

The software runs on any PC running the Windows 2000 or Windows XP operating system. On the hardware side, Lycocom's new Test Suite works with instruments from national instruments and Ascor. The combination provides signal generation and measurement capabilities.

Automated testing

The Lyocom Test Suite uses multiple GUIs (graphical user interfaces), and includes four National Instruments labview tool sets; these facilitate automated testing using Windows's drag-and-drop interface.

Lycocom also claims its Test Suite costs "significantly less" than general-purpose or competing dedicated systems. The company maintains its Test Suite will maximize testing accuracy and efficiency, and do it at lower operational and update costsfrom early product development to manufacturing supportthan competitive products.

Lycocom says its Test Suite's price is currently one-third to one-half that of the most widely recognized competitive systems, and thousands of dollars less than its closest competitor's.

The software costs about $6,000. Hardware ranges from $15,500 to $39,500, depending on how you configure a system to meet your exact needs. Depending on how it's set up, the system supports all 802.11a/g OFDM, 802.11b/g DSSS and 802.11b/g CCK modulation types.

Lastly, Lycocom claims the cost-effectiveness of its system is more competitive than products from competitors Agilent Technologies or LitePoint. What's more, Lycocom claims its approach is more accurate.

Many functions

In use, the test suite's 802.11a/g OFDM controls gives you a handle on phase and amplitude tracking, symbol clock recovery, and frequency synchronization. Its I/Q (in-phase and quadrature) swap compensates for spectrum inversion by internally swapping I and Q signals. The controls also provide channel estimation. Filtering is selectable between six filter types. Filters include Barlett, Blackman, Hamming, Hann, spectrally raised cosine, and spectrally raised root cosine types.

For 802.11b/g DSSS/CCK, the analyzer also tests for symbol clock recovery, does DC offset removal, and provides an equalizer. With that, you can estimate and remove errors resulting from ISI (inter-symbol interference). Equalization is a useful tool for troubleshooting problems in a system, but it's typically turned off when testing compliance in order to maintain consistency with the IEEE-802.11b transmit modulation accuracy test. In any case, the 802.11b/g DSSS/CCK portion of the suite also does an I/Q swap, and has filtering similar to the 802.11a/g OFDM tests discussed above.

Reported info

802.11a/g OFDM reported information consists of carrier leakage reports, sub-carrier flatness reports, frequency error reports, and EVM (error vector magnitude) reports. EVM reports can also provide Pass/Fail indication for IEEE transmitter constellation error tests based on observed data rate.

Reporting also provides an indication of average power, demodulated packet data rate, and the length (in bytes) of a demodulated packet. Reports are also provided for the number of OFDM symbols of a demodulated packet.

Similarly, 802.11b/g DSSS/CCK reported information includes carrier frequency offset errors from a channel center-frequency, with Pass/Fail coverage of IEEE transmit center frequency error tests. Other reported information includes maximum observed EVM (of 1,000 chips, as defined in the IEEE spec, or the maximum EVM of the available chips if the packet contains less than 1000 chips). The software also reports RMS EVM, average power, data rate, and the number of symbols (DSSS or CCK) of a demodulated packet.

802.11a/b/g OFDM displays include display of constellations showing the demodulated positions of the signal field, data symbols, and pilot symbols in the I/Q plane.

Color codingBR>

Color displays are key to the software's usage. Data symbols are displayed in red, with pilot tones displayed in blue. Signal data/pilots are displayed in yellow.

Sub-carrier flatness is also displayed, with the relative power/sub-carrier shown as defined in the IEEE spec. Upper and lower limit lines are displayed to quickly determine if/where any sub-carrier flatness violations occur.

Preamble transients are also shown. The system displays both the amplitude and frequency variation that occurs during a short training sequence. Although the IEEE standard doesn't specify limits for preamble transients, excessive amplitude and/or frequency transients are frequently a source of interoperability problems between radios.

Carrier frequency variation is also shown, as well as amplitude variation, EVM vs. sub-carrier, and EVM vs. symbol. For 802.11b/g DSSS/CCK, the analyzer displays a constellation, shows carrier frequency variation, and EVM vs. symbol. Finally, the system's 802.11a/b/g OFDM/DSSS/CCK signal generator controls let you adjust and select data rates, packet lengths, preamble types, and filter types.

- Alex Mendelsohn

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