Error Vector Time (802.11b/g DSSS/CCK/PBCC)
When 802.11b/g DSSS Direct sequence spread spectrum. The data transmission scheme (sometimes referred to as a "'modulation" scheme) used in 802.11b WLANs. DSSS uses a radio transmitter operating at a fixed centre frequency, but using a relatively broad range of frequencies, to spread data transmissions over a fixed range of the frequency band. 802.11a and 802.11g (when not operating in 802.11b mode) use Orthogonal Frequency Division Multiplexing (OFDM)./CCK complementary code keying/PBCC packet binary convolutional code Demodulation is enabled, the trace data is the error-vector, time-domain trace data over the specified measurement interval. It is the computed error vector for each corresponding chip time in the IQ measured and IQ reference signals. The data results can be viewed as Error Vector Magnitude, Error Vector Phase, only the I component or only the Q component (see Trace Data Formats below).
If normalization is OFF, the VSA displays the instantaneous magnitude for each point. If normalization is ON, the VSA displays the error vector as a percentage ( IQ Normalize explains how this percentage is derived).
Trace Data Formats
It is important to remember that the trace is a time record made up of complex, time-domain data. Each point in the time record has two components: I and Q. The following data can be viewed by selecting appropriate trace format ():
: Displays the EVM Error vector magnitude (EVM): A quality metric in digital communication systems. See the EVM metric in the Error Summary Table topic in each demodulator for more information on how EVM is calculated for that modulation format. (Error Vector Magnitude).
: Displays the I component of the error vector.
Displays the Q component of the error vector.
Displays the Error Vector Phase error.
If the is different than expected, see the troubleshooting Tips in Troubleshooting (Digital Demodulation).
See Also
