2-2 Fixed WiMAX Measurements Chapter 2 —Fixed WiMAX Signal Analyzer
2-2 PN: 10580-00236 Rev. D WiMAX MG
Freq Error
The difference between the measured carrier frequency and the specified carrier frequency is
the frequency error. This number is only as accurate as the frequency reference that is used.
Frequency error is displayed in both Hz and ppm. Option 31 (GPS Receiver) can be used for
improved frequency accuracy when an external reference is not available at a BTS.
EVM (Error Vector Magnitude)
The Error Vector Magnitude (in percent) displays the difference between the reference
waveform and the measured waveform, and then EVM is normalized.
Relative Constellation Error (RCE)
Relative Constellation Error is similar to EVM but is expressed in dB (RCE = 20 log(EVM)
where EVM is expressed in %⁄100) Both rms and peak values over an entire downlink
subframe are displayed.
Carrier Frequency
Carrier Frequency is the measured frequency of the input signal after demodulation, and is
the same as the tuned Center Frequency of the instrument plus the measured Frequency
Error from demodulation.
Base Station ID
Each transmitter has a unique ID of 48 bits. These instruments display the ID as Base
Station ID by decoding the FCH (Frame Control Header), the lower significant bits (LSB) of
4 bits of the downlink frame.
Adjacent Subcarrier Flatness (Peak)
Adjacent Subcarrier Flatness is the absolute difference between the adjacent sub carriers.
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