B.6 Estimation of TX chain amplitude and frequency response parameters
38.1083GPPNRRelease 17Satellite Access Node radio transmission and receptionTS
The equalizer coefficients 
and 
are determined as follows:
1. Calculate the complex ratios (amplitude and phase) of the post-FFT acquired signal 
and the post-FFT ideal signal 
, for each reference signal, over 10ms measurement interval. This process creates a set of complex ratios:
Where the post-FFT ideal signal 
is constructed by the measuring equipment according to the relevant TX specifications, using the following parameters: i.e. nominal demodulation reference signals, (all other modulation symbols are set to 0 V), nominal carrier frequency, nominal amplitude and phase for each applicable subcarrier, nominal timing.
2. Perform time averaging at each reference signal subcarrier of the complex ratios, the time-averaging length is 10ms measurement interval. Prior to the averaging of the phases 
an unwrap operation must be performed according to the following definition: The unwrap operation corrects the radian phase angles of 
by adding multiples of 2*PI when absolute phase jumps between consecutive time instances ti are greater than or equal to the jump tolerance of PI radians. This process creates an average amplitude and phase for each reference signal subcarrier (i.e. every second subcarrier).
Where N is the number of reference signal; time-domain locations ti from for each reference signal subcarrier 
.
3. The equalizer coefficients for amplitude and phase 
and 
at the reference signal subcarriers are obtained by computing the moving average in the frequency domain of the time-averaged reference signal subcarriers, i.e. every second subcarrier. The moving average window size is 19 and averaging is over the DM-RS subcarriers in the allocated RBs. For DM-RS subcarriers at or near the edge of the channel , or when the number of available DM-RS subcarriers within a set of contiguously allocated RBs is smaller than the moving average window size, the window size is reduced accordingly as per figure B.6-1.
4. Perform linear interpolation from the equalizer coefficients 
and 
to compute coefficients 
, 
for each subcarrier.
Figure B.6-1: Reference subcarrier smoothing in the frequency domain