• Parminder Singh's avatar
    Common Phase error estimation and compensation in uplink. · b288eafd
    Parminder Singh authored
    FEATURE STATEMENT:
    - Introduce linear phase error noise model in Uplink at UE
    - Perform common phase error (CPE) estimation and compensation at gNB
    
    SOLUTION:
    - A linear phase shift model is introduced in simulation.
    - PTRS symbols are used to perform estimation of CPE from DMRS compensated signal
    - The estimated values are interpolated in time domain and signal is compensated for the CPE.
    - PTRS processing is done in Frequency Domain for each symbol in a slot and
      LLR's are calculated for each symbol accordingly.
    
    IMPLEMENTATION:
    * sim.h/channle_sim.c
    - Linear Phase Noise Generation model definition.
    * nr_ul_channel_estimation.c/nr_ul_estimation.h
    - CPE estimation from PTRS and DMRS compensated signal.
    * nr_dmrs_rx.c/nr_refsig.h
    - Regenerate PTRS symbols at gNB.
    * nr_ulsch_demodulation.c
    - Removed old PTRS processing code and move to a common PTRS processing function
    * defs_gNB.h/init.c
    - New PTRS variables definition and initialization
    * nr_ulsch_ue.c
    - Corrected PTRS parameter to get new PTRS symbols for each OFDM symbol
    
    TESTING
    * ulsim.c
    - Added Phase noise, Enable PTRS signal and verified the output.
    
    VERIFICATION
    - The LLR are rotated back with estimated CPE and no error is observed in scrambling/decoding
    b288eafd
phase_noise.c 1.54 KB
/*
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 * this work for additional information regarding copyright ownership.
 * The OpenAirInterface Software Alliance licenses this file to You under
 * the OAI Public License, Version 1.1  (the "License"); you may not use this file
 * except in compliance with the License.
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 *
 *      http://www.openairinterface.org/?page_id=698
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 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
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#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
#include  "sim.h"


/* linear phase noise model */
void phase_noise(double ts, int16_t * InRe, int16_t * InIm)
{
  double fd = 300;//0.01*30000
  static double i=0;
  double real, imag,x ,y;
  i++;
  real = cos(fd * 2 * M_PI * i * ts);
  imag = sin (fd * 2 * M_PI * i * ts);
  x = ((real * (double)InRe[0]) - (imag * (double)InIm[0])) ;
  y= ((real * (double)InIm[0]) + (imag * (double)InRe[0])) ;
  InRe[0]= (int16_t)(x);
  InIm[0]= (int16_t)(y);
}