/******************************************************************************* OpenAirInterface Copyright(c) 1999 - 2014 Eurecom OpenAirInterface is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. OpenAirInterface is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenAirInterface.The full GNU General Public License is included in this distribution in the file called "COPYING". If not, see <http://www.gnu.org/licenses/>. Contact Information OpenAirInterface Admin: openair_admin@eurecom.fr OpenAirInterface Tech : openair_tech@eurecom.fr OpenAirInterface Dev : openair4g-devel@eurecom.fr Address : Eurecom, Campus SophiaTech, 450 Route des Chappes, CS 50193 - 06904 Biot Sophia Antipolis cedex, FRANCE *******************************************************************************/ /* file: lte_est_freq_offset.c author (c): florian.kaltenberger@eurecom.fr date: 19.11.2009 */ #include "PHY/defs.h" //#define DEBUG_PHY __m128i avg128F; //compute average channel_level on each (TX,RX) antenna pair int dl_channel_level(int16_t *dl_ch, LTE_DL_FRAME_PARMS *frame_parms) { int16_t rb; __m128i *dl_ch128; int avg; //clear average level avg128F = _mm_xor_si128(avg128F,avg128F); dl_ch128=(__m128i *)dl_ch; for (rb=0;rb<frame_parms->N_RB_DL;rb++) { avg128F = _mm_add_epi32(avg128F,_mm_madd_epi16(dl_ch128[0],dl_ch128[0])); avg128F = _mm_add_epi32(avg128F,_mm_madd_epi16(dl_ch128[1],dl_ch128[1])); avg128F = _mm_add_epi32(avg128F,_mm_madd_epi16(dl_ch128[2],dl_ch128[2])); dl_ch128+=3; } avg = (((int*)&avg128F)[0] + ((int*)&avg128F)[1] + ((int*)&avg128F)[2] + ((int*)&avg128F)[3])/(frame_parms->N_RB_DL*12); _mm_empty(); _m_empty(); return(avg); } int lte_est_freq_offset(int **dl_ch_estimates, LTE_DL_FRAME_PARMS *frame_parms, int l, int* freq_offset) { int ch_offset, omega, dl_ch_shift; struct complex16 *omega_cpx; double phase_offset; int freq_offset_est; unsigned char aa; int16_t *dl_ch,*dl_ch_prev; static int first_run = 1; int coef = 1<<10; int ncoef = 32767 - coef; ch_offset = (l*(frame_parms->ofdm_symbol_size)); if ((l!=0) && (l!=(4-frame_parms->Ncp))) { msg("lte_est_freq_offset: l (%d) must be 0 or %d\n",l,4-frame_parms->Ncp); return(-1); } phase_offset = 0.0; // for (aa=0;aa<frame_parms->nb_antennas_rx*frame_parms->nb_antennas_tx;aa++) { for (aa=0;aa<1;aa++) { dl_ch = (int16_t *)&dl_ch_estimates[aa][12+ch_offset]; dl_ch_shift = 6+(log2_approx(dl_channel_level(dl_ch,frame_parms))/2); // printf("dl_ch_shift: %d\n",dl_ch_shift); if (ch_offset == 0) dl_ch_prev = (int16_t *)&dl_ch_estimates[aa][12+(4-frame_parms->Ncp)*(frame_parms->ofdm_symbol_size)]; else dl_ch_prev = (int16_t *)&dl_ch_estimates[aa][12+0]; // calculate omega = angle(conj(dl_ch)*dl_ch_prev)) // printf("Computing freq_offset\n"); omega = dot_product(dl_ch,dl_ch_prev,(frame_parms->N_RB_DL/2 - 1)*12,dl_ch_shift); //omega = dot_product(dl_ch,dl_ch_prev,frame_parms->ofdm_symbol_size,15); omega_cpx = (struct complex16*) ω // printf("omega (%d,%d)\n",omega_cpx->r,omega_cpx->i); dl_ch = (int16_t *)&dl_ch_estimates[aa][(((frame_parms->N_RB_DL/2) + 1)*12) + ch_offset]; if (ch_offset == 0) dl_ch_prev = (int16_t *)&dl_ch_estimates[aa][(((frame_parms->N_RB_DL/2) + 1)*12)+(4-frame_parms->Ncp)*(frame_parms->ofdm_symbol_size)]; else dl_ch_prev = (int16_t *)&dl_ch_estimates[aa][((frame_parms->N_RB_DL/2) + 1)*12]; // calculate omega = angle(conj(dl_ch)*dl_ch_prev)) omega = dot_product(dl_ch,dl_ch_prev,((frame_parms->N_RB_DL/2) - 1)*12,dl_ch_shift); omega_cpx->r += ((struct complex16*) &omega)->r; omega_cpx->i += ((struct complex16*) &omega)->i; // phase_offset += atan2((double)omega_cpx->i,(double)omega_cpx->r); phase_offset += atan2((double)omega_cpx->i,(double)omega_cpx->r); // LOG_D(PHY,"omega (%d,%d) -> %f\n",omega_cpx->r,omega_cpx->i,phase_offset); } // phase_offset /= (frame_parms->nb_antennas_rx*frame_parms->nb_antennas_tx); freq_offset_est = (int) (phase_offset/(2*M_PI)/(frame_parms->Ncp==NORMAL ? (285.8e-6):(2.5e-4))); //2.5e-4 is the time between pilot symbols // LOG_D(PHY,"symbol %d : freq_offset_est %d\n",l,freq_offset_est); // update freq_offset with phase_offset using a moving average filter if (first_run == 1) { *freq_offset = freq_offset_est; first_run = 0; } else *freq_offset = ((freq_offset_est * coef) + (*freq_offset * ncoef)) >> 15; //#ifdef DEBUG_PHY // msg("l=%d, phase_offset = %f (%d,%d), freq_offset_est = %d Hz, freq_offset_filt = %d \n",l,phase_offset,omega_cpx->r,omega_cpx->i,freq_offset_est,*freq_offset); /* for (i=0;i<150;i++) msg("i %d : %d,%d <=> %d,%d\n",i,dl_ch[2*i],dl_ch[(2*i)+1],dl_ch_prev[2*i],dl_ch_prev[(2*i)+1]); */ //#endif return(0); } //****************************************************************************************************** // LTE MBSFN Frequency offset estimation int lte_mbsfn_est_freq_offset(int **dl_ch_estimates, LTE_DL_FRAME_PARMS *frame_parms, int l, int* freq_offset) { int ch_offset, omega, dl_ch_shift; struct complex16 *omega_cpx; double phase_offset; int freq_offset_est; unsigned char aa; int16_t *dl_ch,*dl_ch_prev; static int first_run = 1; int coef = 1<<10; int ncoef = 32767 - coef; ch_offset = (l*(frame_parms->ofdm_symbol_size)); if ((l!=2) && (l!=6) && (l!=10)) { msg("lte_est_freq_offset: l (%d) must be 2 or 6 or 10", l); return(-1); } phase_offset = 0.0; // for (aa=0;aa<frame_parms->nb_antennas_rx*frame_parms->nb_antennas_tx;aa++) { for (aa=0;aa<1;aa++) { dl_ch = (int16_t *)&dl_ch_estimates[aa][12+ch_offset]; dl_ch_shift = 4+(log2_approx(dl_channel_level(dl_ch,frame_parms))/2); // printf("dl_ch_shift: %d\n",dl_ch_shift); if (ch_offset == 0) dl_ch_prev = (int16_t *)&dl_ch_estimates[aa][12+(10*(frame_parms->ofdm_symbol_size))]; else dl_ch_prev = (int16_t *)&dl_ch_estimates[aa][12+6]; //else if // dl_ch_prev = (int16_t *)&dl_ch_estimates[aa][12+0]; // calculate omega = angle(conj(dl_ch)*dl_ch_prev)) // printf("Computing freq_offset\n"); omega = dot_product(dl_ch,dl_ch_prev,(frame_parms->N_RB_DL/2 - 1)*12,dl_ch_shift); //omega = dot_product(dl_ch,dl_ch_prev,frame_parms->ofdm_symbol_size,15); omega_cpx = (struct complex16*) ω // printf("omega (%d,%d)\n",omega_cpx->r,omega_cpx->i); dl_ch = (int16_t *)&dl_ch_estimates[aa][(((frame_parms->N_RB_DL/2) + 1)*12) + ch_offset]; if (ch_offset == 0) dl_ch_prev = (int16_t *)&dl_ch_estimates[aa][(((frame_parms->N_RB_DL/2) + 1)*12)+10*(frame_parms->ofdm_symbol_size)]; else dl_ch_prev = (int16_t *)&dl_ch_estimates[aa][((frame_parms->N_RB_DL/2) + 1)*12+6]; // calculate omega = angle(conj(dl_ch)*dl_ch_prev)) omega = dot_product(dl_ch,dl_ch_prev,((frame_parms->N_RB_DL/2) - 1)*12,dl_ch_shift); omega_cpx->r += ((struct complex16*) &omega)->r; omega_cpx->i += ((struct complex16*) &omega)->i; // phase_offset += atan2((double)omega_cpx->i,(double)omega_cpx->r); phase_offset += atan2((double)omega_cpx->i,(double)omega_cpx->r); // printf("omega (%d,%d) -> %f\n",omega_cpx->r,omega_cpx->i,phase_offset); } // phase_offset /= (frame_parms->nb_antennas_rx*frame_parms->nb_antennas_tx); freq_offset_est = (int) (phase_offset/(2*M_PI)/2.5e-4); //2.5e-4 is the time between pilot symbols // printf("symbol %d : freq_offset_est %d\n",l,freq_offset_est); // update freq_offset with phase_offset using a moving average filter if (first_run == 1) { *freq_offset = freq_offset_est; first_run = 0; } else *freq_offset = ((freq_offset_est * coef) + (*freq_offset * ncoef)) >> 15; //#ifdef DEBUG_PHY // msg("l=%d, phase_offset = %f (%d,%d), freq_offset_est = %d Hz, freq_offset_filt = %d \n",l,phase_offset,omega_cpx->r,omega_cpx->i,freq_offset_est,*freq_offset); /* for (i=0;i<150;i++) msg("i %d : %d,%d <=> %d,%d\n",i,dl_ch[2*i],dl_ch[(2*i)+1],dl_ch_prev[2*i],dl_ch_prev[(2*i)+1]); */ //#endif return(0); }