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openairinterface5g/openair1/PHY/LTE_TRANSPORT/pcfich.c
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/*******************************************************************************
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@lists.eurecom.fr
Address : Eurecom, Campus SophiaTech, 450 Route des Chappes, CS 50193 - 06904 Biot Sophia Antipolis cedex, FRANCE
*******************************************************************************/
/*! \file PHY/LTE_TRANSPORT/pcfich.c
* \brief Top-level routines for generating and decoding the PCFICH/CFI physical/transport channel V8.6 2009-03
* \author R. Knopp
* \date 2011
* \version 0.1
* \company Eurecom
* \email: knopp@eurecom.fr
* \note
* \warning
*/
#include "PHY/defs.h"
#include "MAC_INTERFACE/extern.h"
//uint16_t pcfich_reg[4];
//uint8_t pcfich_first_reg_idx = 0;
//#define DEBUG_PCFICH
void generate_pcfich_reg_mapping(LTE_DL_FRAME_PARMS *frame_parms)
{
uint16_t kbar = 6 * (frame_parms->Nid_cell %(2*frame_parms->N_RB_DL));
uint16_t first_reg;
uint16_t *pcfich_reg = frame_parms->pcfich_reg;
pcfich_reg[0] = kbar/6;
first_reg = pcfich_reg[0];
frame_parms->pcfich_first_reg_idx=0;
pcfich_reg[1] = ((kbar + (frame_parms->N_RB_DL>>1)*6)%(frame_parms->N_RB_DL*12))/6;
if (pcfich_reg[1] < pcfich_reg[0]) {
frame_parms->pcfich_first_reg_idx = 1;
first_reg = pcfich_reg[1];
}
pcfich_reg[2] = ((kbar + (frame_parms->N_RB_DL)*6)%(frame_parms->N_RB_DL*12))/6;
if (pcfich_reg[2] < first_reg) {
frame_parms->pcfich_first_reg_idx = 2;
first_reg = pcfich_reg[2];
}
pcfich_reg[3] = ((kbar + ((3*frame_parms->N_RB_DL)>>1)*6)%(frame_parms->N_RB_DL*12))/6;
if (pcfich_reg[3] < first_reg) {
frame_parms->pcfich_first_reg_idx = 3;
first_reg = pcfich_reg[3];
}
//#ifdef DEBUG_PCFICH
printf("pcfich_reg : %d,%d,%d,%d\n",pcfich_reg[0],pcfich_reg[1],pcfich_reg[2],pcfich_reg[3]);
//#endif
}
void pcfich_scrambling(LTE_DL_FRAME_PARMS *frame_parms,
uint8_t subframe,
uint8_t *b,
uint8_t *bt)
{
uint32_t i;
uint8_t reset;
uint32_t x1, x2, s=0;
reset = 1;
// x1 is set in lte_gold_generic
x2 = ((((2*frame_parms->Nid_cell)+1)*(1+subframe))<<9) + frame_parms->Nid_cell; //this is c_init in 36.211 Sec 6.7.1
for (i=0; i<32; i++) {
if ((i&0x1f)==0) {
s = lte_gold_generic(&x1, &x2, reset);
//printf("lte_gold[%d]=%x\n",i,s);
reset = 0;
}
bt[i] = (b[i]&1) ^ ((s>>(i&0x1f))&1);
// printf("scrambling %d : b %d => bt %d, c %d\n",i,b[i],bt[i],((s>>(i&0x1f))&1));
}
}
void pcfich_unscrambling(LTE_DL_FRAME_PARMS *frame_parms,
uint8_t subframe,
int16_t *d)
{
uint32_t i;
uint8_t reset;
uint32_t x1, x2, s=0;
reset = 1;
// x1 is set in lte_gold_generic
x2 = ((((2*frame_parms->Nid_cell)+1)*(1+subframe))<<9) + frame_parms->Nid_cell; //this is c_init in 36.211 Sec 6.7.1
for (i=0; i<32; i++) {
if ((i&0x1f)==0) {
s = lte_gold_generic(&x1, &x2, reset);
//printf("lte_gold[%d]=%x\n",i,s);
reset = 0;
}
if (((s>>(i&0x1f))&1) == 1)
d[i]=-d[i];
// printf("scrambling %d : b %d => bt %d, c %d\n",i,b[i],bt[i],((s>>(i&0x1f))&1));
}
}
uint8_t pcfich_b[4][32]= {{0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1},
{1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0},
{1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1},
{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}
};
void generate_pcfich(uint8_t num_pdcch_symbols,
int16_t amp,
LTE_DL_FRAME_PARMS *frame_parms,
mod_sym_t **txdataF,
uint8_t subframe)
{
uint8_t pcfich_bt[32],nsymb,pcfich_quad;
mod_sym_t pcfich_d[2][16];
uint8_t i;
uint32_t symbol_offset,m,re_offset,reg_offset;
int16_t gain_lin_QPSK;
uint16_t *pcfich_reg = frame_parms->pcfich_reg;
int nushiftmod3 = frame_parms->nushift%3;
#ifdef DEBUG_PCFICH
msg("[PHY] Generating PCFICH for %d PDCCH symbols, AMP %d\n",num_pdcch_symbols,amp);
#endif
// scrambling
if ((num_pdcch_symbols>0) && (num_pdcch_symbols<4))
pcfich_scrambling(frame_parms,subframe,pcfich_b[num_pdcch_symbols-1],pcfich_bt);
// modulation
if (frame_parms->mode1_flag==1)
gain_lin_QPSK = (int16_t)((amp*ONE_OVER_SQRT2_Q15)>>15);
else
gain_lin_QPSK = amp/2;
if (frame_parms->mode1_flag) { // SISO
for (i=0; i<16; i++) {
((int16_t*)(&(pcfich_d[0][i])))[0] = ((pcfich_bt[2*i] == 1) ? -gain_lin_QPSK : gain_lin_QPSK);
((int16_t*)(&(pcfich_d[1][i])))[0] = ((pcfich_bt[2*i] == 1) ? -gain_lin_QPSK : gain_lin_QPSK);
((int16_t*)(&(pcfich_d[0][i])))[1] = ((pcfich_bt[2*i+1] == 1) ? -gain_lin_QPSK : gain_lin_QPSK);
((int16_t*)(&(pcfich_d[1][i])))[1] = ((pcfich_bt[2*i+1] == 1) ? -gain_lin_QPSK : gain_lin_QPSK);
}
} else { // ALAMOUTI
for (i=0; i<16; i+=2) {
// first antenna position n -> x0
((int16_t*)(&(pcfich_d[0][i])))[0] = ((pcfich_bt[2*i] == 1) ? -gain_lin_QPSK : gain_lin_QPSK);
((int16_t*)(&(pcfich_d[0][i])))[1] = ((pcfich_bt[2*i+1] == 1) ? -gain_lin_QPSK : gain_lin_QPSK);
// second antenna position n -> -x1*
((int16_t*)(&(pcfich_d[1][i])))[0] = ((pcfich_bt[2*i+2] == 1) ? gain_lin_QPSK : -gain_lin_QPSK);
((int16_t*)(&(pcfich_d[1][i])))[1] = ((pcfich_bt[2*i+3] == 1) ? -gain_lin_QPSK : gain_lin_QPSK);
// fill in the rest of the ALAMOUTI precoding
((int16_t*)&pcfich_d[0][i+1])[0] = -((int16_t*)&pcfich_d[1][i])[0];
((int16_t*)&pcfich_d[0][i+1])[1] = ((int16_t*)&pcfich_d[1][i])[1];
((int16_t*)&pcfich_d[1][i+1])[0] = ((int16_t*)&pcfich_d[0][i])[0];
((int16_t*)&pcfich_d[1][i+1])[1] = -((int16_t*)&pcfich_d[0][i])[1];
}
}
// mapping
nsymb = (frame_parms->Ncp==0) ? 14:12;
symbol_offset = (uint32_t)frame_parms->ofdm_symbol_size*((subframe*nsymb));
re_offset = frame_parms->first_carrier_offset;
// loop over 4 quadruplets and lookup REGs
m=0;
for (pcfich_quad=0; pcfich_quad<4; pcfich_quad++) {
reg_offset = re_offset+((uint16_t)pcfich_reg[pcfich_quad]*6);
if (reg_offset>=frame_parms->ofdm_symbol_size)
reg_offset=1 + reg_offset-frame_parms->ofdm_symbol_size;
// printf("mapping pcfich reg_offset %d\n",reg_offset);
for (i=0; i<6; i++) {
if ((i!=nushiftmod3)&&(i!=(nushiftmod3+3))) {
txdataF[0][symbol_offset+reg_offset+i] = pcfich_d[0][m];
if (frame_parms->nb_antennas_tx_eNB>1)
txdataF[1][symbol_offset+reg_offset+i] = pcfich_d[1][m];
m++;
}
}
}
}
uint8_t rx_pcfich(LTE_DL_FRAME_PARMS *frame_parms,
uint8_t subframe,
LTE_UE_PDCCH *lte_ue_pdcch_vars,
MIMO_mode_t mimo_mode)
{
uint8_t pcfich_quad;
uint8_t i,j;
uint16_t reg_offset;
int32_t **rxdataF_comp = lte_ue_pdcch_vars->rxdataF_comp;
int16_t pcfich_d[32],*pcfich_d_ptr;
int32_t metric,old_metric=-16384;
uint8_t num_pdcch_symbols=3;
uint16_t *pcfich_reg = frame_parms->pcfich_reg;
// demapping
// loop over 4 quadruplets and lookup REGs
// m=0;
pcfich_d_ptr = pcfich_d;
for (pcfich_quad=0; pcfich_quad<4; pcfich_quad++) {
reg_offset = (pcfich_reg[pcfich_quad]*4);
// if (frame_parms->mode1_flag==1) { // SISO
for (i=0; i<4; i++) {
pcfich_d_ptr[0] = ((int16_t*)&rxdataF_comp[0][reg_offset+i])[0]; // RE component
pcfich_d_ptr[1] = ((int16_t*)&rxdataF_comp[0][reg_offset+i])[1]; // IM component
/*
printf("rx_pcfich: quad %d, i %d, offset %d => m%d (%d,%d) => pcfich_d_ptr[0] %d \n",pcfich_quad,i,reg_offset+i,m,
((int16_t*)&rxdataF_comp[0][reg_offset+i])[0],
((int16_t*)&rxdataF_comp[0][reg_offset+i])[1],
pcfich_d_ptr[0]);
*/
pcfich_d_ptr+=2;
}
/*
}
else { // ALAMOUTI
for (i=0;i<4;i+=2) {
pcfich_d_ptr[0] = 0;
pcfich_d_ptr[1] = 0;
pcfich_d_ptr[2] = 0;
pcfich_d_ptr[3] = 0;
for (j=0;j<frame_parms->nb_antennas_rx;j++) {
pcfich_d_ptr[0] += (((int16_t*)&rxdataF_comp[j][reg_offset+i])[0]+
((int16_t*)&rxdataF_comp[j+2][reg_offset+i+1])[0]); // RE component
pcfich_d_ptr[1] += (((int16_t*)&rxdataF_comp[j][reg_offset+i])[1] -
((int16_t*)&rxdataF_comp[j+2][reg_offset+i+1])[1]);// IM component
pcfich_d_ptr[2] += (((int16_t*)&rxdataF_comp[j][reg_offset+i+1])[0]-
((int16_t*)&rxdataF_comp[j+2][reg_offset+i])[0]); // RE component
pcfich_d_ptr[3] += (((int16_t*)&rxdataF_comp[j][reg_offset+i+1])[1] +
((int16_t*)&rxdataF_comp[j+2][reg_offset+i])[1]);// IM component
}
pcfich_d_ptr+=4;
}
*/
}
// pcfhich unscrambling
pcfich_unscrambling(frame_parms,subframe,pcfich_d);
// pcfich detection
for (i=0; i<3; i++) {
metric = 0;
for (j=0; j<32; j++) {
//printf("pcfich_b[%d][%d] %d => pcfich_d[%d] %d\n",i,j,pcfich_b[i][j],j,pcfich_d[j]);
metric += (int32_t)(((pcfich_b[i][j]==0) ? (pcfich_d[j]) : (-pcfich_d[j])));
}
#ifdef DEBUG_PCFICH
msg("metric %d : %d\n",i,metric);
#endif
if (metric > old_metric) {
num_pdcch_symbols = 1+i;
old_metric = metric;
}
}
#ifdef DEBUG_PCFICH
msg("[PHY] PCFICH detected for %d PDCCH symbols\n",num_pdcch_symbols);
#endif
return(num_pdcch_symbols);
}
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