98 lines
4.4 KiB
C
98 lines
4.4 KiB
C
/*
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Author: Laurent THOMAS, Open Cells for Nokia
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copyleft: OpenAirInterface Software Alliance and it's licence
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#include <stdbool.h>
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#include <errno.h>
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#include <common/utils/assertions.h>
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#include <common/utils/LOG/log.h>
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#include <common/config/config_userapi.h>
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#include <openair1/SIMULATION/TOOLS/sim.h>
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/*
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Legacy study:
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The parameters are:
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gain&loss (decay, signal power, ...)
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either a fixed gain in dB, a target power in dBm or ACG (automatic control gain) to a target average
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=> don't redo the AGC, as it was used in UE case, that must have a AGC inside the UE
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will be better to handle the "set_gain()" called by UE to apply it's gain (enable test of UE power loop)
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lin_amp = pow(10.0,.05*txpwr_dBm)/sqrt(nb_tx_antennas);
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a lot of operations in legacy, grouped in one simulation signal decay: txgain*decay*rxgain
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multi_path (auto convolution, ISI, ...)
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either we regenerate the channel (call again random_channel(desc,0)), or we keep it over subframes
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legacy: we regenerate each sub frame in UL, and each frame only in DL
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*/
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void rxAddInput( struct complex16 *input_sig, struct complex16 *after_channel_sig,
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int rxAnt,
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channel_desc_t *channelDesc,
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int nbSamples,
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uint64_t TS,
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uint32_t CirSize
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) {
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// channelDesc->path_loss_dB should contain the total path gain
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// so, in actual RF: tx gain + path loss + rx gain (+antenna gain, ...)
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// UE and NB gain control to be added
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// Fixme: not sure when it is "volts" so dB is 20*log10(...) or "power", so dB is 10*log10(...)
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const double pathLossLinear = pow(10,channelDesc->path_loss_dB/20.0);
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// Energy in one sample to calibrate input noise
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//Fixme: modified the N0W computation, not understand the origin value
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const double KT=1.38e-23*290; //Boltzman*temperature
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// sampling rate is linked to acquisition band (the input pass band filter)
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const double noise_figure_watt = KT*channelDesc->sampling_rate;
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// Fixme: how to convert a noise in Watt into a 12 bits value out of the RF ADC ?
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// the parameter "-s" is declared as SNR, but the input power is not well defined
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// −132.24 dBm is a LTE subcarrier noise, that was used in origin code (15KHz BW thermal noise)
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const double rxGain= 132.24 - channelmod_get_snr_dB();
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// sqrt(4*noise_figure_watt) is the thermal noise factor (volts)
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// fixme: the last constant is pure trial results to make decent noise
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const double noise_per_sample = sqrt(4*noise_figure_watt) * pow(10,rxGain/20) *10;
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// Fixme: we don't fill the offset length samples at begining ?
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// anyway, in today code, channel_offset=0
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const int dd = abs(channelDesc->channel_offset);
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const int nbTx=channelDesc->nb_tx;
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for (int i=0; i<((int)nbSamples-dd); i++) {
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struct complex16 *out_ptr=after_channel_sig+dd+i;
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struct complex rx_tmp= {0};
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for (int txAnt=0; txAnt < nbTx; txAnt++) {
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const struct complex *channelModel= channelDesc->ch[rxAnt+(txAnt*channelDesc->nb_rx)];
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//const struct complex *channelModelEnd=channelModel+channelDesc->channel_length;
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for (int l = 0; l<(int)channelDesc->channel_length; l++) {
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// let's assume TS+i >= l
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// fixme: the rfsimulator current structure is interleaved antennas
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// this has been designed to not have to wait a full block transmission
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// but it is not very usefull
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// it would be better to split out each antenna in a separate flow
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// that will allow to mix ru antennas freely
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struct complex16 tx16=input_sig[((TS+i-l)*nbTx+txAnt)%CirSize];
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rx_tmp.x += tx16.r * channelModel[l].x - tx16.i * channelModel[l].y;
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rx_tmp.y += tx16.i * channelModel[l].x + tx16.r * channelModel[l].y;
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} //l
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}
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out_ptr->r += round(rx_tmp.x*pathLossLinear + noise_per_sample*gaussdouble(0.0,1.0));
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out_ptr->i += round(rx_tmp.y*pathLossLinear + noise_per_sample*gaussdouble(0.0,1.0));
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out_ptr++;
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}
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if ( (TS*nbTx)%CirSize+nbSamples <= CirSize )
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// Cast to a wrong type for compatibility !
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LOG_D(HW,"Input power %f, output power: %f, channel path loss %f, noise coeff: %f \n",
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10*log10((double)signal_energy((int32_t *)&input_sig[(TS*nbTx)%CirSize], nbSamples)),
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10*log10((double)signal_energy((int32_t *)after_channel_sig, nbSamples)),
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channelDesc->path_loss_dB,
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10*log10(noise_per_sample));
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}
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