Added option in pdsch_ue for experimental robust MMSE equalization (currently not working)

srslte/examples/pdsch_ue.c

@@ -39,7 +39,6 @@
 
 #include "srslte/srslte.h"
 
-
 #ifndef DISABLE_RF
 #include "srslte/rf/rf.h"
 #include "srslte/rf/rf_utils.h"
@@ -75,6 +74,7 @@ typedef struct {
   bool disable_plots;
   bool disable_plots_except_constellation;
   bool disable_cfo; 
+  bool use_robust_lmmse; 
   uint32_t time_offset; 
   int force_N_id_2;
   uint16_t rnti;
@@ -95,6 +95,7 @@ typedef struct {
 
 void args_default(prog_args_t *args) {
   args->disable_plots = false; 
+  args->use_robust_lmmse = false; 
   args->disable_plots_except_constellation = false; 
   args->nof_subframes = -1;
   args->rnti = SRSLTE_SIRNTI;
@@ -117,7 +118,7 @@ void args_default(prog_args_t *args) {
 }
 
 void usage(prog_args_t *args, char *prog) {
-  printf("Usage: %s [agpPoOcildDnruv] -f rx_frequency (in Hz) | -i input_file\n", prog);
+  printf("Usage: %s [agpPoOcilLdDnruv] -f rx_frequency (in Hz) | -i input_file\n", prog);
 #ifndef DISABLE_RF
   printf("\t-a RF args [Default %s]\n", args->rf_args);
   printf("\t-g RF fix RX gain [Default AGC]\n");
@@ -132,6 +133,7 @@ void usage(prog_args_t *args, char *prog) {
   printf("\t-c cell_id for input file [Default %d]\n", args->file_cell_id);
   printf("\t-r RNTI in Hex [Default 0x%x]\n",args->rnti);
   printf("\t-l Force N_id_2 [Default best]\n");
+  printf("\t-L (Experimental) Use Robust LMMSE estimation [Default false]\n");
   printf("\t-C Disable CFO correction [Default %s]\n", args->disable_cfo?"Disabled":"Enabled");
   printf("\t-t Add time offset [Default %d]\n", args->time_offset);
 #ifndef DISABLE_GRAPHICS
@@ -151,7 +153,7 @@ void usage(prog_args_t *args, char *prog) {
 void parse_args(prog_args_t *args, int argc, char **argv) {
   int opt;
   args_default(args);
-  while ((opt = getopt(argc, argv, "aoglipPcOCtdDnvrfuUsS")) != -1) {
+  while ((opt = getopt(argc, argv, "aoglLipPcOCtdDnvrfuUsS")) != -1) {
     switch (opt) {
     case 'i':
       args->input_file_name = argv[optind];
@@ -195,6 +197,9 @@ void parse_args(prog_args_t *args, int argc, char **argv) {
     case 'l':
       args->force_N_id_2 = atoi(argv[optind]);
       break;
+    case 'L':
+      args->use_robust_lmmse = true; 
+      break;
     case 'u':
       args->net_port = atoi(argv[optind]);
       break;
@@ -408,6 +413,11 @@ int main(int argc, char **argv) {
   /* Configure downlink receiver for the SI-RNTI since will be the only one we'll use */
   srslte_ue_dl_set_rnti(&ue_dl, prog_args.rnti); 
   
+  /* (Experimental) setup robust LMMSE estimation */
+  if (prog_args.use_robust_lmmse) {
+    srslte_chest_dl_set_robust_mmse_filter(&ue_dl.chest);
+  }
+
   /* Initialize subframe counter */
   sf_cnt = 0;
 

srslte/include/srslte/ch_estimation/chest_dl.h

@@ -83,6 +83,8 @@ SRSLTE_API void srslte_chest_dl_free(srslte_chest_dl_t *q);
 SRSLTE_API void srslte_chest_dl_set_filter_w(srslte_chest_dl_t *q, 
                                              cf_t *w); 
 
+SRSLTE_API void srslte_chest_dl_set_robust_mmse_filter(srslte_chest_dl_t *q); 
+
 SRSLTE_API int srslte_chest_dl_estimate(srslte_chest_dl_t *q, 
                                         cf_t *input,
                                         cf_t *ce[SRSLTE_MAX_PORTS],

srslte/lib/ch_estimation/src/chest_dl.c

@@ -41,6 +41,9 @@
 
 #define ESTIMATE_NOISE_LS_PSS
 
+#include "robust_mmse_25prb.h"
+#include "robust_mmse_50prb.h"
+
 /** 3GPP LTE Downlink channel estimator and equalizer. 
  * Estimates the channel in the resource elements transmitting references and interpolates for the rest
  * of the resource grid. 
@@ -132,6 +135,18 @@ void srslte_chest_dl_set_filter_w(srslte_chest_dl_t *q, cf_t *w) {
   q->w_filter = w; 
 }
 
+void srslte_chest_dl_set_robust_mmse_filter(srslte_chest_dl_t *q) {
+  if (q->cell.nof_prb == 25) {
+    printf("Using robust LMMSE interpolation filter\n");
+    srslte_chest_dl_set_filter_w(q, (cf_t*) w_robust_25prb);
+  } else if (q->cell.nof_prb == 50) {
+    printf("Using robust LMMSE interpolation filter\n");
+    srslte_chest_dl_set_filter_w(q, (cf_t*) w_robust_50prb);
+  } else {
+    fprintf(stderr, "Error setting robust MMSE filter. Not available for %d PRB\n", q->cell.nof_prb);
+  }
+}
+
 /* Uses the difference between the averaged and non-averaged pilot estimates */
 static float estimate_noise_pilots(srslte_chest_dl_t *q, cf_t *ce, uint32_t port_id) 
 {
@@ -215,7 +230,7 @@ static void interpolate_filter_pilots(srslte_chest_dl_t *q, cf_t *pilot_estimate
       srslte_interp_linear_vector(&q->srslte_interp_linvec, &cesymb(0), &cesymb(3), &cesymb(1), 2);
       srslte_interp_linear_vector(&q->srslte_interp_linvec, &cesymb(3), &cesymb(6), &cesymb(4), 2);
       srslte_interp_linear_vector(&q->srslte_interp_linvec, &cesymb(6), &cesymb(9), &cesymb(7), 2);
-      srslte_interp_linear_vector(&q->srslte_interp_linvec, &cesymb(6), &cesymb(9), &cesymb(9), 2);
+      srslte_interp_linear_vector2(&q->srslte_interp_linvec, &cesymb(6), &cesymb(9), &cesymb(9), &cesymb(10), 2);
     } else {
       srslte_interp_linear_vector(&q->srslte_interp_linvec, &cesymb(7), &cesymb(1), &cesymb(0), 1);
       srslte_interp_linear_vector(&q->srslte_interp_linvec, &cesymb(1), &cesymb(7), &cesymb(2), 5);
@@ -255,7 +270,7 @@ static void interpolate_pilots(srslte_chest_dl_t *q, cf_t *pilot_estimates, cf_t
       srslte_interp_linear_vector(&q->srslte_interp_linvec, &cesymb(0), &cesymb(3), &cesymb(1), 2);
       srslte_interp_linear_vector(&q->srslte_interp_linvec, &cesymb(3), &cesymb(6), &cesymb(4), 2);
       srslte_interp_linear_vector(&q->srslte_interp_linvec, &cesymb(6), &cesymb(9), &cesymb(7), 2);
-      srslte_interp_linear_vector(&q->srslte_interp_linvec, &cesymb(6), &cesymb(9), &cesymb(9), 2);
+      srslte_interp_linear_vector2(&q->srslte_interp_linvec, &cesymb(6), &cesymb(9), &cesymb(9), &cesymb(10), 2);
     } else {
       srslte_interp_linear_vector(&q->srslte_interp_linvec, &cesymb(7), &cesymb(1), &cesymb(0), 1);
       srslte_interp_linear_vector(&q->srslte_interp_linvec, &cesymb(1), &cesymb(7), &cesymb(2), 5);

srslte/lib/phch/src/cqi.c

@@ -141,7 +141,7 @@ bool srslte_cqi_send(uint32_t I_cqi_pmi, uint32_t tti) {
 /* SNR-to-CQI conversion, got from "Downlink SNR to CQI Mapping for Different Multiple Antenna Techniques in LTE"
  * Table III. 
 */
-static float cqi_to_snr_table[15] = { 1.95, 4, 6, 8, 10, 11.95, 14.05, 16, 17.9, 19.9, 21.5, 23.45, 25.0, 27.30, 29};
+static float cqi_to_snr_table[15] = { 1.95, 4, 6, 8, 10, 11.95, 14.05, 16, 17.9, 19.9, 21.5, 24, 26, 28, 30};
 
 uint8_t srslte_cqi_from_snr(float snr)
 {