added cdd precoding

srslte/include/srslte/mimo/precoding.h

@@ -53,7 +53,14 @@ SRSLTE_API int srslte_precoding_single(cf_t *x,
 
 SRSLTE_API int srslte_precoding_diversity(cf_t *x[SRSLTE_MAX_LAYERS], 
                                           cf_t *y[SRSLTE_MAX_PORTS], 
-                                          int nof_ports, int nof_symbols);
+                                          int nof_ports, 
+                                          int nof_symbols);
+
+SRSLTE_API int srslte_precoding_cdd(cf_t *x[SRSLTE_MAX_LAYERS], 
+                                    cf_t *y[SRSLTE_MAX_PORTS], 
+                                    int nof_layers, 
+                                    int nof_ports, 
+                                    int nof_symbols);
 
 SRSLTE_API int srslte_precoding_type(cf_t *x[SRSLTE_MAX_LAYERS], 
                                      cf_t *y[SRSLTE_MAX_PORTS], 

srslte/lib/mimo/layermap.c

@@ -59,7 +59,7 @@ int srslte_layermap_multiplex(cf_t *d[SRSLTE_MAX_CODEWORDS], cf_t *x[SRSLTE_MAX_
     n[1] = nof_layers - n[0];
     if (nof_symbols[0] / n[0] == nof_symbols[1] / n[1]) {
 
-      srslte_layermap_diversity(d[0], x,     n[0], nof_symbols[0]);
+      srslte_layermap_diversity(d[0],  x,       n[0], nof_symbols[0]);
       srslte_layermap_diversity(d[1], &x[n[0]], n[1], nof_symbols[1]);
       return nof_symbols[0] / n[0];
 
@@ -115,11 +115,9 @@ int srslte_layermap_type(cf_t *d[SRSLTE_MAX_CODEWORDS], cf_t *x[SRSLTE_MAX_LAYER
     }
     break;
   case SRSLTE_MIMO_TYPE_SPATIAL_MULTIPLEX:
+  case SRSLTE_MIMO_TYPE_CDD:
     return srslte_layermap_multiplex(d, x, nof_cw, nof_layers, nof_symbols);
     break;
-  case SRSLTE_MIMO_TYPE_CDD:
-    fprintf(stderr, "CDD Not implemented\n");
-    return -1; 
   }
   return 0;
 }

srslte/lib/mimo/precoding.c

@@ -620,6 +620,31 @@ int srslte_precoding_diversity(cf_t *x[SRSLTE_MAX_LAYERS], cf_t *y[SRSLTE_MAX_PO
   }
 }
 
+int srslte_precoding_cdd(cf_t *x[SRSLTE_MAX_LAYERS], cf_t *y[SRSLTE_MAX_PORTS], int nof_layers, int nof_ports, int nof_symbols) 
+{
+  int i;
+  if (nof_ports == 2) {
+    if (nof_layers != 2) {
+      fprintf(stderr, "Invalid number of layers %d for 2 ports\n", nof_layers);
+      return -1; 
+    }
+    for (i = 0; i < nof_symbols; i++) {
+      y[0][i] =  (x[0][i]+x[1][i])/2;
+      y[1][i] =  (x[0][i]-x[1][i])/2;
+      i++;
+      y[0][i] =  (x[0][i]+x[1][i])/2;
+      y[1][i] = (-x[0][i]+x[1][i])/2;
+    }
+    return 2 * i;
+  } else if (nof_ports == 4) {
+    fprintf(stderr, "Not implemented\n");
+    return -1;
+  } else {
+    fprintf(stderr, "Number of ports must be 2 or 4 for transmit diversity (nof_ports=%d)\n", nof_ports);
+    return -1;
+  }
+}
+
 /* 36.211 v10.3.0 Section 6.3.4 */
 int srslte_precoding_type(cf_t *x[SRSLTE_MAX_LAYERS], cf_t *y[SRSLTE_MAX_PORTS], int nof_layers,
     int nof_ports, int nof_symbols, srslte_mimo_type_t type) {
@@ -637,8 +662,7 @@ int srslte_precoding_type(cf_t *x[SRSLTE_MAX_LAYERS], cf_t *y[SRSLTE_MAX_PORTS],
 
   switch (type) {
   case SRSLTE_MIMO_TYPE_CDD:
-    fprintf(stderr, "CCD not supported\n");
-    return -1; 
+    return srslte_precoding_cdd(x, y, nof_layers, nof_ports, nof_symbols); 
   case SRSLTE_MIMO_TYPE_SINGLE_ANTENNA:
     if (nof_ports == 1 && nof_layers == 1) {
       return srslte_precoding_single(x[0], y[0], nof_symbols);