From 327aa97cfdfc28f687047aa1f6ea5d4ccb8206e8 Mon Sep 17 00:00:00 2001
From: Andre Puschmann <andre@softwareradiosystems.com>
Date: Wed, 12 Feb 2020 17:40:47 +0100
Subject: [PATCH] add macro for invalid RNTI 0x0

---
 lib/include/srslte/phy/common/phy_common.h | 1 +
 srsue/src/phy/cc_worker.cc                 | 5 ++---
 srsue/src/stack/mac/mac.cc                 | 9 ++++++---
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/lib/include/srslte/phy/common/phy_common.h b/lib/include/srslte/phy/common/phy_common.h
index cb76fe219..fafc9b8c9 100644
--- a/lib/include/srslte/phy/common/phy_common.h
+++ b/lib/include/srslte/phy/common/phy_common.h
@@ -71,6 +71,7 @@
 typedef enum { SRSLTE_CP_NORM = 0, SRSLTE_CP_EXT } srslte_cp_t;
 typedef enum { SRSLTE_SF_NORM = 0, SRSLTE_SF_MBSFN } srslte_sf_t;
 
+#define SRSLTE_INVALID_RNTI 0x0 // TS 36.321 - Table 7.1-1 RNTI 0x0 isn't a valid DL RNTI
 #define SRSLTE_CRNTI_START 0x000B
 #define SRSLTE_CRNTI_END 0xFFF3
 #define SRSLTE_RARNTI_START 0x0001
diff --git a/srsue/src/phy/cc_worker.cc b/srsue/src/phy/cc_worker.cc
index fd2d49873..618ee8df4 100644
--- a/srsue/src/phy/cc_worker.cc
+++ b/srsue/src/phy/cc_worker.cc
@@ -370,10 +370,9 @@ int cc_worker::decode_pdcch_dl()
 {
   int nof_grants = 0;
 
-  srslte_dci_dl_t dci[SRSLTE_MAX_CARRIERS] = {};
-
   uint16_t dl_rnti = phy->stack->get_dl_sched_rnti(CURRENT_TTI);
-  if (dl_rnti) {
+  if (dl_rnti != SRSLTE_INVALID_RNTI) {
+    srslte_dci_dl_t dci[SRSLTE_MAX_CARRIERS] = {};
 
     /* Blind search first without cross scheduling then with it if enabled */
     for (int i = 0; i < (ue_dl_cfg.cfg.dci.cif_present ? 2 : 1) && !nof_grants; i++) {
diff --git a/srsue/src/stack/mac/mac.cc b/srsue/src/stack/mac/mac.cc
index 3ba84d59e..a9ada3f7c 100644
--- a/srsue/src/stack/mac/mac.cc
+++ b/srsue/src/stack/mac/mac.cc
@@ -291,7 +291,8 @@ uint16_t mac::get_ul_sched_rnti(uint32_t tti)
   if (uernti.crnti) {
     return uernti.crnti;
   }
-  return 0;
+  Error("Couldn't configure RNTI for UL transmission.\n");
+  return SRSLTE_INVALID_RNTI;
 }
 
 bool mac::is_in_window(uint32_t tti, int* start, int* len)
@@ -329,7 +330,7 @@ uint16_t mac::get_dl_sched_rnti(uint32_t tti)
       // TODO: This scheduling decision belongs to RRC
       if (si_window_length > 1) {                     // This is not a SIB1
         if ((tti / 10) % 2 == 0 && (tti % 10) == 5) { // Skip subframe #5 for which SFN mod 2 = 0
-          return 0;
+          return SRSLTE_INVALID_RNTI;
         }
       }
       Debug("SCHED: Searching SI-RNTI, tti=%d, window start=%d, length=%d\n", tti, si_window_start, si_window_length);
@@ -352,7 +353,9 @@ uint16_t mac::get_dl_sched_rnti(uint32_t tti)
     Debug("SCHED: Searching P-RNTI\n");
     return SRSLTE_PRNTI;
   }
-  return 0;
+
+  // turn off DCI search for this TTI
+  return SRSLTE_INVALID_RNTI;
 }
 
 void mac::bch_decoded_ok(uint8_t* payload, uint32_t len)