Reviewed NR procedure for PUCCH resource sselection and reviewed gNb PUCCH interface

lib/include/srsran/interfaces/gnb_interfaces.h

@@ -243,10 +243,20 @@ public:
     std::array<uint8_t*, SRSRAN_MAX_TB> data = {}; ///< Data pointer
   };
 
+  /**
+   * @brief Describes a possible PUCCH candidate transmission
+   * @note The physical layer shall try decoding all the possible PUCCH candidates and report back to the stack the
+   * strongest of the candidates. This is thought to be used in the case of SR opportunities in which the UE could
+   * transmit HARQ-ACK in two possible resources.
+   */
+  struct pucch_candidate_t {
+    srsran_uci_cfg_nr_t        uci_cfg;  ///< UCI configuration for the opportunity
+    srsran_pucch_nr_resource_t resource; ///< PUCCH resource to use
+  };
+
   struct pucch_t {
-    srsran_uci_cfg_nr_t          uci_cfg;   ///< UCI configuration
-    srsran_pucch_nr_common_cfg_t pucch_cfg; ///< UE dedicated PUCCH configuration
-    srsran_pucch_nr_resource_t   resource;  ///< PUCCH resource
+    srsran_pucch_nr_common_cfg_t                          pucch_cfg;  ///< UE dedicated PUCCH configuration
+    srsran::bounded_vector<pucch_candidate_t, MAX_GRANTS> candidates; ///< PUCCH candidates to decode
   };
 
   struct ul_sched_t {

lib/src/phy/phch/ra_ul_nr.c

@@ -528,10 +528,9 @@ int srsran_ra_ul_nr_pucch_resource(const srsran_pucch_nr_hl_cfg_t* pucch_cfg,
 
   // Use SR PUCCH resource
   // - At least one positive SR
-  // - up to 2 HARQ-ACK
+  // - No HARQ-ACK
   // - No CSI report
-  if (uci_cfg->sr_positive_present > 0 && uci_cfg->ack.count <= SRSRAN_PUCCH_NR_FORMAT1_MAX_NOF_BITS &&
-      uci_cfg->nof_csi == 0) {
+  if (uci_cfg->sr_positive_present > 0 && uci_cfg->ack.count == 0 && uci_cfg->nof_csi == 0) {
     uint32_t sr_resource_id = uci_cfg->pucch.sr_resource_id;
     if (sr_resource_id >= SRSRAN_PUCCH_MAX_NOF_SR_RESOURCES) {
       ERROR("SR resource ID (%d) exceeds the maximum ID (%d)", sr_resource_id, SRSRAN_PUCCH_MAX_NOF_SR_RESOURCES);
@@ -550,6 +549,55 @@ int srsran_ra_ul_nr_pucch_resource(const srsran_pucch_nr_hl_cfg_t* pucch_cfg,
     return SRSRAN_SUCCESS;
   }
 
+  // Use SR PUCCH resource
+  // - At least one positive SR
+  // - up to 2 HARQ-ACK
+  // - No CSI report
+  if (uci_cfg->sr_positive_present > 0 && uci_cfg->ack.count <= SRSRAN_PUCCH_NR_FORMAT1_MAX_NOF_BITS &&
+      uci_cfg->nof_csi == 0) {
+    uint32_t sr_resource_id = uci_cfg->pucch.sr_resource_id;
+    if (sr_resource_id >= SRSRAN_PUCCH_MAX_NOF_SR_RESOURCES) {
+      ERROR("SR resource ID (%d) exceeds the maximum ID (%d)", sr_resource_id, SRSRAN_PUCCH_MAX_NOF_SR_RESOURCES);
+      return SRSRAN_ERROR;
+    }
+
+    if (!pucch_cfg->sr_resources[sr_resource_id].configured) {
+      ERROR("SR resource ID (%d) is not configured", sr_resource_id);
+      return SRSRAN_ERROR;
+    }
+
+    // Select PUCCH resource for SR
+    srsran_pucch_nr_resource_t resource_sr = pucch_cfg->sr_resources[sr_resource_id].resource;
+
+    // Select PUCCH resource for HARQ-ACK
+    srsran_pucch_nr_resource_t resource_harq = {};
+    if (ra_ul_nr_pucch_resource_hl(pucch_cfg, O_uci, uci_cfg->pucch.resource_id, &resource_harq) < SRSRAN_SUCCESS) {
+      return SRSRAN_ERROR;
+    }
+
+    // If a UE would transmit positive or negative SR in a resource using PUCCH format 0 and HARQ-ACK information bits
+    // in a resource using PUCCH format 1 in a slot, the UE transmits only a PUCCH with the HARQ-ACK information bits
+    // in the resource using PUCCH format 1.
+    if (resource_sr.format == SRSRAN_PUCCH_NR_FORMAT_0 && resource_harq.format == SRSRAN_PUCCH_NR_FORMAT_1) {
+      *resource = resource_harq;
+      return SRSRAN_SUCCESS;
+    }
+
+    // If the UE would transmit positive SR in a first resource using PUCCH format 1 and at most two HARQ-ACK
+    // information bits in a second resource using PUCCH format 1 in a slot, the UE transmits a PUCCH with HARQ-ACK
+    // information bits in the first resource using PUCCH format 1 as described in Clause 9.2.3. If a UE would transmit
+    // negative SR in a resource using PUCCH format 1 and at most two HARQ-ACK information bits in a resource using
+    // PUCCH format 1 in a slot, the UE transmits a PUCCH in the resource using PUCCH format 1 for HARQ-ACK
+    // information as described in Clause 9.2.3.
+    if (resource_sr.format == SRSRAN_PUCCH_NR_FORMAT_1 && resource_harq.format == SRSRAN_PUCCH_NR_FORMAT_1) {
+      *resource = resource_sr;
+      return SRSRAN_SUCCESS;
+    }
+
+    // The impossible happened...
+    return SRSRAN_ERROR;
+  }
+
   // Use format 2, 3 or 4 resource from higher layers
   // - Irrelevant SR opportunities
   // - More than 2 HARQ-ACK

srsenb/src/phy/nr/slot_worker.cc

@@ -149,13 +149,13 @@ bool slot_worker::work_ul()
   // For each PUCCH...
   for (stack_interface_phy_nr::pucch_t& pucch : ul_sched.pucch) {
     stack_interface_phy_nr::pucch_info_t pucch_info = {};
-    pucch_info.uci_data.cfg                         = pucch.uci_cfg;
+    pucch_info.uci_data.cfg                         = pucch.candidates[0].uci_cfg;
 
     // Decode PUCCH
     if (srsran_gnb_ul_get_pucch(&gnb_ul,
                                 &ul_slot_cfg,
                                 &pucch.pucch_cfg,
-                                &pucch.resource,
+                                &pucch.candidates[0].resource,
                                 &pucch_info.uci_data.cfg,
                                 &pucch_info.uci_data.value) < SRSRAN_SUCCESS) {
       logger.error("Error getting PUCCH");
@@ -171,7 +171,8 @@ bool slot_worker::work_ul()
     // Log PUCCH decoding
     if (logger.info.enabled()) {
       std::array<char, 512> str;
-      srsran_gnb_ul_pucch_info(&gnb_ul, &pucch.resource, &pucch_info.uci_data, str.data(), (uint32_t)str.size());
+      srsran_gnb_ul_pucch_info(
+          &gnb_ul, &pucch.candidates[0].resource, &pucch_info.uci_data, str.data(), (uint32_t)str.size());
 
       logger.info("PUCCH: %s", str.data());
     }

test/phy/dummy_gnb_stack.h

@@ -475,8 +475,8 @@ public:
     // If any UCI information is triggered, schedule PUCCH
     if (uci_cfg.ack.count > 0 || uci_cfg.nof_csi > 0 || uci_cfg.o_sr > 0) {
       mac_interface_phy_nr::pucch_t pucch = {};
-      pucch.uci_cfg                       = uci_cfg;
-      if (not phy_cfg.get_pucch_uci_cfg(slot_cfg, uci_cfg, pucch.pucch_cfg, pucch.resource)) {
+      pucch.candidates[0].uci_cfg         = uci_cfg;
+      if (not phy_cfg.get_pucch_uci_cfg(slot_cfg, uci_cfg, pucch.pucch_cfg, pucch.candidates[0].resource)) {
         logger.error("Error getting UCI CFG");
         return SRSRAN_ERROR;
       }