implemented logical channel prioritization in DL scheduler

lib/include/srslte/interfaces/sched_interface.h

@@ -105,10 +105,10 @@ public:
   };
 
   struct ue_bearer_cfg_t {
-    int priority                                          = 0;
+    int      priority                                     = 1;
-    int bsd                                               = 0;
+    uint32_t bsd                                          = 1000; // msec
-    int pbr                                               = 0;
+    uint32_t pbr                                          = -1;
-    int group                                             = 0;
+    int      group                                        = 0;
     enum direction_t { IDLE = 0, UL, DL, BOTH } direction = IDLE;
   };
 

srsenb/hdr/stack/mac/scheduler_common.h

@@ -22,12 +22,22 @@
 #ifndef SRSLTE_SCHEDULER_COMMON_H
 #define SRSLTE_SCHEDULER_COMMON_H
 
-#include "srslte/adt/interval.h"
 #include "srslte/adt/bounded_bitset.h"
+#include "srslte/adt/interval.h"
 #include "srslte/interfaces/sched_interface.h"
 
 namespace srsenb {
 
+/***********************
+ *     Constants
+ **********************/
+
+constexpr uint32_t tti_duration_ms = 1000;
+
+/***********************
+ *   Helper Types
+ **********************/
+
 //! Struct used to store possible CCE locations.
 struct sched_dci_cce_t {
   uint32_t cce_start[4][6]; ///< Stores starting CCE for each aggr level index and CCE location index

srsenb/hdr/stack/mac/scheduler_ue.h

@@ -99,8 +99,13 @@ const char* to_string(sched_interface::ue_bearer_cfg_t::direction_t dir);
 
 class lch_manager
 {
+  constexpr static uint32_t pbr_infinity = -1;
+  constexpr static uint32_t MAX_LC       = sched_interface::MAX_LC;
+
 public:
   void set_cfg(const sched_interface::ue_cfg_t& cfg_);
+  void new_tti();
+
   void config_lcid(uint32_t lcg_id, const sched_interface::ue_bearer_cfg_t& bearer_cfg);
   void ul_bsr(uint8_t lcg_id, uint32_t bsr);
   void ul_buffer_add(uint8_t lcid, uint32_t bytes);
@@ -112,22 +117,27 @@ public:
   bool is_bearer_ul(uint32_t lcid) const;
   bool is_bearer_dl(uint32_t lcid) const;
 
+  int get_dl_tx_total(uint32_t lcid) const { return get_dl_tx(lcid) + get_dl_retx(lcid); }
   int get_dl_tx(uint32_t lcid) const;
   int get_dl_retx(uint32_t lcid) const;
   int get_bsr(uint32_t lcid) const;
+  int get_max_prio_lcid() const;
 
   std::string get_bsr_text() const;
 
 private:
   struct ue_bearer_t {
-    sched_interface::ue_bearer_cfg_t cfg      = {};
+    sched_interface::ue_bearer_cfg_t cfg         = {};
-    int                              buf_tx   = 0;
+    int                              bucket_size = 0;
-    int                              buf_retx = 0;
+    int                              buf_tx      = 0;
+    int                              buf_retx    = 0;
+    int                              Bj          = 0;
   };
 
   int alloc_retx_bytes(uint8_t lcid, uint32_t rem_bytes);
   int alloc_tx_bytes(uint8_t lcid, uint32_t rem_bytes);
 
+  size_t                                           prio_idx = 0;
   srslte::log_ref                                  log_h{"MAC"};
   std::array<ue_bearer_t, sched_interface::MAX_LC> lch     = {};
   std::array<int, 4>                               lcg_bsr = {};
@@ -139,15 +149,17 @@ private:
 class sched_ue
 {
 public:
+  sched_ue();
+  void reset();
+  void init(uint16_t rnti, const std::vector<sched_cell_params_t>& cell_list_params_);
+  void new_tti(srslte::tti_point new_tti);
+
   /*************************************************************
    *
    * FAPI-like Interface
    *
    ************************************************************/
-  sched_ue();
-  void reset();
   void phy_config_enabled(uint32_t tti, bool enabled);
-  void init(uint16_t rnti, const std::vector<sched_cell_params_t>& cell_list_params_);
   void set_cfg(const sched_interface::ue_cfg_t& cfg);
 
   void set_bearer_cfg(uint32_t lc_id, srsenb::sched_interface::ue_bearer_cfg_t* cfg);
@@ -231,7 +243,7 @@ public:
   bool     needs_cqi(uint32_t tti, uint32_t cc_idx, bool will_send = false);
   uint32_t get_max_retx();
 
-  bool pucch_sr_collision(uint32_t current_tti, uint32_t n_cce);
+  bool pucch_sr_collision(uint32_t tti, uint32_t n_cce);
 
 private:
   bool is_sr_triggered();
@@ -298,7 +310,7 @@ private:
 
   bool phy_config_dedicated_enabled = false;
 
-  srslte::tti_point        last_tti;
+  srslte::tti_point        current_tti;
   std::vector<cc_sched_ue> carriers; ///< map of UE CellIndex to carrier configuration
 
   // Control Element Command queue

srsenb/src/stack/mac/scheduler.cc

@@ -432,6 +432,12 @@ void sched::new_tti(tti_point tti_rx)
   // Generate sched results for all CCs, if not yet generated
   for (size_t cc_idx = 0; cc_idx < carrier_schedulers.size(); ++cc_idx) {
     if (not is_generated(tti_rx, cc_idx)) {
+      // Setup tti-specific vars of the UE
+      for (auto& user : ue_db) {
+        user.second.new_tti(tti_rx);
+      }
+
+      // Generate carrier scheduling result
       carrier_schedulers[cc_idx]->generate_tti_result(tti_rx);
     }
   }

srsenb/src/stack/mac/scheduler_ue.cc

@@ -136,10 +136,10 @@ void sched_ue::set_cfg(const sched_interface::ue_cfg_t& cfg_)
 
     if (ue_idx >= prev_supported_cc_list.size()) {
       // New carrier needs to be added
-      carriers.emplace_back(cfg, (*cell_params_list)[cc_cfg.enb_cc_idx], rnti, ue_idx, last_tti);
+      carriers.emplace_back(cfg, (*cell_params_list)[cc_cfg.enb_cc_idx], rnti, ue_idx, current_tti);
     } else if (cc_cfg.enb_cc_idx != prev_supported_cc_list[ue_idx].enb_cc_idx) {
       // One carrier was added in the place of another
-      carriers[ue_idx] = cc_sched_ue{cfg, (*cell_params_list)[cc_cfg.enb_cc_idx], rnti, ue_idx, last_tti};
+      carriers[ue_idx] = cc_sched_ue{cfg, (*cell_params_list)[cc_cfg.enb_cc_idx], rnti, ue_idx, current_tti};
       if (ue_idx == 0) {
         log_h->info("SCHED: rnti=0x%x PCell is now enb_cc_idx=%d.\n", rnti, cc_cfg.enb_cc_idx);
       }
@@ -172,6 +172,13 @@ void sched_ue::reset()
   }
 }
 
+void sched_ue::new_tti(srslte::tti_point new_tti)
+{
+  current_tti = new_tti;
+
+  lch_handler.new_tti();
+}
+
 /*******************************************************
  *
  * FAPI-like main scheduler interface.
@@ -241,12 +248,12 @@ void sched_ue::unset_sr()
   sr = false;
 }
 
-bool sched_ue::pucch_sr_collision(uint32_t current_tti, uint32_t n_cce)
+bool sched_ue::pucch_sr_collision(uint32_t tti, uint32_t n_cce)
 {
   if (!phy_config_dedicated_enabled) {
     return false;
   }
-  if (cfg.pucch_cfg.sr_configured && srslte_ue_ul_sr_send_tti(&cfg.pucch_cfg, current_tti)) {
+  if (cfg.pucch_cfg.sr_configured && srslte_ue_ul_sr_send_tti(&cfg.pucch_cfg, tti)) {
     return (n_cce + cfg.pucch_cfg.N_pucch_1) == cfg.pucch_cfg.n_pucch_sr;
   }
   return false;
@@ -1110,12 +1117,11 @@ uint32_t sched_ue::get_aggr_level(uint32_t ue_cc_idx, uint32_t nof_bits)
 
 void sched_ue::finish_tti(const tti_params_t& tti_params, uint32_t enb_cc_idx)
 {
-  last_tti       = tti_point{tti_params.tti_rx};
   cc_sched_ue* c = find_ue_carrier(enb_cc_idx);
 
   if (c != nullptr) {
     // Check that scell state needs to change
-    c->finish_tti(last_tti);
+    c->finish_tti(current_tti);
   }
 }
 
@@ -1481,6 +1487,18 @@ void lch_manager::set_cfg(const sched_interface::ue_cfg_t& cfg)
   }
 }
 
+void lch_manager::new_tti()
+{
+  prio_idx++;
+  for (uint32_t lcid = 0; lcid < sched_interface::MAX_LC; ++lcid) {
+    if (is_bearer_active(lcid)) {
+      if (lch[lcid].cfg.pbr != pbr_infinity) {
+        lch[lcid].Bj = std::min(lch[lcid].Bj + (int)(lch[lcid].cfg.pbr * tti_duration_ms), lch[lcid].bucket_size);
+      }
+    }
+  }
+}
+
 void lch_manager::config_lcid(uint32_t lc_id, const sched_interface::ue_bearer_cfg_t& bearer_cfg)
 {
   if (lc_id >= sched_interface::MAX_LC) {
@@ -1497,6 +1515,13 @@ void lch_manager::config_lcid(uint32_t lc_id, const sched_interface::ue_bearer_c
 
   if (not is_equal) {
     lch[lc_id].cfg = bearer_cfg;
+    if (lch[lc_id].cfg.pbr == pbr_infinity) {
+      lch[lc_id].bucket_size = std::numeric_limits<int>::max();
+      lch[lc_id].Bj          = std::numeric_limits<int>::max();
+    } else {
+      lch[lc_id].bucket_size = lch[lc_id].cfg.bsd * lch[lc_id].cfg.pbr;
+      lch[lc_id].Bj          = 0;
+    }
     Info("SCHED: bearer configured: lc_id=%d, mode=%s, prio=%d\n",
          lc_id,
          to_string(lch[lc_id].cfg.direction),
@@ -1535,21 +1560,65 @@ void lch_manager::dl_buffer_state(uint8_t lcid, uint32_t tx_queue, uint32_t retx
   Debug("SCHED: DL lcid=%d buffer_state=%d,%d\n", lcid, tx_queue, retx_queue);
 }
 
-/* Allocates first available RLC PDU */
+int lch_manager::get_max_prio_lcid() const
+{
+  int min_prio_val = std::numeric_limits<int>::max(), prio_lcid = -1;
+  for (uint32_t lcid = 0; lcid < MAX_LC; ++lcid) {
+    if (get_dl_tx_total(lcid) > 0 and lch[lcid].Bj > 0 and lch[lcid].cfg.priority < min_prio_val) {
+      min_prio_val = lch[lcid].cfg.priority;
+      prio_lcid    = lcid;
+    }
+  }
+
+  if (prio_lcid < 0) {
+    // disregard Bj value in selection of lcid
+    size_t                       nof_lcids    = 0;
+    std::array<uint32_t, MAX_LC> chosen_lcids = {};
+    for (uint32_t lcid = 0; lcid < MAX_LC; ++lcid) {
+      if (get_dl_tx_total(lcid) > 0) {
+        if (lch[lcid].cfg.priority < min_prio_val) {
+          min_prio_val    = lch[lcid].cfg.priority;
+          chosen_lcids[0] = lcid;
+          nof_lcids       = 1;
+        } else if (lch[lcid].cfg.priority == min_prio_val) {
+          chosen_lcids[nof_lcids++] = lcid;
+        }
+      }
+    }
+    // logical chanels with equal priority should be served equally
+    if (nof_lcids > 0) {
+      prio_lcid = chosen_lcids[prio_idx % nof_lcids];
+    }
+  }
+
+  return prio_lcid;
+}
+
+/// Allocates first available RLC PDU
 int lch_manager::alloc_rlc_pdu(sched_interface::dl_sched_pdu_t* rlc_pdu, int rem_bytes)
 {
-  // TODO: Implement lcid priority (now lowest index is lowest priority)
   int alloc_bytes = 0;
-  int i           = 0;
+  int lcid        = get_max_prio_lcid();
-  for (i = 0; i < sched_interface::MAX_LC and alloc_bytes == 0; i++) {
+  if (lcid < 0) {
-    alloc_bytes = alloc_retx_bytes(i, rem_bytes);
+    return alloc_bytes;
-    if (alloc_bytes == 0) {
+  }
-      alloc_bytes = alloc_tx_bytes(i, rem_bytes);
+
-    }
+  // try first to allocate retxs
+  alloc_bytes = alloc_retx_bytes(lcid, rem_bytes);
+
+  // if no retx alloc, try newtx
+  if (alloc_bytes == 0) {
+    alloc_bytes = alloc_tx_bytes(lcid, rem_bytes);
   }
+
   if (alloc_bytes > 0) {
+    // Update Bj
+    if (lch[lcid].cfg.pbr != pbr_infinity) {
+      lch[lcid].Bj -= alloc_bytes;
+    }
+
     rlc_pdu->nbytes = alloc_bytes;
-    rlc_pdu->lcid   = i - 1;
+    rlc_pdu->lcid   = lcid;
     Debug("SCHED: Allocated lcid=%d, nbytes=%d, tbs_bytes=%d\n", rlc_pdu->lcid, rlc_pdu->nbytes, rem_bytes);
   }
   return alloc_bytes;

srsenb/src/stack/rrc/mac_controller.cc

@@ -27,6 +27,35 @@ namespace srsenb {
 
 using namespace asn1::rrc;
 
+// TS 36.331 9.1.1.2 - CCCH configuration
+sched_interface::ue_bearer_cfg_t get_bearer_default_ccch_config()
+{
+  sched_interface::ue_bearer_cfg_t bearer = {};
+  bearer.priority                         = 1;
+  bearer.pbr                              = -1;
+  bearer.bsd                              = -1;
+  bearer.group                            = 0;
+  return bearer;
+}
+
+// TS 36.331 9.2.1.1 - SRB1
+sched_interface::ue_bearer_cfg_t get_bearer_default_srb1_config()
+{
+  return get_bearer_default_ccch_config();
+}
+
+// TS 36.331 9.2.1.2 - SRB2
+sched_interface::ue_bearer_cfg_t get_bearer_default_srb2_config()
+{
+  sched_interface::ue_bearer_cfg_t bearer = get_bearer_default_srb1_config();
+  bearer.priority                         = 3;
+  return bearer;
+}
+
+/***************************
+ *  MAC Controller class
+ **************************/
+
 rrc::ue::mac_controller::mac_controller(rrc::ue* rrc_ue_, const sched_interface::ue_cfg_t& sched_ue_cfg) :
   log_h("RRC"),
   rrc_ue(rrc_ue_),
@@ -202,24 +231,55 @@ void rrc::ue::mac_controller::handle_con_reconf_with_mobility()
 
 void rrc::ue::mac_controller::apply_current_bearers_cfg()
 {
-  srsenb::sched_interface::ue_bearer_cfg_t bearer_cfg = {};
+  current_sched_ue_cfg.ue_bearers              = {};
-  current_sched_ue_cfg.ue_bearers                     = {};
+  current_sched_ue_cfg.ue_bearers[0].direction = sched_interface::ue_bearer_cfg_t::BOTH;
-  current_sched_ue_cfg.ue_bearers[0].direction        = sched_interface::ue_bearer_cfg_t::BOTH;
 
   // Configure SRBs
   const srb_to_add_mod_list_l& srbs = rrc_ue->bearer_list.get_established_srbs();
   for (const srb_to_add_mod_s& srb : srbs) {
-    bearer_cfg.direction                        = srsenb::sched_interface::ue_bearer_cfg_t::BOTH;
+    auto& bcfg = current_sched_ue_cfg.ue_bearers[srb.srb_id];
-    bearer_cfg.group                            = 0;
+    switch (srb.srb_id) {
-    current_sched_ue_cfg.ue_bearers[srb.srb_id] = bearer_cfg;
+      case 0:
+        bcfg = get_bearer_default_ccch_config();
+        break;
+      case 1:
+        bcfg = get_bearer_default_srb1_config();
+        break;
+      case 2:
+        bcfg = get_bearer_default_srb2_config();
+        break;
+      default:
+        bcfg = {};
+    }
+    bcfg.direction = srsenb::sched_interface::ue_bearer_cfg_t::BOTH;
+    if (srb.lc_ch_cfg_present and
+        srb.lc_ch_cfg.type().value == srb_to_add_mod_s::lc_ch_cfg_c_::types_opts::explicit_value and
+        srb.lc_ch_cfg.explicit_value().ul_specific_params_present) {
+      // NOTE: Use UL values for DL prioritization as well
+      auto& ul_params = srb.lc_ch_cfg.explicit_value().ul_specific_params;
+      bcfg.pbr        = ul_params.prioritised_bit_rate.to_number();
+      bcfg.priority   = ul_params.prio;
+      bcfg.bsd        = ul_params.bucket_size_dur.to_number();
+      if (ul_params.lc_ch_group_present) {
+        bcfg.group = ul_params.lc_ch_group;
+      }
+    }
   }
 
   // Configure DRBs
   const drb_to_add_mod_list_l& drbs = rrc_ue->bearer_list.get_established_drbs();
   for (const drb_to_add_mod_s& drb : drbs) {
-    bearer_cfg.direction                          = sched_interface::ue_bearer_cfg_t::BOTH;
+    auto& bcfg     = current_sched_ue_cfg.ue_bearers[drb.lc_ch_id];
-    bearer_cfg.group                              = drb.lc_ch_cfg.ul_specific_params.lc_ch_group;
+    bcfg           = {};
-    current_sched_ue_cfg.ue_bearers[drb.lc_ch_id] = bearer_cfg;
+    bcfg.direction = sched_interface::ue_bearer_cfg_t::BOTH;
+    bcfg.group     = 1;
+    bcfg.priority  = 4;
+    if (drb.lc_ch_cfg_present and drb.lc_ch_cfg.ul_specific_params_present) {
+      bcfg.group    = drb.lc_ch_cfg.ul_specific_params.lc_ch_group;
+      bcfg.pbr      = drb.lc_ch_cfg.ul_specific_params.prioritised_bit_rate.to_number();
+      bcfg.priority = drb.lc_ch_cfg.ul_specific_params.prio;
+      bcfg.bsd      = drb.lc_ch_cfg.ul_specific_params.bucket_size_dur;
+    }
   }
 }