Improved DL TCP performance by tweeking BSR reports and UL scheduler

lib/include/srslte/interfaces/sched_interface.h

@@ -95,6 +95,7 @@ public:
     int priority; 
     int bsd; 
     int pbr;
+    int group;
     enum {IDLE = 0, UL, DL, BOTH} direction; 
   } ue_bearer_cfg_t; 
   
@@ -231,7 +232,7 @@ public:
   /* UL information */
   virtual int ul_crc_info(uint32_t tti, uint16_t rnti, bool crc) = 0; 
   virtual int ul_sr_info(uint32_t tti, uint16_t rnti) = 0; 
-  virtual int ul_bsr(uint16_t rnti, uint32_t lcid, uint32_t bsr) = 0; 
+  virtual int ul_bsr(uint16_t rnti, uint32_t lcid, uint32_t bsr, bool set_value = true) = 0;
   virtual int ul_recv_len(uint16_t rnti, uint32_t lcid, uint32_t len) = 0; 
   virtual int ul_phr(uint16_t rnti, int phr) = 0; 
   virtual int ul_cqi_info(uint32_t tti, uint16_t rnti, uint32_t cqi, uint32_t ul_ch_code) = 0; 

lib/src/common/pdu.cc

@@ -33,7 +33,7 @@
 
 // Table 6.1.3.1-1 Buffer size levels for BSR 
 static uint32_t btable[64] = {
-  0, 5, 10, 12, 14, 17, 19, 22, 26, 31, 36, 42, 49, 57, 67, 78, 91, 107, 125, 146, 171, 200, 234, 274, 321, 376, 440, 515, 603, 706, 826, 967, 1132, 
+  0, 1, 10, 12, 14, 17, 19, 22, 26, 31, 36, 42, 49, 57, 67, 78, 91, 107, 125, 146, 171, 200, 234, 274, 321, 376, 440, 515, 603, 706, 826, 967, 1132,
   1326, 1552, 1817, 2127, 2490, 2915, 3413, 3995, 4667, 5476, 6411, 7505, 8787, 10287, 12043, 14099, 16507, 19325, 22624, 26487, 31009, 36304, 
   42502, 49759, 58255, 68201, 79846, 93479, 109439, 128125, 150000};
 
@@ -428,12 +428,16 @@ int sch_subh::get_bsr(uint32_t buff_size[4])
       buff_size[2] = (payload[1]&0x0F) << 4 | (payload[1]&0xC0) >> 6;
       buff_size[3] = (payload[2]&0x3F); 
     } else {
-      uint32_t nonzero_lcg     = (payload[0]&0xc0) >> 6;
+      nonzero_lcg              = (payload[0]&0xc0) >> 6;
       buff_size[nonzero_lcg%4] =  payload[0]&0x3f;
     }
     for (int i=0;i<4;i++) {
       if (buff_size[i]) {
-        buff_size[i] = btable[buff_size[i]%64];
+        if (buff_size[i]<63) {
+          buff_size[i] = btable[1+buff_size[i]];
+        } else {
+          buff_size[i] = btable[63];
+        }
       }
     }
     return nonzero_lcg;

srsenb/drb.conf.example

@@ -15,14 +15,14 @@ qci_config = (
     };
     dl_um = {
       sn_field_length = 10; 
-      t_reordering    = 80;             
+      t_reordering    = 45;             
     };
   };
   logical_channel_config = {
-    priority = 11; 
+    priority = 13; 
     prioritized_bit_rate   = -1; 
     bucket_size_duration  = 100; 
-    log_chan_group = 3; 
+    log_chan_group = 2; 
   };
 },
 {

srsenb/hdr/mac/scheduler.h

@@ -108,7 +108,7 @@ public:
   
   int ul_crc_info(uint32_t tti, uint16_t rnti, bool crc);
   int ul_sr_info(uint32_t tti, uint16_t rnti); 
-  int ul_bsr(uint16_t rnti, uint32_t lcid, uint32_t bsr); 
+  int ul_bsr(uint16_t rnti, uint32_t lcid, uint32_t bsr, bool set_value = true);
   int ul_recv_len(uint16_t rnti, uint32_t lcid, uint32_t len);
   int ul_phr(uint16_t rnti, int phr); 
   int ul_cqi_info(uint32_t tti, uint16_t rnti, uint32_t cqi, uint32_t ul_ch_code); 

srsenb/hdr/mac/scheduler_harq.h

@@ -105,6 +105,7 @@ public:
   void       same_alloc();
   bool       is_adaptive_retx(); 
 
+  void       reset_pending_data();
   bool       has_pending_ack();
   uint32_t   get_pending_data(); 
   

srsenb/hdr/mac/scheduler_ue.h

@@ -62,7 +62,7 @@ public:
   void rem_bearer(uint32_t lc_id);
   
   void dl_buffer_state(uint8_t lc_id, uint32_t tx_queue, uint32_t retx_queue);
-  void ul_buffer_state(uint8_t lc_id, uint32_t bsr); 
+  void ul_buffer_state(uint8_t lc_id, uint32_t bsr, bool set_value = true);
   void ul_phr(int phr); 
   void mac_buffer_state(uint32_t ce_code);
   void ul_recv_len(uint32_t lcid, uint32_t len);
@@ -116,6 +116,8 @@ public:
   bool       get_pucch_sched(uint32_t current_tti, uint32_t prb_idx[2], uint32_t *L);
   bool       pucch_sr_collision(uint32_t current_tti, uint32_t n_cce);
 
+  uint32_t   get_pending_ul_old_data();
+
 private: 
   
   typedef struct {
@@ -126,7 +128,6 @@ private:
   } ue_bearer_t; 
   
   bool       is_sr_triggered();
-  uint32_t   get_pending_ul_old_data();  
   int        alloc_pdu(int tbs, sched_interface::dl_sched_pdu_t* pdu);
 
   static uint32_t format1_count_prb(uint32_t bitmask, uint32_t cell_nof_prb); 

srsenb/hdr/mac/ue.h

@@ -86,6 +86,8 @@ public:
   uint32_t rl_failure();
   void     rl_failure_reset();
 
+  void set_lcg(uint32_t lcid, uint32_t lcg);
+
   void metrics_read(srsenb::mac_metrics_t* metrics);
   void metrics_rx(bool crc, uint32_t tbs);
   void metrics_tx(bool crc, uint32_t tbs);
@@ -102,6 +104,8 @@ private:
   void metrics_phr(float phr); 
   uint32_t phr_counter;
 
+  std::vector<uint32_t> lc_groups[4];
+  
   mac_metrics_t metrics;
   
   srslte::mac_pcap* pcap;

srsenb/rr.conf.example

@@ -9,7 +9,7 @@ mac_cnfg =
   ulsch_cnfg = 
   {
     max_harq_tx = 4;
-    periodic_bsr_timer = 5; // in ms 
+    periodic_bsr_timer = 40; // in ms 
     retx_bsr_timer = 320;   // in ms
   };
   

srsenb/src/mac/mac.cc

@@ -33,6 +33,7 @@
 #include <strings.h>
 #include <pthread.h>
 #include <unistd.h>
+#include <srslte/interfaces/sched_interface.h>
 
 #include "srslte/common/log.h"
 #include "mac/mac.h"
@@ -164,6 +165,8 @@ int mac::rlc_buffer_state(uint16_t rnti, uint32_t lc_id, uint32_t tx_queue, uint
 int mac::bearer_ue_cfg(uint16_t rnti, uint32_t lc_id, sched_interface::ue_bearer_cfg_t* cfg)
 {
   if (ue_db.count(rnti)) {
+    // configure BSR group in UE
+    ue_db[rnti]->set_lcg(lc_id, (uint32_t) cfg->group);
     return scheduler.bearer_ue_cfg(rnti, lc_id, cfg);      
   } else {
     Error("User rnti=0x%x not found\n", rnti);

srsenb/src/mac/scheduler.cc

@@ -302,12 +302,12 @@ int sched::ul_cqi_info(uint32_t tti, uint16_t rnti, uint32_t cqi, uint32_t ul_ch
   return ret; 
 }
 
-int sched::ul_bsr(uint16_t rnti, uint32_t lcid, uint32_t bsr)
+int sched::ul_bsr(uint16_t rnti, uint32_t lcid, uint32_t bsr, bool set_value)
 {
   pthread_mutex_lock(&mutex);
   int ret = 0; 
   if (ue_db.count(rnti)) {         
-    ue_db[rnti].ul_buffer_state(lcid, bsr);
+    ue_db[rnti].ul_buffer_state(lcid, bsr, set_value);
   } else {
     Error("User rnti=0x%x not found\n", rnti);
     ret = -1;
@@ -792,13 +792,13 @@ int sched::ul_sched(uint32_t tti, srsenb::sched_interface::ul_sched_res_t* sched
             user->unset_sr();
           }
 
-          log_h->info("SCHED: %s %s rnti=0x%x, pid=%d, dci=%d,%d, grant=%d,%d, n_rtx=%d, tbs=%d, bsr=%d (%d)\n", 
+          log_h->info("SCHED: %s %s rnti=0x%x, pid=%d, dci=%d,%d, grant=%d,%d, n_rtx=%d, tbs=%d, bsr=%d (%d-%d)\n",
                       is_rar?"RAR":"UL",
                       is_newtx?"tx":"retx",                
                       rnti, h->get_id(), 
                       sched_result->pusch[nof_dci_elems].dci_location.L, sched_result->pusch[nof_dci_elems].dci_location.ncce,
                       alloc.RB_start, alloc.L, h->nof_retx(), sched_result->pusch[nof_dci_elems].tbs, 
-                      user->get_pending_ul_new_data(current_tti),pending_data_before);
+                      user->get_pending_ul_new_data(current_tti),pending_data_before, user->get_pending_ul_old_data());
 
           nof_dci_elems++;          
         } else {
@@ -814,6 +814,14 @@ int sched::ul_sched(uint32_t tti, srsenb::sched_interface::ul_sched_res_t* sched
     }
   }
 
+  // Update pending data counters after this TTI
+  for(std::map<uint16_t, sched_ue>::iterator iter=ue_db.begin(); iter!=ue_db.end(); ++iter) {
+    sched_ue *user = (sched_ue *) &iter->second;
+    uint16_t rnti = (uint16_t) iter->first;
+
+    user->get_ul_harq(current_tti)->reset_pending_data();
+  }
+
   sched_result->nof_dci_elems   = nof_dci_elems;
   sched_result->nof_phich_elems = nof_phich_elems;
 

srsenb/src/mac/scheduler_harq.cc

@@ -229,13 +229,22 @@ bool ul_harq_proc::has_pending_ack()
     active = false;     
   }
   if (!active) {
-    pending_data = 0; 
     need_ack = false;
   }
   return ret; 
 }
 
-uint32_t ul_harq_proc::get_pending_data()
+
+
+void ul_harq_proc::reset_pending_data()
+{
+  if (!active) {
+    pending_data = 0;
+  }
+}
+
+
+  uint32_t ul_harq_proc::get_pending_data()
 {
   return pending_data; 
 }

srsenb/src/mac/scheduler_ue.cc

@@ -163,12 +163,18 @@ void sched_ue::phy_config_enabled(uint32_t tti, bool enabled)
   phy_config_dedicated_enabled = enabled; 
 }
 
-void sched_ue::ul_buffer_state(uint8_t lc_id, uint32_t bsr)
+void sched_ue::ul_buffer_state(uint8_t lc_id, uint32_t bsr, bool set_value)
 {
   if (lc_id < sched_interface::MAX_LC) {
+    if (set_value) {
       lch[lc_id].bsr = bsr;
+    } else {
+      lch[lc_id].bsr += bsr;
+    }
     Debug("SCHED: UL lcid=%d buffer_state=%d\n", lc_id, bsr);
   }
+  Info("SCHED: bsr=%d, lcid=%d, bsr={%d,%d,%d,%d}\n", bsr, lc_id,
+       lch[0].bsr, lch[1].bsr, lch[2].bsr, lch[3].bsr);
 }
 
 void sched_ue::ul_phr(int phr)
@@ -297,6 +303,8 @@ void sched_ue::ul_recv_len(uint32_t lcid, uint32_t len)
       }
     }
   }
+  Info("SCHED: recv_len=%d, lcid=%d, bsr={%d,%d,%d,%d}\n", len, lcid,
+       lch[0].bsr, lch[1].bsr, lch[2].bsr, lch[3].bsr);
 }
 
 void sched_ue::set_ul_crc(uint32_t tti, bool crc_res)
@@ -554,6 +562,10 @@ uint32_t sched_ue::get_pending_ul_new_data(uint32_t tti)
   } else {
     pending_data = 0; 
   }
+  if (pending_data) {
+    Info("SCHED: pending_data=%d, pending_ul_data=%d, bsr={%d,%d,%d,%d}\n", pending_data,pending_ul_data,
+         lch[0].bsr, lch[1].bsr, lch[2].bsr, lch[3].bsr);
+  }
   return pending_data; 
 }
 

srsenb/src/mac/ue.cc

@@ -58,6 +58,10 @@ void ue::config(uint16_t rnti_, uint32_t nof_prb, sched_interface *sched_, rrc_i
   for(int i=0;i<NOF_HARQ_PROCESSES;i++) {
     pending_buffers[i] = NULL; 
   }
+
+  // Set LCID group for SRB0 and SRB1
+  set_lcg(0, 0);
+  set_lcg(1, 0);
 }  
 
 
@@ -89,6 +93,15 @@ void ue::rl_failure_reset()
   nof_failures = 0;
 }
 
+void ue::set_lcg(uint32_t lcid, uint32_t lcg)
+{
+  // find and remove if already exists
+  for (int i=0;i<4;i++) {
+    lc_groups[lcg].erase(std::remove(lc_groups[lcg].begin(), lc_groups[lcg].end(), lcid), lc_groups[lcg].end());
+  }
+  lc_groups[lcg].push_back(lcid);
+}
+
 srslte_softbuffer_rx_t* ue::get_rx_softbuffer(uint32_t tti)
 {
   return &softbuffer_rx[tti%NOF_HARQ_PROCESSES];
@@ -139,10 +152,12 @@ void ue::process_pdu(uint8_t* pdu, uint32_t nof_bytes, uint32_t tstamp)
     pcap->write_ul_crnti(pdu, nof_bytes, rnti, true, last_tti);
   }
 
+  uint32_t lcid_most_data = 0;
+  int most_data = -99;
+  
   while(mac_msg_ul.next()) {
     assert(mac_msg_ul.get());
-    if (mac_msg_ul.get()->is_sdu()) 
+    if (mac_msg_ul.get()->is_sdu()) {
-    {
       // Route logical channel 
       log_h->debug_hex(mac_msg_ul.get()->get_sdu_ptr(), mac_msg_ul.get()->get_payload_size(),
                        "PDU:   rnti=0x%x, lcid=%d, %d bytes\n",
@@ -156,7 +171,7 @@ void ue::process_pdu(uint8_t* pdu, uint32_t nof_bytes, uint32_t tstamp)
       if (mac_msg_ul.get()->get_sdu_lcid() == 0) {
         uint8_t *x = mac_msg_ul.get()->get_sdu_ptr();
         uint32_t sum = 0;
-        for (uint32_t i=0;i<mac_msg_ul.get()->get_payload_size();i++) {
+        for (uint32_t i = 0; i < mac_msg_ul.get()->get_payload_size(); i++) {
           sum += x[i];
         }
         if (sum == 0) {
@@ -175,25 +190,43 @@ void ue::process_pdu(uint8_t* pdu, uint32_t nof_bytes, uint32_t tstamp)
       // Indicate scheduler to update BSR counters 
       sched->ul_recv_len(rnti, mac_msg_ul.get()->get_sdu_lcid(), mac_msg_ul.get()->get_payload_size());
 
+      if ((int) mac_msg_ul.get()->get_payload_size() > most_data) {
+        most_data = (int) mac_msg_ul.get()->get_payload_size();
+        lcid_most_data = mac_msg_ul.get()->get_sdu_lcid();
+      }
+
       // Save contention resolution if lcid == 0
       if (mac_msg_ul.get()->get_sdu_lcid() == 0 && route_pdu) {
         uint32_t nbytes = srslte::sch_subh::MAC_CE_CONTRES_LEN;
         if (mac_msg_ul.get()->get_payload_size() >= nbytes) {
-          uint8_t *ue_cri_ptr  = (uint8_t*) &conres_id;
+          uint8_t *ue_cri_ptr = (uint8_t *) &conres_id;
           uint8_t *pkt_ptr = mac_msg_ul.get()->get_sdu_ptr(); // Warning here: we want to include the
-          for (uint32_t i=0;i<nbytes;i++) {
+          for (uint32_t i = 0; i < nbytes; i++) {
-            ue_cri_ptr[nbytes-i-1] = pkt_ptr[i];
+            ue_cri_ptr[nbytes - i - 1] = pkt_ptr[i];
           }
         } else {
           Error("Received CCCH UL message of invalid size=%d bytes\n", mac_msg_ul.get()->get_payload_size());
         }
       }
-    } else {
+    }
+  }
+  mac_msg_ul.reset();
+
+  /* Process CE after all SDUs because we need to update BSR after */
+  bool bsr_received = false;
+  while(mac_msg_ul.next()) {
+    assert(mac_msg_ul.get());
+    if (!mac_msg_ul.get()->is_sdu()) {
       // Process MAC Control Element
-      if (!process_ce(mac_msg_ul.get())) {
+      bsr_received |= process_ce(mac_msg_ul.get());
-        Warning("Received Subheader with invalid or unkonwn LCID\n");
     }
   }
+
+  // If BSR is not received means that new data has arrived and there is no space for BSR transmission
+  if (!bsr_received && lcid_most_data > 2) {
+    // Add BSR to the LCID for which most data was received
+    sched->ul_bsr(rnti, lcid_most_data, 256, false); // false adds BSR instead of setting
+    Info("BSR not received. Giving extra grant\n");
   }
 
   Debug("MAC PDU processed\n");
@@ -222,9 +255,10 @@ void ue::push_pdu(uint32_t tti, uint32_t len)
 
 bool ue::process_ce(srslte::sch_subh *subh) {
   uint32_t buff_size[4] = {0, 0, 0, 0};
-  uint32_t idx = 0; 
   float phr = 0;
+  int idx = 0;
   uint16_t old_rnti = 0;
+  bool is_bsr = false;
   switch(subh->ce_type()) {
     case srslte::sch_subh::PHR_REPORT: 
       phr = subh->get_phr(); 
@@ -244,22 +278,25 @@ bool ue::process_ce(srslte::sch_subh *subh) {
       break;
     case srslte::sch_subh::TRUNC_BSR: 
     case srslte::sch_subh::SHORT_BSR:
-    case srslte::sch_subh::LONG_BSR: 
       idx = subh->get_bsr(buff_size);
-      if (idx > 0) {
+      for (uint32_t i=0;i<lc_groups[idx].size();i++) {
         // Indicate BSR to scheduler
-        sched->ul_bsr(rnti, idx, 2*buff_size[idx]);
+        sched->ul_bsr(rnti, lc_groups[idx][i], buff_size[idx]);
-        Info("CE:    Received BSR rnti=0x%x, lcid=%d, value=%d\n", rnti, idx, buff_size[idx]);        
+        Info("CE:    Received %s BSR rnti=0x%x, lcg=%d, lcid=%d, value=%d\n",
-      } else if (idx == 0) {
+             subh->ce_type()==srslte::sch_subh::SHORT_BSR?"Short":"Trunc", rnti, idx, lc_groups[idx][i], buff_size[idx]);
-        // TODO: map lcid group to lcid
-        for (int i=0;i<4;i++) {
-          sched->ul_bsr(rnti, i, 2*buff_size[i]);
       }
+      is_bsr = true;
+      break;
+    case srslte::sch_subh::LONG_BSR:
+      subh->get_bsr(buff_size);
+      for (int idx=0;idx<4;idx++) {
+        for (uint32_t i=0;i<lc_groups[idx].size();i++) {
+          sched->ul_bsr(rnti, lc_groups[idx][i], buff_size[idx]);
+        }
+      }
+      is_bsr = true;
       Info("CE:    Received Long BSR rnti=0x%x, value=%d,%d,%d,%d\n", rnti,
            buff_size[0], buff_size[1], buff_size[2], buff_size[3]);
-      } else {
-        printf("Error!\n");
-      }
       break;
     case srslte::sch_subh::PADDING: 
       Debug("CE:    Received padding for rnti=0x%x\n", rnti);
@@ -268,7 +305,7 @@ bool ue::process_ce(srslte::sch_subh *subh) {
       Error("CE:    Invalid lcid=0x%x\n", subh->ce_type());
       break;
   }
-  return true; 
+  return is_bsr;
 }
 
 

srsenb/src/upper/rrc.cc

@@ -24,6 +24,8 @@
  *
  */
 
+#include <srslte/interfaces/sched_interface.h>
+#include <srslte/asn1/liblte_rrc.h>
 #include "srslte/asn1/liblte_mme.h"
 #include "upper/rrc.h"
 
@@ -1311,7 +1313,9 @@ void rrc::ue::send_connection_reconf(srslte::byte_buffer_t *pdu)
   // Add SRB2 and DRB1 to the scheduler
   srsenb::sched_interface::ue_bearer_cfg_t bearer_cfg;
   bearer_cfg.direction = srsenb::sched_interface::ue_bearer_cfg_t::BOTH;
+  bearer_cfg.group = 0;
   parent->mac->bearer_ue_cfg(rnti, 2, &bearer_cfg);
+  bearer_cfg.group = conn_reconf->rr_cnfg_ded.drb_to_add_mod_list[0].lc_cnfg.ul_specific_params.log_chan_group;
   parent->mac->bearer_ue_cfg(rnti, 3, &bearer_cfg);
   
   // Configure SRB2 in RLC and PDCP

srsue/ue.conf.example

@@ -26,7 +26,7 @@ ul_freq = 2565000000
 tx_gain = 80
 rx_gain = 60
 
-#nof_rx_ant = 1
+nof_rx_ant = 2
 #device_name = auto
 #device_args = auto
 #time_adv_nsamples = auto