adding MAC 0 padding support

lib/include/srsran/interfaces/enb_command_interface.h

@@ -25,6 +25,8 @@ public:
    * @param gain Relative gain
    */
   virtual void cmd_cell_gain(uint32_t cell_id, float gain) = 0;
+
+  virtual void toggle_padding() = 0;
 };
 } // namespace srsenb
 

lib/include/srsran/interfaces/enb_mac_interfaces.h

@@ -21,6 +21,7 @@ namespace srsenb {
 struct mac_args_t {
   uint32_t                      nof_prb; ///< Needed to dimension MAC softbuffers for all cells
   sched_interface::sched_args_t sched;
+  int                           lcid_padding;
   int                           nr_tb_size = -1;
   uint32_t                      nof_prealloc_ues; ///< Number of UE resources to pre-allocate at eNB startup
   uint32_t                      max_nof_kos;

srsenb/enb.conf.example

@@ -332,6 +332,7 @@ enable = false
 #max_prach_offset_us  = 30
 #nof_prealloc_ues     = 8
 #rlf_release_timer_ms = 4000
+#lcid_padding         = 3
 #eea_pref_list = EEA0, EEA2, EEA1
 #eia_pref_list = EIA2, EIA1, EIA0
 #gtpu_tunnel_timeout = 0

srsenb/hdr/enb.h

@@ -137,6 +137,8 @@ public:
   // eNodeB command interface
   void cmd_cell_gain(uint32_t cell_id, float gain) override;
 
+  void toggle_padding() override;
+
 private:
   const static int ENB_POOL_SIZE = 1024 * 10;
 

srsenb/hdr/stack/enb_stack_base.h

@@ -92,6 +92,7 @@ public:
 
   virtual void stop() = 0;
 
+  virtual void toggle_padding() = 0;
   // eNB metrics interface
   virtual bool get_metrics(stack_metrics_t* metrics) = 0;
 };

srsenb/hdr/stack/enb_stack_lte.h

@@ -91,6 +91,7 @@ public:
   {
     mac.set_sched_dl_tti_mask(tti_mask, nof_sfs);
   }
+  void toggle_padding() override { mac.toggle_padding(); }
   void tti_clock() override;
 
 private:

srsenb/hdr/stack/gnb_stack_nr.h

@@ -71,6 +71,8 @@ public:
   // MAC interface to trigger processing of received PDUs
   void process_pdus() final;
 
+  void toggle_padding() { srsran::console("padding not available for NR\n"); }
+
 private:
   void run_thread() final;
   void run_tti_impl(uint32_t tti);

srsenb/hdr/stack/mac/mac.h

@@ -94,6 +94,11 @@ public:
   bool process_pdus();
 
   void get_metrics(mac_metrics_t& metrics);
+
+  void toggle_padding();
+
+  void add_padding();
+
   void write_mcch(const srsran::sib2_mbms_t* sib2_,
                   const srsran::sib13_t*     sib13_,
                   const srsran::mcch_msg_t*  mcch_,
@@ -176,8 +181,9 @@ private:
   uint8_t             mtch_payload_buffer[mtch_payload_len] = {};
 
   // pointer to MAC PCAP object
-  srsran::mac_pcap*     pcap     = nullptr;
-  srsran::mac_pcap_net* pcap_net = nullptr;
+  srsran::mac_pcap*     pcap       = nullptr;
+  srsran::mac_pcap_net* pcap_net   = nullptr;
+  bool                  do_padding = false;
 
   // Number of rach preambles detected for a cc.
   std::vector<uint32_t> detected_rachs;

srsenb/hdr/stack/mac/ue.h

@@ -144,6 +144,7 @@ public:
   void     start_ta() { ta_fsm.start(); };
   uint32_t set_ta_us(float ta_us) { return ta_fsm.push_value(ta_us); };
   void     tic();
+  void     trigger_padding(int lcid);
 
   uint8_t* generate_pdu(uint32_t                              ue_cc_idx,
                         uint32_t                              harq_pid,

srsenb/src/enb.cc

@@ -227,4 +227,9 @@ std::string enb::get_build_string()
   return ss.str();
 }
 
+void enb::toggle_padding()
+{
+  stack->toggle_padding();
+}
+
 } // namespace srsenb

srsenb/src/main.cc

@@ -216,6 +216,7 @@ void parse_args(all_args_t* args, int argc, char* argv[])
     ("expert.eea_pref_list", bpo::value<string>(&args->general.eea_pref_list)->default_value("EEA0, EEA2, EEA1"), "Ordered preference list for the selection of encryption algorithm (EEA) (default: EEA0, EEA2, EEA1).")
     ("expert.eia_pref_list", bpo::value<string>(&args->general.eia_pref_list)->default_value("EIA2, EIA1, EIA0"), "Ordered preference list for the selection of integrity algorithm (EIA) (default: EIA2, EIA1, EIA0).")
     ("expert.nof_prealloc_ues", bpo::value<uint32_t>(&args->stack.mac.nof_prealloc_ues)->default_value(8), "Number of UE resources to preallocate during eNB initialization")
+    ("expert.lcid_padding", bpo::value<int>(&args->stack.mac.lcid_padding)->default_value(3), "LCID on which to put MAC padding")
     ("expert.max_mac_dl_kos", bpo::value<uint32_t>(&args->general.max_mac_dl_kos)->default_value(100), "Maximum number of consecutive KOs in DL before triggering the UE's release")
     ("expert.max_mac_ul_kos", bpo::value<uint32_t>(&args->general.max_mac_ul_kos)->default_value(100), "Maximum number of consecutive KOs in UL before triggering the UE's release")
     ("expert.gtpu_tunnel_timeout", bpo::value<uint32_t>(&args->stack.gtpu_indirect_tunnel_timeout_msec)->default_value(0), "Maximum time that GTPU takes to release indirect forwarding tunnel since the last received GTPU PDU. (0 for infinity)")
@@ -428,6 +429,7 @@ void parse_args(all_args_t* args, int argc, char* argv[])
 }
 
 static bool do_metrics = false;
+static bool do_padding = false;
 
 static void* input_loop(metrics_stdout* metrics, srsenb::enb_command_interface* control)
 {
@@ -452,6 +454,14 @@ static void* input_loop(metrics_stdout* metrics, srsenb::enb_command_interface*
             cout << "Enter t to restart trace." << endl;
           }
           metrics->toggle_print(do_metrics);
+        } else if (cmd[0] == "p") {
+          do_padding = !do_padding;
+          if (do_padding) {
+            cout << "Enter p to stop padding." << endl;
+          } else {
+            cout << "Enter p to restart padding." << endl;
+          }
+          control->toggle_padding();
         } else if (cmd[0] == "q") {
           raise(SIGTERM);
         } else if (cmd[0] == "cell_gain") {
@@ -471,6 +481,7 @@ static void* input_loop(metrics_stdout* metrics, srsenb::enb_command_interface*
           cout << "          t: starts console trace" << endl;
           cout << "          q: quit srsenb" << endl;
           cout << "  cell_gain: set relative cell gain" << endl;
+          cout << "          p: starts MAC padding" << endl;
           cout << endl;
         }
       }

srsenb/src/stack/mac/mac.cc

@@ -285,6 +285,21 @@ void mac::get_metrics(mac_metrics_t& metrics)
   metrics.cc_rach_counter = detected_rachs;
 }
 
+void mac::toggle_padding()
+{
+  do_padding = !do_padding;
+}
+
+void mac::add_padding()
+{
+  for (auto it = ue_db.begin(); it != ue_db.end(); ++it) {
+    uint16_t cur_rnti = it->first;
+    auto     ue       = it;
+    scheduler.dl_rlc_buffer_state(ue->first, args.lcid_padding, 20e6, 0);
+    ue->second->trigger_padding(args.lcid_padding);
+  }
+}
+
 /********************************************************
  *
  * PHY interface
@@ -594,6 +609,9 @@ int mac::get_dl_sched(uint32_t tti_tx_dl, dl_sched_list_t& dl_sched_res_list)
 
   trace_complete_event("mac::get_dl_sched", "total_time");
   logger.set_context(TTI_SUB(tti_tx_dl, FDD_HARQ_DELAY_UL_MS));
+  if (do_padding) {
+    add_padding();
+  }
 
   for (uint32_t enb_cc_idx = 0; enb_cc_idx < cell_config.size(); enb_cc_idx++) {
     // Run scheduler with current info

srsenb/src/stack/mac/ue.cc

@@ -732,4 +732,9 @@ void ue::tic()
   }
 }
 
+void ue::trigger_padding(int lcid)
+{
+  sched->ul_bsr(rnti, lcid, 20e6);
+}
+
 } // namespace srsenb