diff --git a/lib/include/srslte/interfaces/enb_interfaces.h b/lib/include/srslte/interfaces/enb_interfaces.h
index bb75a8025..c1e14bef8 100644
--- a/lib/include/srslte/interfaces/enb_interfaces.h
+++ b/lib/include/srslte/interfaces/enb_interfaces.h
@@ -199,9 +199,8 @@ public:
    *
    * @param rnti identifier of the user
    * @param pcell_index Primary cell (PCell) index
-   * @param is_temporal Indicates whether the UE is temporal
    */
-  virtual int add_rnti(uint16_t rnti, uint32_t pcell_index, bool is_temporal) = 0;
+  virtual int add_rnti(uint16_t rnti, uint32_t pcell_index) = 0;
 
   /**
    * Removes an RNTI context from all the physical layer components, including secondary cells
@@ -209,6 +208,14 @@ public:
    */
   virtual void rem_rnti(uint16_t rnti) = 0;
 
+  /**
+   * Pregenerates the scrambling sequences for a given RNTI.
+   * WARNING: This function make take several ms to complete.
+   *
+   * @param rnti identifier of the user
+   */
+  virtual int pregen_sequences(uint16_t rnti) = 0;
+
   /**
    *
    * @param stop
diff --git a/srsenb/hdr/phy/cc_worker.h b/srsenb/hdr/phy/cc_worker.h
index bb63dd5a6..cd64810ca 100644
--- a/srsenb/hdr/phy/cc_worker.h
+++ b/srsenb/hdr/phy/cc_worker.h
@@ -42,8 +42,9 @@ public:
   cf_t* get_buffer_tx(uint32_t antenna_idx);
   void  set_tti(uint32_t tti);
 
-  int      add_rnti(uint16_t rnti, bool is_temporal);
+  int      add_rnti(uint16_t rnti);
   void     rem_rnti(uint16_t rnti);
+  int      pregen_sequences(uint16_t rnti);
   uint32_t get_nof_rnti();
 
   /* These are used by the GUI plotting tools */
diff --git a/srsenb/hdr/phy/phy.h b/srsenb/hdr/phy/phy.h
index da73c68cb..7e1100786 100644
--- a/srsenb/hdr/phy/phy.h
+++ b/srsenb/hdr/phy/phy.h
@@ -51,8 +51,9 @@ public:
   std::string get_type() override { return "lte"; };
 
   /* MAC->PHY interface */
-  int  add_rnti(uint16_t rnti, uint32_t pcell_index, bool is_temporal) override;
+  int  add_rnti(uint16_t rnti, uint32_t pcell_index) override;
   void rem_rnti(uint16_t rnti) final;
+  int  pregen_sequences(uint16_t rnti) override;
   void set_mch_period_stop(uint32_t stop) final;
   void set_activation_deactivation_scell(uint16_t                                     rnti,
                                          const std::array<bool, SRSLTE_MAX_CARRIERS>& activation) override;
diff --git a/srsenb/hdr/phy/sf_worker.h b/srsenb/hdr/phy/sf_worker.h
index 8ca54130e..c41de4e8e 100644
--- a/srsenb/hdr/phy/sf_worker.h
+++ b/srsenb/hdr/phy/sf_worker.h
@@ -41,8 +41,9 @@ public:
   cf_t* get_buffer_rx(uint32_t cc_idx, uint32_t antenna_idx);
   void  set_time(uint32_t tti, uint32_t tx_worker_cnt, srslte_timestamp_t tx_time);
 
-  int      add_rnti(uint16_t rnti, uint32_t cc_idx, bool is_temporal);
+  int      add_rnti(uint16_t rnti, uint32_t cc_idx);
   void     rem_rnti(uint16_t rnti);
+  int      pregen_sequences(uint16_t rnti);
   uint32_t get_nof_rnti();
 
   /* These are used by the GUI plotting tools */
diff --git a/srsenb/src/phy/cc_worker.cc b/srsenb/src/phy/cc_worker.cc
index 599935e9c..130deb787 100644
--- a/srsenb/src/phy/cc_worker.cc
+++ b/srsenb/src/phy/cc_worker.cc
@@ -127,14 +127,14 @@ void cc_worker::init(phy_common* phy_, srslte::log* log_h_, uint32_t cc_idx_)
   }
 
   /* Setup SI-RNTI in PHY */
-  add_rnti(SRSLTE_SIRNTI, false);
+  add_rnti(SRSLTE_SIRNTI);
 
   /* Setup P-RNTI in PHY */
-  add_rnti(SRSLTE_PRNTI, false);
+  add_rnti(SRSLTE_PRNTI);
 
   /* Setup RA-RNTI in PHY */
   for (int i = SRSLTE_RARNTI_START; i <= SRSLTE_RARNTI_END; i++) {
-    add_rnti(i, false);
+    add_rnti(i);
   }
 
   if (srslte_softbuffer_tx_init(&temp_mbsfn_softbuffer, nof_prb)) {
@@ -180,25 +180,25 @@ void cc_worker::set_tti(uint32_t tti_)
   tti_tx_ul = TTI_RX_ACK(tti_rx);
 }
 
-int cc_worker::add_rnti(uint16_t rnti, bool is_temporal)
+int cc_worker::pregen_sequences(uint16_t rnti)
 {
-
-  if (not is_temporal) {
-    if (srslte_enb_dl_add_rnti(&enb_dl, rnti)) {
-      return -1;
-    }
-    if (srslte_enb_ul_add_rnti(&enb_ul, rnti)) {
-      return -1;
-    }
+  if (srslte_enb_dl_add_rnti(&enb_dl, rnti)) {
+    return -1;
   }
+  if (srslte_enb_ul_add_rnti(&enb_ul, rnti)) {
+    return -1;
+  }
+  return SRSLTE_SUCCESS;
+}
+
+int cc_worker::add_rnti(uint16_t rnti)
+{
+  std::unique_lock<std::mutex> lock(mutex);
 
-  mutex.lock();
   // Create user unless already exists
   if (ue_db.count(rnti) == 0) {
     ue_db[rnti] = new ue(rnti);
   }
-  mutex.unlock();
-
   return SRSLTE_SUCCESS;
 }
 
diff --git a/srsenb/src/phy/phy.cc b/srsenb/src/phy/phy.cc
index 30165dc8a..6a061dcc9 100644
--- a/srsenb/src/phy/phy.cc
+++ b/srsenb/src/phy/phy.cc
@@ -150,7 +150,7 @@ void phy::stop()
 }
 
 /***** MAC->PHY interface **********/
-int phy::add_rnti(uint16_t rnti, uint32_t pcell_index, bool is_temporal)
+int phy::add_rnti(uint16_t rnti, uint32_t pcell_index)
 {
   if (SRSLTE_RNTI_ISUSER(rnti)) {
     // Create default PHY configuration with the desired PCell index
@@ -161,7 +161,7 @@ int phy::add_rnti(uint16_t rnti, uint32_t pcell_index, bool is_temporal)
   }
 
   for (uint32_t i = 0; i < nof_workers; i++) {
-    if (workers[i].add_rnti(rnti, pcell_index, is_temporal) != SRSLTE_SUCCESS) {
+    if (workers[i].add_rnti(rnti, pcell_index) != SRSLTE_SUCCESS) {
       return SRSLTE_ERROR;
     }
   }
@@ -183,6 +183,16 @@ void phy::rem_rnti(uint16_t rnti)
   }
 }
 
+int phy::pregen_sequences(uint16_t rnti)
+{
+  for (uint32_t i = 0; i < nof_workers; i++) {
+    if (workers[i].pregen_sequences(rnti) != SRSLTE_SUCCESS) {
+      return SRSLTE_ERROR;
+    }
+  }
+  return SRSLTE_SUCCESS;
+}
+
 void phy::set_mch_period_stop(uint32_t stop)
 {
   workers_common.set_mch_period_stop(stop);
@@ -241,7 +251,7 @@ void phy::set_config_dedicated(uint16_t rnti, const phy_rrc_dedicated_list_t& de
     if (config.configured) {
       // Add RNTI to all SF workers
       for (uint32_t w = 0; w < nof_workers; w++) {
-        workers[w].add_rnti(rnti, config.enb_cc_idx, false);
+        workers[w].add_rnti(rnti, config.enb_cc_idx);
       }
     }
   }
diff --git a/srsenb/src/phy/sf_worker.cc b/srsenb/src/phy/sf_worker.cc
index 98ba0769c..b1be21ef0 100644
--- a/srsenb/src/phy/sf_worker.cc
+++ b/srsenb/src/phy/sf_worker.cc
@@ -129,12 +129,22 @@ void sf_worker::set_time(uint32_t tti_, uint32_t tx_worker_cnt_, srslte_timestam
   }
 }
 
-int sf_worker::add_rnti(uint16_t rnti, uint32_t cc_idx, bool is_temporal)
+int sf_worker::pregen_sequences(uint16_t rnti)
+{
+  for (auto& w : cc_workers) {
+    if (w->pregen_sequences(rnti)) {
+      return SRSLTE_ERROR;
+    }
+  }
+  return SRSLTE_SUCCESS;
+}
+
+int sf_worker::add_rnti(uint16_t rnti, uint32_t cc_idx)
 {
   int ret = SRSLTE_ERROR;
 
   if (cc_idx < cc_workers.size()) {
-    cc_workers[cc_idx]->add_rnti(rnti, is_temporal);
+    cc_workers[cc_idx]->add_rnti(rnti);
     ret = SRSLTE_SUCCESS;
   }
 
diff --git a/srsenb/src/stack/mac/mac.cc b/srsenb/src/stack/mac/mac.cc
index 4ef080f3f..73206626f 100644
--- a/srsenb/src/stack/mac/mac.cc
+++ b/srsenb/src/stack/mac/mac.cc
@@ -212,8 +212,8 @@ int mac::ue_cfg(uint16_t rnti, sched_interface::ue_cfg_t* cfg)
   if (not ue_ptr->is_phy_added) {
     Info("Registering RNTI=0x%X to PHY...\n", rnti);
     // Register new user in PHY with first CC index
-    if (phy_h->add_rnti(rnti, (SRSLTE_MRNTI) ? 0 : cfg->supported_cc_list.front().enb_cc_idx, false) == SRSLTE_ERROR) {
-      Error("Registering new UE RNTI=0x%X to PHY\n", rnti);
+    if (phy_h->pregen_sequences(rnti) == SRSLTE_ERROR) {
+      Error("Generating sequences for UE RNTI=0x%X\n", rnti);
     }
     Info("Done registering RNTI=0x%X to PHY...\n", rnti);
     ue_ptr->is_phy_added = true;
@@ -524,7 +524,7 @@ void mac::rach_detected(uint32_t tti, uint32_t enb_cc_idx, uint32_t preamble_idx
     rrc_h->add_user(rnti, ue_cfg);
 
     // Add temporal rnti to the PHY
-    if (phy_h->add_rnti(rnti, enb_cc_idx, true) != SRSLTE_SUCCESS) {
+    if (phy_h->add_rnti(rnti, enb_cc_idx) != SRSLTE_SUCCESS) {
       Error("Registering temporal-rnti=0x%x to PHY\n", rnti);
       return;
     }