diff --git a/srsenb/hdr/stack/mac/nr/sched_nr.h b/srsenb/hdr/stack/mac/nr/sched_nr.h
index c34e0605f..b1cf3502e 100644
--- a/srsenb/hdr/stack/mac/nr/sched_nr.h
+++ b/srsenb/hdr/stack/mac/nr/sched_nr.h
@@ -38,7 +38,7 @@ public:
   void new_tti(tti_point tti_rx) override;
   int  generate_sched_result(tti_point tti_rx, uint32_t cc, sched_nr_res_t& result);
 
-  void dl_ack_info(tti_point tti_rx, uint16_t rnti, uint32_t cc, uint32_t tb_idx, bool ack) override;
+  void dl_ack_info(uint16_t rnti, uint32_t cc, uint32_t pid, uint32_t tb_idx, bool ack) override;
   void ul_sr_info(tti_point tti_rx, uint16_t rnti) override;
 
 private:
@@ -50,7 +50,7 @@ private:
   using sched_worker_manager = sched_nr_impl::sched_worker_manager;
   sched_worker_manager sched_workers;
 
-  std::array<std::array<sched_nr_res_t, SCHED_NR_MAX_CARRIERS>, SCHED_NR_MAX_CARRIERS> sched_results;
+  std::array<std::array<sched_nr_res_t, SCHED_NR_MAX_CARRIERS>, SCHED_NR_NOF_SUBFRAMES> sched_results;
 
   using ue_map_t = sched_nr_impl::ue_map_t;
   std::mutex ue_db_mutex;
diff --git a/srsenb/hdr/stack/mac/nr/sched_nr_common.h b/srsenb/hdr/stack/mac/nr/sched_nr_common.h
index f120fa802..996003cc2 100644
--- a/srsenb/hdr/stack/mac/nr/sched_nr_common.h
+++ b/srsenb/hdr/stack/mac/nr/sched_nr_common.h
@@ -13,12 +13,21 @@
 #ifndef SRSRAN_SCHED_NR_COMMON_H
 #define SRSRAN_SCHED_NR_COMMON_H
 
-#include "srsran/adt/circular_map.h"
+#include "sched_nr_interface.h"
+#include "srsran/adt/bounded_bitset.h"
 
 namespace srsenb {
 
 const static size_t SCHED_NR_MAX_USERS     = 4;
 const static size_t SCHED_NR_NOF_SUBFRAMES = 10;
+const static size_t SCHED_NR_MAX_NOF_RBGS  = 25;
+const static size_t SCHED_NR_NOF_HARQS     = 16;
+
+namespace sched_nr_impl {
+
+using rbgmask_t = srsran::bounded_bitset<SCHED_NR_MAX_NOF_RBGS, true>;
+
+} // namespace sched_nr_impl
 
 } // namespace srsenb
 
diff --git a/srsenb/hdr/stack/mac/nr/sched_nr_harq.h b/srsenb/hdr/stack/mac/nr/sched_nr_harq.h
index 6b6fe2ed2..e090e109a 100644
--- a/srsenb/hdr/stack/mac/nr/sched_nr_harq.h
+++ b/srsenb/hdr/stack/mac/nr/sched_nr_harq.h
@@ -13,24 +13,29 @@
 #ifndef SRSRAN_SCHED_NR_HARQ_H
 #define SRSRAN_SCHED_NR_HARQ_H
 
+#include "sched_nr_common.h"
 #include "srsran/common/tti_point.h"
 #include <array>
 
 namespace srsenb {
 namespace sched_nr_impl {
 
-template <size_t NofTbs>
-class harq
+class harq_proc
 {
 public:
-  harq() = default;
+  explicit harq_proc(uint32_t id_, uint32_t max_nof_tb_ = 1) : pid(id_), max_nof_tb(max_nof_tb_) {}
 
-  bool empty() const
-  {
-    return std::all_of(tb.begin(), tb.end(), [](const tb_t t) { return not t.active; });
-  }
+  bool empty() const { return not tb[0].active and not tb[1].active; }
   bool empty(uint32_t tb_idx) const { return tb[tb_idx].active; }
 
+  void ack_info(uint32_t tb_idx, bool ack) { tb[tb_idx].ack_state = ack; }
+
+  bool has_pending_retx(tti_point tti_rx) const { return not empty() and tti_tx + ack_delay <= tti_rx; }
+
+  bool new_tx(tti_point tti_tx, const rbgmask_t& rbgmask, uint32_t mcs, uint32_t ack_delay);
+
+  const uint32_t pid;
+
 private:
   struct tb_t {
     bool     active    = false;
@@ -40,19 +45,58 @@ private:
     uint32_t mcs       = 0;
   };
 
-  uint32_t                 id;
-  tti_point                tti_tx;
-  std::array<tb_t, NofTbs> tb;
+  const uint32_t max_nof_tb;
+
+  tti_point                         tti_tx;
+  uint32_t                          ack_delay = 0;
+  rbgmask_t                         rbgmask;
+  std::array<tb_t, SCHED_NR_MAX_TB> tb;
 };
 
 class harq_entity
 {
 public:
-  void dl_ack_info(tti_point tti_rx, uint32_t tb_idx, bool ack) {}
+  harq_entity();
+  void new_tti(tti_point tti_rx_);
+
+  void dl_ack_info(uint32_t pid, uint32_t tb_idx, bool ack) { dl_harqs[pid].ack_info(tb_idx, ack); }
+
+  harq_proc& get_dl_harq(uint32_t pid) { return dl_harqs[pid]; }
+
+  harq_proc* find_pending_dl_retx()
+  {
+    return find_dl([this](const harq_proc& h) { return h.has_pending_retx(tti_rx); });
+  }
+  harq_proc* find_pending_ul_retx()
+  {
+    return find_ul([this](const harq_proc& h) { return h.has_pending_retx(tti_rx); });
+  }
+  harq_proc* find_empty_dl_harq()
+  {
+    return find_dl([](const harq_proc& h) { return h.empty(); });
+  }
+  harq_proc* find_empty_ul_harq()
+  {
+    return find_ul([](const harq_proc& h) { return h.empty(); });
+  }
 
 private:
-  std::array<harq<1>, 16> dl_harqs;
-  std::array<harq<1>, 16> ul_harqs;
+  template <typename Predicate>
+  harq_proc* find_dl(Predicate p)
+  {
+    auto it = std::find_if(dl_harqs.begin(), dl_harqs.end(), p);
+    return (it == dl_harqs.end()) ? nullptr : &(*it);
+  }
+  template <typename Predicate>
+  harq_proc* find_ul(Predicate p)
+  {
+    auto it = std::find_if(ul_harqs.begin(), ul_harqs.end(), p);
+    return (it == ul_harqs.end()) ? nullptr : &(*it);
+  }
+
+  tti_point              tti_rx;
+  std::vector<harq_proc> dl_harqs;
+  std::vector<harq_proc> ul_harqs;
 };
 
 } // namespace sched_nr_impl
diff --git a/srsenb/hdr/stack/mac/nr/sched_nr_interface.h b/srsenb/hdr/stack/mac/nr/sched_nr_interface.h
index fb1fe93fc..e38d4e8ad 100644
--- a/srsenb/hdr/stack/mac/nr/sched_nr_interface.h
+++ b/srsenb/hdr/stack/mac/nr/sched_nr_interface.h
@@ -18,10 +18,16 @@
 
 namespace srsenb {
 
-const static size_t   SCHED_NR_MAX_CARRIERS = 4;
-const static uint16_t SCHED_NR_INVALID_RNTI = 0;
+const static size_t   SCHED_NR_MAX_CARRIERS   = 4;
+const static uint16_t SCHED_NR_INVALID_RNTI   = 0;
+const static size_t   SCHED_NR_MAX_PDSCH_DATA = 16;
+const static size_t   SCHED_NR_MAX_PUSCH_DATA = 16;
+const static size_t   SCHED_NR_MAX_TB         = 2;
 
-struct sched_nr_cell_cfg {};
+struct sched_nr_cell_cfg {
+  uint32_t nof_prb;
+  uint32_t nof_rbg;
+};
 
 struct sched_nr_cfg {
   uint32_t nof_concurrent_subframes = 1;
@@ -37,9 +43,21 @@ struct sched_nr_ue_cfg {
   srsran::bounded_vector<sched_nr_ue_cc_cfg, SCHED_NR_MAX_CARRIERS> carriers;
 };
 
+struct sched_nr_data_t {
+  srsran::bounded_vector<uint32_t, SCHED_NR_MAX_TB> tbs;
+};
+
+struct sched_nr_dl_res_t {
+  srsran::bounded_vector<sched_nr_data_t, SCHED_NR_MAX_PDSCH_DATA> data;
+};
+
+struct sched_nr_ul_res_t {
+  srsran::bounded_vector<sched_nr_data_t, SCHED_NR_MAX_PUSCH_DATA> pusch;
+};
+
 struct sched_nr_res_t {
-  struct dl_result {};
-  struct ul_result {};
+  sched_nr_dl_res_t dl_res;
+  sched_nr_ul_res_t ul_res;
 };
 
 class sched_nr_interface
@@ -49,8 +67,8 @@ public:
   virtual void ue_cfg(uint16_t rnti, const sched_nr_ue_cfg& ue_cfg) = 0;
   virtual void new_tti(tti_point tti_rx)                            = 0;
 
-  virtual void dl_ack_info(tti_point tti_rx, uint16_t rnti, uint32_t cc, uint32_t tb_idx, bool ack) = 0;
-  virtual void ul_sr_info(tti_point, uint16_t rnti)                                                 = 0;
+  virtual void dl_ack_info(uint16_t rnti, uint32_t cc, uint32_t pid, uint32_t tb_idx, bool ack) = 0;
+  virtual void ul_sr_info(tti_point, uint16_t rnti)                                             = 0;
 };
 
 } // namespace srsenb
diff --git a/srsenb/hdr/stack/mac/nr/sched_nr_rb_grid.h b/srsenb/hdr/stack/mac/nr/sched_nr_rb_grid.h
new file mode 100644
index 000000000..38ae6a366
--- /dev/null
+++ b/srsenb/hdr/stack/mac/nr/sched_nr_rb_grid.h
@@ -0,0 +1,49 @@
+/**
+ *
+ * \section COPYRIGHT
+ *
+ * Copyright 2013-2021 Software Radio Systems Limited
+ *
+ * By using this file, you agree to the terms and conditions set
+ * forth in the LICENSE file which can be found at the top level of
+ * the distribution.
+ *
+ */
+
+#ifndef SRSRAN_SCHED_NR_RB_GRID_H
+#define SRSRAN_SCHED_NR_RB_GRID_H
+
+#include "sched_nr_interface.h"
+#include "sched_nr_ue.h"
+
+namespace srsenb {
+namespace sched_nr_impl {
+
+class slot_grid
+{
+public:
+  explicit slot_grid(uint32_t cc, const sched_nr_cfg& cfg_);
+  void new_tti(tti_point tti_rx_, sched_nr_res_t& sched_res_);
+  bool alloc_pdsch(slot_ue& ue, const rbgmask_t& dl_mask);
+  bool alloc_pusch(slot_ue& ue, const rbgmask_t& dl_mask);
+
+  void generate_dcis();
+
+  tti_point tti_tx_dl() const { return tti_rx + TX_ENB_DELAY; }
+  tti_point tti_tx_ul() const { return tti_tx_dl() + K2; }
+
+private:
+  static const size_t K0 = 0, K1 = 4, K2 = 4;
+  const uint32_t      cc;
+  const sched_nr_cfg& cfg;
+
+  tti_point       tti_rx;
+  rbgmask_t       pdsch_mask;
+  rbgmask_t       pusch_mask;
+  sched_nr_res_t* sched_res = nullptr;
+};
+
+} // namespace sched_nr_impl
+} // namespace srsenb
+
+#endif // SRSRAN_SCHED_NR_RB_GRID_H
diff --git a/srsenb/hdr/stack/mac/nr/sched_nr_ue.h b/srsenb/hdr/stack/mac/nr/sched_nr_ue.h
index 5eccca607..16688f11c 100644
--- a/srsenb/hdr/stack/mac/nr/sched_nr_ue.h
+++ b/srsenb/hdr/stack/mac/nr/sched_nr_ue.h
@@ -16,6 +16,7 @@
 #include "sched_nr_common.h"
 #include "sched_nr_harq.h"
 #include "sched_nr_interface.h"
+#include "srsran/adt/circular_map.h"
 #include "srsran/adt/move_callback.h"
 #include "srsran/adt/pool/cached_alloc.h"
 
@@ -25,51 +26,61 @@ namespace sched_nr_impl {
 
 class ue_carrier;
 
-class bwp_ue
+class slot_ue
 {
 public:
-  bwp_ue() = default;
-  explicit bwp_ue(ue_carrier& carrier_, tti_point tti_rx_);
-  ~bwp_ue();
-  bwp_ue(bwp_ue&& other) noexcept : carrier(other.carrier) { other.carrier = nullptr; }
-  bwp_ue& operator=(bwp_ue&& other) noexcept
-  {
-    carrier       = other.carrier;
-    other.carrier = nullptr;
-    return *this;
-  }
-  bool empty() const { return carrier == nullptr; }
+  slot_ue() = default;
+  explicit slot_ue(bool& busy_signal, tti_point tti_rx_, uint32_t cc);
+  ~slot_ue();
+  slot_ue(slot_ue&&) noexcept = default;
+  slot_ue& operator=(slot_ue&&) noexcept = default;
+  bool     empty() const { return busy_signal == nullptr; }
+  void     release();
 
   tti_point tti_rx;
   uint32_t  cc = SCHED_NR_MAX_CARRIERS;
 
+  // UE parameters common to all sectors
   const sched_nr_ue_cfg* cfg = nullptr;
   bool                   pending_sr;
 
+  // UE parameters that are sector specific
+  uint32_t   dl_cqi;
+  uint32_t   ul_cqi;
+  harq_proc* h_dl = nullptr;
+  harq_proc* h_ul = nullptr;
+
 private:
-  ue_carrier* carrier = nullptr;
+  struct noop {
+    void operator()(bool* ptr) {}
+  };
+  std::unique_ptr<bool, noop> busy_signal;
 };
 
 class ue_carrier
 {
 public:
   ue_carrier(uint16_t rnti, uint32_t cc, const sched_nr_ue_cfg& cfg);
-  bwp_ue try_reserve(tti_point tti_rx);
-  void   push_feedback(srsran::move_callback<void(ue_carrier&)> callback);
+  slot_ue try_reserve(tti_point tti_rx, const sched_nr_ue_cfg& cfg);
+  void    push_feedback(srsran::move_callback<void(ue_carrier&)> callback);
+  void    set_cfg(const sched_nr_ue_cfg& uecfg);
 
   const uint16_t rnti;
   const uint32_t cc;
 
+  // Channel state
+  uint32_t dl_cqi = 1;
+  uint32_t ul_cqi = 0;
+
   harq_entity harq_ent;
 
 private:
-  friend class bwp_ue;
-  void release() { busy = false; }
+  const sched_nr_ue_cfg* cfg = nullptr;
 
-  const sched_nr_ue_cfg* cfg;
+  bool      busy{false};
+  tti_point last_tti_rx;
 
   srsran::deque<srsran::move_callback<void(ue_carrier&)> > pending_feedback;
-  bool                                                     busy{false};
 };
 
 class ue
@@ -77,7 +88,7 @@ class ue
 public:
   ue(uint16_t rnti, const sched_nr_ue_cfg& cfg);
 
-  bwp_ue try_reserve(tti_point tti_rx, uint32_t cc);
+  slot_ue try_reserve(tti_point tti_rx, uint32_t cc);
 
   void set_cfg(const sched_nr_ue_cfg& cfg);
 
diff --git a/srsenb/hdr/stack/mac/nr/sched_nr_worker.h b/srsenb/hdr/stack/mac/nr/sched_nr_worker.h
index 67a31878f..af1c79734 100644
--- a/srsenb/hdr/stack/mac/nr/sched_nr_worker.h
+++ b/srsenb/hdr/stack/mac/nr/sched_nr_worker.h
@@ -14,6 +14,7 @@
 #define SRSRAN_SCHED_NR_WORKER_H
 
 #include "sched_nr_common.h"
+#include "sched_nr_rb_grid.h"
 #include "sched_nr_ue.h"
 #include "srsran/adt/circular_array.h"
 #include "srsran/adt/optional.h"
@@ -26,23 +27,27 @@
 namespace srsenb {
 namespace sched_nr_impl {
 
-class bwp_worker
+class carrier_slot_worker
 {
 public:
-  explicit bwp_worker(uint32_t cc_, ue_map_t& ue_db_) : cc(cc_), ue_db(ue_db_) {}
+  explicit carrier_slot_worker(uint32_t cc_, const sched_nr_cfg& cfg_) : cc(cc_), cfg(cfg_), res_grid(cc, cfg) {}
 
-  void start(tti_point tti_rx_);
+  void start(tti_point tti_rx_, sched_nr_res_t& bwp_result, ue_map_t& ue_db_);
   void run();
   void end_tti();
   bool running() const { return tti_rx.is_valid(); }
 
 private:
-  ue_map_t& ue_db;
+  void alloc_dl_ues();
+  void alloc_ul_ues();
+
+  const uint32_t      cc;
+  const sched_nr_cfg& cfg;
 
   tti_point tti_rx;
-  uint32_t  cc;
+  slot_grid res_grid;
 
-  srsran::circular_array<bwp_ue, SCHED_NR_MAX_USERS> bwp_ues;
+  srsran::static_circular_map<uint16_t, slot_ue, SCHED_NR_MAX_USERS> slot_ues;
 };
 
 class sched_worker_manager
@@ -55,22 +60,23 @@ public:
 
   void reserve_workers(tti_point tti_rx, srsran::span<sched_nr_res_t> sf_result_);
   void start_tti(tti_point tti_rx);
-  bool run_tti(tti_point tti_rx, uint32_t cc);
+  bool run_tti(tti_point tti_rx, uint32_t cc, sched_nr_res_t& result);
   void end_tti(tti_point tti_rx);
 
 private:
   const sched_nr_cfg& cfg;
+  ue_map_t&           ue_db;
 
-  struct sf_worker_ctxt {
-    sem_t                        sf_sem;
-    tti_point                    tti_rx;
-    srsran::span<sched_nr_res_t> sf_result;
-    int                          worker_count = 0;
-    std::vector<bwp_worker>      workers;
+  struct slot_worker_ctxt {
+    sem_t                            sf_sem;
+    tti_point                        tti_rx;
+    srsran::span<sched_nr_res_t>     sf_result;
+    int                              worker_count = 0;
+    std::vector<carrier_slot_worker> workers;
   };
-  std::vector<std::unique_ptr<sf_worker_ctxt> > sf_ctxts;
+  std::vector<std::unique_ptr<slot_worker_ctxt> > slot_ctxts;
 
-  sf_worker_ctxt& get_sf(tti_point tti_rx);
+  slot_worker_ctxt& get_sf(tti_point tti_rx);
 };
 
 } // namespace sched_nr_impl
diff --git a/srsenb/src/stack/mac/nr/CMakeLists.txt b/srsenb/src/stack/mac/nr/CMakeLists.txt
index ee33f96bc..480fb0d24 100644
--- a/srsenb/src/stack/mac/nr/CMakeLists.txt
+++ b/srsenb/src/stack/mac/nr/CMakeLists.txt
@@ -6,6 +6,6 @@
 # the distribution.
 #
 
-set(SOURCES mac_nr.cc sched_nr.cc sched_nr_ue.cc sched_nr_worker.cc)
+set(SOURCES mac_nr.cc sched_nr.cc sched_nr_ue.cc sched_nr_worker.cc sched_nr_rb_grid.cc sched_nr_harq.cc)
 
 add_library(srsgnb_mac STATIC ${SOURCES})
diff --git a/srsenb/src/stack/mac/nr/sched_nr.cc b/srsenb/src/stack/mac/nr/sched_nr.cc
index 83423f734..8d0797318 100644
--- a/srsenb/src/stack/mac/nr/sched_nr.cc
+++ b/srsenb/src/stack/mac/nr/sched_nr.cc
@@ -15,7 +15,6 @@
 
 namespace srsenb {
 
-using sched_nr_impl::bwp_worker;
 using sched_nr_impl::sched_worker_manager;
 using sched_nr_impl::ue;
 using sched_nr_impl::ue_carrier;
@@ -100,7 +99,7 @@ void sched_nr::ue_cfg_impl(uint16_t rnti, const sched_nr_ue_cfg& uecfg)
 
 void sched_nr::new_tti(tti_point tti_rx)
 {
-  // Lock subframe workers to provided tti_rx
+  // Lock slot workers for provided tti_rx
   sched_workers.reserve_workers(tti_rx, sched_results[tti_rx.sf_idx()]);
 
   {
@@ -113,33 +112,25 @@ void sched_nr::new_tti(tti_point tti_rx)
   }
 }
 
+/// Generate {tti,cc} scheduling decision
 int sched_nr::generate_sched_result(tti_point tti_rx, uint32_t cc, sched_nr_res_t& result)
-{
-  // Generate {tti,cc} scheduling decision
-  run_tti(tti_rx, cc);
-
-  // copy scheduling decision result
-  result = sched_results[tti_rx.sf_idx()][cc];
-
-  return SRSRAN_SUCCESS;
-}
-
-void sched_nr::run_tti(tti_point tti_rx, uint32_t cc)
 {
   // unlocked, parallel region
-  bool all_workers_finished = sched_workers.run_tti(tti_rx, cc);
+  bool all_workers_finished = sched_workers.run_tti(tti_rx, cc, result);
 
   if (all_workers_finished) {
     // once all workers of the same subframe finished, synchronize sched outcome with ue_db
     std::lock_guard<std::mutex> lock(ue_db_mutex);
     sched_workers.end_tti(tti_rx);
   }
+
+  return SRSRAN_SUCCESS;
 }
 
-void sched_nr::dl_ack_info(tti_point tti_rx, uint16_t rnti, uint32_t cc, uint32_t tb_idx, bool ack)
+void sched_nr::dl_ack_info(uint16_t rnti, uint32_t pid, uint32_t cc, uint32_t tb_idx, bool ack)
 {
   pending_events->push_cc_feedback(
-      rnti, cc, [tti_rx, tb_idx, ack](ue_carrier& ue_cc) { ue_cc.harq_ent.dl_ack_info(tti_rx, tb_idx, ack); });
+      rnti, cc, [pid, tb_idx, ack](ue_carrier& ue_cc) { ue_cc.harq_ent.dl_ack_info(pid, tb_idx, ack); });
 }
 
 void sched_nr::ul_sr_info(tti_point tti_rx, uint16_t rnti)
diff --git a/srsenb/src/stack/mac/nr/sched_nr_harq.cc b/srsenb/src/stack/mac/nr/sched_nr_harq.cc
new file mode 100644
index 000000000..9c9c0c627
--- /dev/null
+++ b/srsenb/src/stack/mac/nr/sched_nr_harq.cc
@@ -0,0 +1,46 @@
+/**
+ *
+ * \section COPYRIGHT
+ *
+ * Copyright 2013-2021 Software Radio Systems Limited
+ *
+ * By using this file, you agree to the terms and conditions set
+ * forth in the LICENSE file which can be found at the top level of
+ * the distribution.
+ *
+ */
+
+#include "srsenb/hdr/stack/mac/nr/sched_nr_harq.h"
+
+namespace srsenb {
+namespace sched_nr_impl {
+
+bool harq_proc::new_tx(tti_point tti_tx_, const rbgmask_t& rbgmask_, uint32_t mcs, uint32_t ack_delay_)
+{
+  if (not empty()) {
+    return false;
+  }
+  tti_tx    = tti_tx_;
+  ack_delay = ack_delay_;
+  rbgmask   = rbgmask_;
+  tb[0].mcs = mcs;
+  return true;
+}
+
+harq_entity::harq_entity()
+{
+  dl_harqs.reserve(SCHED_NR_NOF_HARQS);
+  ul_harqs.reserve(SCHED_NR_NOF_HARQS);
+  for (uint32_t pid = 0; pid < SCHED_NR_NOF_HARQS; ++pid) {
+    dl_harqs.emplace_back(pid);
+    ul_harqs.emplace_back(pid);
+  }
+}
+
+void harq_entity::new_tti(tti_point tti_rx_)
+{
+  tti_rx = tti_rx_;
+}
+
+} // namespace sched_nr_impl
+} // namespace srsenb
\ No newline at end of file
diff --git a/srsenb/src/stack/mac/nr/sched_nr_rb_grid.cc b/srsenb/src/stack/mac/nr/sched_nr_rb_grid.cc
new file mode 100644
index 000000000..c27ff43a7
--- /dev/null
+++ b/srsenb/src/stack/mac/nr/sched_nr_rb_grid.cc
@@ -0,0 +1,80 @@
+/**
+ *
+ * \section COPYRIGHT
+ *
+ * Copyright 2013-2021 Software Radio Systems Limited
+ *
+ * By using this file, you agree to the terms and conditions set
+ * forth in the LICENSE file which can be found at the top level of
+ * the distribution.
+ *
+ */
+
+#include "srsenb/hdr/stack/mac/nr/sched_nr_rb_grid.h"
+
+namespace srsenb {
+namespace sched_nr_impl {
+
+slot_grid::slot_grid(uint32_t cc_, const sched_nr_cfg& cfg_) : cc(cc_), cfg(cfg_) {}
+
+void slot_grid::new_tti(tti_point tti_rx_, sched_nr_res_t& sched_res_)
+{
+  tti_rx    = tti_rx_;
+  sched_res = &sched_res_;
+
+  pdsch_mask.reset();
+  pusch_mask.reset();
+  *sched_res = {};
+}
+
+bool slot_grid::alloc_pdsch(slot_ue& ue, const rbgmask_t& dl_mask)
+{
+  const uint32_t tbs = 100, mcs = 20;
+  if (ue.h_dl == nullptr) {
+    return false;
+  }
+  if ((pdsch_mask & dl_mask).any()) {
+    return false;
+  }
+  if (sched_res->dl_res.data.full()) {
+    return false;
+  }
+  if (not ue.h_dl->new_tx(tti_tx_dl(), dl_mask, mcs, K1)) {
+    return false;
+  }
+
+  pdsch_mask |= dl_mask;
+  sched_res->dl_res.data.emplace_back();
+  sched_nr_data_t& data = sched_res->dl_res.data.back();
+  data.tbs.resize(1);
+  data.tbs[0] = tbs;
+
+  return true;
+}
+
+bool slot_grid::alloc_pusch(slot_ue& ue, const rbgmask_t& ul_mask)
+{
+  const uint32_t tbs = 100, mcs = 20;
+  if ((pusch_mask & ul_mask).any()) {
+    return false;
+  }
+  if (sched_res->ul_res.pusch.full()) {
+    return false;
+  }
+  if (not ue.h_ul->new_tx(tti_tx_ul(), ul_mask, mcs, 0)) {
+    return false;
+  }
+
+  pusch_mask |= ul_mask;
+  sched_res->ul_res.pusch.emplace_back();
+  sched_nr_data_t& data = sched_res->ul_res.pusch.back();
+  data.tbs.resize(1);
+  data.tbs[0] = tbs;
+
+  return true;
+}
+
+void slot_grid::generate_dcis() {}
+
+} // namespace sched_nr_impl
+} // namespace srsenb
\ No newline at end of file
diff --git a/srsenb/src/stack/mac/nr/sched_nr_ue.cc b/srsenb/src/stack/mac/nr/sched_nr_ue.cc
index c772978e6..9d3d0dbef 100644
--- a/srsenb/src/stack/mac/nr/sched_nr_ue.cc
+++ b/srsenb/src/stack/mac/nr/sched_nr_ue.cc
@@ -15,36 +15,86 @@
 namespace srsenb {
 namespace sched_nr_impl {
 
-bwp_ue::bwp_ue(ue_carrier& carrier_, tti_point tti_rx_) : carrier(&carrier_), tti_rx(tti_rx_), cc(carrier_.cc) {}
+slot_ue::slot_ue(bool& busy_signal_, tti_point tti_rx_, uint32_t cc_) :
+  busy_signal(&busy_signal_), tti_rx(tti_rx_), cc(cc_)
+{}
 
-bwp_ue::~bwp_ue()
+slot_ue::~slot_ue()
 {
-  if (carrier != nullptr) {
-    carrier->release();
+  release();
+}
+
+void slot_ue::release()
+{
+  if (busy_signal != nullptr) {
+    *busy_signal = false;
   }
 }
 
-ue_carrier::ue_carrier(uint16_t rnti_, uint32_t cc_, const sched_nr_ue_cfg& cfg_) : rnti(rnti_), cc(cc_), cfg(&cfg_) {}
+///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+ue_carrier::ue_carrier(uint16_t rnti_, uint32_t cc_, const sched_nr_ue_cfg& uecfg_) : rnti(rnti_), cc(cc_), cfg(&uecfg_)
+{}
+
+void ue_carrier::set_cfg(const sched_nr_ue_cfg& uecfg)
+{
+  cfg = &uecfg;
+}
 
 void ue_carrier::push_feedback(srsran::move_callback<void(ue_carrier&)> callback)
 {
   pending_feedback.push_back(std::move(callback));
 }
 
-bwp_ue ue_carrier::try_reserve(tti_point tti_rx)
+slot_ue ue_carrier::try_reserve(tti_point tti_rx, const sched_nr_ue_cfg& uecfg_)
 {
-  if (busy) {
-    return bwp_ue();
+  slot_ue sfu = (busy) ? slot_ue() : slot_ue(busy, tti_rx, cc);
+  if (sfu.empty()) {
+    return sfu;
   }
-  // successfully acquired
+  // successfully acquired. Process any CC-specific pending feedback
   busy = true;
+  if (cfg != &uecfg_) {
+    set_cfg(uecfg_);
+  }
   while (not pending_feedback.empty()) {
     pending_feedback.front()(*this);
     pending_feedback.pop_front();
   }
-  return bwp_ue(*this, tti_rx);
+  if (not last_tti_rx.is_valid()) {
+    last_tti_rx = tti_rx;
+    harq_ent.new_tti(tti_rx);
+  } else {
+    while (last_tti_rx++ < tti_rx) {
+      harq_ent.new_tti(tti_rx);
+    }
+  }
+
+  // set UE parameters common to all carriers
+  sfu.cfg = &uecfg_;
+
+  // copy cc-specific parameters and find available HARQs
+  sfu.dl_cqi = dl_cqi;
+  sfu.ul_cqi = ul_cqi;
+  sfu.h_dl   = harq_ent.find_pending_dl_retx();
+  if (sfu.h_dl == nullptr) {
+    sfu.h_dl = harq_ent.find_empty_dl_harq();
+  }
+  sfu.h_ul = harq_ent.find_pending_ul_retx();
+  if (sfu.h_ul == nullptr) {
+    sfu.h_ul = harq_ent.find_empty_ul_harq();
+  }
+
+  if (sfu.h_dl == nullptr and sfu.h_ul == nullptr) {
+    // there needs to be at least one available HARQ for newtx/retx
+    sfu.release();
+    return sfu;
+  }
+  return sfu;
 }
 
+///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
 ue::ue(uint16_t rnti, const sched_nr_ue_cfg& cfg)
 {
   for (uint32_t cc = 0; cc < cfg.carriers.size(); ++cc) {
@@ -60,18 +110,17 @@ void ue::set_cfg(const sched_nr_ue_cfg& cfg)
   ue_cfgs[current_idx] = cfg;
 }
 
-bwp_ue ue::try_reserve(tti_point tti_rx, uint32_t cc)
+slot_ue ue::try_reserve(tti_point tti_rx, uint32_t cc)
 {
   if (carriers[cc] == nullptr) {
-    return bwp_ue();
+    return slot_ue();
   }
-  bwp_ue sfu = carriers[cc]->try_reserve(tti_rx);
+  slot_ue sfu = carriers[cc]->try_reserve(tti_rx, ue_cfgs[current_idx]);
   if (sfu.empty()) {
-    return bwp_ue();
+    return slot_ue();
   }
   // set UE-common parameters
   sfu.pending_sr = pending_sr;
-  sfu.cfg        = &ue_cfgs[current_idx];
 
   return sfu;
 }
diff --git a/srsenb/src/stack/mac/nr/sched_nr_worker.cc b/srsenb/src/stack/mac/nr/sched_nr_worker.cc
index 1f673a086..be64998ac 100644
--- a/srsenb/src/stack/mac/nr/sched_nr_worker.cc
+++ b/srsenb/src/stack/mac/nr/sched_nr_worker.cc
@@ -16,7 +16,7 @@ namespace srsenb {
 namespace sched_nr_impl {
 
 /// Called at the beginning of TTI in a locked context, to reserve available UE resources
-void bwp_worker::start(tti_point tti_rx_)
+void carrier_slot_worker::start(tti_point tti_rx_, sched_nr_res_t& bwp_result_, ue_map_t& ue_db)
 {
   srsran_assert(not running(), "scheduler worker::start() called for active worker");
   // Try reserve UE cells for this worker
@@ -24,63 +24,101 @@ void bwp_worker::start(tti_point tti_rx_)
     uint16_t rnti = ue_pair.first;
     ue&      u    = *ue_pair.second;
 
-    bwp_ue sfu0 = u.try_reserve(tti_rx, cc);
-    if (sfu0.empty()) {
+    slot_ues.insert(rnti, u.try_reserve(tti_rx, cc));
+    if (slot_ues[rnti].empty()) {
       // Failed to synchronize because UE is being used by another worker
+      slot_ues.erase(rnti);
       continue;
     }
-    // Synchronization of UE for this {tti, cc} was successful
-    bwp_ues[rnti] = std::move(sfu0);
+    // UE acquired successfully for scheduling in this {tti, cc}
   }
 
+  res_grid.new_tti(tti_rx_, bwp_result_);
   tti_rx = tti_rx_;
 }
 
-void bwp_worker::run()
+void carrier_slot_worker::run()
 {
   srsran_assert(running(), "scheduler worker::run() called for non-active worker");
+
+  // Prioritize PDCCH scheduling for DL and UL data in a RoundRobin fashion
+  if ((tti_rx.to_uint() & 0x1u) == 0) {
+    alloc_dl_ues();
+    alloc_ul_ues();
+  } else {
+    alloc_ul_ues();
+    alloc_dl_ues();
+  }
+
+  // Select the winner PDCCH allocation combination, store all the scheduling results
+  res_grid.generate_dcis();
 }
 
-void bwp_worker::end_tti()
+void carrier_slot_worker::end_tti()
 {
   srsran_assert(running(), "scheduler worker::end() called for non-active worker");
 
   // releases UE resources
-  for (bwp_ue& u : bwp_ues) {
-    if (not u.empty()) {
-      u = {};
-    }
-  }
+  slot_ues.clear();
 
   tti_rx = {};
 }
 
+void carrier_slot_worker::alloc_dl_ues()
+{
+  if (slot_ues.empty()) {
+    return;
+  }
+  slot_ue& ue = slot_ues.begin()->second;
+  if (ue.h_dl == nullptr) {
+    return;
+  }
+
+  rbgmask_t dlmask(cfg.cells[cc].nof_rbg);
+  dlmask.fill(0, dlmask.size(), true);
+  res_grid.alloc_pdsch(ue, dlmask);
+}
+void carrier_slot_worker::alloc_ul_ues()
+{
+  if (slot_ues.empty()) {
+    return;
+  }
+  slot_ue& ue = slot_ues.begin()->second;
+  if (ue.h_ul == nullptr) {
+    return;
+  }
+
+  rbgmask_t ulmask(cfg.cells[cc].nof_rbg);
+  ulmask.fill(0, ulmask.size(), true);
+  res_grid.alloc_pusch(ue, ulmask);
+}
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 
-sched_worker_manager::sched_worker_manager(ue_map_t& ue_db_, const sched_nr_cfg& cfg_) : cfg(cfg_)
+sched_worker_manager::sched_worker_manager(ue_map_t& ue_db_, const sched_nr_cfg& cfg_) : cfg(cfg_), ue_db(ue_db_)
 {
   // Note: For now, we only allow parallelism at the sector level
-  sf_ctxts.resize(cfg.nof_concurrent_subframes);
+  slot_ctxts.resize(cfg.nof_concurrent_subframes);
   for (size_t i = 0; i < cfg.nof_concurrent_subframes; ++i) {
-    sf_ctxts[i].reset(new sf_worker_ctxt());
-    sem_init(&sf_ctxts[i]->sf_sem, 0, 1);
-    sf_ctxts[i]->workers.reserve(cfg.cells.size());
+    slot_ctxts[i].reset(new slot_worker_ctxt());
+    sem_init(&slot_ctxts[i]->sf_sem, 0, 1);
+    slot_ctxts[i]->workers.reserve(cfg.cells.size());
     for (uint32_t cc = 0; cc < cfg.cells.size(); ++cc) {
-      sf_ctxts[i]->workers.emplace_back(cc, ue_db_);
+      slot_ctxts[i]->workers.emplace_back(cc, cfg);
     }
   }
 }
 
 sched_worker_manager::~sched_worker_manager()
 {
-  for (uint32_t sf = 0; sf < sf_ctxts.size(); ++sf) {
-    sem_destroy(&sf_ctxts[sf]->sf_sem);
+  for (uint32_t sf = 0; sf < slot_ctxts.size(); ++sf) {
+    sem_destroy(&slot_ctxts[sf]->sf_sem);
   }
 }
 
-sched_worker_manager::sf_worker_ctxt& sched_worker_manager::get_sf(tti_point tti_rx)
+sched_worker_manager::slot_worker_ctxt& sched_worker_manager::get_sf(tti_point tti_rx)
 {
-  return *sf_ctxts[tti_rx.to_uint() % sf_ctxts.size()];
+  return *slot_ctxts[tti_rx.to_uint() % slot_ctxts.size()];
 }
 
 void sched_worker_manager::reserve_workers(tti_point tti_rx_, srsran::span<sched_nr_res_t> sf_result_)
@@ -91,7 +129,7 @@ void sched_worker_manager::reserve_workers(tti_point tti_rx_, srsran::span<sched
 
   sf_worker_ctxt.sf_result    = sf_result_;
   sf_worker_ctxt.tti_rx       = tti_rx_;
-  sf_worker_ctxt.worker_count = sf_worker_ctxt.workers.size();
+  sf_worker_ctxt.worker_count = static_cast<int>(sf_worker_ctxt.workers.size());
 }
 
 void sched_worker_manager::start_tti(tti_point tti_rx_)
@@ -100,11 +138,11 @@ void sched_worker_manager::start_tti(tti_point tti_rx_)
   srsran_assert(sf_worker_ctxt.tti_rx == tti_rx_, "invalid run_tti(tti, cc) arguments");
 
   for (uint32_t cc = 0; cc < sf_worker_ctxt.workers.size(); ++cc) {
-    sf_worker_ctxt.workers[cc].start(sf_worker_ctxt.tti_rx);
+    sf_worker_ctxt.workers[cc].start(sf_worker_ctxt.tti_rx, sf_worker_ctxt.sf_result[cc], ue_db);
   }
 }
 
-bool sched_worker_manager::run_tti(tti_point tti_rx_, uint32_t cc)
+bool sched_worker_manager::run_tti(tti_point tti_rx_, uint32_t cc, sched_nr_res_t& result)
 {
   auto& sf_worker_ctxt = get_sf(tti_rx_);
   srsran_assert(sf_worker_ctxt.tti_rx == tti_rx_, "invalid run_tti(tti, cc) arguments");
@@ -116,6 +154,9 @@ bool sched_worker_manager::run_tti(tti_point tti_rx_, uint32_t cc)
   // Get {tti, cc} scheduling decision
   sf_worker_ctxt.workers[cc].run();
 
+  // copy sched result
+  result = sf_worker_ctxt.sf_result[cc];
+
   // decrement the number of active workers
   --sf_worker_ctxt.worker_count;
   srsran_assert(sf_worker_ctxt.worker_count >= 0, "invalid number of calls to run_tti(tti, cc)");
@@ -132,6 +173,8 @@ void sched_worker_manager::end_tti(tti_point tti_rx_)
   for (auto& worker : sf_worker_ctxt.workers) {
     worker.end_tti();
   }
+
+  sf_worker_ctxt.sf_result = {};
   sem_post(&sf_worker_ctxt.sf_sem);
 }
 
diff --git a/srsenb/test/mac/nr/sched_nr_test.cc b/srsenb/test/mac/nr/sched_nr_test.cc
index 338e514b6..3a2d3da13 100644
--- a/srsenb/test/mac/nr/sched_nr_test.cc
+++ b/srsenb/test/mac/nr/sched_nr_test.cc
@@ -112,7 +112,7 @@ void sched_nr_cfg_parallel_sf_test()
 
 int main()
 {
-  srsran::get_background_workers().set_nof_workers(4);
+  srsran::get_background_workers().set_nof_workers(8);
 
   srsenb::sched_nr_cfg_serialized_test();
   srsenb::sched_nr_cfg_parallel_cc_test();