SRSUE: initial scell sync

SRSUE: SCell Synch feedbacks delay

SRSUE: Implemented SCell Radio offset correction

lib/include/srslte/interfaces/radio_interfaces.h

@@ -186,6 +186,14 @@ public:
    */
   virtual void set_rx_srate(const double& srate) = 0;
 
+  /**
+   * Sets relative offset between receiver channels. It does not guarantee that the offset is corrected by the radio
+   * implementation.
+   * @param ch logical channel index
+   * @param offset_samples Offset in samples, it can be negative
+   */
+  virtual void set_channel_rx_offset(uint32_t ch, int32_t offset_samples) = 0;
+
   // getter
   virtual double            get_freq_offset()       = 0;
   virtual float             get_rx_gain()           = 0;

lib/include/srslte/radio/radio.h

@@ -73,6 +73,7 @@ public:
   void set_rx_gain(const float& gain) override;
   void set_tx_srate(const double& srate) override;
   void set_rx_srate(const double& srate) override;
+  void set_channel_rx_offset(uint32_t ch, int32_t offset_samples) override;
 
   // getter
   double            get_freq_offset() override;
@@ -92,6 +93,7 @@ public:
 private:
   std::vector<srslte_rf_t>      rf_devices  = {};
   std::vector<srslte_rf_info_t> rf_info     = {};
+  std::vector<int32_t>          rx_offset_n = {};
   rf_metrics_t                  rf_metrics  = {};
   log_filter                    log_local   = {};
   log_filter*                   log_h       = nullptr;
@@ -163,9 +165,7 @@ private:
    * @param tx_time_ Timestamp to transmit (read only)
    * @return it returns true if the transmission was successful, otherwise it returns false
    */
-  bool tx_dev(const uint32_t&           device_idx,
-              rf_buffer_interface&      buffer,
-              const srslte_timestamp_t& tx_time_);
+  bool tx_dev(const uint32_t& device_idx, rf_buffer_interface& buffer, const srslte_timestamp_t& tx_time_);
 
   /**
    * Helper method for receiving over a single RF device. This function maps automatically the logical receive buffers
@@ -176,9 +176,7 @@ private:
    * @param rxd_time Points at the receive time (write only)
    * @return it returns true if the reception was successful, otherwise it returns false
    */
-  bool rx_dev(const uint32_t&            device_idx,
-              const rf_buffer_interface& buffer,
-              srslte_timestamp_t*        rxd_time);
+  bool rx_dev(const uint32_t& device_idx, const rf_buffer_interface& buffer, srslte_timestamp_t* rxd_time);
 
   /**
    * Helper method for mapping logical channels into physical radio buffers.

lib/src/radio/radio.cc

@@ -108,6 +108,7 @@ int radio::init(const rf_args_t& args, phy_interface_radio* phy_)
   // Allocate RF devices
   rf_devices.resize(device_args_list.size());
   rf_info.resize(device_args_list.size());
+  rx_offset_n.resize(device_args_list.size());
 
   // Init and start Radios
   for (uint32_t device_idx = 0; device_idx < (uint32_t)device_args_list.size(); device_idx++) {
@@ -247,8 +248,39 @@ bool radio::rx_dev(const uint32_t&            device_idx,
     return false;
   }
 
-  int ret = srslte_rf_recv_with_time_multi(
-      &rf_devices[device_idx], radio_buffers, buffer.get_nof_samples(), true, full_secs, frac_secs);
+  // Apply Rx offset into the number of samples and reset value
+  int      nof_samples_offset = rx_offset_n.at(device_idx);
+  uint32_t nof_samples        = buffer.get_nof_samples();
+
+  // Number of samples adjust from device time offset
+  if (nof_samples_offset < 0 and (uint32_t)(-nof_samples_offset) > nof_samples) {
+    // Avoid overflow subtraction
+    nof_samples = 0;
+  } else {
+    // Limit the number of samples to a maximum of 2 times the requested number of samples
+    nof_samples = SRSLTE_MIN(nof_samples + nof_samples_offset, 2 * nof_samples);
+  }
+
+  // Subtract number of offset samples
+  rx_offset_n.at(device_idx) = nof_samples_offset - ((int)nof_samples - (int)buffer.get_nof_samples());
+
+  int ret =
+      srslte_rf_recv_with_time_multi(&rf_devices[device_idx], radio_buffers, nof_samples, true, full_secs, frac_secs);
+
+  // If the number of received samples filled the buffer, there is nothing else to do
+  if (buffer.get_nof_samples() <= nof_samples) {
+    return ret > 0;
+  }
+
+  // Otherwise, set rest of buffer to zero
+  uint32_t nof_zeros = buffer.get_nof_samples() - nof_samples;
+  for (auto& b : radio_buffers) {
+    if (b != nullptr) {
+      cf_t* ptr = (cf_t*)b;
+      srslte_vec_cf_zero(&ptr[nof_samples], nof_zeros);
+    }
+  }
+
   return ret > 0;
 }
 
@@ -491,6 +523,26 @@ void radio::set_rx_srate(const double& srate)
   }
 }
 
+void radio::set_channel_rx_offset(uint32_t ch, int32_t offset_samples)
+{
+  int physical_channel_idx = rx_channel_mapping.get_carrier_idx(ch);
+
+  // Return if invalid index
+  if (physical_channel_idx < SRSLTE_SUCCESS) {
+    return;
+  }
+
+  // Calculate device index
+  uint32_t device_idx = (nof_antennas * (uint32_t)physical_channel_idx) / nof_channels_x_dev;
+
+  // Bound device index
+  if (device_idx >= rx_offset_n.size()) {
+    return;
+  }
+
+  rx_offset_n[ch] = offset_samples;
+}
+
 void radio::set_tx_freq(const uint32_t& carrier_idx, const double& freq)
 {
   if (!is_initialized) {

srsenb/test/phy/enb_phy_test.cc

@@ -247,6 +247,7 @@ public:
   void              set_rx_gain(const float& gain) override {}
   void              set_tx_srate(const double& srate) override {}
   void              set_rx_srate(const double& srate) override { rx_srate = srate; }
+  void              set_channel_rx_offset(uint32_t ch, int32_t offset_samples) override{};
   void              set_tx_gain(const float& gain) override {}
   float             get_rx_gain() override { return 0; }
   double            get_freq_offset() override { return 0; }

srsue/hdr/phy/scell/scell_sync.h

@@ -0,0 +1,192 @@
+/*
+ * Copyright 2013-2020 Software Radio Systems Limited
+ *
+ * This file is part of srsLTE.
+ *
+ * srsLTE is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * srsLTE is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * A copy of the GNU Affero General Public License can be found in
+ * the LICENSE file in the top-level directory of this distribution
+ * and at http://www.gnu.org/licenses/.
+ *
+ */
+
+#ifndef SRSLTE_SCELL_SYNC_H
+#define SRSLTE_SCELL_SYNC_H
+
+namespace srsue {
+namespace scell {
+
+/**
+ * Radio feedback interface
+ */
+class sync_callback
+{
+public:
+  /**
+   * Provides secondary serving cell synchronization feedback
+   * @param ch channel index
+   * @param offset Number of samples to offset
+   */
+  virtual void set_rx_channel_offset(uint32_t ch, int32_t offset) = 0;
+};
+
+class sync
+{
+private:
+  /**
+   * FSM
+   *
+   *  Init   +------+ Set cell  +------------+ PSS found +----------+
+   *   or -->| IDLE |---------->| Search PSS |---------->| In-Synch |
+   *  Stop   +------+           +------------+           +----------+
+   *                                   ^ Set Cell             |
+   *                                   |                      |
+   *                                   +----------------------+
+   */
+  typedef enum { STATE_IDLE = 0, STATE_SEARCH_PSS, STATE_IN_SYNCH } state_t;
+
+  state_t                             state    = STATE_IDLE;
+  sync_callback*                      callback = nullptr;
+  uint32_t                            channel  = 0;
+  srslte_sync_t                       find_pss = {};
+  int32_t                             sf_len   = 0;
+  std::array<cf_t, SRSLTE_SF_LEN_MAX> temp;
+
+  /**
+   * Executes the PSS search state
+   * @param tti
+   * @param buffer
+   */
+  void run_state_search_pss(uint32_t tti, cf_t* buffer)
+  {
+    uint32_t peak_pos = 0;
+
+    // Append new base-band
+    srslte_vec_cf_copy(&temp[sf_len], buffer, sf_len);
+
+    // Run PSS search
+    switch (srslte_sync_find(&find_pss, temp.data(), 0, &peak_pos)) {
+
+      case SRSLTE_SYNC_FOUND:
+        if (callback != nullptr) {
+          // Calculate Sample Offset from TTI difference
+          int tti_mod    = (int)tti % (SRSLTE_NOF_SF_X_FRAME / 2);
+          int tti_offset = (tti_mod < 3) ? tti_mod : (tti_mod - SRSLTE_NOF_SF_X_FRAME / 2);
+
+          // Calculate sample offset from PSS correlation peak
+          int offset = (int)(peak_pos - (3 * sf_len) / 2);
+
+          // Provide offset through feedback interface
+          callback->set_rx_channel_offset(channel, offset + tti_offset * sf_len);
+        }
+        state = STATE_IN_SYNCH;
+        break;
+      case SRSLTE_SYNC_FOUND_NOSPACE:
+        ERROR("No space error\n");
+        break;
+      case SRSLTE_SYNC_NOFOUND:
+        // Ignore
+        break;
+      case SRSLTE_SYNC_ERROR:
+        ERROR("Error finding PSS\n");
+        break;
+    }
+
+    // If the state has not changed, copy new data into the temp buffer
+    if (state == STATE_SEARCH_PSS) {
+      srslte_vec_cf_copy(&temp[0], buffer, sf_len);
+    }
+  }
+
+public:
+  /**
+   * Constructor
+   * @param _callback provides the class for giving feedback
+   * @param _channel provides the channel index where the feedback needs to be applied
+   */
+  sync(sync_callback* _callback, uint32_t _channel) : callback(_callback), channel(_channel)
+  {
+    // Initialise Find PSS object
+    if (srslte_sync_init(&find_pss, SRSLTE_SF_LEN_MAX, SRSLTE_SF_LEN_MAX, SRSLTE_SYMBOL_SZ_MAX) != SRSLTE_SUCCESS) {
+      ERROR("Initiating Synchroniser\n");
+    }
+  }
+
+  /**
+   * Sets the cell for the synchronizer
+   */
+  void set_cell(const srslte_cell_t& cell)
+  {
+    uint32_t symbol_sz = srslte_symbol_sz(cell.nof_prb);
+    sf_len             = SRSLTE_SF_LEN_PRB(cell.nof_prb);
+
+    // Resize Sync object
+    if (srslte_sync_resize(&find_pss, 2 * sf_len, 2 * sf_len, symbol_sz) != SRSLTE_SUCCESS) {
+      ERROR("Error setting cell sync find\n");
+    }
+
+    // Configure
+    srslte_sync_set_frame_type(&find_pss, cell.frame_type);
+    srslte_sync_set_N_id_2(&find_pss, cell.id % SRSLTE_NOF_NID_2);
+    srslte_sync_set_N_id_1(&find_pss, cell.id / SRSLTE_NOF_NID_2);
+    srslte_sync_set_cfo_ema_alpha(&find_pss, 0.1);
+    srslte_sync_set_em_alpha(&find_pss, 1);
+    srslte_sync_set_threshold(&find_pss, 3.0);
+
+    // Reset Temporal buffer
+    srslte_vec_cf_zero(temp.data(), 2 * sf_len);
+
+    // Go to search PSS
+    state = STATE_SEARCH_PSS;
+  }
+
+  /**
+   * Resets the class, goes back into IDLE mode
+   */
+  void stop() { state = STATE_IDLE; }
+
+  /**
+   * Runs internal FSM, performing Synchronization operations on the provided buffer. It expects data per sub-frame
+   * basis (1 ms).
+   * @param tti Current primary serving cell time
+   * @param buffer Base-band buffer of the given secondary serving cell
+   */
+  void run(uint32_t tti, cf_t* buffer)
+  {
+    switch (state) {
+      case STATE_IDLE:
+        // Do nothing
+        break;
+      case STATE_SEARCH_PSS:
+        run_state_search_pss(tti, buffer);
+        break;
+      case STATE_IN_SYNCH:
+        // Do nothing
+        break;
+    }
+  }
+
+  /**
+   * Get channel index
+   * @return The channel number it has been configured
+   */
+  uint32_t get_channel() const { return channel; }
+
+  /**
+   * Indicates whether the secondary serving cell assigned to the instance is in-sync
+   * @return true if it is in sync state
+   */
+  bool is_in_sync() const { return state == STATE_IN_SYNCH; }
+};
+} // namespace scell
+} // namespace srsue
+#endif // SRSLTE_SCELL_SYNC_H

srsue/hdr/phy/sync.h

@@ -30,6 +30,7 @@
 #include "phy_common.h"
 #include "prach.h"
 #include "scell/intra_measure.h"
+#include "scell/scell_sync.h"
 #include "search.h"
 #include "sf_worker.h"
 #include "sfn_sync.h"
@@ -47,7 +48,7 @@ namespace srsue {
 
 typedef _Complex float cf_t;
 
-class sync : public srslte::thread, public chest_feedback_itf, public search_callback
+class sync : public srslte::thread, public chest_feedback_itf, public search_callback, public scell::sync_callback
 {
 public:
   sync() : thread("SYNC"), sf_buffer(sync_nof_rx_subframes), dummy_buffer(sync_nof_rx_subframes){};
@@ -93,6 +94,25 @@ public:
 
   srslte::radio_interface_phy* get_radio() override { return radio_h; }
 
+  /**
+   * Sets secondary serving cell for synchronization purposes
+   * @param cc_idx component carrier index
+   * @param _cell Cell information
+   */
+  void scell_sync_set(uint32_t cc_idx, const srslte_cell_t& _cell);
+
+  /**
+   * Stops all secondary serving cell synchronization
+   */
+  void scell_sync_stop();
+
+  /**
+   * Implements Secondary Serving cell feedback
+   * @param ch Feedback channel
+   * @param offset Number of samples to offset
+   */
+  void set_rx_channel_offset(uint32_t ch, int32_t offset) override { radio_h->set_channel_rx_offset(ch, offset); }
+
 private:
   void reset();
   void radio_error();
@@ -180,6 +200,9 @@ private:
   // Object for synchronization of the primary cell
   srslte_ue_sync_t ue_sync = {};
 
+  // Object for synchronization secondary serving cells
+  std::vector<std::unique_ptr<scell::sync> > scell_sync;
+
   // Buffer for primary and secondary cell samples
   const static uint32_t sync_nof_rx_subframes = 5;
   srslte::rf_buffer_t   sf_buffer             = {};

srsue/src/phy/phy.cc

@@ -303,11 +303,13 @@ void phy::meas_stop()
 
 bool phy::cell_select(const phy_cell_t* cell)
 {
+  sfsync.scell_sync_stop();
   return sfsync.cell_select(cell);
 }
 
 phy_interface_rrc_lte::cell_search_ret_t phy::cell_search(phy_cell_t* cell)
 {
+  sfsync.scell_sync_stop();
   return sfsync.cell_search(cell);
 }
 
@@ -440,9 +442,12 @@ void phy::set_config(srslte::phy_cfg_t& config_, uint32_t cc_idx, uint32_t earfc
       workers[i]->set_config(cc_idx, config_);
     }
 
-    // Set inter-frequency measurement primary cell
     if (cell_info) {
+      // Set inter-frequency measurement
       sfsync.set_inter_frequency_measurement(cc_idx, earfcn, *cell_info);
+
+      // Set secondary serving cell synchronization
+      sfsync.scell_sync_set(cc_idx, *cell_info);
     }
 
     if (cc_idx == 0) {

srsue/src/phy/sync.cc

@@ -104,6 +104,12 @@ void sync::init(srslte::radio_interface_phy* _radio,
     intra_freq_meas.push_back(std::unique_ptr<scell::intra_measure>(q));
   }
 
+  // Allocate Secondary serving cell synchronization
+  for (uint32_t i = 1; i < worker_com->args->nof_carriers; i++) {
+    // Give the logical channel
+    scell_sync.push_back(std::unique_ptr<scell::sync>(new scell::sync(this, i * worker_com->args->nof_rx_ant)));
+  }
+
   reset();
   running = true;
 
@@ -380,6 +386,11 @@ void sync::run_camping_in_sync_state(sf_worker* worker, srslte::rf_buffer_t& syn
     force_camping_sfn_sync = true;
   }
 
+  // Run secondary serving cell synchronization
+  for (auto& e : scell_sync) {
+    e->run(tti, sync_buffer.get(e->get_channel(), 0, worker_com->args->nof_rx_ant));
+  }
+
   if (is_overflow) {
     force_camping_sfn_sync = true;
     is_overflow            = false;
@@ -927,4 +938,30 @@ void sync::meas_stop()
   }
 }
 
+void sync::scell_sync_set(uint32_t cc_idx, const srslte_cell_t& _cell)
+{
+  // Ignore if PCell
+  if (cc_idx == 0) {
+    return;
+  }
+
+  // Decrement to match SCell index
+  cc_idx--;
+
+  // Ignore if out of range
+  if (cc_idx >= scell_sync.size()) {
+    return;
+  }
+
+  // Set secondary serving cell
+  scell_sync[cc_idx]->set_cell(_cell);
+}
+
+void sync::scell_sync_stop()
+{
+  for (auto& e : scell_sync) {
+    e->stop();
+  }
+}
+
 } // namespace srsue

srsue/test/phy/ue_phy_test.cc

@@ -305,6 +305,7 @@ private:
       rx_srate = (float)srate;
       log_h.info("Set Rx sampling rate to %+.3f MHz.\n", srate * 1.0e-6);
     }
+    void  set_channel_rx_offset(uint32_t ch, int32_t offset_samples) override{};
     float get_rx_gain() override
     {
       std::unique_lock<std::mutex> lock(mutex);