dynamic bit selection based on the estimated power of the received signal.

src/algorithms/signal_source/adapters/ad9361_fpga_signal_source.cc

@@ -3,7 +3,10 @@
  * \brief signal source for Analog Devices front-end AD9361 connected directly to FPGA accelerators.
  * This source implements only the AD9361 control. It is NOT compatible with conventional SDR acquisition and tracking blocks.
  * Please use the fmcomms2 source if conventional SDR acquisition and tracking is selected in the configuration file.
- * \author Javier Arribas, jarribas(at)cttc.es
+ * \authors <ul>
+ *          <li> Javier Arribas, jarribas(at)cttc.es
+ *          <li> Marc Majoral, mmajoral(at)cttc.es
+ *          </ul>
  *
  * -------------------------------------------------------------------------
  *
@@ -288,6 +291,18 @@ Ad9361FpgaSignalSource::Ad9361FpgaSignalSource(const ConfigurationInterface *con
                 }
         }
 
+    // dynamic bits selection
+    enable_dynamic_bit_selection_ = configuration->property(role + ".enable_dynamic_bit_selection", true);
+    if (enable_dynamic_bit_selection_)
+        {
+            std::string dynamic_bit_selection_default_device_name1 = "/dev/uio48";
+            std::string device_name1 = configuration->property(role + ".dyn_bits_sel_devicename", dynamic_bit_selection_default_device_name1);
+            std::string dynamic_bit_selection_default_device_name2 = "/dev/uio49";
+            std::string device_name2 = configuration->property(role + ".dyn_bits_sel_devicename", dynamic_bit_selection_default_device_name2);
+            dynamic_bit_selection_fpga = std::make_shared<Fpga_dynamic_bit_selection>(device_name1, device_name2);
+            thread_dynamic_bit_selection = std::thread([&] { run_dynamic_bit_selection_process(); });
+        }
+
     if (in_stream_ > 0)
         {
             LOG(ERROR) << "A signal source does not have an input stream";
@@ -335,6 +350,22 @@ Ad9361FpgaSignalSource::~Ad9361FpgaSignalSource()
                         }
                 }
         }
+
+    std::unique_lock<std::mutex> lock(dynamic_bit_selection_mutex);
+    bool bit_selection_enabled = enable_dynamic_bit_selection_;
+    lock.unlock();
+
+    if (bit_selection_enabled == true)
+        {
+            std::unique_lock<std::mutex> lock(dynamic_bit_selection_mutex);
+            enable_dynamic_bit_selection_ = false;
+            lock.unlock();
+
+            if (thread_dynamic_bit_selection.joinable())
+                {
+                    thread_dynamic_bit_selection.join();
+                }
+        }
 }
 
 
@@ -576,6 +607,23 @@ void Ad9361FpgaSignalSource::run_DMA_process(const std::string &FreqBand, const
         }
 }
 
+void Ad9361FpgaSignalSource::run_dynamic_bit_selection_process(void)
+{
+    bool dynamic_bit_selection_active = true;
+
+    while (dynamic_bit_selection_active)
+        {
+            // setting the bit selection to the top bits
+            dynamic_bit_selection_fpga->bit_selection();
+            std::this_thread::sleep_for(std::chrono::milliseconds(Gain_control_period_ms));
+            std::unique_lock<std::mutex> lock(dynamic_bit_selection_mutex);
+            if (enable_dynamic_bit_selection_ == false)
+                {
+                    dynamic_bit_selection_active = false;
+                }
+            lock.unlock();
+        }
+}
 
 void Ad9361FpgaSignalSource::connect(gr::top_block_sptr top_block)
 {

src/algorithms/signal_source/adapters/ad9361_fpga_signal_source.h

@@ -22,6 +22,7 @@
 #define GNSS_SDR_AD9361_FPGA_SIGNAL_SOURCE_H
 
 #include "concurrent_queue.h"
+#include "fpga_dynamic_bit_selection.h"
 #include "fpga_switch.h"
 #include "gnss_block_interface.h"
 #include <pmt/pmt.h>
@@ -66,13 +67,20 @@ public:
     gr::basic_block_sptr get_right_block() override;
 
 private:
+    // perform dynamic bit selection every 500 ms by default
+    static const uint32_t Gain_control_period_ms = 500;
+
     void run_DMA_process(const std::string &FreqBand,
         const std::string &Filename1,
         const std::string &Filename2);
 
+    void run_dynamic_bit_selection_process(void);
+
     std::thread thread_file_to_dma;
+    std::thread thread_dynamic_bit_selection;
 
     std::shared_ptr<Fpga_Switch> switch_fpga;
+    std::shared_ptr<Fpga_dynamic_bit_selection> dynamic_bit_selection_fpga;
 
     std::string role_;
 
@@ -115,9 +123,11 @@ private:
     bool rx1_enable_;
     bool rx2_enable_;
     bool enable_DMA_;
+    bool enable_dynamic_bit_selection_;
     bool rf_shutdown_;
 
     std::mutex dma_mutex;
+    std::mutex dynamic_bit_selection_mutex;
 };
 
 #endif  // GNSS_SDR_AD9361_FPGA_SIGNAL_SOURCE_H

src/algorithms/signal_source/libs/CMakeLists.txt

@@ -17,6 +17,8 @@ endif()
 if(ENABLE_FPGA OR ENABLE_AD9361)
     set(OPT_SIGNAL_SOURCE_LIB_SOURCES ${OPT_SIGNAL_SOURCE_LIB_SOURCES} fpga_switch.cc)
     set(OPT_SIGNAL_SOURCE_LIB_HEADERS ${OPT_SIGNAL_SOURCE_LIB_HEADERS} fpga_switch.h)
+    set(OPT_SIGNAL_SOURCE_LIB_SOURCES ${OPT_SIGNAL_SOURCE_LIB_SOURCES} fpga_dynamic_bit_selection.cc)
+    set(OPT_SIGNAL_SOURCE_LIB_HEADERS ${OPT_SIGNAL_SOURCE_LIB_HEADERS} fpga_dynamic_bit_selection.h)
 endif()
 
 set(SIGNAL_SOURCE_LIB_SOURCES

src/algorithms/signal_source/libs/fpga_dynamic_bit_selection.cc

@@ -0,0 +1,136 @@
+/*!
+ * \file fpga_dynamic_bit_selection.cc
+ * \brief Dynamic Bit Selection in the received signal.
+ * \authors <ul>
+ *    <li> Marc Majoral, 2020. mmajoral(at)cttc.es
+ * </ul>
+ *
+ * Class that controls the Dynamic Bit Selection in the FPGA.
+ *
+ *
+ * -------------------------------------------------------------------------
+ *
+ * Copyright (C) 2010-2020  (see AUTHORS file for a list of contributors)
+ *
+ * GNSS-SDR is a software defined Global Navigation
+ *          Satellite Systems receiver
+ *
+ * This file is part of GNSS-SDR.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ * -------------------------------------------------------------------------
+ */
+
+#include "fpga_dynamic_bit_selection.h"
+#include <glog/logging.h>
+#include <fcntl.h>     // for open, O_RDWR, O_SYNC
+#include <iostream>    // for cout, endl
+#include <sys/mman.h>  // for mmap
+
+Fpga_dynamic_bit_selection::Fpga_dynamic_bit_selection(const std::string &device_name1, const std::string &device_name2)
+{
+    // dynamic bits selection corresponding to frequency band 1
+    if ((d_device_descriptor1 = open(device_name1.c_str(), O_RDWR | O_SYNC)) == -1)
+        {
+            LOG(WARNING) << "Cannot open deviceio" << device_name1;
+        }
+    d_map_base1 = reinterpret_cast<volatile unsigned *>(mmap(nullptr, FPGA_PAGE_SIZE,
+        PROT_READ | PROT_WRITE, MAP_SHARED, d_device_descriptor1, 0));
+
+    if (d_map_base1 == reinterpret_cast<void *>(-1))
+        {
+            LOG(WARNING) << "Cannot map the FPGA dynamic bit selection module in frequency band 1 into tracking memory";
+            std::cout << "Could not map dynamic bit selection memory corresponding to frequency band 1." << std::endl;
+        }
+
+    // dynamic bits selection corresponding to frequency band 2
+    if ((d_device_descriptor2 = open(device_name2.c_str(), O_RDWR | O_SYNC)) == -1)
+        {
+            LOG(WARNING) << "Cannot open deviceio" << device_name2;
+        }
+    d_map_base2 = reinterpret_cast<volatile unsigned *>(mmap(nullptr, FPGA_PAGE_SIZE,
+        PROT_READ | PROT_WRITE, MAP_SHARED, d_device_descriptor2, 0));
+
+    if (d_map_base2 == reinterpret_cast<void *>(-1))
+        {
+            LOG(WARNING) << "Cannot map the FPGA dynamic bit selection module in frequency band 2 into tracking memory";
+            std::cout << "Could not map dynamic bit selection memory corresponding to frequency band 2." << std::endl;
+        }
+
+    // initialize default bit selection
+    shift_out_bits_band1 = shift_out_bits_default;
+    shift_out_bits_band2 = shift_out_bits_default;
+
+    DLOG(INFO) << "Dynamic bit selection FPGA class created";
+}
+
+
+Fpga_dynamic_bit_selection::~Fpga_dynamic_bit_selection()
+{
+    close_devices();
+}
+
+void Fpga_dynamic_bit_selection::bit_selection(void)
+{
+    // estimated signal power corresponding to frequency band 1
+    uint32_t rx_signal_power1 = d_map_base1[1];
+    // estimated signal power corresponding to frequency band 2
+    uint32_t rx_signal_power2 = d_map_base2[1];
+
+    // dynamic bit selection corresponding to frequency band 1
+    if (rx_signal_power1 > Power_Threshold_High)
+        {
+            if (shift_out_bits_band1 < shift_out_bit_max)
+                {
+                    shift_out_bits_band1 = shift_out_bits_band1 + 1;
+                }
+        }
+    else if (rx_signal_power1 < Power_Threshold_Low)
+        {
+            if (shift_out_bits_band1 > shift_out_bits_min)
+                {
+                    shift_out_bits_band1 = shift_out_bits_band1 - 1;
+                }
+        }
+
+    // dynamic bit selection corresponding to frequency band 2
+    if (rx_signal_power2 > Power_Threshold_High)
+        {
+            if (shift_out_bits_band2 < shift_out_bit_max)
+                {
+                    shift_out_bits_band2 = shift_out_bits_band2 + 1;
+                }
+        }
+    else if (rx_signal_power2 < Power_Threshold_Low)
+        {
+            if (shift_out_bits_band2 > shift_out_bits_min)
+                {
+                    shift_out_bits_band2 = shift_out_bits_band2 - 1;
+                }
+        }
+
+    // update bit selection corresopnding to frequency band 1
+    d_map_base1[0] = shift_out_bits_band1;
+
+    // udpate bit selection corresponding to frequency band 2
+    d_map_base2[0] = shift_out_bits_band2;
+}
+
+void Fpga_dynamic_bit_selection::close_devices()
+{
+    auto *aux = const_cast<unsigned *>(d_map_base1);
+    if (munmap(static_cast<void *>(aux), FPGA_PAGE_SIZE) == -1)
+        {
+            std::cout << "Failed to unmap memory uio" << std::endl;
+        }
+
+    aux = const_cast<unsigned *>(d_map_base2);
+    if (munmap(static_cast<void *>(aux), FPGA_PAGE_SIZE) == -1)
+        {
+            std::cout << "Failed to unmap memory uio" << std::endl;
+        }
+
+    close(d_device_descriptor1);
+    close(d_device_descriptor2);
+}

src/algorithms/signal_source/libs/fpga_dynamic_bit_selection.h

@@ -0,0 +1,80 @@
+/*!
+ * \file fpga_dynamic_bit_selection.h
+ * \brief Dynamic bit selection in the received signal.
+ * \authors <ul>
+ *          <li> Marc Majoral, 2020. mmajoral(at)cttc.es
+ *          </ul>
+ *
+ * Class that controls the Dynamic Bit Selection in the FPGA.
+ *
+ *
+ * -------------------------------------------------------------------------
+ *
+ * Copyright (C) 2010-2020  (see AUTHORS file for a list of contributors)
+ *
+ * GNSS-SDR is a software defined Global Navigation
+ *          Satellite Systems receiver
+ *
+ * This file is part of GNSS-SDR.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ * -------------------------------------------------------------------------
+ */
+
+#ifndef GNSS_SDR_FPGA_DYNAMIC_BIT_SELECTION_H
+#define GNSS_SDR_FPGA_DYNAMIC_BIT_SELECTION_H
+
+#include <string>
+
+/*!
+ * \brief Class that controls the switch in the FPGA, which connects the FPGA acquisition and multicorrelator modules to
+ * either the DMA or the Analog Front-End.
+ */
+class Fpga_dynamic_bit_selection
+{
+public:
+    /*!
+     * \brief Constructor
+     */
+    explicit Fpga_dynamic_bit_selection(const std::string& device_name1, const std::string& device_name2);
+
+    /*!
+     * \brief Destructor
+     */
+    ~Fpga_dynamic_bit_selection();
+
+    /*!
+     * \brief This function configures the switch in th eFPGA
+     */
+    //    void set_switch_position(int32_t switch_position);
+    void bit_selection(void);
+
+private:
+    static const size_t FPGA_PAGE_SIZE = 0x10000;
+
+    static const uint32_t Num_bits_ADC = 12;                                      // Number of bits in the ADC
+    static const uint32_t Num_bits_FPGA = 4;                                      // Number of bits after the bit selection
+    static const uint32_t shift_out_bits_default = Num_bits_ADC - Num_bits_FPGA;  // take the most significant bits by default
+    static const uint32_t shift_out_bits_min = 0;                                 // minimum possible value for the bit selection
+    static const uint32_t shift_out_bit_max = Num_bits_ADC - Num_bits_FPGA;       // maximum possible value for the bit selection
+    // received signal power thresholds for the bit selection
+    // the received signal power is estimated as the averaged squared absolute value of the received signal samples
+    static const uint32_t Power_Threshold_High = 15000;
+    static const uint32_t Power_Threshold_Low = 6000;
+
+
+    void close_devices(void);
+
+    uint32_t shift_out_bits_band1;  // number of bits to shift for frequency band 1
+    uint32_t shift_out_bits_band2;  // number of bits to shift for frequency band 2
+
+
+    volatile unsigned* d_map_base1;  // driver memory map corresponding to frequency band 1
+    int d_device_descriptor1;        // driver descriptor corresponding to frequency band 1
+
+    volatile unsigned* d_map_base2;  // driver memory map corresponding to frequency band 2
+    int d_device_descriptor2;        // driver descriptor corresponding to frequency band 2
+};
+
+#endif  // GNSS_SDR_FPGA_DYNAMIC_BIT_SELECTION_H