Avoid tracking the same PRN in multiple channels (Fixes: #885)

docs/CHANGELOG.md

@@ -14,6 +14,11 @@ All notable changes to GNSS-SDR will be documented in this file.
 
 ## [Unreleased](https://github.com/gnss-sdr/gnss-sdr/tree/next)
 
+### Improvements in Interoperability:
+
+- Enabled multi-band processing off-loading to the FPGA when using the MAX2771
+  RF front-end.
+
 ### Improvements in Maintainability:
 
 - Added a CI job to detect lines longer than 512 characters (avoid this
@@ -27,7 +32,7 @@ All notable changes to GNSS-SDR will be documented in this file.
 
 ### Improvements in Portability:
 
-- Fix building option `-DENABLE_ION=ON` when using CMake >= 4.0.
+- Fixed building option `-DENABLE_ION=ON` when using CMake >= 4.0.
 - Updated `gsl-lite` to v1.0.1. See the
   [gsl-lite release](https://github.com/gsl-lite/gsl-lite/releases/tag/v1.0.1).
 
@@ -38,6 +43,9 @@ All notable changes to GNSS-SDR will be documented in this file.
   PDF format. It requires `numpy` and `matplotlib`.
 - `File_Signal_Source` fixed file length and sample skip calculations on 32-bit
   systems.
+- Fixed tracking the same PRN in multiple channels. Previously, this could
+  happen when the number of acquisition channels was close to the number of
+  available PRNs for a given signal.
 
 See the definitions of concepts and metrics at
 https://gnss-sdr.org/design-forces/

src/core/receiver/gnss_flowgraph.cc

@@ -2192,6 +2192,14 @@ Gnss_Signal GNSSFlowgraph::search_next_signal(const std::string& searched_signal
     std::string assist_signal = "";
     auto& available_signals = available_signals_map_.at(searched_signal);
 
+    if (available_signals.empty())
+        {
+            const auto& entry = signal_mapping.at(searched_signal);
+            const auto& gnss_system_str = entry.first;
+            const auto& signal_pretty_str = entry.second;
+            throw std::runtime_error("More ACQUISITION channels than PRNs for signal " + gnss_system_str + " " + signal_pretty_str);
+        }
+
     switch (mapStringValues_[searched_signal])
         {
         case evGPS_2S:
@@ -2250,8 +2258,12 @@ Gnss_Signal GNSSFlowgraph::search_next_signal(const std::string& searched_signal
         {
             result = available_signals.front();
             available_signals.pop_front();
+            const std::string sys = result.get_satellite().get_system();
+            if ((sys == "Glonass") || (sys == "Beidou"))
+                {
                     available_signals.push_back(result);
                 }
+        }
 
     return result;
 }

src/core/system_parameters/gnss_satellite.h

@@ -54,7 +54,7 @@ public:
     void update_PRN(uint32_t PRN);                                      //!< Updates the PRN Number when information is decoded, only applies to GLONASS GNAV messages
     uint32_t get_PRN() const;                                           //!< Gets satellite's PRN
     int32_t get_rf_link() const;                                        //!< Gets the satellite's rf link
-    std::string get_system() const;                                     //!< Gets the satellite system {"GPS", "GLONASS", "SBAS", "Galileo", "Beidou"}
+    std::string get_system() const;                                     //!< Gets the satellite system {"GPS", "Glonass", "SBAS", "Galileo", "Beidou"}
     std::string get_system_short() const;                               //!< Gets the satellite system {"G", "R", "SBAS", "E", "C"}
     std::string get_block() const;                                      //!< Gets the satellite block. If GPS, returns {"IIA", "IIR", "IIR-M", "IIF"}
     std::string what_block(const std::string& system_, uint32_t PRN_);  //!< Gets the block of a given satellite