It's starting to sound right

include/encoder/ModemController.h

@@ -51,7 +51,7 @@ public:
           interleaver(baud_rate, interleave_setting, is_frequency_hopping),
           input_data(std::move(_data)),
           mgd_decoder(baud_rate, is_frequency_hopping),
-          modulator(48000) {}
+          modulator(baud_rate, 48000, 0.5, is_frequency_hopping) {}
 
     /**
      * @brief Transmits the input data by processing it through different phases like FEC encoding, interleaving, symbol formation, scrambling, and modulation.
@@ -75,19 +75,12 @@ public:
 
         std::vector<uint8_t> mgd_decoded_data = mgd_decoder.mgdDecode(processed_data);
 
-        // Step 4: Symbol Formation. This function injects the sync preamble symbols.
+        // Step 4: Symbol Formation. This function injects the sync preamble symbols. Scrambling is built-in.
         std::vector<uint8_t> symbol_stream = symbol_formation.formSymbols(mgd_decoded_data);
 
-        // Step 5: Scrambling
+        std::vector<int16_t> modulated_signal = modulator.modulate(symbol_stream);
-        std::vector<uint8_t> scrambled_data = scrambler.scrambleData(symbol_stream);
 
-        // Step 6: PSK Modulation. This is the final baseband output of the class.
+        return modulated_signal;
-        std::vector<int16_t> modulated_signal = modulator.modulate(scrambled_data);
-
-        // Step 7: Apply Sqrt Half Cosine Filter with a rolloff factor of 0.3 (30%)
-        std::vector<int16_t> filtered_signal = SqrtHalfCosine(modulated_signal, 0.3);
-
-        return filtered_signal;
     }
 
 private:
@@ -96,6 +89,7 @@ private:
     bool is_frequency_hopping;       ///< Indicates if frequency hopping is used.
     BitStream input_data;            ///< The input data stream.
     size_t interleave_setting;       ///< The interleave setting to be used.
+    size_t sample_rate;
 
     SymbolFormation symbol_formation; ///< Symbol formation instance to form symbols from data.
     Scrambler scrambler;              ///< Scrambler instance for scrambling the data.
@@ -132,28 +126,6 @@ private:
         return eom_data;
     }
 
-    /**
-     * @brief Applies a square-root raised cosine filter to the input signal.
-     * @param input_signal The input modulated signal.
-     * @param rolloff_factor The rolloff factor of the filter.
-     * @return The filtered signal.
-     */
-    [[nodiscard]] std::vector<int16_t> SqrtHalfCosine(const std::vector<int16_t>& input_signal, double rolloff_factor) const {
-        std::vector<int16_t> filtered_signal(input_signal.size());
-        const double pi = M_PI;
-        const double normalization_factor = 1.0 / (1.0 + rolloff_factor);
-
-        for (size_t i = 0; i < input_signal.size(); ++i) {
-            double t = static_cast<double>(i) / input_signal.size();
-            double cosine_term = std::cos(pi * t * rolloff_factor);
-            double filtered_value = input_signal[i] * normalization_factor * (0.5 + 0.5 * cosine_term);
-
-            filtered_signal[i] = clamp(static_cast<int16_t>(filtered_value));
-        }
-
-        return filtered_signal;
-    }
-
     std::vector<uint8_t> splitTribitSymbols(const BitStream& input_data) {
         std::vector<uint8_t> return_vector;
         size_t max_index = input_data.getMaxBitIndex();

include/modulation/PSKModulator.h

@@ -5,52 +5,130 @@
 #include <cmath>
 #include <cstdint>
 #include <stdexcept>
+#include <complex>
+#include <algorithm>
 
 class PSKModulator {
 public:
-    PSKModulator(double sample_rate) : sample_rate(sample_rate), carrier_freq(1800), phase(0.0) {
+    PSKModulator(double baud_rate, double sample_rate, double energy_per_bit, bool is_frequency_hopping) 
+        : sample_rate(sample_rate), carrier_freq(1800), phase(0.0) {
         initializeSymbolMap();
+        symbol_rate = 2400;  // Fixed symbol rate as per specification (2400 symbols per second)
+        samples_per_symbol = static_cast<size_t>(sample_rate / symbol_rate);
     }
 
     std::vector<int16_t> modulate(const std::vector<uint8_t>& symbols) {
-        std::vector<int16_t> modulated_signal;
+        std::vector<std::complex<double>> modulated_signal;
 
         const double phase_increment = 2 * M_PI * carrier_freq / sample_rate;
         for (auto symbol : symbols) {
             if (symbol >= symbolMap.size()) {
                 throw std::out_of_range("Invalid symbol value for 8-PSK modulation");
             }
-            double target_phase = symbolMap[symbol];
+            std::complex<double> target_symbol = symbolMap[symbol];
 
             for (size_t i = 0; i < samples_per_symbol; ++i) {
-                double value = std::sin(phase + target_phase);
+                double in_phase = std::cos(phase + target_symbol.real());
-                modulated_signal.push_back(static_cast<int16_t>(value * std::numeric_limits<int16_t>::max()));
+                double quadrature = std::sin(phase + target_symbol.imag());
-                phase += phase_increment;
+                modulated_signal.emplace_back(in_phase, quadrature);
-                if (phase >= 2 * M_PI) {
+                phase = std::fmod(phase + phase_increment, 2 * M_PI);
-                    phase -= 2 * M_PI;
-                }
             }
         }
-        return modulated_signal;
+
+        // Apply raised-cosine filter
+        auto filter_taps = sqrtRaisedCosineFilter(201, symbol_rate);  // Adjusted number of filter taps to 201 for balance
+        auto filtered_signal = applyFilter(modulated_signal, filter_taps);
+
+        // Normalize the filtered signal
+        double max_value = 0.0;
+        for (const auto& sample : filtered_signal) {
+            max_value = std::max(max_value, std::abs(sample.real()));
+            max_value = std::max(max_value, std::abs(sample.imag()));
+        }
+        double gain = (max_value > 0) ? (32767.0 / max_value) : 1.0;
+
+        // Combine the I and Q components and apply gain for audio output
+        std::vector<int16_t> combined_signal;
+        for (auto& sample : filtered_signal) {
+            int16_t combined_sample = static_cast<int16_t>(std::clamp(gain * (sample.real() + sample.imag()), -32768.0, 32767.0));
+            combined_signal.push_back(combined_sample);
+        }
+
+        return combined_signal;
+    }
+
+    std::vector<double> sqrtRaisedCosineFilter(size_t num_taps, double symbol_rate) {
+        double rolloff = 0.35;  // Fixed rolloff factor as per specification
+        std::vector<double> filter_taps(num_taps);
+        double norm_factor = 0.0;
+        double sampling_interval = 1.0 / sample_rate;
+        double symbol_duration = 1.0 / symbol_rate;
+        double half_num_taps = static_cast<double>(num_taps - 1) / 2.0;
+
+        for (size_t i = 0; i < num_taps; ++i) {
+            double t = (i - half_num_taps) * sampling_interval;
+            if (std::abs(t) < 1e-10) {
+                filter_taps[i] = 1.0;
+            } else {
+                double numerator = std::sin(M_PI * t / symbol_duration * (1.0 - rolloff)) +
+                                  4.0 * rolloff * t / symbol_duration * std::cos(M_PI * t / symbol_duration * (1.0 + rolloff));
+                double denominator = M_PI * t * (1.0 - std::pow(4.0 * rolloff * t / symbol_duration, 2));
+                filter_taps[i] = numerator / denominator;
+            }
+            norm_factor += filter_taps[i] * filter_taps[i];
+        }
+
+        norm_factor = std::sqrt(norm_factor);
+        std::for_each(filter_taps.begin(), filter_taps.end(), [&norm_factor](double &tap) { tap /= norm_factor; });
+        return filter_taps;
+    }
+
+    std::vector<std::complex<double>> applyFilter(const std::vector<std::complex<double>>& signal, const std::vector<double>& filter_taps) {
+        std::vector<std::complex<double>> filtered_signal(signal.size());
+
+        size_t filter_length = filter_taps.size();
+        size_t half_filter_length = filter_length / 2;
+
+        // Convolve the signal with the filter taps
+        for (size_t i = 0; i < signal.size(); ++i) {
+            double filtered_i = 0.0;
+            double filtered_q = 0.0;
+
+            for (size_t j = 0; j < filter_length; ++j) {
+                if (i >= j) {
+                    filtered_i += filter_taps[j] * signal[i - j].real();
+                    filtered_q += filter_taps[j] * signal[i - j].imag();
+                } else {
+                    // Handle edge case by zero-padding
+                    filtered_i += filter_taps[j] * 0.0;
+                    filtered_q += filter_taps[j] * 0.0;
+                }
+            }
+
+            filtered_signal[i] = std::complex<double>(filtered_i, filtered_q);
+        }
+
+        return filtered_signal;
     }
 
 private:
     double sample_rate;        ///< The sample rate of the system.
     double carrier_freq;       ///< The frequency of the carrier, set to 1800 Hz as per standard.
     double phase;              ///< Current phase of the carrier waveform.
-    size_t samples_per_symbol = 40; ///< Number of samples per symbol, calculated to match symbol duration with cycle.
+    size_t samples_per_symbol; ///< Number of samples per symbol, calculated to match symbol duration with cycle.
-    std::vector<double> symbolMap;  ///< The mapping of tribit symbols to phase shifts.
+    size_t symbol_rate;
+    std::vector<std::complex<double>> symbolMap;  ///< The mapping of tribit symbols to I/Q components.
 
     void initializeSymbolMap() {
         symbolMap = {
-            0.0,          // 0 (000) corresponds to 0 degrees
+            {1.0, 0.0},                              // 0 (000) corresponds to I = 1.0, Q = 0.0
-            M_PI / 4,     // 1 (001) corresponds to 45 degrees
+            {std::sqrt(2.0) / 2.0, std::sqrt(2.0) / 2.0}, // 1 (001) corresponds to I = cos(45), Q = sin(45)
-            M_PI / 2,     // 2 (010) corresponds to 90 degrees
+            {0.0, 1.0},                              // 2 (010) corresponds to I = 0.0, Q = 1.0
-            3 * M_PI / 4, // 3 (011) corresponds to 135 degrees
+            {-std::sqrt(2.0) / 2.0, std::sqrt(2.0) / 2.0}, // 3 (011) corresponds to I = cos(135), Q = sin(135)
-            M_PI,         // 4 (100) corresponds to 180 degrees
+            {-1.0, 0.0},                             // 4 (100) corresponds to I = -1.0, Q = 0.0
-            5 * M_PI / 4, // 5 (101) corresponds to 225 degrees
+            {-std::sqrt(2.0) / 2.0, -std::sqrt(2.0) / 2.0}, // 5 (101) corresponds to I = cos(225), Q = sin(225)
-            3 * M_PI / 2, // 6 (110) corresponds to 270 degrees
+            {0.0, -1.0},                             // 6 (110) corresponds to I = 0.0, Q = -1.0
-            7 * M_PI / 4  // 7 (111) corresponds to 315 degrees
+            {std::sqrt(2.0) / 2.0, -std::sqrt(2.0) / 2.0}  // 7 (111) corresponds to I = cos(315), Q = sin(315)
         };
     }
 };