main_receiver.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <time.h>

// 引入所有模块
#include "common.h"
#include "css_common.h"
#include "source_codec.h"
#include "tbcc_channel.h"
#include "css_modulator.h"
#include "css_demodulator.h"
#include "interleaver.h"

// === 新增头文件 ===
#include "css_doppler.h" 

// ==========================================
// 工具函数：保存数据到文件
// ==========================================
void save_debug_data(const char *filename, const float *data, size_t len) {
    FILE *fp = fopen(filename, "w");
    if (!fp) {
        printf("[Error] Could not open file %s for writing\n", filename);
        return;
    }
    for (size_t i = 0; i < len; i++) {
        fprintf(fp, "%f\n", data[i]);
    }
    fclose(fp);
    printf("[File] Saved %zu samples to '%s'\n", len, filename);
}

void print_preview_int(const char *label, const int *data, int len) {
    printf("   > %-30s: ", label);
    for (int i = 0; i < len; i++) printf("%d", data[i]);
    printf("...\n");
}

void print_preview_float(const char *label, const float *data, int len) {
    printf("   > %-30s: ", label);
    for (int i = 0; i < len; i++) printf("%+.1f ", data[i]);
    printf("...\n");
}

// ==========================================
// 信道模拟：高斯白噪声
// ==========================================
void add_awgn(float *signal, size_t len, float snr_db) {
    float sig_energy = 0;
    for(size_t i=0; i<len; i++) sig_energy += signal[i]*signal[i];
    float sig_power = sig_energy / len;
    float noise_power = sig_power / pow(10.0, snr_db/10.0);
    float noise_std = sqrt(noise_power);
    
    printf("\n[Channel] Adding AWGN (SNR: %.1f dB)...\n", snr_db);
    for (size_t i = 0; i < len; i++) {
        float u1 = (float)rand() / RAND_MAX;
        float u2 = (float)rand() / RAND_MAX;
        if(u1 < 1e-6) u1 = 1e-6;
        float z = sqrt(-2.0 * log(u1)) * cos(2.0 * PI * u2);
        signal[i] += noise_std * z;
    }
}

// ==========================================
// 主函数
// ==========================================
int main() {
    srand(time(NULL));
    printf("============================================\n");
    printf("      CSS Full Chain Receiver Simulation    \n");
    printf("============================================\n");

    // 1. 初始化
    tbcc_init();
    ModConfig mod_cfg = {
        .fs = 192000.0, .bw_total_low = 9000.0, .bw_total_high = 15000.0,
        .subband_bw = 300.0, .subband_guard = 80.0, .num_subbands = 16,
        .t_hfm_sync = 0.050, .t_lfm_pilot = 0.050, .t_guard_long = 0.020,
        .t_sym_active = 0.020, .t_sym_guard = 0.020
    };
    WaveformBank *bank = mod_init_waveform_bank(&mod_cfg);

    // 2. 发送端处理
    printf("\n[Tx] Generating Transmission Signal...\n");
    
    AppData tx_data = { .longitude = 120.013, .latitude = 30.4560, .depth = 50.0, .timestamp_us = 1234564578 };
    int frame_bits[FRAME_LEN_BITS];
    build_tx_frame(&tx_data, frame_bits);
    
    int encoded_bits[TBCC_ENC_LEN];
    tbcc_encode(frame_bits, encoded_bits);
    
    int interleaved_bits[TBCC_ENC_LEN];
    block_interleave(encoded_bits, interleaved_bits);
    
    uint8_t packed_payload[32];
    memset(packed_payload, 0, 32);
    for(int i=0; i<TBCC_ENC_LEN; i++) {
        if(interleaved_bits[i]) packed_payload[i/8] |= (1 << (7-(i%8)));
    }

    float *tx_signal = NULL;
    size_t tx_len = 0;
    mod_assemble_full_frame(packed_payload, bank, &mod_cfg, &tx_signal, &tx_len);
    save_debug_data("data_tx_clean.txt", tx_signal, tx_len);

    // ------------------------------------------------
    // 3. 信道传输 (模拟多普勒 + 噪声)
    // ------------------------------------------------
    
    // === 设置模拟参数 ===
    float sim_velocity = 1.0f; // 相对速度 15 m/s
    float c = 1500.0f;
    // 使用双向/回波模型公式，或者单纯为了加大难度测试算法
    float alpha_true = (c + sim_velocity) / (c - sim_velocity); 
    
    printf("\n[Channel] Simulating Doppler (v=%.2f m/s, alpha=%.6f)...\n", sim_velocity, alpha_true);

    // 计算接收长度 (物理压缩/拉伸)
    size_t rx_len_raw = (size_t)floor(tx_len / alpha_true);
    float *rx_signal_raw = (float*)malloc(rx_len_raw * sizeof(float));
    
    // (A) 多普勒效应: 重采样 (Tx -> Rx)
    // 注意：resample_linear 中 rate=alpha 表示 input 被抽取 (压缩)
    resample_linear(tx_signal, tx_len, alpha_true, rx_signal_raw, rx_len_raw);
    
    // (B) 加噪声
    add_awgn(rx_signal_raw, rx_len_raw, 20.0f); // 稍微提高一点 SNR 方便调试多普勒
    save_debug_data("data_rx_doppler_noisy.txt", rx_signal_raw, rx_len_raw);

    // ------------------------------------------------
    // 4. 接收端处理
    // ------------------------------------------------
    printf("\n[Rx] Starting Receiver Processing...\n");

    // === (A) 多普勒估计与补偿 ===
    printf("   > Performing Doppler Estimation & Compensation...\n");
    DopplerResult dop_res = css_doppler_process(rx_signal_raw, rx_len_raw, &mod_cfg, bank);
    
    if (dop_res.comp_signal == NULL) {
        printf("[Error] Doppler compensation failed!\n");
        return -1;
    }
    save_debug_data("data_rx_compensated.txt", dop_res.comp_signal, dop_res.comp_len);

    // === (B) CSS 解调 (使用补偿后的信号) ===
    float rx_soft_interleaved[TBCC_ENC_LEN];
    // 注意：将补偿后的信号传入解调器
    demod_process_full_frame(dop_res.comp_signal, dop_res.comp_len, &mod_cfg, bank, rx_soft_interleaved);

    // === (C) 后续链路 (解交织 -> 译码) ===
    float rx_soft_ordered[TBCC_ENC_LEN];
    block_deinterleave_soft(rx_soft_interleaved, rx_soft_ordered);
    
    int rx_decoded_bits[FRAME_LEN_BITS];
    tbcc_decode(rx_soft_ordered, rx_decoded_bits);

    // ------------------------------------------------
    // 5. 结果分析
    // ------------------------------------------------
    printf("\n[Analysis] Performance Metrics:\n");
    
    int error_count = 0;
    for (int i = 0; i < FRAME_LEN_BITS; i++) {
        if (frame_bits[i] != rx_decoded_bits[i]) error_count++;
    }
    printf("   > BER: %.4f%% (%d errors)\n", (float)error_count/FRAME_LEN_BITS*100.0f, error_count);

    AppData rx_data;
    if (parse_rx_frame(rx_decoded_bits, &rx_data)) {
        printf("[Result] CRC PASS. Data Recovered.\n");
        printf("   > Depth: %.1fm (Tx: %.1fm)\n", rx_data.depth, tx_data.depth);
    } else {
        printf("[Result] CRC FAILED.\n");
    }

    // 清理
    free(tx_signal);
    free(rx_signal_raw);
    free(dop_res.comp_signal); // 记得释放补偿后的信号
    mod_free_waveform_bank(bank, mod_cfg.num_subbands);

    printf("\n=== Simulation Finished ===\n");
    return 0;
}