ldpc 加权比特译码算法c语言

以下是LDPC加权比特译码算法的C语言代码：

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

#define MAX_ITER 50
#define EPS 1e-7

double* LLR; // 信道输入
double* LLRout; // 译码输出
double** H; // LDPC 矩阵
double** W; // 权重矩阵
int* rowsize; // 每行非零元素个数
int n; // 码字长度
int m; // 码字检验位数
int nC; // 变量节点数
int nV; // 校验节点数

int sign(double x) {
    return (x >= 0) ? 1 : -1;
}

void ldpc_encoder(double* u, double* v) {
    int i, j;
    for (i = 0; i < m; i++) {
        v[i] = 0;
        for (j = 0; j < rowsize[i]; j++) {
            v[i] += u[H[i][j]] * W[i][j];
        }
        v[i] = tanh(v[i]);
    }
}

void ldpc_decoder() {
    int iter, i, j, k;
    double **vnode, **cnode, **Q, **R;
    double *vnode_sum, *cnode_sum;
    double **vnode_msg, **cnode_msg;
    double **cnode_prev;

    vnode = (double**) malloc(nV * sizeof(double*));
    for (i = 0; i < nV; i++) {
        vnode[i] = (double*) malloc(2 * nC * sizeof(double));
    }

    cnode = (double**) malloc(nC * sizeof(double*));
    for (i = 0; i < nC; i++) {
        cnode[i] = (double*) malloc(2 * rowsize[i] * sizeof(double));
    }

    Q = (double**) malloc(nC * sizeof(double*));
    for (i = 0; i < nC; i++) {
        Q[i] = (double*) malloc(rowsize[i] * sizeof(double));
    }

    R = (double**) malloc(nC * sizeof(double*));
    for (i = 0; i < nC; i++) {
        R[i] = (double*) malloc(rowsize[i] * sizeof(double));
    }

    vnode_sum = (double*) malloc(nC * sizeof(double));
    cnode_sum = (double*) malloc(nV * sizeof(double));

    vnode_msg = (double**) malloc(nV * sizeof(double*));
    for (i = 0; i < nV; i++) {
        vnode_msg[i] = (double*) malloc(rowsize[i] * sizeof(double));
    }

    cnode_msg = (double**) malloc(nC * sizeof(double*));
    for (i = 0; i < nC; i++) {
        cnode_msg[i] = (double*) malloc(2 * rowsize[i] * sizeof(double));
    }

    cnode_prev = (double**) malloc(nC * sizeof(double*));
    for (i = 0; i < nC; i++) {
        cnode_prev[i] = (double*) malloc(rowsize[i] * sizeof(double));
    }

    // 初始化变量节点信息
    for (i = 0; i < nV; i++) {
        for (j = 0; j < rowsize[i]; j++) {
            vnode_msg[i][j] = LLR[i];
        }
    }

    // 迭代译码
    for (iter = 0; iter < MAX_ITER; iter++) {
        // 变量节点更新
        for (i = 0; i < nV; i++) {
            for (j = 0; j < rowsize[i]; j++) {
                double product = 1;
                for (k = 0; k < rowsize[i]; k++) {
                    if (j != k) {
                        product *= tanh(0.5 * vnode[i][2 * k + 1]);
                    }
                }
                vnode_msg[i][j] = 2 * atanh(product);
            }
        }

        // 校验节点更新
        for (i = 0; i < nC; i++) {
            for (j = 0; j < rowsize[i]; j++) {
                int k = H[i][j];
                double product = 1;
                for (int l = 0; l < rowsize[i]; l++) {
                    if (j != l) {
                        product *= tanh(0.5 * cnode_prev[i][l]);
                    }
                }
                Q[i][j] = product;
                R[i][j] = tanh(0.5 * vnode[k][2 * j]);
                cnode_msg[i][2 * j] = atanh(Q[i][j] * R[i][j]);
                cnode_msg[i][2 * j + 1] = LLR[k];
            }
        }

        // 校验节点求和
        for (i = 0; i < nC; i++) {
            vnode_sum[i] = 0;
            for (j = 0; j < rowsize[i]; j++) {
                vnode_sum[i] += cnode_msg[i][2 * j];
            }
        }

        // 变量节点求和
        for (i = 0; i < nV; i++) {
            cnode_sum[i] = 0;
            for (j = 0; j < rowsize[i]; j++) {
                cnode_sum[i] += cnode_msg[H[i][j]][2 * j + 1];
            }
        }

        // 更新变量节点
        for (i = 0; i < nV; i++) {
            for (j = 0; j < rowsize[i]; j++) {
                double sum = cnode_sum[i] - cnode_msg[H[i][j]][2 * j + 1];
                vnode[i][2 * j + 1] = sum + vnode_msg[i][j];
                vnode[i][2 * j] = 2 * atanh(tanh(0.5 * sum) * tanh(0.5 * vnode_msg[i][j]));
            }
        }

        // 更新校验节点
        for (i = 0; i < nC; i++) {
            for (j = 0; j < rowsize[i]; j++) {
                cnode_prev[i][j] = cnode_msg[i][2 * j] - vnode_sum[i];
            }
        }

        // 判断停止条件
        int stop = 1;
        for (i = 0; i < nV; i++) {
            if (fabs(LLR[i] - vnode[i][1]) > EPS) {
                stop = 0;
                break;
            }
        }
        if (stop) {
            break;
        }
    }

    // 译码输出
    for (i = 0; i < n; i++) {
        LLRout[i] = vnode[i][1];
    }

    // 释放内存
    for (i = 0; i < nV; i++) {
        free(vnode[i]);
    }
    free(vnode);

    for (i = 0; i < nC; i++) {
        free(cnode[i]);
        free(Q[i]);
        free(R[i]);
        free(cnode_prev[i]);
    }
    free(cnode);
    free(Q);
    free(R);
    free(cnode_prev);

    free(vnode_sum);
    free(cnode_sum);

    for (i = 0; i < nV; i++) {
        free(vnode_msg[i]);
    }
    free(vnode_msg);

    for (i = 0; i < nC; i++) {
        free(cnode_msg[i]);
    }
    free(cnode_msg);
}

int main() {
    // 初始化 LDPC 码
    n = 6; // 码字长度
    m = 3; // 码字检验位数
    nC = m; // 变量节点数
    nV = n - m; // 校验节点数

    LLR = (double*) malloc(n * sizeof(double));
    LLRout = (double*) malloc(n * sizeof(double));
    H = (double**) malloc(m * sizeof(double*));
    W = (double**) malloc(m * sizeof(double*));
    rowsize = (int*) malloc(m * sizeof(int));

    H[0] = (double[]) {0, 2, 3};
    H[1] = (double[]) {1, 2, 4};
    H[2] = (double[]) {3, 4, 5};

    W[0] = (double[]) {1.0, 2.0, 3.0};
    W[1] = (double[]) {4.0, 5.0, 6.0};
    W[2] = (double[]) {7.0, 8.0, 9.0};

    rowsize[0] = 3;
    rowsize[1] = 3;
    rowsize[2] = 3;

    // 初始化信道输入
    LLR[0] = 0.2;
    LLR[1] = -0.3;
    LLR[2] = 0.4;
    LLR[3] = -0.5;
    LLR[4] = 0.6;
    LLR[5] = -0.7;

    // LDPC 解码
    ldpc_decoder();

    // 输出译码结果
    int i;
    for (i = 0; i < n; i++) {
        printf("%f ", LLRout[i]);
    }
    printf("\n");

    // 释放内存
    free(LLR);
    free(LLRout);
    free(rowsize);
    free(H);
    free(W);
    return 0;
}

注意，这段代码只是一个简单的示例，实际应用中可能需要根据具体情况进行修改。此外，代码中使用了 `tanh` 和 `atanh` 函数，需要包含 `<math.h>` 头文件。