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MIMI检测-线性算法-匹配滤波 Matched Filter

2022-10-14 11:24 作者:乐吧的数学  | 我要投稿

这篇文章讲解一下 MIMO 检测算法的一个小类别:线性算法。

(录制的视频:

https://www.bilibili.com/video/BV1xe4y1E7GE/

https://www.bilibili.com/video/BV1vd4y117YQ/

我们的问题是已知接收的信号 Y,以及信道系数矩阵 H,估计发送的数据 X.



这里说的线性算法,指的是通过对 Y 的线性组合来估计出发送的数据 X,可以表示为:


%5Chat%20X%20%3D%20T%20Y


其中 Y 是接收到的信号构成的列向量,%5Chat%20X 是估计出来的发送数据构成的列向量,T 是一个矩阵,这样,估计出来的发送的数据,就是接收到的数据的线性组合,例如:


%5Chat%20x_1%20%3D%20t_%7B11%7Dy_1%2Bt_%7B12%7Dy_2%2B...%2Bt_%7B1N_r%7Dy_%7BN_r%7D%20%20%5C%5C%0A%0A...%20%5C%5C%0A%0A%5Chat%20x_k%20%3D%20t_%7Bk1%7Dy_1%2Bt_%7Bk2%7Dy_2%2B...%2Bt_%7BkN_r%7Dy_%7BN_r%7D%20%20%5C%5C%0A%0A...%5C%5C%0A%0A%5Chat%20x_%7BN_t%7D%20%3D%20t_%7Bk1%7Dy_1%2Bt_%7Bk2%7Dy_2%2B...%2Bt_%7BkN_r%7Dy_%7BN_r%7D


这篇文章介绍三种典型的 MIMO 的线性 detector(检测)。


匹配滤波器(MF: Matched Filter)


%5Chat%20X%20%3D%20H%5EH%20Y%20%20-------%E5%85%AC%E5%BC%8F(1)



因为:


y_1%20%3D%20h_%7B11%7Dx_1%20%2B%20h_%7B12%7D%20x_2%20%2B%20...%20%2B%20h_%7B1N_t%7D%20x_%7BN_t%7D%20%2B%20n_1%20%5C%5C%0A%0Ay_2%20%3D%20h_%7B21%7Dx_1%20%2B%20h_%7B22%7D%20x_2%20%2B%20...%20%2B%20h_%7B2N_t%7D%20x_%7BN_t%7D%20%2B%20n_2%20%5C%5C%0A%0A...%20%5C%5C%0A%0Ay_%7BN_r%7D%20%3D%20h_%7BN_r1%7Dx_1%20%2B%20h_%7BN_r2%7D%20x_2%20%2B%20...%20%2B%20h_%7BN_rN_t%7D%20x_%7BN_t%7D%20%2B%20n_%7BN_r%7D%20%5C%5C



而公式(1) 可以写成:


%5Chat%20x_1%20%3D%20h_%7B11%7D%5E*%20y_1%20%2B%20h_%7B21%7D%5E*%20y_2%20%2B%20...%20%2B%20h_%7BN_r%201%7D%5E*%20y_%7BN_r%7D%20%5C%5C%0A%0A%5Chat%20x_2%20%3D%20h_%7B12%7D%5E*%20y_1%20%2B%20h_%7B22%7D%5E*%20y_2%20%2B%20...%20%2B%20h_%7BN_r%202%7D%5E*%20y_%7BN_r%7D%20%5C%5C%0A%0A...%20%5C%5C%0A%0A%5Chat%20x_%7BN_t%7D%20%3D%20h_%7B12%7D%5E*%20y_1%20%2B%20h_%7B22%7D%5E*%20y_2%20%2B%20...%20%2B%20h_%7BN_r%202%7D%5E*%20y_%7BN_r%7D%20%5C%5C



我们把其中一个估计,展开看看:


%5Chat%20x_2%20%3D%20h_%7B12%7D%5E*%20y_1%20%2B%20h_%7B22%7D%5E*%20y_2%20%2B%20...%20%2B%20h_%7BN_r%202%7D%5E*%20y_%7BN_r%7D%20%5C%5C%20%0A%0A%3Dh_%7B12%7D%5E*h_%7B21%7Dx_1%20%2B%20h_%7B12%7D%5E*h_%7B12%7Dx_2%2B...%2Bh_%7B12%7D%5E*h_%7B1N_t%7Dx_%7BN_t%7D%20%2B%20%5C%5C%0A%0Ah_%7B22%7D%5E*h_%7B21%7Dx_1%20%2B%20h_%7B22%7D%5E*h_%7B22%7Dx_2%2B...%2Bh_%7B22%7D%5E*h_%7B2N_t%7Dx_%7BN_t%7D%20%2B%20%5C%5C%0A%0A...%20%2B%20%5C%5C%0A%0Ah_%7BN_r%202%7D%5E*h_%7BN_r%201%7Dx_1%20%2B%20h_%7BN_r%202%7D%5E*h_%7BN_r%202%7Dx_2%2B...%2Bh_%7BN_r%202%7D%5E*h_%7B%20N_r%20N_t%7Dx_%7BN_t%7D%20%5C%5C%0A%0A%3D%20(h_%7B12%7D%5E*h_%7B12%7D%2Bh_%7B22%7D%5E*h_%7B22%7D%2B...%2Bh_%7BN_r%202%7D%5E*h_%7BN_r%202%7D)%20x_2%20%2B%20.....



我们用向量的方式来表示,更简洁,容易理解:


令:


H%20%3D%20%5Bh_1%2Ch_2%2C...%2Ch_%7BN_t%7D%5D



则:


Y%20%3D%20h_1%20x_1%20%2B%20h_2%20x_2%20%2B%20...%2B%20h_%7BN_t%7D%20x_%7BN_t%7D%20%2B%20n



而:


H%5EH%20%3D%20%0A%0A%5Cbegin%7Bbmatrix%7D%0A%0Ah_1%5EH%20%5C%5C%0A%0Ah_2%5EH%20%5C%5C%0A%0A...%20%5C%5C%0A%0Ah_%7BN_t%7D%5EH%0A%0A%5Cend%7Bbmatrix%7D



从而:


%5Chat%20X%20%3D%20H%5EH%20Y%20%3D%20%0A%0A%5Cbegin%7Bbmatrix%7D%0A%0Ah_1%5EH%20h_1%20x_1%20%2B%20h_1%5EH%20h_2%20x_2%2B...%2Bh_1%5EH%20h_%7BN_t%7D%20x_%7BN_t%7D%20%2B%20h_1%5EHn%20%5C%5C%0A%0Ah_2%5EH%20h_1%20x_1%20%2B%20h_2%5EH%20h_2%20x_2%2B...%2Bh_2%5EH%20h_%7BN_t%7D%20x_%7BN_t%7D%20%2B%20h_2%5EHn%5C%5C%0A%0A...%5C%5C%0A%0Ah_%7BN_t%7D%5EH%20h_1%20x_1%20%2B%20h_%7BN_t%7D%5EH%20h_2%20x_2%2B...%2Bh_%7BN_t%7D%5EH%20h_%7BN_t%7D%20x_%7BN_t%7D%20%2B%20h_%7BN_t%7D%5EHn%20%0A%0A%5Cend%7Bbmatrix%7D



例如:


%5Chat%20x_2%20%3Dh_2%5EH%20h_1%20x_1%20%2B%20h_2%5EH%20h_2%20x_2%2B...%2Bh_2%5EH%20h_%7BN_t%7D%20x_%7BN_t%7D%20%2B%20h_2%5EHn%5C%5C%0A%0A%3D%20h_2%5EH%20h_2%20x_2%20%2B%20h_2%5EH%20h_1%20x_1%20%2B%20h_3%5EH%20h_3%20x_3%2B...%2Bh_2%5EH%20h_%7BN_t%7D%20x_%7BN_t%7D%2B%20h_2%5EHn


除了第一项,后面都是干扰项。


如果满足正交性,则干扰就会都消失掉。



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