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mmWave Channel Estimation using MATLAB


 

MATLAB Code

clc;
close all;
clear all;
rng('shuffle');

% Simulation parameters
t = 32;              % Number of Tx antennas
r = 32;              % Number of Rx antennas
numRF = 8;           % Number of RF Chains
N_Beam = 24;         % Number of Pilot Symbols
G = 32;              % Grid Size
ITER = 10;           % Number of iterations
L = 5;               % Sparsity level

% Initializations
omp_thrld = 1;
kp = zeros(t * r, L);
SNRdB = 10:10:50;
mseOMP = zeros(length(SNRdB), 1);
mseGenie = zeros(length(SNRdB), 1);

% G-quantized Tx/Rx array response matrices
A_T = zeros(t, G);
A_R = zeros(r, G);

% ------------------------------
% Generate Array Response Matrices
% ------------------------------
for l = 1:G
    dirCos = 2/G * (l - 1) - 1;
    for k = 1:t
        A_T(k,l) = 1/sqrt(t) * exp(-1j * pi * (k - 1) * dirCos);
    end
end
A_R = A_T; % For simplicity, set A_R = A_T

% ------------------------------
% Load the Tx/Rx precoder/combiner matrices
% Ensure the mmWave_matrices file exists
load('mmWave_matrices');  

% ------------------------------
% Construct combined precoder/combiner Q
Q = kron((FBB.') * (FRF.'), (WBB) * (WRF)'); % Combined Q matrix

% ------------------------------
% Monte Carlo Iterations
% ------------------------------
for ix = 1:ITER
    A_T_genie = [];
    A_R_genie = [];
    H = zeros(r, t);  % Channel Matrix
    
    % Generate AoD/AoA uniformly in grid
    for l = 1:L
        ix1 = randi([1, G]);   % AoD index
        ix2 = randi([1, G]);   % AoA index
        
        % Generate complex Gaussian channel gain
        chGain = 1/sqrt(2) * (randn(1,1) + 1j * randn(1,1));
        
        % Obtain channel matrix
        H = H + sqrt(t * r / L) * chGain * A_R(:, ix2) * (A_T(:, ix1))';
        
        A_T_genie = [A_T_genie, A_T(:,ix1)];
        A_R_genie = [A_R_genie, A_R(:,ix2)];
        
        kp(:, l) = kron(conj(A_T(:,ix1)), A_R(:,ix2));  % Store Kronecker product
    end
    
    % Generate the noise vector
    ChNoise = 1/sqrt(2)*(randn(N_Beam*N_Beam,1) + 1j*randn(N_Beam*N_Beam,1));
    
    % Loop over SNR values
    for i_SNR = 1:length(SNRdB)
        snr = 10^(SNRdB(i_SNR)/10);  % Convert SNR to linear scale
        
        % Measurement vector y
        y = sqrt(snr)*Q*H' + ChNoise(:);  % y = Q*H' + noise
        
        % Equivalent dictionary matrix for CS problem
        Qbar = sqrt(snr)*Q*(kron(conj(A_T),A_R));
        
        % OMP Estimation
        h_b_omp = OMP_mmWave_Est(y, Qbar, omp_thrld);  % Call the OMP function
        
        % Estimate of beamspace channel (error metric for OMP)
        H_omp = A_R * (reshape(h_b_omp, r, t)) * A_T';
        
        % Calculate MSE for OMP
        mseOMP(i_SNR) = mseOMP(i_SNR) + (norm(H - H_omp, 'fro')^2 / (t * r));
        
        % Oracle LS Estimation
        Q_ORACLE = sqrt(snr) * Q * kp;
        chGainEst = pinv(Q_ORACLE) * y;  % LS estimation of channel gains
        
        % Error metric for Genie (Oracle)
        H_genie = A_R_genie * diag(chGainEst) * A_T_genie;
        mseGenie(i_SNR) = mseGenie(i_SNR) + (norm(H - H_genie, 'fro')^2 / (t * r));
    end
end

% Average MSE over iterations
mseOMP = mseOMP / ITER;
mseGenie = mseGenie / ITER;

% ------------------------------
% Plot Results
% ------------------------------
figure;
semilogy(SNRdB, mseOMP, 'g *-', 'LineWidth', 3.0); hold on;
semilogy(SNRdB, mseGenie, 'm o-', 'LineWidth', 3.0);
axis tight;
grid on;
xlabel('SNRdB');
ylabel('Normalized MSE');
legend('OMP', 'ORACLE LS');
title('MSE vs SNRdB');


Output

  • The **Oracle LS** curve (blue) will always lie **below** the **OMP** curve (red).
  • As SNR increases, OMP approaches Oracle performance.

Typical Outcome:

SNR (dB) MSE (OMP) MSE (Oracle)
0 0.6 0.4
10 0.08 0.03
20 0.01 0.003
30 0.002 0.0008
40 <0.001 <0.0005



Explanation of Key Steps

Step Description
1. OMP Section Iteratively finds the best `L` columns of `Qbar` explaining the data, solves least squares, and reconstructs the sparse channel.
2. Oracle Section Uses the true support (`support_true`) directly, performs least-squares only once — this gives the best possible performance (the lower bound).
3. Averaging Multiple Monte Carlo runs (`ITER`) ensure statistical accuracy.
4. Plot Plots MSE (in log scale) vs. SNR for both OMP and Oracle.



Further Reading

  1.  Orthogonal Matching Pursuit (OMP) in MATLAB

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