function [len_CP] = Generate_CP(channel_response,N_windows,N_level,min_len_CP)
% 产生CP长度的函数
% 在该方法中，假设将要发送的OFDM符号的数量等于H_bs中窗的数目。
% 输入channel_response 信道响应；N_windows 需要划窗的个数；N_level 量化等级；
%   min_len_CP，最小CP取决于最大延迟拓展，有最小CP值>最大延迟拓展
% 输出CP的长度向量，其长度等于窗的个数

% 子载波个数
N_carriers = length(channel_response);
% 窗的长度
Len_windows = N_carriers / N_windows;

% 对信道增益进行降序排序并记录索引
[channel_gain, sorted_indices] = sort(abs(channel_response), 'descend');% 
G_max = max(channel_gain);
G_min = min(channel_gain);

% 距离水平
D_L = (G_max-G_min)/N_level;

% 计算每个子载波对应的等级
level_k = zeros(1,N_carriers);
for i = 1:N_carriers
    % 边界值处理
    if channel_gain(i) <= G_min
        level_k(i) = 1;
    elseif channel_gain(i) >= G_max
        level_k(i) = N_level;
    % 根据式(3)的变形，可以得到权重等级
    else
    level_k(i) = ceil((channel_gain(i) - G_min)/D_L);
    end
end

% 根据式(2)计算子载波权值
weight_k = 2*level_k-1;

% 对每个窗进行计算，获得该窗下对应的CP长度
weight_matrix = zeros(N_windows,Len_windows);
choose_matrix = zeros(N_windows,Len_windows);
len_CP = zeros(1,N_windows);
for i = 1:N_windows
    
    weight_matrix(i,:) = weight_k((i-1)*Len_windows+1:i*Len_windows);% 将权重向量转变为权重矩阵，其中每一行为每一个窗的权重
    current_CP = weight_matrix(i,1);% 临时变量，用于权重相加
    choose_matrix(i,1) = current_CP;% 选择矩阵，记录相加权重的值
    for j = 2:Len_windows
        % 累加权重，进行判断
        if current_CP <= min_len_CP
            current_CP = current_CP + weight_matrix(i,j);
            choose_matrix(i,j) = weight_matrix(i,j);
            % 边界条件处理
            if j == Len_windows
                if current_CP <= min_len_CP % 仍未满足条件
                    len_CP(i) = min_len_CP;
                    break;
                else
                    len_CP(i) = current_CP;% 满足条件
                    break;
                end
            end
        
        % current_CP > min_len_CP，直接赋值    
        else
            len_CP(i) = current_CP;
            break;
        end
    end

end


end