fine_sync.m

一个UWB仿真程序包

function [fine_sync_index] = fine_sync(rx_down,corr_template,thld,...
                blocks_per_code_symbol,code_len,coarse_sync_index,PLOT_DEBUG);
    
    %calculate the correlation only in region we need it...
    %temp_mat = zeros(blocks_per_code_symbol,length(corr_template));
    %for i=1:blocks_per_code_symbol*31
    %    temp_mat(i,:) = rx_down(coarse_sync_index+i-1:coarse_sync_index+length(corr_template)+i-2);
    %end
    %corr = temp_mat * corr_template';
%     corr2 = conv(rx_down(coarse_sync_index:coarse_sync_index+code_len*blocks_per_code_symbol+length(corr_template)), fliplr(corr_template));
%     corr = corr2(length(corr_template):length(corr_template)+blocks_per_code_symbol*code_len-1);
%     % %  clear temp_mat; %free memory
%     %determine max of corr -> strongest path
%     [max_corr4, ind_corr4] = max(corr);
%     
%     %we now go backwards through the correlation until we find one sample
%     %that is not above the threshold, the max number of steps we go back is
%     %blocks_per_code_symbol/2
%     current_index = ind_corr4;
%     t0_index = ind_corr4;
%     for i=1:floor(blocks_per_code_symbol/2)
%         current_index = current_index - 1;
%         %wrap around if it goes over the beginning
%         if(current_index == 0)
%             current_index = length(corr);
%         end
%         if(corr(current_index) >= thld)
%             t0_index = t0_index - 1;
%         else
%             break;
%         end
%     end
%     
%     %fine_sync_index = coarse_sync_index + t0_index - 1;
%     if(PLOT_DEBUG)
%         %     figure
%         %     plot(corr2)
% 
%         figure
%         plot(corr)
%         hold on
%         plot(thld*ones(1,length(corr)),'m')
%         line([t0_index t0_index],[0 max(corr)],'Color','g')
%         line([ind_corr4 ind_corr4],[0 max(corr)],'Color','y')
%     end
    
   
    
     
    
    %from -block to + 2blocks
    corr3 = conv(rx_down(coarse_sync_index-blocks_per_code_symbol:coarse_sync_index+3*blocks_per_code_symbol+length(corr_template)), fliplr(corr_template));
    corr3 = corr3(length(corr_template):length(corr_template)+blocks_per_code_symbol*4);
    %[max_corr4, ind_corr4] = max(corr3(blocks_per_code_symbol:2*blocks_per_code_symbol));
    [max_corr4, ind_corr4] = max(corr3);
    %ind_corr4 = ind_corr4 + blocks_per_code_symbol - 1;
    
    %we now go backwards through the correlation until we find one sample
    %that is not above the threshold, the max number of steps we go back is
    %blocks_per_code_symbol/2
    current_index = ind_corr4;
    t0_index = ind_corr4;
    for i=1:floor(blocks_per_code_symbol/2)
    %for i=1:blocks_per_code_symbol-1
        current_index = current_index - 1;
        %wrap around if it goes over the beginning
        if(current_index == 0)
            break;
        end
        if(corr3(current_index) >= thld && corr3(current_index)>corr3(current_index+blocks_per_code_symbol))
            t0_index = current_index;
        end
    end
    fine_sync_index = coarse_sync_index - blocks_per_code_symbol + t0_index - 1;
    
    
    if(PLOT_DEBUG)
        %     figure
        %     plot(corr2)

        figure
        plot(corr3)
        hold on
        plot(thld*ones(1,length(corr3)),'m')
        line([t0_index t0_index],[0 max(corr3)],'Color','g')
        line([ind_corr4 ind_corr4],[0 max(corr3)],'Color','y')
    end

%     coarse_template = reshape( ...
%         repmat(abs(len31_preamble_code(5)),blocks_per_code_symbol, 1), ...
%         1,31*blocks_per_code_symbol);
%     %repeat correlation template G times
%     coarse_template = repmat(coarse_template,1,4);
%     corr4 = conv(rx_down(coarse_sync_index-blocks_per_code_symbol:coarse_sync_index+blocks_per_code_symbol+length(coarse_template)), fliplr(coarse_template));
%     corr4 = corr4(length(coarse_template):length(coarse_template)+blocks_per_code_symbol*2-1);
%     [max_corr4, ind_corr4] = max(corr4);
%     if(PLOT_DEBUG)
%         %     figure
%         %     plot(corr2)
% 
%         figure
%         plot(corr4)
%         hold on
%         plot(thld*ones(1,length(corr4)),'m')
%         %line([t0_index t0_index],[0 max(corr3)],'Color','g')
%         line([ind_corr4 ind_corr4],[0 max(corr4)],'Color','y')
%     end
    
    
    %corr2 = conv(rx_down,fliplr(corr_template));
%     vinc = corr(corr_coarse_sync_index-...
%         blocks_per_code_symbol:corr_coarse_sync_index+blocks_per_code_symbol);
%     [max_vinc ind_vinc] = max(vinc);
%     %get the corresponding index in corr
%     corr_fine_sync_index2 = corr_coarse_sync_index + ind_vinc - blocks_per_code_symbol - 1;
%     %get the corresponding index in the received signal
%     fine_sync_index2 = corr_fine_sync_index2 - (length(corr_template)-1)

% % corr3 = conv(rx_down(coarse_sync_index:coarse_sync_index+blocks_per_code_symbol+length(corr_template2)), fliplr(corr_template2));
% % thld3 = noise_var * chi2inv(THLD_PROBA, (T_INT * 2* RX_BW) * N_INT * G * 16)

return;