synchronization.m

MATLAB-functions used in Space-Time Project Simulation

function [corr_max,sample_nr]=synchronization(in_data_block, fs, T, training_sequence, model)

% 	[corr_max,sample_nr]=synchronization(in_data_block, fs, T, training_sequence, model)
%
%	
%	Output:
%	sample_nr               - Sample number, counted from first value in inphase_data_block
%                               where sampling is best performed.
%   corr_max                - Max value of the correlation 	
%
%   Input:
%	in_data_block 	        - Output from MF
%   fs                 	    - Sampling rate
%   T                  	    - Symboltime
%   training_sequence 	    - Training_sequence, same as concatenated in transmitter.
%	model					- Specifies if Alamouti-coding has been used.
%						        model = 0 : No Alamouti-coding in transm.
%						        model = 1 : Alamouti-coding in transm.
%   
%   Short Theoretical Background for the Function:
%
%   Slides the training-sequence over the recieved matched-filtered
%   inphase- or quadrature component and returns the number of the sample where the
%   first value of the train.-seq. has it's start.
%
%   The implentation can be compared to theory described in QPSK-lab
%   performed in the course of communication theory, year 2001 KTH.
%
%	 Assuming first part of data is training-sequence through antenna 1.
%	 (and performing sync. only on these data, not 2:nd antennas train.)
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
%%% Function part of simulation for Space-Time
%%% coding project, group Grey-2001.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%   Author: Stefan Uppg錼d
%   Date: 2001-03-20 and 21
%   Version: 1.0
%   Revision (Name & Date % Spec): 
%	1.1	SU	2001-03-24	Adding the Alamouti-functioncall.
%   1.2 SU  2001-03-25  Decreased the slidingdistance to one train.seq.length.
%   1.3 SU  2001-03-27  Added the absolute function after for-loop.
%   1.4 SU  2001-03-28  Increased the slidingdistance to three train.seq.length
%   1.5 FH  2001-03-30  returns the maxvalue of the correlation 
%   1.6 SU  2001-04-04  Removed the Alamouti-coding.
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%
%%% Correlates the inphase-part with 
%%%

r = in_data_block;          % Rename variable to make the code easier to read.

c1 = bpsk(training_sequence,model);
L = length(c1);             % Length of BPSK:ed training-sequence.
Q = fs*T;                   % Number of samples per symbol.

sum_of_r_times_c1 = [];

for(m=1:1*Q*L)              % Lets m = sample_time slides one time the train.seq.distance.
    sum_of_r_times_c1 = [sum_of_r_times_c1 (r(m : Q: L*Q+m-1) * c1')];
end
sum_of_r_times_c1 = abs(sum_of_r_times_c1);
figure(10), plot(sum_of_r_times_c1)
[corr_max, sample_nr] = max(sum_of_r_times_c1); % Skips the abs(...) noted in QPSK-lab.