down_sampler.m

MATLAB-functions used in Space-Time Project Simulation

function [symbols]=down_sampler(indata,sample_nr,fs,T,block_length)

%   [symbols]=down_sampler(indata,sample_nr,fs,T,block_length)
%
%	Output:
%	symbols         - Symbols after downsampling
%   
%   Input:
%   indata          - Symbols after matched filter          
%	sample_nr       - The time to sample indata, given as a sample number
%   fs              - Sampling frequency
%   T               - Symbol period
%   block_length    - Length of original indatablock = length of the 
%                     output variable symbols 
%
%   Short Theoretical Background for the Function:
%   
%   Downsamples indata. 
%   sample_nr decides which sample to begin sampling on. 
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
%%% Function part of simulation for Space-Time
%%% coding project, group Grey-2001.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%   Author: Fredrik Hansson
%   Date: 2001-03-21
%   Version: 1.0
%   Revision (Name & Date):
%   1.1 SU 2001-03-25   Added the if-expression to avoid sampling outside indata-vector
%                       if syncroniztion-function "failed".
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

oversamp = fs*T;
last_symbol = (sample_nr + (block_length-1)*(oversamp));
if (last_symbol > length(indata)) % avoiding sampling outside indata when sample_nr is bad.
    sample_nr = length(indata) - (oversamp * block_length)
    last_symbol = (sample_nr + (block_length-1)*(oversamp));
    
end

symbols = indata(sample_nr:oversamp:last_symbol); % keep every oversamp磘h symbol beginning at sample_nr