qpskdecoder.m

simulation module for visual wireless sensor network

% ------------------------------------------------------------------------------- %
% QPSKDecoder(..) Module 
% -----------------------
% This module does QPSK Decoding. 
% The constellation points are assumed to be at (1,1), (1,-1),(-1,1) and (-1,-1). 
% (i.e, at 45,135,-135,-45 degrees) respectively and the signal mapping is assumed
% to be

% B1 B2   I   Q
% --------------
%  0  0  -a  -a
%  0  1  -a  +a
%  1  0  +a  -a
%  1  1  +a  +a
%
% Outputs : The I and Q Modulated (received) Symbol streams.
% Inputs : The decoded bit streams.
%
% Note :
% -------
% This is just for simulation purposes only and so no really fancy things are done
% here. The signalling points are chosen so that the encoding and decoding can be
% done as FAST as possible (by just using a max of two simple statements).
%
% Written by,
% -----------
% Vijaya Chandran Ramasami,
% Radar Systems Lab,
% The University of Kansas, 
% Lawrence, KS 66044.
% E-Mail - [e-mail]
% ------------------------------------------------------------------------------- %

function [BitStreamOne, BitStreamTwo] = QPSKDecoder(I_Symbols, Q_Symbols)

BitStreamOne = I_Symbols > 0;
BitStreamTwo = Q_Symbols > 0;