function [alpha,theta]=channel_estimator(quad_train_seq, inphase_train_seq, orig_train, model, channel)%   [alpha,theta]=channel_estimator(quad_train_seq, inphase_train_seq, orig_train, model, channel)%%   Output:%   alpha		        - Alpha in channelmodel alpha = exp(j*theta)
%   theta               - Theta in dito%%   Input:%   quad_train_seq	    - Quadrature part of training-sequence as seen in receiver.
%   inphase_train_seq   - Inphase dito	 %   orig_train  	    - Original training-sequence. (Binary!) (on Antenna 1!)
%							   (not using training info from antenna 2.)%	 model			    - If 0: No Alamouti coding (only sending on antenna 1)
%								if 1: Alamouti coding is used for transmitting antennas.
%	 channel	        - 1 if referring to channel 0 (or 2) in Alamouti's paper.
%								2 if referring to channel 1 (or 3)%   %   Short Theoretical Background for the Function:%%   Only one channel is estimated!!! 
%	 
%	Estimates the one-tap channel. %   (Referring to Appendix A in George J鰊grens master of sciense%   thesis for mathematical theories)%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     %%% Function part of simulation for Space-Time%%% coding project, group Grey-2001.%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   Author: Stefan Uppg錼d%   Date: 2001-03-22%   Version: 1.1%   Revision (Name & Date):
%		SU	2001-03-24 Adding variable: model and modifying code for that%						  Also: changed inputargument "sent_training_seq" be binary.
%						  (not BPSK:ed)%       SU  2001-03-27 Added if for calculating theta.%       SU  2001-04-08 Put the mean-expressions on 1/abs(w) and angle(w) instead of on r*conj(r).%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% This is the straigt-forward channel-estimator according to the described theories.
sent_train_seq = bpsk(orig_train,model);r = complex(inphase_train_seq, quad_train_seq);%Sigma_tt = mean(sent_train_seq .* sent_train_seq);Sigma_td = mean(sent_train_seq .* r);Sigma_tt = 1;h = Sigma_td ./ Sigma_tt;alpha = abs(h);        theta = angle(h);