function varargout = detect(sig_down,dlt,slt,ch_coefs,varargin)%DETECT Multidimensional data detector.%   D_E = DETECT(S,DLT,SLT,ALPHA) performs the maximum likelihood%   sequence estimation (MLSE) i.e. Viterbi algorithm on the received%   signal and returns the data estimations. The look-up tables DLT and%   SLT are used together with the external function BRMET which is%   called during the computation to evaluate branch metric ALPHA%   includes a channel complex path fadings.%%   [DATA_EST,STATE_EST] = DETECT(...) also returns a matrix including%   the track with most probable path in the code trellis. This matrix is%   required when the decoding process suppose to be displayed with%   DISPTRELL function. %%   [D_E,S_E] = DETECT(...,'PropertyName',PropertyValue,...)% %   Detect Property List% %   Echo           'on' | {'off'}%%   See also BRMET, DISPTRELL, MFILTER.%   Copyright 2001-2003 Kamil Anis, anisk@feld.cvut.cz%   Dept. of Radioelectronics, %   Faculty of Electrical Engineering%   Czech Technical University in Prague%   $Revision: 2.1 $  $Date: 2003/1/16 17:33:28 $%   --%   <additional stuff goes here>global ECHO TIMINGname = 'DETECT';[idt,tag] = iecho(name);nopts = length(varargin) / 2;opts = reshape(varargin,[2 nopts])';ord1 = strmatch('Echo',opts(:,1));% Echoif ~isempty(ord1) % first check whether local option exists	value1 = opts{ord1,2};	switch value1	case 'on'		ech = 1;	case 'off'		ech = 0;	otherwise		disp(' ');		disp([tag,'Invalid option for Echo property.']);		disp([idt,'Possible values are ''on''|{''off''}.']);		disp(' ');		ech = 0;	endelse	if ~isempty(ECHO) % than check whether global option exists		switch ECHO		case 'on'			ech = 1;		case 'off'			ech = 0;		otherwise			disp(' ');			disp([tag,'Invalid option for Echo property.']);			disp([idt,'Possible values are ''on''|{''off''}.']);			disp(' ');			ech = 0;		end	else % if there are no settings use the defaults		ech = 0; % default value	endend%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% BODY BEGIN %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%if ech	disp(' ');	disp([tag,'Performing data detection. This may take a while.']);	disp([idt,'Please wait...']);end[step_final,space_dim,frames] = size(sig_down);[s,md,foo] = size(dlt);load qam16.txt;if ~TIMING % disable timing when running performance measurement  tic;endfor k = 1:frames	% running multi-dimensional Viterbi algorithm	% make all starting paths unprobable except for the correct one	metric(1,2:s) = realmax;	for l = 1:step_final		for j = 1:s % current j		% finding all previous states s_pre leads to current sate j		[s_pre,foo] = find(slt == j);		% determining a pair position relevant to the state j		% {1,2,3,4,5,6,7,8} -> {1,2,3,4,1,2,3,4}		pos = mod(j - 1,md) + 1;		% picking-up the pairs corresponding to each of s_pre states		data_test = dlt(s_pre,pos,:);		data_test = reshape(data_test,[md space_dim]);		% mapping pairs to appropriate constellation		if md == 16 % 16QAM			for r = 1:space_dim				k1(:,r) = qam16(data_test(:,r) + 1,1);				k2(:,r) = qam16(data_test(:,r) + 1,2);			end			q_test = (2 * k1 - md - 1) - i * (2 * k2 - md - 1);		else % 4,8PSK			expr = i * 2 * pi / md;			q_test = exp(expr * data_test);		end		% evaluating branch metric		metric_d = brmet(sig_down(l,:,k),q_test,ch_coefs(:,:,k));		% adds the data_test metrices to the previous states		metric_md = metric(l,s_pre)' + metric_d;		% choosing a metric with lowest accumulated value		[metric_min,metric_pos] = min(metric_md);		% and storing it's value to the matrix of metrices		metric(l + 1,j) = metric_min;		% creates a states matrix of s_pre (with lowest metric)		vit_state(l + 1,j) = s_pre(metric_pos);		% creates a matrix of appropriate data_test		vit_data(l + 1,j) = pos - 1;		end	end	% finding the best path at the trellis end	[foo,state_best] = min(metric(end,:));	state_est(step_final + 1) = state_best;	% back tracking	for l = step_final:-1:1		state_est(l) = vit_state(l + 1,state_est(l + 1));		data_est(l,:,k) = vit_data(l + 1,state_est(l + 1));	endendif ~TIMING  totaltime = toc;else  totaltime = 0;endvarargout = {data_est,state_est};%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% BODY END %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%if ech	hour = round(totaltime / 3600);	mins = round(totaltime / 60);	secs = mod(totaltime,60);	  str1 = num2str(frames * step_final * s);	str2 = sprintf('%1d',hour);	str3 = sprintf('%1d',mins);	str4 = sprintf('%1.1f',secs);		disp([idt,'Total decoding complexity -> ',str1,' steps.']);	disp([idt,'Total elapsed time -> ',str2,' hrs, ',str3,' min, ',str4,...        ' sec.']);	disp(' ');end