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function FrameStart= findfrm(SignalIn, FrameGap, quickrate,zerotime) 
%FINDFRM Finds the start of a COFDM frame 
%	FrameStart = findfrm(SignalIn, FrameGap, quickrate,zerotime) 
%	Find the approximate starting location 
%	zerotime : zeroed time of the guard period 
%	Copyright Eric Lawrey 1997 
% 
 
SignalIn = abs(SignalIn);		%Envelope detect the signal 
 
%========================================= 
% Subsample to find approx start location 
%========================================= 
index = 1:quickrate:length(SignalIn); 
SubSignal = SignalIn(index);	%Subsample the signal 
SubFilt = filter(ones(1,round(FrameGap/quickrate)),1,SubSignal); 
SearchSig1 = SubFilt(round(FrameGap/quickrate):length(SubFilt)); 
approxstart = min((find(SearchSig1==min(SearchSig1))+... 
		FrameGap/quickrate)*quickrate-zerotime); 
%plot(SearchSig1); 
%============================================================ 
% Narrow down the search to find the exact starting location 
%============================================================ 
Offset = round(approxstart-1.1*FrameGap);	%Starting location of accurate search 
EnvFilt = filter(ones(1,FrameGap),1,... 
	  SignalIn(Offset:round(approxstart+FrameGap/3))); 
%plot(EnvFilt); 
 
%============================================================================ 
%Find the minimum of the integral ensuring that it is at least one frame time 
%before the end of the wave file. (ignore the first symbol period) 
%============================================================================ 
SearchSig = EnvFilt(FrameGap:length(EnvFilt)); 
minsig = find(SearchSig==min(SearchSig))+FrameGap; 
 
%Calc the expect start of the frame 
%Pick the frame start just before the normal starting time to allow for timming 
%errors in both directions, i.e. early and late 
FrameStart = min(minsig-zerotime+Offset); 
CalcStart = FrameStart;