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function [y,NextSignal]=mai(CurrentSignal,LastSignal,ChanCode,MPathDelay,MPathAmp,fDoppler,SamplesPerChip,PulseShape,MaxOffset) 
%********************************************************************************************* 
% y=mai(NumInterferers,ChanCode,MPathDelay,MPathAmp,SamplesPerChip,PulseShape,MaxOffset) 
% 
% Copyright 2002 The Mobile and Portable Radio Research Group 
% 
%This function generates the mutual access interference (MAI) for one frame.  Each interferer 
%has an offset which is equal to an integer multiple of the sampling period.  This offset  
%will not exceed MaxOffset, which is defined in terms of chips.  For each interferer, 
%the data and control bits are generated at random, spread with the channel code and  
%then scambled with a different code per interferer.  The resulting frame is the pulse shaped 
%and processed through the channel defined by MPathDelay and MPathAmp.  Once this is  
%is done for each interferer, the signals are then added to create the MAI signal 
% 
%Parameters 
%   Input 
%      NumInterferers   Scalar   The number of interfering signals 
%      ChanCode         Matrix   The channel code matrix.  For simplicity each interferer 
%                                will have the same channel code.  Further, each interferer 
%                                will only have one DPDCH.  Multiple DPDCHs per interferer 
%                                will be added at a later time 
%      MPathDelay       Vector   The multipath delays in terms of number of samples 
%                                For simplicity, each interferer will have the same  
%                                multipath fading profile 
%      MPathAmp         Vector   The average energy for each multipath delay 
%      SamplesPerChip   Scalar   The number of samples per chip 
%      PulseShape       Vector   The pulse shaping filter impulse response used for the system 
%      MaxOffset        Scalar   The maximum allowable offset for each interferer in terms of  
%                                chips. 
%   Output 
%      y                Vector   The mutual access interference (MAI) signal 
% 
%********************************************************************************************* 
ChipsPerFrame=38400; 
SigLength=length(CurrentSignal); 
MaxDelay=max(MPathDelay); 
y=zeros(1,SigLength+MaxDelay); 
[NumInterferers,col]=size(CurrentSignal); 
 
for k=1:NumInterferers 
   %***************************** 
	% DEBUG CODE -- MUST BE REMOVED 
	rand('state',0); 
	% DEBUG CODE -- MUST BE REMOVED 
	%***************************** 
 
    
   SF=size(ChanCode,1); 
   %Random Generation of Control Bits  
   %The specific sequence should not be that important 
   ControlBits=sign(rand(1,150)-0.5); 
   %Generate Scramble Sequence 
   ScrambleCodeNumber = round((2^24-1)*rand(1)); 
   ScrambleCode=scramble_long(ScrambleCodeNumber); 
    
   %******************** 
   %Debugging Purposes Only 
 %  if k==1 
      fee=[ControlBits.';ScrambleCodeNumber]; 
      save testdat.txt fee -ascii  
 %  end 
   %Debugging Purposes Only 
   %******************** 
    
   %Generate uplink Frame for interferer 
   UplinkFrame=gen_uplink_wcdma_frame(1,ScrambleCode.',ChanCode,ControlBits,1,1); 
   NextSignal(k,:)=GenWCDMAUplinkSignal(UplinkFrame,UplinkFrame,UplinkFrame,PulseShape,SamplesPerChip); 
   %incorporate offset 
   offset=round(SamplesPerChip*MaxOffset*2*(rand(1,1)-0.5)); 
   %*********************************** 
   %DEBUG CODE 
   offset = 10; 
   %DEBUG CODE 
   %*********************************** 
 
   if offset > MaxDelay 
      MAIUplinkSignal=[LastSignal(k,(SigLength-offset+1):SigLength),CurrentSignal(k,1:(SigLength+MaxDelay-offset))]; 
   elseif offset >= 1 
      MAIUplinkSignal=[LastSignal(k,(SigLength-offset+1):SigLength),CurrentSignal(k,1:(SigLength)),NextSignal(k,1:(MaxDelay-offset))]; 
   elseif offset < 0 
      MAIUplinkSignal=[CurrentSignal(k,1-offset:SigLength),NextSignal(1:MaxDelay-offset)]; 
   else 
      MAIUplinkSignal=[CurrentSignal(k,:),NextSignal(k,1:MaxDelay)]; 
   end 
   %Apply Multipath Channel 
   MPathSignal=MaiMpathChannel(MAIUplinkSignal,MPathDelay,MPathAmp,fDoppler,SamplesPerChip); 
   y=y+MPathSignal; 
end