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