function en_output = encoderm( x, g, alpha, puncture )


% Copyright Nov. 1998 Yufei Wu


% MPRG lab, Virginia Tech.


% for academic use only





% uses interleaver map 'alpha'


% if puncture = 1, unpunctured, produces a rate 1/3 output of fixed length


% if puncture = 0, punctured, produces a rate 1/2 output 


% multiplexer chooses odd check bits from RSC1 


% and even check bits from RSC2





% determine the constraint length (K), memory (m) 


% and number of information bits plus tail bits.





[n,K] = size(g); 


m = K - 1;


L_info = length(x); 


L_total = L_info + m;  





% generate the codeword corresponding to the 1st RSC coder


% end = 1, perfectly terminated;


input = x;


output1 = rsc_encode(g,input,1);





% make a matrix with first row corresponing to info sequence


% second row corresponsing to RSC #1's check bits.


% third row corresponsing to RSC #2's check bits.





y(1,:) = output1(1:2:2*L_total);


y(2,:) = output1(2:2:2*L_total);








% interleave input to second encoder


for i = 1:L_total


   input1(1,i) = y(1,alpha(i)); 


end


output2 = rsc_encode(g, input1(1,1:L_total), -1 );


y(3,:) = output2(2:2:2*L_total);





% paralell to serial multiplex to get output vector


% puncture = 0: rate increase from 1/3 to 1/2;


% puncture = 1; unpunctured, rate = 1/3;








if puncture > 0		% unpunctured


   for i = 1:L_total


       for j = 1:3


           en_output(1,3*(i-1)+j) = y(j,i);


       end


   end


else			% punctured into rate 1/2


   for i=1:L_total


       en_output(1,n*(i-1)+1) = y(1,i);


       if rem(i,2)


      % odd check bits from RSC1


          en_output(1,n*i) = y(2,i);


       else


      % even check bits from RSC2


          en_output(1,n*i) = y(3,i);


       end 


    end  


end





% antipodal modulation: +1/-1


en_output = 2 * en_output - ones(size(en_output));