%differentially decodes a PSK diff encoded symbol
%inputs/outputs
%inputs: in_vec (complex PSK symbols), num_sym (size of in_vec)
%output: out_vec (complex PSK of size num_sym)
%The first decoded symbol could be in error because of initialization

function [out_vec] = diff_dec(in_vec, num_sym)

    initial=1/sqrt(2)*(1+j);
    for ii=1:num_sym
        if(ii==1) 
            out_vec(ii)=in_vec(ii)*conj(initial);
        else
            out_vec(ii)=in_vec(ii)*conj(in_vec(ii-1));
        end
        
            
    end