The statement in the subject is refering to Erich Cosby's tutorial for OFDM. I'm simulating OFDM in Simulink with the aim of later converting it for a DSP. I use BPSK before the OFDM operation. With BPSK, all my binary inputs would be converted to either 1 or -1 in the IQ spectrum. In Simulink, the outputs contain very small values for the imaginary part i in the range of around -16 eg, binary 1 would be 1+1.22e-16i and binary 0 would be otherwise.. Would this small imag value be sufficient to fulfill the statement and produce a real time signal? Would it cause any problems with the DSP implementation?