A selective detection receiver for PAM-DMT in optical wireless communication systems

This paper investigates the performance improvement of the receiver for pulse-amplitude-modulated discrete multitone modulation (PAM-DMT) system in intensity modulated direct detected optical channel. In conventional receiver for PAM-DMT, data are only extracted from the imaginary parts of subcarriers while the real parts which contain clipping noise are simply discarded, causing a major loss of the received power. It has been proved that exploiting the structure of the clipping noise and detecting the combination of the real parts and the imaginary parts would improve the optical power efficiency. In this paper, a selective detection receiver based on the one which is characterized by temporal diversity combining for PAM-DMT is proposed, leading to enhanced bit error rate performance. It generates some transmitted information candidates with new sign matrices and choose the optimal one which has the minimum Euclidean distance with the original received one. It can also be employed in additive white Gaussian noise channel, multipath channel and multiple-input and multiple-output channel. Simulations show that the proposed receiver achieves a better gain of at least 1.0 dB in Eb/N0 at system BER of 10-4 with 16-PAM modulation than the temporal diversity combining receiver in multipath channel.