ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV / We investigate pulse position modulation (PPM) and multipulse PPM (MPPM) for free space op- tical channels using bit interleaved coded modulation with iterative decoding. Data bits are first encoded by using a non recursive convolutional code and the coded bits after an interleaver are modulated before transmission. Iterative decoding is performed at the receiver. Optimized mapping is designed for MPPM. A genetic algorithm is used to find the optimized mapping for MPPM. Our simulation results show that a significant improvement in the error performance can be achieved by using optimized mapping and iterative decoding at the receiver.

In this paper, we investigate an adaptive decode-and-forward (DF) cooperative diversity scheme based on bit interleaved coded modulation with iterative decoding (BICM-ID). Data bits are first encoded by using a convolutional code and the coded bits after an interleaver are modulated before transmission. Iterative decoding is used at the receiver. Optimized constellation mapping is designed jointly for the source and the relay using a genetic algorithm. A novel error performance analysis for the adaptive DF scheme using BICM-ID is proposed. The simulation results agree well with the analytical results at high signal-to-noise ratio (SNR). More than 5.8 dB gain in terms of SNR over the existing mappings is achieved with proposed mappings.