Optimizing the performance of digital pulse interval modulation with guard slots for diffuse indoor optical wireless links

The performance of indoor optical wireless communication (OWC) systems degrades as the channel becomes dispersive and achieving higher data rates is problematic. In this study, different decoding algorithms are suggested to improve the performance of the digital pulse interval modulation (DPIM) scheme with guard slot(s) without incorporating an equalizer at the receiver. The normalized optical power requirement (NOPR) to achieve a slot error rate (SER) of 10-6 is calculated for a comparative study of different systems. A threshold decoding scheme with the optimum threshold level offers a significant reduction in NOPR compared to a fixed threshold level of 0.5. The hybrid approach in which a slot is detected by comparing received signal with a threshold level as well as amplitude of adjacent slots has potential to improve the performance. Moreover, with the decoding scheme adopted, which maximises the likelihood of a pulse within a symbol, there is marked improvement in the system performance.