Novel approach for increasing the peak-to-average optical power ratio in rate-adaptive optical wireless communication systems

A new and simple rate-adaptive transmission scheme for indoor unguided optical links is proposed. This scheme is based on the use of variable silence periods and on-off keying (OOK) formats with memory. These variable silence times are used for modifying the statistics of the amplitude sequence regarding the statistics of the message sequence, giving an increase in the peak-toaverage optical power ratio. This is a favourable characteristic in intensity modulation and direct detection infrared links. In this fashion, OOK formats with Gaussian pulses modifying their position within the symbol period are adopted, obtaining a good tradeoff between performance and required complexity. This is applied to links operating at a high initial bit rate, providing a signalling rate with a wide dynamic range and a relevant improvement in performance with gradual complexity in implementation, compared with the scheme proposed and specified in the Advanced Infrared (AIr) standard by the Infrared Data Association (IrDA), which is based on repetition coding and pulse-position modulation.