Baseline Wander Effects on Systems Employing Digital Pulse Interval Modulation

Fluorescent lamps introduce a periodic interference signal in optical wireless receivers, which has the potential to severely degrade link performance. Usually, electrical high-pass filtering is employed to mitigate the effects of this interference, but this results in baseline wander or intersymbol interference. Digital pulse interval modulation (DPIM) is a modulation technique which has been shown to be suitable for deployment in optical wireless communication systems and this paper examines the effect of baseline wander on systems employing DPIM. A new expression is given for the slot autocorrelation function of DPIM and, from this, the power spectral density is calculated. The error performance of DPIM, as a function of high-pass filter (HPF) cut-on frequency, is compared with the more established techniques of on-off keying using non-return to zero signalling (OOK) and pulse position modulation (PPM), using both numerical analysis and computer simulation.