Differential pulse position modulation for power-efficient wireless infrared communication

In this paper we examine the use of differential pulse-position modulation (DPPM) for indoor wireless infrared communication. We show that for a given bandwidth, DPPM requires significantly less average power and provides higher throughput than PPM. We examine the power requirement of DPPM in the presence of multipath intersymbol interference (ISI) and show that ISI penalty is essentially determined by the delay spread-bandwidth product. To reduce the ISI penalty, we propose chip-rate equalization and compare its performance to optimum maximum-likelihood sequence detection. We also derive the power spectrum of DPPM signals.