Coded PPM based modulations for infrared WLAN'S

Abstract

In this communication we consider the use of PPM based modulation methods, such as the hybrid modulation method called Amplitude and Pulse-Position Modulation (APPM) and Overlapping Pulse-Position Modulation (OPPM) to improve the performance of infrared WLAN’s, by the use of Trellis-Coded Modulation (TCM) codes. We derive the best codes for some APPM and OPPM schemes, and the results show that non-negligible coding gains without bandwidth expansion can be obtained with trellis codes of moderate complexity. The theoretical coding gains are confirmed by simulation. Finally a set of multirate systems using the derived TCM coding are evaluated, and their practical benefits observed in terms of connectivity improvements.