Performance analysis of indoor infrared wireless systems using PPM CDMA with hard limiter on diffuse channels

摘要

As infrared link designs, diffuse channels are robust against shadowing, however diffuse channels are subject to multipath dispersion that causes intersymbol interference (ISI). The performance of infrared wireless systems using PPM CDMA is analyzed on LOS channels and diffuse channels where ISI is assumed to affect only two chips. However, in the practical situation, ISI often affects more than two chips. This report analyzes the performance of indoor infrared wireless systems using PPM CDMA on diffuse channels by taking the effects of ISI over several chips into account. Then we propose PPM CDMA system with Hard Limiter (HL) to mitigate the effects of ISI. We show that how much the transmitted power should be increased on diffuse channels, and that the performance of the system using PPM CDMA is superior to that of the system using on-off keing (OOK) CDMA on diffuse channels. We also show that the performance of the PPM CDMA system with HL is superior to that of the unequalized PPM CDMA.