Multiple-subcarrier modulation for non-directed wireless infrared communication

We examine multiple-subcarrier modulation (MSM) schemes for wireless infrared digital communication in the indoor environment. Intensity-modulation with direct-detection (IM/DD) as used, which results in equivalent baseband channels with a non-negativity constraint on the input. The power efficiencies of modulation schemes are compared at 30 Mb/s and 100 Mb/s over an ensemble of experimentally determined multipath channels. It is found that MSM schemes can allow operation at higher data rates than single-carrier modulation schemes without equalization. Moreover, MSM schemes can be more bandwidth efficient and also can provide a simple and flexible method for multiple access to the channel. However, they are not as power-efficient as single-carrier schemes and this will limit their use to applications that are not power-limited.