Multiple-subcarrier modulation for nondirected wireless infrared communication

TLDR

The study investigates multiple‑subcarrier modulation schemes for indoor wireless infrared digital communication, including carrier selection and power shaping to enhance performance. The authors use intensity modulation with direct detection, modeling equivalent baseband channels with a non‑negativity constraint, and compare power efficiencies of MSM schemes at 30 Mb/s and 100 Mb/s across experimentally measured multipath channels. MSM enables higher data rates than single‑carrier modulation without equalization, offers greater bandwidth efficiency and a simple, flexible multiple‑access method, yet its lower power efficiency restricts its use to non‑power‑limited applications.

Abstract

We examine multiple-subcarrier modulation (MSM) schemes for wireless infrared digital communication in the indoor environment. Intensity modulation with direct detection (IM/DD) is employed, which results in equivalent baseband channels with a nonnegativity 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. Carrier selection and power shaping are examined as methods for improving MSM performance. 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 which are not power limited.