Comparison of DCO-OFDM and M-PAM for LED-Based Communication Systems

TL;DR

This paper compares M-PAM and DCO-OFDM modulation schemes for LED-based communication systems, demonstrating that optimized M-PAM can achieve higher data rates under practical LED constraints.

Contribution

The study introduces an optimized M-PAM scheme with waveform design and compares it to an optimized DCO-OFDM, highlighting the advantages of M-PAM in LED communication.

Findings

M-PAM with optimized processing outperforms DCO-OFDM in data rate.

Waveform design reduces inter-symbol interference in M-PAM.

Optimized DCO-OFDM is less efficient under LED bandwidth and power constraints.

Abstract

Light-emitting diode (LED)-based communications, such as visible light communications (VLC) and infrared (IR) communications, are candidate techniques to provide short-range and high-speed data transmission. In this paper, M-ary pulse amplitude modulation (M-PAM), used as a high bandwidth efficiency scheme, is compared with an optimized DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM) scheme. Considering the bandwidth limit and constrained peak transmitted power characteristics of LEDs, a bit loading algorithm with an optimized modulation index is used for the DCO-OFDM. To reduce the inter-symbol interference caused by LEDs, a waveform design algorithm with a minimum mean squared error (MMSE) equalizer is applied to the M-PAM system. From numerical results, M-PAM with the optimized signal processing can provide a substantially higher data rate than the optimally designed DCO-OFDM for the same performance.