Spectral and Energy Efficiency of DCO-OFDM in Visible Light Communication Systems with Finite-Alphabet Inputs

TL;DR

This paper derives the exact achievable rate of DCO-OFDM in visible light communication with finite-alphabet inputs, and proposes power allocation schemes to maximize spectral and energy efficiency under power constraints.

Contribution

It provides the first derivation of the achievable rate for DCO-OFDM with finite-alphabet inputs and introduces novel power allocation schemes for efficiency maximization.

Findings

Exact achievable rate derived for DCO-OFDM with finite-alphabet inputs.

Multi-level mercury-water-filling scheme maximizes spectral efficiency.

Dinkelbach-type scheme optimizes energy efficiency.

Abstract

The bound of the information transmission rate of direct current biased optical orthogonal frequency division multiplexing (DCO-OFDM) for visible light communication (VLC) with finite-alphabet inputs is yet unknown, where the corresponding spectral efficiency (SE) and energy efficiency (EE) stems out as the open research problems. In this paper, we derive the exact achievable rate of {the} DCO-OFDM system with finite-alphabet inputs for the first time. Furthermore, we investigate SE maximization problems of {the} DCO-OFDM system subject to both electrical and optical power constraints. By exploiting the relationship between the mutual information and the minimum mean-squared error, we propose a multi-level mercury-water-filling power allocation scheme to achieve the maximum SE. Moreover, the EE maximization problems of {the} DCO-OFDM system are studied, and the Dinkelbach-type power allocation scheme is developed for the maximum EE. Numerical results verify the effectiveness of the proposed theories and power allocation schemes.