Flip-OFDM for Unipolar Communication Systems

TL;DR

This paper compares Flip-OFDM and ACO-OFDM in unipolar communication systems, showing they have similar performance but Flip-OFDM is simpler, and introduces a noise reduction detection scheme with significant benefits.

Contribution

It provides the first detailed performance comparison of Flip-OFDM and ACO-OFDM and proposes a novel noise filtering detection scheme for Flip-OFDM.

Findings

Flip-OFDM and ACO-OFDM have comparable performance.

Flip-OFDM offers 50% complexity savings over ACO-OFDM.

The new detection scheme reduces noise by nearly 3dB.

Abstract

Unipolar communications systems can transmit information using only real and positive signals. This includes a variety of physical channels ranging from optical (fiber or free-space), to RF wireless using amplitude modulation with non-coherent reception, to baseband single wire communications. Unipolar OFDM techniques enable to efficiently compensate frequency selective distortion in the unipolar communication systems. One of the leading examples of unipolar OFDM is asymmetric clipped optical OFDM (ACO-OFDM) originally proposed for optical communications. Flip-OFDM is an alternative approach that was proposed in a patent, but its performance and full potentials have never been investigated in the literature. In this paper, we first compare Flip-OFDM and ACO-OFDM, and show that both techniques have the same performance but different complexities (Flip-OFDM offers 50% saving). We then propose a new detection scheme, which enables to reduce the noise at the Flip-OFDM receiver by almost 3dB. The analytical performance of the noise filtering schemes is supported by the simulation results.