A Simple Capacity-Achieving Scheme for Channels with Polarization-Dependent Loss

TL;DR

This paper introduces a simple, universal scheme that achieves channel capacity in polarization-dependent loss channels by transforming them into scalar Gaussian channels, significantly reducing SNR penalties.

Contribution

It presents a novel interference cancellation and precoding scheme that is both optimal and simple, transforming PDL channels into standard Gaussian channels for efficient coding.

Findings

Achieves near-capacity performance with minimal SNR penalty

Reduces SNR penalty from 4 dB to 1 dB under 6 dB PDL

Transforms PDL channels into scalar Gaussian channels

Abstract

We demonstrate, for a widely used model of channels with polarization dependent loss (PDL), that channel capacity is achieved by a simple interference cancellation scheme in conjunction with a universal precoder. Crucially, the proposed scheme is not only information-theoretically optimal, but it is also exceptionally simple and concrete. It transforms the PDL channel into separate scalar additive white Gaussian noise channels, allowing off-the-shelf coding and modulation schemes designed for such channels to approach capacity. The signal-to-noise ratio (SNR) penalty incurred under 6 dB of PDL is reduced to the information-theoretic minimum of a mere 1 dB as opposed to the 4 dB SNR penalty incurred under naive over-provisioning.