Soft-metric based channel decoding for photon counting receivers

TL;DR

This paper explores the use of soft-metric LDPC codes for photon counting receivers in polarization-based binary communication, demonstrating improved error rates and capacity gains by leveraging the photon distribution's additional degree of freedom.

Contribution

It introduces a soft-metric decoding approach for photon counting channels with polarization encoding, enhancing performance over traditional methods.

Findings

Improved frame and bit error rates with soft-metric LDPC decoding.

Potential capacity gains using photon counting detectors.

Effective utilization of photon distribution in polarization channels.

Abstract

We address photon-number-assisted, polarization- based, binary communication systems equipped with photon counting receivers. In these channels information is encoded in the value of polarization phase-shift but the carrier has and additional degree of freedom, i.e. its photon distribution, which may be exploited to implement binary input-multiple output (BIMO) channels also in the presence of a phase-diffusion noise affecting the polarization. Here we analyze the performances of these channels, which approach capacity by means of iteratively decoded error correcting codes. In this paper we use soft-metric- based low density parity check (LDPC) codes for this purpose. In order to take full advantage of all the information available at the output of a photon counting receiver, soft information is generated in the form of log-likelihood ratios, leading to improved frame error rate (FER) and bit error rate (BER) compared to binary symmetric channels (BSC). We evaluate the classical capacity of the considered BIMO channel and show the potential gains that may be provided by photon counting detectors in realistic implementations.