# Improving Data Communication of Enhanced Loran Systems Using 128-ary Polar Codes

## TL;DR

This paper improves the error performance and data transmission efficiency of eLoran systems by replacing Reed-Solomon codes with 128-ary polar codes.

## Contribution

Proposes using 128-ary polar codes with SS demodulation to enhance eLoran data communication.

## Key findings

- The new scheme achieves a 9.3 dB gain at 0.01 FER over RS codes.
- Data transmission efficiency improves by reducing duration by 2/3 or increasing message bits by 250%.
- Positioning capabilities remain unaffected by the changes.

## Abstract

The enhanced Loran (eLoran) system, a critical terrestrial backup for the Global Satellite Navigation System (GNSS), traditionally utilizes a Reed-Solomon (RS) code for its data communication, which presents limitations in error performance, particularly due to its decoding method. This paper introduces a significant advancement by proposing the replacement of the conventional RS code with a 128-ary polar code, which is designed to maintain compatibility with the established 128-ary Pulse Position Modulation (PPM) scheme integral to eLoran’s positioning function. A Soft–Soft (SS) demodulation method, based on a correlation receiver, is developed to provide the requisite soft information for the effective Successive Cancellation List (SCL) decoding of the 128-ary polar code. Comprehensive simulations demonstrate that the proposed 128-ary polar code with SS demodulation achieves a substantial error performance improvement, yielding an approximate 9.3 dB gain at the 0.01 FER level over the RS code in eLoran data communication with EPD-MD demodulation. Additionally, the proposed scheme improves data transmission efficiency—either reducing transmission duration by 2/3 or increasing message bit number by 250% for comparable error performance—without impacting the system’s primary positioning capabilities.