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

Area of Science:

• Navigation Systems Engineering
• Information Theory
• Digital Communications

Background:

• Enhanced Loran (eLoran) is a critical terrestrial backup for Global Satellite Navigation Systems (GNSS).
• Traditional eLoran data communication uses Reed-Solomon (RS) codes, which have suboptimal error performance.
• The 128-ary Pulse Position Modulation (PPM) scheme is integral to eLoran's positioning function.

Purpose of the Study:

• To propose replacing the conventional RS code in eLoran with a 128-ary polar code.
• To develop a Soft-Soft (SS) demodulation method for effective 128-ary polar code decoding.
• To evaluate the error performance and data transmission efficiency of the proposed scheme.

Main Methods:

• Implemented a 128-ary polar code compatible with the existing 128-ary PPM scheme.
• Developed a Soft-Soft (SS) demodulation method using a correlation receiver.
• Conducted comprehensive simulations to compare the proposed polar code with the traditional RS code.

Main Results:

• The 128-ary polar code with SS demodulation achieved a 9.3 dB gain at 0.01 FER compared to RS code with EPD-MD demodulation.
• The proposed scheme significantly improved data transmission efficiency, reducing duration by 2/3 or increasing message bits by 250% for similar error rates.
• System positioning capabilities remained unaffected.

Conclusions:

• Replacing RS codes with 128-ary polar codes offers substantial error performance improvements for eLoran.
• The developed SS demodulation method effectively supports SCL decoding of 128-ary polar codes.
• The proposed approach enhances eLoran data communication efficiency without compromising its core positioning function.