How Combining Automatic Repeat Request and Forward Error Correction Improves Throughput in Low Earth Orbit Satellite Communications

This paper investigates the throughput performance of Automatic Repeat Request (ARQ) and hybrid Automatic Repeat Request Forward Error Correction (ARQ+FEC) schemes in a Rayleigh fading environment, representative of Low Earth Orbit (LEO) satellite communications. While traditional FEC-only schemes have been favored in high-latency systems, the short round-trip delays in LEO enable the practical use of ARQ. However, it remains unclear whether typical Bit Error Rate (BER) levels in LEO channels caused by fading and path loss fall within the correction capabilities of ARQ+FEC configurations. This study fills that gap by analytically modeling and simulating the performance of BCH-coded FEC integrated with Selective Repeat ARQ. At an Eb/No of 20 dB, the hybrid system reduces the average transmissions per block from 1.5 (ARQ-only) to 1.2, and improves normalized throughput from 0.67 to 0.79 an 18% gain. These findings demonstrate that moderate error correction levels are well-suited to the BER ranges typically observed in LEO, confirming the hybrid schemes capability for improving throughput and reliability in next-generation satellite systems.