Hardware‐Accurate Simulation and Performance Analysis of Free Space Optical Communication Systems

ABSTRACT

This paper presents a system‐level performance evaluation of a 10 Mbps free‐space optical (FSO) communication link using a novel dual‐testbed methodology. By combining hardware‐accurate profiling in Keil Vision for the STM32H755ZI (ARM Cortex‐M7) and NXP LPC1768 (ARM Cortex‐M3) microcontrollers with physical layer simulations in Proteus, we successfully isolate embedded processing constraints from optical channel impairments. Our software optimisations, including the use of atomic bit‐set registers and loop unrolling, pushed the internal GPIO toggle rate to 95.58 MHz on the STM32H755ZI and 19.91 MHz on the NXP LPC1768, demonstrating that the core processing capability far exceeds the data rate requirements. Comparative profiling reveals critical cross‐platform microarchitectural bottlenecks: Sub‐word data type alignment ( uint64_t ) inflicts a execution penalty on the Cortex‐M3 core, while software 4B5B encoding introduces severe cycle overheads ( per ) without dedicated hardware barrel shifters, necessitating mandatory toolchain optimisation ( ‐O2 ) to preserve real‐time frame timing. Channel simulations quantified the system's resilience, showing that maintaining a target BER under atmospheric turbulence necessitates an SNR of 47 dB. The receiver bandwidth was empirically determined to require a minimum 3.5 MHz low‐pass filter cutoff, a finding consistent with Nyquist theory. Furthermore, we identify a hard reliability limit of 32 bits for continuous payload transmission due to AC coupling droop, reinforcing the necessity of DC‐balanced line coding. This study provides a comprehensive co‐design blueprint for developing reliable FSO systems under stringent hardware and environmental constraints.