Analysis of radio frequency interference affecting S-band RNSS receiver

The 2483.5-2500 MHz S-band has gained increasing attention as a candidate frequency for Regional Navigation Satellite Systems (RNSS), such as Navigation with Indian Constellation (NavIC) and South Korea's Korean Positioning System (KPS). However, this band is adjacent to terrestrial services such as the Long-Term Evolution (LTE) band and the Industrial, Scientific, and Medical (ISM) band, raising concerns about interference. This study examines the impact of real-world adjacent-band interference on the reception quality of S-band RNSS signals. Two representative waveforms, BPSK(1), as used in NavIC, and a custom BOC(5,2) signal, were digitally generated and combined with real-world interference recordings obtained in the Korean spectrum environment. A software-defined radio (SDR) system was employed to process different interference and quantization scenarios. Results indicate that LTE uplinks cause the most severe degradation in carrier-to-noise density ratio (C/N₀), while microwave ovens and Wi-Fi devices also cause noticeable degradation. The BOC(5,2) waveform generally exhibited greater susceptibility to interference than BPSK(1), although the relative trend depended on the interference scenario and receiver processing configuration. Low-bit quantization increased degradation, whereas automatic gain control (AGC) partially mitigated this effect.