Christian Arnel R. Alcantara | Alshein Faith Aboy | Gino Rey Avila |
May 14, 2026
Low-power Internet-of-Things (IoT) devices deployed in industrial and smart-building environments frequently experience electromagnetic interference (EMI) that degrades conventional radio-frequency communication links. As an alternative, audio-band communication below 20 kHz offers a low-power signaling channel that is less affected by RF interference and can be implemented using simple transducers or wired coupling circuits. This paper presents a simulation-based comparative analysis of several audio-band modulation techniques for low-rate IoT communication, including amplitude modulation (AM), frequency modulation (FM), phase modulation (PM), amplitude shift keying (ASK), frequency shift keying (FSK), phase shift keying (PSK), and chirp spread spectrum (CSS). MATLAB-based simulations were performed to evaluate spectral occupancy, bandwidth requirements, and spectral efficiency using Fourier-domain analysis. Results show that ASK and PSK achieve the highest spectral efficiency of approximately 0.50 bps/Hz with bandwidths of about 2 kHz, while FM requires the largest bandwidth of approximately 12 kHz due to frequency deviation. CSS exhibits the widest spectral distribution (.7 kHz) but provides a processing gain of approximately 7, enabling improved robustness against narrowband interference. These results highlight the trade-off between bandwidth efficiency and interference resilience for audio-band communication systems and demonstrate the feasibility of using low-frequency modulation techniques for reliable low-power data transmission in interference-constrained environments.