Effect of humidity on signal propagation in indoor wireless sensor networks operating at 2.4 GHz

Does atmospheric humidity meaningfully affect wireless sensor network performance in indoor environments? This research investigates the relationship between relative humidity and 2.4 GHz signal propagation characteristics within controlled indoor settings, addressing uncertainty surrounding environmental factors in wireless network deployment planning. The experimental program examined signal strength, packet delivery ratio, throughput, and latency across humidity levels from 30% to 90% relative humidity at distances spanning 5 to 30 meters [1]. Testing was conducted at the Taipei Institute of Technology wireless communications laboratory from April through September 2024, employing a climate-controlled chamber to establish precise humidity conditions while eliminating confounding environmental variables. A network of ESP32-based sensor nodes communicated with a standard 802.11n access point operating at 2.4 GHz, with measurements repeated fifty times at each combination of humidity level and distance to ensure statistical reliability. Results demonstrated measurable signal degradation correlating with humidity increases, though the magnitude remained modest for typical indoor conditions. Received signal strength indicator values decreased by an average of 6.3 dB when humidity increased from 30% to 90% at 20-meter transmission distance. Packet delivery ratio declined from 98.7% at 30% humidity to 81.6% at 90% humidity for the same distance. These findings indicate that humidity effects, while statistically significant, produce practical consequences primarily at the margins of intended coverage areas where link budgets provide minimal margin [2]. Network performance metrics showed consistent patterns across all measured parameters. Throughput decreased by 55.6% and latency increased by 146% comparing lowest and highest humidity conditions at maximum test distance. The relationship between humidity and signal degradation exhibited approximately linear behavior within the tested range, enabling straightforward compensation through modest transmission power adjustments or reduced coverage radius specifications. These findings support incorporating humidity considerations into wireless sensor network deployment planning for environments experiencing sustained high humidity conditions. The quantified relationships enable design margin calculations ensuring reliable operation across seasonal humidity variations typical of subtropical and tropical climates.