Impact of Firefighting Water Jets on Public Safety Long-Term Evolution Communication Reliability

In fire environments, firefighting water jets can cause significantly attenuated electromagnetic signals, potentially impairing wireless communication reliability. In this study, the impact of water droplets generated by water jets on electromagnetic wave propagation in the PS-LTE band (718–783 MHz), designated for Korea’s disaster safety communication network, was systematically investigated. Experiments were conducted under heavy (100 mm \cdot h−1) and light (2.5 mm \cdot h−1) rainfall conditions, considering two scenarios: when a wireless terminal is positioned outside the rain (Antenna Placed Outside Rain: AoR) and when it is in direct contact with raindrops (Antenna placed Inside Rain: AiR). Electromagnetic wave transmission was simulated using linearly polarized (Dipole) and circularly polarized (Bi-Quad) antennas, with the results validated experimentally. The radiation patterns and efficiency of each receiving antenna were also analyzed. In the AoR scenario, the measured efficiency of the linearly polarized antenna was 89%, while that of the circularly polarized antenna was 79%. By contrast, under the AiR scenario, the efficiency of the linearly and circularly polarized antennas decreased to 36% and 32%, respectively. The results confirmed that in the AiR scenario, direct contact with raindrops led to electromagnetic absorption and scattering, reducing the receiving antenna’s efficiency by nearly 50% compared to the AoR scenario. Additionally, the communication characteristics of a wireless device exposed to water were analyzed, revealing that droplet exposure reduced receiver sensitivity by over 3 dBm. This represents one of the first systematic experimental analyses of PS-LTE signal degradation under emulated firefighting water-jet conditions. These findings highlight the potential impact of water jets on signal attenuation in the PS-LTE band, emphasizing the need for mitigation strategies to ensure reliable communication in fire environments.