Maritime multi-hop HF radio propagation

Abstract

When radio waves are transmitted on the ocean, their signals will gradually decay due to the influence of the propagation medium such as free space, ionosphere and sea surface. This paper designs a reflection loss model to analyze HF radio waves reflected off the ocean. Then, combined with reflection loss model, this paper establishes maritime communication channel model to discuss marine HF radio wave communication. Through simulation, this paper summarizes the multi-hop HF radio wave propagation characteristics at sea. Regarding the reflection loss model, this paper calculated free space reflection loss, ionospheric absorption loss and sea surface reflection loss that occur before the HF radio wave is reflected by the sea for the first time. According to the relation between reflected power, incident power and reflection loss, this paper solved the reflected power to determine the strength of the first reflection of the HF signal off the ocean. Depending on FFT (Fast Fourier Transform), this paper generated a three-dimensional ocean wave model from a 2D PM wave spectrum to simulate ocean fluctuations. By calculating, we found that reflections off a turbulent ocean are attenuated more than reflections off a calm ocean. This paper builds a smooth sea surface SNR estimation model. The model takes the atmospheric noise power and the radio wave received power as the parameters, and then this paper calculated the maximum number of hops the signal can take before its strength falls below a usable signal-to-noise ratio (SNR) threshold.