Multipath delay profile and Doppler spread of millimeter radiowaves over the sea channel

This paper presents a line-of-sight (LoS) ship-to-ship wireless communication for millimeter radiowaves over the sea surface. 35 GHz and 94 GHz have been analyzed by our simulations as they are the frequencies of interest for the sea channels at millimeter radiowaves. The main time dispersion parameters of maritime channel such as mean excess delay, Root Mean Square (RMS) delay spread, coherence bandwidth (Bc), Doppler spread as well as coherence time and coherence distance have been investigated in this work. Cumulative Distribution Functions (CDFs) of time delay parameters indicate that the maritime channels can be assumed frequency non-selective as long as the bandwidth of transmitted signal does not exceed 750 MHz and 1.53 GHz at 35 GHz and 94 GHz, respectively. In addition, based on the results obtained from the Doppler spectrum, the sea channel is not affected by vessel movements and therefore the efficacy of Doppler frequency is negligible in maritime environments at these two frequencies. Consequently, the corresponding coherence times are relatively long enough not to cause distortion due to motion. As for the coherence distance, our results illustrate that the coherence distance for off shore marine channels is so large that it offers no space diversity over the sea channel.