Environmental Information-Aided Electromagnetic Propagation Testbed for Maritime Communication

Maritime channel modeling can be affected by some key time-varying environmental factors.The ducting effect is one of the thorniest factors since it causes anomalous propagation enhancement and severe co-channel interference.Moreover,the atmospheric attenuation is much more severe in the ocean environment,resulting in shorter coverage distance and more link outage.In this paper,we propose an environmental information-aided electromagnetic propagation testbed.It is based on complex refractivity estimation and improved parabolic equation propagation model,taking into account both ducting effect and atmospheric attenuation.A large-scale temporal and spatial propagation measurement was conducted with meteorological acquisition.We consider practical path loss and ducting conditions to verify the testbed feasibility in these long-distance radio links.The simulation results are in good agreement with the measured data,which further reveal the basic temporal and spatial distribution of ducting effect at 3.5 GHz band.

A New Way to Study Water-Vapor Absorption Coefficient

In the visible spectrum, the atmospheric attenuations to sunlight mainly include aerosol scattering, atmospheric molecule Rayleigh scattering and ozone absorption, while in the near-infrared spectrum (from 650 nm to 1 000 nm), we must take water-vapor absorption into account. Based on the atmospheric correction theory, using spectrum irradiance data measured by Instantaneous Ground spectrometer, ozone content measured by Microtops Ⅱozone monitor, water-vapor content and aerosol optical thickness measured by sun photometer, we give a new way to study water-vapor absorption to sunlight, and the result shows that the main peak values of water-vapor absorption coefficients are 0.025 cm-1, 0.073 cm-1, 0.124 cm-1, 0.090 cm-1, 0.141 cm-1 and 0.417 cm-1, which respectively lie at 692 nm, 725 nm, 761 nm, 818 nm, 912 nm and 937 nm.

Enhancement of FSO Communications Links Under Complex Environment

Free space optical communication is a line-of-sight （LOS） technology that uses lasers to provide optical bandwidth connections. Potential disturbance arising from the weather condition is one of the most effective factors that influence the bi-directional free space optics （FSO） performance. The complex weather condition in the Middle East region and Arabian Gulf has been dominated by dust storms activities. Dust storms directly affect the characteristics of FSO and consequently lead to an increase in the bit error rate （BER） and deterioration Q-factor to bad levels due to the high attenuation factor. In this research, the authors compare the differences between two bi-directional FSOs. One is the traditional link, and the other has been developed to enhance the system performance under the dust storms condition. The proposed design consists of dual FSO channels, and each one includes erbium-doped fiber amplifier （EDFA） optical amplifiers. This design has demonstrated the proficiency in addressing the attenuation that occurs due to weather stickers. The results prove there is an improvement in performance by measuring the Q-factor. In addition, BER can be significantly improved, and further communicating distance can be achieved by utilizing 1550nm with multiple channels and EDFA.