Performance analysis of serial relay orbital satellite optical communication over turbulent channels.

Optical space communication has been proven to be a reliable relay satellite transmission system. The difficulty that occurs in RF satellite communication (SatCom) can be alleviated by using free-space optical (FSO) or laser SatCom. In this work, we analyze a proposed laser downlink relay SatCom model with existing channel turbulence employing intensity modulation and direct detection (IM/DD), and amplify-and-forward (AF) technology and compare it with the optical direct link SatCom. Accounting for atmospheric attenuation and turbulence, the effect of model parameters such as zenith angle, receiver aperture radius, best number of optical ground stations (OGSs), and end-to-end operating wavelength on system performance is investigated for different OGS height scenarios. We provide exact closed-form expressions for the proposed model and optimize system performance by selecting the best number of OGSs using a selective diversity technique that can boost the system signal-to-noise (SNR) by up to 37 dB (99.9%).

Performance analysis of multiple NLOS UV communication cooperative relays over turbulent channels.

Ultraviolet (UV) communication overcomes pointing and tracking errors and is superior to other modern optical wireless communication technologies at short range. Using effective wavelengths from 200 to 280 nm, enables the non-line-of-sight (NLOS) outdoor UV communication in the presence of strong molecular and aerosol scattering. Because of these characteristics, solar blind NLOS UV communications offers broad coverage and high security. In this paper, NLOS UV communication is considered with decode and forward (DF) relays in the presence of log-normal (LN) channels using the best relay selection technique according to the channel state information (CSI). Then the outage probability of the multi-relay UV system is discussed for the proposed model. Simulation results verify the effectiveness of our employed analytical model. The outage probability for both serial and cooperative relays is compared with a different number of relays. Numerical simulations are further presented for many factors influencing the functioning of the system such as elevation angle, atmospheric scattering parameters and receiver field of view (FOV) angles. The obtained results demonstrate that increasing the number of UV NLOS cooperative relays does not necessarily improve the system performance, but there are other factors that must be considered such as the value of the elevation angle and the number of relays.