On the BER Performance of OOK FSO Links with Receivers’ Diversity and Time Jitter over Strong Turbulence Channels

Free Space Optical (FSO) communications have increasingly emerged in the last decade because of their unparalleled, inherent advantages like the high data rate communications with minimal costs. However, the performance of FSO communications systems is severely limited due to numerous agents. One of the deteriorating contributors is the scintillation effect due to atmospheric turbulence, causing rapid fluctuations of the receiving signal’s intensity. Turbulence strength depends on the current weather conditions and can be estimated from many available statistical models proposed. Also, time jitter is another deteriorating contributor, which causes additional impairments to the link’s throughput due to an either early or late misdetection of the received optical pulse’s center. Especially inevitable, time jitter affects high data rate communications, where the corresponding detector’s time slot is quite short. One hopeful FSO performance improvement solution employs the receiver’s diversity technique. In this work new mathematical expressions for the estimation of the average BER performance of NRZ or RZ OOK FSO links with receivers’ diversity are derived. The strong atmospheric turbulence effect is modeled with K - distribution. In addition, time jitter effect is studied, for the first time to the best of the authors’ knowledge, with the generalized Gaussian distribution. Useful numerical results and interesting conclusion are also listed in this work.