Abstract
This study investigated the outage performance of a terrestrial FSO communication system that uses mixed series and parallel decode-and-forward (DF) relay-assisted (i.e., cooperative diversity) configurations, taking into account the influence of both atmospheric turbulence and pointing error effects. Turbulence-induced optical signal fading is modeled by gamma-gamma or the negative exponential distribution for weak to strong and saturated turbulence conditions, respectively. Additionally, weak to strong non-zero boresight misalignment-induced optical signal fading is modeled by the generalized Beckmann distribution. Under these conditions, an outage analysis of the examined FSO system is performed, in terms of both outage probability and mean outage duration metrics. Thus, fairly accurate closed-form mathematical expressions for both performance metrics are derived, while their corresponding analytical results demonstrate concrete performance and availability improvements for the total FSO system, especially when the number of the connected in parallel DF relays increases. Moreover, the obtained results are verified through the corresponding simulation results.
Highlights
Terrestrial FSO communication systems that establish line-of-sight optical wireless links by using lasers and photo-detectors as transmitter and receiver terminals, respectively, have had growing research and commercial attention in the last few years
From the transmitter to each first DF relay node of each parallel path, the system consists of one source and N different destinations, signaling with an intensity modulation and direct detection (IM/DD) format in order to overcome any interference of the arriving information signal copies, from different paths, at the receiver node of the total system
A flexible mixed parallel and muliti-hop DF relaying FSO architecture has been introduced in order to effectively combat weak to saturated atmospheric turbulence effects, along introduced in order to effectively combat weak to saturated atmospheric turbulence effects, along with weak to strong non-zero boresight pointing errors, which significantly mitigate the FSO outage with weak to strong non-zero boresight pointing errors, which significantly mitigate the FSO outage performance and availability
Summary
Terrestrial FSO communication systems that establish line-of-sight optical wireless links by using lasers and photo-detectors as transmitter and receiver terminals, respectively, have had growing research and commercial attention in the last few years. A mixed architecture with parallel and serial relayed FSO links can significantly improve the performance of the system [17] In this context, a recently published work [17] estimated the outage probability (OP) of a mixed decode-and-forward (DF) FSO system over weak turbulent channels, modeled through the compact gamma distribution [18], along with non-zero boresight pointing errors modeled, in turn, with the accurate approximation of Beckmann’s distribution [19].According to the mixed DF FSO topology proposed in [17], the source node initiallytransmitsthe same signal to a specific number of DF relay nodes in a parallel configuration. Non-zero boresight pointing errors are emulated through the accurate approximation of the Beckmann distribution, proposed in [19]
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