Abstract
Subcarrier free-space optical (FSO) systems using coherent recovery techniques at the receiver have acquired growing research interest in recent times. However, their optimal performance is diminished by the non-perfect synchronization of carrier frequency and phase, which is mainly due to phase noise problems. Moreover, turbulence and pointing error effects further deteriorate the overall performance. However, relay transmission schemes can extend the coverage distance and offer substantial improvements over fading conditions. In this respect, we consider a serially relayed network using decode-and-forward relays, and investigate its performance by means of average symbol error probability and mean outage duration. Turbulence is modeled by the recently unified M(alaga) distribution, which constitutes a very general statistical model that accurately describes the irradiance fluctuations from weak-to-strong turbulence conditions. Additionally, the presence of non-zero boresight pointing errors due to misalignment between the transmitter–receiver pair is considered, while the effect of phase noise is specified by a Tikhonov distribution. A comparison between single line-of-sight and serially relayed FSO configurations is provided as well. Novel approximated mathematical expressions are deduced, which are proved to be accurate enough over a wide range of turbulence strengths and signal-to-noise values. Finally, proper numerical results are presented and validated by Monte Carlo simulations.
Highlights
The increasing requirement for high data rates, low cost, and improved security over recent years has given rise to the employment of terrestrial free-space optics (FSO) as a potential technology for point-to-point communications
We thoroughly investigate the performance of a multi-hop system by means of the average symbol error performance (ASEP) and the mean outage duration (MOD) per hour
By properly using the analytical expressions derived in the previous section, we can numerically verify the joint influence of M(alaga) fading and non-zero boresight pointing errors on the phase shift keying (PSK) performance for both single and multi-hop FSO configurations along with or without phase noise impairments
Summary
The increasing requirement for high data rates, low cost, and improved security over recent years has given rise to the employment of terrestrial free-space optics (FSO) as a potential technology for point-to-point communications. The use of relays in FSO systems is an effective method to extend the coverage distance and lessen the negative effects of fading [8,9] Motivated by this fact, we thoroughly investigate the performance of a multi-hop system by means of the average symbol error performance (ASEP) and the mean outage duration (MOD) per hour. We thoroughly investigate the performance of a multi-hop system by means of the average symbol error performance (ASEP) and the mean outage duration (MOD) per hour To this end, we assume the freshly launched M(alaga) distribution for turbulence description, the appearance of non-zero boresight pointing errors, subcarrier intensity modulation, and phase noise effects. To this end, we first estimate the ASEP under the assumption of negligible phase noise effects by considering both M(alaga) turbulent and non-zero boresight misalignment fading conditions.
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