Unified Performance Analysis of Multi-Hop FSO Systems over Double Generalized Gamma Turbulence Channels with Pointing Errors

Behnam Ashrafzadeh, Amir Zaimbashi, Ehsan Soleimani-Nasab, Murat Uysal

Research output: Contribution to journalArticlepeer-review


Free space optical (FSO) communication systems provide high bandwidth in unregulated spectrum and act as a powerful line-of-sight wireless connectivity solution. The performance of FSO systems can be seriously impaired by fading as a result of atmospheric turbulence and/or pointing errors due to misalignment. In the context of FSO systems, relaying was proposed as an effective fading mitigation technique due to the fact that the variance is distance-dependent in turbulence channels. In this article, we present a unified performance analysis of multi-hop FSO systems over Double Generalized Gamma (DGG) turbulence channels with pointing error impairments. We assume amplify-and-forward relaying and consider both heterodyne detection and intensity modulation with direct detection. We derive tight closed-form expressions for the outage probability and bit error probability of both fixed-gain and channel state information (CSI)-assisted relaying in terms of the bivariate Fox-H functions and Fox-H functions, respectively. We further analyze asymptotic behavior of the outage probability in terms of simple elementary functions and obtain the achievable diversity orders. Diversity gain is found to be a function of atmospheric turbulence parameters, pointing error, detection type and the number of hops. Monte Carlo simulation results are further provided to verify the accuracy of the derived expressions.

Original languageEnglish (US)
Article number9170804
Pages (from-to)7732-7746
Number of pages15
JournalIEEE Transactions on Wireless Communications
Issue number11
StatePublished - Nov 2020


  • Free space optical communications
  • diversity order
  • double generalized gamma
  • multi-hop relaying
  • outage probability

ASJC Scopus subject areas

  • Computer Science Applications
  • Electrical and Electronic Engineering
  • Applied Mathematics


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