Adaptive subcarrier PSK intensity modulation in free space optical systems

Nestor D. Chatzidiamantis, Athanasios S. Lioumpas, George K. Karagiannidis, Shlomi Arnon

Research output: Contribution to journalArticlepeer-review

94 Scopus citations


We propose an adaptive transmission technique for free space optical (FSO) systems, operating in atmospheric turbulence and employing subcarrier phase shift keying (S-PSK) intensity modulation. Exploiting the constant envelope characteristics of S-PSK, the proposed technique offers efficient utilization of the FSO channel capacity by adapting the modulation order of S-PSK, according to the instantaneous state of turbulence induced fading and a pre-defined bit error rate (BER) requirement. Novel expressions for the spectral efficiency and average BER of the proposed adaptive FSO system are presented and performance investigations under various turbulence conditions, turbulence models, and target BER requirements are carried out. Numerical results indicate that significant spectral efficiency gains are offered without increasing the transmitted average optical power or sacrificing BER requirements, especially in moderate-to-strong turbulence conditions. Furthermore, the proposed variable rate transmission technique is applied to multiple input multiple output (MIMO) FSO systems, providing additional improvement in the achieved spectral efficiency as the number of the transmit and/or receive apertures increases.

Original languageEnglish
Article number5723049
Pages (from-to)1368-1377
Number of pages10
JournalIEEE Transactions on Communications
Issue number5
StatePublished - 1 May 2011


  • Adaptive modulation
  • atmospheric turbulence
  • free-space optical communications
  • multiple input multiple output (MIMO)
  • subcarrier PSK intensity modulation
  • variable rate

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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