Reciprocity-enhanced optical communication through atmospheric turbulence - part I: reciprocity proofs and far-field power transfer optimization

Abstract

Turbulence-induced scintillation is the principal impairment to Gbps laser communication over clear-weather atmospheric paths. This paper, plus its companion [A. Puryear, J. H. Shapiro, and R.R. Parenti, "ReciprocityEnhanced Optical Communication through Atmospheric Turbulence-Part II: Communication Architectures and Performance"], introduce and analyze the exploitation of atmospheric reciprocity for combating turbulence. Part I presents reciprocity proofs that apply under rather general conditions and underlie the communication performance analysis in Part II.

On the Reciprocity of Underwater Turbulent Channels

“…Theoretical studies in the '70s revealed that atmospheric turbulence has a reciprocal nature [18], [19], meaning that two laser beams propagating in opposite directions experience the same atmospheric turbulence distortions. Atmospheric turbulence reciprocity has been later confirmed experimentally [20], [21]. Through reciprocity in FSO, a pilot signal from a receiver can be used at the transmitter end to provide channel state information (CSI), based on which the transmitter end could employ various digital signal processing (DSP) techniques.…”

Statistical and temporal irradiance fluctuations modeling for a ground-to-geostationary satellite optical link

“…However, a difficulty is that, while the downlink is a plane wave, the uplink is a Gaussian beam. It has been shown ( [26], [27]) that the upward propagation of a Gaussian beam can be modeled by the downward propagation of a plane wave. This result simplifies the estimation of the correlation between the downlink and the uplink.…”

Characterizing Instantaneous Difference between Received Powers at Two Ends of a Bidirectional Optical Wireless Communication Link through Atmospheric Turbulence

“…However, up to now, the turbulence-induced performance degradation of OWC systems is still a problem that is required to be further addressed. To use code-rate-adaptive transmission to reduce the turbulence-induced negative effects on OWC systems, the transmitter needs to obtain the channel state information [4]; traditionally, a low data-rate feedback channel is employed to send the channel state information detected by the receiver to the transmitter [4,5]. Nevertheless, time delay caused by the feedback operation may make the channel state information arriving at the transmitter stale, and consequently weaken the performance improvement that the use of rate-adaptive transmission may result in.…”

“…Nevertheless, time delay caused by the feedback operation may make the channel state information arriving at the transmitter stale, and consequently weaken the performance improvement that the use of rate-adaptive transmission may result in. Very recently, several researchers found that fluctuations in the received light powers at the two ends of a bidirectional OWC link through atmospheric turbulence may manifest significant correlation [5,6]. This property has been referred to as the channel intensity reciprocity in the literature [6], and can be employed to implement code-rate-adaptive transmission in bidirectional OWC links of which the adaptive transceivers directly obtain the instantaneous channel state information according to their received light powers.…”