Link-Layer Retransmission-based Error-Control Protocols in FSO Communications: A Survey

Abstract

Free-space optical (FSO) communications have gained significant interest over the last few years, thanks to the capability to transport extremely high-speed data over long distances without exhausting radio frequency (RF) resources. FSO communication is widely considered in various network scenarios, such as inter-satellite/deep-space links, ground-station/vehicles, satellite/aerial links, or terrestrial links. It is expected to be a key enabling technology for the next generation of 6G wireless networks. Nevertheless, despite the great potential of FSO communications, its performance suffers from various limitations and challenges: atmospheric turbulence, clouds, weather conditions, and pointing misalignment. The error-control solutions, including physical layer (PHY) and link-layer methods, aim to mitigate the transmission errors caused by such adverse issues. While the existing surveys on error-control solutions in FSO systems primarily focussed on the PHY methods, we instead provide a review of link-layer solutions. In particular, we conduct an extensive literature survey of state-of-the-art retransmission protocols, both automatic repeat request (ARQ) and hybrid ARQ (HARQ), for various FSO communication scenarios, including point-to-point terrestrial, cooperative, multi-hop relaying, hybrid FSO/RF, satellite/aerial, and deep-space systems. Furthermore, we provide a survey of recent literature and insightful discussion on the cross-layer design frameworks related to link-layer retransmission protocols in FSO communication networks. Finally, the lessons learned, design guidelines, related open issues, and future research directions are exposed.

Error Analysis of Free Space Communication System Using Machine Learning

“…Haze is a particular matter which is the combination of dust and smoke in the atmosphere distributed randomly and leads to chemical reactions due to gaseous pollutants. It is sometimes referred to as Mie scattering due to the transmitter wavelength, and almost similar size of haze particles [23], [24], [25]. Visibility is roughly 10 Km but can reduce due to fire and other seasonal occurrences.…”

Teletraffic analysis and simulation on FSO systems: the traffic generators approach

“…Nevertheless, there is little research on data link protocols over FSO. In [3] it is criticized that the research to date has focused on studying error mitigation schemes in FSO links by means of physical layer techniques such as those described in [4]: forward error correction, adaptive transmission, adaptive modulation, adaptive optics, aperture averaging, spatial diversity, hybrid RF/FSO links, relay satellite assisted transmission, digital signal processing, and pointing, acquisition and tracking (PAT) systems. For this reason, [3] presents a study and recommendations on how to apply error correction schemes in FSO links through data link layer functions, that is, through retransmission protocols such as Automatic Repeat Request (ARQ) or Hybrid Automatic Repeat Request (HARQ).…”

“…In [5] and [3] the benefits of the cross-layer design approach to FSO links are discussed. When protocols are designed with the cross-layer design approach, there may be an exchange of information between the physical and data link layers, which are traditionally decoupled when using the layered design approach.…”

Availability of Free-Space Laser Communication Link with the Presence of Clouds in Tropical Regions

“…In 6G, the huge development is not limited to terrestrial networks, but also satellite networks. They supplement existing terrestrial networks due to their cost-effective, rapid deployment, which is easily achieved from the popularity of low-earth orbit (LEO) satellites [1][2][3]. On the other hand, free-space laser communication (lasercom) using large optical bandwidth can transmit extremely high data rates and better security over long transmission distances without exhausting precious and limited radio frequency (RF) resources [4].…”