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

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.

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

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.

An Analogy of a Network to an Electro Hydrodynamic Fluid Flow to Analyze the Energy Required for Transmitting a Packet in a Network Susceptible to Multiple Failures

Computer networks have become pervasive to human life and now, people are inseparable from connectivity. The world’s networking communities have been constantly raising the bar of standards to provide the best possible service to their users. Every packet drop is treated as a blunder and a game ender by the companies. Standards lead to organizations that govern the service rules and policies, penalize the companies heavily if packets are lost, connections are severed midconversation. This makes the companies spare no expense into developing smarter and faster rerouting methods, packet retransmission protocols. The observation of these systems leads to believe that the system is modeled after an electro hydro dynamic fluid flow through a charged medium. In this paper the analogy and the analysis of the energy spent for rerouting packets in case of node failure, is presented in its complete mathematical form.

Advanced Retransmission Protocols for Critical Wireless Communications

This chapter provides background about Hybrid Automatic Repeat reQuest (HARQ) protocols. First, the critical situations that may be faced by wireless communication systems especially cellular mobile technologies in case of very noisy radio channels are introduced. Particularly, the chapter introduces the HARQ protocols, their main constituent components as well as some related application areas. Then, the state-of-the-art of HARQ protocols is presented. The next section explains the three basic ARQ protocols. Then, the different HARQ types are detailed. Then, a mathematical model of type II HARQ based on Rayleigh fading channel is provided. This analytical analysis is followed by a discussion of the throughput which is one of the most interesting metrics used to measure the performance of HARQ systems. The readers can find in the next section a description of the HARQ systems architecture where 3GPP LTE is used to illustrate and explain how such systems operate. Finally, the last section concludes the chapter.