Traditional Internet protocols are not suitable for the aeronautical environment. The TCP/IP protocol stack has evolved for an Internet that is mostly wired (although that is changing at the edges) with stable topologies and connectivity to which disruptions require terminating of TCP connections, and reconvergence of routing algorithms.
Civilian and commercial airborne networks require some modifications due to wireless links and moderate but often predicable mobility. However, these scenarios are not necessarily multi-hop, and traditionally rely on point-to-point links to ground stations for ATC (air traffic control) and satellites (for Internet access and entertainment distribution). Drone networks may be more challenging if multi-hop communication is desired with unpredictable movements.
The most challenging scenario is for highly dynamic high-velocity multi-hop airborne networks, currently the domain of military communication. However, it is reasonable to expect future civilian, commercial, and government airborne networks to become more challenging as is becoming the case for ground-based vehicular networks, motivating VANETs (vehicular ad hoc networks) and VDTNs (vehicular disruption-tolerant networks).
This chapter is organized as follows: Section 4.2 introduces the communication environment for aeronautical networks, which can vary significantly depending on the scenario (e.g., civilian vs. military networks). Section 4.3 relates airborne networks to the traditional Internet, as well as other mobile wireless environments, including WMNs (wireless mesh networks), MANETs (mobile ad hoc networks), and DTNs (disruption-tolerant networks). Section 4.4 then presents an architecture and protocol suite suitable for the most demanding aeronautical environment: highly dynamic, high-velocity multi-hop networks that require the greatest change to past networking architectures, with comparisons to traditional end-to-end transport and routing protocols. Section 4.5 presents selected performance evaluation of this aeronautical protocol suite, with references to further analysis. Finally, Section 4.6 summarizes this chapter.
Airborne Network Environment
Airborne networks are a class of mobile wireless networks: wireless due to the untethered communication links between aircraft, and mobile due to the movement of aircraft. Depending on the communication paradigm, they may or may not need to be ad hoc networks that self-organize.
Table 4.1 shows the key characteristics of airborne network scenarios, ordered in increasing challenge to network protocols. The evolution from current to future network types, described for each scenario below, is depicted in italic font in the last column.