In a telecommunications system, a backhaul is the portion that connects the backbone and the edge networks. For example, with a cellular phone system, the towers connect to local phones and make a large, but local, network. The towers communicate with a central routing system that is able to talk to all towers in the system. The local tower network is an edge system, the central system is the backbone and the method of communication between them is the backhaul. This term has several other meanings in other technical fields, but they all revolve around the same ideas.
The term backhaul has a long history in the telecommunication, computer and broadcasting fields. It likely originated as a term used in overland transport to talk about using a secondary route to get to a destination faster. This term was co-opted to describe moving data from place to place as efficiently as possible. From there, it entered into the telecommunications field as a segment of the system and into broadcasting as a method of getting programming where it needs to be for transmission.
The telecommunications definition is the more widely used of the two. In this case, a backhaul describes a primarily software system that connects two primarily hardware systems together. While the above example uses cellular phones, any communications system likely has a backhaul. The primary requirement is two main hardware-based systems, generally a local system and a main routing system. In every case, these systems need a specialized method of communication between them.
These systems are varied, but they all use basic telecommunications protocols to talk to one another. In addition to cellular phones, automatic teller machines, multi-location business networks and satellite communication systems all use backhaul systems to communicate. In all of these examples, the backhaul is an actual system of software and routing paths.
The broadcast version of backhaul is used less and describes a method of moving information rather than the system of moving it. In this case, the term is used to show how information travels from location to location to get to a central system. The main focus in this definition is routing speed and cost efficiency. For instance, if a television show needs an uplink at a certain time for broadcast, it is important that the show arrive on time and intact over the network’s systems.
This form of backhaul goes back to the original version, where the goal was to arrive safely at a specified time. This form requires precise organization between several groups to make sure data flows in the way it should. This will often require bypassing common transmission routes in favor of slower, but more reliable, means.