In communications networks, a backhaul is a transport connection between distributed and central network nodes, typically between access networks and core networks or between access points( AP) and exchanges.
In mobile networks, this means the connection of the base stations( BS) to the base station controller( BCS). In small cell concepts, backhaul ensures that the small cells are connected to the core network, the Internet or other services. And in satellite communications, the backhaul provides the connection to the point from which the data is transmitted in the uplink to the satellite.
The term backhaul merely states that there is a connection between the distributed nodes and the central nodes; it says nothing about how, via which transmission medium and with which protocol this transport connection is implemented. This can work as a radio link with directional radio, it can be wire-bound and realized via optical fibers, it can be set up as a mobile backhaul, likewise take place via fixed links or be switched via circuit- or packet-switched techniques. In terms of the connection type, the backhaul can also be a point-to-point connection or a multipoint connection. And in terms of the protocol that provides transport in the backhaul, all common transport protocols are conceivable: time-division multiplexing(TDM), asynchronous transfer mode( ATM), IP protocol, multi-protocol label switching( MPLS), Gigabit Ethernet and others.
The many possibilities in backhaul design have a significant influence on the backhaul configuration and the resulting backhaul costs.