In the Centralized RAN telecommunications architecture, the fronthaul portion of the network comprises the intermediate links between the centralized radio controllers and the radio heads (or masts) at the "edge" of a cellular network.
In general it is coincident with the backhaul network, but subtly different. Technically in a C-RAN the backhaul data is only decoded from the fronthaul network at the centralised controllers, from where it is then transferred to the core network.
It comprises dedicated fibers carrying data in the CPRI or OBSAI format. This fiber network is either owned or leased by the mobile network operator. In the UK for example BT Openworld owns a majority of the fiber network to radio masts. There are proposals to modify Ethernet to make it more suitable for the Fronthaul network.