midhaul

Midhaul is a telecommunications term referring to a portion of a network transport path that lies between the access/RAN edge and the core network, or more specifically the link between distributed processing units in a split radio access network and the central processing unit. In mobile networks such as 4G and 5G, midhaul supports the connection between remote or distributed units and central units, enabling centralized processing and coordination across multiple cells. It is distinct from backhaul, which connects base stations to the core network, and from fronthaul, which connects radio heads to baseband units. The exact boundary between midhaul and fronthaul varies with architecture and vendor; some designs designate the link between distributed units and central units as midhaul, while the radio-head to distributed-unit link is treated as fronthaul.

Midhaul plays a role in enabling centralized processing, resource pooling, and features such as coordinated multipoint and dynamic spectrum sharing. It must carry both user-plane and control-plane traffic with sufficient bandwidth and reasonable latency; however, compared with fronthaul, midhaul generally tolerates higher latency and can use a broader range of transport options. This can include traditional fiber, wireless microwave, or other IP-based transport networks, depending on capacity needs and latency targets.

Implementation considerations for midhaul include synchronization requirements, quality of service, redundancy, and capacity planning. Operators design midhaul to balance performance, cost, and architectural goals within the broader transport network, often combining multiple paths and technologies to meet reliability and scalability needs.