Fronthaul, also known as mobile fronthaul, is a term that refers to the connection of the C-RAN, a new type of cellular network architecture of centralized baseband units (BBU), at the access layer of the network to remote standalone radio heads at cell sites. Due to the rising demand for C-RAN (often spelled out as either cloud radio access network or as centralized radio access network) deployments, using fronthaul as a method for supporting all generations of wireless communication has gained attention.

Disparate radio elements are connected to the centralized controllers through the Common Public Radio Interface (CPRI), which refers to the mainstream transport protocol in modern fronthaul networks. The latest CPRI specification adds capacity to remote radio heads, achieves higher-order MIMO and allows multi-carrier configuration. This type of interface supports shared infrastructure and dynamic capacity allocation, which enables the reality of a completely open RAN that can be used for future 5G applications and deployment scenarios.

Fronthaul is one of many factors that may enable distributed LTE-Advanced networks to make data travel faster and coverage denser in the future. Operators using the 5G architecture with a virtualized access layer attached to the mobile core could receive vastly improved performance at the access layer of the network. Additionally, virtual radio access networks (vRANs) might require fronthaul to maximize cost savings and efficiency, which is a solution that network operators are pursuing to take advantage of software-defined networking (SDN) and network function virtualization (NFV) capabilities.

Although fronthaul significantly boosts network performance by making it more flexible and efficient, many factors can affect performance and must be considered before adopting it as standard. These factors include network topology, the amount of fiber in the ground, the type of spectrum and the current lack of a fully open interface.

Fronthaul vs Backhaul

While backhaul is a well-known wireless networking term, fronthaul is similar in concept but less familiar. Wireless backhaul is the use of wireless communications systems to get data from an end user to a node in a major network such as the internet or the proprietary network of a large organization. With fronthaul, remote radio heads separate the radio elements of a base station from the baseband controller resulting in easier radio deployment at the top of a cell tower and increased signal coverage range.

This was last updated in October 2018

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