Optical fiber is used for transmission between the BBU and the RRU. The RRU is then connected to the antenna through coaxial cables and power dividers (couplers), that is, the trunk uses optical fiber, and the branch uses the same fiber. One of the main aspects of optimization is reducing signal loss. However, the RRU/AAU is mostly installed outdoors, such as iron towers, etc., and the optical cable connecting to the BBU/DU is required to have the. A BBU-RRU delay setting method comprises: acquiring a fibre length L BBU-RRU between a BBU and an RRU; acquiring a buffer delay Trru required by the RRU and an air interface advance T a corresponding to the RRU; sending the acquired fibre length, the buffer delay Trru required by the RRU and the. Remote radio units or RRUs basically act as the connection point between those digital baseband signals we work with and actual radio frequency transmissions. What they do is take the digital. AAU, RRU, and BBU are key components in a telecom network, particularly in modern wireless communication systems like 4G and 5G.