In a mobile communication system, a base station is an important component of a mobile communication network, and is adapted to receive and transmit radio signals and enable a user equipment (user equipment, UE) to access a wireless network.
Base station systems of existing communication networks have different networking solutions, for example, a base station may be disposed at a single location, or a baseband part and a radio frequency part of a base station may also be disposed at different locations (a base station with a distributed architecture). For the base station with a distributed architecture, that is, the baseband part and the radio frequency part of the base station are separated, the distance between a baseband circuit and a radio frequency circuit may be relatively short; or the base station may also have a main-remote design architecture, in which a radio unit part is remotely disposed relative to a baseband part of a main unit. The main unit (MU) performs baseband signal processing, and the main unit may include one or more baseband control units (baseband control unit, BBU). One or more radio units (remote radio unit, RRU) perform conversion between baseband and radio frequency, and transmit and receive signals on one or more antennas. Each RRU serves a geographical area or cell, and transmits uplink/downlink baseband signal and main control state information with the BBU through an interface unit. For a time division synchronization (Time Division Duplex, TDD) system, because base stations use the same frequency band for transmission and reception, the base stations need to keep time synchronization in order to avoid interference between the base stations.
In the prior art, time synchronization is implemented on conventional base stations through a satellite positioning system (for example, a global positioning system, GPS system, a BeiDou satellite system, a Galileo system, or the like). However, for a base station with a distributed architecture, the BBU and the RRU are separately configured, and if satellite positioning systems are installed in both the BBU and the RRU, the system architecture is complex, and the system cost is greatly increased.