CPRI (Common Public Radio Interface): The Common Public Radio Interface (CPRI) alliance is an industrial cooperation organization, which is committed to the formulation of the main interface specifications between the radio equipment control center (REC) inside the radio base station and the radio equipment (RE).Companies that initiated the establishment of CPRI include Ericsson, Huawei, NEC, Nortel Networks and Siemens. CPRI is open to other organizations and manufacturers.
CPRI: transmit baseband signals in a digital way. There are two digital interfaces, standard CPRI and OBSAI.CPRI (The Common Public Radio Interface) defines the interface relationship between the base station data processing control unit REC (Radio Equipment Control) and the base station transceiver unit RE (Radio Equipment). Its data structure can be directly used for remote transmission of repeater data, becoming a remote system of the base station.
Development and evolution
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·In April 2003, Ericsson, Huawei, NEC, Nortel Networks and Siemens launched the CPRI organization.
·In September 2003, version 1.0 of the CPRI standard was released. By developing an open standard interface, the base station is divided into wireless equipment (RE) and wireless equipment control part (REC).
·Version 2.0 was released in October 2004. It supports W-CDMA, CDMA2000, TD-SCDMA and other wireless communication standards.
·The latest version 3.0 was released in October 2006, adding support for WiMAX.
Delay adjustment
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After the electrical signal on the remote RF unit is synchronized with the base station, the delay of all transmission channels between the remote RF unit and the base station machine room must be set to meet the timing requirements of the air interface.The interconnection between the remote RF unit and the base station is usually set by usingFrame synchronizationTechnical measurement of delay value.
The interface includes three different information flows（User layerdata stream, control management data flow, and synchronize data flow).The protocol consists of two layers: L1:physical layer。L2:：data connection Layer.
Through L1 and L2 layer protocols, IQ data, control and management, and synchronization signals can be exchanged between REC and RE.All signals can be exchanged on digital continuous AC lines.
