CPRI Specification V4.0 (2008-06-30)
`
`Interface Specification
`
`Common Public Radio Interface (CPRI);
`Interface Specification
`
`The CPRI specification has been developed by Ericsson AB, Huawei Technologies Co. Ltd, NEC Corporation, Nortel Networks Ltd, Alcatel
`Lucent and Nokia Siemens Networks GmbH & Co. KG (the “Parties”) and may be updated from time to time. Further information about CPRI,
`and the latest specification, may be found at http://www.cpri.info
`
`BY USING THE CPRI SPECIFICATION, YOU ACCEPT THE “Interface Specification Download Terms and Conditions” FOUND AT
`http://www.cpri.info/spec.html
`
`IN ORDER TO AVOID ANY DOUBT, BY DOWNLOADING AND/OR USING THE CPRI SPECIFICATION NO EXPRESS OR IMPLIED LICENSE
`.
`AND/OR ANY OTHER RIGHTS WHATSOEVER ARE GRANTED FROM ANYBODY.
`
`© 2008 Ericsson AB, Huawei Technologies Co. Ltd, NEC Corporation, Nortel Networks Ltd, Alcatel Lucent, and Nokia Siemens Networks GmbH
`& Co. KG.
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`CPRI Specification V4.0 (2008-06-30)
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`3.
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`4.
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`3.5.
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`3.6.
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`3.7.
`3.8.
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`3.9.
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`Table of Contents
`1.
`Introduction ................................................................................................................ 4
`2.
`System Description .................................................................................................... 6
`2.1.
`Definitions/Nomenclature............................................................................. 6
`2.2.
`System Architecture ..................................................................................... 9
`2.3.
`Reference Configurations .......................................................................... 10
`2.4.
`Functional Description ............................................................................... 13
`2.4.1. Radio Functionality.......................................................................... 13
`2.4.2. CPRI Control Functionality .............................................................. 14
`Interface Baseline..................................................................................................... 15
`3.1.
`Supported Radio Standards....................................................................... 15
`3.2.
`Operating Range......................................................................................... 15
`3.3.
`Topology/Switching/Multiplexing .............................................................. 15
`3.4.
`Bandwidth/Capacity/Scalability ................................................................. 17
`3.4.1. Capacity in terms of Antenna-Carriers............................................. 17
`3.4.2. Required U-plane IQ Sample Widths............................................... 18
`3.4.3. Required C&M-plane Bit Rate ......................................................... 18
`Synchronization/Timing ............................................................................. 19
`3.5.1. Frequency Synchronization ............................................................. 19
`3.5.2. Frame Timing Information ............................................................... 20
`3.5.3. Link Timing Accuracy ...................................................................... 20
`3.5.4. Round Trip Delay Accuracy............................................................. 21
`3.5.5. Accuracy of TDD Tx-Rx switching point........................................... 21
`Delay Calibration......................................................................................... 22
`3.6.1. Round Trip Cable Delay per Link..................................................... 22
`3.6.2. Round Trip Delay of a Multi-hop Connection ................................... 22
`Link Maintenance........................................................................................ 23
`Quality of Service........................................................................................ 23
`3.8.1. Maximum Delay .............................................................................. 23
`3.8.2. Bit Error Ratio U-plane .................................................................... 24
`3.8.3. Bit Error Ratio C&M-plane ............................................................... 24
`Start-up Requirement ................................................................................. 24
`3.9.1. Clock Start-up Time Requirement ................................................... 24
`3.9.2. Plug and Play Requirement............................................................. 24
`Interface Specification ............................................................................................. 26
`4.1.
`Protocol Overview ...................................................................................... 26
`4.2.
`Physical Layer (Layer 1) Specification ...................................................... 27
`4.2.1. Line Bit Rate ................................................................................... 27
`4.2.2. Physical Layer Modes ..................................................................... 27
`4.2.3. Electrical Interface........................................................................... 28
`4.2.4. Optical Interface .............................................................................. 29
`4.2.5. Line Coding..................................................................................... 29
`4.2.6. Bit Error Correction/Detection.......................................................... 29
`4.2.7. Frame Structure .............................................................................. 29
`4.2.8. Synchronisation and Timing ............................................................ 50
`4.2.9. Link Delay Accuracy and Cable Delay Calibration........................... 51
`4.2.10. Link Maintenance of Physical Layer ................................................ 54
`Data Link Layer (Layer 2) Specification for Slow C&M Channel.............. 58
`4.3.1. Layer 2 Framing .............................................................................. 58
`4.3.2. Media Access Control/Data Mapping .............................................. 58
`4.3.3. Flow Control.................................................................................... 58
`4.3.4. Control Data Protection/ Retransmission Mechanism...................... 59
`Data Link Layer (Layer 2) Specification for Fast C&M Channel............... 59
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`4.3.
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`4.4.
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`6.
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`7.
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`4.5.
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`4.4.1. Layer 2 Framing .............................................................................. 59
`4.4.2. Media Access Control/Data Mapping .............................................. 59
`4.4.3. Flow Control.................................................................................... 62
`4.4.4. Control Data Protection/ Retransmission Mechanism...................... 62
`Start-up Sequence ...................................................................................... 62
`4.5.1. General ........................................................................................... 62
`4.5.2. Layer 1 Start-up Timer .................................................................... 63
`4.5.3. State Description............................................................................. 64
`4.5.4. Transition Description...................................................................... 68
`Interoperability.......................................................................................................... 71
`5.1.
`Forward and Backward Compatibility ....................................................... 71
`5.1.1. Fixing Minimum Control Information Position in CPRI Frame
`Structure ......................................................................................... 71
`5.1.2. Reserved Bandwidth within CPRI.................................................... 71
`5.1.3. Version Number .............................................................................. 71
`5.1.4. Specification Release Version mapping into CPRI Frame ............... 71
`Compliance ................................................................................................. 72
`5.2.
`Annex ........................................................................................................................ 73
`6.1.
`Delay Calibration Example (Informative)................................................... 73
`6.2.
`Electrical Physical Layer Specification (Informative)............................... 76
`6.2.1. Overlapping Rate and Technologies ............................................... 76
`6.2.2. Signal Definition .............................................................................. 77
`6.2.3. Eye Diagram and Jitter.................................................................... 77
`6.2.4. Reference Test Points..................................................................... 78
`6.2.5. Cable and Connector ...................................................................... 78
`6.2.6.
`Impedance ...................................................................................... 78
`6.2.7. AC Coupling.................................................................................... 78
`6.2.8. TX Performances ............................................................................ 79
`6.2.9. Receiver Performances................................................................... 81
`6.2.10. Measurement Procedure................................................................. 83
`Networking (Informative)............................................................................ 83
`6.3.1. Concepts......................................................................................... 83
`6.3.2. Reception and Transmission of SAPCM by the RE ........................... 84
`6.3.3. Reception and Transmission of SAPIQ by the RE ............................ 84
`6.3.4. Reception and Distribution of SAPS by the RE ................................ 84
`6.3.5. Reception and Transmission of CPRI Layer 1 Signalling by the
`RE................................................................................................... 84
`6.3.6. Bit Rate Conversion ........................................................................ 85
`6.3.7. More than one REC in a radio base station ..................................... 85
`6.3.8. The REC as a Networking Element ................................................. 85
`E-UTRA sampling rates (Informative)........................................................ 85
`6.4.
`List of Abbreviations................................................................................................ 87
`References ................................................................................................................ 90
`History....................................................................................................................... 91
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`6.3.
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`1. Introduction
`The Common Public Radio Interface (CPRI) is an industry cooperation aimed at defining a publicly available
`specification for the key internal interface of radio base stations between the Radio Equipment Control (REC)
`and the Radio Equipment (RE). The parties cooperating to define the specification are Ericsson AB, Huawei
`Technologies Co. Ltd, NEC Corporation, Nortel Networks Ltd, Alcatel Lucent and Nokia Siemens Networks
`GmbH & Co. KG.
`
`
`
`Motivation for CPRI:
`
`The CPRI specification enables flexible and efficient product differentiation for radio base stations and
`independent technology evolution for Radio Equipment (RE) and Radio Equipment Control (REC).
`
`
`
`Scope of Specification:
`
`The necessary items for transport, connectivity and control are included in the specification. This includes
`User Plane data, Control and Management Plane transport mechanisms, and means for synchronization.
`
`A focus has been put on hardware dependent layers (layer 1 and layer 2). This ensures independent
`technology evolution (on both sides of the interface), with a limited need for hardware adaptation. In addition,
`product differentiation in terms of functionality, management, and characteristics is not limited.
`
`With a clear focus on layer 1 and layer 2 the scope of the CPRI specification is restricted to the link interface
`only, which is basically a point to point interface. Such a link shall have all the features necessary to enable a
`simple and robust usage of any given REC/RE network topology, including a direct interconnection of multi-
`port REs.
`
`Redundancy mechanisms are not described in the CPRI specification, however all the necessary features to
`support redundancy, especially in system architectures providing redundant physical interconnections (e.g.
`rings) are defined.
`
`The specification has the following scope (with reference to Figure 1):
`
`A digitized and serial internal radio base station interface that establishes a connection between
`‘Radio Equipment Control’ (REC) and ‘Radio Equipment’ (RE) enabling single-hop and multi-hop
`topologies is specified.1
`Three different information flows (User Plane data, Control and Management Plane data, and
`Synchronization Plane data) are multiplexed over the interface.
`The specification covers layers 1 and 2.
`3a. The physical layer (layer 1) supports both an electrical interface (e.g., what is used in traditional
`radio base stations), and an optical interface (e.g. for radio base stations with remote radio
`equipment).
`Layer 2 supports flexibility and scalability.
`
`3b.
`
`1.
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`2.
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`3.
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`1 The CPRI specification may be used for any internal radio base station interface that carries the information flows mentioned in the
`scope of point 2.
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`CPRI Specification V4.0 (2008-06-30)
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`Radio Equipment Control (REC)
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`Radio Equipment (RE)
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`Control &
`Mgmt.
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`Sync.
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`User
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`Control &
`Mgmt.
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`Sync.
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`User
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`Air
`Interface
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`Layer 2
`Layer 1
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`Layer 2
`Layer 1
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`DigitizedRadio Base Station
`Internal Interface Specification
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`Figure 1: System and Interface Definition
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`2. System Description
`This chapter describes the CPRI related parts of the basic radio base station system architecture and defines
`the mapping of the functions onto the different subsystems. Furthermore, the reference configurations and
`the basic nomenclature used in the following chapters are defined.
`
`The following description is based on the UMTS (Universal Mobile Telecommunication System), WiMAX
`Forum Mobile [11] based on IEEE Std 802.16-2004 as amended by IEEE Std 802.16e-2005 and IEEE Std
`802.16-2004/Cor1-2005 [12] and Evolved UMTS Terrestrial Radio Access (E-UTRA). However, the interface
`may also be used for other radio standards.
`
`2.1. Definitions/Nomenclature
`This section provides the basic nomenclature that is used in the following chapters.
`Subsystems:
`
`The radio base station system is composed of two basic subsystems, the radio equipment control and the
`radio equipment (see Figure 1). The radio equipment control and the radio equipment are described in the
`following chapter.
`Node:
`
`The subsystems REC and RE are also called nodes, when either an REC or an RE is meant. The Radio
`Base Station system shall contain at least two nodes, at least one of each type; REC and RE.
`Protocol layers:
`
`This specification defines the protocols for the physical layer (layer 1) and the data link layer (layer 2).
`
`Layer 1 defines:
`• Electrical characteristics
`• Optical characteristics
`• Time division multiplexing of the different data flows
`• Low level signalling
`Layer 2 defines:
`• Media access control
`• Flow control
`• Data protection of the control and management information flow
`Protocol data planes:
`
`The following data flows are discerned:
`
`Control Plane:
`
`Control data flow used for call processing.
`
`Management Plane:
`
`This data is management information for the operation, administration and
`maintenance of the CPRI link and the nodes.
`
`User Plane:
`
`Data that has to be transferred from the radio base station to the mobile station and
`vice versa. These data are transferred in the form of IQ data.
`
`Synchronization:
`Data flow which transfers synchronization and timing information between nodes.
`The control plane and management plane are mapped to a Service Access Point SAPCM as described below.
`User plane data:
`The user plane data is transported in the form of IQ data. Several IQ data flows are sent via one physical
`CPRI link. Each IQ data flow reflects the data of one antenna for one carrier, the so-called antenna-carrier
`(AxC).
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`Antenna-carrier (AxC):
`
`One antenna-carrier is the amount of digital baseband (IQ) U-plane data necessary for either reception or
`transmission of only one carrier at one independent antenna element.
`Antenna-carrier (AxC) Group:
`An AxC Group is an aggregation of NA AxC with the same sample rate, the same sample width, the same
`destination SAPIQ, and the same radio frame length. In case of NA=1 an AxC Group is the same as an AxC.
`AxC Container:
`An AxC Container is a sub-part of the IQ-data block of one basic frame. For UTRA-FDD it contains the IQ
`samples of one AxC for the duration of one UMTS chip. For WiMAX it contains IQ sample bits of one AxC
`and sometimes also stuffing bits. For E-UTRA it contains one or more IQ samples for the duration of one
`UMTS chip or it contains IQ sample bits and sometimes also stuffing bits.
`AxC Container Group:
`An AxC Container Group is an aggregation of NC AxC Containers containing IQ-samples for an AxC
`Group in one basic frame. NC is defined in section 4.2.7.2.7.
`AxC Symbol Block:
`An AxC Symbol Block is an aggregation in time of NSAM IQ samples for one WiMAX symbol plus NS_SYM
`stuffing bits. NSAM and NS_SYM are defined in section 4.2.7.2.6.
`AxC Container Block:
`An AxC Container Block is an aggregation in time of K AxC Container Groups or an aggregation in time of
`NSYM AxC Symbol Blocks plus NS_FRM stuffing bits. It contains S IQ samples per AxC plus stuffing bits. K
`and S are defined in section 4.2.7.2. NSYM and NS_FRM are defined in section 4.2.7.2.6.
`Service Access Points:
`
`For all protocol data planes, layer 2 service access points are defined that are used as reference points for
`performance measurements. These service access points are denoted as SAPCM, SAPS and SAPIQ as
`illustrated in Figure 2. A service access point is defined on a per link basis.
`Stuffing bits:
`
`Stuffing bits are used for alignment of WiMAX/E-UTRA sample frequencies to the basic frame frequency.
`Stuffing bits are also sent in TDD mode during time intervals when there is no IQ data to be sent over CPRI.
`The content of stuffing bits is vendor specific (“v”).
`Stuffing samples:
`If the total sampling rate per AxC Group is not the integer multiple of the CPRI basic frame rate (3.84MHz),
`then stuffing samples are added to make the total sampling rate the integer multiple of the CPRI basic
`frame rate. Stuffing samples are filled with vendor specific bits (“v”).
`Link:
`
`The term “link” is used to indicate the bidirectional interface in between two directly connected ports, either
`between REC and RE, or between two nodes, using one transmission line per direction. A working link
`consists of a master port, a bidirectional cable, and a slave port.
`
`Master/master and slave/slave links are not covered by this specification (for the definition of master and
`slave see below).
`Passive Link:
`
`A passive link does not support any C&M channel, i.e. it carries only IQ data and synchronization
`information. It may be used for capacity expansion or redundancy purposes, or for any other internal
`interfaces in a radio base station.
`Hop:
`
`A “hop” is the aggregation of all links directly connecting two nodes.
`Multi-hop connection:
`A “multi-hop connection” is composed of a set of continuously connected hops starting from the REC and
`ending at a particular RE including nodes in between.
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`Logical connection:
`A “logical connection” defines the interconnection between a particular SAP (e.g., SAPCM) belonging to a port
`of the REC and the corresponding peer SAP (e.g., SAPCM) belonging to a port of one particular RE and
`builds upon a single hop, or a multi-hop connection, between the REC and that particular RE. Logical
`connections for C&M data, user plane data and synchronization can be distinguished.
`Master port and slave port:
`
`Each link connects two ports which have asymmetrical functions and roles: a master and a slave.
`
`This is implicitly defined in CPRI release 1 with the master port in the REC and the slave port in the RE.
`
`This master/slave role split is true for the following set of flows of the interface:
`• Synchronization
`• C&M channel negotiation during start-up sequence
`• Reset indication
`• Start-up sequence
`Such a definition allows the reuse of the main characteristic of the CPRI release 1 specification, where each
`link is defined with one termination being the master port and the other termination being the slave port.
`
`At least one REC in a radio base station shall have at least one master port and optionally have other ports
`that may be slave or master.
`
`An RE shall have at least one slave port and optionally have other ports that may be slave or master.
`
`Under normal conditions a link has always one master port and one slave port. Two master ports or two
`slave ports connected together is an abnormal situation and is therefore not covered by this specification.
`Downlink:
`
`Direction from REC to RE for a logical connection.
`Uplink:
`
`Direction from RE to REC for a logical connection.
`
`
`
`Figure 1A and Figure 1B illustrate some of the definitions.
`
`
`
`SAPS
`SAPCM
`SAPIQ
`
`Logical Connection for Synchronization (REC(cid:0)RE #2)
`Logical Connection for C&M data (REC(cid:0)RE #2)
`Logical Connection for IQ data (REC(cid:0)RE #2)
`
`SAPS
`SAPCM
`SAPIQ
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`Master
`Port
`
`Slave
`Port
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`Master
`Port
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`Slave
`Port
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`REC
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`RE #1
`
`RE #2
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`Link
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`Hop
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`SAPS
`SAPCM
`SAPIQ
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`Figure 1A: Illustration of basic definitions
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`K Basic Frames, S samples K Basic Frames, S samples
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`AxC Container Block
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`AxC AxC
`Group
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`
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`AxC AxC
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`
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`AxC AxC
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`AxC AxC
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`ContainerContainer
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`GroupGroup
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`AxC AxC
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`ContainerContainer
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`AxC AxC
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`container container
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`
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`WiMAX Symbol WiMAX Symbol
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`
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`AxC AxC
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`AxC AxC AxC
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`
`
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`ContainerContainerContainer
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`AxC Symbol Block
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`AxC AxC AxC
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`ContainerContainerContainer
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`WiMAX Frame WiMAX Frame
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`WiMAX Symbol WiMAX Symbol
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`AxC Container BlockAxC Container Block
`AxC Symbol Block
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`
`AxC AxC AxC
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`ContainerContainerContainer
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`AxC AxC AxC
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`
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`ContainerContainerContainer
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`SAP IQSAP IQ
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`
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`SAP IQ SAP IQ
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`time
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`
`
`
`
`
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`Basic Frame Basic Frame
`
`
`
`Figure 1B: Illustration of AxC related definitions
`
`2.2. System Architecture
`Radio base stations should provide deployment flexibility for the mobile network operators, i.e., in addition to
`a concentrated radio base station, more flexible radio base station system architectures involving remote
`radio equipment shall be supported. This may be achieved by a decomposition of the radio base station into
`two basic building blocks, the so-called radio equipment control (REC) and the radio equipment (RE) itself.
`Both parts may be physically separated (i.e., the RE may be close to the antenna, whereas the REC is
`located in a conveniently accessible site) or both may be co-located as in a conventional radio base station
`design.
`
`The REC contains the radio functions of the digital baseband domain, whereas the RE contains the
`analogue radio frequency functions. The functional split between both parts is done in such a way that a
`generic interface based on In-Phase and Quadrature (IQ) data can be defined.
`
`For the UMTS radio access network, the REC provides access to the Radio Network Controller via the Iub
`interface, whereas the RE serves as the air interface, called the Uu interface, to the user equipment.
`
`For WiMAX, the REC provides access to network entities (e.g. other BS, ASN-GW), whereas the RE serves
`as the air interface to the subscriber station / mobile subscriber station (SS / MSS).
`
`For E-UTRA, the REC provides access to the Evolved Packet Core for the transport of user plane and
`control plane traffic via S1 interface, whereas the RE serves as the air interface to the user equipment.
`
`A more detailed description of the functional split between both parts of a radio base station system is
`provided in Section 2.4.
`
`In addition to the user plane data (IQ data), control and management as well as synchronization signals have
`to be exchanged between the REC and the RE. All information flows are multiplexed onto a digital serial
`communication line using appropriate layer 1 and layer 2 protocols. The different information flows have
`access to the layer 2 via appropriate service access points. This defines the common public radio interface
`illustrated in Figure 2. The common public radio interface may also be used as a link between two nodes in
`system architectures supporting networking. An example of a common public radio interface between two
`REs is illustrated in Figure 2A.
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`CPRI Specification V4.0 (2008-06-30)
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`Radio Base Station System
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`Network Interface
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`Radio Equipment Control (REC)
`Control &
`Mgmt
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`User Plane
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`Sync
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`Radio Equipment (RE)
`Control &
`Sync
`Mgmt
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`User Plane
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`Air Interface
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`SAPCM
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`SAPS
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`SAP IQ
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`SAPCM
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`Layer 2
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`Layer 1
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`CPRI link
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`SAP IQ
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`SAP S
`Layer 2
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`Layer 1
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`Master port
`Slave port
`Common Public Radio Interface
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`Figure 2: Basic System Architecture and Common Public Radio Interface Definition
`
`
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`Air Interface
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`Air Interface
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`
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`Network
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`Interface
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`Radio Base Station System
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`Radio Equipment Control (REC)
`Sync
`User Plane
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`Control &
`Mgmt
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`Radio Equipment (RE) #1
`Control &
`Sync
`User Plane
`Mgmt
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`
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`Control & Sync User Plane
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`
`Mgmt
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`SAP CM
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`SAP S SAP IQ
`Layer 2
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`SAP CM SAP S SAP IQ
`Layer 2
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`SAP CM SAP S SAP IQ
`Layer 2
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`Radio Equipment (RE) #2
`Sync User Plane
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`Control &
`Mgmt
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`SAP CM SAP S SAP IQ
`Layer 2
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`Layer 1
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`CPRI link
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`Layer 1
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`Layer 1
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`CPRI link
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`Layer 1
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`Master port
`Slave port
`Common Public Radio Interface
`
`Master port
`Slave port
`Common Public Radio Interface
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`Figure 2A: System Architecture with a link between REs
`
`
`
`2.3. Reference Configurations
`This section provides the reference configurations that have to be supported by the CPRI specification. The
`basic configuration, shown in Figure 3, is composed of one REC and one RE connected by a single CPRI
`link. The basic configuration can be extended in several ways:
`• First, several CPRI links may be used to enhance the system capacity as required for large system
`configurations involving many antennas and carriers (see Figure 4). It is required that an IQ data flow
`of a certain antenna and a certain antenna-carrier (see Section 2.1) is carried completely by one
`CPRI link (however, it is allowed that the same antenna-carrier may be transmitted simultaneously
`over several links). Therefore, the number of physical links is not restricted by this specification.
`• Second, several REs may be served by one REC as illustrated in Figure 5 for the so-called star
`topology.
`• Third, one RE may be served by multiple RECs as illustrated in Figure 5D. The requirements for this
`configuration are not fully covered in the CPRI specification; refer to section 6.3.7 for further
`explanation.
`• Furthermore, three basic networking topologies may be used for the interconnection of REs:
`o Chain topology, an example is shown in Figure 5A
`
`o Tree topology, an example is shown in Figure 5B
`
`o Ring topology, an example is shown in Figure 5C
`• Any other topology (e.g. combination of RECs and REs in a chain and tree) is not precluded. An
`example of reusing the CPRI interface for other internal interfaces in a radio base station is depicted
`in Figure 5E.
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`o
`
`If a radio base station has multiple RECs, e.g. of different radio access technologies, the
`CPRI interface may be used for the interface between two RECs.
`
`o The requirements for this configuration are not fully covered in the CPRI specification; refer
`to sections 6.3.7 and 6.3.8 for further explanation.
`
`REC
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`CPRI link
`
`RE
`
`
`
`Figure 3: Single point-to-point link between one REC and one RE
`
`RE
`
`
`
`CPRI link
`
`...
`
`CPRI link
`
`REC
`
`Figure 4: Multiple point-to-point links between one REC and one RE
`
`RE
`
`...
`
`RE
`
`)
`
`s
`
`(
`
`k
`
`R I li n
`
`P
`
`C
`
`...
`
`CPRI link(s)
`
`REC
`
`Figure 5: Multiple point-to-point links between one REC and several REs (star topology)
`
`
`
`...
`
`
`
`REC
`
`CPRI link(s)
`
`RE
`
`CPRI link(s)
`
`RE
`
`CPRI link
`
`Figure 5A: Chain topology
`
`CPRI
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`

`

`
`
`
`
`
`
`
`
`
`
`
`
`12
`
`CPRI Specification V4.0 (2008-06-30)
`
`...
`
`...
`
`
`
`
`
`...
`
`
`
`CPRI link(s)
`
`RE
`
`REC
`
`CPRI link(s)
`
`RE
`
`CPRI link(s)
`
`RE
`
`Figure 5B: Tree topology
`
`REC
`
`CPRI link(s)
`
`RE
`
`CPRI link(s)
`
`RE
`
`CPRI link(s)
`
`Figure 5C: Ring topology
`
`REC
`
`CPRI link(s)
`
`RE
`
`REC
`
`CPRI link(s)
`
`
`Figure 5D: Multiple point-to-point links between several RECs and one RE
`
`REC
`
`CPRI link(s)
`
`REC
`
`CPRI link(s)
`
`RE
`
`Figure 5E: Chain topology of multiple RECs
`
`CPRI
`
`

`

`
`
`
`
`13
`
`CPRI Specification V4.0 (2008-06-30)
`
`2.4. Functional Description
`
`2.4.1. Radio Functionality
`
`This section provides a more detailed view on the functional split between REC and RE, which provides the
`basis for the requirement definition in the next chapter.
`
`The REC is concerned with the Network Interface transport, the radio base station control and management
`as well as the digital baseband processing. The RE provides the analogue and radio frequency functions
`such as filtering, modulation, frequency conversion and amplification. An overview on the functional
`separation between REC and RE is given in Table 1 for UTRA FDD and in Table 1A for WiMAX and E-
`UTRA.
`
`Table 1: Functional decomposition between REC and RE (valid for the UTRA FDD standard)
`
`Functions of REC
`
`Functions of RE
`
`Downlink
`
`Uplink
`
`Downlink
`
`Uplink
`
`Radio base station control & management
`
`
`
`
`
`Iub transport
`
`RRC Channel Filtering
`
`Iub Frame protocols
`
`D/A conversion
`
`A/D conversion
`
`Channel Coding
`
`Channel De-coding
`
`Up Conversion
`
`Down Conversion
`
`Interleaving
`
`De-Interleaving
`
`Spreading
`
`Scrambling
`
`De-spreading
`
`De-scrambling
`
`MIMO processing
`
`ON/OFF control of each
`carrier
`
`Automatic Gain Control
`
`Carrier Multiplexing
`
`Carrier De-multiplexing
`
`Power amplification and
`limiting
`
`Low Noise Amplification
`
`Adding
`channels
`
`of
`
`physical
`
`distribution
`Signal
`signal processing units
`
`to
`
`Antenna supervision
`
`
`
`Transmit Power Control
`of each physical channel
`
`Frame and slot signal
`generation
`(including
`clock stabilization)
`
`Transmit Power Control &
`Feedback
`Information
`detection
`
`
`RF filtering
`
`RF filtering
`
`
`
`Measurements
`
`Measurements
`
`
`
`CPRI
`
`

`

`
`
`
`
`14
`
`CPRI Specification V4.0 (2008-06-30)
`
`Table 1A: Functional decomposition between REC and RE (valid for WiMAX & E-UTRA)
`
`Functions of REC
`
`Functions of RE
`
`Downlink
`
`Uplink
`
`Downlink
`
`Uplink
`
`Radio base station control & management
`
`Add CP (optional)
`
`
`
`Backhaul transport
`
`MAC layer
`
`Channel Coding,
`Interleaving, Modulation
`
`Channel De-coding, De-
`Interleaving,
`Demodulation
`
`iFFT
`
`FFT
`
`Channel Filtering
`
`D/A conversion
`
`Up Conversion
`
`A/D conversion
`
`Down Conversion
`
`ON/OFF control of each
`carrier
`
`Automatic Gain Control
`
`Add CP (optional)
`
`Remove CP
`
`Carrier Multiplexing
`
`Carrier De-multiplexing
`
`MIMO processing
`
`Signal aggregation from
`signal processing units
`
`Signal distribution to
`signal processing units
`
`Transmit Power Control
`of each physical channel
`
`Transmit Power Control &
`Feedback Information
`detection
`
`Power amplification and
`limiting
`
`Low Noise Amplification
`
`Antenna supervision
`
`
`
`RF filtering
`
`RF filtering
`
`Frame and slot signal
`generation (including
`clock stabilization)
`
`
`
`Measurements
`
`
`
`TDD switching
`in case of TDD mode
`
`Measurements
`
`2.4.2. CPRI Control Functionality
`
`This section provides a more detailed view on the functional split between REC and RE for CPRI
`functionality beyond the specification itself.