eCPRI message format | eCPRI header | eCPRI message types

This page describes eCPRI message format including eCPRI header, eCPRI payload and transmission order. It also mentions eCPRI message types.

• eCPRI stands for Enhanced Common Public Radio Interface.
• The basic idea is to divide functionalities of BS (Base Station) into two blocks viz. REC (Radio Equipment Control) and RE (Radio Equipment) and connect them via packet based fronthaul transport network such as Ethernet or IP. This is shown in the figure-1. REC and RE terms are used with CPRI where as same terms are renamed as eREC and eRE in eCPRI interface.
• eCPRI handles following service points viz. User Plane Traffic, Synchronization and Control & Management.
• eCPRI can be used between single eRECs and eREs as well as multiple eRECs/eREs.

eCPRI fronthaul connection

• Both eREC and eRE are physical separated where in eRE is kept near to antenna and eREC at far end.

eCPRI message format

eCPRI message format

The figure-2 depicts eCPRI message format.

• For User plane over ethernet, eCPRI messages are transmitted in standard ethernet frames. Minimum size of data field of ethernet frame is 46 octets. Frames with payload sizes larger than 1500 octets can also be supported.
• For User plane over IP, eCPRI messages are transmitted in UDP/IP packets.

• eCPRI message structure is as follows.
eCPRI message =
eCPRI header (4 bytes)
eCPRI payload (variable size)

eCPRI header format | eCPRI Common Header

eCPRI header format

The figure-3 depicts eCPRI header format with all the eCPRI common header fields.

eCPRI message common header consists of following fields.
eCPRI header =
eCPRI protocol revision (4 bits)
Reserved (3 bits)
C bit (1 bit), C = 0 indicates that the current eCPRI message is the last one inside the eCPRI PDU
C = 1 indicates that another eCPRI message follows this current one within the eCPRI PDU.
eCPRI message type (8 bits), type of service carried by the message.
eCPRI payload size (16 bits), maximum supported payload size is 216-1.

eCPRI message types

Following table-1 mentions eCPRI message types.

Message Type Name of message
0 IQ Data
1 Bit Sequence
2 Real time control data
3 Generic Data transfer
4 Remote Memory Access
5 One way delay measurement
6 Remote reset
7 Event Indication
8 to 63 Reserved
64 to 255 Vendor Specific

Refer eCPRI protocol stack >> for more information how the eCPRI message of different types flow through the eCPRI protocol stack.


• eCPRI Specification V1.2 (2018-06-25), Download CPRI Specifications >>.

CPRI and eCPRI Related Links

5G NR Numerology | 5G NR Terminology

5G NR Control channels | 5G NR Traffic Channels | 5G NR Reference Signals and sequences


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5G Frequency Bands
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5G millimeter wave channel sounding
Difference between 4G and 5G
5G testing and test equipments
5G network architecture
5G NR Physical layer
5G NR MAC layer
5G NR RLC layer
5G NR PDCP layer

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