CE Level


CE Operation is categorized into four difference levels. These for groups are devided into two groups and each of the group belong to two different Operation Mode as below.





Mode A

Level 1

No Repetition for PRACH

Level 2

Small Number of Repetition for PRACH

Mode B

Level 3

Medium Number of Repetition for PRACH

Level 4

Large Number of Repetition for PRACH


Each of the level differs mostly in RACH and Paging process. Some of the major differences with different CE levels are :

  • RACH configuration and resources (e.g, frequency, time, preamble) associated with each of the RACH configuration
  • Frequency resources used for RACH transmission
  • Repetition Number for RACH Preamble


How UE can figure out which Mode and which Level it has to apply ?


Basically Operation mode is determined by eNB and the Level within each Mode is determined by UE. The operation mode is determed by eNB and informed to UE via RRC message and the level is determined by UE. Then you may ask how UE determine the level and inform it to eNB ? UE determined the level based on the reference signal power (RSRP) it measure and inform it to eNB by PRACH resource (frequency, time, preamble) it uses.


All the information that UE need to determine CE Level and necessary PRACH resource information is notified to UE via SIB2 infromation as outlined below.



NOTE 1 : The number of items under RACH-CE-LevelInfo should be same as the number of items under prach-ParameterListCE

NOTE 2 : For the details of RACH-CE-LevelInfo, refer to this note.

NOTE 3 : For the details of RSRP-ThresholsPrachInfoList and prach-ParameterListCE, refer to this note.




Reference :


[1] 4G, LTE-Advanced Pro and The Road to 5G by  Erik Dahlman, Stefan Parkvall, Johan Skold

[2] 3GPP TSG RAN WG1 Meeting #83 R1-156698 : MPDCCH for Paging at multiple CE Levels

[3] 3GPP TS 36.213 V13.2.0 (2016-06) : Physical layer procedures (Release 13)