Difference between CDRX and ANR-DRX in LTE

Hello Experts.

Is anyone aware of the difference between CDRX and ANR-DRX in LTE?


Cdrx is connected mode drx having state sleep and active use for UE battery saving to get it in sleep mode when no PDCCH to listen for DL/UL grants.
ANR-DRX: it’s new term for me, never heard any DRX with ANR.
Idle mode DRX also there for UE in idle mode.

Yes @ankgitm.
Yes in addition to this eDRX is there but ANR-DRX even I have also not heard.

ANR-DRX is not a 3gpp term, I have heard it while working with Qualcomm.

ANR-DRX is used to get mobile in to MGAP in for measuring ECGI of the neighbor cell.

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Basically when UE need to read CGI for same RAT or different RAT base station configure DRX.
The value for DRX period is different than the normal connected mode DRX.

Normal MGAP is not sufficient to measure sib1 (ecgi) of NBR, hence in ANR DRX is used.

That’s not DRX. It’s called autonomus gaps as per 3gpp for CGI purpose.

If no meas gap configured then also UE can report CGI.

How to do this?

Autonomous gap.

T321 timer also there linked with CGI.
I’ve seen and tried without MGAP and DRX config CGI can be reported just like intra frequency measurement report.

Guys, CDRX and ANR-DRX both are same.
The only difference is DRX that in ANR-DRX UE performs off-period measurements on target cell. e.g. Reading SIB1 for CGI info.

ANR-DRX seems some internal terminology adopted.

You can call it as CDRX working ANR is active.
All the measurements related to neighbors are done at sleep cycle.
E.g. for Inter freq case performing measgap within sleep mode.
And for Intrafreq reading SIB1 to acquire target CGI.

For inter Freq/inter rat mr we always need mgap or drx config as per understanding.
For intra Freq mr no need of mgap/Drx same for CGI reporting.

Right, I have also written same. :+1:

For CGI measurement in ANR, enb will configure special ANR-DRX cycle for UE evenif CDRX is not activated. Because cgi is in sib1, its periodicity is at least 20ms, larger than normal cdrx cycle. So, anr drx cycle is recommended to set high value. If not, UE can not decode cgi.

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Any of experts can assist? Why UE is supposed to be in DRX mode when reading sib1 of the neighbor? is it mandatory to activate ANR-DRX when reading cgi of the neighbor cells?