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About Me LTE: RRC Connection Reestablishment Request All 5G/LTE Posts

Kumara Swamy The purpose of RRC CONNECTION RE-ESTABLISHMENT procedure is to re-establish the RRC 5G NR: 2-Step Random Access Procedure
(Release-16)
View my complete profile connection, which involves the resumption of SRB1 operation and the re-activation of security (without changing
algorithms). The UE shall only initiate this procedure when AS security has been activated. 5G NR: PDSCH Resource Allocation in
Frequency-Domain
The connection re-establishment succeeds only if the concerned cell is prepared i.e. has a valid UE
Total Pageviews context. In case E-UTRAN accepts the re-establishment, SRB1 operation resumes while the operation of other 5G NR: PUSCH Resource Allocation in
Frequency-Domain
radio bearers remains suspended. If AS security has not been activated, the UE doesn’t initiate this procedure,
2,105,451 instead, it moves to RRC_IDLE directly 5G NR: Measurement Configuration

The UE initiates the RRC CONNECTION RE-ESTABLISHMENT procedure when one of the following conditions 5G NR: Measurement GAPs
is met:
5G NR: PUSCH Resource Allocation in Time-
Upon detecting radio link failure; or Domain
Upon handover failure; or
5G NR: PDSCH Resource Allocation in Time-
Labels Upon mobility from E-UTRA failure; or Domain
5G (29) Upon integrity check failure indication from lower layers; or 5G NR: Time Domain – Slots and Slot Formats
5G NR (28) Upon an RRC CONNECTION RECONFIGURATION failure
5G NR: Bandwidth Part
BSR (1) 5G NR: Resource Blocks
RRC Connection Reestablishment Request Message
Buffer Status Reporting (1) 5G NR: Resource Grid
Direction: UE => E-UTRAN
Bundling (3) 5G NR: SIB9
Signalling Radio Bearer: SRB0
BWP (1) RLC Mode: TM 5G NR: SIB6, SIB7 and SIB8
Logical Channel: CCCH
Carrier Aggregation (7) 5G NR: SIB5
Transport Channel: UL-SCH
CQI (2) 5G NR: SIB4
IEs in RRC CONNECTION REESTABLISHMENT REQUEST message are given below:
CRE (5) 5G NR: SIB3
ue-Identity: UE identity is included to retrieve UE context and to facilitate contention resolution by lower layers.
CS fallback (2) 5G NR: SIB2
The UE Identity shall be set as follows:
CSG (1) 1. Set the C-RNTI to the C-RNTI used in the source PCell (In case of handover and mobility from E-UTRA
failure) or used in the PCell in which the trigger for the re-establishment occurred (other cases); 5G NR: SIB1
CSI (3) 2. Set the physCellId to the physical cell identity of the source PCell (handover and mobility from E-UTRA
5G NR: System Information
failure) or of the PCell in which the trigger for the re-establishment occurred (other cases);
DCI Formats (9) 3. Set the shortMAC-I to the 16 least significant bits of the calculated MAC-I 5G NR: Synchronization Signal/PBCH block
(SSB)
DRX (2) reestablishmentCause: This IE indicates the failure cause that triggered the re-establishment procedure and shall
be set as follows: 5G NR: PBCH and Master Information Block
eICIC (5) (MIB)
1. If the re-establishment procedure was initiated due to reconfiguration failure (the UE is unable to comply
EMM (28) with the reconfiguration sent in RRC CONNECTION RECONFIGURATION), then set the
reestablishmentCause to the value 'reconfigurationFailure'; 5G NR: Secondary Synchronization Signal
2. If the re-establishment procedure was initiated due to handover failure (intra-LTE handover failure or inter- (SSS)
EN-DC (1)
RAT mobility from EUTRA failure) then, set the reestablishmentCause to the value 'handoverFailure'
3. Set the reestablishmentCause to the value 'otherFailure' if the re-establishment procedure was triggered 5G NR: Primary Synchronization Signal (PSS)
EPC (51)
due other causes than indicated in cases 1 and 2
5G NR: UE RRC States and State Transitions
ESM (17)
Example: RRC CONNECTION REESTABLISHMENT REQUEST
DCI Formats in 5G NR
FeICIC (5)
RNTIs in 5G NR
FGI (1)
5G NR: MAC PDU Formats and Parameters
gNB (3)
related to RA procedure
Hetnet (4)
5G NR: Random Access Procedure
ICIC (5)
5G NR: Numerologies and Frame Structure
LTE Calculators (12)
LTE: Carrier Aggregation - SCell Activation and
Deactivation Timings
LTE Security (7)
LTE: TDD Timing Calculator
LTE System Information (10)
LTE Feature Group Indicators Decoder
MAC CE (1)
LTE: Carrier Aggregation based ICIC
MAC PDU (4)
Reference: 3GPP TS 36.331
LTE: Further enhanced Inter-Cell Interference
MAC Procedures (13)
Coordination: FeICIC
measurement gap (3) Very Useful (7) Useful (1) Not Useful (1) More Like This Please (0)
Reactions: LTE: Enhanced Inter-Cell Interference
measurements (1) Coordination: eICIC
Posted by Kumara Swamy
NAS (45) LTE: Inter-Cell Interference Coordination: ICIC
Labels: EPC, RRC, RRC Messages

NR (19) LTE: Cell Range Extension (CRE)

NR PHY (10)
69 comments: LTE: PUCCH Frequency Resource Calculator

NR SIB (9) LTE: Resource Allocation Calculator

Anonymous December 12, 2012 at 5:22 PM
Periodic CSI (4) LTE: Random Access Response MAC PDU
wht do u think about other failure? Decoder
PHY (17) Reply LTE: MAC PDU Decoder
PHY Procedures (20)
LTE: Multiple Timing Advances for uplink
Power Control (1) Carrier Aggregation
Kumara Swamy December 13, 2012 at 4:59 AM
Random Access (6) Hi LTE: Cross-Carrier Scheduling in Carrier
Aggregation
Resource Allocation (19)
'OtherFailure' could be because of radio link failure, integritycheck failure etc.. whichever doesn't fall in LTE: Carrier Aggregation - SCell Measurements
RNTI (10) the category of 'handoverFailure' or 'reconfigurationFailure'
LTE: Carrier Aggregation - Activation and
RRC (36) Reply Deactivation of Secondary Cells

RRC Messages (39) LTE: Carrier Aggregation - Secondary Cell

Addition/Modification/Release
Scheduling Request (3) Unknown January 28, 2013 at 2:47 PM
RNTIs in LTE
Is it possible UE Can trigger re-estbalishment without initiative RACH procedure ?
Semi-Persistent Scheduling (6)
LTE: Periodic CSI Reporting Calculator
Reply
sps (5)
LTE: SRS Calculator
SR (3) Replies
LTE: Sounding Reference Signal Procedure
SRS (4) Unknown May 27, 2020 at 12:22 PM
LTE: Measurement GAP Calculator
SSB (5) no..
LTE: SPS Calculator
System Information (13)
Reply LTE: Scheduling Request Timing Calculator for
TDD (2) FDD and TDD

Timing Advance (4) LTE: Connected Mode DRX Calculations

Kumara Swamy February 1, 2013 at 9:37 AM LTE: Timing Advance and Time Alignment
TTI Bundling (3)
It is not possible to trigger re-establishment procedure without RACH procedure. Timer
UE Capabilities (2)
Reply LTE: Connected Mode DRX
UE Identities (6)
LTE: Buffer Status Reporting Procedure
UE states (1)
Anonymous June 24, 2013 at 12:17 PM LTE: Scheduling Request Procedure

Based on what condition eNB come to know UE has lost its Radio link between the UE and eNB? RNTIs in LTE
Reply LTE: TTI Bundling

Replies LTE: Activate Dedicated EPS Bearer Context

Reject
Unknown May 27, 2020 at 12:24 PM LTE: Semi-Persistent Scheduling
if the measured rsrp is too low. or sinr is too low or if it does not get any ack/nack msg from
LTE: Downlink Resource Allocation Type 1
pdsch
LTE: Downlink Resource Allocation Type 2 and
Uplink Resource Allocation Type 0
Reply
LTE: Downlink Resource Allocation Type 0

LTE: Resource Allocation

Ankur Sinha July 9, 2013 at 10:57 AM
LTE: ESM Information Request Procedure
upon receiving N310 consecutive "out-of-sync" indications for the Cell from lower layers a timer T310 is
started and when this timer expires. It is understood by UE that RLF has occured LTE: Modify EPS Bearer Context Reject

Reply LTE: Modify EPS Bearer Context Request

LTE: Bearer Resource Modification Reject

Canvas August 14, 2013 at 10:07 AM LTE: Bearer Resource Modification Request
How many times a UE can try re-establishment? LTE: Bearer Resource Allocation Reject
Reply
LTE: Bearer Resource Allocation Request

LTE: Deactivate EPS Bearer Context Accept

Kumara Swamy August 26, 2013 at 10:04 AM LTE: Deactivate EPS Bearer Context Request
Once the RRC Connection Re-establishment procedure is triggered, the UE shall start the timer T311,
LTE: PDN Disconnect Request
and once the UE selects a suitable cell, this T311 timer is stopped, and RRC initiates the transmission of
RRC Connection Re-establishment message and start the timer T301. This timer is stopped only when LTE: PDN Connectivity Reject
"Reception of RRC Connection Reestablishment or RRC Connection Reestablishment Reject message
as well as when the selected cell becomes unsuitable" LTE: PDN Connectivity Request

LTE: Activate Dedicated EPS Bearer Context

If either T311 or T301 expires, the UE goes to Idle mode and no more RRC Connection Re- Accept
establishments sent. This implies that the UE could try re-establishment only once after the procedure is
triggered. LTE: Activate Dedicated EPS Bearer Context
Request

Reply LTE: Activate Default EPS Bearer Context

Accept

LTE: Activate Default EPS Bearer Context

Anonymous August 31, 2013 at 8:19 PM Request

Hi LTE: EMM Information

LTE: Transport of NAS messages

is it possible eNB detect the false RRC Connection Re-establishment request?

Reply LTE: Detach Accept

LTE: Detach Request (Network Initiated)

Replies
LTE: Detach Request (UE initiated)
Kumara Swamy September 2, 2013 at 6:02 AM
LTE: CS Service Notification
Please specify what do you mean by False RRC connection re-est request
LTE: Service Reject

Reply LTE: NAS Level Congestion Control

LTE: Extended Service Request

LTE: Service Request

Unknown September 2, 2013 at 11:48 AM
Integrity Check Failure Case: LTE: Security Protected NAS message

LTE: Identity Response

It check fails at UE PDCP, it intimates to RRC about it and RRC triggers RRC Connection re-
establishment. LTE: Identity Request
How about at eNodeB, What RRC will do once it got indication from PDCP of eNOdeB.
LTE NAS: Security Mode Reject

LTE NAS: Security Mode Complete

Regards,
Venky LTE NAS: Security Mode Command

Reply LTE: Authentication Failure

LTE: Authentication Reject

Kumara Swamy September 2, 2013 at 12:14 PM LTE: Authentication Response

Most of such error handling is done by releasing the existing RRC connection with release cause "other" LTE: Authentication Request
Reply LTE: Tracking Area Update Complete

LTE: Tracking Area Update Accept

sarvjeet September 14, 2013 at 6:39 AM LTE: Tracking Area Update Reject
WHAT IS MEAN BY VALID UE CONTEXT
LTE: GUTI
Reply
LTE: Tracking Area Update Request

LTE: Attach Complete

sarvjeet September 14, 2013 at 6:44 AM
LTE: Attach Reject
and please also explain short mac-i,pcell
LTE: Attach Accept
Reply
LTE: Attach Request

LTE: System Information Block Type 7

Kumara Swamy September 15, 2013 at 5:40 PM
LTE: System Information Block Type 6
Usually, eNB maintains (at RRC) an UE context once the connection is established (also, a context
between the MME and eNodeB) LTE: System Information Block Type 5

LTE: System Information Block Type 4

The IE ShortMAC-I is used to identify and verify the UE at RRC connection re-establishment. The 16
least significant bits of the MAC-I calculated using the security configuration of the source PCell LTE: System Information Block Type 3

PCell is the primary cell on which UE has initiated the connection establishment and attached to. This LTE: System Information Block Type 2
terminology is wrt to Carrier Aggregation where there could be more than one serving cell (aggregated) to
LTE: System Information Block Type 1
increase the bandwidth. All additional serving cells apart from PCell are referred to as secondary cells
(SCells) LTE: Master Information Block

LTE: Paging
Reply
LTE: RRC Connection Release

LTE: DL Information Transfer

Anonymous October 18, 2013 at 5:57 PM
LTE: UL Information Transfer
Hi,
LTE: Measurement Report
Since RRC Re-establishment occur after losing RRC connection so every rrc re-establishment request
LTE: Mobility from E-UTRA Command
can consider as RRC drop irrespective of re-establishment success or failure. ??
LTE: RRC Connection Reestablishment Reject
If re-establishment occur due to handover failure is it possible to get re-establishment success because
handover means cell will be change and Ue context will not be available in new cell. LTE: RRC Connection Reestablishment
Complete
Reply
LTE: RRC Connection Reestablishment

LTE: RRC Connection Reestablishment

Kumara Swamy October 21, 2013 at 10:42 AM Request

The re-establishment (triggered due to HO failure) can also be successful as the UE context is not moved LTE: RRC Connection Reconfiguration
to new cell until HO success Complete

Reply LTE: RRC Connection Reconfiguration

LTE: UE Capability Information

Replies
LTE: UE Capability Enquiry
RajeshKumar@CommonMan December 24, 2014 at 8:27 AM
LTE RRC: Security Mode Failure
Means UE send RRC Re-Establishment Req to Old eNB rather than new eNB in case of HO?
LTE RRC: Security Mode Complete
Reply
LTE RRC: Security Mode Command

LTE: RRC Connection Reject

Anonymous October 30, 2013 at 8:02 AM LTE: RRC Connection Setup Complete
If the radio link is failed with current cell due to HO failure. UE tries to establish RRC connection again by LTE: RRC Connection Setup
sending RRC connection reestablishment request to eNB. Suppose in our scenario, by that time UE is
moved to new cell (target eNB) where it is getting good signal, then, LTE: RRC Connection Request

LTE: UE Identities
Will the same UE sends RRC connection re-establishment request or new RRC connection request to
target eNB? (But still the existing UE context with source eNB has not been transferred to target eNB.)

Can anyone clear this?

Reply Followers
Follower (206) Weiter
Kumara Swamy October 30, 2013 at 10:38 AM

The UE sends RRC Connection Re-establishment towards new eNB.

The RLF Indication procedure may be initiated after a UE attempts to re-establish the radio link
connection at eNB B after a failure at eNB A. The RLF INDICATION message sent from eNB B to eNB A
shall contain the following
information elements:
Folgen
- Failure Cell ID: PCI of the cell in which the UE was connected prior to the failure occurred;
- C-RNTI: C-RNTI of the UE in the cell where UE was connected prior to the failure occurred;
- shortMAC-I (optionally): the 16 least significant bits of the MAC-I calculated using the security
configuration of the source cell and the re-establishment cell identity;
- UE RLF Report Container (optionally): the RLF Report received from the UE

eNB B may initiate RLF Indication towards multiple eNBs if they control cells which use the PCI signalled
by the UE during the re-establishment procedure. The eNB A selects the UE context that matches the
received Failure Cell ID and C-RNTI, and, if available, uses the shortMAC-I to confirm this identification,
by calculating the shortMAC-I and comparing it to the received IE

Reply

Replies

Unknown August 7, 2014 at 12:18 PM

This comment has been removed by the author.

Unknown August 7, 2014 at 12:20 PM

This comment has been removed by the author.

Unknown August 31, 2015 at 4:52 PM

Very good reply KSP. Just a few updates

-- shortMAC-I is signed with the source cell K_rrc_integrity (see 36.331, section 5.3.7.4)

There are two situations:

-- if eNB B is already a "prepared" cell, i.e eNB B had received HO Request from eNB A which
used the UE's old-CRNTI, then eNB B has UE context and will continue with successful RRC
Re-establishment.

-- Else, eNB B is not a prepared cell, i.e had not previously received HO Request from eNB A.
From Rel-12 onwards, eNB-B will send a RLF indication message to eNB A. eNB A will verify
the UE' CRNTI and then will proceed with Handover Request message to eNB B. (See 36.300
Section 20.2.2.12, If the previous serving eNB matches the correct context, it may also trigger
the Handover Preparation procedure towards the eNB that initiated the Radio Link Failure
Indication procedure.).
This way eNB-B gets UE's context from eNB-A. But this is only supported from Rel-12
onwards.

Once RRC Connection is Re-established the AS keys are changed to eNB-B.

Reply

Unknown April 15, 2014 at 12:49 PM

Hi,

I have a particular problem was wondering if you could help. I have RRC connection recofiguration (HO
information) then RRC Connection reconfiguration complete in target cell. X2 based so I can see
pathswitch being acknowledged for erab id 5 but then the HO fails the UE reads MIB in the target cell and
also does a RRC connection re-establishment with cause "HO Failure". Is this to do with lower layer sync
issue or something else ?

Reply

Anonymous September 9, 2014 at 6:22 AM

what is the total size of the message ?

Reply

Kumara Swamy October 15, 2014 at 7:28 PM

6 bytes

Reply

Unknown October 23, 2014 at 2:34 PM

How can I make Ue to trigger re-establishment request by integrity check failure. I mean after UE
attached to Pcell and scell is configured I want UE to send re-establishment with reason as other failure.
Can you please help?

Reply

Kumara Swamy October 23, 2014 at 3:07 PM

Try radio link failure instead of integrity check failure which must be easy in any test environment.

Reply

Unknown October 24, 2014 at 6:27 AM

Sorry, I have to use integrity check because it is a specific requirement. How to trigger this?
Thanks in advance.

Reply

Replies

Kumara Swamy October 24, 2014 at 10:52 PM

Which Test environment is being used? after succesful security procedure, reconfigure
integrity protection algorithm at the simulator side but don't signal to the UE. I think this will do
the job, but I am not 100% sure

Reply

Unknown November 12, 2014 at 12:19 AM

Hello, Im noticing that all of the "LTE RRC Connection Reestablishment Requests" are rejected
inmediatly by the network. Is it possible that the network im working on currently does not have active the
Reestablishment feature? And if so What is it needed to activate it and what is the procedure? Thanks a
lot.

Reply

Replies

Kumara Swamy November 12, 2014 at 9:43 AM

Hi,
Is Reestablishment request is sent on the serving cell or any other cell? There may be a
possibility that the UE is sending Reestablishment request message on some other cell, and
that particular cell is not prepared for Reestablishment, meaning that it can't fetch UE's context
from the source cell....

Unknown November 12, 2014 at 4:10 PM

Hi, In all of the cases the Reestablishment request is sent on the serving cell and on directed
to the serving cell. Also in all of the drive tests i have seen there isn't a single successful "LTE
RRC Connection Reestablishment".

Anonymous January 10, 2019 at 1:03 PM

hi

Reply

Anonymous December 10, 2014 at 10:23 AM

Could you please tell how rrc will get re-established if radio-link failure detect (due to RLC Max
retransmission) at eNodeB side?

Reply

Anonymous January 14, 2015 at 1:31 PM

hi

Reply

Anonymous February 17, 2015 at 1:46 PM

Hi!

I am trying to detect a radio link failure. In case the re establishment cause is 'otherFailure', but it is not
specified exactly if it is RLF or something else, how can I track this using other messages? For example
by receiving an RRCConnectionRequest, could it mean that the UE went into Idle mode due to a radio
link failure and now it is trying to reconnect to the network?

Thanks in advance :)
Reply

Anonymous June 17, 2015 at 12:24 PM

Hi
I want to reduce RRC reestablishment attempt for HO to Improve HO Performance so which NSN
Parameter need to tune to Reduce RRC reestablishment attempt.

Reply

Anonymous June 18, 2015 at 3:55 AM

Hi
I want to reduce RRC reestablishment attempt for HO to Improve HO Performance so which NSN
Parameter need to tune to Reduce RRC reestablishment attempt.

Reply
Reply

Mohal Joshi September 17, 2015 at 11:34 PM

This comment has been removed by the author.

Reply

Mohal Joshi September 17, 2015 at 11:35 PM

When Radio Link Failure occurs T311 timer starts along with Reestablishment. However receipt of which
message or event on UE side will stop the T311 timer. Standard simply says "“selection of suitable E-
UTRA cell” but doesn't explicitly say that on receipt of which message from eNB will UE stop running
T311 Timer

Reply

Replies

Kumara Swamy October 6, 2015 at 9:13 AM

Hi Mohal,

There is no need to receive any message from the eNodeB to for the "Selection of suitable E-
UTRA Cell".

The UE shall select a suitable cell based on idle mode measurements and cell selection
criteria.

A "suitable cell" is a cell on which the UE may camp on to obtain normal service. The UE shall
have a valid USIM and such a cell shall fulfil all the following requirements.
- The cell is part of either:
- the selected PLMN, or:
- the registered PLMN, or:
- a PLMN of the Equivalent PLMN list
- The cell is not barred, see subclause 5.3.1 in 36.304;
- The cell is part of at least one TA that is not part of the list of "forbidden tracking areas for
roaming" [4], which belongs to a PLMN that fulfils the first bullet above;
- The cell selection criteria are fulfilled, see subclause 5.2.3.2 in 36.304;

If more than one PLMN identity is broadcast in the cell, the cell is considered to be part of all
TAs with TAIs constructed from the PLMN identities and the TAC broadcast in the cell.

For more information on Cell selection/reselection procedures, please look into 36.304

Reply

Mainpal December 28, 2015 at 7:10 AM

Hi KSP,

Which message EnodeB will communicate to MME after Receiving the Reestablishment Complete
message from UE. what else messages will transverse between enodeb and mme, before sending
Reconfiguration message to UE from EnodeB after Reestablishment complete message has been
received at EnodeB.

Thanks
Reply

Anonymous January 3, 2016 at 7:14 PM

How UE sends Reestablishment request message to other cells?

Reply

Replies

Kumara Swamy January 4, 2016 at 9:11 AM

It is same way as RRC Connection Request (establishment)...

Reply

Unknown January 4, 2016 at 10:27 AM

Hi,
Can anyone explain various reasons of HO fails in both preparation phase and execution phase in LTE?

Reply

Unknown January 7, 2016 at 9:02 AM

This comment has been removed by the author.

Reply

Unknown January 8, 2016 at 5:00 PM

Hi KMP,
If you please tell me the initial trouble shooting for SINR. SRB1 success ratio can be degraded because
of SINR?. or SINR is main cause of Re-establishment? thanks

Reply

Unknown February 4, 2016 at 11:53 AM

hi,
interesting subject but there is a question i could not find answer for:
why RRC re establishment on target cell after HO failure succeed if x2 interface exist and fails if there is
no X2.

Reply

Replies

Kumara Swamy February 4, 2016 at 12:38 PM

Broadly speaking, one of X2 control plane functions is to transfer the UE context from source
eNB to the target eNB.

After having detected handover failure, the UE attempts to resume the RRC connection either
in the source eNB or in another eNB using the RRC re-establishment procedure. This
connection resumption succeeds only if the accessed cell is prepared, i.e. concerns a cell of
the source eNB or of another eNB towards which handover preparation has been performed.

Reply

Ashutosh Kaushik April 6, 2016 at 3:12 PM

Hi KSP , First of all I want to mention that I have been reading your blog for some time now, I must
appreciate your work and knowledge.I gained knowledge on many topics here.
For this topic I have two queries :-
1) You mentioned in one of your comments dated 26th August 2013 that "Once the RRC Connection Re-
establishment procedure is triggered, the UE shall start the timer T311, and once the UE selects a
suitable cell, this T311 timer is stopped, and RRC initiates the transmission of RRC Connection Re-
establishment message and start the timer T301. This timer is stopped only when "Reception of RRC
Connection Reestablishment or RRC Connection Reestablishment Reject message as well as when the
selected cell becomes unsuitable".
My doubt is that until the RRC connection re-establishment procedure is unsucessful the UE is not moved
to RRC idle state and remains in RRC conencted state as per literatures.If for any reason RRC
connection re-establishment is failed or rejected then only UE moves to idle state so why we are
mentioning "suitable cell selection" here when a UE is already connected. This should be applicable only
when UE attempts for new RRC connection request in a new cell , isn't it? As per my understanding timer
T311 is started after sending RRC connection re-establishment request message and it covers all
attempts of RRC connection re-establishments. Whereas timer T301 is also started after sending RRC
connection re-extablishment request message but covers only duration waiting for a response (either
accept or reject). I think timer T301 is subset of timer T311. T301 is for each attempt and there can be
more than 1 attempt of RRC conn. restb and for covering all attempts we have timer T311.

My understanding may be wrong , this is what I have read in Ericsson's literature.

Please explain me properly if correction is required.

Thanks & Regards,

Ashutosh Kaushik
Reply

Ashutosh Kaushik April 6, 2016 at 3:16 PM

My second question is that what contents are present in a "context fetch" message ie. what are things
present in a "context" which is used between Target and source Enodeb during Multi-Target RRC
connection re-estb. procedure?

Many Thanks !!
Reply

Anonymous May 27, 2016 at 6:49 PM

Hi Kumar Swamy , i need to know if the srvcc Get failed due to some reaon and then the reestablishment
has been occured , how to know only from the UU TRace that QCI 1 get estalished after the
reestablishment complete . i can see Invite message of QCI5 after the re-establishment and in the RRC
Reconfiguration there is no information related to Dedicated bearer and RLC UM . would these hints can
confirm that qci1 did nt get established after the reestablishment or to get a full pic we required S1 trace
also . Please your help on this case
Reply

david September 13, 2016 at 1:20 PM

In RRC connection reestablishment, Is the SN is required to resume SRB1 config in AM mode to resume
configuration?
Reply

Anonymous January 30, 2017 at 7:24 PM

Hi KSP,
What is the significance of :
A) ReestablishmentInfo &
B) AdditionalReestabInfoList ::= SEQUENCE ( SIZE (1..maxReestabInfo) ) OF AdditionalReestabInfo

in AS CONTEXT of HO PREP message which is sent by src ENB to target eNB.

Thank You!!
Reply

Replies

Kumara Swamy February 23, 2017 at 11:58 AM

The ReestablishmentInfo IE contains information needed for a potential re-establishment to
succeed in the target cell i.e., when the Handover fails and if the UE initiates Re-
estatblishment procedure on the target cell.

Reply

Shiva March 2, 2017 at 2:56 AM

Are multiple RREs possible during T301?. My understanding it upon sending RRE to the eNB, UE will
start T301 timer then it can expect the following 3 before going to idle mode as per 3GPP.
a) RRE from eNB
b) RRE Reject from eNB U
c) Nothing from eNB
T301 stops when a) or b) received by UE. In case of a) UE will carry on with RRE EST procedure. In case
of b) Will the UE retry another RRE with the new T301???
In case C) after T301 timer expiry UE will go to idle mode.
Also I would like to know in what condition UE will send > 1 RRE to the enb??

Thanks in Advance
Reply

Replies

Unknown October 23, 2018 at 4:56 PM

This comment has been removed by the author.

Reply

Munzir February 2, 2018 at 5:54 PM

Is there any factor which decides whether UE will send RRC Re-establishment request to source cell or
target target cell?
Thanks
Reply

Replies

Munzir February 5, 2018 at 2:43 PM

Awaiting your response

Kumara Swamy March 4, 2018 at 9:57 AM

Sorry for the delayed response. As you mentioned Target cell, I assume here that the UE is
initiating RRC Connection Re-establishment procedure due "Handover Failure". In any case,
as soon as this procedure is initiated, UE performs cell selection and it sends RRC Connection
Re-establishment message to the cell it has cell selected, be it is source cell, target cell or
could be any other cell.

Hope this helps.

Reply

aaaa May 8, 2018 at 3:47 PM

It will be great if anyone can help on our specific case: We are having 2 different PLMN (equivalent
PLMN), MME / core network is different. Now when UE try reestablishment from one PLMN cell to
another PLMN cell, it sis always fail (both for data and VoLTE). PLMN1_Site and PLMN2 site is having X2
definition. When we trace to check failure found as example: UE trigger reestablishment from PLMN2 cell
to PLMN1 cell. PLMN1 eNB sent context_fetch request to PLMN-2 eNB. PLMN-2 eNB send
context_fetch response, but not getting in PLMN1-ENB from trace. Then after timer expiry PLMN1-Node
sent reestablishment reject. Any idea, is this happening due to different MME?

Reply

Khan June 3, 2018 at 2:35 AM

Hi...can you please explain how a VoLTE call is saved after a RRC drop..for example we see RRC drop
during a VoLTE call, there is an interruption in RTP packets..the UE does RRC Re-establishment on
another cell but fails..and there is a drop..the UE initiates another RRC connection and then the
dedicated bearer is setup on the new enb....how does the new enb know the UE was having a VoLTE
Call session ?
Reply

pemainayam.net June 26, 2018 at 11:01 PM

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Reply

yeshwanth August 16, 2018 at 1:19 PM

RRC reestablishment happens due to

-> Radio Link Failure.

-> Handover Failure.
-> Reconfiguration Failure.
-> Integrity Failure.

1Q)Does UE goes for RACH of all these cases or only for RLF.

2Q)Actually what makes UE get RLF.

Handover / (Failure) case:

3Q)Is there any possibility during handover UE might fail to do RACH with target.
Actually during HO ,target provides rach dedicated config.So if RACH fails ,then will it send
reestablishment to target or source or other.
What was the behaviour ?

4Q)Will ue has to do reestablishment with only source,any possibility of sending to other cell(target or
other).

5Q)Are there any messages between eNB's to forward during reestablishment rejection cases (which
version>10.5/message in 36331 specifies).

My doubt :

1) Except RLF ,for other cases still UE was in connected mode only,so we can derive crnti & pcell from ue
context &
forward the reestablishment request.

2) If we need to go for RACH of all the cases ,to which eNB will UE sends RACH & reestablishment
request.
How it derives crnti & pcell to include it onto reestablishment request.

3) what if during HO , TS1RELOCOverall_timer_id & TX2RELOCoverall_id expires before Source (/any

cell) receives reestablishment request.

3) What is the significance of mobility during these situations.

P.S :- Please correct me ,if any of my question or assumption was wrong.

Reply

Unknown November 7, 2019 at 10:21 AM

Why UE initiate the reestablishment request after security activation because if radio link failure can be
detected before reception of Security configuration from network
Reply

Unknown May 26, 2020 at 6:57 PM

Hello
Kindly set information with layer wise
Like
L3 RRC NAS
L2 PDCP RLC MAC,
L1 PHYSICAL
Your content is Good easily under stand if possible please provide step by step
If possible can share LTE and 5NR Notes on my mail singhanshu758@gmail.com

Thanks

Reply

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