5.3.8 RRC connection release

36.3313GPPEvolved Universal Terrestrial Radio Access (E-UTRA)Protocol specificationRadio Resource Control (RRC)Release 15TS

5.3.8.1 General

Figure 5.3.8.1-1: RRC connection release, successful

The purpose of this procedure is:

– to release the RRC connection, which includes the release of the established radio bearers as well as all radio resources; or

– to suspend the RRC connection for both suspended RRC connection or RRC_INACTIVE, which includes the suspension of the established radio bearers;

– to complete the UP-EDT procedure, which includes the release or suspension of the established radio bearers.

5.3.8.2 Initiation

E-UTRAN initiates the RRC connection release procedure to a UE in RRC_CONNECTED or in RRC_INACTIVE or to complete UP-EDT.

5.3.8.3 Reception of the RRCConnectionRelease by the UE

The UE shall:

1> except for NB-IoT, BL UEs or UEs in CE, delay the following actions defined in this clause 60 ms from the moment the RRCConnectionRelease message was received or optionally when lower layers indicate that the receipt of the RRCConnectionRelease message has been successfully acknowledged, whichever is earlier;

1> for BL UEs or UEs in CE, delay the following actions defined in this clause 1.25 seconds from the moment the RRCConnectionRelease message was received or optionally when lower layers indicate that the receipt of the RRCConnectionRelease message has been successfully acknowledged, whichever is earlier;

1> for NB-IoT, delay the following actions defined in this clause 10 seconds from the moment the RRCConnectionRelease message was received or optionally when lower layers indicate that the receipt of the RRCConnectionRelease message has been successfully acknowledged, whichever is earlier.

NOTE: For BL UEs, UEs in CE and NB-IoT, when STATUS reporting, as defined in TS 36.322 [7], has not been triggered and the UE has sent positive HARQ feedback (ACK), as defined in TS 36.321 [6], the lower layers can be considered to have indicated that the receipt of the RRCConnectionRelease message has been successfully acknowledged.

1> stop T380, if running;

1> if the RRCConnectionRelease message is received in response to an RRCConnectionResumeRequest for EDT:

2> indicate to upper layers that the suspended RRC connection has been resumed;

2> discard the stored UE AS context and resumeIdentity;

2> stop timer T300;

2> stop timer T302, if running;

2> stop timer T303, if running;

2> stop timer T305, if running;

2> stop timer T306, if running;

2> stop timer T308, if running;

2> perform the actions as specified in 5.3.3.7;

2> stop timer T320, if running;

2> stop timer T322, if running;

1> if AS security is not activated and if UE is connected to 5GC:

2> ignore any field included in RRCConnectionRelease message except waitTime;

2> perform the actions upon leaving RRC_CONNECTED or RRC_INACTIVE as specified in 5.3.12 with the release cause ‘other’ upon which the procedure ends;

1> if the RRCConnectionRelease message includes redirectedCarrierInfo indicating redirection to geran; or

1> if the RRCConnectionRelease message includes idleModeMobilityControlInfo including freqPriorityListGERAN:

2> if AS security has not been activated; and

2> if upper layers indicate that redirect to GERAN without AS security is not allowed:

3> ignore the content of the RRCConnectionRelease;

3> perform the actions upon leaving RRC_CONNECTED or RRC_INACTIVE as specified in 5.3.12, with release cause ‘other’, upon which the procedure ends;

1> if AS security has not been activated:

2> ignore the content of redirectedCarrierInfo, if included and indicating redirection to nr;

2> ignore the content of idleModeMobilityControlInfo, if included and including freqPriorityListNR;

2> if the UE ignores the content of redirectedCarrierInfo or of idleModeMobilityControlInfo:

3> perform the actions upon leaving RRC_CONNECTED as specified in 5.3.12, with release cause ‘other’, upon which the procedure ends;

1> if the RRCConnectionRelease message includes redirectedCarrierInfo indicating redirection to eutra and if UE is connected to 5GC:

2> if cn-Type is included:

3> after the cell selection, indicate the available CN Type(s) and the received cn-Type to upper layers;

NOTE 1: Handling the case if the E-UTRA cell selected after the redirection does not support the core network type specified by the cn-Type, is up to UE implementation.

1> if the RRCConnectionRelease message includes the idleModeMobilityControlInfo:

2> store the cell reselection priority information provided by the idleModeMobilityControlInfo;

2> if the t320 is included:

3> start timer T320, with the timer value set according to the value of t320;

1> else:

2> apply the cell reselection priority information broadcast in the system information;

1> if the RRCConnectionRelease message includes the measIdleConfig:

2> clear VarMeasIdleConfig and VarMeasIdleReport;

2> store the received measIdleDuration in VarMeasIdleConfig;

2> start T331 with the value of measIdleDuration;

2> if the measIdleConfig contains measIdleCarrierListEUTRA:

3> store the received measIdleCarrierListEUTRA in VarMeasIdleConfig;

3> start performing idle mode measurements as specified in 5.6.20;

NOTE 2: If the measIdleConfig does not contain measIdleCarrierListEUTRA, UE may receive measIdleCarrierListEUTRA as specified in 5.2.2.12.

1> for NB-IoT, if the RRCConnectionRelease message includes the redirectedCarrierInfo:

2> if the redirectedCarrierOffsetDedicated is included in the redirectedCarrierInfo:

3> store the dedicated offset for the frequency in redirectedCarrierInfo;

3> start timer T322, with the timer value set according to the value of T322 in redirectedCarrierInfo;

1> if the releaseCause received in the RRCConnectionRelease message indicates loadBalancingTAURequired:

2> perform the actions upon leaving RRC_CONNECTED as specified in 5.3.12, with release cause ‘load balancing TAU required’;

1> else if the releaseCause received in the RRCConnectionRelease message indicates cs-FallbackHighPriority:

2> perform the actions upon leaving RRC_CONNECTED as specified in 5.3.12, with release cause ‘CS Fallback High Priority’;

1> else:

2> if the extendedWaitTime is present; and

2> if the UE supports delay tolerant access or the UE is a NB-IoT UE:

3> forward the extendedWaitTime to upper layers;

2> if the extendedWaitTime-CPdata is present and the NB-IoT UE only supports the Control Plane CIoT EPS optimisation:

3> forward the extendedWaitTime-CPdata to upper layers;

2> if the releaseCause received in the RRCConnectionRelease message indicates rrc-Suspend:

3> perform the actions upon leaving RRC_CONNECTED as specified in 5.3.12, with release cause ‘RRC suspension’;

2> else if rrc-InactiveConfig is included:

3> perform the actions upon entering RRC_INACTIVE as specified in 5.3.8.7;

2> else:

3> perform the actions upon leaving RRC_CONNECTED or RRC_INACTIVE as specified in 5.3.12, with release cause ‘other’;

5.3.8.4 T320 expiry

The UE shall:

1> if T320 expires:

2> if stored, discard the cell reselection priority information provided by the idleModeMobilityControlInfo or inherited from another RAT;

2> apply the cell reselection priority information broadcast in the system information;

5.3.8.5 T322 expiry or stop

The UE shall:

1> if T322 expires or is stopped:

2> discard the redirectedCarrierOffsetDedicated provided in RRCConnectionRelease message;

5.3.8.6 UE actions upon receiving the expiry of DataInactivityTimer

Upon receiving the expiry of DataInactivityTimer from lower layers while in RRC_CONNECTED, the UE shall:

1> perform the actions upon leaving RRC_CONNECTED as specified in 5.3.12, with release cause ‘RRC connection failure’;

5.3.8.7 UE actions upon entering RRC_INACTIVE

Upon entering RRC_INACTIVE, the UE shall:

1> reset MAC and release the default MAC configuration if any;

1> stop all timers that are running except T302, T309, T320, T325 and T330;

1> re-establish RLC entities for all SRBs and DRBs;

1> if the RRCConnectionRelease message is including the waitTime:

2> start timer T302, with the timer value set according to the waitTime;

2> inform the upper layer that access barring is applicable for all access categories except categories ‘0’ and ‘2’;

1> if T309 is running:

2> stop timer T309 for all access categories;

2> perform the actions as specified in 5.3.16.4.

1> apply the received rrc-InactiveConfig;

1> if the RRCConnectionRelease message was received in response to an RRCConnectionResumeRequest:

2> in the stored UE Inactive AS context:

3> replace the KeNB and KRRCint keys with the current KeNB and KRRCint keys;

3> replace the C-RNTI with the temporary C-RNTI which the UE has used to receive the RRCConnectionRelease message;

3> replace the cellIdentity with the cellIdentity of the PCell at the time the UE has received the RRCConnectionRelease message;

3> replace the previously stored physical cell identity with the physical cell identity of the PCell at the time the UE has received the RRCConnectionRelease message;

1> else:

2> store in the UE Inactive AS Context, the current KeNB and KRRCint keys, the ROHC state, the stored QoS flow to DRB mapping rules, the C-RNTI used in the source PCell, the cellIdentity and the physical cell identity of the source PCell, and all other parameters configured;

1> if the periodic-RNAU-timer is included:

2> start timer T380, with the timer value set to the periodic-RNAU-timer;

1> suspend all SRB(s) and DRB(s), except SRB0;

1> indicate PDCP suspend to lower layers of all DRBs;

1> indicate the suspension of the RRC connection to upper layers;

1> enter RRC_INACTIVE and perform procedures as specified in TS 36.304 [4], clause 5.2.7;

Upon selecting to an inter-RAT cell or switching to another CN type, the UE shall:

1> perform the actions upon leaving RRC_INACTIVE as specified in 5.3.12, with release cause ‘other’;