My Intra-NR Notes - Revision history

Paul: /* 9.2.1 Mobility in RRC_IDLE */

2022-11-27T21:54:14Z

9.2.1 Mobility in RRC_IDLE

← Older revision		Revision as of 16:54, 27 November 2022
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	** The UE searches the NR frequency bands and for each carrier frequency identifies the strongest cell as per the CD-SSB. It then reads cell system information broadcast to identify its PLMN(s):		** The UE searches the NR frequency bands and for each carrier frequency identifies the strongest cell as per the CD-SSB. It then reads cell system information broadcast to identify its PLMN(s):
	*** The UE may search each carrier in turn ("initial cell selection") or make use of stored information to shorten the search ("stored information cell selection").		*** The UE may search each carrier in turn ("initial cell selection") or make use of stored information to shorten the search ("stored information cell selection").
	* The UE seeks to identify a suitable cell; if it is not able to identify a suitable cell it seeks to identify an acceptable cell. When a suitable cell is found or if only an acceptable cell is found it camps on that cell and commence the cell reselection procedure:		* The UE seeks to identify a suitable cell; if it is not able to identify a suitable cell it seeks to identify an acceptable cell. <span style="color:red">When a suitable cell is found or if only an acceptable cell is found it camps on that cell and commence the cell reselection procedure</span>:
	** A suitable cell is one for which the measured cell attributes satisfy the cell selection criteria; the cell PLMN is the selected PLMN, registered or an equivalent PLMN; the cell is not barred or reserved and the cell is not part of a tracking area which is in the list of "forbidden tracking areas for roaming";		** A suitable cell is one for which the measured cell attributes satisfy the cell selection criteria; the cell PLMN is the selected PLMN, registered or an equivalent PLMN; the cell is not barred or reserved and the cell is not part of a tracking area which is in the list of "forbidden tracking areas for roaming";
	** An acceptable cell is one for which the measured cell attributes satisfy the cell selection criteria and the cell is not barred.		** An acceptable cell is one for which the measured cell attributes satisfy the cell selection criteria and the cell is not barred.

Paul: /* 9.2.2.4.1 UE triggered transition from RRC_INACTIVE to RRC_CONNECTED */

2022-11-02T21:44:51Z

9.2.2.4.1 UE triggered transition from RRC_INACTIVE to RRC_CONNECTED

← Older revision		Revision as of 16:44, 2 November 2022
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	:6. A new connection is setup as described in clause 9.2.1.3.		:6. A new connection is setup as described in clause 9.2.1.3.

	The following figure describes the rejection ~~form~~ the network when the UE attempts to resume a connection from RRC_INACTIVE:		The following figure describes the rejection from the network when the UE attempts to resume a connection from RRC_INACTIVE:

	<center>[[File:Reject from the network, UE attempts to resume a connection.png\|Reject from the network, UE attempts to resume a connection]]</center>		<center>[[File:Reject from the network, UE attempts to resume a connection.png\|Reject from the network, UE attempts to resume a connection]]</center>

Paul: /* 9.2.2.1 Overview */

2022-11-02T21:20:57Z

9.2.2.1 Overview

← Older revision		Revision as of 16:20, 2 November 2022
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	RRC_INACTIVE is a state where a UE remains in CM-CONNECTED and can move within an area configured by NG-RAN, the RAN-based Notification Area (RNA), without notifying NG-RAN. In RRC_INACTIVE, the last serving gNB node keeps the UE context and the UE-associated NG connection with the serving AMF and UPF.		RRC_INACTIVE is a state where a UE remains in CM-CONNECTED and can move within an area configured by NG-RAN, the RAN-based Notification Area (RNA), without notifying NG-RAN. In RRC_INACTIVE, the last serving gNB node keeps the UE context and the UE-associated NG connection with the serving AMF and UPF.

			If the last serving gNB receives DL data from the UPF or DL UE-associated signalling from the AMF (except the UE Context Release Command message) while the UE is in RRC_INACTIVE, it pages in the cells corresponding to the RNA and may send XnAP RAN Paging to neighbour gNB(s) if the RNA includes cells of neighbour gNB(s).

			Upon receiving the UE Context Release Command message while the UE is in RRC_INACTIVE, the last serving gNB may page in the cells corresponding to the RNA and may send XnAP RAN Paging to neighbour gNB(s) if the RNA includes cells of neighbour gNB(s), in order to release UE explicitly.

			Upon receiving the NG RESET message while the UE is in RRC_INACTIVE, the last serving gNB may page involved UEs in the cells corresponding to the RNA and may send XnAP RAN Paging to neighbour gNB(s) if the RNA includes cells of neighbour gNB(s) in order to explicitly release involved UEs.

			Upon RAN paging failure, the gNB behaves according to TS 23.501.

			The AMF provides to the NG-RAN node the Core Network Assistance Information to assist the NG-RAN node's decision whether the UE can be sent to RRC_INACTIVE, and to assist UE configuration and paging in RRC_INACTIVE. The Core Network Assistance Information includes the registration area configured for the UE, the Periodic Registration Update timer, and the UE Identity Index value, and may include the UE specific DRX, an indication if the UE is configured with Mobile Initiated Connection Only (MICO) mode by the AMF, the Expected UE Behaviour, the UE Radio Capability for Paging, the PEI with Paging Subgrouping assistance information and the NR Paging eDRX Information and Paging Cause Indication for Voice Service. The UE registration area is taken into account by the NG-RAN node when configuring the RNA. The UE specific DRX and UE Identity Index value are used by the NG-RAN node for RAN paging. The Periodic Registration Update timer is taken into account by the NG-RAN node to configure Periodic RNA Update timer. The NG-RAN node takes into account the Expected UE Behaviour to assist the UE RRC state transition decision. The NG-RAN node may use the UE Radio Capability for Paging during RAN Paging. The NG-RAN node takes into account the PEI with Paging Subgrouping assistance information for subgroup paging in RRC_INACTIVE. When sending the XnAP RAN Paging to neighbour NG-RAN node(s), the PEI with Paging Subgrouping assistance information may be included. The NG-RAN node takes into account the NR Paging eDRX Information to configure the RAN Paging when the NR UE is in RRC_INACTIVE. When sending XnAP RAN Paging to neighbour NG-RAN node(s), the NR Paging eDRX Information for RRC_IDLE and for RRC_INACTIVE may be included. The NG-RAN node takes into consideration the Paging Cause Indication for Voice Service to include the Paging Cause in RAN Paging for a UE in RRC_INACTIVE state. When sending XnAP RAN Paging to neighbour NG-RAN node(s), the Paging Cause may be included.

			At transition to RRC_INACTIVE the NG-RAN node may configure the UE with a periodic RNA Update timer value. At periodic RNA Update timer expiry without notification from the UE, the gNB behaves as specified in TS 23.501.

			If the UE accesses a gNB other than the last serving gNB, the receiving gNB triggers the XnAP Retrieve UE Context procedure to get the UE context from the last serving gNB and may also trigger an Xn-U Address Indication procedure including tunnel information for potential recovery of data from the last serving gNB. Upon successful UE context retrieval, the receiving gNB shall perform the slice-aware admission control in case of receiving slice information and becomes the serving gNB and it further triggers the NGAP Path Switch Request and applicable RRC procedures. After the path switch procedure, the serving gNB triggers release of the UE context at the last serving gNB by means of the XnAP UE Context Release procedure.

			In case the UE is not reachable at the last serving gNB, the gNB shall fail any AMF initiated UE-associated class 1 procedure which allows the signalling of unsuccessful operation in the respective response message. It may trigger the NAS Non Delivery Indication procedure to report the non-delivery of any non PDU Session related NAS PDU received from the AMF as specified in TS 38.413.

			If the UE accesses a gNB other than the last serving gNB and the receiving gNB does not find a valid UE Context, the receiving gNB can perform establishment of a new RRC connection instead of resumption of the previous RRC connection. UE context retrieval will also fail and hence a new RRC connection needs to be established if the serving AMF changes.

			A UE in the RRC_INACTIVE state is required to initiate RNA update procedure when it moves out of the configured RNA. When receiving RNA update request from the UE, the receiving gNB triggers the XnAP Retrieve UE Context procedure to get the UE context from the last serving gNB and may decide to send the UE back to RRC_INACTIVE state, move the UE into RRC_CONNECTED state, or send the UE to RRC_IDLE. In case of periodic RNA update, if the last serving gNB decides not to relocate the UE context, it fails the Retrieve UE Context procedure and sends the UE back to RRC_INACTIVE, or to RRC_IDLE directly by an encapsulated ''RRCRelease'' message.

	=== 9.2.2.2 Cell Reselection ===		=== 9.2.2.2 Cell Reselection ===

Paul: /* 9.2.2.4.1 UE triggered transition from RRC_INACTIVE to RRC_CONNECTED */

2022-11-02T20:00:57Z

9.2.2.4.1 UE triggered transition from RRC_INACTIVE to RRC_CONNECTED

← Older revision		Revision as of 15:00, 2 November 2022
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	: 9. The gNB triggers the release of the UE resources at the last serving gNB.		: 9. The gNB triggers the release of the UE resources at the last serving gNB.

	After step 1 above, when the gNB decides to use a single RRC message to reject the Resume Request right away and keep the UE in RRC_INACTIVE without any reconfiguration (e.g. as described in the two examples below), or when the gNB decides to setup a new RRC connection, SRB0 (without security) is used. Conversely, when the gNB decides to reconfigure the UE (e.g. with a new DRX cycle or RNA) or when the gNB decides to push the UE to RRC_IDLE, SRB1 (with integrity protection and ciphering as previously configured for that SRB) shall be used.		After step 1 above, when the gNB decides to use a single RRC message to reject the Resume Request right away and keep the UE in RRC_INACTIVE without any reconfiguration (e.g. as described in the two examples below), or when the gNB decides to setup a new RRC connection, SRB0 (without security) is used. Conversely, when the gNB decides to reconfigure the UE (e.g. with a new Discontinuous Reception (DRX) cycle or RNA) or when the gNB decides to push the UE to RRC_IDLE, SRB1 (with integrity protection and ciphering as previously configured for that SRB) shall be used.

	NOTE: SRB1 can only be used once the UE Context is retrieved i.e. after step 3.		NOTE: SRB1 can only be used once the UE Context is retrieved i.e. after step 3.

Paul: /* 9.2.1.3 RRC_IDLE State Transitions */

2022-11-02T19:23:01Z

9.2.1.3 RRC_IDLE State Transitions

← Older revision		Revision as of 14:23, 2 November 2022
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	:1. UE attempts to setup a new connection from RRC_IDLE.		:1. UE attempts to setup a new connection from RRC_IDLE.
	:2. The gNB is not able to handle the procedure, for instance due to congestion.		:2. The gNB is not able to handle the procedure, for instance due to congestion.
	:3. The gNB sends RRCReject (with a wait time) to keep the UE in RRC_IDLE.		:3. The gNB sends ''RRCReject'' (with a wait time) to keep the UE in RRC_IDLE.

	== 9.2.2 Mobility in RRC_INACTIVE ==		== 9.2.2 Mobility in RRC_INACTIVE ==

Paul: /* 9.2.1.3 RRC_IDLE State Transitions */

2022-11-02T19:09:02Z

9.2.1.3 RRC_IDLE State Transitions

← Older revision		Revision as of 14:09, 2 November 2022
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	: 2/2a. The gNB completes the RRC setup procedure.		: 2/2a. The gNB completes the RRC setup procedure.
	: NOTE: The scenario where the gNB rejects the request is described below.		: NOTE: The scenario where the gNB rejects the request is described below.
	: 3. The first NAS message from the UE, piggybacked in RRCSetupComplete, is sent to AMF.		: 3. The first NAS message from the UE, piggybacked in ''RRCSetupComplete'', is sent to AMF.
	: 4/4a/5/5a. Additional NAS messages may be exchanged between UE and AMF, see TS 23.502.		: 4/4a/5/5a. Additional NAS messages may be exchanged between UE and AMF, see TS 23.502.
	: 6. The AMF prepares the UE context data (including PDU session context, the Security Key, UE Radio Capability and UE Security Capabilities, etc.) and sends it to the gNB.		: 6. The AMF prepares the UE context data (including PDU session context, the Security Key, UE Radio Capability and UE Security Capabilities, etc.) and sends it to the gNB.

Paul: /* 9.2.1.3 RRC_IDLE State Transitions */

2022-11-02T18:20:02Z

9.2.1.3 RRC_IDLE State Transitions

← Older revision		Revision as of 13:20, 2 November 2022
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	=== 9.2.1.3 RRC_IDLE State Transitions ===		=== 9.2.1.3 RRC_IDLE State Transitions ===

	The following figure describes the UE triggered transition from RRC_IDLE to RRC_CONNECTED (for the NAS part, see TS 23.502):		The following figure describes the UE triggered transition from RRC_IDLE to RRC_CONNECTED (<span style="color:red">for the NAS part, see TS 23.502</span>):

	<center>[[File:UE triggered transition from RRC IDLE to RRC CONNECTED.png\|UE triggered transition from RRC IDLE to RRC CONNECTED sequence diagram]]</center>		<center>[[File:UE triggered transition from RRC IDLE to RRC CONNECTED.png\|UE triggered transition from RRC IDLE to RRC CONNECTED sequence diagram]]</center>

Paul: /* 9.2.1.2 Cell Reselection */

2022-11-02T18:18:48Z

9.2.1.2 Cell Reselection

← Older revision		Revision as of 13:18, 2 November 2022
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	=== 9.2.1.2 Cell Reselection ===		=== 9.2.1.2 Cell Reselection ===

	A UE in RRC_IDLE performs cell reselection. The principles of the procedure are the following:		<span style="color:red">A UE in RRC_IDLE performs cell reselection.</span> The principles of the procedure are the following:
	* Cell reselection is always based on CD-SSBs located on the synchronization raster (see clause 5.2.4).		* Cell reselection is always based on CD-SSBs located on the synchronization raster (see clause 5.2.4).
	* The UE makes measurements of attributes of the serving and neighbour cells to enable the reselection process:		* The UE makes measurements of attributes of the serving and neighbour cells to enable the reselection process:

Paul: /* 9.2.1.1 Cell Selection */

2022-11-02T18:18:10Z

9.2.1.1 Cell Selection

← Older revision		Revision as of 13:18, 2 November 2022
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	Transition to RRC_IDLE:		Transition to RRC_IDLE:
	* On transition from RRC_CONNECTED or RRC_INACTIVE to RRC_IDLE, a UE should camp on a cell as result of cell selection according to the frequency be assigned by RRC in the state transition message if any.		* <span style="color:red">On transition from RRC_CONNECTED or RRC_INACTIVE to RRC_IDLE, a UE should camp on a cell as result of cell selection according to the frequency be assigned by RRC in the state transition message if any.</span>

	Recovery from out of coverage:		Recovery from out of coverage:

Paul: /* 9.2.1 Mobility in RRC_IDLE */

2022-11-02T18:05:28Z

9.2.1 Mobility in RRC_IDLE

← Older revision		Revision as of 13:05, 2 November 2022
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	=== 9.2.1.1 Cell Selection ===		=== 9.2.1.1 Cell Selection ===

	The principles of PLMN selection in NR are based on the 3GPP PLMN selection principles. Cell selection is required on transition from RM-DEREGISTERED to RM-REGISTERED, from CM-IDLE to CM-CONNECTED and from CM-CONNECTED to CM-IDLE and is based on the following principles:		The principles of PLMN selection in NR are based on the 3GPP PLMN selection principles. <span style="color:red">Cell selection</span> is required on transition from RM-DEREGISTERED to RM-REGISTERED, from CM-IDLE to CM-CONNECTED and from CM-CONNECTED to CM-IDLE and is based on the following principles:

	* The UE NAS layer identifies a selected PLMN and equivalent PLMNs;		* The UE NAS layer identifies a selected PLMN and equivalent PLMNs;