释放流程及异常原因分析V2ppt课件

1、释放流程及异常释放缘由分析2021-05张恒概述主要内容阐明本次主要讨论的内容：LTE业务释放类型及相应信令流程的详解；相关的counter触发定义，以及异常问题分析；经过对这些内容的梳理和讨论，可以了解LTE释放的实际知识，并且在日常KPI和Log分析方面，提供协助。释放流程及异常释放缘由分析主要内容业务承载类型及业务建立过程业务释放类型及相应流程、缘由E-RAB releaseUE context releaseRRC connection release异常释放的触发情景详解UE initiated dropeNB initiated drop异常释放related Counter Tr

2、iggersNetwork/Field KPI及Drops分析Summary业务承载类型LTE业务承载类型LTE的业务承载类型分为默许承载、公用承载两种：默许承载：UE开机时获得承载，一定是MME发起的业务，优先级特别低，Non GBR；公用承载：一定是由PGW触发建立的；一个UE可以有不同的公用承载；GTP variant: EPS bearer termination in PGWSRB与默许、公用承载关系业务承载类型无线承载分类SRB Signalling Radio BearersSRBs的定义是，仅用于传输RRC和NAS音讯的RBRadio Bearer；DRB Data Radio

3、 Bearer，用于传输业务数据的无线承载；与S1-U承载共同组成E-RAB.分为UM、AM两种；业务承载类型UE context及E-RABE-RAB UE至SGW之间的承载，E-RAB是指用户平面的承载，由S1-U承载和DRBData Radio Bearer，数据无线承载串联而成，进入LTE系统的业务数据主要经过E-RAB进展传输。因此对于LTE，业务管理主要是在E-RAB层次上进展的。 一个UE可以有多个E-RAB，目前最多支持8个EPS承载个AM DRB，3个UM DRB. 在运用上，E-RAB常出现于性能目的的统计中，例如：E-RAB建立胜利率。E-RAB建立胜利指eNodeB胜利

4、为UE分配了通讯通道的无线资源和用户面的无线承载，所以这个目的反映了eNodeB或小区接纳业务的才干，可以用来思索系统负荷情况。业务承载类型UE context及E-RABUE context Including E-RAB context, security context, roaming restriction, UE S1 signalling connection ID(s), etc. in the eNB.在源eNB的UE上下文中还包含了与遨游和接入限制有关的信息； Initial UE context只能由MME发起，一个UE只需一个UE context； 一个eNB UE c

5、ontext是eNB内和一个处于激活形状的UE相关联的一个信息块。这块信息是为了维持E-UTRAN提供应这个激活态UE的效力所必需的信息； eNB UE context是在UE迁移到激活形状之后开场建立的；或者，eNB UE context是在切换目的eNB完成切换资源分配切换预备阶段之后开场建立的。 RRC connection 层三信令衔接，UE坚持非IDLE的必需衔接，一个UE只需一个RRC connection，一旦衔接释放，UE一切业务释放，并进入RRC_IDLE态；LTE完好业务流程默许承载建立信令流程AttachSteps:Random AccessInitial NAS msg

6、NAS securityS1 init setupRRC sec + UE capSRB2/DRB setupNAS replyLTE完好业务流程RA及RRC衔接建立流程SRB0：RRC connection request、RRC connection setup音讯中包含SRB1建立的相关信息；SRB1：RRC connection setup complete；LTE完好业务流程公用承载建立流程Dedicated Bearer Establishment：E-RAB建立释放流程及异常释放缘由分析主要内容业务承载类型及业务建立过程业务释放类型及相应流程、缘由E-RAB releaseUE

7、context releaseRRC connection releaseAbnormal release的触发情景详解UE initiated dropeNB initiated drop异常释放related Counter TriggersNetwork/Field KPI及Drops分析Summary业务释放类型release 根据业务承载类型，业务释放过程也分为三类：E-RAB releaseThe purpose of the E-RAB Release procedure is to enable the release of already established E-RABs

8、 for a given UE；E-RAB释放后，UE依然可以处于ECM-CONNECTED形状；UE context releaseIf the eNB wants to remove all remaining E-RABs, e.g., for user inactivity, the UE Context Release Request procedure shall be used instead.当UE回到ECM-IDLE形状时，MME向eNodeB发UE CONTEXT RELEASE音讯。收到这条音讯后，eNodeB删除eNB UE context。MME继续保管MME UE

9、context.业务释放类型release 根据业务承载类型，业务释放过程也分为两类：RRC connection releaseThe 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；RRC衔接释放后，UE进入RRC_IDLE形状。E-RAB release释放类型：E-RAB release 根据3GPP定义(3GPP TS 36.413)

10、，E-RAB release过程分为两大类：ENodeB InitiatedMME InitiatedE-RAB管理的相关信息都embed在context管理信令中。MME InitiatedENodeB Initiated释放流程信令详解E-RAB release ：MME InitiatedE-RAB release command音讯内容：shall contain the information required by the eNB to release at least one E-RAB in the E-RAB To Be Released List IE. If a NAS-

11、PDU IE is contained in the message, the eNB shall pass it to the UE.E-RAB To Be Released List IE. the UE Aggregate Maximum Bit Rate IE.E-RAB release response音讯内容：- A list of E-RABs which are released successfully shall be included in the E-RAB Release List IE.- A list of E-RABs which failed to be re

12、leased, if any, shall be included in the E-RAB Failed to Release List IE.释放流程信令详解E-RAB release ：MME InitiatedeNB收到E-RAB RELEASE COMMAND后，eNB将会释放被恳求的ERABs. 对于每一个要释放的E-RAB，eNB会释放其相应的DRB和空口资源。The eNB shall pass the value contained in the E-RAB ID IE received for the E-RAB to the radio interface protoco

13、l for each Data Radio Bearer to be released. The eNB shall release allocated resources on S1 for the E-RABs requested to be released.Network triggered (from Delete Bearer)释放流程信令详解E-RAB release ：eNB InitiatedE-RAB RELEASE INDICATION音讯内容：The E-RAB RELEASE INDICATION message shall contain at least one

14、E-RAB released at the eNB, in the E-RAB Released List IE.Upon reception of the E-RAB RELEASE INDICATION message the MME shall normally initiate the appropriate release procedure on the core network side for the E-RABs identified in the E-RAB RELEASE INDICATION message.Interaction with UE Context Rel

15、ease Request procedure:If the eNB wants to remove all remaining E-RABs, e.g., for user inactivity, the UE Context Release Request procedure shall be used instead.释放流程及异常释放缘由分析主要内容业务承载类型及业务建立过程业务释放类型及相应流程、缘由E-RAB releaseUE context releaseRRC connection releaseAbnormal release的触发情景详解UE initiated drope

16、NB initiated drop异常释放related Counter TriggersNetwork/Field KPI及Drops分析SummaryUE context release释放类型：UE context release根据3GPP定义(3GPP TS 36.413)，UE context过程同样分为两大类：ENodeB InitiatedMME InitiatedThis procedure is used to release the logical S1-AP signalling connection (over S1-MME) and all S1 bearers (

17、in S1-U) for a UE. The procedure will move the UE from ECM-CONNECTED to ECM-IDLE in both the UE and MME, and all UE related context information is deleted in the eNode B.UE context release释放的触发条件UE Context Release Request 该信令，使基站可以根据E-UTRAN的需求，向MME恳求UE-associated S1链接的释放； ENodeB发起的Context release情况：

18、Normal release：“User Inactivity，CS Fallback triggered，UE Not Available for PS Service，Inter-RAT Redirection，Time Critical Handover，Handover Cancelled，“DetachAbnormal release：“Radio Connection With UE Lost, “CSG Subscription Expiry, “Redirection towards 1xRTT，Unspecified Failure，O&M Intervention，Repe

19、ated RRC signalling Integrity Check Failure，etc.ENodeB InitiatedUE context release释放的触发条件UE Context Release CommandMME Initiated 该信令，使MME在多种情形下，可以控制UE-associated 链接的释放； MME发起的Context release情况：Normal release：e.g, completion of a transaction between the UE and the EPC, or completion of successful han

20、dover, or completion of handover cancellation, or release of the old UE-associated logical S1-connection when two UE-associated logical S1-connections toward the same UE is detected after the UE has initiated the establishment of a new UE-associated logical S1-connection, or the UE is no longer allo

21、wed to access the CSG cell(i.e., the UE becomes a non-member of the currently used CSG cell).Abnormal release： “Load Balancing TAU Required，authentication failure, detach, not allowed CSG celetc.UE context release正常释放缘由信令实例eNB initiatedMME initiatedMME initiatedeNB initiatedeNB initiatedUE context r

22、elease异常释放缘由信令实例MME initiatedeNB initiatedMME initiatedMME initiatedMME initiated释放流程信令详解UE context release：ENodeB InitiatedThe UE CONTEXT RELEASE REQUEST message shall indicate the appropriate cause value, e.g., “User Inactivity,“Radio Connection With UE Lost, “CSG Subscription Expiry, “CS Fallback

23、 triggered, “Redirection towards1xRTT, “Inter-RAT Redirection, “UE Not Available for PS Service, for the requested UE-associated logical S1-connection release.Interactions with UE Context Release procedure:The UE Context Release procedure should be initiated upon reception of a UE CONTEXT RELEASE RE

24、QUEST message.释放流程信令详解UE context release：ENodeB InitiatedTransition due to inavtivity.UE consumes less battery power in idle mode; Less active Ues which network has to handle; Fast going to inactivity has drawback of longer connection setup time(more transitions idle to connected).释放流程信令详解UE context

25、 release：ENodeB Initiated释放流程信令详解UE context release：MME InitiatedThe UE CONTEXT RELEASE COMMAND message shall contain the UE S1AP ID pair IE if available, otherwise the message shall contain the MME UE S1AP ID IE.The MME provides the cause IE set to “Load Balancing TAU Required in the UE CONTEXT REL

26、EASE COMMAND message sent to the eNB for all load balancing and offload cases in the MME.MME UE S1AP is released when the S1 connection is released (next time a newvalue is assigned) eNB UE S1AP is released释放流程信令详解UE context release：MME InitiatedUpon reception of the UE CONTEXT RELEASE COMMAND messa

27、ge, the eNB shall release all related signalling and user data transport resources and reply with the UE CONTEXT RELEASE COMPLETE message. In case of eNBsupporting L-GW function for LIPA operation, the eNB shall also release the node internal tunnel resources.释放流程信令详解UE context release：MME Initiated

28、释放流程信令详解UE context release：MME Initiated释放流程及异常释放缘由分析主要内容业务承载类型及业务建立过程业务释放类型及相应流程、缘由E-RAB releaseUE context releaseRRC connection releaseAbnormal release的触发情景详解UE initiated dropeNB initiated drop异常释放related Counter TriggersNetwork/Field KPI及Drops分析SummaryRRC connection release释放类型根据3GPP定义(3GPP TS 36

29、.331)，E-UTRAN initiates the RRC connection release procedure to a UE in RRC_CONNECTED：RRC connection releaseThe 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.RRC connection release requested by u

30、pper layersThe purpose of this procedure is to release the RRC connection. Access to the current PCell may be barred as a result of this procedure.RRC connection release释放缘由The release of the RRC connection is initiated by E-UTRAN. The procedure may be used to re-direct the UE to another frequency o

31、r RAT. In exceptional cases the UE may abort the RRC connection, i.e.move to RRC_IDLE without notifying E-UTRAN.释放流程及异常释放缘由分析主要内容业务承载类型及业务建立过程业务释放类型及相应流程、缘由E-RAB releaseUE context releaseRRC connection releaseAbnormal release的触发情景详解UE initiated dropeNB initiated drop异常释放related Counter TriggersNetwo

32、rk/Field KPI及Drops分析SummaryCall dropWho Initiates Drops, UE, MME or eNB? UE can initiate a drop by starting RRC Connection Re-establishmentNote: besides RLF also other causes can trigger RRC Conn Re-Establishment eNB can initiate abnormal S1 + RRC release due toRadio network layer problem (TA timer,

33、 RLF, PDCCH Order failure)Transport network layer problem (GTP-U error, Treloc expiry, Path Switch problem)Other abnormal cause MME can initiate abnormal S1 + RRC release due toRadio network layer problemOther abnormal causeUE initiated dropRLFWhen UE is in RRC_CONNECTED and RRC security is active,

34、it can trigger RRC Connection Re-establishmentupon T310 expiryupon reaching the maximum number of UL RLC retransmissionsupon handover failure (T304 expiry)upon non-HO related random access problemIf successful, RRC Conn Re-Establishment reconfigures SRB1 to resume data transfer of RRC msgsre-activat

35、es RRC security without changing algorithmsNOTE: DRB should be re-configured after SRB1 NOTE: if UE is in RRC_CONNECTED while RRC security is not active, UE goes to RRC_IDLE, performs cell reselection and TAUUE initiated dropRLF due to T310 Expiry at UEUE initiated dropRLF due to Maximum UL RLC Re-T

36、x Reachedfrom RRC Connection Reconfiguration:drb-ToAddModList drb-ToAddModList value 1 drb-Identity: 1 rlc-Config am ul-AM-RLC t-PollRetransmit: ms40 pollPDU: p32 pollByte: kB25 maxRetxThreshold: t8UE initiated dropRLF due to HO Failurefrom RRC Connection Reconfiguration: mobilityControlInfo targetP

37、hysCellId: 33 t304: ms1000 newUE-Identity Bin: 14 EB (= 5355)UE initiated dropRLF Due to Non-HO Random Access Failure“Non-HO random access meansPDCCH order -triggered RA Random Access Scheduling Request释放流程及异常释放缘由分析主要内容业务承载类型及业务建立过程业务释放类型及相应流程、缘由E-RAB releaseUE context releaseRRC connection releaseA

38、bnormal release的触发情景详解UE initiated dropeNB initiated drop异常释放related Counter TriggersNetwork/Field KPI及Drops分析SummaryeNB initiated dropRLF eNB can drop the call due to following triggers eNB-detected radio link problemsPUSCH RLFCQI RLFAck/Nack RLFPDCCH Order failureSRS RLFTA timer expiryMaximum RLC

39、retransmissions exceededGTP-U failureeNB initiated dropRadio Link Problem Detection at eNBeNB radio link problem detection mechanisms are NSN-internally specifiedMultiple methods (called “link monitors) are defined to detect a radio link problem in the eNB. When one link monitor detects a problem, i

40、t is really a radio link problem even if other link monitors have not yet indicated anything.Each link monitor has its internal criteria to decide when radio link problem is flagged and de-flagged (radio link recovers). If the RLP persists longer than T_RLF, RRC+S1 release is triggeredT_RLF = t310 +

41、 t311 (eNB-internal timer)Link monitors:Uplink PUSCH DTX detection for scheduled uplink dataCQI DTX detection for periodic CQI reports in PUCCH and PUSCHUplink Ack/Nack DTX detection for transmitted downlink data PDCCH Order RLFSRS DTX detection (TD-LTE)eNB initiated drop1. PUSCH RLF: RlsCause_Pusch

42、Rlf_ON When UE is scheduled for PUSCH transmission, eNB expects to receive UL transmission on the scheduled PRBsIf signal from UE cannot be detected at all, PUSCH DTX is declaredNOTE: The case where UL TBS is received but it fails CRC check is not DTX (its a NACK)DTX PUSCH indication is provided by

43、the UL physical layer.The result is received by LTE MAC in reliableULtransmissionFlag parameter.Both counter-based and timer-based RLF detection is supportedTimer-based PUSCH RLF detection:If “DTX“ is received on the PUSCH for a configurable period of time (rlpDetMaxTimeUl), PUSCH RLF is set onCount

44、er-based PUSCH RLF detection:If “DTX“ is received on the PUSCH for a consecutive number of times (rlpDetMaxNoUl), PUSCH RLF is set onThe recovery of the radio link is indicated when for a configurable number of contiguous UL resource assignments data is detected on PUSCH (ACK or NACK received). Defi

45、ned by parameter rlpDetEndNoUl.eNB initiated drop1. PUSCH RLF: RlsCause_PuschRlf, Counter-based RLF Detection Example T_RLF = T310 + T3113 2 vendor-file parameters in this example:eNB initiated drop2. Periodic CQI RLF: RlsCause_CqiRlf_ON The eNB supports CQI DTX detection for periodic CQI reports on

46、 PUCCH and PUSCH.If MAC layer receives nCqiDtx consecutive reports from UL PHY, the MAC declares CqiRLF_ON If the MAC has set CqiRLF_ON for a specific UE and nCqiRec consecutive CQI reports are again detected successfully for that UE, the MAC sets CqiRLF_OFFThe parameters nCqiDtx and nCqiRec are in

47、the vendor-specific parameter fileFor both PUSCH and PUCCH the periodic CQI is encoded using a Reed Muller block code and comes along without any CRC. Hence, the UL PHY indicates a DTX detection for periodic CQI reports on PUCCH or PUSCH whenever a report is configured but no reliable transmission f

48、rom the UE could be detected. So the output of the detector shall be either the detected CQI report or a DTX indication.NOTE: CQI_RLF detection does not apply to aperiodic CQI report on PUSCHeNB initiated drop2. Periodic CQI RLF: RlsCause_CqiRlf, Example 6 1 vendor-file parameters in this example:T_

49、RLF = T310 + T311eNB initiated drop3. Ack/Nack RLF: RlsCause_AckNackRlf_ONAfter DL scheduled data, eNB expects HARQ ACK or NACK on PUCCH or PUSCH at known UL TTITimer-based ACK/NACK RLF detection:If ACK/NACK “DTX“ is received for a configurable period of time (rlpDetMaxTimeDl), ACK/NACK RLF is set o

50、nCounter-based ACK/NACK RLF detection:If ACK/NACK “DTX“ is received for a consecutive number of times (rlpDetMaxNoDl), ACK/NACK RLF is set onThe recovery of the RLF is indicated when for a configurable number of contiguous ACK/NACK opportunities ACK or NACK is detected on PUSCH or PUCCH (no DTX). De

51、fined by parameter rlpDetEndNoDl. .eNB initiated drop4. PDCCH Order RLFIf there DL data in eNB buffer and UE is out-of-sync, UE must be brought back to in-sync (time aligned) with a RA procedure before DL data can be sent Signaling of dedicated RA preamble via PDCCH (so-called PDCCH order) is done u

52、sing DCI format 1A In case that PDCCH order fails for a UE (i.e., no transmission of assigned dedicated preamble detected by eNodeB, or no msg3 transmission) the PDCCH order shall be repeated noRepPdcchOrder times (R&D configurable parameter, range 0-3, default 1), again using the selected preamble

53、and considering DRX status of the UE accordingly. Final failure of the PDCCH order process shall be indicated as radio link problem to higher layers with cause “PDCCH order failure If inactivity timer for the UE has expired then there is no T_RLF timer involved S1 and RRC released immediatelyeNB ini

54、tiated drop5. SRS RLFThe eNB supports SRS DTX detection for radio link problem detectionIf MAC layer receives nSrsDtx consecutive reports from UL PHY, the MAC declares SRS RLFIf the MAC has set SRS RLF for a specific UE and nSrsRec consecutive SRS transmissions are succesfully detected the UE, the M

55、AC sets SRS RLF OFFHence the SRS RLF has similar mechanism as CQI DTX RLFThe parameters nSrsDtx and nSrsRec are operator-configurableP7 default values from RL15 SCF:8 1eNB initiated dropWhen is Drop (= RRC + S1 release) Triggered by eNB?3GPP does not specify eNB radio link failures, but NSN eNB mimi

56、cs the behaviour of the UE RLF specified in 3GPP.When a radio link problem is detected, an eNB-internal timer (T_RLF) is started. The timer T_RLF is stopped when in case of radio link failure recovery.For a given UE, T_RLF is started when any of the PUSCH RLF, CQI RLF, SRS RLF or AckNack RLF is set

57、to ON stateFor a given UE, T_RLF is stopped only if all RLFs are OFFWhen the timer T_RLF expires, the UE is released from the eNB using eNB initiated S1 release + RRC connection release call dropT_RLF = T310 + T311eNB initiated dropRLF Triggering by eNB, SignallingOnly L2 Ack needed for successful R

58、RC Conn Release. If L2 Ack not received after timer tL2AckRrcRel expires (def=800ms), RRC is released anyway. NOTE: No RLC Ack needed for RRC Connection Release. No reTx for RRC Connection ReleaseeNB initiated dropIn-Sync and Out-Of-Sync States: OverviewRRC connected substates: UL in-sync and UL out

59、-of-syncUplink RA SR or downlink PDCCH order to bring UE back in-synceNB initiated dropTA Timer Expiry at UEAs UE detects Out-of-Sync status using a Timing Alignment Timer, the timer shall be started or restarted whenever an initial TA or a TA update command is received (see 3GPP-36.321, section 5.2

60、). If the timer expires, the UE detects out-of-sync status.3GPP TS 36.321: When timeAlignmentTimer expires at UE, UE MAC layer shall:flush all HARQ buffers;notify RRC layer to release PUCCH/SRS;clear any configured downlink assignments and uplink grants3GPP TS 36.331: Upon receiving a PUCCH/ SRS rel