单击此处编辑母版标题样式,,单击此处编辑母版文本样式,,第二级,,第三级,,第四级,,第五级,,R 18 G 65 B 145,R 0 G 201 B 255,R 104 G 113 B 122,R 216 G 217 B 218,R 168 G 187 B 192,Core and background colors:,,,,,81,© Nokia Solutions and Networks 2015,,Click to edit Master title style,,Click to edit Master text styles,,Second level,,Third level,,Fourth level,,Fifth level,,R 18 G 65 B 145,R 0 G 201 B 255,R 104 G 113 B 122,R 216 G 217 B 218,R 168 G 187 B 192,Core and background colors:,,,,,1,© Nokia Solutions,and Networks,2014,,释放流程及异常释放原因分析,201,6-05,,概述,,主要内容说明,,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；通过对这些内容的梳理和讨论，能够了解,LTE,释放的理论知识，并且在日常,KPI,和,Log,分析方面，提供帮助。
释放流程及异常释放原因分析,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、原因,,E-RAB release,,UE context release,,RRC connection release,,异常释放的触发情景详解,,UE initiated drop,,eNB initiated drop,,异常释放,related,Counter Triggers,,Network/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认承载、专用承载两种：,,默,认承载,：,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,；,,专用承载,：一,定是由,PGW,触发建立,的；,一个,UE,可以有不同,的专用承载；,GTP variant: EPS bearer termination in PGW,SRB,与默认、专用承载关系,业务承载类型,,无线承载分类,,SRB,,– Signalling Radio Bearers,（,SRBs,）的定义是，仅用于传输,RRC,和,NAS,消息的,RB,（,Radio Bearer,）；,,,,,,,,,DRB,,– Data Radio 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-RAB,,E-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,DRB,（,Data Radio Bearer,，数据无线承载）串联而成，进入,LTE,系统的业务数据主要通过,E-RAB,进行传输。
因此对于,LTE,，业务管理主要是在,E-RAB,层次上进行的,–,一个,UE,可以有多个,E-RAB,，目前最多支持,8,个,EPS,承载（５个,AM,,DRB,，,3,个,UM,,DRB,）,.,,–,在应用上，,E-RAB,常出现于性能指标的统计中，例如：,E-RAB,建立成功率E-RAB,建立成功指,eNodeB,成功为,UE,分配了通信通道的无线资源和用户面的无线承载，所以这个指标反映了,eNodeB,或小区接纳业务的能力，可以用来考虑系统负荷情况,业务承载类型,,UE context及E-RAB,,UE,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漫游和接入限制有关的信,息；,,–,Initial UE context,只能由,MME,发,起，一个,UE,只有一个,UE context,；,,–,一个,eNB UE context,是,eNB,内和一个处于激活状态的,UE,相关联的一个信息块。
这块信息是为了维持,E-UTRAN,提供给这个激活态,UE,的服务所必须的信息；,,–,eNB UE context,是在,UE,迁移到激活状态之后开始建立的；或者，,eNB UE context,是在切换目标,eNB,完成切换资源分配（切换准备阶段）之后开始建立的RRC connection,,,层三信令连接，,UE,保持非,IDLE,的必须连接，一个,UE,只有一个,RRC connection,，一旦连接释放，,UE,所有业务释放，并进入,RRC_IDLE,态；,LTE完整业务流程,,默认承载建立信令流程（Attach）,,Steps:,,Random Access,,Initial NAS msg,,NAS security,,S1 init setup,,RRC sec + UE cap,,SRB2/DRB setup,,NAS,reply,LTE完整业务流程,,RA及RRC连接建立流程,,SRB0,：,,RRC connection request,、,RRC connection setup,（消息中包含,SRB1,建立的相关信息）；,,SRB1,：,,RRC connection setup complete,；,LTE完整业务流程,,专用承载建立流程,,Dedicated Bearer Establishment,：,,E-RAB,建立,释放流程及异常释放原因分析,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、原因,,E-RAB release,,UE context release,,RRC connection release,,Abnormal release,的触发情景详解,,UE initiated drop,,eNB initiated drop,,异常释放,related,Counter Triggers,,Network/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 release,,The purpose of the E-RAB Release procedure is to enable the release of already established E-RABs for a given,UE,；,,E-RAB,释,放后，,UE,仍,然可以处于,ECM-CONNECTED,状态；,,UE context release,,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,.,,当,UE,回,到,ECM-,IDLE,状,态时，,MME,向,eNodeB,发,UE CONTEXT RELEASE,消息。
收到这条消息后，,eNodeB,删除,eNB,UE,,context,MME,继续保留,MME,UE 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 release,,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,；,,RRC,连接释放后，,UE,进入,RRC_IDLE,状态E-RAB release,,释放类型：E-RAB release,,根据,3GPP,定义,(3GPP TS 36.413),，,E-RAB release,过程分为两大类：,,ENodeB Initiated,,MME Initiated,,E-RAB,管理的相关信息都,embed,在,context,管理信令中MME Initiated,,ENodeB Initiated,,释放流程信令详解,,E-RAB release ：MME Initiated,,E-RAB release command,消息内容：,,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-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,消,息内容：,,- 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 released, 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 Initiated,,eNB,收到,E-RAB RELEASE COMMAND,后，,eNB,将会释放被请求的,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 protocol 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 Initiated,,E-RAB RELEASE INDICATION,消息内容：,,The E-RAB RELEASE INDICATION message shall contain at least one 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 Release 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原因分析,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、原因,,E-RAB release,,UE context release,,RRC connection release,,Abnormal release,的触发情景详解,,UE initiated drop,,eNB initiated drop,,异常释放,related,Counter Triggers,,Network/Field KPI及Drops分析,,Summary,UE 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 Initiated,,MME Initiated,,This procedure is used to release the logical S1-AP signalling connection (over,S1-MME,) and all S1 bearers (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,的需要，向,MME,请求,UE-associated S1,链接的释放；,,ENodeB,发起的,Context release,情况：,,Normal release,：,“User Inactivity”,，‘,CS Fallback triggered’,，‘,UE Not Available for PS Service’,，‘,Inter-RAT Redirection’,，‘,Time Critical Handover’,，‘,Handover Cancelled’,，“,Detach”,,Abnormal release,：,“,Radio Connection With UE Lost”, “CSG Subscription Expiry,”,,“Redirection towards 1xRTT,”,，,Unspecified,Failure,，,O&M,Intervention,，,Repeated RRC signalling Integrity Check,Failure,，,etc.,ENodeB Initiated,,UE context release,,释放的触发条件—UE Context Release Command,,MME 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 handover, 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 allowed 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,,正常释放原因信令实例,,eNB initiated,MME initiated,MME initiated,eNB initiated,eNB initiated,UE context release,,异常释放原因信令实例,,MME initiated,eNB initiated,MME initiated,MME initiated,MME initiated,释放流程信令详解,,UE context release：ENodeB Initiated,,The 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 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 REQUEST message.,释放流程信令详解,,UE context release：ENodeB Initiated,,Transition 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 release：ENodeB Initiated,,释放流程信令详解,,UE context release：MME Initiated,,The 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 RELEASE 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 new,,value is assigned) eNB UE S1AP is released,释放流程信令详解,,UE context release：MME Initiated,,Upon reception of the UE CONTEXT RELEASE COMMAND message, the eNB shall release all related signalling and user data transport resources and reply with the UE CONTEXT RELEASE COMPLETE message. In case of eNB,,supporting 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,,释放流程信令详解,,UE context release：MME Initiated,,释放流程及异常释放原因分析,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、原因,,E-RAB release,,UE context release,,RRC connection release,,Abnormal release,的触发情景详解,,UE initiated drop,,eNB initiated drop,,异常释放,related,Counter Triggers,,Network/Field KPI及Drops分析,,Summary,RRC connection release,,释放类型,,根据,3GPP,定义,(3GPP TS 36.331),，,E-UTRAN initiates the RRC connection release procedure to a UE in RRC_CONNECTED,：,,RRC connection,release,,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.,,RRC connection release requested by upper,layers,,The,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,,释放原因,,The release of the RRC connection is initiated by E-UTRAN. The procedure may be used to re-direct the UE to another frequency or 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原因分析,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、原因,,E-RAB release,,UE context release,,RRC connection release,,Abnormal release,的触发情景详解,,UE initiated drop,,eNB initiated drop,,异常释放,related,Counter Triggers,,Network/Field KPI及Drops分析,,Summary,Call drop,,Who Initiates Drops, UE, MME or eNB?,,UE can ”initiate a drop” by starting RRC Connection Re-establishment,,Note: besides RLF also other causes can trigger RRC Conn Re-Establishment,,eNB can initiate abnormal S1 + RRC release due to,,Radio network layer problem (TA timer, 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 to,,Radio network layer problem,,Other abnormal cause,UE initiated drop,,RLF,,When UE is in RRC_CONNECTED and RRC security is active, it can trigger RRC Connection Re-establishment,,upon,T310 expiry,,upon reaching the,maximum number of UL RLC retransmissions,,upon,handover failure (T304 expiry),,upon,non-HO related random access problem,,If successful, RRC Conn Re-Establishment,,reconfigures SRB1 to resume data transfer of RRC msgs,,re-activates RRC security without changing algorithms,,NOTE: 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 TAU,UE initiated drop,,RLF due to T310 Expiry at UE,,UE initiated drop,,RLF due to Maximum UL RLC Re-Tx Reached,,from 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 : t8,UE initiated drop,,RLF due to HO Failure,,from RRC Connection Reconfiguration:,,,mobilityControlInfo,,targetPhysCellId : 33,,,t304 : ms1000,,newUE-Identity,,Bin : 14 EB (= 5355),UE initiated drop,,RLF Due to Non-HO Random Access Failure,,“Non-HO random access” means,,PDCCH order -triggered RA,,Random Access Scheduling Request,释放流程及异常释放原因分析,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、原因,,E-RAB release,,UE context release,,RRC connection release,,Abnormal release,的触发情景详解,,UE initiated drop,,eNB initiated drop,,异常释放,related,Counter Triggers,,Network/Field KPI及Drops分析,,Summary,eNB initiated drop,,RLF,,,eNB can drop the call due to following triggers,,,eNB-detected radio link problems,,PUSCH RLF,,CQI RLF,,Ack/Nack RLF,,PDCCH Order failure,,SRS RLF,,TA timer expiry,,M,aximum RLC retransmissions exceeded,,GTP-U failure,eNB initiated drop,,Radio Link Problem Detection at eNB,,eNB radio link problem detection mechanisms are,NSN-internally specified,,Multiple methods (called “link monitors”) are defined to detect a radio link problem in the eNB.,,When one link monitor detects a problem, it 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 triggered,,T_RLF = t310 + t311 (eNB-internal timer),,Link monitors:,,Uplink,PUSCH DTX,detection for scheduled uplink data,,CQI DTX,detection for periodic CQI reports in PUCCH and PUSCH,,Uplink Ack/Nack DTX,detection for transmitted downlink data,,PDCCH Order RLF,,SRS DTX detection (TD-LTE),eNB initiated drop,,1. PUSCH RLF: RlsCause_PuschRlf_ON,,When UE is scheduled for PUSCH transmission, eNB expects to receive UL transmission on the scheduled PRBs,,If signal from UE cannot be detected at all, PUSCH DTX is declared,,NOTE: The case where UL TBS is received but it fails CRC check is,not,DTX (it’s a NACK),,DTX PUSCH indication is provided by the UL physical layer.,,The result is received by LTE MAC in,reliableULtransmissionFlag,parameter.,,Both counter-based and timer-based RLF detection is supported,,Timer-based PUSCH RLF detection:,,If “DTX“ is received on the PUSCH for a configurable period of time (,rlpDetMaxTimeUl,), PUSCH RLF is set on,,Counter-based PUSCH RLF detection:,,If “DTX“ is received on the PUSCH for a consecutive number of times (,rlpDetMaxNoUl,),,,PUSCH RLF is set on,,The,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).,,Defined by parameter,rlpDetEndNoUl,.,eNB initiated drop,,1. PUSCH RLF: RlsCause_PuschRlf, Counter-based RLF Detection Example,,T_RLF = T310 + T311,<,p name,=",rlpDetMaxNUl,">,3,,,,<,p name,=",rlpDetEndNUl,">,2,,,vendor- in this example:,eNB initiated drop,,2. Periodic CQI RLF: RlsCause_CqiRlf_ON,,The eNB supports CQI DTX detection for periodic CQI reports on 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_OFF,,The parameters,nCqiDtx,and,nCqiRec,are in the vendor-specific parameter file,,For 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 from 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 PUSCH,eNB initiated drop,,2. Periodic CQI RLF: RlsCause_CqiRlf, Example,,,,<,p name,=",nCqiDtx,">,6,,,,,,<,p name,=",nCqiRec,">,1,,vendor- in this example:,T_RLF = T310 + T311,eNB initiated drop,,3. Ack/Nack RLF: RlsCause_AckNackRlf_ON,,After DL scheduled data, eNB expects HARQ ACK or NACK on PUCCH or PUSCH at known UL TTI,,Timer-based ACK/NACK RLF detection,:,,If ACK/NACK “DTX“ is received for a configurable period of time,(rlpDetMaxTimeDl,), ACK/NACK RLF is set on,,Counter-based ACK/NACK RLF detection:,,If ACK/NACK “DTX“ is received for a consecutive number of times (,rlpDetMaxNoDl,),,,ACK/NACK RLF is set on,,The,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).,,Defined by parameter,rlpDetEndNoDl,.,,.,eNB initiated drop,,4. PDCCH Order RLF,,If 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 using 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 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 immediately,eNB initiated drop,,5. SRS RLF,,The eNB supports SRS DTX detection for radio link problem detection,,If MAC layer receives,nSrsDtx,consecutive reports from UL PHY, the MAC declares SRS RLF,,If the MAC has set SRS RLF for a specific UE and,nSrsRec,consecutive SRS transmissions are succesfully detected the UE, the MAC sets SRS RLF OFF,,Hence the SRS RLF has similar mechanism as CQI DTX RLF,,The parameters,nSrsDtx,and,nSrsRec,are operator-configurable,,P7 default values from RL15 SCF:,,,,8,,1,eNB initiated drop,,When is Drop (= RRC + S1 release) Triggered by eNB?,,3GPP does not specify eNB radio link failures, but NSN eNB mimics 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 to ON state,,For a given UE, T_RLF is stopped only if all RLFs are OFF,,When the timer T_RLF expires, the UE is released from the eNB using eNB initiated S1 release + RRC connection release –> call drop,,T_RLF = T310 + T311,eNB initiated drop,,RLF Triggering by eNB, Signalling,,Only L2 Ack needed for successful RRC 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 Release,eNB initiated drop,,In-Sync and Out-Of-Sync States: Overview,,RRC connected substates: UL in-sync and UL out-of-sync,Uplink RA SR or downlink PDCCH order to bring UE back in-sync,eNB initiated drop,,TA Timer Expiry at UE,,As 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). 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 grants,,,3GPP TS 36.331: Upon receiving a PUCCH/ SRS release request from MAC layer, the UE RRC shall:,,release periodic CQI reporting config, ie it stops CQI reporting on PUCCH,,release Scheduling Request Config,eNB initiated drop,,In-Sync, Out-Of-Sync Handling in RL30,,Parameter,LNCEL/applyOutOfSyncState,defines how eNB handles TA expir。