LTE系统全网信令流程

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1、0,LTE系统全网信令流程,Introduction,As a new wireless mobile communication technology, LTE (Long Term Evolution) provide all kinds of services through network access procedures. So when you are trying to understand the LTE technology, the network access procedure is just in the close front of your eyes. This

2、 document is trying to describe the general procedure handlings among the network elements under LTE network architecture, by way of showing you the procedure handlings in figures. From these figures, you will get an overview of the LTE general procedures, such as: “The System Information Handling”,

3、 “The Random Access Procedure”, “The Attach Procedure”, “The TAU Procedure”, “The Handover Procedure”, etc. The first several figures show the introduction of protocol layer stacks among network elements, such as: protocol layer stacks“between UE-MME”, “between UE-PDN GW”, etc. From these protocol l

4、ayer stacks introduction, you will learn the peer-to-peer protocol layers among several related network elements, it will help you to understand LTE procedures working mechanism stuff. And after, begins the description of the LTE general procedure, in an order from “System information handling”to “A

5、NR Measurement procedure”, with the “access procedure”, “handover procedure”, “inter-RAT operation procedure”, in the middle. From these procedure figures description, you can get the deep details of the LTE network access procedure, and it will finally direct you to found a whole-system-view of LTE

6、 architecture. This document is suitable for the guys who want to know the LTE general procedure, or use it as a reference book. 2009-11-06,1,Abbreviations,MME Mobility Management Entity UE User Equipment MS Mobile Station eNodeB evolved NodeB GW GateWay PCRF Policy and Charging Rules Fuction H-PCRF

7、 Home-PCRF V-PCRF Visited-PCRF HSS Home Subscriber Server EIR Equipment Identity Register UTRAN Universal Terrestrial Radio Access Network E-UTRAN evolved UTRAN GERAN GSM/EDGE Radio Access Network PLMN Public Land Mobile Network HPLMN Home PLMN VPLMN Visited PLMN HLR Home Location Register VLR Visit

8、or Location Register CBC Cell Broadcast Centre OMC Operation and Maintenance Center BSC Base Station Controler BTS Base Transceiver Station BSS Base Station Subsystem CN Core Network MSC/SGSN Mobile-services Switching Centre/Serving GPRS Support Node Inter-RAT Radio Access Technology MBMS Media Broa

9、dcast and Multicast System MCE Multi-cell/multicast Coordination Entity RNC Radio Network Controler,2,Network elements functions,eNodeB functions: -Header compression and user plane ciphering; -MME selection when no routeing to an MME can be determined from the information provided by the UE; -UL be

10、arer level rate enforcement based on UE-AMBR and MBR via means of uplink scheduling(e.g. by limiting the amount of UL resources granted per UE over time); -DL bearer level rate enforcement based on UE-AMBR; -UL and DL bearer level admission control; -Transport level packet marking in the uplink, e.g

11、. setting the DiffServ Code Point, based on the QCI of the associated EPS bearer. MME functions: -NAS signalling; -NAS signalling security; -Inter CN node signalling for mobility between 3GPP access networks (terminating S3); -UE Reachability in ECM-IDLE state (including control and execution of pag

12、ing retransmission); -Tracking Area list management; -PDN GW and Serving GW selection; -MME selection for handovers with MME change; -SGSN selection for handovers to 2G or 3G 3GPP access networks; -Roaming (S6a towards home HSS); -Authentication; -Authorization; -Bearer management functions includin

13、g dedicated bearer establishment; -Lawful Interception of signalling traffic; -Warning message transfer function (including selection of appropriate eNB); UE Reachability procedures. SGSN functions: -Inter EPC node signalling for mobility between 2G/3G and E-UTRAN 3GPP access networks; -PDN and Serv

14、ing GW selection: the selection of SGW/PGW by the SGSN is as specified for the MME; MME selection for handovers to E-UTRAN 3GPP access network.,3,Network elements functions,Serving GW functions: -the local Mobility Anchor point for inter-eNodeB handover; -sending of one or more end marker to the sou

15、rce eNodeB, source SGSN or source RNC immediately after switching the path during inter-eNodeB and inter-RAT handover, especially to assist the reordering function in eNodeB. -Mobility anchoring for inter-3GPP mobility (terminating S4 and relaying the traffic between 2G/3G system and PDN GW); -ECM-I

16、DLE mode downlink packet buffering and initiation of network triggered service request procedure; -Lawful Interception; -Packet routeing and forwarding; -Transport level packet marking in the uplink and the downlink, e.g. setting the DiffServ Code Point, based on the QCI of the associated EPS bearer

17、; -Accounting for inter-operator charging. For GTP-based S5/S8, the Serving GW generates accounting data per UE and bearer; -Interfacing OFCS according to charging principles and through reference points specified in TS32.24051. PDN GW functions: -Per-user based packet filtering (by e.g. deep packet

18、 inspection); -Lawful Interception; -UE IP address allocation; -Transport level packet marking in the uplink and downlink, e.g. setting the DiffServ Code Point, based on the QCI of the associated EPS bearer; -Accounting for inter-operator charging; -UL and DL service level charging as defined in TS2

19、3.2036(e.g. based on SDFs defined by the PCRF, or based on deep packet inspection defined by local policy); -Interfacing OFCS through according to charging principles and through reference points specified in TS32.24051. -UL and DL service level gating control as defined in TS23.2036; -UL and DL ser

20、vice level rate enforcement as defined in TS23.2036(e.g. by rate policing/shaping per SDF); -UL and DL rate enforcement based on APN-AMBR(e.g. by rate policing/shaping per aggregate of traffic of all SDFs of the same APN that are associated with Non-GBR QCIs);,4,Network elements functions,-DL rate e

21、nforcement based on the accumulated MBRs of the aggregate of SDFs with the same GBR QCI(e.g. by rate policing/shaping); -DHCPv4 (server and client) and DHCPv6 (client and server) functions; -The network does not support PPP bearer type in this version of the specification. Pre-Release 8 PPP function

22、ality of a GGSN may be implemented in the PDN GW; -packet screening. -UL and DL bearer binding as defined in TS23.2036; -UL bearer binding verification as defined in TS23.2036; -Functionality as defined in RFC486132; -Accounting per UE and bearer. H-PCRF functions: -terminates the Rx reference point

23、 for home network services; -terminates the S9 reference point for roaming with local breakout; -associates the sessions established over the multiple reference points (S9, Rx), for the same UEs IP-CAN session (PCC session binding). V-PCRF functions: -terminates the Gx and S9 reference points for ro

24、aming with local breakout; -terminates Rx for roaming with local breakout and visited operators Application Function.,5,网元间信令面总体协议栈,6,网元间信令面总体协议栈（续）,7,网元间用户面总体协议栈,8,网元间用户面总体协议栈（续）,9,系统消息广播流程,Special comments: The frozen data of fiducial 3GPP protocol version : 2009/09.,System information handling: S

25、ystem information is divided into the MasterInformationBlock (MIB) and a number of SystemInformationBlocks (SIBs). The MIB includes a limited number of most essential and most frequently transmitted parameters that are needed to acquire other information from the cell, and is transmitted on BCH. SIB

26、s other than SystemInformationBlockType1 are carried in SystemInformation (SI) messages and mapping of SIBs to SI messages is flexibly configurable by schedulingInfoList included in SystemInformationBlockType1, with restrictions that: each SIB is contained only in a single SI message, only SIBs havi

27、ng the same scheduling requirement (periodicity) can be mapped to the same SI message, and SystemInformationBlockType2 is always mapped to the SI message that corresponds to the first entry in the list of SI messages in schedulingInfoList. There may be multiple SI messages transmitted with the same

28、periodicity. SystemInformationBlockType1 and all SI messages are transmitted on DL-SCH. Reference: 36.331: Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification;,10,小区选择流程,1)Initial Cell Selection: This procedure requires no prior knowledge of whic

29、h RF channels are E-UTRA carriers. The UE shall scan all RF channels in the E-UTRA bands according to its capabilities to find a suitable cell. On each carrier frequency, the UE need only search for the strongest cell. Once a suitable cell is found this cell shall be selected. 2)Stored Information C

30、ell Selection: This procedure requires stored information of carrier frequencies and optionally also information on cell parameters, from previously received measurement control information elements or from previously detected cells. Once the UE has found a suitable cell the UE shall select it. If n

31、o suitable cell is found the Initial Cell Selection procedure shall be started. suitable cell: A suitable cell is a cell on which the UE may camp on to obtain normal service. Such a cell shall fulfil all the following requirements. -The cell is part of either: -the selected PLMN, or: -the registered

32、 PLMN, or: -a PLMN of the Equivalent PLMN list according to the latest information provided by NAS: -The cell is not barred -The cell is part of at least one TA that is not part of the list of forbidden tracking areas for roaming , which belongs to a PLMN that fulfils the first bullet above; -The ce

33、ll selection criteria are fulfilled; -For a CSG cell, the CSG ID is part of the allowed CSG list of the UE. 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. Referenc

34、e: 36.331: Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification; 36.304: Evolved Universal Terrestrial Radio Access (E-UTRA);Equipment (UE) procedures in idle mode,Special comments: The frozen data of fiducial 3GPP protocol version : 2009/09.,11,小

35、区重选流程,Reselection priorities handling: 1)Absolute priorities of different E-UTRAN frequencies or inter-RAT frequencies may be provided to the UE in the system information, in the RRCConnectionRelease message, or by inheriting from another RAT at inter-RAT cell (re)selection. 2)In the case of system

36、information, an E-UTRAN frequency or inter-RAT frequency may be listed without providing a priority (i.e. the field cellReselectionPriority is absent for that frequency). If priorities are provided in dedicated signalling, the UE shall ignore all the priorities provided in system information. 3)If U

37、E is in camped on any cell state, UE shall only apply the priorities provided by system information from current cell, and the UE preserves priorities provided by dedicated signalling unless specified otherwise. 4)When the UE in camped normally state, has only dedicated priorities other than for the

38、 current frequency, the UE shall consider the current frequency to be the lowest priority frequency (i.e. lower than the eight network configured values). 5)The UE shall delete priorities provided by dedicated signalling when: -the UE enters RRC_CONNECTED state; or -the optional validity time of ded

39、icated priorities (T320) expires; or -a PLMN selection is performed on request by NAS. 6)The UE shall only perform cell reselection evaluation for E-UTRAN frequencies and inter-RAT frequencies that are given in system information and for which the UE has a priority provided. 7)The UE shall not consi

40、der any black listed cells as candidate for cell reselection. 8)The UE shall inherit the priorities provided by dedicated signalling and the remaining validity time (i.e., T320 in E-UTRA, T322 in UTRA and T3230, FFS in GERAN), if configured, at inter-RAT cell (re)selection. Reference: 36.331: Evolve

41、d Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification; 36.304: Evolved Universal Terrestrial Radio Access (E-UTRA);Equipment (UE) procedures in idle mode,Special comments: The frozen data of fiducial 3GPP protocol version : 2009/09.,12,寻呼过程流程,Network Tri

42、gged Service Request(Paging) procedure: If the MME needs to signal with the UE that is in ECM-IDLE state, e.g. to perform the MME/HSS-initiated detach procedure for the ECM-IDLE mode UE or the SGW receives control signalling (e.g. Create Dedicated Bearer Request or Modify Dedicated Bearer Request),

43、the MME starts network triggered service request procedure from step 3. If ISR is activated, when the Serving GW receives a Create Dedicated Bearer Request or Modify Bearer Request for a UE, and the SGW does not have a downlink S1-U and the SGSN has notified the Serving GW that the UE has moved to P

44、MM-IDLE or STANDBY state, the Serving GW buffers signalling messages and triggers MME and SGSN to page UE. In this case the SGW will be notified about the current RAT type based on the UE triggered service request procedure. The SGW will go on executing the dedicated bearer activation or dedicated b

45、earer modification procedure, i.e. send the corresponding buffered signalling to MME or SGSN which UE resides in now and inform the current RAT type to the PDN GW if the RAT type has been changed compared to the last reported RAT Type. If dynamic PCC is deployed, the current RAT type information sha

46、ll also be conveyed from the PDN GW to the PCRF. If the PCRF response leads to an EPS bearer modification the PDN GW should initiate a bearer update procedure as specified in clause5.4.2.1 below. Reference: 23.401: General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Ra

47、dio Access Network (E-UTRAN) access; 36.331: Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification; 36.413: Evolved Universal Terrestrial Radio Access (E-UTRA) ; S1 Application Protocol (S1AP).,13,随机接入流程,Random Access procedure: The random access p

48、rocedure is characterized by: -Common procedure for FDD and TDD; -One procedure irrespective of cell size; The random access procedure is performed for the following five events: -Initial access from RRC_IDLE; -RRC Connection Re-establishment procedure; -Handover; -DL data arrival during RRC_CONNECT

49、ED requiring random access procedure; -E.g. when UL synchronisation status is “non-synchronised”; -UL data arrival during RRC_CONNECTED requiring random access procedure; -E.g. when UL synchronisation status is non-synchronised or there are no PUCCH resources for SR available. Furthermore, the rando

50、m access procedure takes two distinct forms: -Contention based (applicable to all five events); -Non-contention based (applicable to only handover and DL data arrival). Normal DL/UL transmission can take place after the random access procedure. Reference: 36.300: Evolved Universal Terrestrial Radio

51、Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2.,14,ATTACH流程,15,ATTACH流程,E-UTRAN Initial Attach procedure: A UE/user needs to register with the network to receive services that require registration. This registration is described as Netw

52、ork Attachment. The always-on IP connectivity for UE/users of the EPS is enabled by establishing a default EPS bearer during Network Attachment. The PCC rules applied to the default EPS bearer may be predefined in the PDN GW and activated in the attachment by the PDN GW itself. The Attach procedure

53、may trigger one or multiple Dedicated Bearer Establishment procedures to establish dedicated EPS bearer(s) for that UE. During the attach procedure, the UE may request for an IP address allocation. Terminals utilising only IETF based mechanisms for IP address allocation are also supported. During th

54、e Initial Attach procedure the Mobile Equipment Identity is obtained from the UE. The MME operator may check the ME Identity with an EIR. At least in roaming situations, the MME should pass the ME Identity to the HSS, and, if a PDNGW outside of the VPLMN, should pass the ME Identity to the PDNGW. Th

55、e E-UTRAN Initial Attach procedure is used for Emergency Attach by UEs that need to perform emergency services but cannot gain normal services from the network. These UEs are in limited service state as defined in TS23.12210. Also UEs that had attached for normal services and do not have emergency b

56、earers established and are camped on a cell in limited service state (e.g. restricted Tracking Area or not allowed CSG) shall initiate the Attach procedures indicating that the attach is to receive emergency services. UEs that camp normally on a cell, i.e. UEs that are not in limited service state,

57、should initiate normal initial attach when not already attached and shall initiate the UE Requested PDN Connectivity procedure to receive emergency EPS bearer services. NOTE1:A UE that is emergency attached performs initial attach procedure before being able to obtain normal services. Reference: 23.

58、401: General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access; 36.331: Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification; 36.413: Evolved Universal Terrestrial Radio Access (E-UTRA

59、) ; S1 Application Protocol (S1AP).,16,TAU流程,E-UTRAN Tracking Area Update procedures: The procedure is initiated by an UE in either ECM-IDLE state or ECM-CONNECTED state. NOTE1:If the tracking area update procedure fails a maximum allowable number of times, or if the MME returns a Tracking Area Upda

60、te Reject (Cause) message, the UE shall enter EMM DEREGISTERED state. If the Update Location Ack message indicates a reject, this should be indicated to the UE, and the UE shall not access non-PS services until a successful location update is performed. Reference: 23.401: General Packet Radio Servic

61、e (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access; 36.331: Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification; 36.413: Evolved Universal Terrestrial Radio Access (E-UTRA) ; S1 Application Protocol (S1A

62、P).,17,DETACH流程,UE-initiated Detach procedure for E-UTRAN: The Detach procedure is that UE camps on E-UTRAN and Detach Request is sent to MME. Reference: 23.401: General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access; 36.331: Evolved

63、Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification; 36.413: Evolved Universal Terrestrial Radio Access (E-UTRA) ; S1 Application Protocol (S1AP).,18,鉴权流程,19,鉴权流程,E-UTRAN Authentication and Key Agreement procedure: EPS AKA is the authentication and key a

64、greement procedure that shall be used over E-UTRAN, between the UE and MME. EPS AKA is specified in TS33.40141. EPS AKA shall produce keying material forming a basis for user plane (UP), RRC, and NAS ciphering keys as well as RRC and NAS integrity protection keys. Reference: 23.401: General Packet R

65、adio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access; 33.401: 3GPP System Architecture Evolution (SAE); Security architecture. 36.331: Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification; 36.413

66、: Evolved Universal Terrestrial Radio Access (E-UTRA) ; S1 Application Protocol (S1AP).,20,UE呼叫流程,Reference: 23.401: General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access; 36.331: Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Proto