Week #15 LTE-WLAN Aggregation ( LWA )

1. 教育部行動寬頻尖端技術人才培育計畫-小細胞基站聯盟中心教育部行動寬頻尖端技術人才培育計畫-小細胞基站聯盟中心 示範課程：行動寬頻網路之異質性存取 Week #15LTE-WLAN Aggregation (LWA) 助理教授：吳俊興 助教：王瑞元 國立高雄大學 資訊工程學系

2. Outline • Introduction to LWA • LWA Architecture • LWAAP • E-UTRAN and Wireless LAN (WLAN) • Xw in Layer 1 • Signaling Transport • XwApplication Protocol (XwAP) • XwData Transport • XwInterface User Plane Protocol

3. LTE-WLAN Aggregation (LWA) (TS36.300/22A) • E-UTRAN supports LWAoperation whereby a UE in RRC_CONNECTED is configured by the eNB to utilize radio resources of LTE and WLAN • WLAN AP/AC only interacts with eNB; no interaction with the Core Network • LWA is controlled by eNB, based on UEmeasurement reporting • When LWA is activated, eNB configures one or more bearers as LWAbearers • Two scenarios are supported depending on the backhaul connection between LTE and WLAN • Collocated LWA scenario for an ideal/internal backhaul • Non-collocated LWA scenario for a non-ideal backhaul • WLAN Termination (WT) terminates the Xw interface for WLAN C-Plane connectivity of eNB and WT for LWA U-Plane connectivity of eNB and WT for LWA

4. LWA Radio Protocol Architecture • In LWA, the radio protocol architecture that a particular bearer uses depends on the LWA backhaul scenario and how the bearer is set up • Two bearer types exist for LWA: split LWA bearer and switched LWAbearer LWA Radio Protocol Architecture for the Collocated Scenario • LWAallows asingle bearertobeconfiguredto utilize LTEand WLANsimultaneously • Splitandswitched bearersare supported • R13LWAsupports aggregationindownlinkonly,whileuplinktransmissionisalwayson LTE • Packets(PDCPPDUs)belongingtoLWAbearercanbe sent byeNBvia LTEorWLANsimultaneously • LWA uses EtherType0x9E65 allocated by IEEE RAC LWA Radio Protocol Architecture for the Non-Collocated Scenario

5. LWAand LWIP • LWA(LTE WLAN Aggregation) • 將運行於授權頻譜的 LTE及非授權頻譜的Wi­Fi在PDCP實現聚合，並由LTE eNB做統一調度控制 • 此技術Wi­Fi AP(WT)和LTE eNB間必須要有一個Xw介面溝通，若以小型small cell實現，則經常是以LTE和WiFi一體化設備方式實現，確保可靠性與低延時 • LWIP(LTE WLAN Radio Level Integration with IPsec Tunnel) • LWIP技術不須改動舊有的WLAN架構設備，藉由UE透過WLAN建立IPSec通道至LTE eNB上的Security Gateway，即可實現LTE與WLAN的聚合

6. LWAAP • LTE與無線區域網路聚合適配協定(LTE-WLAN AggregationAdaptation Protocol, LWAAP)，在此層協定中，執行資料連線載體(Data Radio Bearer, DRB)的辨識碼附加，同時添加於基地台端與用戶設備端，以支援多重 LWA 載體的能力

7. LWA : User Plane (Non-collocated) The Xw-U interface is used to deliver LWAAP PDUs between eNB and WT

8. LWA : Control Plane (Non-collocated) • eNB-WT control plane signaling for LWA is performed by means of Xw-C interface signaling

9. LWA : Mobility • A WLAN mobility set is a set of one or more WLAN Access Points (APs) • identified by one or more BSSID/HESSID/SSIDs, • within which WLAN mobility mechanisms apply while the UE is configured with LWA bearer(s) • i.e., the UE may perform mobility between WLAN APs belonging to the mobility set without informing the eNB

10. LWA : Operation • WT Addition • WT Modification • WT Release

11. eLWA • eLWA五大項目標，分別為透過無線區域網路 (Wireless Local Area Networks, WLAN)的 • 上行資料傳送 • 移動管理優化 • 支援 60GHz 頻段 • 資訊收集與回饋 • 自動建立鄰近基 3 台關係(Automatic Neighbour Relation, ANR) • 3GPPRAN2#93,#96

12. eLWA-更新的上行傳輸的系統架構圖 • 3GPPRAN2#96 • 有關上行資料傳輸，可能造成的封包序號不同步 • 留給用戶設備(UE)自行處理 • 目前的PDCP狀態回報與LWA狀態回報的資訊

13. Abbreviations & Definitions • E-UTRAN : Evolved Universal Terrestrial Radio Access Network • O&M : Operations & Maintenance • Xw : logical interface between eNB and WT • WT : WLAN Termination • IANA : Internet Assigned Numbers Authority • IETF : Internet Engineering Task Force • PPP : Point-to-Point Protocol • RFC : Request for Comments • SCTP : Stream Control Transmission Protocol • Elementary Procedure:a unit of interactionbetween an eNB and WT, consists of an initiating message and possibly a response message • Class 1: Elementary Procedures with response (success or failure), • Class 2: Elementary Procedures without response • E-RAB : E-UTRAN Radio Access Bearer. An E-RAB uniquely identifies the concatenation of an S1 Bearer and the corresponding Data Radio Bearer. When an E-RAB exists, there is a one-to-one mapping between this E-RAB and an EPS bearer of the Non Access Stratum

14. Definitions and Terms • LWA bearer : in LTE-WLAN Aggregation, a bearer whose radio protocols are located in both the eNB and the WLAN to use both eNB and WLAN resources • WLAN Termination : the logical node that terminates the Xw interface on the WLAN side. • PDCP : Packet Data Convergence Protocol • RCLWI : RAN Controlled LTE-WLAN Interworking • EP Elementary Procedure • IE Information Element • SN Sequence Number • TAC Tracking Area Code • UE User Equipment • LWA LTE/WLAN Aggregation • RCL WI : RAN Controlled LTE-WLAN Interworking • Xw UP : Xw User Plane • 3GPP TR 21.905: "Vocabulary for 3GPP Specifications"

15. Layer 1 (Physical layer) on the Xw Interface • Interface to physical medium • Frame delineation • Line clock extraction capability • Transmission quality control • The support of any suitable layer 1 technique - like point-to-point or point-to-multipoint techniques - shall not be prevented • Interface to management plane • Performance monitoring functions • Alarm status reporting functions • Synchronization source management • 3GPP TS 36.411: “Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 layer 1”

16. XwSignaling Bearer Signaling Transport • Functions • Provision of reliable transfer of Xw-AP message over Xwinterface • Provision of networking and routeingfunction • Provision of redundancy in the signallingnetwork • Support for flow control and congestion control • Protocols • Figure : Xwsignalling bearer protocol stack • The Transport Network Layer is based on IP transport, comprising SCTP on top of IP

17. Protocol Stack • Data link layer : • The support of any suitable Data Link Layer protocol, e.g. PPP, Ethernet • IP layer : • The eNB shall support Ipv6 and/or Ipv4 • The IP layer of Xw only supports point-to-point transmission for delivering Xw-AP message • The eNB shall support the Diffserv Code Point marking • Transport layer : • There shall be only one SCTP association established between one eNB and WT pair • The eNB shall establish the SCTP association • A single pair of stream identifiers shall be reserved for the sole use of XwAP elementary procedures that utilize non UE-associated signalling • At least one pair of stream identifiers shall be reserved for the sole use of XwAP elementary procedures that utilize UE-associated signalling • A single UE-associated signalling shall use one SCTP stream and the stream should not be changed during the communication of the UE-associated signalling • The SCTP congestion control may, using an implementation specific mechanism, initiate higher layer protocols to reduce the signalling traffic at the source and prioritise certain messages

18. XwAPServices • the services offered between an eNB and WT • The Xw interface XwAP(XwApplication Protocol) procedures • UE-associated XwAP procedures :handle the configuration and modification to support LWA for a specific UE • Non UE-associated procedures :support LWA and RCLWI, and are not related to a specific UE • Parallel transactions • Unless explicitly indicated in the procedure specification • at any instance in time one protocol peer • shall have a maximum of one ongoing XwAP procedure related to a certain UE

19. Non-collocated LWA Overall Architecture

20. Services Expected from Signalling Transport • The signalling connection shall provide in sequence delivery of XwAPmessages • XwAPshall be notified if the signalling connection breaks • Xwsignalling transport is described in TS 36.462

21. Mapping between XwAPFunctions and XwAP EPs

22. XwAPProceduresClass 1 Elementary Procedures

23. XwAPProceduresClass 2 Elementary Procedures

24. Xw Setup • Exchange application level configuration data needed for the eNB and the WT to interoperate correctly over the Xwinterface • Erases any existing application level configuration data in the two nodes • Replaces it by the one received • This procedure also resets the Xwinterface • The procedure uses non-UE-associated signalling

25. XwSetup - Successful Operation • XwSETUP REQUEST message(eNB->WT) • Xw SETUP RESPONSE message(WT->eNB) • Alist of relevant WLAN identifiers

26. XwSetup - Unsuccessful Operation • XwSETUP FAILURE message (WT->eNB) • candidate WT cannot accept the setup • An appropriate cause value

27. Xw Setup - Abnormal Conditions • The first message received for a specific TNL association • Not an Xw SETUP REQUEST, Xw SETUP RESPONSE, orXw SETUP FAILURE message • Shall be treated as a logical error

28. WT Configuration Update • Update application level configuration data needed for an eNB and a WT to interoperate correctly over the Xwinterface • The procedure uses non-UE-associated signalling

29. WT Configuration Update - Successful Operation • WT CONFIGURATION UPDATE message (WT->eNB) • Include an appropriate set of up-to-date configuration data • Added, modified and deleted • WLAN identifiers that the WT has just taken into operational use

30. WT Configuration Update - Unsuccessful Operation • CONFIGURATION UPDATE FAILURE message (eNB->WT) • an appropriate cause value

31. WT Status Reporting Initiation • This procedure is used by an eNB • Request the reporting of load measurements to a WT • The procedure uses non-UE-associated signalling

32. WT Status Reporting Initiation procedure – Successful Operation • WT STATUS REQUEST message (eNB->WT) • Registration Request IE • Start • WT initiate the requested measurement • Report Characteristics IE • The type of objects WT shall perform measurements on • Stop • WTshall stop all measurements and terminate the reporting • Ignore Report Characteristics ,BSS To Report List, Reporting Periodicity, Partial Success Indicator • Partial Success Indicator IE : WT provide not all of the information • WT STATUS REPORT message(WT->eNB) • BSS report list • BSSLoadIE:firstbit • WANMetricsIE:secondbit • AvailableChannelUtilizationIE:thirdbit • ReportingPeriodicityIE:Timeinterval between two messages • WT STATUS RESPONSE message(WT->eNB) • Measurement Initiation Result IE : WT initiate the measurement for the admitted measurement objects

33. WT Status Reporting Initiation Procedure - Unsuccessful Operation • WT STATUS FAILURE message • None of the requested measurements can be initiated • Cause IE • Set to an appropriate value for each requested measurement object • Complete Failure Cause Information IE

34. WT Status Reporting Initiation Procedure –Abnormal Conditions • The eNB does not receive either WT STATUS RESPONSE message or WT STATUS FAILURE message • The eNB may reinitiate the WT Status Reporting Initiation procedure towards the WT • New identical WT STATUS REQUEST • Failed • WT STATUS RESPONSE : Measurement Initiation Result ID without admitted measurements • Registration Request IE is set to "start" and the Report Characteristics IE bitmap is set to "0" • Registration Request IE is set to "start" and the Reporting Periodicity IE value is not specified • Registration Request IE set to "start" and the eNB Measurement ID IE corresponding to an existing on-going load measurement reporting • Registration Request IE is set to "stop" and the WT STATUS REQUEST message does not contain WT Measurement ID IE

35. WT Status Reporting • This procedure is initiated by the WT to report the result of measurements admitted by the WT following a successful WT Status Reporting Initiation procedure • WT STATUS REPORT message (WT->eNB) • The admitted measurements are the measurements that were successfully initiated during the preceding WT Status Reporting Initiation procedure

36. Error Indication • The Error Indication procedure is initiated by a node to report detected errors in one incoming message • cannot be reported by an appropriate failure message. • If the error situation arises due to reception of a message which used UE-associated signalling • Then the Error Indication procedure uses UE-associated signalling • Otherwise the procedure uses non UE-associated signalling

37. Error Indication Procedure, eNB/WT Originated -Successful Operation • ERROR INDICATION message • Cause IE • Criticality DiagonsticsIE • eNBUE XwAP ID IE /WTUE XwAP ID IE

38. Reset • Align the resources in the eNB and in the WT in the event of an abnormal failure • The procedure resets the Xw interface • Not affect the application level configuration data exchanged during • The Xw Setup procedure • The procedure uses non UE-associated signalling

39. Reset, eNB/WT-initiated Successful Operation • RESETmessage • Receiving node shall • Abort any other ongoing procedures • Except another Reset procedure • Delete all the context information related to the initiating node • Except the application level configuration data exchanged during Xw Setup or WT Configuration Update procedures • Release the corresponding resources • Respond with a RESET RESPONSE message • Abnormal condition • If Reset procedure is ongoing and the receiving node receives the RESET message from the peer entity on the same Xwinterface • the receiving node shall respond with the RESET RESPONSE message

40. WT Addition Preparation • Request the WT to allocate resources for LWA operation for a specific UE • The procedure uses UE-associated signalling • Three cases • Successful Operation • Unsuccessful Operation • Abnormal Operation

41. WT Addition Preparation - Successful Operation • WT ADDITION REQUEST message(eNB->WT) • E-RAB Level QoSParameters IE • Allocation and Retention Priority IE • Allocation of sources • GBR QoS InformationIE • eNB may therefore need to monitor the bit rate of offloaded GBR bearers • Serving PLMNIE • The WT may take it into account for the allocation of resources for LWA • Reception of the WT ADDITION REQUEST message, WT shall • Use the information included in the Mobility SetIE • The WLAN Mobility Set configured for LWA • Store the WLAN Security Information IE, if included • Establish the required security relation towards the UE • WT ADDITION REQUEST ACKNOWLEDGE message(WT->eNB), requested E-RAB • E-RABs Admitted To Be Added ListIE : successfully established • E-RABs Not Admitted ListIE : failed to be established

42. WT Addition Preparation - Unsuccessful Operation • If the WT is not able to accept at least one of the bearers or a failure occurs during the WT Addition Preparation, the WT sends the WT ADDITION REQUEST REJECT message with an appropriate cause value to the eNB

43. WT Addition Preparation - Abnormal Conditions • If the WT receives a WT ADDITION REQUEST message containing multiple E-RAB ID IEs (in the E-RABs To Be Added List IE) set to the same value • The WT shall consider the establishment of the corresponding E-RAB as failed • If the WT receives a WT ADDITION REQUEST message containing an E-RAB Level QoS Parameters IE which contains a QCI IE indicating a GBR bearer , and which does not contain the GBR QoS InformationIE • The WT shall consider the establishment of the corresponding E-RAB as failed

44. eNB Initiated WT Modification • This procedure is used to enable an eNB to request a WT to modify the UE context at the WT • The procedure uses UE-associated signalling

45. eNB initiated WT Modification – Successful Operation • WT MODIFICATION REQUEST message(eNB->WT) • UE Context Information IE: • E-RABs to be added within the E-RABs To Be Added ItemIE • E-RABs to be modified within the E-RABs To Be Modified ItemIE • E-RABs to be released within the E-RABs To Be Released ItemIE • WLAN security information in the WLAN Security InformationIE • E-RAB Level QoS Parameters IE • Allocation and Retention Priority IE • GBR QoS Information IE • eNB may therefore need to monitor the bit rate of offloaded GBR bearers • Serving PLMN IE • The WT may take it into account forthe allocation of resources for LWA • eNB GTP Tunnel Endpoint IE in the E-RABs To Be Modified Item IE • E-RAB level QoS parameter IE • WT GTP Tunnel Endpoint IE • Mobility Set IE • WT MODIFICATION REQUEST ACKNOWLEDGE message(WT->eNB) • E-RABs Admitted To Be Added List IE • E-RABs Admitted To Be Modified List IE • E-RABs Admitted To Be Released List IE • E-RABs Not Admitted List IE

46. eNB initiated WT Modification – Unsuccessful Operation • If the WT does not admit any modification requested by the eNB, or a failure occurs during the eNB initiated WT Modification • The WT shall send the WT MODIFICATION REQUEST REJECT message to the eNB • The message shall contain the Cause IE with an appropriate value

47. eNB initiated WT Modification,Abnormal Conditions • If the WT receives a WT MODIFICATION REQUEST message containing multiple E-RAB ID IEs (in the E-RABs To Be Added List IE and/or the E-RABs To Be Modified List IE) set to the same value • The WT shall not admit the action requested for the corresponding E-RABs • If the WT receives a WT MODIFICATION REQUEST message containing multiple E-RAB ID IEs (in the E-RAB To Be Released List IE) set to the same value • The WT shall initiate the release of one corresponding E-RAB and ignore the duplication of the instances of the selected corresponding E-RABs • If the WT receives a WT MODIFICATION REQUEST message containing a E-RAB Level QoS Parameters IE which contains a QCI IE indicating a GBR bearer (as defined in TS 23.203 [13]), and which does not contain the GBR QoS Information IE • The WT shall not admit the corresponding E-RAB • Interaction with the WT initiated WT Modification procedure: • If the eNB, after having initiated the eNB initiated WT Modification procedure, receives the WT MODIFICATION REQUIRED message • The eNB shall refuse the WT initiated WT Modification procedure with an appropriate cause value in the CauseIE

48. WT Initiated WT Modification • This procedure is used by the WT to modify the UE context in the WT. • In particular, in this Release of the specification, this procedure is used to request to the eNB the release of LWA bearers, or change their WT GTP Tunnel Endpoints • The procedure uses UE-associated signalling

49. WT initiated WT Modification – Successful Operation • WT MODIFICATION REQUIRED message(WT->eNB) • E-RABs to be released within the E-RABs To Be Released ItemIE • E-RABs to be modified within the E-RABs To Be Modified ItemIE • E-RABs To Be Modified Item IE • WT GTP Tunnel Endpoint IE • The eNB shall use this information to change the Xw transport bearer associated to the concerned E-RAB • MODIFICATION CONFIRM message(eNB->WT) • E-RABs Confirmed To Be Released ListIE • DL Forwarding GTP Tunnel Endpoint IE: dataforwarding of downlink packets for that bearer • E-RABs Confirmed To Be Modified List IE

50. WT initiated WT Modification – Unsuccessful Operation • In case none of the requested modifications can be performed successfully • the eNB shall respond with the WT MODIFICATION REFUSE message to the WT with an appropriate cause value in the Cause IE