1. Week #15 LTE-WLAN Aggregation (LWA)
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 #15 LTE-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
Xw Application Protocol (XwAP)
Xw Data Transport
Xw Interface User Plane Protocol
參考資料:

3. LTE-WLAN Aggregation (LWA) (TS36.300/22A)
E-UTRAN supports LWA operation 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 UE measurement reporting
When LWA is activated, eNB configures one or more bearers as LWA bearers
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 LWA bearer
LWA Radio Protocol Architecture for the Collocated Scenario
LWA allows a single bearer to be configured to utilize LTE and WLAN simultaneously
Split and switched bearers are supported
R13 LWA supports aggregation in downlink only, while uplink transmission is always on LTE
Packets (PDCP PDUs) belonging to LWA bearer can be sent by eNB via LTE or WLAN simultaneously
LWA uses EtherType 0x9E65 allocated by IEEE RAC
LWA Radio Protocol Architecture for the Non-Collocated Scenario

5. LWA and 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
參考資料:

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)
在U-plan(user plane)層面, LTE與WLAN是被聚合於Packet Data Convergence Protocol(PDCP)層.
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
以移動集合(mobility-set)替代一群存取點(agroup of Aps)，每個 mobility-set 的識別(ID)可能是基礎服務組識別碼 (BSSID)、同質延伸服務識別碼(HESSID)、或服務組識別碼(SSID)，相同 mobility-set 的存取點(AP)會有相同 SSID。
eNB 提供一組 mobility-set 給 UE，UE 在任何時間點都只能連結到一個 mobility-set。
mobility-set 內的 APs 都連接到同一個 WT；一個WT 可以連接多個 mobility-sets。
若 UE 在相同 mobility-set 的 APs 間移動，可以不通知 eNB；若發生跨 mobility-sets 的移動，則需要由 eNB 控制。

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)
3GPP RAN2 #93, #96

12. eLWA-更新的上行傳輸的系統架構圖 3GPP RAN2 #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 interaction between 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 : "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 : “Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 layer 1 ”

16. Xw Signaling Bearer Signaling Transport
Functions
Provision of reliable transfer of Xw-AP message over Xw interface
Provision of networking and routeing function
Provision of redundancy in the signalling network
Support for flow control and congestion control
Protocols
Figure : Xw signalling bearer protocol stack
The Transport Network Layer is based on IP transport, comprising SCTP on top of IP

17. Protocol Stack Data link layer : IP layer : Transport 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. XwAP Services the services offered between an eNB and WT
The Xw interface XwAP(Xw Application 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 XwAP messages
XwAP shall be notified if the signalling connection breaks
Xw signalling transport is described in TS

21. Mapping between XwAP Functions and XwAP EPs
Elementary Procedure(s)
WLAN Status Reporting
WT Status Reporting Initiation
WT Status Reporting
Setting up the Xw
Xw Setup
WT Configuration Update
LTE-WLAN Aggregation
WT Addition Preparation
WT Association Confirmation
eNB Initiated WT Modification
WT Initiated WT Modification
eNB Initiated WT Release
WT Initiated WT Release
Reporting of General Error Situations
Error Indication
Resetting the Xw
Reset

22. XwAP Procedures Class 1 Elementary Procedures
Initiating Message
Successful Outcome
Unsuccessful Outcome
Response message
Xw Setup
Xw SETUP REQUEST
Xw SETUP RESPONSE
Xw SETUP FAILURE
WT Configuration Update
WT CONFIGURATION UPDATE
WT CONFIGURATION UPDATE ACKNOWLEDGE
WT CONFIGURATION UPDATE FAILURE
WT Status Reporting Initiation
WT STATUS REQUEST
WT STATUS RESPONSE
WT STATUS FAILURE
WT Addition Preparation
WT ADDITION REQUEST
WT ADDITION REQUEST ACKNOWLEDGE
WT ADDITION REQUEST REJECT
eNB Initiated WT Modification
WT MODIFICATION REQUEST
WT MODIFICATION REQUEST ACKNOWLEDGE
WT MODIFICATION REQUEST REJECT
WT Initiated WT Modification
WT MODIFICATION REQUIRED
WT MODIFICATION CONFIRM
WT MODIFICATION REFUSE
WT Initiated WT Release
WT RELEASE REQUIRED
WT RELEASE CONFIRM
Reset
RESET REQUEST
RESET RESPONSE

23. XwAP Procedures Class 2 Elementary Procedures
Initiating Message
WT Status Reporting
WT STATUS REPORT
Error Indication
ERROR INDICATION
WT Association Confirmation
WT ASSOCIATION CONFIRMATION
eNB Initiated WT Release
WT RELEASE REQUEST

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

25. Xw Setup - Successful Operation
Xw SETUP REQUEST message(eNB->WT)
Xw SETUP RESPONSE message(WT->eNB)
A list of relevant WLAN identifiers

26. Xw Setup - Unsuccessful Operation
Xw SETUP 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, or Xw 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 Xw interface
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
WT shall 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
BSS Load IE : first bit
WAN Metrics IE : second bit
Available Channel Utilization IE : third bit
Reporting Periodicity IE : Time interval 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 Diagonstics IE
eNB UE XwAP ID IE / WT UE 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
RESET message
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 Xw interface
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 QoS Parameters IE
Allocation and Retention Priority IE
Allocation of sources
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 for the allocation of resources for LWA
Reception of the WT ADDITION REQUEST message, WT shall
Use the information included in the Mobility Set IE
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 List IE : successfully established
E-RABs Not Admitted List IE : 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 Information IE

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 Item IE
E-RABs to be modified within the E-RABs To Be Modified Item IE
E-RABs to be released within the E-RABs To Be Released Item IE
WLAN security information in the WLAN Security Information IE
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 for the 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 [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 Cause IE

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 Item IE
E-RABs to be modified within the E-RABs To Be Modified Item IE
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 List IE
DL Forwarding GTP Tunnel Endpoint IE : data forwarding 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

51. WT initiated WT Modification - Abnormal Conditions
If the value received in the E-RAB ID IE of any of the E-RABs To Be Released Item IE or of the E-RABs To Be Modified Item IE is not known at the eNB
the eNB shall regard the procedure as failed and
may take appropriate actions like triggering the eNB initiated WT Release procedure
Interaction with the eNB initiated WT Modification Preparation procedure:
If the WT, after having initiated the WT initiated WT Modification procedure, receives the WT MODIFICATION REQUEST message , the WT shall
regard the WT initiated WT Modification Procedure as failed
be prepared to receive the WT MODIFICATION REFUSE message from the eNB
continue with the eNB initiated WT Modification procedure as specified in eNB Initiated WT Modification

52. eNB Initiated WT Release
The eNB initiated WT Release procedure is triggered by the eNB to initiate the release of the resources for a specific UE
The procedure uses UE-associated signalling

53. eNB initiated WT Release - Successful Operation
WT RELEASE REQUEST message (eNB->WT)
WT receipt : WT shall stop providing user data to the UE
Cause IE : eNB provide appropriate information
E-RABs To Be Released Item IE
DL Forwarding GTP Tunnel Endpoint IE : the WT may perform data forwarding of downlink packets for that bearer

54. WT Initiated WT Release
This procedure is triggered by the WT to initiate the release of the resources for a specific UE
The procedure uses UE-associated signalling

55. WT-initiated WT Release - Successful Operation
WT RELEASE REQUIRED message (WT->eNB)
eNB receipt : replies with the WT RELEASE CONFIRM message
WT RELEASE CONFIRM message (eNB->WT)
E-RABs To Be Released Item IE
DL Forwarding GTP Tunnel Endpoint IE : the WT may perform data forwarding of downlink packets for that bearer
WT receipt : start data forwarding and stop providing user data to the UE

56. WT Association Confirmation
This procedure is initiated by the WT to give confirmation to the eNB
a certain UE successfully associated
with the WLAN following a successful WT Addition Preparation procedure
The procedure uses UE-associated signalling

57. WT Association Confirm Procedure – Successful Operation
WT ASSOCIATION CONFIRMATION message (WT->eNB)
eNB receipt :
eNB consider that the UE is associated with the WLAN
that user plane data for that UE may be sent to the WT

58. Xw Data Transport
Data Link Layer: any data link protocol that fulfils the requirements toward the upper layer may be used
Transport Network Layer for Data Streams over Xw
GTP-U : General Packet Radio Service Tunneling Protocol – User Plane(用於為每個PDP context提供一個或多個隧道，用以傳輸用戶數據)
GTP :是一組基於IP的通信協議，用於在GSM、UMTS和LTE網絡中承載GPRS
There is one UL data stream (if flow control is supported) and one DL data stream per E-RAB at the Xw interface
DL(eNB->WT)
UL(WT->eNB)
Each data stream is carried on a dedicated transport bearer

59. Xw over UDP/IP Path protocol
The UDP port number for GTP-U shall be as defined in TS
The eNB and the WT over the Xw interface shall support fragmentation and assembly of GTP packets at the IP layer
There may be one or several IP addresses in both the eNB and the WT
The packet processing function in the source eNB shall send downstream packets corresponding toa given E-RAB to the target WT IP address (received in XwAP) associated to the DL transport bearer of that particular E-RAB
The packet processing function in the source WT shall send upstream packets corresponding to a given E-RAB to the target eNB IP address (received in XwAP) associated to the UL transport bearer of that particular E-RAB
The Transport Layer Address signalled in XwAP messages is a bit string of
32 bits in case of Ipv4 address according to IETF RFC 791
128 bits in case of Ipv6 address according to IETF RFC 2460

60. Diffserv Code Point Marking
IP Differentiated Services code point marking shall be supported
The mapping between traffic categories and Diffserv code points
Be configurable by O&M for based on QoS Class Identifier (QCI)/ Label Characteristics and others E-UTRAN traffic parameters
Traffic categories are implementation-specific
May be determined from the application parameters

61. LTE-WLAN Aggregation For the LWA bearer option
the GTP-U protocol over UDP over IP shall be supported as the transport for the downlink user data stream of LWA PDUs and the uplink flow control feedback stream on the Xw interface
The GTP-U PDU(Protocol Data Unit) includes a RAN Container with flow control information as specified in TS which is carried in the GTP-U extension header
The transport bearer is identified by the GTP-U TEID and the IP address of the eNB and WT respectively
The DL data stream is used for DL user data transmission from the eNB to the WT
The UL data stream is used for UL flow control feedback transmission from the WT to the eNB
the packet processing function in the eNB shall send downstream packets corresponding to a given E-RAB to the WT IP address (received in XwAP) associated to the DL transport bearer of that particular E-RAB. The packet processing function in the WT shall send upstream packets corresponding to a given E-RAB to the eNB IP address (received in XwAP) associated to the UL transport bearer of that particular E-RAB
in addition, user data forwarding (from WT to eNB ) may be performed by eNB providing another GTP-U TEID to receive the DL data forwarded by the WT

62. LWA Radio Protocol Architecture for the Non-Collocated Scenario

63. LWA Radio Protocol Architecture for the Collocated Scenario

64. Xw User Plane Protocol
Using services of the transport network layer in order to allow flow control of user data packets transferred over the Xw interface
Provision of Xw UP specific sequence number information for user data transferred from the eNB to the WT for a specific E-RAB configured with the LWA bearer option
Information of successful transmission towards or in sequence delivery to the UE of LWAAP PDUs from WT for user data associated with a specific E-RAB configured with the LWA bearer option
Information of LWA PDUs that were not transferred towards or not delivered to the UE
Information of the currently desired buffer size at the WT for transmitting to the UE user data associated with a specific E-RAB configured with the LWA bearer option
Information of the currently minimum desired buffer size at the WT for transmitting to the UE user data associated with all E-RABs configured with the LWA bearer option

65. Transfer of Downlink User Data
Services Expected from the Xw Transport Network Layer
Provide Xw-U specific sequence number information at the transfer of user data carrying a DL LWA PDU from the eNB to the WT via the Xw-U interface
An Xw user plane instance making use of the Transfer of Downlink User Data procedure is associated to a single E-RAB only. The Transfer of Downlink User Data procedure is invoked whenever user data for that particular E-RAB needs to be sent across the Xw-U interface.
The eNB shall assign consecutive Xw-U sequence numbers to each transferred Xw-U packet.
The WT shall detect whether an Xw-U packet was lost and memorise the respective sequence number after it has declared the respective Xw-U packet as being “lost”.
The WT shall transfer the remaining LWA PDUs towards the UE and memorise the highest Xw-U sequence number of the PDCP PDU that was successfully transferred towards or delivered to the UE.

66. Downlink Data Delivery Status
Provide feedback from the WT to the eNB to allow the eNB to control the downlink user data flow via the WT for the respective E-RAB
When the WT decides to trigger the Feedback for Downlink Data Delivery procedure it shall report:
a) the highest Xw-U sequence number successfully transferred towards or delivered to the UE among those PDUs received from the eNB;
b) the desired buffer size in bytes for the concerned E-RAB;
c) the minimum desired buffer size in bytes for the UE;
d) the Xw-U packets that were declared as being “lost” by the WT and have not yet been reported to the eNB within the DL DATA DELIVERY STATUS frame.

67. References LWA eLWA feLWA
Stage-2 high level description – TS , section 22A.1
Stage-3 data plane (PDCP) –TS
Stage-3 data plane (LWAAP) – TS
Stage-3 control plane (RRC) – various sections in TS
Stage-3 control plane network interface (Xw) – TS , TS , TS
Stage-3 data plane network interface (Xw) – TS TS
Stage-3 security aspects – TS , section X (section number to be allocated)
eLWA
Rel-14 eLWA Work Item Description (WID) - RP
feLWA
Rel-15 FeLWA Motivation – RP