1. 助理教授：吳俊興 助教：楊文健 國立高雄大學 資訊工程學系
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:行動與無線區網整合
Week #07 RCLWI機制
助理教授：吳俊興
助教：楊文健
國立高雄大學 資訊工程學系

2. Outline Introduction of RCLWI Configure RCLWI Network Interfaces
Traffic Steering
UE Moving

3. RAN-Controlled LTE-WLAN Interworking (RCLWI)
Radio Access Network(RAN) : A RAN consists of the ground-based infrastructure required for delivery of communication between UEs and the Core Network (CN)
In LTE, the RAN consists of one or more base stations (i.e. eNodeBs)
RAN support for inter-operation with other systems (e.g., GSM/EDGE, UMTS, CDMA2000, WiMAX, etc.)

4. Functions of RCLWI
Share the same architecture as LWA but no LWA specific functions
Measurement and WLAN mobility set
Steering command R

5. E-UTRAN Can Configure The UE
E-UTRAN can configure the UE to connect to a WLAN and configure bearers for LWA (referred to as LWA bearers or LWA DRBs) or offload traffic to WLAN for RCLWI
The UE uses the WLAN parameters received from E-UTRAN in performing WLAN measurements and WLAN mobility
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6. RCLWI and RALWI
LTE in the Unlicensed Spectrum, March 29, 2016, Manuel Blanco Product Marketing engineer

7. RCLWI and RALWI
RAN- Assisted LTE-WLAN Interworking (RALWI – Rel 12) provides the UE with parameters and rules to help take the decision to steer to WLAN or LTE
RAN-Controlled LTE-WLAN Interworking (RCLWI – Rel 13) allows the Network Operator to control when and where to steer through a steering command:
RAN Controlled LTE WLAN Interworking (RCLWI), which builds upon 3GPP Rel-12 RAN Assisted
Greater control by the Operator
Harmonized with 3GPP handovers based on UE measurements
LTE in the Unlicensed Spectrum, March 29, 2016, Manuel Blanco Product Marketing engineer

8. E-UTRAN Configure RCLWI
E-UTRAN does not configure RCLWI with DC, LWA or LWIP simultaneously for the same UE
If RCLWI and RAN assisted WLAN interworking are simultaneously configured for the same UE, in RRC_CONNECTED, the UE only applies RCLWI
The UE uses the RCLWI procedures to perform access network selection and traffic steering decisions between 3GPP access and WLAN or using ANDSF policies defined in TS [2]
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9. RCLWI Same Architecture as LWA
Even though LWA and RCLWI are specified as part of the same WI, these are two very different capabilities and it is reasonable to assume that operators deploying LWA are unlikely to deploy RCLWI and vice versa
Therefore, 3GPP propose that LWA and RCLWI have separate capability indications and that both features should be optional
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WI = work item

10. E-UTRAN Support RCLWI for Controlling Traffic Steering
E-UTRAN supports E-UTRAN controlled bi-directional traffic steering between E-UTRAN and WLAN for UEs in RRC_CONNECTED
RRC_CONNECTED : Radio Resource Control protocol for the radio interface between UE and E-UTRAN as well as for the radio interface between RN and E-UTRAN
the radio related information transported in a transparent container between source eNB and target eNB upon inter eNB handover
- the radio related information transported in a transparent container between a source or target eNB and another system upon inter RAT handover
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11. RCLWI for Controlling Traffic Steering
When E-UTRAN sends an "offload" command to the UE, the UE passes an indication to the upper layers indicating that traffic steering to/from WLAN is needed
The upper layers determine to initiate traffic steering to/from WLAN based on the UE capability and the configuration information that has received from NAS layer indicating which PDN connections are offloadable
When the UE receives the "offload" command from the EUTRAN, the UE shall perform handover to WLAN only the PDN connections that have been authorized for offloading
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The NAS level indication about "offloadability" of PDN connections is defined in clause

12. Network Interfaces-General
Similarly as for LWA
In the non-collocated RCLWI scenario
the eNB is connected to one or more WT logical nodes via an Xw interface
In the collocated RCLWI scenario
the interface between LTE and WLAN is up to implementation
There is no user plane interface defined between the eNB and the WT in RCLWI
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13. C-Plane Connectivity of eNB and WT for LWA
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14. Network Interfaces-Control Plane
In the non-collocated RCLWI scenario, the Xw control plane interface (Xw-C) is defined between the eNB and the WT and is similar to what is defined for LWA in Figure
Figure C-Plane Connectivity of eNB and WT for LWA
LWA specific funtions are not part of RCLWI
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15. RCLWI interface
RCLWI is also based on WT and Xw interface upgrade of the WiFi network for control signaling, however, the User Plane (UP) bearers instead of going through the LTE eNB are routed through a CN with WiFi legacy link
This is rather a bearer handover (or an offload) than an aggregation compared to LWA, however still the UE is controlled by the network to receive the data from WiFi link, instead of taking this decision by itself
Compared to LWA, this solution doesn’t require the UE to be upgraded with LWAAP
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16. WLAN-Mobility Config
The UE stores the current WLAN mobility set, which is a non-empty set of WLAN identifiers, in wlan-MobilitySet in VarWLAN-MobilityConfig
This WLAN mobility set can be configured and updated via LWA-Configuration or RCLWI-Configuration
When the UE receives a new or updated WLAN mobility set, it initiates connection to a WLAN whose identifiers match all WLAN identifiers for at least one entry in wlan-MobilitySet R

17. WLAN-Mobility Config(Cont.)
If not already connected to WLAN, the UE can perform WLAN mobility within the WLAN mobility set (connect to another WLAN whose identifiers match the ones in wlan-MobilitySet) without any signalling to E-UTRAN R

18. Traffic Steering from E-UTRAN to WLAN

19. Traffic Steering from E-UTRAN to WLAN
The eNB sends the RRCConnectionReconfiguration message to the UE indicating the UE to steer traffic from E-UTRAN to WLAN
The UE forward the indication to upper layers and replies with RRCConnectionReconfigurationComplete message
The UE steers traffic from E-UTRAN to WLAN (subject to upper layer) after successful association to WLAN
If WLAN association failed, the UE sends WLANConnectionStatusReport message R R
Corrections to RCLWI procedure

20. Traffic Steering from WLAN to E-UTRAN
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The traffic steering from WLAN to E-UTRAN procedure is initiated by the eNB

21. Traffic Steering from WLAN to E-UTRAN
The eNB sends the RRCConnectionReconfiguration message to the UE indicating the UE to steer traffic fromWLAN to E-UTRAN
The UE forward the indication to upper layers and replies with RRCConnectionReconfigurationComplete message
The UE steers traffic from WLAN to E-UTRAN
The traffic steering from WLAN to E-UTRAN procedure is initiated by the eNB

22. Connected UE steering traffic from LTE to WLAN
Simplified call flow

23. Connected UE steering traffic from LTE to WLAN
In this call flow, eNB can trigger WT status request at any time in order to get the status information about WLAN APs (e.g. BSS load, backhaul rate, etc)
The failure report for unsuccessful traffic steering could be considered, e.g. eNB can reconfigure WLAN measurement
But there is no need to report for successful traffic steering
When the UE has selected a WLAN based on user preferences, the UE shall ignore the LWA/RCLWI signalling R

24. Connected UE steering traffic from WLAN to LTE
For connected UE, the procedure of steering traffic back from WLAN in R13 can be tightly controlled by eNB R

25. LTE Idle UE steering traffic from WLAN to LTE

26. LTE Idle UE steering traffic from WLAN to LTE
The eNB may release LTE RRC connection if all traffics are through WLAN after traffic steering
In order to avoid the eNB losing control fully for idle UE steering traffic back to LTE, some parameters applicable for idle UEs could be desirable R

27. Idle Mode UEs
For idle mode UEs, since LTE RRC connection has already been released, eNB can’t take tight control of the traffic steering to/from WLAN
In R12, dedicated WLAN offload parameters can be delivered through RRC connection reconfiguration, which can be used for the traffic steering in both idle mode and connected mode and from LTE to WLAN and from WLAN to LTE
In R13, for connected mode UEs, eNB can take tight control of the traffic steering from LTE to WLAN and from WLAN to LTE
支援R12 R13 For idle mode 的 UE

28. WLAN offload parameters for idle mode UE
The dedicated WLAN offload parameters for idle mode UE is considered, which can be delivered to UE through eNB
If eNB releases R13 RCLWI capable UEs to idle, then eNB can provide specific idle mode WLAN offload parameters to UE for traffic steering during RRC release procedure
支援R12 R13 For idle mode 的 UE

29. Connected UE steering traffic between WTs

30. Connected UE steering traffic between WTs
Based on the agreements of RAN2#90, UE mobility across mobility set (AP group) should be controlled by eNB based on WLAN measurement reports
For connected UE, it looks clear that eNB can take control of the WT change procedure

31. LTE Idle UE steering traffic between WTs

32. LTE Idle UE steering traffic between WTs
For Idle mode UE, in order to allow eNB to control UE mobility across mobility set (AP group), UE should be triggered for LTE connection setup while it detects that serving AP of mobility set is bad enough or neighbour AP is good enough

33. Moving towards to LWA capable eNB/ WLAN AP
For smooth switching between RCLWI and aggregation, the following scenarios could be considered
e.g. UE moves from RCLWI capable AP to LWA capable AP, or UE moves from RCLWI capable eNB to LWA capable eNB or vice versa

34. UE moving to LWA capable AP

35. Connected/Idle UE moving to LWA capable AP
UE moves from RCLWI capable AP to LWA capable AP and both APs connect to the same eNB
In order to allow eNB to get the information that UE is into the coverage of one AP which is aggregation capable, UE should also measure LWA capable APs which could be included as part of WLAN AP lists in WLAN measurement configuration for connected UE or WLAN offload configuration for idle UE
For connected UE, eNB can make further decision whether to activate LWA or not based on WLAN measurement reporting relevant to LWA capable APs

36. UE moving to LWA capable eNB

37. Connected/Idle UE moving to LWA capable eNB
UE moves from RCLWI capable eNB to LWA capable eNB
For connected UE, inter-eNB handover happens
The target eNB may activate aggregation for UE after handover

38. LTE Idle UE moving to LWA/RCLWI capable eNB

39. LTE Idle UE moving to LWA/RCLWI capable eNB
For idle UE, in order to allow UE to know being into the coverage of LWA capable eNB, eNB should broadcast one indicator to inform UEs
e.g. LWA capable indicator
And UE can trigger LTE RRC connection setup while it enters this LWA capable eNB and still has traffic on WLAN R

40. E-UTRAN Send A Steering Command to the UE
E-UTRAN may send a steering command to the UE indicating to steer traffic from E-UTRAN to WLAN or from WLAN to E-UTRAN
The upper layers in the UE shall be notified upon reception of such a command
Upper layers determine which traffic is offloadable to WLAN
Similarly as for LWA, two scenarios are supported depending on the backhaul connection between LTE and WLAN (non-collocated RCLWI scenario for a non-ideal backhaul and collocated RCLWI scenario for an ideal/internal backhaul)
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41. WLAN Measurements
The UE supporting RCLWI may be configured by the E- UTRAN to perform WLAN measurements
WLAN measurement object can be configured using WLAN identifiers (BSSID, HESSID and SSID), WLAN carrier information and WLAN band
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42. WLAN Measurements(Cont.)
WLAN measurement reporting is triggered using RSSI
WLAN measurement report contains, for each included WLAN, RSSI and WLAN identifier, and may contain WLAN carrier information, WLAN band, channel utilization, station count, admission capacity, backhaul rate and an indication whether the UE is connected to the WLAN
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43. ANDSF Co-existence with LWA and RCLWI
When the UE supports WLAN access selection and traffic routing based on the ANDSF procedures defined in 3GPP and based on the LWA/RCLWI procedures specified in 3GPP, then the UE shall support co-existence between these procedures as well as co-existence between these procedures and the user preferences by applying the following behaviour
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44. The UE Shall Accept The LWA/RCLWI signalling
When the UE has not selected a WLAN, the UE shall accept the LWA/RCLWI signalling and shall apply WLAN access selection and traffic routing based on the applicable LWA/RCLWI procedures
When the UE has selected a WLAN based on user preferences, the UE shall ignore the LWA/RCLWI signalling
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45. Selected A WLAN Based On ANDSF
When the UE has selected a WLAN based on ANDSF rules, the UE shall accept or shall ignore the LWA/RCLWI signalling based on the UE configuration
Specifically, the UE may be configured via the home ANDSF with an indication that specifies if the UE shall accept or ignore the LWA/RCLWI signalling in a specific PLMN and/or when connected to a specific WLAN access
If the UE is not configured via the home ANDSF with this indication, then the UE shall always accept the LWA/RCLWI signalling
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