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

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

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.) https://en.wikipedia.org/wiki/E-UTRA

Functions of RCLWI Share the same architecture as LWA but no LWA specific functions Measurement and WLAN mobility set Steering command R2-161352

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 36.300

RCLWI and RALWI LTE in the Unlicensed Spectrum, March 29, 2016, Manuel Blanco Product Marketing engineer

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

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 23.402 [2] 36.300

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 36.300 WI = work item

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 36.300 23.401

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 36.300 23.401 The NAS level indication about "offloadability" of PDN connections is defined in clause 4.3.23.

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 36.300

C-Plane Connectivity of eNB and WT for LWA 36.300

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 36.300

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 https://www.grandmetric.com/2017/01/16/lte-advanced-pro-with-wifi-ran-level-integration/ 36.300

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 R2-161352

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 R2-161352

Traffic Steering from E-UTRAN to WLAN

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 R2-161352 R2-164733 Corrections to RCLWI procedure

Traffic Steering from WLAN to E-UTRAN 36300 The traffic steering from WLAN to E-UTRAN procedure is initiated by the eNB

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

Connected UE steering traffic from LTE to WLAN Simplified call flow

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 R2-161352

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 R2-161352

LTE Idle UE steering traffic from WLAN to LTE

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 R2-161352

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

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

Connected UE steering traffic between WTs

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

LTE Idle UE steering traffic between WTs

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

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

UE moving to LWA capable AP

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

UE moving to LWA capable eNB

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

LTE Idle UE moving to LWA/RCLWI capable eNB

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 R2-161352

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) 36.300

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 36.300

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 36.300

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 23.402

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 23.402

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 23402