LTE RRM introduction & ITRI L3-RRM SW 顏鴻傑 資通所 2015/08/25 Radio Resource Control

Outline RRM concept and key functions Sample code for RRM development

RRM concept and key functions

What’s RRM Definition: Goal: to allocate and manage the limited radio resource to maximize the system performance and capacity. Goal: ensure planned QoS of traffic ensure cell coverage ensure spectrum utilization

LTE features (1/6) RAN structure Most of RRM functions are located in eNB due to lack of the RRM server (a node to do multi-cell RRM) in E-UTRAN.

LTE features (2/6) System bandwidth allocation E-UTRAN supports 1.4/3/5/10/20 MHz bandwidths, while UTRAN FDD supports only 5MHz bandwidth. RRM is concerned that different bandwidths lead to different available resources and performance in frequency-selective scheduling.

LTE features (3/6) Multiple access techniques CDMA in UTRAN: both intra-cell and inter-cell UEs may generate interference. OFDMA/SC-FDMA in downlink/uplink in E-UTRAN: only inter-cell interference.

LTE features (4/6) Multiple antenna techniques LTE supports many MIMO modes and can dynamical switching among them. Physical resources in space dimension are different in the MIMO modes.

LTE features (5/6) Optimization of PS domain No CS domain in LTE. All traffic in PS domain are packets (i.e., variable length, bursty) and are defined by different parameters compared to CS domain. The parameters of each traffic are determined by many RRM processes.

QoS Class Identifier (QCI)

LTE features (6/6) Share channel No dedicated channel in LTE. All traffic share the physical resources which are allocated by packet scheduler. Specifically, eNB tells the UE the transmission resources (via control signaling) and takes back them when transmission completed. Packet scheduler in UMTS is constrained by the dedicated channel design.

LTE Interface for RRM

RRM key functions (Source: 3GPP TS 36.300)

Radio Admission Control RAC purpose: to admit or reject establishment requests for new radio bearers. RAC goal: to ensure high radio resource utilization by accepting radio bearer requests if radio resources are available. This simultaneously ensures proper QoS for in-progress sessions by rejecting radio bearer requests when they cannot be accommodated.

RAC process RAC is triggered when UE requests serving eNB to do RRC Connection establishment (i.e. add SRB configuration) MME requests serving eNB to do ERAB setup/modification (i.e. add/change DRB configuration such as QoS info) Source eNB requests target eNB to do handover preparation (i.e. add SRB and DRB configuration)

RAC process Example: bearer setup (Source: LONG TERM EVOLUTION: 3GPP LTE Radio and Cellular Technology, Auerbach Publications, 2009)

RAC process (Source: LONG TERM EVOLUTION: 3GPP LTE Radio and Cellular Technology, Auerbach Publications, 2009)

Radio Bearer Control RBC involves the establishment, maintenance and release of radio bearers. RBC is also concerned with the maintenance of radio bearers of in-progress sessions at the change of the radio resource situation due to mobility and so on. RBC is involved in the release of radio resources associated with radio bearers including at-session termination and handover.

RBC process When?

RBC process

RBC 提供 DRA 的 QoS 參數

Connection Mobility Control CMC oversees the management of radio resources related to idle or connected mode mobility. In connected mode, handover decisions may be based on UE/eNB measurements, neighbor cell load, traffic distribution, transport, hardware resources, and operator defined policies.

CMC process

Cell Selection (1/2) Initial Cell Selection Scan all RF channels in the E-UTRA bands Only search for the strongest cell on each carrier frequency Once a suitable cell is found this cell shall be selected Stored Information Cell Selection Stored information of carrier frequencies & optionally also information on cell parameters Cell Selection when leaving RRC_CONNECTED state According to redirectedCarrierInfo in RRCConnectionRelease if present (left to Redirect topic discusses)

Cell Selection (2/2) TS 36.304 – criterion S TS 36.331 – SIB1 q-RxLevMinOffset receive level q-RxLevMin max((p-MAX – 23), 0) [dB] [dB] quality q-QaulMin-r9 q-QaulMinOffset-r9 From PHY after Layer 1 Filtering, -140 ~ -44 [dBm] From PHY after Layer 1 Filtering, -19.5 ~ -3 [dB] q-RxLevMin in cellSelectionInfo IE in RRC SIB1, -70 ~ -22 [dBM] q-QualMin-r9 in CellSelectionInfo-v920 IE in RRC SIB1, -34 ~ -3 [dB] TS 36.304 – criterion S TS 36.331 – SIB1 TS 36.133 – RSRP mapping & RSRQ mapping Avoid “ping-pong” between different PLMNs q-RxLevMinOffset n cellSelectionInfo IE in RRC SIB1, 1 ~ 8 [dB] Avoid “ping-pong” between different PLMNs q-QualMinOffset-r9 in CellSelectionInfo-v920 IE in RRC SIB1, 1 ~ 8 [dB] p-MAX in RRC SIB1, -30 ~ 33 [dBm] Until now, only 1 UE power class defined, it specifies +23 dBm

Cell Re-selection Procedure

Cell Re-selection (1/7) Methods to provide cell reselection related information to the UE System information RRCConnectionRelease message Inheriting from another RAT at inter-RAT cell (re)selection Absolute priority For inter-frequency & inter-RAT frequency cell reselection only

Cell Re-selection (2/7) Step 1. Perform Measurements Intra-frequency If serving cell Srxlev > SIntraSearchP && Squal > SIntraSearchQ May not perform intra-freq. measurements Otherwise Shall perform intra-freq. measurements Inter-frequency & Inter-RAT Inter-freq. or Inter-RAT freq. with higher priority than serving freq. Shall perform inter-freq. or inter-RAT freq. measurements Inter-freq. or Inter-RAT freq. with equal or lower priority than serving freq. If serving cell Srxlev > SnonIntraSearchP && Squal > SnonIntraSearchQ May not perform inter-freq. or inter-RAT freq. measurements s-IntraSearchP-r9 or s-IntraSearch s-NonIntraSearchP-r9 or s-NonIntraSearch

Cell Re-selection (3/7) Step 2. Criteria (1/2) Higher priority E-UTRAN frequency than serving frequency If threshServingLowQ is present in SIB3 A cell fulfils Squal > ThreshX,HighQ during TreselectionEUTRA More than 1 second has elapsed since the UE camped on the current serving cell Otherwise A cell fulfils Srxlev > ThreshX,HighP during TreselectionEUTRA Lower priority E-UTRAN frequency than serving frequency Serving cell fulfils Squal < ThreshServing,LowQ && a cell fulfils Squal > ThreshX,LowQ during TreselectionEUTRA Serving cell fulfils Srxlev < ThreshServing,LowP && a cell fulfils Srxlev > ThreshX,LowP during TreselectionEUTRA Equal priority E-UTRAN frequency & Intra-frequency Fulfilling Criterion S during TreselectionEUTRA threshX-High threshServingLow threshX-Low

Cell Re-selection (4/7) Step 2. Criteria (2/2) [dB] [dB] From PHY after Layer 1 Filtering, -140 ~ -44 [dBm] From PHY after Layer 1 Filtering, -19.5 ~ -3 [dB] q-RxLevMin in InterFreqCarrierFreqInfo IE in RRC SIB5, -70 ~ -22 [dBM] q-QualMin-r9 in InterFreqCarrierFreqInfo IE in RRC SIB5, -34 ~ -3 [dB] p-MAX in RRC SIB5, -30 ~ 33 [dBm] Until now, only 1 UE power class defined, it specifies +23 dBm

Cell Re-selection (5/7) Step 3. Ranking (1/2) Intra-frequency: 0 or q-OffsetCell Inter-frequency: (q-OffsetFreq + q-OffsetCell) or q-OffsetFreq From PHY after Layer 1 Filtering, -140 ~ -44 [dBm]

Cell Re-selection (6/7) Step 3. Ranking (2/2) t-ReselectionEUTRA in RRC SIB3 or SIB5

Handover Procedure

L3 Measurement Measurements configuration In RRC connection reconfiguration Each UE may have different config

L3 Measurement Trigger Type Event Periodical Event A1 Event A2 Event B1 (Inter RAT) Event B2 (Inter RAT) Periodical ReportStrongestCells ReportCGI Event Measurement Report #1 Measurement Report #2 Measurement Report #1 Measurement Report #2 Event condition matched Event condition matched timeToTrigger reportInterval timeToTrigger reportInterval Start point of measurement reportAmount: r2 reportAmount: r2 ReportStrongdestCells Measurement Report #1 Measurement Report #2 Measurement Report #3 Measurement Report #4 reportInterval reportInterval reportInterval reportInterval Start point of measurement reportAmount: r4 ReportCGI Measurement Report Start point of measurement reportAmount: r1 (always set to r1)

Measurement Report 用途 Event Type 用途 A1 Serving becomes better than threshold 關閉量測 A2 Serving becomes worse than threshold 打開量測 A3 Neighbor becomes offset better than serving Intra/Inter-frequency handover A4 Neighbor becomes better than threshold Loading balance A5 Serving becomes worse than threshold1 and neighbor becomes better than threshold2 Intra/Inter-frequency handover,

Handover Type (1) (2) (3) (4) Intra E-UTRAN HO w/o S-GW relocation Intra E-UTRAN HO with S-GW relocation Intra E-UTRAN HO with MME/S-GW relocation Inter RAT HO

Dynamic Resource Allocation DRA (or Packet Scheduling, PS) allocates and de-allocates resources including buffering and processing resources and resource blocks to user and control plane packets.

DRA jobs To determine the available radio resources for NRT bearers. NRT: non real-time (a.k.a. non-GBR in LTE) To determine the available radio resources for NRT bearers. To share the available radio resources between NRT bearers. To monitor the allocations for NRT bearers. To monitor the system loading. To perform load control actions for NRT bearers (optional).

Basic scheduling policy Round Robin (RR): Channel condition is not taken into account. Max Carrier-to-Interference (C/I) User with the best channel quality is scheduled. Proportional Fair (PF) Short-term channel variations are exploited while maintaining long-term average user data rate. Algorithm Throughput Fairness Complexity Channel tracking QoS guarantee RR low best no Max C/I highest bad middle yes PF higher better

L2 Scheduler framework Protocol stack (DL process) (UL process) (per UE/bearer) (DL process) (per TTI, per UE) (scrambled by RNTI) (per PRB, per TTI) Upper scheduler (UL process) (per TTI, per UE) Lower scheduler (scrambled by RNTI) (per PRB, per TTI) (MAC signaling) (Source: LONG TERM EVOLUTION: 3GPP LTE Radio and Cellular Technology, Auerbach Publications, 2009)

Load balancing Task: to balance traffic load over multiple inter-frequency and inter-RAT cells. Vertical v.s. horizontal LB: LB among (geographically) overlapped cells LB among neighbor cells

Load balancing 處理 eNBs 常規性的負載 保持無線資源的高度利用 保證已存在的連線的QoS 維持較低的通話遺失率 Overload indication RAC CMC 處理 eNBs 常規性的負載 保持無線資源的高度利用 保證已存在的連線的QoS 維持較低的通話遺失率 調整 Handover ( Handover ) threshold LB 調整 Cell re - CMC selection 參數 ( Cell re - LB 的主要目的 selection ) LB 與其他 RRM 模組的關係

Load balancing Intra-LTE considerations: resource utilization, hardware load, transport layer load. Inter-RAT considerations: available resource, maximum throughput, maximum UE number other considerations: UE capability, current traffic status, subscriber’s priority,…

Inter-Cell Interference Coordination ICIC manages radio resource blocks to keep inter-cell interference under control, based on the feedback from multiple cells. Multi-cell RRM approach: to takes into account resources and loads situation in multiple cells

Sample code for RRM development – ENBD

ENBD module decomposition Config. & CLI RRM RRC handler X2AP handler S1AP handler User data forwarding Gateway/NAT (raw socket) Serving eNB (RRC) Neighbor eNB MME Serving eNB (PDCP) Control-plane data User-plane data

Software component (1/5) RRM Core RRM function development. Source files: enbd\src\rrm\ RRC handler Handle interaction of RRM with RRC about cell and UE control procedure. enbd\src\rrc\ RRC interface files: enbd\src\rrc\new\

Software component (2/5) S1AP handler Handle interaction of RRM with S1AP about cell and UE control procedure. Source files: enbd\src\s1ap\ X2AP handler Handle interaction of RRM with X2AP about cell and UE control procedure. enbd\src\x2ap\

Software component (3/5) User data forwarding Route user data from PDCP to LAN gateway and vice versa (on a per bearer basis). Source files: enbd\src\gtpu\ Connection database Maintain UE and its bearer contexts (shared among all components). enbd\src\connection\

Software component (3/5) Neighbor database Maintain neighbor cell contexts (shared among all components). Source files: enbd\src\nbr\ Config & CLI Config: load software/cell/UE common parameters when ENBD software startup (called by main function). CLI: implement user input command to dynamic configure parameters or trigger procedures. enbd\enbd\ *CLI: Command-line interface

Software component (5/5) Other libraries: Raw socket wrapper: enbd\src\drv\ Common & Sys lib: enbd\src\

RAC development Case 1: UE requests serving eNB to do RRC Connection establishment (i.e. add SRB configuration) UE RRC RRM MME random access RRCConnectionRequest 1. RRC_CON_IND RAC 2. RRC_CON_SETUP_REQ RRCConnectionSetup RRCConnectionSetupComplete 3. RRC_CON_SETUP_CFM 4. S1AP_INIT_UE_MSG

RAC development Case 1: Call flow (1/2) rrm_process_prim() rrc_receive() prim_UeAdmission rrc_process_lower() rrm_process_UeAdmission() 1. RRC_CON_IND rrc_cell_process_ConnSetup_requested() rrc_process_prim() prim_UeAdmission prim_ConnSetupReq rrc_ctx_send_rrmprim() rrc_cell_process_rrm() rrc_cell_create_ConnSetup() 2. RRC_CON_SETUP_REQ rrc_send()

RAC development Case 1: Call flow (2/2) rrc_receive() s1ap_receive_prim() prim_InitConn rrc_process_lower() s1ap_client_process_rrm() 3. RRC_CON_SETUP_CFM rrc_cell_process_ConnSetup_confirmed() s1ap_client_create_InitUeMsg() prim_InitConn 4. S1AP_INIT_UE_MSG rrc_ctx_send_s1prim() s1ap_send()

2. RRC_CON_RECONFIG_REQ RAC development Case 2: MME requests serving eNB to do ERAB setup/modification (i.e. add/change DRB configuration such as QoS info) UE RRC RRM MME 1. S1AP_INIT_CTX_SETUP_REQ RAC + RBC 2. RRC_CON_RECONFIG_REQ RRCConnectionReconfiguration w/ MeasConfig RRCConnectionReconfigurationComplete 3. RRC_CON_RECONFIG_CFM 4. S1AP_INIT_CTX_SETUP_RSP

RAC development Case 2: Call flow (1/3) rrc_receive() s1ap_receive() rrc_process_prim() prim_SetupConn rrc_process_lower() s1ap_process_sctp() rrc_cell_process_rrm() 1.2 RRC_SEC_ACTV_CFM 1. S1AP_INIT_CTX_SETUP_REQ rrc_cell_process_SecActv_confirmed() s1ap_client_process_sctp() rrc_cell_create_SecActvReq() prim_SetupConnAck prim_SetupConn 1.1 RRC_SEC_ACTV_REQ rrc_cell_create_UeCapReq() s1ap_ctx_send_prim() rrc_send() 1.3 RRC_UE_CAP_REQ rrc_send()

RAC development Case 2: Call flow (2/3) rrm_process_prim() rrc_receive() prim_AddDrb rrm_process_AddBearer() rrc_process_lower() 1.4 RRC_UE_CAP_CFM rrc_process_prim() rrc_cell_process_UeCap_confirmed() prim_AddDrbAck prim_AddBearer rrc_cell_process_rrm() rrc_ctx_send_internal() rrc_cell_create_ConnReconfigReq() 2. RRC_CON_RECONFIG_REQ rrc_send()

RAC development Case 2: Call flow (2/3) rrc_receive() s1ap_receive_prim() prim_SetupConnAck rrc_process_lower() s1ap_client_process_rrm() 3. RRC_CON_RECONFIG_CFM rrc_cell_process_ConnReconf_confirmed() s1ap_client_create_InitCtxSetupRsp() prim_SetupConnAck 4. S1AP_INIT_CTX_SETUP_RSP rrc_ctx_send_s1prim() s1ap_send()

RAC development Case 3: Source eNB requests target eNB to do handover preparation (i.e. add SRB + DRB config) Source eNB UE RRC RRM MME 1. X2AP_HO_REQ 2. RRC_HO_PREPAR_REQ 3. RRC_HO_PREPAR_CFM RAC + RBC 4. RRC_HO_RSV_REQ 5. RRC_HO_RSV_CFM 6. X2AP_HO_REQ_ACK RRCConnectionReconfiguration (MobilityInfo of target cell) RRCConnectionReconfigurationComplete 7. RRC_HO_CFM_IND 8. S1AP_PS_REQ 9. S1AP_PS_RSP 10. RRC_HO_PS_IND 11. X2AP_UE_RELEASE

RAC development Case 3: Call flow (1/5) x2ap_receive() rrc_process_prim() prim_SetupHoConn x2ap_process_sctp() rrc_cell_process_rrm() 1. X2AP_HO_REQ rrc_cell_create_HoPrepReq() x2ap_client_process_sctp() prim_SetupHoConn 2. RRC_HO_PREPAR_REQ x2ap_ctx_send_prim() rrc_send()

RAC development Case 3: Call flow (2/5) rrm_process_prim() rrc_receive() prim_HoAdmission rrm_process_HoAdmission() rrc_process_lower() 3. RRC_HO_PREPAR_CFM rrc_process_prim() rrc_cell_process_HoPrep_confirmed() prim_HoAdmissionAck prim_HoAdmission rrc_cell_process_rrm() rrc_ctx_send_internal() rrc_cell_create_HoRsvReq() 4. RRC_HO_RSV_REQ rrc_send()

RAC development Case 3: Call flow (3/5) rrc_receive() x2ap_receive_prim() prim_SetupHoConnAck rrc_process_lower() x2ap_client_process_rrm() 5. RRC_HO_RSV_CFM rrc_cell_process_HoRsv_confirmed() x2ap_peer_create_HoReqAck() prim_SetupHoConnAck 6. X2AP_HO_REQ_ACK rrc_ctx_send_x2prim() x2ap_send()

RAC development Case 3: Call flow (4/5) rrc_receive() s1ap_receive_prim() prim_PathSwitch rrc_process_lower() s1ap_client_process_rrm() 7. RRC_HO_CFM_IND rrc_cell_process_HoCmp_confirmed() s1ap_client_create_PsReq() prim_PathSwitch 8. S1AP_PS_REQ rrc_ctx_send_s1prim() s1ap_send()

RAC development Case 3: Call flow (5/5) s1ap_receive() rrc_process_prim() x2ap_receive_prim() prim_PathSwitchAck prim_UeRelease s1ap_process_sctp() rrc_cell_process_rrm() x2ap_client_process_rrm() 9. S1AP_PS_RSP s1ap_client_process_sctp() rrc_cell_create_PsInd() x2ap_peer_create_UeRelease() prim_PathSwitchAck 10. RRC_HO_PS_IND 11. X2AP_UE_RELEASE s1ap_ctx_send_prim() rrc_send() x2ap_send() prim_UeRelease rrc_ctx_send_x2prim()

2. RRC_CON_RECONFIG_REQ RBC development Case 1: MME requests serving eNB to do ERAB setup (i.e. add DRB configuration such as QoS info) UE RRC RRM MME 1. S1AP_ERAB_SETUP_REQ RAC + RBC 2. RRC_CON_RECONFIG_REQ RRCConnectionReconfiguration RRCConnectionReconfigurationComplete 3. RRC_CON_RECONFIG_CFM 4. S1AP_ERAB_SETUP_RSP

RBC development Case 1: Call flow (1/2) rrm_process_prim() s1ap_receive() prim_AddDrb rrm_process_AddBearer() s1ap_process_sctp() 1. S1AP_ERAB_SETUP_REQ rrc_process_prim() s1ap_client_process_sctp() prim_AddBearerAck rrc_cell_process_rrm() prim_AddDrb s1ap_ctx_send_prim() rrc_cell_create_ConnReconfigReq() 2. RRC_CON_RECONFIG_REQ rrc_send()

RBC development Case 1: Call flow (2/2) rrc_receive() s1ap_receive_prim() prim_AddBearerAck rrc_process_lower() s1ap_client_process_rrm() 3. RRC_CON_RECONFIG_CFM rrc_cell_process_ConnReconf_confirmed() s1ap_client_create_ErabSetupRsp() prim_AddBearerAck 4. S1AP_ERAB_SETUP_RSP rrc_ctx_send_s1prim() s1ap_send()

2. RRC_CON_RECONFIG_REQ RBC development Case 2: MME requests serving eNB to do ERAB modify (i.e. change DRB configuration) UE RRC RRM MME 1. S1AP_ERAB_MOD_REQ (RAC) + RBC 2. RRC_CON_RECONFIG_REQ RRCConnectionReconfiguration RRCConnectionReconfigurationComplete 3. RRC_CON_RECONFIG_CFM 4. S1AP_ERAB_MOD_RSP

RBC development Case 2: Call flow (1/2) rrm_process_prim() s1ap_receive() prim_ModBearer rrm_process_ModifyBearer() s1ap_process_sctp() 1. S1AP_ERAB_MOD_REQ rrc_process_prim() s1ap_client_process_sctp() prim_ModBearerAck prim_ModBearer rrc_cell_process_rrm() s1ap_ctx_send_prim() rrc_cell_create_ConnReconfigReq() 2. RRC_CON_RECONFIG_REQ rrc_send()

RBC development Case 2: Call flow (2/2) rrc_receive() s1ap_receive_prim() prim_ModBearerAck rrc_process_lower() s1ap_client_process_rrm() 3. RRC_CON_RECONFIG_CFM rrc_cell_process_ConnReconf_confirmed() s1ap_client_create_ErabModRsp() prim_ModBearerAck 4. S1AP_ERAB_MOD_RSP rrc_ctx_send_s1prim() s1ap_send()

2. RRC_CON_RECONFIG_REQ RBC development Case 3: MME requests serving eNB to do ERAB release (i.e. delete DRB configuration). RBC may adjust other DRBs as well. UE RRC RRM MME 1. S1AP_ERAB_REL_CMD RBC 2. RRC_CON_RECONFIG_REQ RRCConnectionReconfiguration RRCConnectionReconfigurationComplete 3. RRC_CON_RECONFIG_CFM 4. S1AP_ERAB_REL_RSP

RBC development Case 3: Call flow (1/2) rrm_process_prim() s1ap_receive() prim_RelBearer s1ap_process_sctp() rrm_process_ReleaseBearer() 1. S1AP_ERAB_REL_CMD rrc_process_prim() s1ap_client_process_sctp() prim_RelBearer prim_RelBearerAck rrc_cell_process_rrm() s1ap_ctx_send_rrmprim() rrc_cell_create_ConnReconfigReq() 2. RRC_CON_RECONFIG_REQ rrc_send()

RBC development Case 3: Call flow (2/2) rrc_receive() s1ap_receive_prim() prim_RelBearerAck rrc_process_lower() s1ap_client_process_rrm() 3. RRC_CON_RECONFIG_CFM rrc_cell_process_ConnReconf_confirmed() s1ap_client_create_ErabRelRsp() prim_RelBearerAck 4. S1AP_ERAB_REL_RSP rrc_ctx_send_s1prim() s1ap_send()

CMC-HO development Part 1: Source eNB may setup/modify/remove L3 measurement configurations for the UE dynamically. UE RRC RRM L3_MEAS 1. RRC_CON_RECONFIG_REQ RRCConnectionReconfiguration RRCConnectionReconfigurationComplete 2. RRC_CON_RECONFIG_CFM loop MeasurementReport 3. RRC_MEAS_REPORT_IND

CMC-HO development Part 1: Call flow (1/2) 1. RRC_CON_RECONFIG_REQ rrc_receive() rrm_cmc_evaluate_MeasConfig() rrc_process_lower() rrc_process_prim() 2. RRC_CON_RECONFIG_CFM prim_MeasConfig rrc_cell_process_rrm() rrc_cell_process_ConnReconf_confirmed() rrc_cell_create_ConnReconfigReq() 1. RRC_CON_RECONFIG_REQ rrc_send()

CMC-HO development Part 1: Call flow (2/2) rrc_receive() rrc_process_lower() 3. RRC_MEAS_REPORT_IND rrc_cell_process_ConnReconf_confirmed() prim_MeasReport rrc_ctx_send_internal()

CMC-HO development Part 2: Source eNB make handover decision (i.e., choose the target cell for the UE to be hand-off). Target eNB UE RRC RRM HO decision 1. RRC_HO_INFO_REQ 2. RRC_HO_INFO_CFM 3. X2AP_HO_REQ 4. X2AP_HO_REQ_ACK 5. RRC_HO_CMD_REQ (w/ RRCConnectionReconfiguration) RRCConnectionReconfiguration 6. RRC_HO_CMD_CFM RRCConnectionReconfigurationComplete 7. X2AP_UE_RELEASE 8. RRC_CON_REL_REQ 9. RRC_CON_REL_CFM

CMC-HO development Part 2: Call flow (1/4) rrc_receive() rrm_cmc_evaluate_HoConfig() rrc_process_lower() rrc_process_prim() 2. RRC_HO_INFO_CFM prim_HoRequired rrc_cell_process_rrm() rrc_cell_process_HoInfo_confirmed() prim_PrepHoConn rrc_cell_create_HoInfoReq() rrc_ctx_send_x2prim() 1. RRC_HO_INFO_REQ rrc_send()

CMC-HO development Part 2: Call flow (2/4) x2ap_receive_prim() prim_PrepHoConn x2ap_process_sctp() x2ap_client_process_rrm() 4. X2AP_HO_REQ_ACK x2ap_peer_create_HoReq() x2ap_client_process_sctp() 3. X2AP_HO_REQ prim_PrepHoConnAck x2ap_send() x2ap_ctx_send_prim()

CMC-HO development Part 2: Call flow (3/4) 5. RRC_HO_CMD_REQ rrc_receive() rrc_process_prim() prim_PrepHoConnAck rrc_process_lower() rrc_cell_process_rrm() 6. RRC_HO_CMD_CFM rrc_cell_create_HoCmdReq() rrc_cell_process_HoCmd_confirmed() 5. RRC_HO_CMD_REQ prim_PrepHoConn rrc_send() rrc_ctx_send_x2prim()

CMC-HO development Part 2: Call flow (4/4) rrc_receive() x2ap_receive() rrc_process_prim() rrc_process_lower() prim_UeRelease x2ap_process_sctp() rrc_cell_process_rrm() 9. RRC_CON_REl_CFM 7. X2AP_UE_RELEASE rrc_cell_process_ConnReL_confirmed() x2ap_client_process_sctp() rrc_cell_create_ConnRelReq() prim_UeRelease 8. RRC_CON_REL_REQ x2ap_ctx_send_prim() rrc_send()

CMC-Idle development For UE cell reselection: (re-)configure cell broadcast info (i.e., SIB3 and SIB4/SIB5 parameters). RRC RRM CMC-Idle 1. RRC_SIB3_CFG_REQ 2. RRC_SIB3_CFG_CFM option 3. RRC_SIB4_CFG_REQ 4. RRC_SIB4_CFG_CFM option 5. RRC_SIB5_CFG_REQ 6. RRC_SIB5_CFG_CFM

CMC-Idle development Call flow 1. RRC_SIB3_CFG_REQ rrc_receive() rrm_cmc_evaluate_CellCofig() rrc_process_lower() rrc_process_prim() 2. RRC_SIB3_CFG_CFM prim_CellReconfig rrc_cell_process_rrm() rrc_cell_process_Sib3_confirmed() rrc_cell_process_CellReconfig_requested() rrm_cell_pack_cellSetup() 1. RRC_SIB3_CFG_REQ rrc_send()

LB development load control for idle UE load control for connected UE: Configure SIB (similar to CMC-Idle). load control for connected UE: Reject lower priority UE/RB during RAC procedure. Configure CMC-HO threshold.

L2 measurement eNB L2 measurement provisioning MAC provides cell-level load info to assist LB (and RAC/CMC as well) on demand. RRC RRM RRC_L2_MEAS_REQ (type=PRB_USAGE, interval=T) Interval=T RRC_L2_MEAS_IND

Thanks for your time. We hope this introduction is helpful.