Overview of Network Slicing and Features in 3GPP 5G Use Case Team
Network slicing in 3GPP's 5G architecture allows for the creation of logical networks with specific capabilities. The end-to-end slicing process involves various network functions like Access and Mobility Management Function (AMF), Session Management Function (SMF), and User Plane Function (UPF). S-NSSAI and NSSAI are used for slice identification and selection, while high-level processes for slice access detail PDU session establishment, SMF selection, and UPF selection. The processing inside 5G-RAN includes L2-Uplink, QoS flows, SDAP, Radio Bearers, and Security measures.
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Network Slicing (and related) Features in 3GPP 5G Use Case Team
E2E Slicing Network Slice: A logical network that provides specific network capabilities and network characteristics. Network Slice instance: A set of Network Function instances and the required resources (e.g. compute, storage and networking resources) which form a deployed Network Slice. High level constraints: - UE can access up to 8 slices via distinct PDU sessions (one PDU session can belong to only one slice) - Same AMF serves as control anchor for a given UE for all slices UE can access - 5G-RAN is conceptualized simply as slice-aware THIS VIEW IS LOGICAL: Where and how the individual functions are deployed, how resources are shared or dedicated not specified. NSSF NRF N22 AMF N11 SMF N4 N2 N1 SLICE X UPF UPF N3 UE gNB AMF: Access and Mobility Management Function SMF: Session Management Function UPF: User Plane Function NSSF: Network Slice Selection Function NRF: NF Resource Function SMF N3 N4 5G-RAN SLICE Y UPF UPF
High Level Process for Slice Access DN UE (R)AN AMF UPF PCF UDM SMF 1. PDU Session Establishment Request 2. SMF selection 3a. Namf_PDUSession_CreateSMContext Request Slice Information is carried and used in: UE to AMF PDU Session Request SMF selection procedure (may involve NSSF and NRF) Subscription retrieval by SMF Notifications by UDM SMF to AMF Message for PDU session context set up AMF to RAN Session Request 4a-4b. Registration/ Subscription retrieval/ Subscription for updates 5. Namf_PDUSession_CreateSMContext Response 6. PDU Session authentication/authorization 7a. PCF selection 7b.Session Management Policy Establishment or Modification 8. UPF selection 9. Session Management Policy Modification Slice identification & selection: Done via S-NSSAI and NSSAI S-NSSAI is comprised of Slice/Service type (SST) and a Slice Differentiator (SD) PDU Session Context in SMF, AMF, and RAN has 1-1 association between PDU session and S-NSSAI 10a. N4 Session Establishment/Modification Request 10b. N4 Session Establishment/Modification Response 11. Namf_Communication_N1N2MessageTransfer 12. N2 PDU Session Request (NAS msg) 13. AN-specific resource setup (PDU Session Establishment Accept) 14. N2 PDU Session Request Ack First Uplink Data 15. Nsmf_PDUSession_UpdateSMContext Request 16a. N4 Session Modification Request 16b. N4 Session Modification Response Slice/Service Type SST value 1 Characteristics. 17. Nsmf_PDUSession_UpdateSMContext Response eMBB Slice suitable for the handling of 5G enhanced Mobile Broadband. 18. Nsmf_PDUSession_SMContextStatusNotify 19. IPv6 Address Configuration Slice suitable for the handling of ultra- reliable low latency communications. Slice suitable for the handling of massive IoT. URLLC 2 First Downlink Data MIoT 3 20. Unsubscription / Deregistration
Processing inside 5G-RAN L2-Uplink with Carrier Aggregation L2-Downlink with Carrier Aggregation QoS Flows QoS Flows QoS flow handling QoS flow handling QoS flow handling SDAP SDAP Radio Bearers Radio Bearers ROHC ROHC ROHC ROHC ROHC ROHC PDCP PDCP Security Security Security Security Security Security RLC Channels RLC Channels Segm. ARQ Segm. ARQ Segm. ARQ Segm. ARQ RLC ... ... Segm. ARQ Segm. ARQ ... RLC ... Logical Channels Logical Channels Scheduling / Priority Handling Scheduling MAC Multiplexing UE1 Multiplexing UEn MAC Multiplexing HARQ HARQ HARQ HARQ HARQ HARQ Transport Channels Transport Channels CC1 ... CC1 ... CCx CCy CC1 ... CCx Individual carriers Ref. 3GPP TS 38.300
RAN Slicing Concepts (3GPP TS 38.300) RAN awareness of slices Differentiated handling of traffic for different network slices Selection of RAN part of the network slice Using UE or CN provided assistance information Resource management between slices Policy enforcement between slices as per service level agreements for each supported slice Support of QoS (within Slice) RAN selection of CN entity Selecting AMF for UE attachment (same AMF handles all slices that UE accesses) Resource isolation between slices Implementation dependent. Resources can be shared or dedicated. If shared RRM policies and protection mechanisms should be implemented. Slice Availability Local availability in parts of the network is supported. Slice availability should not change within UE s registration area. Support for UE associating with multiple network slices simultaneously One signalling connection is maintained. Granularity of slice awareness (per PDU session) Validation of the UE rights to access a network slice Mainly dictated by 5GC policies. NG-RAN may be allowed to apply local policies based on RAN awareness of the slice.
RAN Constraints (Related to Slicing) in 3GPP Rel 15 Slice availability S-NSSAI (i.e., slice) must be supported in all cells in a UE s registration area Change in supported NSSAI for Tracking Areas (TAs) induces UE re-registration Bandwidth Part (BWP) Each UE can have up to 4 BWP configured and only one is active at a given time Each BWP can be configured with a particular numerology Supported set of numerologies depend on the carrier frequency of BWP Slot Format Each slot is configured as one of 61 different UL-DL symbol allocation including flexible symbols (i.e., can be used for UL or DL based on scheduling) Different slot formats can be concatenated Can be modified by setting configuration parameters on UE side Flexible symbols are set as UL/DL using Download Control Information (DCI) NSSAI: Network Slice Selection Assistance Information S-NSSAI: Single Network Slice Assistance Information
Processing Slice Request Generate S-NSSAI Descriptor New Slice Slice Lifecycle Management Operationalize Request Analysis Slice Slice Slice Request Synthesis Onboarding Onboard/Configure 5G Functions with new S-NSSAI Manage Slice States, Policies, & Resources Grant Access to an existing S-NSSAI Data Collection Data Collection 5G CLOUD Infrastructure and Functions
E2E 5G Slice Dimensions Slice CN Function (i.e., AMF, SMF & UPF) Cloud Selection UE Profiles Descriptor Coverage CN Function Mobility Instantiation, Configuration, Selection Performance Requirements S-NSSAI RAN Selection (i.e., gNBs) RAN Function (L2) Traffic Characteristic Transport mode(s) & constraints Instantiation, Configuration, Selection Power Constraints Carrier & BWP Slot Format Numerology Radio Link (L1) Configuration Application Stack
For Casablanca? Assume 5G VNF/PNF instances are already onboarded - Each VNF/PNF in the ONAP inventory has a supported NSSAI profile - Before UE /CPE registration, 5G slice must be instantiated by ONAP ONAP constructs slice descriptor based on slice order, correlates the descriptor with the supported NSSAIs, picks a target NSSAI for the customer placing the slice order Instantiate and/or configure the functions for the target NSSAI E.g., update user subscription profiles and NSSF Trigger UE/CPE re-registration for UE/CPE start consuming the instantiated slice
s Thank You!
Appendix - Numerology and Slot Length Radio Frame (10 ms) Subframe (1ms) Slot 62.5us to 1ms Supported Numerologies = Cyclic prefix Normal Normal Normal, Extended Normal Normal 2 [kHz] 15 15 30 60 120 240 f 0 1 2 3 4 1 ms 0.5 ms 250 us 125 us 62.5 us Control only no data 1 slot = 14 Symbols (Normal), 12 Symbols (Extended)
Appendix Slot Format (3GPP TS 38.211) Format Symbol number in a slot 5 6 D D U U X X D D D D D D D D D D X X X X U U U U U U U U U U X U X X X X X X X X X X X X X X X X X X X X X X X X D D D D D D D D D D D D U U U U U U U U U U U U U U U U X U D D D X D X D X X X X X X X U U U U U U U U X U U U U U X U U U U U X U X U Reserved 0 D U X D D D D D X X X X X X X X D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D X X X X D D D D D D D D 1 D U X D D D D D X X U X X X X X X D D X D D X D D X D D D D D D D D X D D X D D X D D D D D D D D X U X X X D D X D D X X D 2 D U X D D D D D X X U U X X X X X X D X X D X X D X X D D D D D D D U X D X X D X X D D D D D D X X U U X X D X U D X X X X 3 D U X D D D D D X X U U U X X X X X X X X X X X X X X X D D D D D D U U X U X X X X X D D D D D X X U U U X D U U D X U X X 4 D U X D D D D D X X U U U U X X X X X X X X X X X X X X D D D D D D U U U U U X U X X D D D D D X X U U U U D U U X U U X X 7 D U X D D D D D X X U U U U U U X X X X X X X X X X X X D D D D D D U U U U U U U U U D X X D D D D X X X X D D D D D D D D 8 D U X D D D D D X X U U U U U U X X X X X X X X X X X X D D D D D D U U U U U U U U U D X U D D D X U X X X D D X D D X X D 9 D U X D D D D X X X U U U U U U X X X X X X X X X X X X D D D D D X U U U U U U U U U X X U D D X X U U X X D X U D X X X X 10 D U X D D D X X X X U U U U U U X X X X X X X X X X X X D D X D X X U U U U U U U U U X X U D D X X U U U X D U U D X U X X 11 D U X D D X X X X X U U U U U U X X X X X X X X X U U U D X X X X X U U U U U U U U U X X U D D X X U U U U D U U X U U X X 12 D U X D X X X X X U U U U U U U X X X X X X U U U U U U X X X U U U U U U U U U U U U X U U D X X X U U U U X U U X U U X X 13 D U X X X X X X U U U U U U U U X X X U U U U U U U U U U U U U U U U U U U U U U U U U U U X X X X U U U U U U U U U U U U 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 D: Downlink-only Symbol U: Uplink-only Symbol X: Flexible Symbol that can be scheduled for both UL & DL 62 255
