LTE Review EPS Architecture Protocol Architecture Air Interface DL Scheduling EMM, ECM, RRC States QoS, s & EPS Bearers
Evolved Packet System (EPS) Architecture S6a HSS MME PCRF S1-MME S10 S11 Gxc Gx E-UTRAN Serving GW PDN GW Internet S1-U S5 SGi Evolved Packet Core (EPC) Control plane User plane EPS comprises EPC, E-UTRAN and UE E-UTRAN, i.e. enb performs radio access functions EPC provides connectivity & performs mobility & user management functions separation between C Plane and U Plane in EPC 2
EPS Protocol Architecture (U Plane) Application IP IP PDCP PDCP Relay GTP-U GTP-U Relay GTP-U GTP-U RLC RLC UDP/IP UDP/IP UDP/IP UDP/IP MAC MAC L2 L2 L2 L2 L1 L1 L1 L1 L1 L1 LTE-Uu S1-U S5/S8 SGi UE enodeb Serving GW PDN GW LTE-Uu: radio interface (UE - enb) GPRS Tunneling Protocol for the user plane (GTP-U): tunnels user data between enodeb and the S-GW as well as between the S- GW and the P-GW 3
Downlink Scheduling & Resource Allocation Channel dependent scheduling is supported in both time and frequency domain enables two dimensional flexibility Scheduler chooses bandwidth allocation, modulation and coding set (MCS), MIMO mode, and power allocation 14 OFDM symbols <=3 OFDM symbols for L1/L2 control UE A UE B UE C Frequency (180 khz) 12 subcarriers Time Slot = 0.5ms Slot = 0.5ms Total number of RBs available depends on the operating bandwidth Bandwidth (MHz) 1.4 3.0 5.0 10.0 15.0 20.0 Number of available resource blocks 6 15 25 50 75 100 4
RRC States UMTS LTE GSM/GPRS Connection establishment/release RRC States incl. Inter-RAT mobility (3GPP only) 5
Relation between EMM, ECM and RRC States EMM-Deregistered Attach EMM-Registered PLMN/ Cell Selection PLMN/ Cell Selection Attach Handover UE Inactivity Detection TAU Accept Cell Reselection A ECM-Idle B ECM-Idle C ECM-Connected D ECM-Idle RRC-Idle Power is turned off for a long time RRC-Idle RRC-Connected RRC-Idle Power On Power On Detach Attach Reject TAU Reject UE Power Off New Traffic TAU Request UE Power Off Adapted from www.netmanias.com 6
EMM, ECM and RRC States User View Case State User Experiences (Examples) C D EMM-Registered + ECM-Connected + RRC-Connected EMM-Registered + ECM-Idle + RRC-Idle UE is attached to the network (an MME) and is using services (e.g. Internet, VoIP, Live TV) Mobility handled by handover procedures UE is attached to the network (an MME), but not using any service Mobility handled by cell reselection procedures 7
EPS Bearer and Signaling Connections in EMM-registered State State C: EMM-Registered ECM-Connected RRC-Connected MME UE enb S-GW P-GW Control Plane ECM Connection/Signaling Conn. RRC Connection S1 Signaling Connection S11 GTP-C S5 GTP-C Data Plane Data Radio Bearer EPS Bearer S1 Bearer S5 Bearer 8
EPS Bearer and Signaling Connections in EMM-registered State State D: EMM-Registered ECM-Idle RRC-Idle MME UE enb S-GW P-GW Control Plane ECM Connection/Signaling Conn. RRC Connection S1 signaling Connection S11 GTP-C S5 GTP-C Data Plane Data Radio Bearer EPS Bearer S1 Bearer S5 Bearer 9
QoS Class Identifiers (s) Resource Type Priority Packet Delay Budget Packet Error Loss Rate 1 2 100 ms 10-2 Conversational Voice 2 Example Services 4 150 ms 10-3 Conversational Video (Live Streaming) 3 3 50 ms 10-3 Real Time Gaming 4 5 300 ms 10-6 Non-Conversational Video (Buffered Streaming) 5 1 100 ms 10-6 IMS Signalling 6 6 300 ms 10-6 TCP-based (e.g., www, e-mail, chat, ftp, Video (Buffered Streaming) p2p file sharing, progressive video, etc.) 7 Non- 7 100 ms 10-3 Video (Live Streaming) Voice, Interactive Gaming 8 8 Video (Buffered Streaming) TCP-based (e.g., www, e-mail, chat, ftp, 300 ms 10-6 p2p file sharing, progressive video, etc.) 9 9 10
EPS bearer QoS definition s represent type of traffic, i.e handling wrt latency, error correction and data rate (throughput itself not included) Throughput, i.e. Guaranteed Bit Rate () and Maximum Bit Rate () TFT (Traffic Flow Template), i.e. the rules to identify external flows (Service Data Flows SDFs) and to map them to a specific EPS bearer comprising IP source and destination, port numbers, protocol ID, etc. (Admission and Retention Policy) for overload handling UE enb S-GW P-GW Application APN- A Default Bearer (Non- ) Dedicated Bearer (Non- ) UE- A APN- A Dedicated Bearer () 11 o (DL) (DL)
Mapping of External Flows on EPS bearers EPS bearers (inside EPS) SDFs (outside EPS) UE enb S-GW P-GW PDN Application APN- A Default Bearer (Non-) Dedicated Bearer (Non- ) Dedicated Bearer () UE- A (UL/DL ) APN- A (DL) (DL) (UL/DL ) (UL/DL ) (UL/DL ) Mapping of external SDFs to EPS bearers via TFTs Source: www.netmanias.com Mapping of external Service Data Flows (SDFs) on EPS bearers is implemented at the edges of the network, i.e. UE and P-GW Legend: - : Guaranteed Bit Rate - : Maximum Bit Rate - A: Aggregated - APN-A: APN-specific 12