3G Long-term Evolution (LTE) and System Architecture Evolution (SAE)

Transcription

1 3G Long-term Evolution (LTE) and System Architecture Evolution (SAE) Background Evolved Packet System Architecture LTE Radio Interface Radio Resource Management LTE-Advanced

2 3GPP Evolution Background Discussion started in Dec 2004 State of the art then: The combination of HSDPA and E-DCH provides very efficient packet data transmission capabilities, but UMTS should continue to be evolved to meet the ever increasing demand of new applications and user expectations. 10 years have passed since the initiation of the 3G programme and it is time to initiate a new programme to evolve 3G which will lead to a 4G technology. From the application/user perspectives, the UMTS evolution should target at significantly higher data rates and throughput, lower network latency, and support of always-on connectivity. From the operator perspectives, an evolved UMTS will make business sense if it: Provide significantly improved power and bandwidth efficiencies Facilitate the convergence with other networks/technologies Reduce transport network cost Limit additional complexity Evolved-UTRA is a packet only network there is no support of circuit switched services (no MSC) Evolved-UTRA started on a clean state everything was up for discussion including the system architecture and the split of functionality between RAN and CN Led to 3GPP Study Item (Study Phase: Q2006) 3G Long-term Evolution (LTE) for new Radio Access and System Architecture Evolution (SAE) for Evolved Network 2

3 LTE Requirements and Performance Targets High Peak Data Rates 100 Mbps DL (20 MHz, 2x2 MIMO) 50 Mbps UL (20 MHz, 1x2) Improved Spectrum Efficiency 3-4x HSPA Rel 6 in DL* 2-3x HSPA Rel 6 in UL 1 bps/hz broadcast * Assumes 2x2 in DL for LTE, but 1x2 for HSPA Rel 6 Improved Cell Edge Rates Support Scalable BW 1.4, 3, 5, 10, 15, 20 MHz 2-3x HSPA Rel 6 in DL* 2-3x HSPA Rel 6 in UL Full broadband coverage Low Latency < 5ms user plane (UE to RAN edge) <100ms camped to active < 50ms dormant to active Packet Domain Only High VoIP capacity Simplified network architecture 3

4 Key Features of LTE to Meet Requirements Selection of OFDM for the air interface Less receiver complexity Robust to frequency selective fading and inter-symbol interference (ISI) Access to both time and frequency domain allows additional flexibility in scheduling (including interference coordination) Scalable OFDM makes it straightforward to extend to different transmission bandwidths Integration of MIMO techniques Pilot structure to support 1, 2, or 4 Tx antennas in the DL and MU-MIMO in the UL Simplified network architecture Reduction in number of logical nodes flatter architecture Clean separation of user and control plane 4

5 Network Simplification: From 3GPP to 3GPP LTE 3GPP architecture Control plane 4 functional entities on the control plane and user plane 3 standardized user plane & control plane interfaces GGSN SGSN RNC NodeB User plane Control plane MME MMF ASGW S-GW enodeb User plane S-GW: Serving Gateway MME: Mobility Management Entity enodeb: Evolved NodeB 3GPP LTE architecture 2 functional entities on the user plane: enodeb and S-GW SGSN control plane functions S-GW & MME Less interfaces, some functions disappeared 4 layers into 2 layers Evolved GGSN integrated S-GW Moved SGSN functionalities to S-GW. RNC evolutions to RRM on a IP distributed network for enhancing mobility management. Part of RNC mobility function moved to S-GW & enodeb 7

6 Evolved UTRAN Architecture Key elements of network architecture No more RNC RNC layers/functionalities moves in enb X2 interface for seamless mobility (i.e. data/ context forwarding) and interference management Note: Standard only defines logical structure/ Nodes! MME/S-GW S1 S1 S1 enb MME/S-GW S1 S1 S1 X2 enb EPC E-UTRAN X2 enb X2 EPC = Evolved Packet Core 8

7 EPS Architecture Functional description of the Nodes enb enodeb contains all radio access functions Admission Control Scheduling of UL & DL data Scheduling and transmission of paging and system broadcast IP header compression Outer ARQ (RLC) Inter Cell RRM RB Control Connection Mobility Cont. Radio Admission Control enb Measurement Configuration & Provision Dynamic Resource Allocation (Scheduler) RRC PDCP RLC MAC PHY S1 MME S-GW NAS Security Idle State Mobility Handling EPS Bearer Control Mobility Anchoring P-GW UE IP address allocation Packet Filtering MME control plane functions Idle mode UE reachability Tracking area list management S-GW/P-GW selection Inter core network node signaling for mobility bw. 2G/3G and LTE NAS signaling Authentication Bearer management functions internet E-UTRAN EPC Serving Gateway Local mobility anchor for inter-enb handovers Mobility anchor for inter-3gpp handovers Idle mode DL packet buffering Lawful interception Packet routing and forwarding PDN Gateway UE IP address allocation Mobility anchor between 3GPP and non-3gpp access Connectivity to Packet Data Network 9

8 EPS Architecture Control Plane Layout over S1 NAS sub-layer performs: Authentication Security control Idle mode mobility handling Idle mode paging origination UE enb MME NAS RRC PDCP RLC MAC PDCP sub-layer performs: Integrity protection & ciphering PHY RRC PDCP RLC MAC PHY NAS RRC sub-layer performs: Broadcasting Paging Connection Management Radio bearer control Mobility functions UE measurement reporting & control UE enode-b MME 10

9 EPS Architecture User Plane Layout over S1 Physical sub-layer performs: DL: OFDMA, UL: SC-FDMA FEC UL power control Multi-stream transmission & reception (i.e. MIMO) UE PDCP RLC MAC PHY enb PDCP RLC MAC PHY PDCP sub-layer performs: Header compression Ciphering S-Gateway RLC sub-layer performs: Transferring upper layer PDUs In-sequence delivery of PDUs Error correction through ARQ Duplicate detection Flow control Segmentation/ Concatenation of SDUs MAC sub-layer performs: Scheduling Error correction through HARQ Priority handling across UEs & logical channels Multiplexing/de-multiplexing of RLC radio bearers into/from PhCHs on TrCHs UE enode-b MME 11

10 EPS Architecture Interworking for 3GPP and non-3gpp Access GERAN SGSN HSS non-3gpp Access S3 S6a UTRAN S1-MME MME S10 S11 S12 S4 Gxc PCRF Gx E-UTRAN Serving GW PDN GW Internet S1-U S5 SGi EPS Core Home Subscriber Server (HSS) is the subscription data repository for permanent user data (subscriber profile). Policy Charging Rules Function (PCRF) provides the policy and charging control (PCC) rules for controlling the QoS as well as charging the user, accordingly. S3 interface connects MME directly to SGSN for signaling to support mobility across LTE and UTRAN/GERAN; S4 allows direction of user plane between LTE and GERAN/ UTRAN (uses GTP) 12

11 LTE Key Radio Features (Release 8) Multiple access scheme DL: OFDMA with CP UL: Single Carrier FDMA (SC-FDMA) with CP Adaptive modulation and coding DL modulations: QPSK, 16QAM, and 64QAM UL modulations: QPSK, 16QAM, and 64QAM (optional for UE) Rel-6 Turbo code: Coding rate of 1/3, two 8-state constituent encoders, and a contention-free internal interleaver. ARQ within RLC sublayer and Hybrid ARQ within MAC sublayer. Advanced MIMO spatial multiplexing techniques (2 or 4)x(2 or 4) downlink and 1x(2 or 4) uplink supported. Multi-layer transmission with up to four streams. Multi-user MIMO also supported. Implicit support for interference coordination Support for both FDD and TDD 13

12 LTE Frequency Bands LTE will support all band classes currently specified for UMTS as well as additional bands 14

13 OFDM Basics Overlapping Orthogonal OFDM: Orthogonal Frequency Division Multiplexing OFDMA: Orthogonal Frequency Division Multiple-Access FDM/ FDMA is nothing new: carriers are separated sufficiently in frequency so that there is minimal overlap to prevent cross-talk. conventional FDM frequency OFDM: still FDM but carriers can actually be orthogonal (no cross-talk) while actually overlapping, if specially designed saved bandwidth! OFDM saved bandwidth frequency 15

14 OFDM Basics Waveforms f = 1/T Frequency domain: overlapping sinc functions Referred to as subcarriers Typically quite narrow, e.g. 15 khz x 10 5 freq Time domain: simple gated sinusoid functions For orthogonality: each symbol has an integer number of cycles over the symbol time fundamental frequency f 0 = 1/T T = symbol time Other sinusoids with f k = k f time 16

15 OFDM Basics The Full OFDM Transceiver Modulating the symbols onto subcarriers can be done verry efficiently in baseband using the FFT algorithm OFDM Transmitter bit stream Encoding + Interleaving + Modulation Serial to Parallel... IFFT... Parallel to Serial add CP D/A RF Tx Estimated bit stream Demod + De-interleave + Decode Parallel to Serial... FFT... Serial to Parallel remove CP A/D RF Rx Channel estimation & compensation OFDM Receiver 17

16 OFDM Basics Cyclic Prefix ISI (between OFDM symbols) eliminated almost completely by inserting a guard time T G T G OFDM Symbol OFDM Symbol OFDM Symbol Within an OFDM symbol, the data symbols modulated onto the subcarriers are only orthogonal if there are an integer number of sinusoidal cycles within the receiver window Filling the guard time with a cyclic prefix (CP) ensures orthogonality of subcarriers even in the presence of multipath elimination of same cell interference CP Useful OFDM symbol time OFDM symbol CP Useful OFDM symbol time OFDM symbol CP Useful OFDM symbol time OFDM symbol 18

17 OFDM Basics Choosing the Symbol Time for LTE Two competing factors in determining the right OFDM symbol time: CP length should be longer than worst case multipath delay spread, and the OFDM symbol time should be much larger than CP length to avoid significant overhead from the CP On the other hand, the OFDM symbol time should be much smaller than the shortest expected coherence time of the channel to avoid channel variability within the symbol time LTE is designed to operate in delay spreads up to ~5 μs and for speeds up to 350 km/h (1 ms coherence 2.6 GHz). As such, the following was decided: CP length = 4.7 μs OFDM symbol time = 66.6 μs(~1/15 the worst case coherence time) f = 15 khz ~4.7 µs ~66.7 µs CP 22

18 Scalable OFDM for Different Operating Bandwidths 20 MHz bandwidth 10 MHz bandwidth 5 MHz bandwidth With Scalable OFDM, the subcarrier spacing stays fixed at 15 khz (hence symbol time is fixed to 66.6 µs) regardless of the operating bandwidth (1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz) 3 MHz bandwidth 1.4 MHz bandwidth common channels centre frequency The total number of subcarriers is varied in order to operate in different bandwidths This is done by specifying different FFT sizes (i.e. 512 point FFT for 5 MHz, 2048 point FFT for 20 MHz) Influence of delay spread, Doppler due to user mobility, timing accuracy, etc. remain the same as the system bandwidth is changed robust design 23

19 LTE Downlink Frame Format Radio frame = 10ms subframe = 1.0ms slot = 0.5ms slot = 0.5ms OFDM symbol Subframe length is 1 ms consists of two 0.5 ms slots 7 OFDM symbols per 0.5 ms slot 14 OFDM symbols per 1ms subframe In UL center SC-FDMA symbol used for the data demodulation reference signal (DM-RS) 24

20 Multiple Antenna Techniques Supported in LTE SU-MIMO Multiple data streams sent to the same user (max. 2 codewords) Significant throughput gains for UEs in high SINR conditions MU-MIMO or Beamforming Different data streams sent to different users using the same time-frequency resources Improves throughput even in low SINR conditions (cell-edge) Works even for single antenna mobiles Transmit diversity (TxDiv) Improves reliability on a single data stream Fall back scheme if channel conditions do not allow SM Useful to improve reliability on common control channels 25

21 MIMO Support is Different in Downlink and Uplink Downlink Supports SU-MIMO, MU-MIMO, TxDiv Uplink Initial release of LTE does only support MU-MIMO with a single transmit antenna at the UE Desire to avoid multiple power amplifiers at UE 26

22 LTE Duplexing Modes LTE supports both Frequency Division Duplex (FDD) and Time Division Duplex (TDD) to provide flexible operation in a variety of spectrum allocations around the world. Unlike UMTS TDD there is a high commonality between LTE TDD & LTE FDD Slot length (0.5 ms) and subframe length (1 ms) is the same than LTE FDD with the same numerology (OFDM symbol times, CP length, FFT sizes, sample rates, etc.) UL/ DL switching points designed to allow coexistance with UMTS-TDD (TD-CDMA, TD-SCDMA) 27

23 LTE Half-Duplex FDD In addition to FDD & TDD, LTE supports also Half-Duplex FDD (HD-FDD) HD-FDD is like FDD, only the UE cannot transmit and receive at the same time Note, that the enodeb can still transmit and receive at the same time to different UEs; half-duplex is enforced by the enodeb scheduler Reasons for HD-FDD Handsets are cheaper, as no duplexer is required More commonality between TDD and HD-FDD than compared to full duplex FDD Certain FDD spectrum allocations have small duplex space; HD-FDD leads to duplex desense in UE 28

24 LTE Downlink The LTE downlink uses scalable OFDMA Fixed subcarrier spacing of 15 khz for unicast Symbol time fixed at T = 1/15 khz = µs Different UEs are assigned different sets of subcarriers so that they remain orthogonal to each other (except MU-MIMO) bit stream Encoding + Interleaving + Modulation Serial to Parallel... IFFT... Parallel to Serial add CP 20 MHz: 2048 pt IFFT 10 MHz: 1024 pt IFFT 5 MHz: 512 pt IFFT 29

25 Physical Channels to Support LTE Downlink Allows mobile to get timing and frequency sync with the cell Carries basic system broadcast information Carries DL traffic DL resource allocation enodeb Time span of PDCCH HARQ feedback for DL CQI reporting MIMO reporting 30

26 Mapping between DL Logical, Transport and Physical Channels PCCH: paging control channel BCCH: broadcast control channel CCCH: common control channel DCCH: dedicated control channel DTCH: dedicated traffic channel LTE makes heavy use of shared channels common control, paging, and part of broadcast information carried on PDSCH PCCH BCCH CCCH DCCH DTCH MCCH MTCH Downlink Logical channels PCH: paging channel BCH: broadcast channel DL-SCH: DL shared channel PCH BCH DL-SCH MCH Downlink Transport channels PCFICH PBCH PHICH PDSCH PDCCH PMCH Downlink Physical Channels 31

27 LTE Uplink Transmission Scheme (1/2) To facilitate efficient power amplifier design in the UE, 3GPP chose single carrier frequency domain multiple access (SC-FDMA) in favor of OFDMA for uplink multiple access. SC-FDMA results in better PAPR Reduced PA back-off improved coverage SC-FDMA is still an orthogonal multiple access scheme UEs are orthogonal in frequency UE A Synchronous in the time domain through the use of timing advance (TA) signaling Node B UE C UE B Only need to be synchronous within a fraction of the CP length α UE A Transmit Timing 0.52 µs timing advance resolution β UE B Transmit Timing γ UE C Transmit Timing 32

28 LTE Uplink Transmission Scheme (2/2) SC-FDMA implemented using an OFDMA front-end and a DFT pre-coder, this is referred to as either DFT-pre-coded OFDMA or DFT-spread OFDMA (DFT- SOFDMA) Advantage is that numerology (subcarrier spacing, symbol times, FFT sizes, etc.) can be shared between uplink and downlink Can still allocate variable bandwidth in units of 12 sub-carriers Each modulation symbol sees a wider bandwidth bit stream Encoding + Interleaving + Modulation Serial to Parallel.. DFT.. Subcarrier mapping... IFFT... Parallel to Serial add CP DFT precoding 33

29 Physical Channels to Support LTE Uplink Random access for initial access and UL timing alignment Carries UL Traffic UL scheduling request for time synchronized IEs enodeb Allows channel state information to be obtained by enb UL scheduling grant HARQ feedback for UL 34

30 Mapping between UL Logical, Transport and Physical Channels CCCH: common control channel DCCH: dedicated control channel DTCH: dedicated traffic channel CCCH DCCH DTCH Uplink Logical channels RACH: random access channel UL-SCH: UL shared channel RACH UL-SCH Uplink Transport channels PUSCH: physical UL shared channel PUCCH: physical UL control channel PRACH: physical random access channel PRACH PUSCH PUCCH Uplink Physical Channels 35

31 Downlink Peak Rates bandwidth # of parallel streams supported MHz 5.4 MBps 10.4 MBps 19.6 MBps 3 MHz 13.5 MBps 25.9 MBps 50 MBps 5 MHz 22.5 MBps 43.2 MBps 81.6 MBps 10 MHz 45 MBps 86.4 MBps MBps 15 MHz 67.5 MBps MBps MBps 20 MHz 90 MBps MBps MBps assumptions: 64QAM, code rate = 1, 1OFDM symbol for L1/L2, ignores subframes with P-BCH, SCH 36

32 Uplink Peak Rates bandwidth Highest Modulation 16 QAM 64QAM 1.4 MHz 2.9 MBps 4.3 MBps 3 MHz 6.9 MBps 10.4 MBps 5 MHz 11.5 MBps 17.3 MBps 10 MHz 27.6 MBps 41.5 MBps 15 MHz 41.5 MBps 62.2 MBps 20 MHz 55.3 MBps 82.9 MBps assumptions: code rate = 1, 2PRBs reserved for PUCCH (1 for 1.4MHz), no SRS, ignores subframes with PRACH, takes into account highest prime-factor restriction 37

33 LTE Release 8 User Equipment Categories Category Peak rate Mbps DL UL Capability for physical functionalities RF bandwidth 20MHz Modulation DL QPSK, 16QAM, 64QAM UL QPSK, 16QAM QPSK, 16QAM, 64QAM Multi-antenna 2 Rx diversity Assumed in performance requirements. 2x2 MIMO Not supported Mandatory 4x4 MIMO Not supported Mandatory 39

34 Scheduling and Resource Allocation (1/2) Basic unit of allocation is called a Resource Block (RB) 12 subcarriers in frequency (= 180 khz) 1 timeslot in time (= 0.5 ms, = 7 OFDM symbols) Multiple resource blocks can be allocated to a user in a given subframe 12 sub-carriers (180 khz) The total number of RBs available depends on the operating bandwidth Bandwidth (MHz) Number of available resource blocks

35 Scheduling and Resource Allocation (2/2) LTE uses a scheduled, shared channel on both the uplink (UL-SCH) and the downlink (DL-SCH) Normally, there is no concept of an autonomous transmission; all transmissions in both uplink and downlink must be explicitly scheduled Downlink Scheduling 14 OFDM symbols <=3 OFDM symbols for PDCCH UE A UE B UE C Frequency 12 subcarriers Time Slot = 0.5ms Slot = 0.5ms LTE allows "semi-persistent" (periodical) allocation of resources, e.g. for VoIP 41

36 Uplink Power Control Open-loop power control is the baseline uplink power control method in LTE (compensation for path loss and fading) Open-loop PC is needed to constrain the dynamic range between signals received from different UEs Unlike CDMA, there is no in-cell interference to combat; rather, fading is exploited by rate control Transmit power per PRB TxPSD (dbm) = α PL (db) + P0 nominal(dbm) PL db : pathloss, estimated from DL reference signal P0 nominal (dbm) = Γ nominal (db) + I tot (dbm) Sum of SINR target Γ nominal and total interference I tot sent on BCH Fractional compensation factor α 1 (PUSCH) only a fraction of the path loss is compensated Additionally, (slow) closed loop PC can be used Target SINR on PUSCH is now a function of the UE s path loss: SINR (dbm) = Γ nominal (db) (1 α) PL (db) Target SINR 42

37 Interference Coordination with Flexible Frequency Reuse γ β α γ β β α γ β α Full Transmission Bandwidth F1 F2 F Sector α Sector β Sector γ γ β α γ β β α γ β α Cell edge Reuse > 1 β γ α β β γ α β γ α γ β α γ α γ α γ β α γ α Cell centre Reuse = 1 Scheduler can place restriction on which PRBs can be used in which sectors Achieves frequency reuse > 1 Reduced inter-cell interference leads to improved SINR, especially at cell-edge Reduction in available transmission bandwidth leads to poor overall spectral efficiency Cell edge users with frequency reuse > 1, enb transmits with higher power Improved SINR conditions Cell centre users can use whole frequency band enb transmits with reduced power Less interference to other cells Flexible frequency reuse realized through intelligent scheduling and power allocation 43

38 Random-Access Procedure RACH only used for Random Access Preamble Response/ Data are sent over SCH Non-contention based RA to improve access time, e.g. for HO UE enb UE enb 1 Random Access Preamble 0 RA Preamble assignment Random Access Response 2 Random Access Preamble 1 3 Scheduled Transmission 2 Random Access Response Contention Resolution 4 Contention based RA Non-Contention based RA 44

39 LTE Handover LTE uses UE-assisted network controlled handover UE reports measurements; network decides when handover and to which cell Relies on UE to detect neighbor cells no need to maintain and broadcast neighbor lists Allows "plug-and-play" capability; saves BCH resources For search and measurement of inter-frequency neighboring cells only carrier frequency need to be indicated X2 interface used for handover preparation and forwarding of user data Target enb prepares handover by sending required information to UE transparently through source enb as part of the Handover Request Acknowledge message New configuration information needed from system broadcast Accelerates handover as UE does not need to read BCH on target cell Buffered and new data is transferred from source to target enb until path switch prevents data loss UE uses contention-free random access to accelerate handover 45

40 LTE Handover: Preparation Phase UE Source enb Target enb MME sgw Measurement Control Packet Data UL allocation Measurement Reports HO decision HO Request Packet Data L1/L2 signaling L3 signaling User data DL allocation RRC Connection Reconfig. HO Request Ack SN Status Transfer Admission Control HO decision is made by source enb based on UE measurement report Target enb prepares HO by sending relevant info to UE through source enb as part of HO request ACK command, so that UE does not need to read target cell BCCH 46

41 LTE Handover: Execution Phase UE Source enb Target enb MME sgw Packet Data Detach from old cell, sync with new cell Deliver buffered packets and forward new packets to target enb Synchronisation DL data forwarding via X2 Buffer packets from source enb L1/L2 signaling L3 signaling User data UL allocation and Timing Advance RRC Connection Reconfig. Complete Packet Data UL Packet Data RACH is used here only so target enb can estimate UE timing and provide timing advance for synchronization; RACH timing agreements ensure UE does not need to read target cell P-BCH to obtain SFN (radio frame timing from SS is sufficient to know PRACH locations) 47

42 LTE Handover: Completion Phase UE Source enb Target enb MME sgw DL Packet Data DL data forwarding Packet Data Path switch req User plane update req End Marker Release resources Path switch req ACK Switch DL path User plane update response Flush DL buffer, continue delivering in-transit packets L1/L2 signaling End Marker L3 signaling Release resources User data Packet Data Packet Data 48

43 LTE Handover: Illustration of Interruption Period UEs stops Rx/Tx on the old cell UE Source enb Target enb UL U - plane active Measurement Report HO Command HO Request HO Confirm Handover Preparation Handover Interruption (approx 35 ms) approx 20 ms DL sync + RACH (no contention) + Timing Adv + UL Resource Req and Grant HO Complete Handover Latency (approx 55 ms) ACK U - plane active 49

44 Tracking Area BCCH TAI 2 BCCH TAI 3 BCCH TAI 1 BCCH TAI 2 BCCH TAI 2 BCCH TAI 3 BCCH TAI 1 BCCH TAI 1 BCCH TAI 2 BCCH TAI 3 BCCH TAI 1 BCCH TAI 2 BCCH TAI 2 BCCH TAI 3 BCCH TAI 1 Tracking Area 1 Tracking Area 2 Tracking Area 3 Tracking Area Identifier (TAI) sent over Broadcast Channel BCCH Tracking Areas can be shared by multiple MMEs One UE can be allocated to multiple tracking areas 50

45 EPS Bearer Service Architecture E-UTRAN EPC Internet UE enb S-GW P-GW Peer Entity End-to-end Service EPS Bearer External Bearer E-RAB S5/S8 Bearer Radio Bearer S1 Bearer Radio S1 S5/S8 Gi 51

46 LTE RRC States RRC_IDLE Establish RRC connection Release RRC connection RRC_Connected No RRC connection, no context in enodeb (but EPS bearers are retained) UE controls mobility through cell selection UE specific paging DRX cycle controlled by upper layers UE acquires system information from broadcast channel UE monitors paging channel to detect incoming calls RRC connection and context in enodeb Network controlled mobility Transfer of unicast and broadcast data to and from UE UE monitors control channels associated with the shared data channels UE provides channel quality and feedback information Connected mode DRX can be configured by enodeb according to UE activity level 52

47 EPS Connection Management States ECM_IDLE Signaling connection established Signaling connection released ECM_Connected No signaling connection between UE and core network (no S1-U/ S1-MME) No RRC connection (i.e. RRC_IDLE) UE performs cell selection and tracking area updates (TAU) Signaling connection established between UE and MME, consists of two components RRC connection S1-MME connection UE location is known to accuracy of Cell-ID Mobility via handover procedure 53

48 EPS Mobility Management States EMM_Deregistered Attach Detach EMM_Registered EMM context holds no valid location or routing information for UE UE is not reachable by MME as UE location is not known UE successfully registers with MME with Attach procedure or Tracking Area Update (TAU) UE location known within tracking area MME can page to UE UE always has at least one PDN connection 54

49 LTE Status LTE standard (Rel. 8) is stable Rel. 8 frozen in 2Q2009 Since 2010, LTE has been deployed worldwide Totally new infrastructure First target was often to provide broadband coverage for fixed users Currently, 205 LTE networks in 80 countries are in service (Sep. 2013) * Implemented according to Release 8/9 Mostly FDD, but also some TDD networks Mobile packet data support with fallback to 3G/2G for CS voice service Spectrum allocation in new frequency bands as well as existing 2G/3G bands (refarming) 3GPP continues LTE development Rel. 9: technical enhancements/ E-MBMS Rel. 10/11: LTE-Advanced (cf. next slides) * -> Statistics 55

50 LTE-Advanced The evolution of LTE Corresponding to LTE Release 10 and beyond Motivation of LTE-Advanced IMT-Advanced standardisation process in ITU-R Additional IMT spectrum band identified in WRC07 Further evolution of LTE Release 8 and 9 to meet: Requirements for IMT-Advanced of ITU-R Future operator and end-user requirements ITU 2008 Circular Letter Proposals Evaluation Specification IMT-Advanced recommendation 3GPP Study Item phase Work Item phase 3GPP WS IMT-Advanced First submission Final submission LTE release 10 ( LTE-Advanced ) 56

51 Evolution from IMT-2000 to IMT-Advanced Mobility High IMT IMT-Advanced will encompass the capabilities of previous systems Enhanced IMT New Mobile Access New capabilities of IMT-Advanced Enhancement Enhancement Low New Nomadic / Local Area Wireless Access Peak useful data rate (Mbit/s) Interconnection Nomadic / Local Area Access Systems Digital Broadcast Systems

52 System Performance Requirements Peak data rate 1 Gbps data rate will be achieved by 4-by-4 MIMO and transmission bandwidth wider than approximately 70 MHz Peak spectrum efficiency DL: Rel. 8 LTE satisfies IMT-Advanced requirement UL: Need to double from Release 8 to satisfy IMT-Advanced requirement Rel. 8 LTE LTE-Advanced IMT-Advanced Peak data rate DL 300 Mbps 1 Gbps UL 75 Mbps 500 Mbps 1 Gbps (*) Peak spectrum efficiency [bps/hz] DL UL * 100 Mbps for high mobility and 1 Gbps for low mobility is one of the key features as written in Circular Letter (CL) 58

53 Technical Outline to Achieve LTE-Advanced Requirements Support wider bandwidth Carrier aggregation to achieve wider bandwidth Support of spectrum aggregation Peak data rate, spectrum flexibility Advanced MIMO techniques Extension to up to 8-layer transmission in downlink Introduction of single-user MIMO up to 4-layer transmission in uplink Peak data rate, capacity, cell-edge user throughput Coordinated multipoint transmission and reception (CoMP) CoMP transmission in downlink CoMP reception in uplink Cell-edge user throughput, coverage, deployment flexibility Relaying Type 1 relays create a separate cell and appear as Rel. 8 LTE enb to Rel. 8 LTE UEs Coverage, cost effective deployment Further reduction of delay AS/NAS parallel processing for reduction of C-Plane delay 59

54 Carrier Aggregation Wider bandwidth transmission using carrier aggregation Entire system bandwidth up to, e.g., 100 MHz, comprises multiple basic frequency blocks called component carriers (CCs) Each CC is backward compatible with Rel. 8 LTE Carrier aggregation supports both contiguous and non-contiguous spectrums, and asymmetric bandwidth for FDD System bandwidth, e.g., 100 MHz CC, e.g., 20 MHz UE capabilities Frequency 100-MHz case 40-MHz case 20-MHz case (Rel. 8 LTE) 60

55 Advanced MIMO Techniques Extension up to 8-stream transmission for single-user (SU) MIMO in downlink improve downlink peak spectrum efficiency Higher-order MIMO up to 8 streams Max. 8 streams Enhanced multi-user (MU) MIMO in downlink Specify additional reference signals (RS) CSI feedback Enhanced MU-MIMO Introduction of single-user (SU)-MIMO up to 4-stream transmission in uplink Satisfy IMT requirement for uplink peak spectrum efficiency SU-MIMO up to 4 streams Max. 4 streams 61

56 Coordinated Multipoint Transmission/ Reception (CoMP) Enhanced service provisioning, especially for cell-edge users CoMP transmission schemes in downlink Joint processing (JP) from multiple geographically separated points Coherent combining or dynamic cell selection Joint transmission/dynamic cell selection Coordinated scheduling/beamforming (CS/CB) between cell sites Similar for the uplink Dynamic coordination in uplink scheduling Joint reception at multiple sites Coordinated scheduling/beamforming Receiver signal processing at central enb (e.g., MRC, MMSEC) Multipoint reception 62

57 Relaying Type 1 relay Relay node (RN) creates a separate cell distinct from the donor cell UE receives/transmits control signals for scheduling and HARQ from/to RN RN appears as a Rel. 8 LTE enb to Rel. 8 LTE UEs Deploy cells in the areas where wired backhaul is not available or very expensive Higher node Cell ID #x Cell ID #y UE enb RN 63

58 Heterogenous Networks (HetNet) Network expansion due to varying traffic demand & RF environment Cell-splitting of traditional macro deployments is complex and iterative Indoor coverage and need for site acquisition add to the challenge Future network deployments based on Heterogeneous Networks Deployment of Macro enbs for initial coverage only Addition of Pico, HeNBs and Relays for capacity growth & better user experience Improved in-building coverage and flexible site acquisition with low power base stations Relays provide coverage extension with no incremental backhaul expense eicic is introduced in LTE Rel-10 and further enhanced in Rel-11 Time domain interference management Cell range expansion Interference cancellation receiver in the terminal 64

59 LTE References Literature: H. Holma/ A. Toskala (Ed.): LTE for UMTS - Evolution to LTE-Advanced, 2 nd edition, Wiley 2011 E. Dahlman et al: 4G: LTE/LTE-Advanced for Mobile Broadband, 2 nd edition, Academic Press 2013 S. Sesia et al: LTE, The UMTS Long Term Evolution: From Theory to Practice, Wiley 2011 H. Holma/ A. Toskala (Ed.): LTE Advanced: 3GPP Solution for IMT-Advanced, Wiley 2012 Standards TS 36.xxx series: RAN Aspects TS E-UTRAN; Overall description; Stage 2 TR Feasibility study for evolved Universal Terrestrial Radio Access (UTRA) and Universal Terrestrial Radio Access Network (UTRAN) TR Physical layer aspect for evolved UTRA TR GPP System Architecture Evolution: Report on Technical Options and Conclusions TR Feasibility study for Further Advancements for E-UTRA (LTE- Advanced) TR Further Advancements for E-UTRA - Physical Layer Aspects 65

60 Abbreviations CP DFT DRX ECM EMM enodeb/enb EPC EPS E-UTRAN FDD FDM FFT HD-FDD HO HOM HSS IFFT ISI LTE MIMO MME Cyclic Prefix Discrete Fourier Transformation Discontinuous Reception EPS Connection Management EPS Mobility Management Evolved NodeB Evolved Packet Core Evolved Packet System Evolved UMTS Terrestrial Radio Access Network Frequency-Division Duplex Frequency-Division Multiplexing Fast Fourier Transformation Half-Duplex FDD Handover Higher Order Modulation Home Subscriber Server Inverse FFT Inter-Symbol Interference Long Term Evolution Multiple-Input Multiple-Output Mobility Management Entity OFDM OFDMA PCRF PDN P-GW RA RB RRC SAE SCH S-GW SC-FDMA SON SS SU TDD TA TAI TAU UE Orthogonal Frequency-Division Multiplexing Orthogonal Frequency-Division Multiple-Access Policy & Charging Function Packet Data Network PDN Gateway Random Access Resource Block Radio Resource Control System Architecture Evolution Shared Channel Serving Gateway Single Carrier FDMA Self-Organizing Network Synchronization Signal Single User Time-Division Duplex Timing Advance/ Tracking Area Tracking Area Indicator Tracking Area Update User Equipment MU Multi-User 66