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

Transcription

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

2 3GPP Evolution Background 3G Long-Term Evolution (LTE) is the advancement of UMTS with the following targets: Significant increase of the data rates: mobile broadband Simplification of the network architecture Reduction of the signaling effort esp. for activation/ deactivation Work in 3GPP started in Dec 2004 LTE is not backward compatible to UMTS HSPA. LTE is a packet only network there is no support of circuit switched services (no MSC). LTE started on a clean state everything was up for discussion including the system architecture and the split of functionality between RAN and CN. Since 2010, LTE has been further enhanced LTE-Advanced with increased performance targets Application of new scenarios (MTC) and novel concepts (D2D) 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 < 5 ms user plane (UE to RAN edge) < 100 ms camped to active < 50 ms 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 between 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 S/P-GW ASGW enodeb User plane S/P-GW: Serving/PDN 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 MME Less interfaces, some functions disappeared 4 layers into 2 layers Evolved GGSN integrated P-GW Moved SGSN functionalities to S-GW Evolutions to RRM on an IP distributed network for enhancing mobility management Part of RNC mobility function moved to MME & enodeb 5

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

7 EPS Architecture Functional description of the Nodes enodeb contains all radio access functions Radio Resource Management Scheduling of UL & DL data Scheduling and transmission of paging and system broadcast IP header compression & encryption 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 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 Connectivity to Packet Data Network Mobility anchor between 3GPP and non- 3GPP access UE IP address allocation 7

8 EPS Architecture User Plane Layout over S1 Physical sub-layer performs: Modulation Coding (FEC) UL power control Multi-stream transmission & reception (MIMO) PDCP sub-layer performs: Header compression Ciphering S-Gateway RLC sub-layer performs: Transfer of upper layer PDUs Error correction through ARQ Reordering of RLC data PDUs Duplicate detection Flow control Segmentation/ Concatenation of SDUs MAC sub-layer performs: Mapping of logical channels to transport channels Scheduling Error correction through HARQ Priority handling across UEs & logical channels UE enodeb MME 8

9 EPS Architecture Control Plane Layout over S1 NAS sub-layer performs: Authentication Security control Idle mode mobility handling/ paging origination RRC sub-layer performs: Broadcasting Paging RRC Connection Management Radio bearer control Mobility functions UE measurement reporting & control PDCP sub-layer performs: Integrity protection & ciphering UE enodeb MME 9

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) 10

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 11

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

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 13

14 OFDM Basics Waveforms f = 1/T Frequency domain: overlapping sinc functions Referred to as subcarriers Typically quite narrow, e.g. 15 khz 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 14

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

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 16

17 Comparison with CDMA Principle OFDM: particular modulation symbol is carried over a relatively long symbol time and narrow bandwidth LTE: µs symbol time and 15 khz bandwidth For higher data rates send more symbols by using more sub-carriers increases bandwidth occupancy CDMA: particular modulation symbol is carried over a relatively short symbol time and a wide bandwidth UMTS HSPA: 4.17 µs symbol time and 3.84 Mhz bandwidth To get higher data rates use more spreading codes frequency OFDM frequency symbol 0 symbol 1 symbol 2 symbol 3 CDMA symbol 0 symbol 1 symbol 2 symbol 3 time time 17

18 Comparison with CDMA Time Domain Perspective Short symbol times in CDMA lead to ISI in the presence of multipath CDMA symbols Multipath reflections from one symbol significantly overlap subsequent symbols ISI Long symbol times in OFDM together with CP prevent ISI from multipath CP 1 CP 2 CP CP 1 CP 2 1 CP 2 Little to no overlap in symbols from multipath 18

19 Comparison with CDMA Frequency Domain Perspective Channel Response f = 15 khz 5 MHz Frequency In CDMA each symbol is spread over a large bandwidth, hence it will experience both good and bad parts of the channel response in frequency domain In OFDM each symbol is carried by a subcarrier over a narrow part of the band can avoid send symbols where channel frequency response is poor based on frequency selective channel knowledge frequency selective scheduling gain in OFDM systems 19

20 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 s and for speeds up to 350 km/h (~600 µs coherence 2.6 GHz). As such, the following was decided: CP length = 4.7 s OFDM symbol time = s (~1/10 the worst case coherence time) f = 15 khz ~4.7 µs ~66.7 µs CP 20

21 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 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 21

22 LTE Downlink Frame Format Radio frame = 10 ms subframe = 1.0 ms slot = 0.5 ms slot = 0.5 ms 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) 22

23 Spatial Multiplexing V U H H UV H Rank of the MIMO channel determines the number of independent TX/RX channels offered by MIMO for spatial multiplexing Rank min(#tx, #Rx) To properly adjust the transmission parameters the UE provides feedback about the mobile radio channel situation Channel quality (CQI), pre-coding matrix (PMI) and rank (RI) 23

24 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 MIMO Useful to improve reliability on common control channels 24

25 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 25

26 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 using the same numerology (OFDM symbol times, CP length, FFT sizes, sample rates, etc.) Half-Duplex FDD (HD-FDD) as additional method Like FDD, but UE cannot transmit and receive at the same time Useful e.g. in frequency bands with small duplexing space 26

27 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 27

28 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 28

29 Mapping between DL Logical, Transport and Physical Channels PCCH: paging control channel BCCH: broadcast control channel LTE makes heavy use of shared channels common control, paging, and part of broadcast information carried on PDSCH CCCH: common control channel DCCH: dedicated control channel DTCH: dedicated traffic channel PCH: paging channel BCH: broadcast channel DL-SCH: DL shared channel 29

30 LTE Uplink Transmission Scheme (1/2) To facilitate efficient power amplifier design in the UE, 3GPP chose single carrier frequency division 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 Only needed to be synchronous within a fraction of the CP length Node B UE C UE A Transmit Timing UE B 0.52 s timing advance resolution UE B Transmit Timing UE C Transmit Timing 30

31 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 31

32 Physical Channels to Support LTE Uplink Random access for initial access and UL timing alignment Carries UL Traffic UL scheduling request for time synchronized UEs enodeb Allows channel state information to be obtained by enb UL scheduling grant HARQ feedback for UL 32

33 Mapping between UL Logical, Transport and Physical Channels CCCH: common control channel DCCH: dedicated control channel DTCH: dedicated traffic channel RACH: random access channel UL-SCH: UL shared channel PUSCH: physical UL shared channel PUCCH: physical UL control channel PRACH: physical random access channel 33

34 LTE Supported Data Rates The data rates supported by LTE depend on a number of parameters: bandwidth, modulation scheme, MIMO scheme Downlink peak rates Uplink peak rates 34

35 LTE Release 8 System Parameters Access Scheme UL DFTS-OFDM DL OFDMA Bandwidth Minimum TTI Sub-carrier spacing 1.4, 3, 5, 10, 15, 20 MHz 1 ms 15 khz Cyclic prefix length Short 4.7 µs Long 16.7 µs Modulation Spatial multiplexing QPSK, 16QAM, 64QAM Single layer for UL per UE Up to 4 layers for DL per UE MU-MIMO supported for UL and DL 35

36 LTE Release 8 User Equipment Categories Category Peak rate Mbps DL UL Capability for physical functionalities RF bandwidth 20 MHz 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 36

37 Scheduling and Resource Allocation 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

38 LTE Downlink Scheduling & Resource Allocation Channel dependent scheduling is supported in both time and frequency domain enables two dimensional flexibility CQI feedback can provide both wideband and frequency selective feedback PMI and RI feedback allow for MIMO mode selection Scheduler chooses bandwidth allocation, modulation and coding set (MCS), MIMO mode, and power allocation HARQ operation is asynchronous and adaptive Assigned RBs need not be contiguous for a given user in the downlink 14 OFDM symbols <=3 OFDM symbols for L1/L2 control UE A UE B UE C Frequency 12 subcarriers Time Slot = 0.5 ms Slot = 0.5 ms 38

39 LTE Uplink Scheduling & Resource Allocation Channel dependent scheduling in both time and frequency enabled through the use of the sounding reference signal (SRS) Scheduler selects bandwidth, modulation and coding set (MCS), use of MU-MIMO, and PC parameters HARQ operation is synchronous, and can be adaptive PRBs assigned for a particular UE must be contiguous in the uplink (SC-FDMA) To reduce UE complexity, restriction placed on # of PRBs that can be assigned 14 SC-FDMA symbols (12 for data) UE A UE B UE C Frequency 12 subcarriers Time Slot = 0.5 ms Slot = 0.5 ms 39

40 Uplink Power Control Open-loop power control is the baseline uplink power control method in LTE (compensation for path loss and fading) Constrain the dynamic range between signals received from different UEs Fading is exploited by rate control Target SINR is now a function of the UE s pathloss: SINR (dbm) = SINR nom(db) (1 ) PL (db) PL db : pathloss, estimated from DL reference signal Fractional compensation factor 1 only a fraction of the path loss is compensated Target SINR 40

41 Interference Coordination with Flexible Frequency Reuse Cell edge Reuse > 1 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 41

42 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 1 Random Access Preamble Random Access Response 2 3 Scheduled Transmission Contention Resolution 4 Contention based RA Non-Contention based RA 42

43 LTE Handover LTE uses mobile-assisted & network-controlled handover UE reports measurements using reporting criteria 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 as taken 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 43

44 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 44

45 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 PBCH to obtain SFN (radio frame timing from SS is sufficient to know PRACH locations) 45

46 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 46

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

48 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 48

49 EPS Bearer Service Architecture 49

50 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 50

51 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 51

52 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 52

53 LTE Status 3GPP quickly delivered stable LTE standards 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 Worldwide, 560 LTE networks are in service (Oct. 2017) * Mostly implemented according to Release 8/9, increased deployment of LTE-Advanced Mostly FDD, but also some TDD networks Mobile packet data support with fallback to 3G/2G for CS voice service, starting with VoIP 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 12: LTE-Advanced (cf. next slides) * [Source: 5G Americas/ TeleGeography] 53

54 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: Performance requirements for IMT-Advanced of ITU-R Future operator and end-user requirements Other important requirements LTE-Advanced to be backwards compatible with Release 8 Support for flexible deployment scenarios including downlink/uplink asymmetric bandwidth allocation for FDD and non-contiguous spectrum allocation Increased deployment of indoor enb and HNB in LTE-Advanced Cf. T. Nakamura (RAN chairman): Proposal for Candidate Radio Interface Technologies for IMT-Advanced Based on LTE Release 10 and Beyond LTE-Advanced), ITU-R WP 5D 3rd Workshop on IMT-Advanced, October

55 Evolution from IMT-2000 to IMT-Advanced Mobility High IMT-2000 IMT-Advanced encompass the capabilities of previous systems Enhanced IMT-2000 New Mobile Access New capabilities of IMT-Advanced Enhancement Low New Nomadic / Local Area Wireless Access Peak useful data rate (Mbit/s) Interconnection Nomadic / Local Area Access Systems Digital Broadcast Systems 55

56 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) 56

57 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 57

58 Carrier Aggregation Further increase of the available bandwidth by flexible aggregation of the transmission channels (Carrier) Increase of the available peak data rate More flexible channel allocation For each channel (Component Carrier) there is a separate transmitter/ receiver chain Combination of the data streams (aggregation) in the MAC-Layer MAC HARQ1 HARQ1 HARQ1 HARQ1 PHY1 PHY2 PHY3 PHY4 CC1 CC2 CC3 CC4 Band 1 Band 2 58

59 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 59

60 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 60

61 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 61

62 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 62

63 Machine-to-Machine (M2M) Communication Large variety of M2M applications already in use Stationary applications: metering of consumption data, environment monitoring, telemedicine, telemonitoring Mobile M2M applications: tracking of goods (logistics), autonomous communication between vehicles (Car2X) Communication over cellular systems In parts of the world (nearly) complete coverage Low cost connection to even hardly accessible locations Often in 2G systems, 3G/ 4G upcoming Challenges for cellular M2M communication Occurrence of variable radio conditions Times with bad or no radio link Small data reports but for a high number of M2M devices 3GPP provides various LTE improvements under Machine Type Communication (MTC) enhancements 63

64 Device-to-Device (D2D) Communication D2D enables a direct communication between adjacent devices. Avoid delays from infrastructure Provide high data rate at low tx power Allow reuse of resources Possible operation w/o infrastructure 3GPP implementation Proximity services Communication over sidelink channels enb reserves D2D resources (enb grant) Uplink data C-UE D2D-UE Tx enb grant Sidelink data D2D-UE Rx Principle of Sidelink Communication 64

65 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, 2 nd edition, 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

66 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 MU 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 Multi-User OFDM OFDMA PCRF PDN P-GW RA RB RRC SAE SCH S-GW SC-FDMA SON SS SU TDD TA TAI TAU UE VoIP 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 Voice over Internet Protocol 66