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4 g long term evolution introduction 18-jan-2014

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  • 1. “where LTE will lead, we know not; but we can be sure that it will not be the last development in wireless telegraphy” – Guglielmo Marconi
  • 2. Contents [1] LTE/SAE INTRODUCTION      EVOLUTION OF MOBILE COMMUNICATION NETWORKS 3GPP RELEASES & LTE TERMINOLOGY LTE DRIVERS FREQUENCY BANDS LTE-ADVANCED (LTE-A) [2] EVOLVED PACKET SYSTEM (EPS) ARCHITECTURE & PROTOCOLS     OVERVIEW EPS ARCHITECTURE EPS FUNCTIONALITY LTE PROTOCOL STACK LTE UE STATES AND AREA CONCEPTS [3] LTE AIR INTERFACE    OFDMA/SC-FDMA BASICS LTE FRAME & CHANNEL STRUCTURE LTE DOWNLINK & UPLINK PHYSICAL CHANNEL [4] LTE KEY TECHNOLOGY INTRODUCTION    18-Jan-2014 MULTIPLE INPUT MULTIPLE OUTPUT (MIMO) CSFB (CIRCUIT SWITCHED FALLBACK ) SON (SELF ORGANIZING NETWORKS) Free Print and Non-Commercial Publishing 2
  • 3. [1] LTE/SAE INTRODUCTION 18-Jan-2014 Free Print and Non-Commercial Publishing 3
  • 4. Evolution of Mobile Communication Networks     1st 2nd 3rd 4th Generation or 1G Generation or 2G , 2nd Generation Transitional or 2.5G,2.75G Generation or 3G , 3rd Generation Transitional or 3.5G,3.75G,3.9G Generation or 4G 18-Jan-2014 Free Print and Non-Commercial Publishing 4
  • 5. LTE Parallel Evolution Path to HSPA+ 18-Jan-2014 Free Print and Non-Commercial Publishing 5
  • 6. 3GPP RELEASES & LTE TERMINOLOGY Long Term Evolution (LTE) and System Architecture Evolution (SAE) are specified by the Third Generation Partnership Project (3GPP) in Release 8 specifications. A detailed description of SAE/LTE Specifications are available at the 3GPP website: http://www.3gpp.org/ftp/Specs/archive/ The standard development in 3GPP is grouped into two work items, where LTE targets the radio network evolution and System Architecture Evolution (SAE) targets the evolution of the packet core network.  Long Term Evolution (LTE) : Evolution of 3GPP UMTS Terrestrail Radion Access (E-UTRA) Technology. Evolved Packet System (EPS) : Evolution of the complete 3GPP UMTS Radio Access, Packet Core and its integration into legacy 3GPP/non-3GPP network. EPS includes:  Evolved UTRAN (eUTRAN) ” Radio Access Network  Evolved Packet Core (EPC) ” System Architecture. 18-Jan-2014 Free Print and Non-Commercial Publishing 6
  • 7. E-UTRA Design Performance Targets Scalable transmission bandwidth(up to 20 MHz) Improved Spectrum Efficiency Downlink (DL) spectrum efficiency should be 2-4 times Release 6 HSDPA. ”Downlink target assumes 2x2 MIMO for E-UTRA and single Txantenna with Type 1 receiver HSDPA. Uplink (UL) spectrum efficiency should be 2-3 times Release 6 HSUPA. ”Uplink target assumes 1 Tx antenna and 2 Rx antennas for both E-UTRA and Release 6 HSUPA. Coverage Good performance up to 5 km Slight degradation from 5 km to 30 km (up to 100 km not precluded) Mobility Optimized for low mobile speed (< 15 km/h) Maintained mobility support up to 350 km/h (possibly up to 500 km/h) Advanced transmission schemes, multiple-antenna technologies Inter-working with existing 3G and non-3GPP systems Interruption time of real-time or non-real-time service handover between E-UTRAN and UTRAN/GERAN shall be less than 300 or 500 ms. 18-Jan-2014 Free Print and Non-Commercial Publishing 7
  • 8. E-UTRA Air Interface Capabilities UE e-NB Communication Link E-UTRA Air Interface Capabilities Bandwidth support Flexible from 1.4 MHz to 20 MHz Waveform OFDM in Downlink SC-FDM in Uplink Duplexingmode FDD: full-duplex (FD) and half-duplex (HD) TDD Modulation orders for data channels Downlink: QPSK, 16-QAM, 64-QAM Uplink: QPSK, 16-QAM, 64-QAM MIMO support Downlink: SU-MIMO and MU-MIMO (SDMA) Uplink: SDMA 18-Jan-2014 Single & same link of communication for DL & UL DL serving cell = UL serving cell No UL or DL macro-diversity ”UE’s Active Set size = 1  Hard-HO based mobility ”UE assisted (based on measurement reports) and network controlled (handover decision at specific time) by default. ”During a handover, UE uses a RACH based mobility procedure to access the target cell ”Handover is UE initiated if it detects a RL failure condition. Load indicator for inter-cell load control (interference management) ”Transmitted over X2 interface Free Print and Non-Commercial Publishing 8
  • 9. LTE DRIVERS Branding  For branding image  For competition Marketing  For better data service  For SME & Industry user Technical For frequency issue For network quality 18-Jan-2014 Free Print and Non-Commercial Publishing 9
  • 10. LTE DRIVERS Ericsson Mobility Report – November 2013 18-Jan-2014 Free Print and Non-Commercial Publishing 10
  • 11. LTE DRIVERS 18-Jan-2014 Free Print and Non-Commercial Publishing 11
  • 12. LTE DRIVERS LTE operation benefits Enhanced experience for E2E quality Spectrum flexibility Lower cost LTE/SAE introduces the mechanism to fullfill the requirement of a next generation of mobile network.  Higher speed (x10)  Lower latency (1/4 )  Lager capacity (x3)  New or re-farmed spectrum  Varity channel bandwidth  IP based flat network architecture  Low OPEX: SON  High re-use of asset 18-Jan-2014 Flat Overall Architecture  2-nodes architechture  IP routable transport architechture  Lower cost. Improved Radio Aspects  Peak data rates [Mbps] DL=300,UL=75  Scalable Bandwidth:1.4,3,5,10,15,20 MHz  Short latency: <100ms (control plane), <5ms (user plane) New Core Architechture  Simplified Protocol Stack  Simple , more efficient QoS  UMTS backward compatibility security  Circuit Switch service is implemented in PS domain :VoIP. Free Print and Non-Commercial Publishing 12
  • 13. Achievable & Supported Peak Data Rates Achievable LTE Peak Data Rate Peak Data rate scale with the bandwidth 2x2 MIMO supported for the initial LTE deployment. UE Supported Peak Data Rate (Mbps)  Similar peak data rates defined for FDD & TDD.  All categories support 20 MHz, 64QAM downlink and receive antenna diversity.  Category 2,3 ,4 expected in the first phase with bit rates up to 150 Mbps. 18-Jan-2014 Free Print and Non-Commercial Publishing 13
  • 14. Frequency Band of LTE FDD Frequency Band From LTE Protocol:  Duplex mode: FDD and TDD Uplink ( UL) E-UTRA B a nd  Support frequency band form 700MHz to 2.6GHz F U L_low ” Dow nlink ( DL) F U L_high F D L_low ” Duplex M ode F D L_high F U L_low ” F U L_high F D L_low ” F D L_high 2170 MHz FDD 1850 MHz ” 1910 MHz 1930 MHz ” 1990 MHz FDD 1710 MHz ” 1785 MHz 1805 MHz ” 1880 MHz FDD 4 Duplex Mode ” 1710 MHz ” 1755 MHz 2110 MHz ” 2155 MHz FDD 824 MHz ” 849 MHz 869 MHz ” 894MHz FDD 830 MHz ” 840 MHz 875 MHz ” 885 MHz FDD 7 Dow nlink ( DL) 2110 MHz 6 Uplink ( UL) 1980 MHz 5 E-UTRA B and ” 3 TDD Frequency Band 1920 MHz 2  Support various bandwidth: 1.4MHz, 3MHz, 5MHz, 10MHz, 15MHz, 20MHz. 1 2500 MHz ” 2570 MHz 2620 MHz ” 2690 MHz FDD 8 880 MHz ” 915 MHz 925 MHz ” 960 MHz FDD 9 1749.9 MHz 1784.9 MHz 1844.9 MHz 10 1710 MHz ” 1770 MHz 2110 MHz ” 2170 MHz FDD 1427.9 MHz ” 1452.9 MHz 1475.9 MHz ” 1500.9 MHz FDD ” ” FDD 1879.9 MHz 33 1900 MHz ” 1920 MHz 1900 MHz ” 1920 MHz TDD 34 2010 MHz ” 2025 MHz 2010 MHz ” 2025 MHz TDD 35 1850 MHz ” 1910 MHz 1850 MHz ” 1910 MHz TDD 36 1930 MHz ” 1990 MHz 1930 MHz ” 1990 MHz TDD 12 698 MHz ” 716 MHz 728 MHz ” 746 MHz FDD 37 1910 MHz ” 1930 MHz 1910 MHz ” 1930 MHz TDD 13 777 MHz ” 787 MHz 746 MHz ” 756 MHz FDD 38 2570 MHz ” 2620 MHz 2570 MHz ” 2620 MHz TDD 14 788 MHz ” 798 MHz 758 MHz ” 768 MHz FDD 39 1880 MHz ” 1920 MHz 1880 MHz ” 1920 MHz TDD … … 40 2300 MHz ” 2400 MHz 2300 MHz ” 2400 MHz TDD 17 704 MHz ... … 18-Jan-2014 11 … ” Free Print and Non-Commercial Publishing 716 MHz 734 MHz … ” 746 MHz FDD … … 14
  • 15. Frequency Band of LTE ” Release 8 18-Jan-2014 Free Print and Non-Commercial Publishing 15
  • 16. FREQUENCY BANDS 18-Jan-2014 Free Print and Non-Commercial Publishing 16
  • 17. EARFCN (E-Absolute Radio Frequency Channel Numnber) FDL = FDL_low + 0.1(NDL - NOffs-DL) eNB FUL = FUL_low + 0.1(NUL - NOffs-UL) UE 100kHz Raster Uplink Downlink 1937.4MHz 2127.4MHz Frequency FDL = FDL_low + 0.1(NDL - NOffs-DL) NDL = NDL = 18-Jan-2014 (FDL - FDL_low) 0.1 + NOffs-DL (2127.4 - 2110) +0 0.1 = 174 Free Print and Non-Commercial Publishing 17
  • 18. LTE EVOLUTION (LTE-Advanced) LTE-Advanced (LTE-A) is introduced in 3GPP release10 and it’s the Global 4G solution.  Improves spectrum efficiency, delivers increases in capacity and coverage, and the ability to support more customers /devices more efficiently, to maintain and improve the user experience of mobile broadband. [Key features] Multicarrier Enables Flexible Spectrum Deployments  Carrier Aggregation  Higher order MIMO  SON/Hetnets  Interference management  Relays Increased data rates and lower latencies for all users in the cell. Data rates scale with bandwidth„Up to 1 Gbps peak data rate. Aggregating 40 MHz to 100 MHz provide peak data rates of 300 Mbps to 750 Mbps1(2x2 MIMO) and over 1 Gbps(4x4 MIMO) 18-Jan-2014 Free Print and Non-Commercial Publishing 18
  • 19. LTE EVOLUTION (LTE-A) LTE-A introduces higher order MIMO 8x8 DL MIMO, 4x4 UL MIMO and UL Beamforming More Antennas to Leverage Diversity 18-Jan-2014 Free Print and Non-Commercial Publishing 19
  • 20. [2] EVOLVED PACKET SYSTEM (EPS) ARCHITECTURE & PROTOCOLS 18-Jan-2014 Free Print and Non-Commercial Publishing 20
  • 21. System Architecture Evolution (SAE) EPS is all PS (IP based ” no CS domain ) [Main drivers]  All-IP based  Reduce network cost  Reduce data latency & signalling load  Better network topology scalability & reliability  Inter-working & seamless mobility among heterogeneous access networks(3GPP & non3GPP).  Better always-on user experience Simpler and more flexible Qos Suppport  Higher level of security 18-Jan-2014 Free Print and Non-Commercial Publishing 21
  • 22. PS Domain Architecture Evolution EPS flat architecture, with User Plane direct tunneling between SAE-GW and eNode B is similar to the ‚super‛ flat architecture option for HSPA+, where GGSN connects directly to a collapsed RNC+Node B entity or to an evolved Node B. As the color legend shows, the location of the migrated network functions in EPS are as follows:  RNC functions are in eNB & MME  SGSN functions are in the MME  GGSN functions are in SGW & PGW 18-Jan-2014 Free Print and Non-Commercial Publishing 22
  • 23. Overall EPS Architecture Main Network Element of EPS (Evolved Packet System)  E-UTRAN (Evolved UTRAN ) consists of e-NodeBs, providing the user plane and control plane.  EPC (Evolved Packet Core ) consists of MME, S-GW and P-GW. Network Interface of EPC (Evolved Packet System)  e-NodeBs are interconnected with each other by means of the X2 interface, enabling direct transmission of data and signaling.  S1 is the interface between e-NodeBs and the EPC, to the MME via the S1-MME and to S-GW via the S1-U. EPC includes; MME (Mobility Management Entity) handling Control Plane. S-GW (Serving Gateway) & P-GW (PDN Gateway) handling User Plane Note: HSS (Home Subscriber Server) is ‚formally‛ out of the EPC, and will need to be updated with new EPS subscription data and functions. PCRF and Gx/Rx provide QoS Policy and Charging control (PCC), similarly to the UMTS PS domain. 18-Jan-2014 Free Print and Non-Commercial Publishing 23
  • 24. E-UTRAN Entities/Interfaces Evolved Node B (eNB) provides the E-UTRA User Plane (PDCP/RLC/MAC/PHY) and Control Plane (RRC) protocol terminations toward the UE. An eNB can support FDD mode, TDD mode, or dual mode operation. eNBs can optionally be interconnected with each other by means of the X2 interface or connected by means of the S1 interface to the Evolved Packet Core (EPC). e-Node hosts the following functions:  Radio Resource Management: Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both uplink and downlink (scheduling)  IP header compression  Encryption /Integrity protection of user data  MME selection (among MME pool)  Routing of User Plane data towards S-GW  Scheduling and transmission of paging and broadcast messages (originated from the MME)  Measurement and measurement reporting configuration for mobility and scheduling S1 interface  Can be split S1-U (S-GW) & S1-C(MME). X2 interface  Used for inter-eNB handover, load balacing and interference cancellation. 18-Jan-2014 Free Print and Non-Commercial Publishing 24
  • 25. EPC Entities/Interfaces MME (Mobility Management Entity) main functions:       NAS signaling and security AS Security control Idle state mobility handling P-GW and S-GW selection EPS (Evolved Packet System) bearer control; Support paging, handover, roaming and authentication S-GW (Serving Gateway) main functions:      Packet routing and forwarding E-UTRAN and inter-3GPP mobility anchoring E-UTRAN Idle mode DL packet buffering UL and DL charging per UE, PDN, and QCI Transport level QoS mapping P-GW (PDN Gateway) main functions:     Per-user based packet filtering UE IP address allocation UL and DL service level charging User Plane anchoring for 3GPP and non-3GPP mobility S5 interface  Between S-GW and P-GW  Called S8 for Inter-PLMN connection (roaming) 18-Jan-2014 S10 interface  Support mobility between MMEs S11 interface  Support EPS Bearer management between MME & S-GW S6a interface  Used for subscription & security control between MME&HSS Free Print and Non-Commercial Publishing 25
  • 26. LTE Radio Protocol Stack Two Planes in LTE Radio Protocol: (1) User-plane: For user data transfer (2) Control-plane: For system signaling transfer Over LTE-Uu radio interface, protocols are split in:  (AS) Access Stratum: RRC/PDCP/RLC/MAC/PHY.  (NAS) Non Access Stratum: EMM (Mobility Management) and ESM (Session Management) Control plane Main Functions of Control-plane:  RLC and MAC layers perform the same functions as for the user plane  PDCP layer performs ciphering and integrity protection  RRC layer performs broadcast, paging, connection management, RB control, mobility functions, UE measurement reporting and control  NAS layer performs EPS bearer management, authentication, security control Over S1 and X2 interfaces, two RNL application protocols (S1-AP and X2AP), using a new transport protocol called SCTP (Stream Control Transmission Protocol). S1-AP: Supports all necessary EMM-eNB signaling and procedures, including RAB management, mobility, paging, NAS transport, and many other S1 related functions. X2-AP: Supports Intra LTE-Access-System Mobility, Uplink Load Management, and X2 error handling functions. 18-Jan-2014 Free Print and Non-Commercial Publishing 26
  • 27. LTE Radio Protocol Stack User-plane User plane on the S1-U uses GTP-U for tunneling. The same protocol stack would apply to the X2 interface, for data packet forwarding during handover between eNBs. The concatenation of LTE RB + S1 Bearer + S5 Bearer makes the EPS Bearer, which can be shared by multiple Service Flows with the same level of QoS. EPS Bearer (similar to a PDP context of previous 3GPP releases) is defined between the User Equipment (UE) and the P-GW node in the EPC (which provide the end users IP point of presence towards external networks). 18-Jan-2014 Free Print and Non-Commercial Publishing 27
  • 28. LTE Radio Interface structure The radio interface is structured in a layered model, similar to WCDMA, with a layer 2 bearer (here called EPS Bearer Service), which corresponds to a PDP-context in Rel. 6, carrying layer 3 data and the end-to-end service. The EPS bearer is carried by the E-UTRA Radio Bearer Service in the radio interface. The E-UTRA radio bearer is carried by the radio channels. The radio channel structure is divided into logical, transport and physical channels. 18-Jan-2014 Free Print and Non-Commercial Publishing 28
  • 29. LTE UE STATES AND AREA CONCEPTS LTE is developed to have a simpler architecture (fewer nodes) and less signaling (fewer messages) than the UTRAN. The number of states which the UE can be in (corresponding to RRC states) are reduced from five in the UTRAN (DETACHED, IDLE, URA_PCH, CELL_FACH, CELL_DCH) to only three in the eUTRAN (DETACHED, IDLE and CONNECTED) In LTE only one area for idle mode mobility is defined; the Tracking Area (TA). In UTRAN, Routing Area (RA) and UTRAN Registration Area (URA) is defined for PS traffic and Location Area (LA) for CS traffic. In ECM-IDLE (EPS Connection Management IDLE) the UE position is only known by the network on TA level, whereas in ECM-CONNECTED, the UE location is known on cell level by the eNodeB. 18-Jan-2014 Free Print and Non-Commercial Publishing 29
  • 30. [3] LTE AIR INTERFACE 18-Jan-2014 Free Print and Non-Commercial Publishing 30
  • 31. Duplex Techology  Frequency Division Duplex (FDD): Distinguish uplink and downlink according to frequencies.  Time division duplex (TDD): Distinguish uplink and downlink according to timeslots. 18-Jan-2014 Free Print and Non-Commercial Publishing 31
  • 32. Multiple Access Technology 18-Jan-2014 Free Print and Non-Commercial Publishing 32
  • 33. OFDM Basics LTE radio interface is based on OFDM (Orthogonal Frequency Division Multiplex) and OFDMA (Orthogonal Frequency Division Multiple Access) in DL and SC-FDMA (Single Carrier Frequency Division Multiple Access) in UL. OFDM uses a large number of closely spaced narrowband carriers.In a conventional FDM system, the frequency spacing between carriers is chosen with a sufficient guard band to ensure that interference is minimized and can be cost effectively filtered. In OFDM, however, the carriers are packed much closer together. OFDM Orthogonality Each of the 15 kHz LTE air interface subcarriers are ‘Orthogonal’ to each other , there is zero inter-carrier interference at the center frequency of each subcarrier. Orthogonality allows simultaneous transmission on many subcarriers in a tight frequency space without interference from each other. The spectrums of the subcarriers are not separated, but overlap. 18-Jan-2014 Free Print and Non-Commercial Publishing 33
  • 34. OFDM Basics The transmitter combines all the subcarriers using an Inverse Fast Furrier Transform (IFFT) function where the outcome is single signal which is basically a sum of sinusoids having an amplitude that varies depending on the number of subcarriers. The receiver uses a Fast Fourier Transform (FFT) function to recover each subcarrier. System Bandwidth FFT Sub-carriers Guard … Intervals Symbols Frequency … Time OFDM also shows very good performance in highly time dispersive radio environments (i.e. many delayed and strong multipath reflections). FFT = Fast Fourier Transform, IFFT = Inverse FFT FFT/IFFT allows to move between time and frequency domain representation 18-Jan-2014 That is because the data stream is distributed over many subcarriers. Each subcarrier will thus have a slow symbol rate and correspondingly, a long symbol time. This means that the Inter Symbol Interference (ISI) is reduced. Free Print and Non-Commercial Publishing 34
  • 35. OFDM & SC-FDMA OFDM & OFDMA DFT-S-OFDM & SC-FDMA  OFDM (Orthogonal Frequency Division Multiplexing) is a modulation multiplexing technology, divides the system bandwidth into orthogonal subcarriers.  OFDMA is the multi-access technology related with OFDM, is used in the LTE downlink. OFDMA is the combination of TDMA and FDMA essentially.  Advantage: High spectrum utilization efficiency due to orthogonal subcarriers need no protect bandwidth. Support frequency link auto adaptation and scheduling. Easy to combine with MIMO.  DFT-S-OFDM (Discrete Fourier Transform Spread OFDM) is the modulation multiplexing technology used in the LTE uplink, Each user is assigned part of the system bandwidth.  SC-FDMA(Single Carrier Frequency Division Multiple Accessing)is the multi-access technology related with DFT-S-OFDM.  Advantage: High spectrum utilization efficiency due to orthogonal user bandwidth need no protect bandwidth.  Disadvantage: Strict requirement of time-frequency domain synchronization. High Peak-to-Average Power Ratio (PAPR).  Low Peak-to-Average Power Ratio (PAPR) System Bandwidth System Bandwidth Sub-carriers Sub-carriers TTI: 1ms Frequency TTI: 1ms Frequency User 1 User 2 User 3 Time User 1 User 2 Time 18-Jan-2014 Sub-band:12Sub-carriers Sub-band:12Sub-carriers SC-FDMA : PRB’s are grouped to bring down PAPR , better power efficiency at the UE User 3 Free Print and Non-Commercial Publishing 35
  • 36. Time & Frequency Domain Organization LTE Time Domain is organized as  Frame (10 ms)  Sub-frame (1ms)  Slot (0.5ms)  Symbol (duration depends on configuration) Radio Frame Structures Supported by LTE:  Type 1, applicable to FDD  Type 2, applicable to TDD LTE Frequency Domain  LTE DL/UL air interface waveforms use a number of Orthogonal subcarriers to send users & control data. Pre-defined spacing between these subcarriers (15 KHz for regular operation and 7.5 KHZ for MBSFN operation) . DC subcarrier which has no energy and is located at the center of the frequency band. Two guard bands at the edges of the OFDM/OFDMAsignal (no RF transmission in this subcarriers). This is a guard band to avoid interference with adjacent bands. 18-Jan-2014 Free Print and Non-Commercial Publishing 36
  • 37. Frequency Domain Configurations  Various channel bandwidths that may be considered for LTE deployment are shown in the table.  One of the typical LTE deployment options (10 MHz) is highlighted. Assuming 15 KHz Carrier Spacing 18-Jan-2014 Free Print and Non-Commercial Publishing 37
  • 38. UL/DL Resource Grid Definitions  Resource Element (RE) One element in the time/frequency resource grid. One subcarrier in one OFDM/LFDM symbol for DL/UL. Often used for Control channel resource assignment.  Resource Block (RB) Minimum scheduling size for DL/UL data channels Physical Resource Block (PRB) [180 kHz x 0.5 ms] Virtual Resource Block (VRB) [180 kHz x 0.5 ms in virtual frequency domain] ” Localized VRB ” Distributed VRB  Resource Block Group (RBG) Group of Resource Blocks Size of RBG depends 18-Jan-2014 Free Print and Non-Commercial Publishing 38
  • 39. UL/DL Resource Grid Definitions  Resource Element Group (REG)  Groups of Resource Elements to carry control information.  4 or 6 REs per REG depending on number of reference signals per symbol, cyclic prefix configuration.  REs used for DL Reference Signals (RS) are not considered for the REG. ” Only 4 usable REs per REG. Control Channel Element (CCE) Group of 9 REGs form a single CCE. ” 1 CCE = 36 REs usable for control information.  Both REG and CCE are used to specify resources for LTE DL control channels. Antenna Port One designated reference signal per antenna port. Set of antenna ports supported depends on reference signal configuration within cell. 18-Jan-2014 Free Print and Non-Commercial Publishing 39
  • 40. TDD Radio Frame Structure  Applies OFDM, same subcarriers spacing and time unit with FDD. Uplink-downlink Configurations  Similar frame structure with FDD. radio frame is 10ms shown as below, divided into 20 slots which are 0.5ms. Uplinkdownlink configuration Downlink-to-Uplink Switch-point periodicity The uplink-downlink configuration of 10ms frame are shown in the right table. 0  Subframe number 1 2 3 4 5 6 7 8 9 5 ms D S U U U D S U U U 1 Special Subrame Structure  Special Subframe consists of DwPTS, GP and UpPTS .  9 types of Special subframe configuration.  Guard Period size determines the maximal cell radius. (100km)  DwPTS consists of at least 3 OFDM symbols, carrying RS, control message and data.  UpPTS consists of at least 1 OFDM symbol, carrying sounding RS or short RACH. 0 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D D D D 6 5 ms D S U U U D S U U D  DL to UL switch point in special subframe #1 and #6 only  Other subframes allocated to UL or DL  Sum of DwPTS, GP and UpPTS always 1 ms  Subframe #0 and #5 always DL - Used for cell search signals (S-SCH) 18-Jan-2014 Free Print and Non-Commercial Publishing 40
  • 41. Cyclic Prefix (CP) Transmission  CP Length Configuration:  Cyclic Prefix is applied to eliminate ISI (Inter-symbol Interference) of OFDM.  CP length is related with coverage radius. Normal CP can fulfill the requirement of common scenarios. Extended CP is for wide coverage scenario.  Longer CP, higher overheading. Slot structure under Normal CP configuration (△f=15kHz) Slot structure under Extended CP configuration (△f=15kHz) Slot structure under Extended CP configuration (△f=7.5kHz) Configuration DL OFDM CP Length UL SC-FDMA CP Length Extended CP 18-Jan-2014 160 for slot #0 160 for slot #0 144 for slot #1~#6 144 for slot #1~#6 f=15kHz 512 for slot #0~#5 512 for slot #0~#5 f=7.5kHz Normal CP 1024 for slot #0~#2 NULL Sub-carrier of each RB f=15kHz Symbol of each slot 7 12 6 24 (DL only) Free Print and Non-Commercial Publishing 3 (DL only) 41
  • 42. Cyclic Prefix (CP) Transmission In OFDM, multipath causes loss of orthogonality Delayed paths cause overlap between symbols Cyclic Prefix (CP) insertion helps maintain orthogonality Reduces efficiency (or Usable Symbol time, Tu) .  Mitigates Inter-Symbol Interference (ISI)  Reduces efficiency ” Useable time per symbol is Tu/(Tu+TCP)  Selection of Cyclic Prefix governed by delay spread 18-Jan-2014 Free Print and Non-Commercial Publishing 42
  • 43. LTE Channel Structure 18-Jan-2014 Free Print and Non-Commercial Publishing 43
  • 44. LTE Channel Structure Transport Channel Logical Channel Control Channel DL Channel  Broadcast Control Channel (BCCH) ” DL broadcast of system control information.  Paging Control Channel (PCCH) ” DL paging information. UE position not known on cell level  Common Control Channel (CCCH) ” UL/DL. When no RRC connection exists.  Multicast Control Channel (MCCH) ” DL point-to-multipoint for MBMS scheduling and control, for one or several MTCHs.  Dedicated Control Channel (DCCH) ” UL/DL dedicated control information. Used by UEs having an RRC connection.  Broadcast Channel (BCH) – System Information broadcasted in the entire coverage area of the cell.Beamforming is not applied.  Downlink Shared Channel (DL-SCH) – User data, control signaling and System Info. HARQ and link adaptation.Broadcast in the entire cell or beamforming. DRX and MBMS supported.  Paging Channel (PCH) – Paging Info broadcasted in the entire cell. DRX  Multicast Channel (MCH) – MBMS traffic broadcasted in entire cell. MBSFN is supported. Traffic Channel  Dedicated Traffic Channel (DTCH) – UL/DL Dedicated Traffic to one UE, user information.  Multicast Traffic Channel (MTCH) – DL point-to-multipoint. MBMS user data.  Uplink Shared channel (UL-SCH) – User data and control signaling. HARQ and link adaptation. Beamforming may be applied.  Random Access Channel (RACH) – Random Access transmissions (asynchronous and synchronous). The transmission is typically contention based. For UEs having an RRC connection there is some limited support for contention free access. 18-Jan-2014 UL Channel Free Print and Non-Commercial Publishing 44
  • 45. LTE Channel Structure Physical channels  Physical Downlink Shared Channel (PDSCH) ” transmission of the DL-SCH transport channel  Physical Uplink Shared Channel (PUSCH) ” transmission of the UL-SCH transport channel  Physical Control Format Indicator Channel (PCFICH) ” indicates the PDCCH format in DL  Physical Downlink Control Channel (PDCCH) ” DL L1/L2 control signaling  Physical Uplink Control Channel (PUCCH) ” UL L1/L2 control signaling  Physical Hybrid ARQ Indicator Channel (PHICH) Physical signals  Reference Signals (RS) – support measurements and coherent demodulation in uplink and downlink. Primary and Secondary Synchronization signals (P-SCH and S-SCH) – DL only and used in the cell search procedure. Sounding Reference Signal (SRS) – supports UL scheduling measurements ” DL HARQ info  Physical Broadcast Channel (PBCH) ” DL transmission of the BCH transport channel.  Physical Multicast Channel (PMCH) ” DL transmission of the MCH transport channel. Physical Random Access Channel (PRACH) ” UL transmission of the random access preamble as given by the RACH transport channel. 18-Jan-2014 Free Print and Non-Commercial Publishing 45
  • 46. Synchronization Signals (PSS & SSS)  PSS and SSS Functions ”Frequency and Time synchronization  Carrier frequency determination  OFDM symbol/subframe/frame timing determination ”Physical Layer Cell ID (PCI) determination  Determine 1 out of 504 possibilities PSS and SSS resource allocation ”Time: subframe0 and 5 of everyFrame ”Frequency: middle of bandwidth (6 RBs = 1.08 MHz) Primary Synchronization Signals (PSS) ”Assists subframe timing determination ”Provides a unique Cell ID index (0, 1, or 2) withina Cell ID group Secondary Synchronization Signals (SSS) ”Assists frame timing determination ”Provides a unique Cell ID group number among 168 possible Cell ID groups 18-Jan-2014 Free Print and Non-Commercial Publishing 46
  • 47. Cell Identity Determination from PSS and SSS Physical Cell Identity (PCI) is uniquely defined by: A number in the range of 0 to 167, representing the Physical Cell Identity (PCI) group A number in the range of 0 to 2, representing the physical identity within the Physical Cell Identity (PCI) group S-SCH Provides 168 sequences, each associated to a cell ID group information These sequences are interleaved concatenations of two length31 binary sequences P-SCH Three (NID=0,1,2) frequency domain Zadoff-Chu sequences of length 62 18-Jan-2014 Free Print and Non-Commercial Publishing 47
  • 48. Physical Broadcast Channel (PBCH) PBCH Function ”Carries the primary Broadcast Transport Channel ”Carries the Master Information Block (MIB), which includes:  Overall DL transmission bandwidth  PHICH configuration in the cell  System Frame Number  Number of transmit antennas (implicit) Transmitted in ” Time: subframe 0 in every frame ” 4 OFDM symbols in the second slot of corresponding subframe ” Frequency: middle 1.08 MHz (6 RBs) TTI = 40 ms ” Transmitted in 4 bursts at a very low data rate ” Same information is repeated in 4 subframes ” Every 10 ms burst is self-decodable ” CRC check uniquely determines the 40 ms PBCH TTI boundary Last 2 bits of SFN is not transmitted 18-Jan-2014 Free Print and Non-Commercial Publishing 48
  • 49. System Information in PBCH & PDSCH The System Information (SI) that is broadcasted in the whole cell area, is carried by the logical channel BCCH, which in turn is carried by either of the transport channels BCH or DL-SCH. A static part of SI is called MIB (Master Information Block) is transmitted on the BCH, which in turn is carried by the PBCH. A dynamic part of SI, called SIBs (System Information Blocks) is mapped onto RRC System Information messages (SI-1,2,3…) on DL-SCH, which in turn is carried by PDSCH. 18-Jan-2014 Free Print and Non-Commercial Publishing 49
  • 50. System Information (MIB & SIB) MIB (Master Information Block) Repeats every 4 frames (40 ms) and includes DL Tx bandwidth, PHICH configuration, and SFN. This information is necessary to acquire (read) other channels in the cell. ***( LTERelease 8 has 11 different SIB types) 18-Jan-2014 Free Print and Non-Commercial Publishing 50
  • 51. Physical Control Format Indicator Channel (PCFICH) Carries the Control Format Indicator (CFI) Signals the number of OFDM symbols of PDCCH: ” 1, 2, or 3 OFDM symbols for system bandwidth > 10 RBs ” 2, 3, or 4 OFDM symbols for system bandwidth > 6-10 RBs ” Control and data do not occur in same OFDM symbol Transmitted in: ” Time: 1st OFDM symbol of all subframes ” Frequency: spanning the entire system band  4 REGs -> 16 REs  Mapping depends on Cell ID PCFICH in Multiple Antenna configuration ” 1 Tx: PCFICH is transmitted as is ” 2Tx, 4Tx: PCFICH transmission uses Alamouti Code 18-Jan-2014 Free Print and Non-Commercial Publishing 51
  • 52. Physical Downlink Control Channel (PDCCH) Used for: ” DL/UL resource assignments ” Multi-user Transmit Power Control (TPC) commands ” Paging indicators CCEs are the building blocks for transmitting PDCCH ” 1 CCE = 9 REGs (36 REs) = 72 bits ” The control region consists of a set of CCEs, numbered from 0 to N_CCE for each subframe ” The control region is confined to 3 or 4 (maximum) OFDM symbols per subframe (depending on system bandwidth) A PDCCH is an aggregation of contiguous CCEs (1,2,4,8) ” Necessary for different PDCCH formats and coding rate protections ” Effective supported PDCCH aggregation levels need to result in code rate < 0.75 18-Jan-2014 Free Print and Non-Commercial Publishing 52
  • 53. Physical Downlink Shared Channel (PDSCH) Transmits DL packet data One Transport Block transmission per UE’s code word per subframe A common MCS per code word per UE across all allocated RBs ”Independent MCS for two code words per UE 7 PDSCH Tx modes Mapping to Resource Blocks (RBs) Mapping for a particular transmit antenna port shall be in increasing order of: ”First the frequency index, ”Then the time index, starting with the first slot ina subframe. 18-Jan-2014 Free Print and Non-Commercial Publishing 53
  • 54. Physical Downlink Shared Channel (PDSCH) PDSCH Generalized Transmission Scheme  Code Words (maximum of 2)  A code word represents an output from the channel coder  1 code word for rank 1 Transmission  2 code words for rank 2/3/4 Transmissions  Layer Mapping  Number of layers depends on the number of Tx antennas and Wireless Channel Rank  Fixed mapping schemes of code words to layers  Tx Antennas (maximum of 4)  Maximum of 4 antennas (potentially upto 4 layers)  Pre-coding  used to support spatial multiplexing  Code book based precoding 18-Jan-2014 Free Print and Non-Commercial Publishing 54
  • 55. Physical HARQ Indicator Channel (PHICH) Used for ACK/NAK of UL-SCH transmissions Transmitted in: Time ”Normal duration: 1st OFDM symbol ”Extended duration: Over 2 or 3 OFDM symbols Frequency ”Spanning all system bandwidth ”Mapping depending on Cell ID FDM multiplexed with other DL control channels Support of CDM multiplexing of multiple PHICHs 18-Jan-2014 Free Print and Non-Commercial Publishing 55
  • 56. DL Reference Signals (RS) The downlink reference signals consist of so-called reference symbols which are known symbols inserted within in the OFDM time/frequency grid.   Similar with Pilot signal of CDMA. Used for downlink physical channel demodulation and channel quality measurement (CQI) Three types of RS in protocol. Cell-Specific Reference Signal is essential and the other two types RS (MBSFN Specific RS & UE-Specific RS) are optional. Characteristics:    Cell-Specific Reference Signals are generated from cell-specific RS sequence and frequency shift mapping. RS sequence also carriers one of the 504 different Physical Cell ID. The two-dimensional reference signal sequences are generated as the symbol-by-symbol product of a two-dimensional orthogonal sequence and a two-dimensional pseudo-random sequence:  There are 3 different two-dimensional orthogonal sequences  There are 168 different two-dimensional pseudo-random sequences The frequency interval of RS is 6 subcarriers. RS distributes discretely in the time-frequency domain, sampling the channel situation which is the reference of DL demodulation. 18-Jan-2014 Free Print and Non-Commercial Publishing 56
  • 57. R0 One antenna port One Antenna Port DL Reference Signals (RS)  Downlink RS consist of know reference symbol locations  Antenna ports 0 and 1 R0 R0 Inserted in two OFDM symbols (1st and 3rd last OFDM symbol) of each slot.  6 subcarriers spacing and 2x staggering (45kHz frequency sampling) R0 R0 R0 R0  Antenna ports 2 and 3  Inserted in one OFDM symbol (2nd OFDM symbol) of each slot.  6 subcarriers spacing and 2x staggering across slots. R0 l0 l6 l0 l6 Resource element (k,l) Two antenna ports Two Antenna Ports R0 R0 R0 R0 R1 R0 R0 R0 Four antenna ports Four Antenna Ports R0 l6 R0 l0 R0 R0 even-numbered slots odd-numbered slots Antenna port 0 Antenna Port 0 18-Jan-2014 l6 l0 R2 R1 R1 even-numbered slots R3 R3 R2 l6 l0 R3 R2 l6 odd-numbered slots Antenna Antennaport 1 1 Port R1: RS transmitted in 1st ant port R2: RS transmitted in 2nd ant port R3: RS transmitted in 3rd ant port R4: RS transmitted in 4th ant port R2 R1 R1 l6 l0 l6 R1 R1 R0 l0 R1 R1 R0 Reference symbols on this antenna port l6 l0 R1 R0 Not used for transmission on this antenna port R1 R1 l6 l0 R0 R1 R1 R0 l0 R1 R1 l0 R3 l6 l0 even-numbered slots l6 odd-numbered slots Antenna Antenna port 2 2 Port l0 l6 l0 even-numbered slots l6 odd-numbered slots Antenna port 3 Antenna Port 3 Free Print and Non-Commercial Publishing 57
  • 58. DL Reference Signals (RS) ” Measurement Reference 3GPP is defining following measurements: ” RSRP (Reference Signal Received Power) ” RSRQ (Reference Signal Received Quality) RSRP, 3GPP definition  RSRP is the average received power of a single RS resource element.  UE measures the power of multiple resource elements used to transfer the reference signal but then takes an average of them rather than summing them.  Reporting range -44…-140 dBm 18-Jan-2014 Free Print and Non-Commercial Publishing 58
  • 59. DL Reference Signals (RS) ” Measurement Reference RSSI (Received Signal Strength Indicator)  RSSI not reported to eNodeB by UE ” Can be computed from RSRQ and RSRP that are reported by UE RSSI measures all power within the measurement bandwidth ” Measured over those OFDM symbols that contain RS ” Measurement bandwidth RRC-signalled to UE RSSI = wideband power= noise + serving cell power + interference power Without noise and interference, 100% DL PRB activity: RSSI=12*N*RSRP ” RSRP is the received power of 1 RE (3GPP definition) average of power levels received across all Reference Signal symbols within the considered measurement frequency bandwidth ” RSSI is measured over the entire bandwidth ” N: number of RBs across the RSSI is measured and depends on the BW Based on the above, under full load and high SNR: RSRP (dBm)= RSSI (dBm) -10*log (12*N) 18-Jan-2014 Free Print and Non-Commercial Publishing 59
  • 60. DL Reference Signals (RS) ” Measurement Reference RSRQ ,3GPP definition RSRQ = N x RSRP / RSSI ” N is the number of resource blocks over which the RSSI is measured, typically equal to system bandwidth ” RSSI is pure wide band power measurement, including intracell power, interference and noise RSRQ reporting range -3…-19.5dB 18-Jan-2014 Free Print and Non-Commercial Publishing 60
  • 61. Uplink RS (Reference Signal) Uplink RS (Reference Signal):  The uplink pilot signal, used for synchronization between EUTRAN and UE, as well as uplink channel estimation.  Two types of UL reference signals: [1] DM RS (Demodulation Reference Signal), -Associated with transmission of PUSCH or PUCCH -Purpose: Channel estimation for Uplink coherent demodulation/detection of the Uplink control and data channels -Transmitted in time/frequency depending on the channel type (PUSCH/PUCCH), format, and cyclic prefix type [2] SRS (Sounding Reference Signal), -Not associated with transmission of PUSCH or PUCCH -Purpose: Uplink channel quality estimation feedback to the Uplink scheduler (for Channel Dependent Scheduling) at the eNodeB -Transmitted in time/frequency depending on the SRS bandwidth and the SRS bandwidth configuration (some rules apply if there is overlap with PUSCH and PUCCH) 18-Jan-2014 Free Print and Non-Commercial Publishing 61
  • 62. Physical Random Access Channel (PRACH) Basic Principle of Random Access :  Random access is the procedure of uplink synchronization between UE and E-UTRAN.  Prior to random access, physical layer shall receive the following information from the higher layers:  Random access channel parameters: PRACH configuration, frequency position and preamble format, etc.  Parameters for determining the preamble root sequences and their cyclic shifts in the sequence set for the cell, in order to demodulate the random access preamble. 1.Either network indicates specific PRACH resource or UE selects from common PRACH resources. 2.UE sends random access preambles at increasing power. 3.UE receives random access response on the PDCCH which includes assigned resources for PUSCH transmission. “Physical Resource Blocks (PRB) and Modulation and Coding Scheme (MCS) 4.UE sends signaling and user data on PUSCH. 18-Jan-2014 Free Print and Non-Commercial Publishing 62
  • 63. Physical Uplink Shared & Control Channel (PUSCH & PUCCH) Physical Uplink Control Channel (PUCCH)  Carries Hybrid ACK/NACK reponse DL transmission ” Always transmitted using QPSK ” Is punctured into UL-SCH to avoid errors due to missed DL assignments and thus different interpretations of ACK/NACK symbols  Carries Sceduling Request (SR)  Carries CQI (Channel Quality Indicator) Physical Uplink Shared Channel (PUSCH)  Carries data from the Uplink Shared Channel (ULSCH) transport Channel. If data and control are transmitted simultaneously -> PUSCH ” control located in the same region as data (time multiplexed) ” required to preserve single-carrier properties If only control is transmitted -> PUCCH ” control located at reserved region at band edges ” one RB is shared by multiple UEs through orthogonal spreading sequences 18-Jan-2014 Free Print and Non-Commercial Publishing 63
  • 64. Initial Acquisition Procedure ( Cell Search) Cell search is the process of identifying and obtaining downlink synchronization to cells, so that the broadcast information from the cell can be detected. This procedure is used both at initial access and at handover. 18-Jan-2014 Free Print and Non-Commercial Publishing 64
  • 65. [4] LTE KEY TECHNOLOGY INTRODUCTION 18-Jan-2014 Free Print and Non-Commercial Publishing 65
  • 66. LTE MIMO (Multiple Input Multiple Output)  LTE specifications support the use of multiple antennas at both transmitter (tx) and receiver (rx). MIMO (Multiple Input Multiple Output) uses this antenna configuration.  LTE specifications support up to 4 antennas at the tx side and up to 4 antennas at the rx side (here referred to as 4x4 MIMO configuration). In the first release of LTE it is likely that the UE only has 1 tx antenna, even if it uses 2 rx antennas. This leads to that so called Single User MIMO (SU-MIMO) will be supported only in DL (and maximum 2x2 configuration).  OFDM works particularly well with MIMO ” MIMO becomes difficult when there is time dispersion ” OFDM sub-carriers are flat fading (no time dispersion)  3GPP supports one, two, or four transmit Antenna Ports  Multiple antenna ports  Multiple time-frequency grids  Each antenna port defined by an associated Reference Signal LTE DL transmission modes Multiple layers means that the time- and frequency resources (Resource Blocks) can be reused in the different layers up to a number of times corresponding to the channel rank. This means that the same resource allocation is made on all transmitted layers. 18-Jan-2014 Free Print and Non-Commercial Publishing 66
  • 67. LTE MIMO (Multiple Input Multiple Output) DL Single User MIMO ”with 2 antennas 18-Jan-2014 Free Print and Non-Commercial Publishing 67
  • 68. LTE MIMO (Multiple Input Multiple Output) DL Multi User MIMO (MU-MIMO) 18-Jan-2014 Free Print and Non-Commercial Publishing 68
  • 69. LTE MIMO (Multiple Input Multiple Output) UL Multi user MIMO (virtual MIMO) 18-Jan-2014 Free Print and Non-Commercial Publishing 69
  • 70. LTE MIMO Evolution 18-Jan-2014 Free Print and Non-Commercial Publishing 70
  • 71. CSFB (CIRCUIT SWITCHED FALLBACK ) LTE Voice Solution Options 18-Jan-2014 Free Print and Non-Commercial Publishing 71
  • 72. CSFB (CIRCUIT SWITCHED FALLBACK ) LTE Voice Solution in 3GPP & GSMA 18-Jan-2014 Free Print and Non-Commercial Publishing 72
  • 73. CSFB (CIRCUIT SWITCHED FALLBACK ) Voice Options Comparison in LTE Environment 18-Jan-2014 Free Print and Non-Commercial Publishing 73
  • 74. CSFB (CIRCUIT SWITCHED FALLBACK ) 18-Jan-2014 Free Print and Non-Commercial Publishing 74
  • 75. CSFB (CIRCUIT SWITCHED FALLBACK ) Flash CSFB (R9 Redirection with SIB) 18-Jan-2014 Free Print and Non-Commercial Publishing 75
  • 76. SON (SELF ORGANIZING NETWORKS) SON (Self Organization Network) is introduced in 3GPP release 8. This function of LTE is required by the NGMN (Next Generation Mobile Network) operators. From the point of view of the operator’s benefit and experiences, the early communication systems had bad O&M compatibility and high cost. New requirements of LTE are brought forward, mainly focus on FCAPSI (Fault, Configuration, Alarm, Performance, Security, Inventory) management:  Self-planning and Self-configuration, support plug and play  Self-Optimization and Self-healing  Self-Maintenance 18-Jan-2014 Free Print and Non-Commercial Publishing 76
  • 77. SON (SELF ORGANIZING NETWORKS) Three SON RRM functionalities have been standardized in Rel 8. 18-Jan-2014 Free Print and Non-Commercial Publishing 77
  • 78. SON_ANR (Automatic Neighbor Relation) The ANR function relies on cells broadcasting their identity on a global level ”E-UTRAN Cell Global Identifier (ECGI) “The eNB instructs UE to perform measurements on neighbor cells “The eNB can decide to add this neighbor relation and can use the Physical Cell ID and ECGI to: ”Look up transport layer address to the new eNB ”Update Neighbor Relation List ”If needed, set up a new X2 interface toward the new eNB  Main ANR management functions:     Automatic detection of missing neighboring cells Automatic evaluation of neighbor relations Automatic detection of Physical Cell Identifier (PCI) collisions Automatic detection of abnormal neighboring cell coverage   18-Jan-2014 Automatic Neighbor Relation (ANR) can automatically add and maintain neighbor relations. The initial network construction, however, should not fully depend on ANR for the following considerations:  ANR is closely related to traffic in the entire network  ANR is based on UE measurements but the delay is introduced in the measurements. After initial neighbor relations configured and the number of UEs increasing, some neighboring relations may be missing. In this case, ANR can be used to detect missing neighboring cells and add neighbor relations. Free Print and Non-Commercial Publishing 78
  • 79. SON_MLB( Mobility Load Balancing) 18-Jan-2014 Free Print and Non-Commercial Publishing 79
  • 80. END OF DOCUMENT 18-Jan-2014 Free Print and Non-Commercial Publishing 80