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LTE - Long Term Evolution

Long Term Evolution

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LTE - Long Term Evolution

  1. 1. Arief Hamdani Gunawan 21 November 2009
  2. 2. Main Topics <ul><li>Introduction </li></ul><ul><li>Network Architecture </li></ul><ul><li>System Architecture Evolution </li></ul><ul><li>Channels </li></ul><ul><li>Downlink Transmission Scheme </li></ul><ul><li>Uplink Transmission Scheme </li></ul><ul><li>MIMO </li></ul><ul><li>LTE-Advanced </li></ul><ul><li>Conclusion </li></ul>
  3. 3. LTE market situation based on HSPA success story <ul><li>HSPA growth is based on the uptake of mobile data services worldwide. </li></ul><ul><li>More than 250 networks worldwide have already commercially launched HSPA. </li></ul><ul><li>Mobile data traffic is growing exponentially, caused by mobile Internet offerings and improved user experience with new device types. </li></ul><ul><li>LTE is accepted worldwide as the long term evolution perspective for today’s 2G and 3G networks based on WCDMA/HSPA, GSM/EDGE, TD-SCDMA, and CDMA2000 technologies. </li></ul>Sources:, R&S
  4. 4. LTE background story the early days <ul><li>Work on LTE was initiated as a 3GPP release 7 study item “Evolved UTRA and UTRAN” in December 2004: </li></ul><ul><ul><li>“ With enhancements such as HSDPA and Enhanced Uplink, the 3GPP radio-access technology will be highly competitive for several years. However, to ensure competitiveness in an even longer time frame, i.e. for the next 10 years and beyond, a long term evolution of the 3GPP radio-access technology needs to be considered.” </li></ul></ul><ul><li>Basic drivers for LTE have been: </li></ul><ul><ul><li>Reduced latency </li></ul></ul><ul><ul><li>Higher user data rates </li></ul></ul><ul><ul><li>Improved system capacity and coverage </li></ul></ul><ul><ul><li>Cost-reduction. </li></ul></ul>
  5. 5. Introduction to LTE <ul><li>3GPP Long Term Evolution - the next generation of wireless cellular technology beyond 3G </li></ul><ul><li>Initiative taken by the 3rd Generation Partnership Project in 2004 </li></ul><ul><li>Introduced in Release 8 of 3GPP </li></ul><ul><li>Mobile systems likely to be deployed by 2010 </li></ul>
  6. 6. Major requirements for LTE identified during study item phase in 3GPP <ul><li>Higher peak data rates: 100 Mbps (downlink) and 50 Mbps (uplink) </li></ul><ul><li>Improved spectrum efficiency: 2-4 times better compared to 3GPP release 6 </li></ul><ul><li>Improved latency: </li></ul><ul><ul><li>Radio access network latency (user plane UE – RNC - UE) below 10 ms </li></ul></ul><ul><ul><li>Significantly reduced control plane latency </li></ul></ul><ul><li>Support of scalable bandwidth: 1.4, 3, 5, 10, 15, 20 MHz </li></ul><ul><li>Support of paired and unpaired spectrum (FDD and TDD mode) </li></ul><ul><li>Support for interworking with legacy networks </li></ul><ul><li>Cost-efficiency: </li></ul><ul><ul><li>Reduced CA pital and OP erational EX penditures (CAPEX, OPEX) including backhaul </li></ul></ul><ul><ul><li>Cost-effective migration from legacy networks </li></ul></ul><ul><li>A detailed summary of requirements has been captured in 3GPP TR 25.913 „Requirements for Evolved UTRA (E-UTRA) and Evolved UTRAN (E-UTRAN)”. </li></ul>
  7. 7. 3G deployment in the world China Mobile NTT DoCoMo ( 2010 ) KDDI Verizon ( 2009 ) AT&T W ( 2010 ) Vodafone ( 2011 ) T-Mobile ( 2010 ) China Telecom HSPA+ DL>40MBps; UL>10Mbps TD-HSDPA 2.8~8.4Mbps TD-HSUPA 2.2~6.6Mbps WCDMA 384Kbps HSDPA 1.8/3.6Mbps HSDPA 7.2Mbps HSUPA 1.4~5.8Mbps LTE TDD DL:100Mbps UL:50Mbps TD-HSPA+ DL:>25.2Mbps UL:>19.2Mbps EV-DO Rel. 0 DL: 2.4Mbps UL:153.6kbps cdma2000 1x 153.6kbps D0 Rel. A DL: 3.1Mbps UL: 1.8Mbps Do Rev B (Multi Carrier DO) DL : 46.5Mbps UL: 27Mbps LTE FDD DL:100Mbps UL:50Mbps LTE TDD1 LTE TDD2
  8. 8. Trend of B3G ITU IMT-Advanced(4G) UMB + 100Mbps-1Gbps 100Mbps~ 1Gbps LTE+ FDD/TDD DL:100Mbps UL:50Mbps LTE-FDD WIMAX 3GPP 3GPP2 B3G EV-DO Rel. 0 DL: 2.4Mbps UL:153.6kbps cdma2000 1x 153.6kbps D0 Rel. A DL: 3.1Mbps UL: 1.8Mbps Do Rev B ( 多载波 DO ) DL : 46.5Mbps UL: 27Mbps UMB DL: 100Mbps UL: 50Mbps TD-HSPA+ DL:>25.2Mbps UL:>19.2Mbps TD-HSDPA 2.8~8.4Mbps TD-HSUPA 2.2~6.6Mbps HSPA+ DL>40MBps; UL>10Mbps WCDMA 384Kbps HSDPA 1.8/3.6Mbps HSDPA 7.2Mbps HSUPA 1.4~5.8Mbps GREAN ~600kbps GPRS/EDGE ~ 200kbps LTE-TDD DL:100Mbps UL:50Mbps 16m 100Mbps~1Gbps Mobile WiMAX Wave1 15Mbps Mobile WiMAX Wave2 30Mbps
  9. 9. 4G Technologies Mobile WiMAX 3GPP IP E2E Network IP E2E Network CKT Switched Network OFDMA - Based CDMA - Based IMT- Advanced 2008 2009 2010 2011 2012
  10. 10. Evolution of UMTS FDD and TDD driven by data rate and latency requirements
  11. 11. LTE Network Architecture
  12. 12. LTE will Ensure the Success of Mobile Internet
  13. 13. LTE Offers 10-30x Improvement on cost/performance vs. existing technologies
  14. 14. LTE – The Right Solution for Mobile Internet
  15. 15. What’s Happening in Mobile Internet World -- Device Providers --
  16. 16. LTE Key Parameters
  17. 17. Modulation <ul><li>QPSK, 16 QAM and 64 QAM used for the payload channels (spectrally efficient) </li></ul><ul><li>BPSK and QPSK used for the control channels (Reliability and coverage) </li></ul><ul><li>Adaptive modulation and coding </li></ul>
  18. 18. Requirements to be met by LTE Fast, Efficient, Cheap, Simple <ul><li>Peak Data Rates </li></ul><ul><li>Spectrum efficiency </li></ul><ul><li>Reduced Latency </li></ul><ul><li>Mobility </li></ul><ul><li>Spectrum flexibility </li></ul><ul><li>Coverage </li></ul><ul><li>Low complexity and cost </li></ul><ul><li>Interoperability </li></ul><ul><li>Simple packet-oriented E-UTRAN architecture </li></ul>
  19. 19. Simplified LTE network elements and interfaces 3GPP TS 36.300 Figure 4: Overall Architecture eNB = E-UTRAN Node B All radio interface-related functions MME = Mobile Management entity – Manages mobility, UE identity, and security parameters. S-GW = Serving Gateway – Node that terminates the interface towards E-UTRAN. P-GW = PDN (Packet Data Network) Gateway – Node that terminates the interface towards PDN.
  20. 20. LTE Network Architecture <ul><li>Simple Architecture </li></ul><ul><li>Flat IP-Based Architecture </li></ul><ul><li>Reduction in latency and cost </li></ul><ul><li>Split between EPC and E-UTRAN </li></ul><ul><li>Compatibility with 3GPP and non-3GPP technologies </li></ul><ul><li>eNB-radio interface-related functions </li></ul><ul><li>MME-manages mobility, UE identity and security parameters </li></ul><ul><li>S-GW-node that terminates the interface towards E-UTRAN </li></ul><ul><li>EPC = Evolved Packet Core </li></ul><ul><li>E-UTRAN = Evolved Universal Radio Access Network </li></ul><ul><li>MME = Mobile Management entity </li></ul><ul><li>S-GW = Serving Gateway </li></ul><ul><li>SAE = System Architecture Evolution </li></ul><ul><li>eNB = E-UTRAN Node B </li></ul>
  21. 21. PDCP = Packet Data Convergence Protocol RRC = Radio Resource Control RLC = Radio Link Control
  22. 22. Protocol
  23. 23. System Architecture Evolution <ul><li>SAE is a study within 3GPP targeting at the evolution of the overall system architecture. </li></ul><ul><li>Objective is “to develop a framework for an evolution or migration of the 3GPP system to a higher-data-rate, lower-latency, packet optimized system that supports multiple radio access technologies. </li></ul><ul><li>The focus of this work is on the PS domain with the assumption that voice services are supported in this domain&quot;. This study includes the vision of an all-IP network. </li></ul>
  24. 24. Why LTE/SAE? <ul><li>Packet Switched data is becoming more and more dominant </li></ul><ul><li>VoIP is the most efficient method to transfer voice data </li></ul><ul><li> Need for PS optimised system </li></ul><ul><li>Amount of data is continuously growing </li></ul><ul><li> Need for higher data rates at lower cost </li></ul><ul><li>Users demand better quality to accept new services </li></ul><ul><li>High quality needs to be quaranteed </li></ul><ul><li>Alternative solution for non-3GPP technologies (WiMAX) needed </li></ul><ul><li>LTE will enhance the system to satisfy these requirements. </li></ul>
  25. 25. LTE Overview <ul><li>3GPP R8 solution for the next 10 years </li></ul><ul><li>Peaks rates: DL 100Mbps with OFDMA, UL 50Mbps with SC-FDMA </li></ul><ul><li>Latency for Control-plane < 100ms, for User-plane < 5ms </li></ul><ul><li>Optimised for packet switched domain, supporting VoIP </li></ul><ul><li>Scaleable RF bandwidth between 1.25MHz to 20MHz </li></ul><ul><li>200 users per cell in active state </li></ul><ul><li>Supports MBMS multimedia services </li></ul><ul><li>Uses MIMO multiple antenna technology </li></ul><ul><li>Optimised for 0-15km/h mobile speed and support for up-to 120-350 km/h </li></ul><ul><li>No soft handover, Intra-RAT handovers with UTRAN </li></ul><ul><li>Simpler E-UTRAN architecture: no RNC, no CS domain, no DCH </li></ul>
  26. 26. LTE technical objectives and architecture <ul><li>User throughput [/MHz] : </li></ul><ul><ul><li>Downlink: 3 to 4 times Release 6 HSDPA </li></ul></ul><ul><ul><li>Uplink: 2 to 3 times Release 6 Enhanced Uplink </li></ul></ul><ul><li>Downlink Capacity : Peak data rate of 100 Mbps in 20 MHz maximum bandwidth </li></ul><ul><li>Uplink capacity : Peak data rate of 50 Mbps in 20 MHz maximum bandwidth </li></ul><ul><li>Latency : Transition time less than 5 ms in ideal conditions (user plane), 100 ms control plane (fast connection setup) </li></ul>
  27. 27. <ul><li>Mobility : Optimised for low speed but supporting 120 km/h </li></ul><ul><ul><li>Most data users are less mobile! </li></ul></ul><ul><li>Simplified architecture : Simpler E-UTRAN architecture: no RNC, no CS domain, no DCH </li></ul><ul><li>Scalable bandwidth : 1.25MHz to 20MHz: Deployment possible in GSM bands. </li></ul>
  28. 28. LTE radio interface <ul><li>New radio interface modulation: SC-FDMA UL and OFDMA DL </li></ul><ul><ul><li>Frequency division, TTI 1 ms </li></ul></ul><ul><ul><li>Scalable bandwidth 1.25-20MHz </li></ul></ul><ul><ul><li>TDD and FDD modes </li></ul></ul><ul><ul><ul><li>UL/DL in either in same or in another frequncy </li></ul></ul></ul><ul><ul><li>OFDMA has multiple orthogonal subcarries that can be shared between users </li></ul></ul><ul><ul><ul><li>quickly adjustable bandwith per user </li></ul></ul></ul><ul><ul><li>SC-FDMA is technically similar to OFDMA but is better suited for uplink from hand-held devices </li></ul></ul><ul><ul><ul><li>Single carrier, time space multiplexing </li></ul></ul></ul><ul><ul><ul><li>Tx consumes less power </li></ul></ul></ul>From Ericsson, H. Djuphammar
  29. 29. LTE/SAE Keywords <ul><li>aGW Access Gateway </li></ul><ul><li>eNB Evolved NodeB </li></ul><ul><li>EPC Evolved Packet Core </li></ul><ul><li>E-UTRAN Evolved UTRAN </li></ul><ul><li>IASA Inter-Access System Anchor </li></ul><ul><li>LTE Long Term Evolution of UTRAN </li></ul><ul><li>MME Mobility Management Entity </li></ul><ul><li>OFDMA Ortogonal Frequency Division Multiple Access </li></ul><ul><li>SC-FDMA Single Carrier Frequency Division Multiple Access </li></ul><ul><li>SAE System Architecture Evolution </li></ul><ul><li>UPE User Plane Entity </li></ul>
  30. 30. 3GPP TR 23.401 / 25.813 <ul><li>PLMN –Public Land Mobile Network </li></ul><ul><li>EPS –Evolved Packet System </li></ul><ul><li>MME –Mobility Management Entity </li></ul><ul><li>eNB–E-UTRAN Node B </li></ul><ul><li>TAI -Tracking Area ID </li></ul><ul><li>E-UTRAN –Evolved Universal Radio Access Network </li></ul><ul><li>C-RNTI –Cell Radio Network Temporary Identifier </li></ul><ul><li>RA-RNTI –Random Access RNTI </li></ul><ul><li>UE –User Equipment </li></ul><ul><li>IMEI –International Mobile Equipment Identity </li></ul><ul><li>IMSI –International Mobile Subscriber Identity </li></ul><ul><li>S-TMSI –SAE Temporary Mobile Subscriber Identity </li></ul>Network Entities: MME ID eNB ID TAI Network: PLMN EPS ID EUTRAN: E-UTRAN C-RNTI RA-RNTI UE: IMEI IMSI S-TMSI LTE/SAE Network Identifiers
  31. 31. System architecture evolution
  32. 32. RAN interfaces <ul><li>X2 interface between eNBs for handovers </li></ul><ul><li>Handover in 10 ms </li></ul><ul><li>No soft handovers </li></ul><ul><li>Interfaces using IP over E1/T1/ATM/Ethernet /… </li></ul><ul><li>Load sharing in S1 </li></ul><ul><li>S1 divided to S1-U (to UPE) and S1-C (to CPE) </li></ul><ul><li>Single node failure has limited effects </li></ul>S1 S8 X2 X2 eNB aGW eNB aGW eNB
  33. 33. SAE architecture [3GPP TS 23.401] Evolved Packet Core S11 S2 S3 S4 S7 S6 SGi S1 Gb Iu Rx+ X1 X1 X2 Evolved RAN aGW S5 GERAN UTRAN GPRS Core MME UPE SAE GW PCRF Operator IP services (including IMS, PSS, ...) Non-3GPP IP Access eNB eNB PDN SAE GW HSS
  34. 34. SAE architechture [3GPP TS 23.401] S1 TBD S8 X2 Operator IP service, including IMS S11 S11 S5 SGi Evolved RAN IASA aGW = MME/UPE S6a S7 TBD eNB TBD eNB aGW eNB SAE GW PDN SAE GW HSS PCRF aGW
  35. 35. Functions of eNB <ul><li>Terminates RRC, RLC and MAC protocols and takes care of Radio Resource Management functions </li></ul><ul><ul><li>Controls radio bearers </li></ul></ul><ul><ul><li>Controls radio admissions </li></ul></ul><ul><ul><li>Controls mobility connections </li></ul></ul><ul><ul><li>Allocates radio resources dynamically (scheduling) </li></ul></ul><ul><ul><li>Receives measurement reports from UE </li></ul></ul><ul><li>Selects MME at UE attachment </li></ul><ul><li>Schedules and transmits paging messages coming from MME </li></ul><ul><li>Schedules and transmits broadcast information coming from MME & O&M </li></ul><ul><li>Decides measurement report configuration for mobility and scheduling </li></ul><ul><li>Does IP header compression and encryption of user data streams </li></ul>
  36. 36. Functions of aGW <ul><li>Takes care of Mobility Management Entity (MME) functions </li></ul><ul><ul><li>Manages and stores UE context </li></ul></ul><ul><ul><li>Generates temporary identities and allocates them to UEs </li></ul></ul><ul><ul><li>Checks authorization </li></ul></ul><ul><ul><li>Distributes paging messages to eNBs </li></ul></ul><ul><ul><li>Takes care of security protocol </li></ul></ul><ul><ul><li>Controls idle state mobility </li></ul></ul><ul><ul><li>Control SAE bearers </li></ul></ul><ul><ul><li>Ciphers & integrity protects NAS signaling </li></ul></ul>
  37. 37. <ul><li>Takes care of User Plane Entity (UPE) functions </li></ul><ul><ul><li>Terminates for idle state UEs the downlink data path and triggers/initiates paging when downlink data arrive for the UE. </li></ul></ul><ul><ul><li>Manages and stores UE contexts, e.g. parameters of the IP bearer service or network internal routing information. </li></ul></ul><ul><ul><li>Switches user plane for UE mobility </li></ul></ul><ul><ul><li>Terminates user plane packets for paging reasons </li></ul></ul>
  38. 38. Functions S1
  39. 39. <ul><li>LTE Control Plane </li></ul>aGW UE eNB S1 RRC RLC MAC PHY PDCP RRC RLC MAC PHY PDCP NAS NAS
  40. 40. <ul><li>LTE User Plane </li></ul>aGW UE eNB S1 RLC MAC PHY PDCP RLC MAC PHY PDCP IP IP
  41. 41. GTP-U tunneling SAE GW UPE eNB Server UE L1 L2 X1 S1 S11 SGi S5 PDN SAE GW Header compression & encryption Radio L1 MAC PDCP IPv6/v4 u Application TCP/UDP RLC L1 L2 IP UDP GTP-U L2 L1 IP UDP GTP-U L2 L1 IP UDP GTP-U L2 L1 IPv6/v4 TCP/UDP Application L1 L2 IP UDP GTP-U L2 L1 IP UDP GTP-U L2 L1 IP UDP GTP-U L2 L1 Radio L1 MAC RLC PDCP ENC
  42. 42. Non-3GPP access tunneling PDN SAE GW HA AP Server UE IP L2 L1 IPv6/v4 TCP/UDP Application L1 L2 WLAN S2 SGi L2 L1 IP MIP IPv4/6 IP UDP IP MIP IPv4/6 UDP IP L2 L1 IP L2 L1 L1 L2 L1 L2
  43. 43. LTE Physical Layer <ul><li>Enables exchange of data & control info between eNB and UE and also transport of data to and from higher layers </li></ul><ul><li>Functions performed include error detection, FEC, MIMO antenna processing, synchronization, etc. </li></ul><ul><li>It consists of Physical Signals and Physical Channels </li></ul><ul><li>Physical Signals are used for system synchronization, cell identification and channel estimation. </li></ul><ul><li>Physical Channels for transporting control, scheduling and user payload from the higher layers </li></ul><ul><li>OFDMA in the DL, SC-FDMA in the UL </li></ul><ul><li>LTE supports FDD and TDD modes of operation </li></ul>
  44. 44. Channel Mapping
  45. 45. LTE Physical Signals
  46. 46. LTE Physical Channels
  47. 47. LTE Transport Channels <ul><li>Physical layer transport channels offer information transfer to medium access control (MAC) and higher layers. </li></ul><ul><li>DL </li></ul><ul><ul><li>Broadcast Channel (BCH) </li></ul></ul><ul><ul><li>Downlink Shared Channel (DL-SCH) </li></ul></ul><ul><ul><li>Paging Channel (PCH) </li></ul></ul><ul><ul><li>Multicast Channel (MCH) </li></ul></ul><ul><li>UL </li></ul><ul><ul><li>Uplink Shared Channel (UL-SCH) </li></ul></ul><ul><ul><li>Random Access Channel (RACH) </li></ul></ul>
  48. 48. LTE Logical Channels <ul><li>Logical channels are offered by the MAC layer. </li></ul><ul><li>Control Channels: Control-plane information </li></ul><ul><ul><li>Broadcast Control Channel (BCCH) </li></ul></ul><ul><ul><li>Paging Control Channel (PCCH) </li></ul></ul><ul><ul><li>Common Control Channel (CCCH) </li></ul></ul><ul><ul><li>Multicast Control Channel (MCCH) </li></ul></ul><ul><ul><li>Dedicated Control Channel (DCCH) </li></ul></ul><ul><li>Traffic Channels: User-plane information </li></ul><ul><ul><li>Dedicated Traffic Channel (DTCH) </li></ul></ul><ul><ul><li>Multicast Traffic Channel (MTCH) </li></ul></ul>
  49. 49. LTE Frame Structure (Downlink) <ul><li>LTE Frame Structure Type I (FDD) </li></ul><ul><li>LTE Frame Structure Type II (TDD) </li></ul>
  50. 51. FDD (left) and TDD (right) frequency bands defined in the 3GPP (May 2009)
  51. 52. Downlink Transmission Scheme <ul><li>The downlink transmission scheme for E-UTRA FDD and TDD modes is based on conventional OFDM. In an OFDM system, the available spectrum is divided into multiple carriers, called sub-carriers, which are orthogonal to each other. Each of these sub-carriers is independently modulated by a low rate data stream. </li></ul><ul><li>OFDM is used as well in WLAN, WiMAX and broadcast technologies like DVB. OFDM has several benefits including its robustness against multipath fading and its efficient receiver architecture. </li></ul>
  52. 53. OFDM <ul><li>Single Carrier Transmission (e.g. WCDMA) </li></ul><ul><li>Orthogonal Frequency Division Multiplexing </li></ul>
  53. 54. OFDM signal generation chain <ul><li>OFDM signal generation is based on Inverse Fast Fourier Transform (IFFT) operation on transmitter side: </li></ul>On receiver side, an FFT operation will be used.
  54. 55. Modulation <ul><li>QPSK, 16 QAM and 64 QAM used for the payload channels (spectrally efficient) </li></ul><ul><li>BPSK and QPSK used for the control channels (Reliability and coverage) </li></ul><ul><li>Adaptive modulation and coding </li></ul>
  55. 56. Difference between OFDM and OFDMA <ul><li>OFDM allocates users in time domain only </li></ul><ul><li>OFDMA allocates users in time and frequency domain </li></ul>
  56. 57. LTE downlink conventional OFDMA Frequency-Time Representation of an OFDM Signal <ul><li>LTE provides QPSK, 16QAM, 64QAM as downlink modulation schemes </li></ul><ul><li>Cyclic prefix is used as guard interval, different configurations possible: </li></ul><ul><ul><li>Normal cyclic prefix with 5.2 Os (first symbol) / 4.7 Os (other symbols) </li></ul></ul><ul><ul><li>Extended cyclic prefix with 16.7 Os </li></ul></ul><ul><li>15 kHz subcarrier spacing </li></ul><ul><li>Scalable bandwidth </li></ul>
  57. 58. Frequency and Time Domain Representation <ul><li>Frequency Time </li></ul>
  58. 59. OFDMA time-frequency multiplexing
  59. 60. LTE – spectrum flexibility <ul><li>LTE physical layer supports any bandwidth from 1.4 MHz to 20 MHz in steps of 180 kHz (resource block) </li></ul><ul><li>Current LTE specification supports a subset of 6 different system bandwidths </li></ul><ul><li>All UEs must support the maximum bandwidth of 20 MHz </li></ul>
  60. 61. Generic frame structure in E-UTRA downlink <ul><li>For the generic frame structure frame structure, the 10 ms radio frame is divided into 20 equally sized slots of 0.5 ms. </li></ul><ul><li>A sub-frame consists of two consecutive slots, so one radio frame contains 10 sub-frames. </li></ul>
  61. 62. Downlink Resource Grid <ul><li>The available downlink bandwidth consists of N DL BW sub-carriers with a spacing of Δ f = 15 kHz. In case of multi cell MBMS transmission, </li></ul><ul><li>a sub-carrier spacing of Δ f = 7.5 kHz is also possible. </li></ul><ul><li>N DL BW can vary in order to allow for scalable bandwidth operation up to 20 MHz. Initially, the bandwidths for LTE were explicitly defined within layer 1 specifications. </li></ul><ul><li>Later on a bandwidth agnostic layer 1 was introduced, with N DL BW for the different bandwidths to be specified by 3GPP RAN4 to meet performance requirements, e.g. for out-of-band emission requirements and regulatory emission limits </li></ul>
  62. 63. The LTE downlink physical resource based on OFDM
  63. 64. Parameters for downlink generic frame structure
  64. 65. Downlink Data Transmission <ul><li>The user data is carried on the Physical Downlink Shared Channel ( PDSCH ). </li></ul><ul><li>Downlink control signaling on the Physical Downlink Control Channel ( PDCCH ) is used to convey the scheduling decisions to individual UEs. </li></ul><ul><li>The PDCCH is located in the first OFDM symbols of a slot. </li></ul>
  65. 66. Downlink Reference Signal Structure and Cell Search <ul><li>The downlink reference signal structure is important for cell search, channel estimation and neighbor cell monitoring. </li></ul><ul><li>The reference signal sequence carries the cell identity. </li></ul>
  66. 67. Downlink reference signal structure
  67. 68. P-SCH and S-SCH <ul><li>Besides the reference symbols, synchronization signals are therefore needed during cell search. </li></ul><ul><li>E-UTRA uses a hierarchical cell search scheme similar to WCDMA. </li></ul><ul><li>This means that the synchronization acquisition and the cell group identifier are obtained from different SCH signals. </li></ul><ul><li>Thus, a primary synchronization signal (P-SCH) and a secondary synchronization signal (S-SCH) are defined with a pre-defined structure. </li></ul><ul><li>They are transmitted on the 72 centre sub-carriers (around DC sub-carrier) within the same predefined slots (twice per 10 ms) on different resource elements </li></ul>
  68. 69. P-SCH and S-SCH structure
  69. 70. CCPCH <ul><li>As additional help during cell search, a Common Control Physical Channel ( CCPCH) is available which carries BCH type of information, e.g. system bandwidth. </li></ul><ul><li>It is transmitted at pre-defined time instants on the 72 subcarriers centered around DC sub-carrier. </li></ul>
  70. 71. Downlink Physical Layer Procedures <ul><li>Cell search and synchronization: </li></ul><ul><li>Scheduling: Scheduling is done in the base station (eNodeB). The downlink control channel PDCCH informs the users about their allocated time/frequency resources and the transmission formats to use. The scheduler evaluates different types of information, e.g. Quality of Service parameters, measurements from the UE, UE capabilities, buffer status. </li></ul><ul><li>Link Adaptation: Link adaptation is already known from HSDPA as Adaptive Modulation and Coding. Also in E-UTRA, modulation and coding for the shared data channel is not fix, but it is adapted according to radio link quality. For this purpose, the UE regularly reports Channel Quality Indications (CQI) to the eNodeB. </li></ul><ul><li>Hybrid ARQ (Automatic Repeat Request): Downlink Hybrid ARQ is also known from HSDPA. It is a retransmission protocol. The UE can request retransmissions of incorrectly received data packets. </li></ul>
  71. 72. DL Physical Channel Processing
  72. 73. LTE frame structure type 1 (FDD), downlink
  73. 74. LTE frame structure type 2 (TDD)
  74. 75. Uplink Transmission Scheme <ul><li>During the study item phase of LTE, alternatives for the optimum uplink transmission scheme were investigated. </li></ul><ul><li>While OFDMA is seen optimum to fulfil the LTE requirements in downlink, OFDMA properties are less favorable for the uplink. This is mainly due to weaker peak-to-average power ratio (PAPR) properties of an OFDMA signal, resulting in worse uplink coverage. </li></ul>
  75. 76. Single-Carrier Frequency Division Multiple Access (SC-FDMA) <ul><li>Thus, the LTE uplink transmission scheme for FDD and TDD mode is based on SC-FDMA (Single Carrier Frequency Division Multiple Access) with cyclic prefix. </li></ul><ul><li>SC-FDMA signals have better PAPR properties compared to an OFDMA signal. </li></ul><ul><li>This was one of the main reasons for selecting SCFDMA as LTE uplink access scheme. </li></ul><ul><li>The PAPR characteristics are important for cost-effective design of UE power amplifiers. </li></ul><ul><li>Still, SC-FDMA signal processing has some similarities with OFDMA signal processing, so parameterization of downlink and uplink can be harmonized. </li></ul>
  76. 77. How to generate SC-FDMA <ul><li>DFT “pre-coding” is performed on modulated data symbols to transform them into frequency domain, </li></ul><ul><li>Sub-carrier mapping allows flexible allocation of signal to available sub-carriers, </li></ul><ul><li>IFFT and cyclic prefix (CP) insertion as in OFDM, </li></ul>Each subcarrier carries a portion of superposed DFT spread data symbols, therefore SC-FDMA is also referred to as DFT-spread-OFDM (DFT-s-OFDM).
  77. 78. How does a SC-FDMA signal look like <ul><li>Similar to OFDM signal, but… </li></ul><ul><li>… in OFDMA, each sub-carrier only carries information related to one specific symbol, </li></ul><ul><li>… in SC-FDMA, each sub-carrier contains information of ALL transmitted symbols. </li></ul>
  78. 79. OFDMA and SC-FDMA
  79. 80. Why does SC-FDMA have a low PAPR? <ul><li>OFDMA </li></ul><ul><li>Parallel Transmission </li></ul><ul><li>Multi carrier structure </li></ul><ul><li>Increase in M => </li></ul><ul><li>high PAPR </li></ul><ul><li>SC-FDMA </li></ul><ul><li>Serial Transmission </li></ul><ul><li>Each symbol </li></ul><ul><li>represented by a </li></ul><ul><li>wide signal – DFT spreads </li></ul><ul><li>symbols over all subcarriers </li></ul><ul><li>PAPR not affected by </li></ul><ul><li>increase in M </li></ul><ul><li>Both occupy the same bandwidth with same symbol durations </li></ul>
  80. 81. SC-FDMA in comparison with OFDMA and DS-CDMA/FDE
  81. 82. SC-FDMA signal generation Localized vs. distributed FDMA
  82. 83. Uplink Slot Structure
  83. 84. Parameters for uplink generic structure
  84. 85. Uplink Data Transmission <ul><li>In uplink, data is allocated in multiples of one resource block. Uplink resource block size in the frequency domain is 12 sub-carriers, i.e. the same as in downlink. </li></ul><ul><li>However, not all integer multiples are allowed in order to simplify the DFT design in uplink signal processing. </li></ul><ul><li>Only factors 2,3, and 5 are allowed. </li></ul><ul><li>The uplink transmission time interval is 1 ms (same as downlink). </li></ul>
  85. 86. PUSCH and PUCCH <ul><li>User data is carried on the Physical Uplink Shared Channel ( PUSCH ) that is determined by the transmission bandwidth NTx and the frequency hopping pattern k0. </li></ul><ul><li>The Physical Uplink Control Channel ( PUCCH ) carries uplink control information, e.g. CQI reports and ACK/NACK information related to data packets received in the downlink. The PUCCH is transmitted on a reserved frequency region in the uplink. </li></ul>
  86. 87. Uplink Reference Signal Structure <ul><li>Uplink reference signals are used for two different purposes: on the one hand, they are used for channel estimation in the eNodeB receiver in order to demodulate control and data channels. </li></ul><ul><li>On the other hand, the reference signals provide channel quality information as a basis for scheduling decisions in the base station. The latter purpose is also called channel sounding. </li></ul><ul><li>The uplink reference signals are based on CAZAC (Constant Amplitude Zero Auto-Correlation) sequences. </li></ul>
  87. 88. UL Physical Channel Processing
  88. 89. Cell Search <ul><li>Cell search: Mobile terminal or user equipment (UE) acquires time and frequency synchronization with a cell and detects the cell ID of that cell. </li></ul><ul><ul><li>Based on BCH (Broadcast Channel) signal and hierarchical SCH (Synchronization Channel) signals. </li></ul></ul><ul><li>P-SCH (Primary-SCH) and S-SCH (Secondary-SCH) are transmitted twice per radio frame (10 ms) for FDD. </li></ul><ul><li>Cell search procedure </li></ul><ul><li>1. 5 ms timing identified using P-SCH. </li></ul><ul><li>2. Radio timing and group ID found from S-SCH. </li></ul><ul><li>3. Full cell ID found from DL RS. </li></ul><ul><li>4. Decode BCH. </li></ul>
  89. 90. Spatial Multiplexing Spatial multiplexing allows to transmit different streams of data simultaneously on the same downlink resource block(s). These data streams can belong to one single user (single user MIMO / SU-MIMO) or to different users (multi user MIMO / MU-MIMO). While SU-MIMO increases the data rate of one user, MU-MIMO allows to increase the overall capacity. Spatial multiplexing is only possible if the mobile radio channel allows it.
  90. 91. LTE MIMO concept
  91. 92. Multiple Antenna Schemes in LTE <ul><li>In DL : Tx diversity, Rx diversity, Spatial multiplexing (2x2,4x2 configurations – SU-MIMO and MU-MIMO) supported </li></ul><ul><li>In UL : Only 1 Transmitter (antenna selection Tx diversity ), MU-MIMO possible, Rx diversity with 2 or 4 antennas at eNB supported </li></ul>
  92. 93. LTE cooperative MIMO
  93. 94. Collaborative/Network MIMO overview Coordinate transmission and reception of signals among multiple bases. Reduces intercell interference and improves cell-edge performance and overall throughput. Collaborative MIMO : share user data and long-term noncoherent channel information. Coherent network MIMO : share user data and short-term coherent channel information.
  94. 95. Multi-Mode Adaptive MIMO for DL/UL <ul><li>Use adaptive MIMO to accommodate demand of higher data rate and wider coverage in next generation broadband wireless access </li></ul><ul><li>SU MIMO for peak user data rate improvement </li></ul><ul><li>MU MIMO for average data rate enhancement </li></ul><ul><li>Collaborative/Network MIMO for cell edge user data rate boost </li></ul>A uniform MIMO platform SU-MIMO MU-MIMO Collaborative/ Network MIMO adaptive selection MAC layer Cross-layer design
  95. 96. Key technologies in Multi-mode Adaptive MIMO Cellular system Collaborative/Network MIMO MU-MIMO SU-MIMO <ul><li>SU-MIMO enhancement </li></ul><ul><li>Closed-loop MIMO </li></ul><ul><li>Iterative MIMO receiver </li></ul><ul><li>MU-MIMO optimization </li></ul><ul><li>MU precoding algorithm </li></ul><ul><li>Trade-off design of scheduler between complexity and performance </li></ul><ul><li>Collaborative/Network MIMO/Beam Coordination </li></ul><ul><li>Implementation of multi-BS collaboration with channel information </li></ul><ul><li>Multi-dimension adaptation </li></ul><ul><li>Adaptation strategy </li></ul><ul><li>Multi-variable channel measurement </li></ul><ul><li>Low-rate feedback mechanism </li></ul>Multicast Anchor Serving eNB/ per User Data + Sync Protocol for DL (Extension of eMBMS protocol); Data + Channel Estimates for UL eNBs have to be synchronized !!! MIMO channel
  96. 97. <ul><li>LTE doesn’t fulfill the requirements of IMT-Advanced </li></ul><ul><li>3GPP has also started work on LTE-Advanced, an evolution of LTE, as a proposal to ITU-R for the development of IMT Advanced. </li></ul><ul><li>LTE Advanced is envisioned to be the “first true 4G technology”. </li></ul>
  97. 98. Requirements of LTE Advanced <ul><li>Peak data rates – 1Gbps in DL and 500 Mbps in UL </li></ul><ul><li>Cell edge user data rates twice as high and average user throughput thrice as high as in LTE </li></ul><ul><li>Peak spectrum efficiency DL: 30 bps/Hz, UL: 15 bps/Hz </li></ul><ul><li>Operate in flexible spectrum allocations up to 100 MHz and support spectrum aggregation (as BW in DL >>20 MHz) </li></ul><ul><li>An LTE-Advanced capable network must appear as a LTE network for the LTE UEs </li></ul>
  98. 99. Technological proposals for LTE Advanced <ul><li>Larger BW can be used for high date rates and more coverage at cell edges </li></ul><ul><li>Advanced repeater structures </li></ul><ul><li>Relaying for adaptive coding based on link quality </li></ul>Carrier aggregation and Spectrum aggregation
  99. 100. Conclusion <ul><li>3GPP Long Term Evolution has a large amount of potential to become the technology of the future whose success will definitely guarantee that 3GPP has a significant edge over all its competitors. </li></ul><ul><li>With LTE–Advanced also adopting SC-FDMA as the uplink technology, SC-FDMA seems to be an important future technology and it is expected that the future would see a lot of research activity in this field. </li></ul><ul><li>LTE and LTE Advanced together seem to be very promising in fulfilling all the requirements set forth by ITU for IMT Advanced </li></ul>
  100. 101. References <ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li>UTRA-UTRAN Long Term Evolution (LTE) and 3GPP System Architecture Evolution (SAE) - Technical paper from </li></ul><ul><li>Overview of the 3GPP Long Term Evolution Physical Layer – White paper by Jim Zyren, freescale semiconductor, Document Number: 3GPPEVOLUTIONWP: </li></ul><ul><li>3GPP TR 25.913 V8.0.0 (2008-12), “Requirements for Evolved UTRA (E-UTRA) and Evolved UTRAN (E-UTRAN) (Release 8)” </li></ul><ul><li>3GPP TS 36.300 v8.7.0, “E-UTRA and E-UTRAN Overall Description; Stage 2” </li></ul><ul><li>3GPP TS 36.401 V8.4.0 (2008-12), “Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Architecture description (Release 8)” </li></ul><ul><li>3GPP TS 36.410 V8.1.0 (2008-12), “Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 General aspects and principles (Release 8)” </li></ul><ul><li>3GPP TS 36.420 V8.1.0 (2008-12), “Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 general aspects and principles (Release 8)” </li></ul><ul><li>3GPP TS 36.201 V8.2.0 (2008-12), “Evolved Universal Terrestrial Radio Access (E-UTRA); LTE Physical Layer – General Description (Release 8)” </li></ul><ul><li>3GPP Long-Term Evolution (LTE) – Qualcomm Incorporated, January 2008: </li></ul><ul><li>Technical Overview of 3GPP LTE – Hyung G. Myung: </li></ul><ul><li>LTE Overview – NEC Corporation – By K. Jay Miyahara: </li></ul><ul><li>Agilent 3GPP Long Term Evolution: System Overview, Product Development, and Test Challenges: </li></ul><ul><li>Ekstrom, H.; Furuskar, A.; Karlsson, J.; Meyer, M.; Parkvall, S.; Torsner, J.; Wahlqvist, M., “Technical solutions for the 3G long-term evolution” Communications Magazine, IEEE Volume 44,  Issue 3 ,  March 2006 Page(s): 38 - 45 </li></ul><ul><li> </li></ul><ul><li>Long Term Evolution (LTE); A Technical Overview – Technical White Paper: </li></ul><ul><li>3GPP LTE: Introducing Single - Carrier FDMA – By Moray Rumney, Agilent Technologies: </li></ul><ul><li>Single Carrier Orthogonal Multiple Access Technique for Broadband Wireless Communications –Dissertation by Hyung G. Myung: http:// </li></ul><ul><li>Priyanto, B.E.; Codina, H.; Rene, S.; Sorensen, T.B.; Mogensen, P., “Initial Performance Evaluation of DFT-Spread OFDM Based SC-FDMA for UTR LTE Uplink” Vehicular Technology Conference, 2007. VTC2007-Spring. IEEE 65th 22-25 April 2007 Page(s):3175 - 3179 </li></ul>
  101. 102. References <ul><li>Myung, H.G.; Kyungjin Oh; Junsung Lim; Goodman, D.J., “Channel-Dependent Scheduling of an Uplink SC-FDMA System with Imperfect Channel Information” Wireless Communications and Networking Conference, 2008. WCNC 2008. IEEE March 31 2008-April 3 2008 Page(s):1860 - 1864 </li></ul><ul><li>Junsung Lim; Myung, H.G.; Kyungjin Oh; Goodman, D.J., “Proportional Fair Scheduling of Uplink Single-Carrier FDMA Systems” Personal, Indoor and Mobile Radio Communications, 2006 IEEE 17th International Symposium on 11-14 Sept. 2006 Page(s):1 - 6 </li></ul><ul><li>Junsung Lim; Myung, H.G.; Kyungjin Oh; Goodman, D.J., “Channel-Dependent Scheduling of Uplink Single Carrier FDMA Systems” Vehicular Technology Conference, 2006. VTC-2006 Fall. 2006 IEEE 64th 25-28 Sept. 2006 Page(s):1 - 5 </li></ul><ul><li>Yan Lin; Guangxin Yue, “Channel-Adapted and Buffer-Aware Packet Scheduling in LTE Wireless Communication System” Wireless Communications, Networking and Mobile Computing, 2008. WiCOM '08. 4th International Conference on 12-14 Oct. 2008 Page(s):1 - 4 </li></ul><ul><li>Ruiz de Temino, L.; Berardinelli, G.; Frattasi, S.; Mogensen, P., “Channel-aware scheduling algorithms for SC-FDMA in LTE uplink” Personal, Indoor and Mobile Radio Communications, 2008. PIMRC 2008. IEEE 19th International Symposium on 15-18 Sept. 2008 Page(s):1 - 6 </li></ul><ul><li>Saatsakis, A.; Tsagkaris, K.; von-Hugo, D.; Siebert, M.; Rosenberger, M.; Demestichas, P., “Cognitive Radio Resource Management for Improving the Efficiency of LTE Network Segments in the Wireless B3G World” New Frontiers in Dynamic Spectrum Access Networks, 2008. DySPAN 2008. 3rd IEEE Symposium on 14-17 Oct. 2008 Page(s):1 - 5 </li></ul><ul><li>Jung-Lin Pan; Olesen, R.; Grieco, D.; Chia-Pang Yen, “Efficient Feedback Design for MIMO SC-FDMA Systems” Vehicular Technology Conference, 2007. VTC2007-Spring. IEEE 65th 22-25 April 2007 Page(s):2399 - 2403 </li></ul><ul><li>Liu, Jin; Wang, Liang; You, Mingli; Wen, Pingping, “A Special Open-Loop Transmit Antenna Selection Mode in the SC-FDMA Systems for 3G LTE” Military Communications Conference, 2007. MILCOM 2007. IEEE 29-31 Oct. 2007 Page(s):1 - 5 </li></ul><ul><li>Tavangaran, N.; Wilzeck, A.; Kaiser, T., “MIMO SC-FDMA system performance for space time / frequency coding and spatial multiplexing” Smart Antennas, 2008. WSA 2008. International ITG Workshop on Volume , Issue , 26-27 Feb. 2008 Page(s):382 – 386 </li></ul><ul><li>Zijian Bai; Berkmann, J.; Spiegel, C.; Scholand, T.; Bruck, G.H.; Drewes, C.; Gunzelmann, B.; Jung, P.,   “On MIMO with successive interference cancellation applied to UTRA LTE” Communications, Control and Signal Processing, 2008. ISCCSP 2008. 3rd International Symposium on 12-14 March 2008 Page(s):1009 - 1013 </li></ul><ul><li>Ribeiro, C.B.; Hugl, K.; Lampinen, M.; Kuusela, M., “Performance of linear multi-user MIMO precoding in LTE system” Wireless Pervasive Computing, 2008. ISWPC 2008. 3rd International Symposium on 7-9 May 2008 Page(s):410 - 414 </li></ul><ul><li>LTE-Advanced takes an important step forward- http:// =AR_4623 </li></ul><ul><li>3GPP Presentation on the LTE-Advanced as an IMT-Advanced Technology Solution (RP-080756): </li></ul><ul><li>Progress on “LTE Advanced”- the new 4G standard – By Eiko Seidel, Nomor Research GmbH: </li></ul><ul><li>Parkvall, S.; Dahlman, E.; Furuskar, A.; Jading, Y.; Olsson, M.; Wanstedt, S.; Zangi, K., “LTE-Advanced – Evolving LTE towards IMT –Advanced” Vehicular Technology Conference, 2008. VTC 2008-Fall. IEEE 68th 21-24 Sept. 2008 Page(s):1 – 5. </li></ul><ul><li>Single Carrier FDMA – By Hyung G. Myung, May 18, 2008: </li></ul>
  102. 103. [email_address] Thank You !

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Long Term Evolution


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