3GPP LTE (Rel. 8) Overview

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3GPP LTE (Rel. 8) Overview

  1. 1. 3GPP R8 LTE Overview 조봉열, Bong Youl (Brian) Cho brian.cho@intel.com Intel Corporation
  2. 2. Contents Technology Evolution OFDM(A) and SC-FDMA LTE Overview LTE Radio Interface Architecture LTE Downlink Transmission LTE Uplink Transmission LTE Cell Search Summary LTE/MIMO 표준기술 2
  3. 3. Technology Evolution
  4. 4. Worldwide Mobile Users Number Percentage cdmaOne 2,512,409 0.06% CDMA2000 1X 309,507,900 7.18% CDMA2000 1xEV-DO 121,821,983 2.83% CDMA2000 1xEV-DO Rev. A 13,912,386 0.32% Subtotal for 3GPP2 447,754,678 10.39% GSM 3,449,010,903 80.02% WCDMA 255,773,412 5.93% WCDMA HSPA 132,079,727 3.06% TD-SCDMA 825,044 0.02% Subtotal for 3GPP 3,837,689,086 89.03% Subtotal for 3GPP except GSM 388,678,183 9.02% TDMA 753,411 0.02% PDC 2,752,436 0.06% iDEN 21,361,981 0.50% Total 4,310,311,592 * Data supplied by GSMA Mobile Infolink on Aug/07/2009 LTE/MIMO 표준기술 4
  5. 5. 3GPP Standards Evolution Ongoing GERAN Evolution GERAN GPRS EGPRS GERAN Evolution DL PDR: 50 kbps DL PDR: 236 kbps SAIC MSRD UL PDR: 21 kbps UL PDR: 118 kbps PS Handover Dual Carrier Ongoing UMTS R5 HSDPA R6 HSUPA R7 HSPA R8 HSPA HSPA Evolution WCDMA (5MHz) (5 MHz) Evolution Evolution (5MHz) DL PDR: 14 Mbps DL PDR: 14 Mbps (5 MHz) (5 MHz) DL PDR: 384 kbps UL PDR: 384 kbps UL PDR: 5.7 Mbps DL PDR: 28.8 Mbps DL PDR: 43.2 Mbps UL PDR: 64 kbps UL PDR: 11.5 Mbps UL PDR: 11.5 Mbps R7 LTE R8 LTE/SAE R9 & Feasibility LTE-Adv Study (1.4-20MHz) (1.4- (1.25-20MHz) (1.25- DL PDR: ≥ 100 Mbps (R10)… UL PDR: ≥ 50 Mbps 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009+ LTE/MIMO 표준기술 5
  6. 6. Technology Evolution Path 3G 3.5G~3.99G IMT-Adv? 2005 2006 2007-2009 2010+ 3G Technology Evolution HSPA+ (R7/R8) WCDMA (R99) HSDPA (R5) LTE-Adv ? 3GPP LTE (R8) EVDO R.B EVDO R.0 EVDO R.A ? 3GPP2 UMB Wi-Fi 802.16e 802.16e 802.16m ? OFDM OFDMA MIMO-OFDMA (WiMAX R2.0) (WiMAX R1.0) Broadband Wireless Technology Evolution LTE/MIMO 표준기술 6
  7. 7. Advancement For High Data Rate 3.5G 4G 2G, 3G (HSDPA,EVDO) (LTE,WiMAX) Access Scheme CDMA OFDM(A) QPSK,16QAM, Modulation QPSK Up to 16QAM 64QAM Link Adaptation Mainly PC Mainly AMC with channel-aware scheduler ARQ without soft ARQ HARQ with soft combining combining Handover SHO HHO FDD, Duplexing FDD TDD is emerging Antenna Various Antenna Rx Antenna Diversity Technology Diversity, MIMO, BF LTE/MIMO 표준기술 7
  8. 8. OFDM(A) and SC-FDMA
  9. 9. ISI Prevents High Data Rate? In general, ISI prevents “HIGH DATA RATE” Symbol rate increase Ts decrease severe ISI Symbol rate decrease Ts increase less ISI Multipath profile in the wireless channel (which is already given) time System#1 s1 s2 Ts System#2 s1 s2 s3 s4 s5 s6 s7 s8 s9 s10 s11 s12 s13 s14 s15 s16 Ts • System#2 achieves 10x higher data rate by using 10x more spectrum (BW) • However, at the same time, system#2 suffers 10x more severe ISI due to short symbol duration compared to the multipath profile in the time domain LTE/MIMO 표준기술 9
  10. 10. Multicarrier to “Minimize” ISI Effect Ways to “minimize” inter-symbol interference: Reduce the symbol rate, but data rate goes down too Equalizers, but equalization is processor intensive & expensive We are talking about “Broadband Wireless” which requires high data rate Solution: Transmit data over multiple carrier frequencies in parallel Narrow, slower channels are MUCH LESS vulnerable to ISI thanks to long symbol duration compared to the multipath delay in time domain OFDM splits data into parallel, independent, narrowband channels (“subcarriers”) Expensive adaptive equalizers are not required LTE/MIMO 표준기술 10
  11. 11. Guard Interval To “Remove” ISI LTE/MIMO 표준기술 11
  12. 12. Cyclic Prefix for Guard Interval LTE/MIMO 표준기술 12
  13. 13. More on CP (Cyclic Prefix) OFDM guarantee no interference ‘between’ subsequent OFDM symbols OFDM allows ISI ‘within’ one OFDM symbol Then, how can we remove ISI ‘within’ each OFDM symbol? LTE/MIMO 표준기술 13
  14. 14. Circular Convolution Circular convolution where is a periodic version of x[n] with period L. DFT The duality b/w circular convolution in the time domain and simple multiplication in the frequency domain is a property unique to DFT The above simple formula describes an ISI-free channel in the frequency domain, where each input symbol X[m] is simply scaled by a complex value H[m] It is trivial to recover the input symbol by simply computing LTE/MIMO 표준기술 14
  15. 15. Frequency Domain Model of OFDM Tx/Rx One-tap EQ LTE/MIMO 표준기술 15
  16. 16. OFDMA: (1) Better BW Utilization Cell center area: mostly BW-limited region Cell edge area: mostly power-limited region To better utilize the resource FDM-based access is required on top of TDM-based access Enhance uplink link budget! Active subcarriers are divided into subsets called “resource block” When subscriber uses very few resource blocks, It can concentrate all transmitting power (e.g. 200mW) in the used resource blocks It will have additional gain on uplink 10*log10(Fs), where Fs is the power concentration factor 200mW 200mW Total System BW LTE/MIMO 표준기술 16
  17. 17. OFDMA: (2) Freq. Domain Scheduling Loading gain by “frequency selective scheduling” Localized subcarrier assignment Distributed subcarrier assignment LTE/MIMO 표준기술 17
  18. 18. DL Channel Dependent Scheduling in time and frequency domains LTE/MIMO 표준기술 18
  19. 19. OFDMA: (3) Interference Coordination Flexible Fractional Frequency Reuse Cell-A Power A1 A2 A3 A4 A5 B1 B2 B3 B4 C1 C2 C3 C4 B5 C5 weak users good users A1 A2 A3 A4 A5 B2 B3 B4 B5 C1 C2 C3 C4 C5 Cell-B B1 good user weak user C1 C2 C3 C4 C5 Cell-C A1 A2 A3 A4 A5 B1 B2 B3 B4 B5 good users weak users LTE/MIMO 표준기술 19
  20. 20. A Brief History of OFDM* 1966: Chang shows that multicarrier modulation can solve the multipath problem without reducing data rate R. W. Chang, “Synthesis of band-limited orthogonal signals for multichannel data transmission”, Bell Systems Technical Journal, 45:1775-1796, Dec. 1966 1971: Weinstein and Ebert show that multicarrier modulation can be accomplished using a DFT S. Weinstein and P. Ebert, “Data Transmission by frequency-division multiplexing using the discrete Fourier transform”, IEEE Transactions on Communications, 19(5): 628-634, Oct. 1971 1985: Cimini at Bell Labs identifies many of the key issues in OFDM transmission and does a proof-of-concept design L. J. Cimini, “Analysis and simulation of a digital mobile channel using orthogonal frequency division multiplexing”, IEEE Transactions on Communications, 33(7): 665-675, July 1985 1993: DSL adopts OFDM 1999: IEEE 802.11 releases the 802.11a standard for OFDM LTE/MIMO 표준기술 * Jeffrey Andrews, et al., Fundamentals of WiMAX, Prentice Hall, 2007 20
  21. 21. OFDM in Communication Systems 3GPP LTE 3GPP2 UMB IEEE 802.16e Mobile WiMAX DAB, DVB-T, DVB-H T-DMB MediaFlo IEEE 802.11a WLAN xDSL PLC Etc… LTE/MIMO 표준기술 21
  22. 22. SC-FDMA Transmitter SC-FDMA is a new hybrid modulation technique combining the low PAR single carrier methods of current systems with the frequency allocation flexibility and long symbol time of OFDM SC-FDMA is sometimes referred to as Discrete Fourier Transform Spread OFDM = DFT-SOFDM Signal at each subcarrier is linear combination of all M symbols Coded symbol rate= R Spreading Sub-carrier CP DFT Mapping IFFT insertion Msymbols Size-M Low High Low Size-N PAPR PAPR PAPR LTE/MIMO 표준기술 22
  23. 23. CM of OFDMA & SC-FDMA OFDMA SC-FDMA 16QAM SC-FDMA QPSK SC-FDMA pi/2-BPSK LTE/MIMO 표준기술 23
  24. 24. R8 LTE DL OFDMA LTE/MIMO 표준기술 24
  25. 25. R8 LTE UL SC-FDMA (LFDMA) LTE/MIMO 표준기술 25
  26. 26. Comparing OFDM and SC-FDMA* QPSK example using N=4 subcarriers How OFDM and SC-FDMA would be used to transmit a sequence of 8 QPSK symbols LTE/MIMO 표준기술 26 * Moray Rumney (Agilent), “Concepts of 3GPP LTE”, Live Webinar, Sep. 20th, 2007.
  27. 27. Comparing OFDM and SC-FDMA LTE/MIMO 표준기술 27
  28. 28. Time Domain Equalizer In general, the complexity of time-discrete equalizer with linear equalization implementation (as above) grows relatively rapidly with the bandwidth of the signal to be equalized A more wideband signal is subject to relatively more frequency selectivity or, equivalently, more time dispersion. This implies the equalizer needs to have a larger span. A more wideband signal leads to a correspondingly higher sampling rate for the received signal. Thus, also the receiver-filter processing needs to be carried out with a correspondingly higher rate. LTE/MIMO 표준기술 28
  29. 29. Frequency Domain Equalizer Frequency domain equalization basically consists of A size-N DFT/FFT N complex multiplications (the frequency-domain filter) A size-N inverse DFT/FFT Especially in extensive frequency selective channel, the complexity of the frequency domain equalization can be significantly less than that of time domain equalization * D. Falconer, et al., “Frequency domain equalization for single-carrier broadband LTE/MIMO 표준기술 wireless systems,” IEEE Communication Magazine, vol.40, no.4, April 2002 29
  30. 30. LTE Overview
  31. 31. 3GPP Specifications LTE Study Phase (Release 7) TR 25.813, E-UTRA and E-UTRAN: Radio interface protocol aspects TR 25.814, Physical layer aspects for E-UTRA TR 25.912, Feasibility study for E-UTRA and E-UTRAN TR 25.913, Requirements for E-UTRA and E-UTRAN LTE Specifications (Release 8) TS 36.101, E-UTRA: UE radio transmission and reception TS 36.104, E-UTRA: BS radio transmission and reception TS 36.201, E-UTRA: LTE Physical Layer - General Description TS 36.211, E-UTRA: Physical channels and modulation TS 36.212, E-UTRA: Multiplexing and channel coding TS 36.213, E-UTRA: Physical layer procedures TS 36.214, E-UTRA: Physical layer – Measurements TS 36.300, E-UTRA and E-UTRAN: Overall description; Stage 2 TS 36.302, E-UTRA: Services provided by the physical layer TS 36.306, E-UTRA: UE Radio Access Capabilities TS 35.321, E-UTRA: Medium Access Control (MAC) protocol specification TS 36.323, E-UTRA: Packet Data Convergence Protocol (PDCP) specification TS 36.331, E-UTRA: Radio Resource Control (RRC); Protocol specification TS 36.401, E-UTRAN: Architecture description TR 36.938, E-UTRAN: Improved network controlled mobility between LTE and 3GPP2/mobile WiMAX radio technologies TR 36.956, E-UTRA; Repeater planning guidelines and system analysis LTE/MIMO 표준기술 31
  32. 32. 3GPP LTE LTE focus is on: enhancement of the Universal Terrestrial Radio Access (UTRA) optimisation of the UTRAN architecture With HSPA (downlink and uplink), UTRA will remain highly competitive for several years LTE project aims to ensure the continued competitiveness of the 3GPP technologies for the future (started at Nov. 2004) Motivations Need for PS optimized system Evolve UMTS towards packet only system Need for higher data rates Can be achieved with HSDPA/HSUPA and/or new air interface defined by 3GPP LTE Need for high quality of services Use of licensed frequencies to guarantee quality of services Always-on experience (reduce control plane latency significantly) Reduce round trip delay Need for cheaper infrastructure Simplify architecture, reduce number of network elements Most data users are less mobile LTE/MIMO 표준기술 32
  33. 33. Detailed Requirements* Peak data rate Instantaneous downlink peak data rate of 100 Mb/s within a 20 MHz downlink spectrum allocation (5 bps/Hz) Instantaneous uplink peak data rate of 50 Mb/s (2.5 bps/Hz) within a 20MHz uplink spectrum allocation) Control-plane latency Transition time of less than 100 ms from a camped state, such as Release 6 Idle Mode, to an active state such as Release 6 CELL_DCH Transition time of less than 50 ms between a dormant state such as Release 6 CELL_PCH and an active state such as Release 6 CELL_DCH Control-plane capacity At least 200 users per cell should be supported in the active state for spectrum allocations up to 5 MHz User-plane latency Less than 5 ms in unload condition (ie single user with single data stream) for small IP packet * 3GPP TR 25.913, Technical Specification Group RAN: Requirements for Evolved LTE/MIMO 표준기술 UTRA (E-UTRA) and Evolved UTRAN (E-UTRAN), Release 8, Version 8.0.0, Dec. 2008 33
  34. 34. Detailed Requirements Average user throughput Downlink: average user throughput per MHz, 3 to 4 times Release 6 HSDPA Uplink: average user throughput per MHz, 2 to 3 times Release 6 Enhanced Uplink Cell edge user throughput Downlink: user throughput per MHz at 5% of CDF, 2 to 3 times Release 6 HSDPA Uplink: user throughput per MHz at 5% of CDF, 2 to 3 times Release 6 Enhanced Uplink Spectrum efficiency Downlink: In a loaded network, target for spectrum efficiency (bits/sec/Hz/site), 3 to 4 times Release 6 HSDPA ) Uplink: In a loaded network, target for spectrum efficiency (bits/sec/Hz/site), 2 to 3 times Release 6 Enhanced Uplink Mobility E-UTRAN should be optimized for low mobile speed from 0 to 15 km/h Higher mobile speed between 15 and 120 km/h should be supported with high performance Mobility across the cellular network shall be maintained at speeds from 120 km/h to 350 km/h (or even up to 500 km/h depending on the frequency band) Coverage Throughput, spectrum efficiency and mobility targets above should be met up to 5 km cells, and with a slight degradation up to 30 km cells. Cells range up to 100 km should not be precluded. LTE/MIMO 표준기술 34
  35. 35. Detailed Requirements Spectrum flexibility E-UTRA shall operate in spectrum allocations of different sizes, including 1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz in both the uplink and downlink. Operation in paired and unpaired spectrum shall be supported Co-existence and Inter-working with 3GPP RAT (UTRAN, GERAN) Architecture and migration Single E-UTRAN architecture The E-UTRAN architecture shall be packet based, although provision should be made to support systems supporting real-time and conversational class traffic E-UTRAN architecture shall support an end-to-end QoS Backhaul communication protocols should be optimized Radio Resource Management requirements Enhanced support for end to end QoS Support of load sharing and policy management across different Radio Access Technologies Complexity Minimize the number of options No redundant mandatory features LTE/MIMO 표준기술 35
  36. 36. LTE System Performance Peak Data Rate 150.8 baseline 302.8 51.0 75.4 baseline LTE/MIMO 표준기술 36
  37. 37. LTE System Performance – cont’d Downlink Spectral Efficiency Uplink Spectral Efficiency LTE/MIMO 표준기술 37
  38. 38. LTE Key Features Downlink: OFDMA (Orthogonal Frequency Division Multiple Access) Less critical AMP efficiency in BS side Making MS cheap as Concerns on high RX complexity in terminal side much as possible by Uplink: SC-FDMA (Single Carrier-FDMA) moving all the burdens Less critical RX complexity in BS side from MS to BS Critical AMP complexity in terminal side (Cost, power Consumption, UL coverage) Single node RAN (eNB) Support FDD (frame type 1) & TDD (frame type 2 for TD-SCDMA) <cf> H-FDD MS User data rates DL (baseline): 150.8 Mbps @ 20 MHz BW w/ 2x2 SU-MIMO UL (baseline): 75.4 Mbps @ 20 MHz BW w/ non-MIMO or 1x2 MU-MIMO Radio frame: 10 ms (= 20 slots) Sub-frame: 1 ms (= 2 slots) Slot: 0.5 ms TTI: 1 ms HARQ Incremental redundancy is used as the soft combining strategy Retransmission time: 8 ms Modulation DL/UL data channel = QPSK/16QAM/64QAM LTE/MIMO 표준기술 38
  39. 39. LTE Key Features – cont’d MIMO SM (Spatial Multiplexing), Beamforming, Antenna Diversity Min requirement: 2 eNB antennas & 2 UE rx antennas DL: Single-User MIMO up to 4x4 supportable UL: 1x2 MU-MIMO, Optional 2x2 SU-MIMO Resource block 12 subcarriers with subcarrier BW of 15kHz “180kHz” 24 subcarriers with subcarrier BW of 7.5kHz (only for MBMS) Subcarrier operation Frequency selective by localized subcarrier Frequency diversity by distributed subcarrier & frequency hopping Frequency hopping Intra-TTI: UL (once per 0.5ms slot), DL (once per 66us symbol) Inter-TTI: across retransmissions Bearer services Packet only – no circuit switched voice or data services are supported Voice must use VoIP MBSFN Multicast/Broadcast over a Single Frequency Network To support a Multimedia Broadcast and Multicast System (MBMS) Time-synchronized common waveform is transmitted from multiple cells for a given duration The signal at MS will appear exactly as a signal transmitted from a single cell site and subject to multi-path Not only “improve the received signal strength” but also “eliminate inter-cell interference” LTE/MIMO 표준기술 39
  40. 40. E-UTRAN Architecture* LTE/MIMO 표준기술 * 3GPP TS 36.300, E-UTRA and E-UTRAN; Overall description; Stage 2, Release 9, V9.0.0, June 2009 40
  41. 41. Functional Split b/w E-UTRAN and EPC* LTE/MIMO 표준기술 * 3GPP TS 36.300, E-UTRA and E-UTRAN; Overall description; Stage 2, Release 9, V9.0.0, June 2009 41
  42. 42. 3GPP Architecture Evolution Towards Flat Architecture LTE/MIMO 표준기술 42
  43. 43. E-UTRA Frequency Band* Japan, Korea? Korea? Europe Korea? US US China? * 3GPP TS 36.101, E-UTRA: UE radio transmission LTE/MIMO 표준기술 and reception, Release 9, V9.0.0, June 2009 43
  44. 44. E-UTRA Channel Bandwidth* 1RB = 180kHz 6RBs = 1.08MHz, 100RBs = 18MHz 6RBs (72 subcarriers) with 128 FFT, 100RBs (1200 subcarriers) with 2048 FFT * 3GPP TS 36.101, E-UTRA: UE radio transmission LTE/MIMO 표준기술 and reception, Release 9, V9.0.0, June 2009 44
  45. 45. TS 36.101 for UE, 36.104 for eNB Transmitter characteristics Transmit power Output power dynamics Transmit signal quality Output RF spectrum emissions Transmit intermodulation Receiver characteristics Reference sensitivity power level Maximum input level Adjacent Channel Selectivity (ACS) Blocking characteristics Intermodulation characteristics Spurious emissions Performance requirement (below is examples for UE) Dual-antenna receiver capability Simultaneous unicast and MBMS operations Demodulation of PDSCH (Cell-Specific Reference Symbols) Minimum Requirement QPSK/16QAM/64QAM Transmit diversity performance Open-loop spatial multiplexing performance Closed-loop spatial multiplexing performance MU-MIMO LTE/MIMO 표준기술 45
  46. 46. Conformance Test TS 36.141 Evolved Universal Terrestrial Radio Access (E-UTRA); Base Station (BS) conformance testing TS 36.143 Evolved Universal Terrestrial Radio Access (E-UTRA); FDD repeater conformance testing TS 36.508 Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Packet Core (EPC); Common test environments for User Equipment (UE) conformance testing TS 36.509 Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Packet Core (EPC); Special conformance testing functions for User Equipment (UE) TS 36.521-1 Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) conformance specification; Radio transmission and reception; Part 1: Conformance testing TS 36.521-2 Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) conformance specification; Radio transmission and reception; Part 2: Implementation Conformance Statement (ICS) TS 36.521-3 Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) conformance specification; Radio transmission and reception; Part 3: Radio Resource Management (RRM) conformance testing TS 36.523-1 Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Packet Core (EPC); User Equipment (UE) conformance specification; Part 1: Protocol conformance specification TS 36.523-2 Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Packet Core (EPC); User Equipment (UE) conformance specification; Part 2: ICS TS 36.523-3 Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Packet Core (EPC); User Equipment (UE) conformance specification; Part 3: Test suites LTE/MIMO 표준기술 46
  47. 47. LTE Radio Interface Architecture
  48. 48. LTE Protocol Architecture (DL) LTE/MIMO 표준기술 48
  49. 49. Logical Channels: “type of information it carries” Control Channels Broadcast Control Channel (BCCH) used for transmission of system information from the network to all UEs in a cell Paging Control Channel (PCCH) used for paging of UEs whose location on cell level is not known to the network Common Control Channel (CCCH) used for transmission of control information in conjunction with random access, i.e., used for UEs having no RRC connection Dedicated Control Channel (DCCH) used for transmission of control information to/from a UE, i.e., used for UEs having RRC connection (e.g. handover messages) Multicast Control Channel (MCCH) used for transmission of control information required for reception of MTCH Traffic Channels Dedicated Traffic Channel (DTCH) used for transmission of user data to/from a UE Multicast Traffic Channel (MTCH) used for transmission of MBMS services * 3GPP TS 36.300, E-UTRA and E-UTRAN; Overall LTE/MIMO 표준기술 description; Stage 2, Release 9, V9.0.0, June 2009 49
  50. 50. Transport Channels: “how”, “with what characteristics” Downlink Broadcast Channel (BCH) A fixed TF Used for transmission of parts of BCCH, so called MIB Paging Channel (PCH) Used for transmission of paging information from PCCH Supports discontinuous reception (DRX) Downlink Shared Channel (DL-SCH) Main transport channel used for transmission of downlink data in LTE Used also for transmission of parts of BCCH, so called SIB Supports discontinuous reception (DRX) Multicast Channel (MCH) Used to support MBMS Uplink Uplink Shared Channel (UL-SCH) Uplink counterpart to the DL-SCH Random Access Channel(s) (RACH) Transport channel which doesn’t carry transport blocks Collision risk * 3GPP TS 36.300, E-UTRA and E-UTRAN; Overall LTE/MIMO 표준기술 description; Stage 2, Release 9, V9.0.0, June 2009 50
  51. 51. DL Physical Channels Physical Downlink Shared Channel (PDSCH) 실제 downlink user data를 전송하기 위한 transport channel인 DL-SCH와 paging 정보를 전송 하기 위한 transport channel인 PCH가 매핑 동적 방송 정보인 SI (System Information) 값들도 RRC 메시지 형태로 DL-SCH를 통해 전송되 므로 이 역시 PDSCH로 매핑 이 경우는 전체 셀 영역으로 도달될 수 있는 능력이 요구되기도 함 Physical Broadcast Channel (PBCH) UE가 cell search과정을 마친 후에 최초로 검출하는 채널로서, 다른 물리 계층 채널들을 수신하 기 위하여 반드시 필요한 기본적인 시스템 정보들인 MIB (Master Information Block)를 전송하 기 위한 transport channel인 BCH가 매핑 Physical Multicast Channel (PMCH) 방송형 데이터를 전송하기 위한 transport channel 인 MCH가 매핑 Physical Control Format Indicator Channel (PCFICH) 매 subframe마다 전송, only one PCFICH in each cell Informs UE about CFI which indicates the number of OFDM symbols used for PDCCHs transmission Physical Downlink Control Channel (PDCCH) Informs UE about resource allocation of PCH and DL-SCH HARQ information related to DL-SCH UL scheduling grant Physical HARQ Indicator Channel (PHICH) Carries HARQ ACK/NACKs in response to UL transmission LTE/MIMO 표준기술 51
  52. 52. UL Physical Channels Physical Uplink Shared Channel (PUSCH) Uplink counterpart of PDSCH Carries UL-SCH Physical Uplink Control Channel (PUCCH) Carries HARQ ACK/NAKs in response to DL transmission Carries Scheduling Request (SR) Carries channel status reports such as CQI, PMI and RI At most one PUCCH per UE Physical Random Access Channel (PRACH) Carries the random access preamble LTE/MIMO 표준기술 52
  53. 53. LTE Channel Mapping Downlink Uplink LTE/MIMO 표준기술 53
  54. 54. Terminal States RRC_CONNECTED Active state where UE is connected to a specific cell One or several IP addresses as well as an identity of the terminal, Cell Radio-Network Temporary Identifier (C-RNTI), used for signaling purposes b/w UE and network, have been assigned Two substates: IN_SYNC & OUT_OF_SYNC whether or not uplink is synchronized to the network RRC_IDLE Low activity state where US sleeps most of the time to reduce battery consumption Uplink synchronization is not maintained and hence only uplink transmission that may take place is random access In downlink, US can periodically wake up to be paged for incoming calls UE keeps its IP address(es) and other internal info to rapidly move to RRC_CONNECTED LTE/MIMO 표준기술 54
  55. 55. Example of LTE Data Flow LTE/MIMO 표준기술 55
  56. 56. LTE Downlink Transmission
  57. 57. Frame Structure: Type 1 for FDD One radio frame, Tf = 307200×Ts=10 ms One slot, Tslot = 15360×Ts = 0.5 ms #0 #1 #2 #3 #18 #19 One subframe where, Ts = 1/(15000 x 2048) seconds “the smallest time unit in LTE” Tf = 307200 x Ts = 10 ms LTE/MIMO 표준기술 57
  58. 58. Frame Structure: Type 2 for TDD LTE/MIMO 표준기술 58
  59. 59. Frame Structure: FDD/TDD LTE/MIMO 표준기술 59
  60. 60. DL Slot Structure Tslot DL N RB : Downlink bandwidth configuration, RB expressed in units of N sc DL N symb RB N sc : Resource block size in the k = N RB N sc − 1 DL RB frequency domain, expressed as a number of subcarriers N symb × N sc DL RB DL N symb: Number of OFDM symbols in an downlink slot (k , l ) RB N RB × N sc RB N sc DL The minimum RB the eNB uses for LTE scheduling is “1ms (1subframe) x 180kHz (12subcarriers @ 15kHz spacing)” k =0 LTE/MIMO 표준기술 60 l=0 l= DL N symb −1
  61. 61. Definitions Resource Grid DL RB DL Defined as N RB N sc subcarriers in frequency domain and N symb OFDM symbols in time domain DL The quantity N RB depends on the DL transmission BW configured in the cell and shall fulfill 6 ≤ N RB ≤ 110 DL DL The set of allowed values for N RB is given by TS 36.101, TS 36.104 Resource Block (1 RB = 180 kHz) Defined as N sc “consecutive” subcarriers in frequency domain and N symb “consecutive” OFDM RB DL symbols in time domain Corresponding to one slot in the time domain and 180 kHz in the frequency domain Resource Element Uniquely defined by the index pair (k, l ) in a slot where k = 0,..., N RB N sc − 1 and l = 0,..., N symb − 1 DL RB DL are the indices in the frequency and time domain, respectively LTE/MIMO 표준기술 61
  62. 62. Normal CP & Extended CP LTE/MIMO 표준기술 62
  63. 63. PRB and VRB (LVRB, DVRB) Physical resource blocks are numbered from 0 to N RB − 1 in the frequency domain. DL The relation between the physical resource block number nPRB in the frequency domain and resource elements (k , l ) in a slot is given by ⎢ k ⎥ nPRB = ⎢ RB ⎥ ⎢ N sc ⎥ ⎣ ⎦ A virtual resource block is of the same size as a physical resource block. Two types of virtual resource blocks are defined: LVRB and DVRB Virtual resource blocks of localized type are mapped directly to PRBs such that virtual resource block nVRB corresponds to physical resource block nPRB = nVRB . Virtual resource blocks are numbered from 0 to N VRB − 1 , where N VRB = N RB . DL DL DL LTE/MIMO 표준기술 63
  64. 64. DVRB Virtual resource blocks of distributed type are mapped to PRBs as follows Consecutive VRBs are not mapped to PRBs that are consecutive in the frequency domain Even a single VRB pair is distributed in the frequency domain The exact size of the frequency gap depends on the overall downlink cell BW LTE/MIMO 표준기술 64
  65. 65. Resource-element groups (REG) n+5 n+6 n+7 Basic unit for mapping of PCFICH, PHICH, and PDCCH Resource-element groups are used for defining the mapping of control n+3 n+4 channels to resource elements. Mapping of a symbol-quadruplet n+0 n+1 n+2 z (i), z (i + 1), z (i + 2), z (i + 3) onto a resource -element group is defined such that elements z (i) are mapped to resource elements (k , l ) of the resource-element n+5 n+4 n+6 group not used for cell-specific reference signals in increasing order of l and k n+3 n+0 n+1 n+2 LTE/MIMO 표준기술 65
  66. 66. DL Physical Channel Processing code words layers antenna ports Modulation Resource OFDM signal Scrambling element mapper Mapper generation Layer Precoding Mapper Modulation Resource OFDM signal Scrambling element mapper Mapper generation scrambling of coded bits in each of the code words to be transmitted on a physical channel modulation of scrambled bits to generate complex-valued modulation symbols mapping of the complex-valued modulation symbols onto one or several transmission layers precoding of the complex-valued modulation symbols on each layer for transmission on the antenna ports mapping of complex-valued modulation symbols for each antenna port to resource elements generation of complex-valued time-domain OFDM signal for each antenna port LTE/MIMO 표준기술 66
  67. 67. Channel Coding Turbo code PCCC (exactly the same as in WCDMA/HSPA) QPP (quadratic polynomial permutation) interleaver LTE/MIMO 표준기술 67
  68. 68. Modulation LTE/MIMO 표준기술 68
  69. 69. DL Layer Mapping and Precoding Explained in MIMO session LTE/MIMO 표준기술 69
  70. 70. DL OFDM Signal Generation OFDM Parameters 0 ≤ t < (N CP ,l + N )× Ts N = 2048 for ∆f=15kHz N = 4096 for ∆f=7.5kHz Check with resource block parameters (160+2048) x Ts = 71.88us (144+2048) x Ts = 71.35us 71.88us + 71.35us x 6 = 0.5ms Normal Cyclic Prefix = 160 Ts = 5.2 us Normal Cyclic Prefix = 144 Ts = 4.7 us Extended Cyclic Prefix = 512 Ts = 16.7 us Extended Cyclic Prefix for MBMS = 1024 Ts = 33.3 us LTE/MIMO 표준기술 70
  71. 71. DL Physical Channels & Signals Physical channels Physical Downlink Shared Channel (PDSCH) Physical Broadcast Channel (PBCH) Physical Multicast Channel (PMCH) Physical Control Format Indicator Channel (PCFICH) Physical Downlink Control Channel (PDCCH) Physical HARQ Indicator Channel (PHICH) Physical signals Reference Signals Cell-specific RS, associated with non-MBSFN transmission Aid coherent detection (pilot) Reference channel for CQI from UE to eNB MBSFN RS, associated with MBSFN transmission UE-specific RS Synchronization Signals Carries frequency and symbol timing synchronization PSS (Primary SS) and SSS (Secondary SS) LTE/MIMO 표준기술 71
  72. 72. DL Reference Signals Cell-specific reference signals Are transmitted in every downlink subframe, and span entire cell BW Can be used for coherent demodulation of any downlink transmission “except” when so-called non-codebook-based beamforming is used Using antenna ports {0, 1, 2, 3} MBSFN reference signals Are used for channel estimation for coherent demodulation of signals being transmitted by means of MBSFN Using antenna port 4 UE-specific reference signals Is specifically intended for channel estimation for coherent demodulation of DL-SCH when non-codebook-based beamforming is used. Are transmitted only within the RB assigned for DL-SCH to that specific UE Using antenna port 5 LTE/MIMO 표준기술 72
  73. 73. Cell-Specific Reference Signals When estimating the channel for a certain RB, UE may not only use the reference symbols within that RB but also, in frequency domain, neighbor RBs, as well as reference symbols of previously received slots/subframes Pseudo-random sequence generation rl ,ns (m) = 1 (1 − 2 ⋅ c(2m)) + j 1 (1 − 2 ⋅ c(2m + 1)), m = 0,1,...,2 N RB DL − 1 max, 2 2 is the slot number within a radio frame. is the OFDM symbol number within the slot. The pseudo-random sequence c(i) is a length-31 Gold sequence. The complex values of reference symbols will vary b/w different reference- symbol position and also b/w different cells. Thus, RS of a cell can be seen as a cell-specific two-dimensional sequence with the period of one frame. Regardless of cell BW, the reference signal sequence is defined assuming the maximum possible LTE cell BW corresponding to 110 RBs in frequency domain LTE/MIMO 표준기술 73
  74. 74. Relationship with Cell Identity 504 unique Cell ID: 168(N1) Cell ID groups, 3 (N2) Cell ID within each group Cell ID = 3xN1+N2 = 0 ~ 503 index 504 pseudo-random sequences One to one mapping between the Cell ID and Pseudo-random sequences Cell-specific Frequency Shift (N1 mod 6) 1 RE shift from current RS position in case of next Cell ID index Each shift corresponds to 84 different cell identities, that is 6 shifts jointly cover all 504 cell identities. Effective with RS boosting to enhance reference signal SIR by avoiding the collision of boosted RSs from neighboring cells (assuming time synchronization) LTE/MIMO 표준기술 74
  75. 75. Cell-Specific RS Mapping R0 R0 One antenna port R0 R0 R0 R0 R0 R0 l=0 l =6 l=0 l=6 Resource element (k,l) R0 R0 R1 R1 Two antenna ports R0 R0 R1 R1 Not used for transmission on this antenan port R0 R0 R1 R1 Reference symbols on this antenna port R0 R0 R1 R1 l =0 l=6 l =0 l =6 l =0 l =6 l =0 l =6 R0 R0 R1 R1 R2 R3 R3 Four antenna ports R0 R0 R1 R1 R2 R0 R0 R1 R1 R2 R3 R3 R0 R0 R1 R1 R2 l =0 l =6 l =0 l =6 l=0 l =6 l=0 l=6 l=0 l =6 l=0 l=6 l =0 l=6 l =0 l=6 LTE/MIMO 표준기술 even-numbered slots odd-numbered slots even-numbered slots odd-numbered slots even-numbered slots odd-numbered slots even-numbered slots odd-numbered slots 75 Antenna port 0 Antenna port 1 Antenna port 2 Antenna port 3
  76. 76. MBSFN RS Mapping LTE/MIMO 표준기술 76
  77. 77. MBSFN RS Mapping LTE/MIMO 표준기술 77
  78. 78. UE-specific RS on top of Cell-specific RS UE-specific RS (antenna port 5) 12 symbols per RB pair DL CQI estimation is always based on cell-specific RS (common RS) LTE/MIMO 표준기술 78
  79. 79. PCFICH The number of OFDM symbols used for control channel can be varying per TTI CFI (Control Format Indication) Information about the number of OFDM symbols (1~4) used for transmission of PDCCHs in a subframe PCFICH carries CFI 2 bits 32 bits (block coding) 32 bits (cell specific scrambling) 16 symbols (QPSK) Mapping to resource elements: 4 REG (16 RE excluding RS) in the 1st OFDM symbol Spread over the whole system bandwidth To avoid the collisions in neighboring cells, the location depends on cell identity Transmit diversity is applied which is identical to the scheme applied to BCH LTE/MIMO 표준기술 79
  80. 80. PCFICH REG Mapping Cell ID Example for 5 MHz BW LTE DL N RB = 25 (number of REGs = 50) RB N sc = 12 REG LTE/MIMO 표준기술 80
  81. 81. PCFICH Processing LTE/MIMO 표준기술 81
  82. 82. PHICH HARQ ACK/NAK in response to UL transmission HI codewords with length of 12 REs = 4 (Walsh spreading) x 3 (repetition) 3 groups of 4 contiguous REs (not used for RS and PCFICH) BPSK modulation with I/Q multiplexing SF4 x 2 (I/Q) = 8 PHICHs in normal CP Cell-specific scrambling Tx diversity, the same antenna ports as PBCH Typically, PHICH is transmitted in the first OFDM symbol only For FDD, an uplink transport block received in subframe n should be acknowledged on the PHICH in subframe n+4 LTE/MIMO 표준기술 82
  83. 83. PHICH REG Mapping Cell ID ⎧ ⎪ (⎣N cell ID ⎦ ) ⋅ nli′ n1 + m' mod nli′ i=0 ⎪ ni = ⎨ (⎣N cell ID ⋅ nli′ n1 ⎦ + m'+ ⎣nl ′ 3⎦)mod nl ′ i i i =1 ⎪ ⎪ ⎩ (⎣N cell ID ⋅ nli′ n1 ⎦ + m'+ ⎣2 nl ′ 3⎦)mod nl ′ i i i=2 DL N RB Example for 5 MHz BW LTE DL N RB = 25 (number of REGs = 50) RB N sc = 12 REG LTE/MIMO 표준기술 83
  84. 84. PHICH Processing LTE/MIMO 표준기술 84
  85. 85. symbol PCFICH/PHICH RE Mapping Example for 5 MHz BW LTE LTE/MIMO 표준기술 Subcarrier 85
  86. 86. PDCCH DCI Format PDCCH is used to carry DCI where DCI includes; Downlink scheduling assignments, including PDSCH resource indication, transport format, HARQ- related information, and control information related to SM (if applicable). Uplink scheduling grants, including PUSCH resource indication, transport format, and HARQ- related information. Uplink power control commands DCI Usage Details Formats 0 UL grant For scheduling of PUSCH 1 For scheduling of one PDSCH codeword (SIMO, TxD) For compact scheduling of one PDSCH codeword (SIMO, TxD) and random access procedure 1A initiated by a PDCCH order 1B For compact scheduling of one PDSCH codeword with precoding information (CL single-rank) DL For very compact scheduling of one PDSCH codeword (paging, RACH response and dynamic 1C assignment BCCH scheduling) 1D For compact scheduling of one PDSCH codeword with precoding & power offset information 2 For scheduling PDSCH to UEs configured in CL SM 2A For scheduling PDSCH to UEs configured in OL SM 3 Power For transmission of TPC commands for PUCCH/PUSCH with 2-bit power adjustment 3A control For transmission of TPC commands for PUCCH/PUSCH with single bit power adjustment LTE/MIMO 표준기술 86
  87. 87. Downlink Assignment Major contents of different DCI formats: not exhaustive DCI format 0/1A indication [1 bit] Distributed transmission flag [1 bit] Resource-block allocation [variable] For the first (or only) transport block MCS [5 bit] New-data indicator [1 bit] Redundancy version [2 bit] For the second transport block (present in DCI format 2 only) MCS [5 bit] New-data indicator [1 bit] Redundancy version [2 bit] HARQ process number [3 bit for FDD] Information related to SM (present in DCI format 2 only) Pre-coding information [3 bit for 2 antennas, 6 bit for 4 antennas in CL-SM] Number of transmission layer HARQ swap flag [1 bit] Transmit power control (TPC) for PUCCH [2 bit] Identity (RNTI) of the terminal for which the PDCCH transmission is intended [16 bit] LTE/MIMO 표준기술 87
  88. 88. Uplink Grants Major contents of DCI format 0 for UL grants: not exhaustive DCI format 0/1A indication [1 bit] Hopping flag [1 bit] Resource-block allocation [variable] MCS [5 bit] New-data indicator [1 bit] Phase rotation of UL demodulation reference signal [3 bit] Channel-status request flag [1 bit] Transmit power control (TPC) for PUSCH [2 bit] Identity (RNTI) of the terminal for which the PDCCH transmission is intended [16 bit] The time b/w reception of an UL scheduling grant on a PDCCH and the corresponding transmission on UL-SCH are fixed For FDD, the time relation is the same as for PHICH Uplink grant received in downlink subframe n applies to uplink subframe n+4 LTE/MIMO 표준기술 88
  89. 89. PDCCH Processing First n OFDM symbols < 10RB: 2~4 OFDMA symbols > 10RB: 1~3 OFDMA symbols 1/14~3/14 (10~20%) overhead PDCCH format based on # of CCE (Control Channel Element, = 9 REGs) Depending on the payload size of control information (DCI payload) & coding rate Number of CCEs for each of PDCCH may vary and is not signaled, so UE has to blindly determine this search space: a set of candidate control channels formed by CCEs on a given aggregation level {1, 2, 4, 8}, which UE is supposed to attempt to decode User identification is based on “UE specific CRC (normal CRC with UE ID masking)” Cell-specific scrambling, QPSK with tail-biting Conv. Code Tx diversity, the same antenna ports as PBCH Mapped to REG not assigned to PCFICH or PHICH LTE/MIMO 표준기술 89
  90. 90. PDCCH Processing LTE/MIMO 표준기술 90
  91. 91. System Information Master information block (MIB) includes the following information: Downlink cell bandwidth [4 bit] PHICH duration [1 bit] PHICH resource [2 bit] System Frame Number (SFN) except two LBSs Etc… LTE defines different SIBs: SIB1 includes info mainly related to whether an UE is allowed to camp on the cell. This includes info about the operator(s) and about the cell (e.g. PLMN identity list, tracking area code, cell identity, minimum required Rx level in the cell, etc), DL-UL subframe configuration in TDD case, and the scheduling of the remaining SIBs. SIB1 is transmitted every 80ms. SIB2 includes info that UEs need in order to be able to access the cell. This includes info about the UL cell BW, random access parameters, and UL power control parameters. SIBs also includes radio resource configuration of common channels (RACH, BCCH, PCCH, PRACH, PDSCH, PUSCH, PUCCH, and SRS). SIB3 mainly includes info related to cell-reselection. SIB4-8 include neighbor-cell-related info. (E-UTRAN, UTRAN, GERAN, cdma2000) SIB9 contains a home eNB identifier SIB10/11 contains ETWS (Earthquake and Tsunami Warning System) notification More to be added MIB mapped to PBCH Other SIBs mapped to PDSCH LTE/MIMO 표준기술 91
  92. 92. BCH on PBCH To broadcast a certain set of cell and/or system-specific information Requirement to be broadcast in the entire coverage area of the cell BCH transmission The coded BCH transport block is mapped to four subframes (slot #1 in subframe #0) within a 40ms interval 40ms timing is blindly detected (no explicit signaling indicating 40ms timing) Each subframe is assumed to be self-decodable, i.e. the BCH can be decoded from a single reception, assuming sufficiently good channel conditions LTE/MIMO 표준기술 92
  93. 93. BCH on PBCH – cont’d Single (fixed-size) transport block per TTI (40 ms) No HARQ Cell-specific scrambling, BPSK with ½ tail-biting Conv. Code, Tx diversity(1,2,4) BCH mapped to 4 OFDM symbols within a subframe in time-domain at 6 RBs (72 subcarriers) excluding DC in freq-domain PBCH is mapped into RE assuming RS from 4 antennas are used at eNB, irrespective of the actual number of TX antenna Different transmit diversity schemes per # of antennas # of ant=2: SFBC # of ant=4: SFBC + FSTD (Frequency Switching Transmit Diversity) No explicit bits in the PBCH to signal the number of TX antennas at eNB PBCH encoding chain includes CRC masking dependent on the number of configured TX antennas at eNB Blind detection of the number of TX antenna using CRC masking by UE LTE/MIMO 표준기술 93
  94. 94. PBCH Processing LTE/MIMO 표준기술 94
  95. 95. PDSCH Processing 1) RS 2) PSS & SSS and BCH 3) PCFICH 4) PHICH 5) PDCCH 6) PDSCH LTE/MIMO 표준기술 95
  96. 96. DL constellation & frame summary LTE/MIMO 표준기술 96
  97. 97. LTE Uplink Transmission
  98. 98. LTE Uplink Key Features SC-FDMA 사용 단말의 PAPR을 낮추어 커버리지를 증가시키기에 적합함 DFT size is limited to products of the integers 2, 3, and 5 (e.g. DFT sizes of 60, 72, and 96 are allowed but a DFT size of 84 is not allowed.) No unused DC-subcarrier is defined CAZAC (Constant Amplitude Zero Autocorrelation) sequence 사용 Reference signal 및 제어 정보 채널 전송 시 각 단말들의 신호를 구분하기 위하여 CDM 을 수행하는 경우 CAZAC sequence를 주로 사용 CAZAC sequence는 시간/주파수 차원에서 일정한 amplitude를 유지하는 특성을 가지 므로 단말의 PAPR을 낮추어 커버리지를 증가시키기에 적합함 MU-MIMO 지원 QPSK/16QAM/64QAM modulation 지원 LTE/MIMO 표준기술 98
  99. 99. UL Slot Structure Tslot UL N RB : Uplink bandwidth configuration, RB expressed in units of N sc UL N symb RB N sc : Resource block size in the k = N RB N sc − 1 UL RB frequency domain, expressed as a number of subcarriers N symb × N sc UL RB UL N symb : Number of SC-FDMA symbols in an uplink slot (k , l ) RB N RB × N sc RB N sc UL k =0 LTE/MIMO 표준기술 99 l=0 l= UL N symb −1
  100. 100. Definitions Resource Grid UL RB UL Defined as N RB N sc subcarriers in frequency domain and N symb SC-FDMA symbols in time domain UL The quantity N RB depends on the UL transmission BW configured in the cell and shall fulfill 6 ≤ N RB ≤ 110 UL UL The set of allowed values for N RB is given by TS 36.101, TS 36.104 Resource Block Defined as N sc “consecutive” subcarriers in frequency domain and N symb “consecutive” SC- RB UL FDMA symbols in time domain Corresponding to one slot in the time domain and 180 kHz in the frequency domain Resource Element Uniquely defined by the index pair (k, l ) in a slot where k = 0,..., N RB N sc − 1 and UL RB l = 0,..., N symb − 1 UL are the indices in the frequency and time domain, respectively LTE/MIMO 표준기술 100
  101. 101. UL Physical Channels & Signals UL physical channels Physical Uplink Shared Channel (PUSCH) Physical Uplink Control Channel (PUCCH) Physical Random Access Channel (PRACH) UL physical signals An uplink physical signal is used by the physical layer but does not carry information originating from higher layers Two types of reference signals UL demodulation reference signal (DRS) for PUSCH, PUCCH UL sounding reference signal (SRS) not associated with PUSCH, PUCCH transmission LTE/MIMO 표준기술 101
  102. 102. UL Reference Signals UL RS should preferably have the following properties: Favorable auto- and cross-correlation properties Limited power variation in freq-domain to allow for similar channel-estimation quality for all frequencies Limited power variation in time-domain (low cubic metric) for high PA efficiency Sufficiently many RS sequences of the same length to avoid an unreasonable planning effort Zadoff-Chu Sequence Appeared in IEEE Trans. Inform. Theory in 1972 Poly-phase sequence Constant amplitude zero auto correlation (CAZAC) sequence의 일종 Cyclic autocorrelations are zero for all non-zero lags, Non-zero cross-correlations Constant power in both the frequency and the time domain No restriction on code length N π ⎧ − j 2N pn 2 ⎪ e , when N is even g p ( n) = ⎨ 2π ⎪ e − j N pn ( n +1) , when N is odd ⎩ - Sequence number p is relatively prime to N - Sequence length: N - Number of sequences: N-1 LTE/MIMO 표준기술 102
  103. 103. DRS DRS is made from Z-C sequence*, and the DRS sequence length is the same with the number of subcarriers in an assigned RBs DRS is defined with the following parameters Sequence group (30 options): cell specific parameter Sequence (2 options for sequence lengths of 6PRBs or longer): cell specific parameter Cyclic shift (12 options): both terminal and cell specific components Sequence length: given by the UL allocation Typically, Cyclic shifts are used to multiplex RSs from different UEs within a cell. Different sequence groups are used in neighboring cells. LTE/MIMO 표준기술 103
  104. 104. DRS Location within a Subframe DM RS for PUSCH Normal CP 적용 시 PUSCH RS는 한 슬롯 당 중앙의 SC-FDMA 심볼에 위치 Extended CP 적용 시 PUSCH RS는 한 슬롯 당 3번째 SC-FDMA 심볼에 위치 DM RS for PUCCH Format 1x Format 2x LTE/MIMO 표준기술 104
  105. 105. SRS 기지국이 각 단말의 상향링크 채널 정보를 추정할 수 있도록 단말이 전송하는 RS Reference for channel quality information CQ measurement for frequency/time aware scheduling CQ measurement for link adaptation CQ measurement for power control CQ measurement for MIMO Timing measurement Reference signal sequence is defined by a cyclic shift of a base sequence (ZC) r SRS (n ) = ru(,α ) (n ) v ru(,α ) (n) = e jαn ru ,v (n), 0 ≤ n < M sc v RS SRS 전송주기/대역폭은 각 단말마다 고유하게 할당 From as often as once in every 2ms to as infrequently as once in every 160ms (320ms) At least 4 RBs SRS는 서브프레임의 마지막 SC-FDMA 심볼로 전송 SRS multiplexing by Time, Frequency, Cyclic shifts, and transmission comb (2 combs distributed SC-FDMA) To avoid the collision b/w SRS and PUSCH transmission from other UEs, SRS transmissions should not extend into the frequency band reserved for PUCCH. LTE/MIMO 표준기술 105
  106. 106. SRS – cont’d Non-frequency-hopping (wideband) SRS and frequency-hopping SRS Multiplexing of SRS transmissions from different UEs LTE/MIMO 표준기술 106
  107. 107. Uplink L1/L2 Control Signaling Uplink L1/L2 control signaling consists of: HARQ acknowledgements for received DL-SCH transport blocks UE reports downlink channel conditions including CQI, PMI, and RI Scheduling requests Two different methods for transmission of UL L1/L2 control signaling No simultaneous transmission of UL-SCH UE doesn’t have a valid scheduling grant, that is, no resources have been assigned for UL-SCH in the current subframe PUCCH is used for transmission of UL L1/L2 control signaling Simultaneous transmission of UL-SCH UE has a valid scheduling grant, that is, resources have been assigned for UL-SCH in the current subframe UL L1/L2 control signaling is time multiplexed with the coded UL-SCH onto PUSCH prior to SC- FDMA modulation Only HARQ acknowledgement and channel-status reports are transmitted No need to request a SR. Instead, in-band buffer status reports are sent in MAC headers The basis for channel-status reports on PUSCH is aperiodic reports If a periodic report is configured to be transmitted on PUCCH in a frame when US is scheduled to transmit PUSCH, then the periodic report is rerouted to PUSCH resources LTE/MIMO 표준기술 107
  108. 108. Periodic/Aperiodic Channel Info Feedback Periodic reporting Aperiodic reporting When to send Periodically every 2-160 ms When requested by eNB Normally on PUCCH, PUSCH used Where to send Always on PUSCH when multiplexed with data Payload size of the reports 4-11 bits Up to 64 bits Channel coding Linear block codes RM coding or tail-biting CC CRC protection No Yes, 8 bit CRC Sent in separate subframes at lower Sent separately encoded in the RI periodicity same subframe Only very limited amount of Detailed frequency selective reports Freq. selectivity of CQI frequency info are possible Frequency selective PMI reports are Freq. selectivity of PMI Only wideband PMI possible LTE/MIMO 표준기술 108
  109. 109. UL L1/L2 control signaling on PUCCH The reasons for locating PUCCH resources at the edges of the spectrum To maximize frequency diversity To retain single-carrier property Multiple UEs can share the same PUCCH resource block Format 1: length-12 orthogonal phase rotation sequence + length-4 orthogonal cover Format 2: length-12 orthogonal phase rotation sequence PUCCH is never transmitted simultaneously with PUSCH from the same UE 2 consecutive PUCCH slots in Time-Frequency Hopping at the slot boundary LTE/MIMO 표준기술 109
  110. 110. Changing UL System BW Via PUCCH Config LTE/MIMO 표준기술 110
  111. 111. PUCCH Formats Multiplexing PUCCH Modulation Number of bits Usage capacity format scheme per subframe (UE/RB) 1 N/A N/A SR 36, 18*, 12 1a BPSK 1 ACK/NACK 36, 18*, 12 1b QPSK 2 ACK/NACK 36, 18*, 12 2 QPSK 20 CQI 12, 6*, 4 2a QPSK+BPSK 21 CQI + ACK/NACK 12, 6*, 4 2b QPSK+QPSK 22 CQI + ACK/NACK 12, 6*, 4 * Typical value with 6 different rotations (choosing every second cyclic shift) PUCCH Format 2/2a/2b is located at the outermost RBs of system BW ACK/NACK for persistently scheduled PDSCH and SRI are located next ACK/NACK for dynamically scheduled PDSCH are located innermost RBs LTE/MIMO 표준기술 111
  112. 112. PUCCH Resource Mapping Format 1 4 symbols are modulated by BPSK/QPSK BPSK/QPSK symbol is multiplied by a length-4 orthogonal cover sequence (a length-3 orthogonal cover when there is SRS), and then it modulates the rotated length-12 sequence. Reference signals also employ one orthogonal cover sequence PUCCH capacity: up to 3 x 12 = 36 different UEs per each cell-specific sequence (assuming all 12 rotations being available Practically, only 6 rotations.) Format 2 5 symbols are modulated by QPSK after being multiplied by a phase rotated length-12 cell specific sequence. Resource consumption of one channel-status report is 3x of HARQ acknowledgement LTE/MIMO 표준기술 112
  113. 113. More on PUCCH Multiplexing CDM and FDM Two ways for CDM CDM by means of cyclic shifts of a CAZAC sequence CDM by means of block-wise spreading with the orthogonal cover sequences Two main issues with CDM Channel delay spread limits the orthogonality between cyclically shifted CAZAC sequences Channel Doppler spread limits the orthogonality between block-wise spread sequences LTE/MIMO 표준기술 113
  114. 114. PUCCH Format1 Processing LTE/MIMO 표준기술 114
  115. 115. PUCCH Format2 Processing LTE/MIMO 표준기술 115
  116. 116. UL L1/L2 control signaling on PUSCH LTE/MIMO 표준기술 116
  117. 117. More on Control Signalling on PUSCH CQI/PMI transmitted on PUSCH uses the same modulation scheme as data. ACK/NACK and RI are transmitted so that the coding/scrambling/ modulation maximize the Euclidean distance at the symbol level. The outermost constellation points are used to signal these for 16QAM and 64QAM. Different channel coding 1-bit ACK/NACK: repetition coding 2-bit ACK/NACK/RI: simplex coding CQI/PMI < 11bits: (32,N) Reed-Muller coding CQI/PMI > 11bits: tail-biting CC (1/3) How to keep the performance of control signaling on PUSCH? Different power offset? No! Because SC properties are partially destroyed. Variable coding rate? Yes! The size of physical resources for control is scaled. LTE/MIMO 표준기술 117
  118. 118. PUSCH Processing (1) LTE/MIMO 표준기술 118
  119. 119. UL SC-FDMA Signal Generation This section applies to all uplink physical signals and physical channels except the physical random access channel SC-FDMA parameters 0 ≤ t < (N CP ,l + N )× Ts where N = 2048 Check with numbers in Table 5.2.3-1. {(160+2048) x Ts} + 6 x {(144+2048) x Ts} = 0.5 ms 6 x {(512+2048) x Ts} = 0.5 ms LTE/MIMO 표준기술 119
  120. 120. PUSCH Frequency Hopping PUSCH transmission Localized transmission w/o frequency hopping Frequency Selective Scheduling Gain Localized transmission with “frequency hopping” Frequency Diversity Gain, Inter-cell Interference Randomization Two types of PUSCH frequency hopping Subband-based hopping according to cell-specific hopping patterns Hopping based on explicit hopping information in the scheduling grant LTE/MIMO 표준기술 120
  121. 121. Hopping based on cell-specific patterns Subbands are defined In 10 MHz BW case, the overall UL BW corresponds to 50 RBs and there are a total of 4 subbands, each consisting of 11 RBs. The remaining 6 RBs are used for PUCCH transmission. The resource defined by a scheduling grant (VRBs) is not the actual set of RBs for transmission. The resource to use for transmission (PRBs) is the resource provided in the scheduling grant “shifted” a number of subbands according to a cell-specific hopping pattern. LTE/MIMO 표준기술 121
  122. 122. More on hopping w/ cell-specific patterns Example for predefined hopping for PUSCH with 20 RBs and M=4 (subband hopping + mirroring) LTE/MIMO 표준기술 122
  123. 123. Hopping based on explicit information Explicit hopping information provided in the scheduling grant is about the “offset” of the resource in the second slot, relative to the resource in the first slot Selection b/w hopping based on cell-specific hopping patterns or hopping based on explicit information can be done dynamically. Cell BW less than 50 RBs 1 bit in scheduling grant indicating to specify which scheme is to be used When hopping based on explicit information is selected, the offset is always half of BW Cell BS equal or larger than 50 RBs 2 bits in scheduling grant One of the combinations indicate that hopping should be based on cell-specific hopping patterns Three remaining combinations indicate hopping of 1/2, +1/4, and -1/4 of BW LTE/MIMO 표준기술 123
  124. 124. PRACH PRACH는 RA 과정에서 단말이 기지국으로 전송하는 preamble이다 6RB를 차지하며 부반송파 간격은 1.25kHz (format #4는 7.5kHz) 64 preamble sequences for each cell 64 random access opportunities per PRACH resource Sequence부분은 길이 839의 Z-C sequence로 구성 (format #4는 길이 139) Phase modulation: Due to the ideal auto-correlation property, there is no intra-cell interference from multiple random access attempt using preambles derived from the same Z-C root sequence. Five types of preamble formats to accommodate a wide range of scenarios Higher layers control the preamble format 넓은 반경의 셀 환경과 같이 시간 지연이 긴 경우 SINR이 낮은 상황을 고려하여 sequence repetition SINR이 낮은 상황을 고려하여 sequence repetition TDD 모드용 LTE/MIMO 표준기술 124
  125. 125. Different Preamble Formats LTE/MIMO 표준기술 125
  126. 126. PRACH Location LTE/MIMO 표준기술 126
  127. 127. UL 16QAM SC-FDMA LTE/MIMO 표준기술 127
  128. 128. LTE Cell Search
  129. 129. Synchronization Signals 504 unique physical-layer cell identities 168 unique physical-layer cell-identity groups (0~167) 3 physical-layer identity within physical-layer cell-identity group (0~2) SS is using single antenna port However, SS can be with UE-transparent transmit antenna scheme (e.g. PVS, TSTD, CDD) Primary SS (PSS) and Secondary SS (SSS) LTE/MIMO 표준기술 129
  130. 130. Primary Synchronization Signal The sequence used for the primary synchronization signal is generated from a frequency- domain Zadoff-Chu sequence (Length-62) ⎧ − j πun ( n +1) ⎪ e 63 n = 0,1,...,30 d u (n) = ⎨ πu ( n +1)( n + 2) ⎪e − j 63 n = 31,32,...,61 ⎩ For frame structure type 1, PSS is mapped to the last OFDM symbol in slots 0 and 10 No need to know CP length The sequence is mapped to REs (6 RBs) according to DL RB ak ,l = d (n ), N RB N sc k = n − 31 + , l = N symb − 1, DL n = 0,...,61 2 Cell ID detection within a cell ID group (3 hypotheses) Half-frame timing detection (Repeat the same sequence twice) LTE/MIMO 표준기술 130
  131. 131. Secondary Synchronization Signal The sequence used for the second synchronization signal is an interleaved concatenation of two length-31 binary sequences (X and Y) The concatenated sequence is scrambled with a scrambling sequence given by PSS The combination of two length-31 sequences defining SSS differs between slot 0 (SSS1) and slot 10 (SSS2) according to ⎧s0m0 ) (n)c0 (n ) in subframe 0 ⎪ ( d ( 2 n) = ⎨ ( m ) ⎪s1 1 (n)c0 (n ) in subframe 5 ⎩ ⎧s1 m1 ) (n)c1 (n )z1 m0 ) (n ) in subframe 0 ⎪ ( ( d (2n + 1) = ⎨ ( m ) ⎪s0 0 (n)c1 (n )z1 1 (n ) in subframe 5 (m ) ⎩ where 0 ≤ n ≤ 30 Blind detection of CP-length (2 FFT operations are needed) The same antenna port as for the primary sync signal Mapped to 6 RBs LTE/MIMO 표준기술 131
  132. 132. Structure of SSS LTE/MIMO 표준기술 132
  133. 133. Synchronization Signals – cont’d Cell ID group detection (the set of valid combination of X and Y for SSS are 168) Frame boundary detection (the m-sequences X and Y are swapped b/w SSS1 and SSS2) LTE/MIMO 표준기술 133
  134. 134. LTE Cell Search Primary SS Symbol timing acquisition Frequency synchronization Cell ID detection within a cell group ID (3 hypotheses) Half-frame boundary detection Secondary SS Cell group ID detection (168 hypotheses) Frame boundary detection (2 hypotheses) CP-length detection (2 hypotheses) Check Cell ID with cell-specific RS BCH 40ms BCH period timing detection eNB # of tx antenna detection MIB acquisition (Operation BW, SFN, etc…) PDCCH reception SIB acquisition within PDSCH LTE/MIMO 표준기술 134
  135. 135. (cf) WCDMA Cell Search Procedure Terminal power on Detect strongest PSCH Get slot synch from P-SCH Get PICH code group info from S-SCH 8 PN codes per group. 64 code groups have 512 PN codes in total. Get PN code info by evaluating all 8 PN codes in code group Get system info from PCCPCH Wait while monitoring SCCPCH LTE/MIMO 표준기술 135
  136. 136. LTE Cell Search – cont’d* PSS/SSS, BCH 3 1.4 LTE/MIMO 표준기술 136
  137. 137. Summary
  138. 138. LTE Frame & Slot Structure LTE/MIMO 표준기술 * 윤상보 (삼성), “3GPP LTE & LTE-Advanced System”, 제5차 차세대이동통신 단기강좌, Aug. 2008 138
  139. 139. DL Frame Structure Type 1* LTE/MIMO 표준기술 139
  140. 140. UL Frame Structure Type 1* 1 RB LTE/MIMO 표준기술 140
  141. 141. E-UTRA UE Capabilities* * 3GPP TS 36.306, E-UTRA; UE Radio Access Capabilities, LTE/MIMO 표준기술 Release 8, V8.4.0, June 2009 141
  142. 142. LTE with Voice? Long-term Maybe through IMS Near-term CS Fallback NTT DoCoMo pushed the industry to include CS Fallback as part of the 3GPP standard. With CS Fallback the operator accepts the notion that its brand new LTE network won’t support voice and SMS services. Instead, a control signal is sent to the LTE device indicating an incoming voice call/SMS message at which point the device falls back to the legacy 2G/3G network to receive the call/message. Largely comparable to 1xEV-DO/1X Won’t work for 3GPP2 operators (e.g. Verizon, KDDI, and LGT) VoLGA Leverage the operator’s existing circuit switched CN to carry voice calls and SMS messages over the LTE air interface. In many respects VoLGA is comparable to GAN/UMA, which is how operators like Orange UK and T-Mobile USA leverage Wi-Fi access points to offload voice traffic from their macro cellular networks. In other words VoLGA = GAN/UMA – Wi-Fi. Has been ruled out as from Release 8 or Release 9 of 3GPP The driver for LTE is the rapid acceleration of mobile data traffic, thus it would be counter productive to use LTE for voice services. What about SR-VCC (Single Radio Voice Call Continuity) to GSM/WCDMA/CDMA? What about coverage? LTE/MIMO 표준기술 142
  143. 143. CS Fallback Mobile terminated call Mobile originated call LTE/MIMO 표준기술 143
  144. 144. Evolution Beyond Release 8 LTE MBMS SON enhancements Further improvements for enhanced VoIP support in LTE The requirements for the multi-bandwidth and multi-radio access technology base station Enhanced mobility support for LTE Enhanced positioning support for LTE Dual layer beam forming for Rel.9 Enhanced DL transmission for LTE Home-(e)NB And… LTE-Advanced with Release 10 LTE/MIMO 표준기술 144
  145. 145. LTE and WiMAX What is 4G (through LTE and WiMAX)? New Technology: OFDM + MIMO New Biz Model: Mobile Broadband LTE is justifying WiMAX and WiMAX is justifying LTE They are using the same fundamental technologies They are targeting the same market Convergence?? In technical area: 3GPP LTE-Adv & IEEE 802.16m are getting more and more similar In biz area: Ecosystem?? LTE/MIMO 표준기술 145
  146. 146. Final Message* * Signals Ahead LTE/MIMO 표준기술 146
  147. 147. References [1] 3GPP homepage: www.3gpp.org [2] Hannes Ekström, Anders Furuskär, Jonas Karlsson, Michael Meyer, Stefan Parkvall, Johan Torsner, and Mattias Wahlqvist (Ericsson), “Technical Solutions for the 3G Long-Term Evolution”, IEEE Communications Magazine, March 2006 [3] Erik Dahlman, Hannes Ekstrom, Anders Furuskar, Ylva Jading, Jonas Karlsson, Magnus Lundevall, and Stefan Parkvall (Ericsson), “The 3G Long-Term Evolution - Radio Interface Concepts and Performance Evaluation”, IEEE VTC 2006 [4] Leonard J. Cimini Jr. and Ye (Geoffrey) Li, “Orthogonal frequency division multiplexing for wireless channels”, AT&T Labs – Research [5] Richard van Nee and Ramjee Prasad, OFDM for Wireless Multimedia Communications, Artech House Publishers [6] D. Falconer, et al., “Frequency domain equialization for single-carrier broadband wireless systems,” IEEE Communication Magazine, vol.40, no.4, April 2002 [7] Hyung G. Myung, Junsung Lim, and David J. Goodman, “Single Carrier FDMA for Uplink Wireless Transmission”, IEEE Vehicular Technology Magazine, Sep. 2006 [8] 오민석 (LGE), “3GPP LTE”, KRnet 2007, June 29 2007 [9] 김학성 (LGE), “3GPP LTE PHY Layer Specification and Technology”, 제4차 차세대이동통신 단기강좌, Feb. 2008 [10] Moray Rumney (Agilent), “Concepts of 3GPP LTE”, Live Webinar, Sep. 2007 [11] 이상근, 조봉열, 여운영, 쉽게 설명한 3G/4G 이동통신 시스템 (2nd edition), 홍릉과학출판사, 2009 [12] Erik Dahlman, et al, 3G Evolution: HSPA and LTE for Mobile Broadband (2nd edition), Academic Press, 2008 [13] Harri Holma and Antti Toskala, LTE for UMTS: OFDMA and SC-FDMA Based Radio Access, Wiley, 2009 [14] Stefania Sesia, Issam Toufik, and Matthew Baker, LTE, The UMTS Long Term Evolution: From Theory to Practice, Wiley, 2009 [15] David Astély, et al, “LTE: The Evolution of Mobile Broadband,” IEEE Commun. Mag. April 2009 [16] Anna Larmo, et al, “The LTE Link-Layer Design,” IEEE Commun. Mag. April 2009 [17] LSTI, “Latest Results from the LSTI,” Feb. 2009; http://www.lstiforum.com/file/news/Latest_LSTI_Results_Feb09_v1.pdf LTE/MIMO 표준기술 147

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