LTE Physical layer aspects
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This document discusses enhancements to the physical layer of LTE-Advanced (3GPP Release 10). It describes the downlink and uplink physical layer designs, including orthogonal multiple access schemes, reference signals, control signaling, and data transmission methods. It also covers support for time division duplexing, half-duplex frequency division duplexing, and UE categories defined in 3GPP Release 8. The goal of LTE-Advanced is to further improve the LTE standard to meet the requirements of IMT-Advanced.
![System Performance Requirements for
LTE-Advanced
Peak data rate
• 1 Gbps data rate will be achieved by 4-by-4 MIMO and transmission
bandwidth wider than approximately 70 MHz
Peak spectrum efficiency
• DL: Rel. 8 LTE satisfies IMT-Advanced requirement
• UL: Need to double from Release 8 to satisfy IMT-Advanced
requirement
Rel. 8 LTE LTE-Advanced IMT-Advanced
DL 300 Mbps 1 Gbps
Peak data rate 1 Gbps(*)
UL 75 Mbps 500 Mbps
Peak spectrum efficiency DL 15 30 15
[bps/Hz]
UL 3.75 15 6.75
*“100 Mbps for high mobility and 1 Gbps for low mobility” is one of the key features as written in
Circular Letter (CL)
REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 39](https://image.slidesharecdn.com/rev-090003-r1-100324020303-phpapp01/85/LTE-Physical-layer-aspects-39-320.jpg)
LTE Physical layer aspects
- 1. REV-090003r1 LTE-Advanced Physical Layer Matthew Baker, Alcatel-Lucent Chairman 3GPP TSG RAN WG1 REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 1
- 2. Contents Introduction Downlink Physical Layer Design Uplink Physical Layer Design Specific support for TDD Specific support for half-duplex FDD UE categories in Rel-8 Enhancements for LTE-Advanced REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 2
- 3. Releases of 3GPP specifications 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 GSM/GPRS/EDGE enhancements Release 99 W-CDMA Release 4 1.28Mcps TDD Release 5 HSDPA, IMS Release 6 HSUPA, MBMS, IMS+ Release 7 HSPA+ (MIMO, HOM etc.) ITU-R M.1457 IMT-2000 Recommendations Release 8 LTE, SAE Small LTE/SAE Release 9 enhancements Release 10 LTE-Advanced REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 3
- 4. Physical Layer Specifications TS 36.201 E-UTRA 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 The latest version of the specifications can be downloaded from: • http://www.3gpp.org/ftp/Specs/ REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 4
- 5. Orthogonal Multiple Access Schemes Downlink: OFDMA • High spectral efficiency • Robust against frequency-selectivity / multi-path interference • Inter-symbol interference contained within cyclic prefix • Supports flexible bandwidth deployment • Facilitates frequency-domain scheduling • Well suited to advanced MIMO techniques Uplink: SC-FDMA • Based on OFDMA with DFT precoding • Common structure of transmission resources compared to downlink • Cyclic prefix supports frequency-domain equalisation • Low Cubic Metric for efficient transmitter design REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 5
- 6. LTE Release 8 Major Parameters Access Scheme DL OFDMA UL SC-FDMA Bandwidth 1.4, 3, 5, 10, 15, 20 MHz Minimum TTI 1 ms Sub-carrier spacing 15 kHz Cyclic prefix length Short 4.7 µs Long 16.7 µs Modulation QPSK, 16QAM, 64QAM Spatial multiplexing Single layer for UL per UE Up to 4 layers for DL per UE MU-MIMO supported for UL and DL REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 6
- 7. Transmission Resource structure One downlink slot, T slot Basic unit of resource is the Physical Resource Block (PRB) 12 sub-carriers x 0.5 ms subcarriers Allocated in pairs (in time Resource element domain) BW RB NDL subcarriers 1 sub-carrier x 1 symbol = 1 One resource block, N resource element (RE) BW Spatial domain measured in “layers” REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing DL N symb OFDM symbols 7
- 8. One radio interface, 2 frame structures Supports both FDD and TDD (two RITs within one SRIT) • FDD • TDD REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 8
- 9. Contents Introduction Downlink Aspects Uplink Aspects Specific support for TDD Specific support for half-duplex FDD UE categories in Rel-8 Enhancements for LTE-Advanced REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 9
- 10. Low complexity cell acquisition Synchronisation signals and broadcast channel: • Fixed bandwidth • Centrally located • Allows straightforward bandwidth-agnostic cell-search Synchronisation signals and physical broadcast channel frequency REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 10
- 11. Cell acquisition signalling Synchronisation signals in subframes 0 and 5 of each 10 ms radio frame Physical broadcast channel (PBCH) in subframe 0 of each radio frame • Carries the Master Information Block (MIB) • Includes indication of system bandwidth • Robust design for cell-wide coverage: • Low rate, QPSK, robust channel coding (1/3-rate tail-biting convolutional code with repetition), 40 ms TTI • CRC indicates number of transmit antennas 1 coded MIB 40ms TTI of BCH 6 RBs dc REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing one 10 ms radio frame 11
- 12. Reference Signals (RS) In Rel-8, cell-specific RS are provided for 1, 2 or 4 antenna ports • Pattern designed for effective channel estimation • Sparse diamond pattern supports frequency-selective channels and high- mobility with low overhead • Up to 6 cell-specific frequency shifts are configurable • Power-boosting may be applied on the REs used for RS • QPSK sequence with low PAPR Antenna port 0 Antenna port 1 Antenna port 2 Antenna port 3 frequency R0 R0 R1 R1 R2 R3 R0 R0 R1 R1 R2 R3 R0 R0 R1 R1 R2 R3 R0 R0 R1 R1 R2 R3 time REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 12
- 13. UE-specific Reference Signals R5 R5 In Rel-8: R5 R5 • UE-specific (precoded) RS may be provided in R5 R5 data transmissions to specific UEs R5 R5 R5 R5 In Rel-9: l=0 R5 l =6 l =0 R5 l =6 • UE-specific RS extended to dual-layer transmission • CDM between RS R R R R 7 7 7 7 R 8 R8 R8 R 8 of the two layers R7 R7 R7 R7 R 8 R8 R8 R 8 R7 R7 R7 R7 R 8 R8 R8 R8 REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 13
- 14. Downlink control signalling Flexible design to avoid unnecessary overhead • First 1-3 OFDM symbols in each subframe (2-4 in narrow bandwidths) • Control region size is dynamically variable • Length indicated by Physical Control Format Indicator Channel (PCFICH) in first OFDM symbol of each subframe • PCFICH is designed to be robust – 16 QPSK symbols transmitted with full frequency diversity Within the control region: • Physical Downlink Control Channel (PDCCH) carries Downlink Control Information (DCI) messages: • downlink resource assignments • uplink resource grants • uplink power control commands • Physical Hybrid ARQ Indicator Channel (PHICH) carries ACK/NACK for UL data transmissions REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 14
- 15. Downlink data transmission Physical Downlink Shared One subframe = 1 ms Channel (PDSCH) 12 subcarriers • Carries user data, broadcast system information, paging messages Data for UE1: • Transmission resources are (localised) assigned dynamically by PDCCH • Localised (suitable for Data for UE2: frequency domain scheduling) (distributed) or Data for UE3: • distributed (suitable for maximising frequency diversity) REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 15
- 16. PDSCH physical layer processing a0 , a1 ,..., a A −1 Each TTI, 1 or 2 transport blocks are processed from MAC layer b0 , b1 ,..., b B −1 Channel coding is based on 1/3 rate turbo code with trellis termination to approach cr 0 , cr1 ,..., cr (K r −1) Shannon capacity Circular buffer rate matching d r(i0) , d r(1) ,..., d r(i()D i r −1) Modulation QPSK, 16QAM, 64QAM Layer mapping and precoding for support of er 0 , er1 ,..., er (Er −1) multi-antenna transmission f 0 , f1 ,..., f G −1 REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 16
- 17. PDSCH transmission modes In Rel-9, each UE is configured in one of 8 “transmission modes” for PDSCH reception: • Mode 1: Single antenna port, port 0 • Mode 2: Transmit diversity • Mode 3: Large-delay CDD • Mode 4: Closed-loop spatial multiplexing • Mode 5: MU-MIMO • Mode 6: Closed-loop spatial multiplexing, single layer • Mode 7: Single antenna port, UE-specific RS (port 5) • Mode 8 (new in Rel-9): Single or dual-layer transmission with UE- specific RS (ports 7 and/or 8) (in each case, transmit diversity is also available as a fallback) REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 17
- 18. Details of PDSCH transmission modes (1) Mode 2: • SFBC for 2 antenna ports • SFBC / FSTD for 4 antenna ports Mode 3: • Large delay CDD – increases frequency selectivity • Allows open-loop spatial multiplexing • Up to rank 2 without closed loop precoding feedback from UE Mode 4: • Precoding using specified codebook for the relevant number of antenna ports • Supports up to 4 layers • Max 2 codewords to limit signalling overhead • Closed-loop precoding feedback from UE • Used precoding matrix is indicated to UE on PDCCH REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 18
- 19. Details of PDSCH transmission modes (2) Mode 5: • Rank 1 MU-MIMO • Based on same precoding codebooks and feedback as Mode 4 • PDCCH indicates power offset for PDSCH Mode 6: • Based on mode 4 but for single-layer only Mode 7: • UE-specific RS • Suitable for UE-specific beamforming, e.g. based on angle of arrival (no closed-loop precoding feedback from UE) Mode 8: • Dual-layer UE-specific RS • Closed-loop precoding feedback may or may not be used • Supports dual-layer SU-MIMO and single-layer MU-MIMO REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 19
- 20. MBMS R4 Supports Single-Frequency R4 R4 Network operation for high R4 performance: “MBSFN” R4 R4 subframes R4 R4 R4 • Physical Multicast Channel (PMCH) R4 is used instead of PDSCH R4 R4 • Special RS pattern with higher R4 density in frequency domain R4 R4 supports longer “delay spread” R4 from multi-cell transmission R4 R4 even-numbered slots odd-numbered slots Antenna port 4 REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 20
- 21. Contents Introduction Downlink Aspects Uplink Aspects Specific support for TDD Specific support for half-duplex FDD UE categories in Rel-8 Enhancements for LTE-Advanced REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 21
- 22. Uplink multiple access: SC-FDMA Same parameterisation as downlink DFT precoding ensures low PAPR / cubic metric Cyclic prefix facilitates frequency-domain equalisation at eNodeB REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 22
- 23. UL transmission resource allocation One subframe = 1 ms Same structure of PRBs in frequency domain as downlink Contiguous PRB allocation 12 sub-carriers Possibility to configure frequency hopping to increase frequency diversity Number of allocated PRBs for a given user in a given subframe is in multiples of 2, 3 and 5 for low- complexity DFT implementation REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 23
- 24. Timing Advance Uplink transmission orthogonality between users is maintained by timing advance Set initially during Random Access Procedure Updated as necessary subsequently Supports at least 100 km cell range • Greater ranges are up to the implementation Downlink radio frame #i Uplink radio frame #i NTA×TS time units REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 24
- 25. Uplink channel structure Data transmissions on Physical Uplink Shared Channel (PUSCH) • In centre of uplink bandwidth • Minimises out-of-band emissions from wide-bandwidth data transmissions • 1 transport block per TTI • Same channel coding / rate matching as PDSCH • Modulation QPSK, 16QAM, 64QAM When PUSCH is transmitted, any = N RB − 1 nPRB UL m =1 m=0 control signalling is multiplexed m=3 m=2 with data to maintain single carrier structure When no PUSCH, control signalling PUSCH is on Physical Uplink Control Channel (PUCCH) • Usually at edges of system bandwidth m=2 m=3 • PUCCH hops from one side of thencarrier to PRB = 0 m=0 m =1 the other to maximise frequency diversity One subframe REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 25
- 26. Uplink Control Signalling ACK/NACK for PDSCH transmissions Scheduling Request (SR) Channel Quality Information • CQI – indicates an index of a Modulation / Coding Scheme (MCS) that could be received on PDSCH with BLER ≤ 0.1 • PMI – indicates preferred precoding matrix for PDSCH • RI – indicates number of useful transmission layers for PDSCH REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 26
- 27. Channel Quality reporting modes CQI/PMI/RI can be periodic – on PUCCH • Wideband or UE-selected sub-band CQI/PMI/RI can be aperiodic – on PUSCH • Triggered by 1 bit in PDCCH message • Wideband, UE-selected sub-band or higher-layer configured sub-band With or without PMI depending on the configured transmission mode REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 27
- 28. Random Access Channel (RACH) RACH procedure begins with a preamble (PRACH) PRACH resources assigned by eNB within PUSCH region PRACH preamble fits into 6 PRBs • Sufficient for timing estimation • Invariant with bandwidth for low PUSCH complexity • Zadoff Chu sequence PRACH • Excellent correlation properties – Zero correlation zone for different cyclic shifts • Flat frequency spectrum • Different sequences provided first by PUCCH different cyclic shifts, then by different root sequences Multiple PRACH formats suitable for different cell sizes REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 28
- 29. UL Reference Symbols Zadoff Chu sequences Demodulation RS (DM RS) • Embedded in each PUCCH and PUSCH transmission • Same bandwidth as control / data transmission Sounding RS (SRS) • In last symbol of a subframe • Can be configured by network • Supports: • UL frequency-domain scheduling • Channel sounding for downlink transmissions, especially for TDD • Uses interleaving in frequency domain (alternate subcarriers) to provide additional support for multiple users transmitting SRS in the same bandwidth REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 29
- 30. Uplink Power Control Controls uplink power spectral density • Total uplink transmit power scales linearly with transmitted bandwidth Fractional power control can compensate for all or part of path loss • Allows trade-off between intra-cell fairness and inter-cell interference MCS-specific offsets may be applied Closed-loop power control commands can fine-tune the power setting • Carried on PDCCH • Individual commands in UL resource grants • Group commands for groups of UEs Separate power control for PUCCH and PUSCH REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 30
- 31. UL Multi-Antenna transmission Rel-8/9 supports: • Switched antenna diversity • Closed-loop antenna switching supported by CRC masking on PBCH • MU-MIMO • Different cyclic shifts of DM RS can be allocated to different UEs REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 31
- 32. Contents Introduction Downlink Aspects Uplink Aspects Specific support for TDD Specific support for half-duplex FDD UE categories in Rel-8 Enhancements for LTE-Advanced REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 32
- 33. TDD operation Special timeslot for downlink-uplink switching: DwPTS DL UL GP subframe #0 subframe #2 SSS PSS RS/Control UpPTS Data UpPTS can transmit special short PRACH format or SRS TDD operation is also supported by: • An increased number of HARQ processes • ACK/NACK bundling / multiplexing configurations to enable control signalling to be transmitted REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 33
- 34. Contents Introduction Downlink Aspects Uplink Aspects Specific support for TDD Specific support for half-duplex FDD UE categories in Rel-8 Enhancements for LTE-Advanced REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 34
- 35. Half-duplex FDD operation From UE perspective, UL and DL do not overlap in time For DL-UL switching time, UE ignores end of DL subframe For UL-DL switching time, additional timing advance offset can be applied to the UL transmissions 1 ms subframe DL UL DL-to-UL switch time created by the UE UL-to-DL switch time created ignoring the last part of the DL subframe by timing advance REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 35
- 36. Contents Introduction Downlink Aspects Uplink Aspects Specific support for TDD Specific support for half-duplex FDD UE categories in Rel-8 Enhancements for LTE-Advanced REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 36
- 37. LTE-Release 8 User Equipment Categories Category 1 2 3 4 5 Peak rate DL 10 50 100 150 300 Mbps UL 5 25 50 50 75 Capability for physical functionalities RF bandwidth 20MHz Modulation DL QPSK, 16QAM, 64QAM UL QPSK, 16QAM QPSK, 16QAM, 64QAM Multi-antenna 2 Rx diversity Assumed in performance requirements. 2x2 MIMO Not Mandatory supported 4x4 MIMO Not supported Mandatory REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 37
- 38. Contents Introduction Downlink Aspects Uplink Aspects Specific support for TDD Specific support for half-duplex FDD UE categories in Rel-8 Enhancements for LTE-Advanced REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 38
- 39. System Performance Requirements for LTE-Advanced Peak data rate • 1 Gbps data rate will be achieved by 4-by-4 MIMO and transmission bandwidth wider than approximately 70 MHz Peak spectrum efficiency • DL: Rel. 8 LTE satisfies IMT-Advanced requirement • UL: Need to double from Release 8 to satisfy IMT-Advanced requirement Rel. 8 LTE LTE-Advanced IMT-Advanced DL 300 Mbps 1 Gbps Peak data rate 1 Gbps(*) UL 75 Mbps 500 Mbps Peak spectrum efficiency DL 15 30 15 [bps/Hz] UL 3.75 15 6.75 *“100 Mbps for high mobility and 1 Gbps for low mobility” is one of the key features as written in Circular Letter (CL) REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 39
- 40. Carrier Aggregation Wider bandwidth transmission using carrier aggregation • Entire system bandwidth up to, e.g., 100 MHz, comprises multiple basic frequency blocks called component carriers (CCs) Satisfy requirements for peak data rate • Each CC can be configured in a backward compatible way with Rel-8 LTE Maintain backward compatibility with Rel-8 LTE • Carrier aggregation supports both contiguous and non-contiguous spectrum, and asymmetric bandwidth for FDD Achieve flexible spectrum usage System bandwidth, CC, e.g., 20 MHz e.g., 100 MHz Examples of Frequency UE capabilities • 100-MHz case • 40-MHz case • 20-MHz case (Rel. 8 LTE) REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 40
- 41. Downlink Multiple Access Scheme Downlink: OFDMA with component carrier (CC) based structure Priority given to reusing Rel. 8 specification for low-cost and fast development • One transport block is mapped Transport Transport Transport Transport block block block block within one CC • Parallel-type transmission for multi-CC transmission Channel Channel Channel Channel coding coding coding coding HARQ HARQ HARQ HARQ • Good affinity to Rel. 8 LTE specifications Mod. Mod. Mod. Mod. • Cross-carrier scheduling is Mapping Mapping Mapping Mapping possible: • PDCCH on one carrier can CC relate to data on another carrier REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 41
- 42. Uplink Multiple Access Scheme Uplink: N-times DFT-Spread OFDM Achieve wider bandwidth by adopting parallel multi-CC transmission Satisfy requirements for peak data rate while maintaining backward compatibility Low-cost and fast development by reusing Rel. 8 specification • Will also support non-contiguous resource allocation • Enhanced flexibility and efficiency of resource allocation • Simultaneous PUCCH and PUSCH transmission will be supported. • Independent power control will be provided per CC “N-times DFT-Spread OFDM” CC CC PUCCH region Parallel Rel. 8 LTE Freq. PUSCH transmission (Physical uplink shared channel) REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 42
- 43. Enhanced Downlink Multi-antenna Transmission (1) Extension up to 8-layer transmission Max. 8 streams • Increased from 4 layers in Rel-8/9 Satisfy the requirement for peak spectrum efficiency, i.e., 30 bps/Hz Additional reference signals (RS) specified: - Channel state information RS (CSI-RS) • For downlink channel sounding • Sparse, low overhead (configurable) - UE-specific demodulation RS (DM-RS) • UE-specific DM-RS can be precoded, supporting non-codebook-based precoding • UE-specific DM-RS will enable application of enhanced multi-user beamforming such as zero forcing (ZF) for, e.g., 4-by-2 MIMO • DM RS pattern for higher numbers of layers is extended from 2-layer format for transmission mode 8 in Rel-9 • E.g. for 4 antenna ports: REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 43
- 44. Enhanced Downlink Multi-antenna Transmission (2) Support for enhanced MU-MIMO is being studied CSI feedback Enhancements to CSI feedback are being studied • Implicit feedback based on Rel-8 CQI/PMI/RI framework • Explicit feedback • considering gain versus overhead Enhanced MU-MIMO CoMP schemes are being studied • Joint processing (JP) • Joint transmission (JT): PDSCH is transmitted from multiple cells with precoding using DM- RS among coordinated cells • Dynamic cell selection: PDSCH is transmitted from one cell, which is dynamically selected • Coordinated scheduling/beamforming (CS/CB) • PDSCH transmitted only from 1 cell; scheduling/beamforming is coordinated among cells Coherent combining or dynamic cell selection Joint transmission/dynamic cell selection Coordinated scheduling/beamforming REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 44
- 45. Enhanced Uplink Multi-antenna Transmission Introduction of UL transmit diversity for PUCCH Improved signalling robustness and cell-edge performance Introduction of single user (SU)-MIMO up to 4-stream transmission Satisfy the requirement for peak spectrum efficiency, i.e., 15 bps/Hz Signal detection scheme with affinity to DFT-S-OFDM for SU-MIMO • Turbo serial interference canceller (SIC) is assumed to be used for eNB receivers to achieve higher throughput performance for DFT-S-OFDM Improve user throughput, while maintaining low cubic-metric signal transmission Max. 4 streams SU-MIMO up to 4 streams REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 45
- 46. CoMP Reception in Uplink CoMP reception scheme in uplink • Physical uplink shared channel (PUSCH) is received at multiple cells • Scheduling is coordinated among the cells Improve especially cell-edge user throughput • Note that CoMP reception in uplink is an implementation matter and does not require any change to radio interface Receiver signal processing at central eNB (e.g., MRC, MMSEC) Multipoint reception REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 46
- 47. Relaying “Type 1” relay • Relay node (RN) creates a separate cell distinct from the donor cell • UE receives/transmits control signals for scheduling and HARQ from/to RN • RN appears as a Rel-8 LTE eNB to Rel-8 LTE UEs Supports deployment of cells in areas where wired backhaul is not available or very expensive Other relay types are also being studied Higher node Cell ID #x Cell ID #y eNB RN UE REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 47
- 48. Conclusions LTE-Advanced is a very flexible and advanced system Built on the established capabilities of the LTE Rel-8 and Rel-9 physical layer Further enhancements to exploit spectrum availability and advanced multi-antenna techniques REV-090003r1 IMT-Advanced Evaluation Workshop 17 – 18 December, 2009, Beijing 48