Aalborg Universitet. Status på LTE-A Sørensen, Troels Bundgaard. Publication date: Document Version Accepteret manuscript, peer-review version

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1 Aalborg Universitet Status på LTE-A Sørensen, Troels Bundgaard Publication date: 2012 Document Version Accepteret manuscript, peer-review version Link to publication from Aalborg University Citation for published version (APA): Sørensen, T. B. (2012). Status på LTE-A: Standardisering og teknologi. Poster session præsenteret ved Status og perspektiv for næste generation Mobilt bredbånd i Danmark, København, Danmark. General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.? Users may download and print one copy of any publication from the public portal for the purpose of private study or research.? You may not further distribute the material or use it for any profit-making activity or commercial gain? You may freely distribute the URL identifying the publication in the public portal? Take down policy If you believe that this document breaches copyright please contact us at vbn@aub.aau.dk providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from vbn.aau.dk on: juni 08, 2018

2 Status på LTE-A Standardisering og teknologi Præsenteret af Troels B. Sørensen Sektionen for Radio Access Teknologi (RATE), Aalborg Universitet IDA-TTS Konference, 4. december, Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december Aalborg University/RATE IDA-TTS Matti Kiiski, konference/ 1 July 2011 Troels B. Sørensen / 4. december 2012

3 Standardization ITU-R International Telecommunication Union - Radiocommunication (sector) IMT-A International Mobile Telecommunications - Advanced E-UTRAN Evolved UMTS Terrestrial Radio Access Network UMTS Universal Mobile Telecommunications System 3GPP 3rd Generation Partnership Program LTE Long Term Evolution enb evolved Node B UE User Equipment 3 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 Requirements The 3GPP LTE evolution to meet/exceed the ITU-R IMT-Advanced capabilities of a 1Gbps (4G) system Peak data rates of 100 Mbit/s for high and 1 Gbit/s for low mobility Peak spectral efficiencies 15bps/Hz downlink (4 4 MIMO) and 7.5bps/Hz uplink (2 4 MIMO) Bandwidth scalability up to 40MHz, and preferably to 100MHz User plane latency 10ms and 100ms for control (idle to active) 3GPP set its own requirements for LTE-Advanced as detailed in 3GPP TR , including Increased spectral efficiencies (improved efficiency over LTE) Average targets increased 30% for downlink and 40% for uplink Peak extended to 8 8 MIMO downlink and 4 4 MIMO uplink Meeting 3GPP operator requirements for the evolution of E-UTRA Self-Organizing Networks (SON) Backwards compatibility requirements A Release 8 E-UTRA terminal can work in an Advanced E-UTRAN, An Advanced E-UTRA terminal can work in an Release 8 E-UTRAN 4 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012

4 Technology Components These fulfill the ITU requirements for 3-sector macro 1 st LTE field trial Berlin, 11/2007 Key ingredients Carrier Aggregation up to 100 MHz Smooth Migration to LTE-A Carrier1 Carrier2 Carrier3 Carrier5 MIMO 8x 4x Cooperative Systems Backward compatible to LTE Relaying Mobility Heterogeneous Networks LTE standardization is not driven only by IMT-Advanced! 5 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 Standardization 3GPP Releases PAST LTE-A LTE-A Study Items Rel. 10 First LTE-A release NOW LTE-A Work Items LTE-A The 18 months cycle for releases - and market (terminal) introduction and the next almost here Rel. 11 Rel. 12? Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012

5 Standardisation - Specifications The core of the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) specifications relates to the 36 series of the 3GPP specifications (overview of the 3GPP specification numbering) X2 Specifications and responsible Radio Access Network (RAN) Working Group RF: , (RAN4) L2/L3: , , /306 (RAN2) X2: (RAN3) LTE and LTE-A in Rel. 10 and beyond specifications UE L1: (RAN1) Air interface enb S1: (RAN3) S1 Packet core After LTE for UMTS, Wiley Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 Technology Components CA, MIMO, HetNet (eicic), CoMP, Relays 8 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012

6 Carrier Aggregation (CA) BW Bandwidth RRC Radio Ressource Control (layer or signalling) PDCCH Physical Downlink Control CHannel PUCCH Physical Uplink Control CHannel CQI Channel Quality Indicator FDD Frequency Division Duplex DL Downlink UL Uplink CC Component Carrier PCell/SCell Primary and Secondary Cell CRS Common Reference Signal PSS/SSS Primary and Secondary Synchronization Signal OFDM Orthogonal Frequency Division Multiplexing CCE Common Control Element BCCH Broadcast Control CHannel RRC Radio Ressource Control (signalling) CQI Channel Quality Indicator NACK/ACK Negative Acknowledge CSI Channel State Information PRB Physical Resource Block 9 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 Carrier Aggregation (CA) High peak data rates achieved even with fragmented spectrum (important practical aspect) Backwards compatibility requirements with Release 8 LTE is achieved with carrier aggregation by combining up to N = 5 Release 8 component carriers to form N x LTE bandwidth, for example 5 x 20 MHz = 100 MHz LTE terminals receive/transmit on one component carrier, whereas LTE- Advanced terminals may receive/transmit on multiple component carriers simultaneously Both contiguous and non-contiguous CA is supported offering improved spectrum flexibility (e.g. for refarming). Primary and Secondary Cells (Component Carriers - CC) 10 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012

7 CA Band Combinations Initial focus is on CA for two band combinations, specific to different regions of the world Radio frequency aspects are being handled per case and in a release independent manner Band (FDD) Band (FDD) Band 20: MHz (DL) MHz (UL) Band 7: MHz (UL) MHz (DL) Band 3: MHz (UL) MHz (DL) Band 7: MHz (UL) MHz (DL) Current RF specification work has been prioritized to focus on downlink CA CA for uplink is more complicated and will be standardized based on the DL CA combinations Spurious Harmonics Broadband noise Need for (maximum) power reduction of 4-6dB 11 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 CA Gain Mechanisms Multi-carrier scheduling allows for: more bandwidth per user (peak data rate) and better use of high frequency bands (coverage) load balancing/ressource sharing and frequency domain scheduling across carriers PDCP Radio Bearers ROHC ROHC ROHC ROHC Security Security Security Security There is one PDCP and RLC per Radio Bearer. Not visible from RLC on how many CCs the PHY layer transmission is conducted. RLC Segm. ARQ etc... Segm. ARQ etc Logical Channels Segm. ARQ etc... Segm. ARQ etc Dynamic Layer-2 packet scheduling accross multiple CCs supported MAC Scheduling / Priority Handling Multiplexing UE1 Multiplexing UEn HARQ... HARQ HARQ... HARQ Transport Channels Independent HARQ per CC. Thus, HARQ retransmissions shall be send on the same CC as the corresponding original transmission CC1... CCx CC1... CCy Separate transport channel per CC 12 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012

8 CA Signalling Each CC provides reference (CRS) and synchronisation signals (PSS/SSS), as well as system broadcast information (BCCH) specific to that carrier only PCell however carries radio ressource control (RRC) signalling - for bearer setup, CA configuration, mobility measurements, handover, individual SCells can be activated /deactived with MAC control element to save terminal power within7ms Frequency PDCCH OFDM Symbol PRB TTI with 2 slots of 0.5 ms (14 OFDM symbols) Added capacity in control channels for multi-carrier to support more CQI requests, ACK/NACK and CSI reporting, power headroom signalling.. and some simplifications to reduce terminal complexity at the same time reduced need for DPCCH decoding on SCells (e.g. CCE blind decoding on PCell only), control signalling in uplink PCell PUCCH only Cross-carrier scheduling capability of special importance to heterogeneous network operation Time 13 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 Multiple Input Multiple Output (MIMO) SISO Single Input Single Output (antenna system) MU-MIMO Multi-User MIMO SU-MIMO SIngle User MIMO PMI Precoding Matrix Indicator DM-RS Demodulation Reference Signal CSI-RS Channel State Information Reference Signal URS UE specific Reference Signal OCC Orthogonal Cover Codes SRS Sounding Reference Signal CM Cubic Metric SC Single Carrier CQI Channel Quality Indicator Precoding Antennevægtning af TX-antenner 14 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012

9 MIMO The targeted data rates of LTE-A can only be achieved by using advanced Multiple Input Multiple Output (MIMO) antenna techniques Tx 1 2 NT Diversity gain Coherent gain Multiplexing gain 1 2 NR Rx feedback Primarily an evolution of LTE MIMO... Transmit Diversity/Beamforming (Open/Closed Loop) Spatial Multiplexing (Open Loop) Precoded Spatial Multiplexing (Closed Loop).. except for Increased MIMO constellations Uplink Single-User MIMO (SU-MIMO) Flexible Multi-User Scheduling in both downlink and uplink Downlink SISO 2x2 MIMO 4x4 MIMO 8x8 MIMO Uplink SISO 2x2 MIMO 4x4 MIMO 15 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 Downlink MIMO New UE specific reference signal (URS) for demodulation: Includes precoding information for flexible MU-MIMO operation (pairing per ressource) New reference signals replacing Common Reference Signal (CRS): Sparse CSI-RS for feedback generation reduces overhead MU-MIMO Transmit Diversity /Beamforming MIMO UE1 Data UE3 Data Stream 1 CQI, PMI MIMO UE2 Data Stream 2 CQI, PMI, RI enb SU-MIMO Double codebook for 8 TX antennas Data Stream 2 Dynamic switching based on optimised feedback CQI, PMI, RI Data Stream 1 MIMO UE4 16 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012

10 Uplink MIMO New Orthogonal Cover Code (OCC) on top of demodulation reference signal (DM-RS): Allows separation of partially overlapping transmissions for flexible MU-MIMO operation Aperiodic and dynamic SRS reference signal transmisson: Enhances the use of SRS ressources Virtual (MU)-MIMO Transmit diversity Data UE1 Data Stream 1 UE3 Data Stream 2 UE2 enb SU-MIMO Wideband (Closed Loop) Precoding which is Cubic Metric (CM) preserving Data Stream 2 Data Stream 1 MIMO UE4 17 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 Reference signals (DL) Sparse CSI-RS, sent only when in fact needed (overlapped with data transmissions) to reduce overhead for large MIMO constellations Support for 2, 4 and 8 TX antennas The Devil is in the details! URS (DM-RS) sent with precoding, hence no need to signal precoder separately Allows decoupling in spatial and frequency domain scheduling Subcarriers OFDM symbols In uplink, the same scheduling flexibility is introduced using OCC 18 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012

11 Performance QAM Quadrature Amplitude Modulation UL/DL Uplink and Downlink 19 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 UE Categories In addition to the existing 5 categories in rel. 8 (LTE), three new terminal categories added in rel. 10 specifications Peak rate DL/UL Class Class 6 Class 7 Class 8 150/50 Mbps 300/50 Mbps 300/100 Mbps 3000/1500 Mbps Modulation DL 64QAM 64QAM 64QAM 64QAM Modulation UL MIMO DL MIMO UL 16QAM 2x2 No 16QAM 2x2 with CA* 4x4 without CA 16QAM 2x2 with CA* 4x4 without CA 64QAM 8x8 with CA Peak data rates can be achieved in different combinations from CA and MIMO capabilities Cell edge efficiency is about 1% of peak! No Uplink 2x2, MIMO (64QAM): 7.5bps/Hz 2x2 Downlink 4x4 MIMO: 15bps/Hz 4x4 with CA * Carrier aggregation of two 20MHz carriers 20 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012

12 Cell Performance From simulations, average LTE-A cell spectral efficiencies exceed ITU requirements Downlink Uplink 2.6 bps/hz 2x2 MIMO 3.4 bps/hz 4x2 MIMO 4.7 bps/hz 4x4 MIMO 1.4 bps/hz 1x2 MIMO 2.3 bps/hz 2x4 MIMO Much of the gain can be achieved already with LTE rel. 8 (e.g. Multi- User MIMO), but additional MIMO capability and flexibility in scheduling gives additional gain for LTE-A rel. 10 Downlink: UE specific reference signals (URS, or DM-RS), dynamic switching SU/MU-MIMO and optimised double codebook feedback for 8 TX antennas Uplink: SU-MIMO operation, orthogonal cover codes on DM-RS, dynamic aperiodic SRS transmission 21 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 LTE-Advanced; 3GPP Solution for IMT-Advanced", John Wiley, 2012 LTE-A Capability Heterogeneous Networks with small and large cells are essential to cell-edge improvements! secondarily CoMP LTE-A 100MHz FDD HetNet 107GB/sub/month? LTE-A 50MHz FDD HetNet 54GB/sub/month LTE-A 50MHz FDD Network upgrade 15GB/sub/month LTE-A 50MHz FDD 10GB/sub/month LTE 50MHz FDD 6GB/sub/month LTE-Advanced; 3GPP Solution for IMT-Advanced", John Wiley, Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012

13 Heterogeneous Networks (HetNet) ABS Almost Blank Subframe HeNB Home enb CSG = Closed Subscriber Group EIRP = Equivalent Isotropic Radiated Power HeNB = Home base station RE = Range Extension eicic = Enhanced ICIC HII = High Interference Indication ICIC = Inter-Cell Interference Coordination OI = Overload Indication RNTP = Relative Narrow band Transmit Power SON = Self Optimizing Network 23 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 The Combined Benefit of Wide & Local Area Medium area sites Wide Area sites Medium area sites Majority of cell sites today > 300 m > 5 W output power Share of sites growing m 1 5 W Macro Micro Local area Local area Local area Local area Local area Share will grow in future m, < 500 mw Pico, Femto WLAN WLAN WLAN WLAN WLAN License exempt growing & Secondary services emerging m < 100 mw Access Points Benefits of Multi-Layer Deployment Coverage improvement from local area cells in edge or shadowed regions Capacity increase from more transmission points in a given area Tradeoffs involved with Multi-Layer Co-channel deployment needs no additional spectrum but creates interference between the layers and within the same layer >> this interference needs to be controlled for QoS 24 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012

14 HetNet Co-Channel Interference Macro enb: Tx power: 46 dbm Antenna gain: 14 dbi EIRP: 60 dbm Coverage area of macro Pico enb: Tx power: 30 dbm Antenna gain: 5 dbi EIRP: 35 dbm CSG HeNB: Tx power: 20 dbm Antenna gain: 0 dbi EIRP: 20 dbm Macro enb Extended coverage area of pico with RE Coverage area of pico without RE Dominance area of HeNB 25 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 LTE Multi-Cell Coordination via X2 Cell B µ-cell A1 Cell A µ-cell B Each 3GPP releases has added few new features: Release 8 Mobility Management (Handover) ICIC (RNTP, HII, OI) SON Management Release 9 SON enhancements Load balancing Energy Saving Release 10 TDM eicic No X2 between macro and HeNBs (rel.10 includes X2 between HeNBs for some cases) 26 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012

15 TDM eicic Principle Macro-layer Pico-layer Pico-nodes can schedule UEs with larger RE, if not interfered from nonallowed CSG HeNB(s) Almost blank sub-frame (ABS) Sub-frame with normal transmission Pico-UEs with larger RE, close to CSG HeNB(s) are schedula ble (as well as pico-ues without RE). HeNB-layer Macro-eNBs and Pico-eNBs can schedule also users that are close to non-allowed CSG HeNB(s), but not pico-ues with larger RE. 27 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 HetNet is hot Ongoing LTE Rel-12 Study Item 3GPP TR Rel. 12 WI on Carrier Based HetNet ICIC for LTE (rel. 11 WI) Considered Small Cell Scenarios & Objectives Cases with dedicated carrier deployment Rel. 12 SI on Small Cell Enhancements Efficient small cell SON Macro-assisted and standalone small cell solutions Spectrum: e.g. 3.5 GHz for small cells Energy efficient solution Enhanced mobility for dense small cell deployments Rel. 12 WI on HetNet Mobility improvements for LTE (rel. 11 SI) Study of PHY and Architecture enhancements 28 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 Exploiting new carrier type (NCT) Rel. 12 WI on NCT

16 Coordinated Multipoint (CoMP) Transmission and Reception JP Joint Processing 29 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 CoMP Principle A 3-cell CoMP Cooperative/Transmission Set in downlink Cell C Cell B Inter-cell CoMP signaling Cell A (Anchor Cell for the CoMP Cooperative Set) 30 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012

17 CoMP Techniques Categories of CoMP Joint Processing (JP): Data is available at each cell in CoMP cooperating set (CSI and scheduling info, AND data shared among cooperating cells) Joint Transmission: Transmission from multiple points (part of or entire CoMP cooperating set) at a time Dynamic cell selection: Transmission from one point at a time (within CoMP cooperating set) A single point is the transmission point at every subframe; this transmission point can change dynamically within the CoMP cooperating set Coordinated Scheduling/Beamforming (CS/CB): Data is only available at serving cell and transmitted from that point (CSI and scheduling info shared among cooperating cells) The user scheduling/beamforming decisions are made with coordination among cells corresponding to the CoMP cooperating set 31 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 Alike ICIC but faster and including spatial domain Relays 32 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012

18 Relays Relay nodes with LTE backhaul inband or outband for coverage extension/cell edge performance improvement backwards compatible with rel. 8 Access link Relay looks like an enb seen from the UE Backhaul link Relay looks like an additional sector of the macro Relay Nodes Macro enodeb Micro BTS Full enb functionality 33 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 Summary 34 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012

19 Summary Bandwidth has been extended in rel. 10 (LTE-A) up to 100MHz by using backwards compatible carrier aggregation Two carrier downlink CA combinations have been specified and more will come, including uplink CA combinations Support for Multiple Input Multiple Output (MIMO) antennas has been extended in rel. 10 Uplink SU-MIMO up to 4 4 for increasing uplink peak spectral efficiency (up to 15bps/Hz) and enhance average cell spectral efficiency Support of up to 8x8 MIMO in downlink to increase peak spectral efficiency (up to 30bps/Hz) and average cell spectral efficiency The Devil is in the details of the reference signals, which has allowed improvements especially to Multi-User MIMO Multi-layer interference management for Heterogeneous Networks using timedomain enhanced ICIC (eicic) CoMP techniques are still under investigation but included in rel. 11 for downlink and improved for uplink over what is already possible with LTE rel. 8 Transparent relay nodes with wireless LTE backhaul were introduced in rel. 10, primarily for cell edge improvements With these techniques, the target of reaching a peak data rates of more than 1Gbit/s and significant improved average cell spectral efficiency in both UL and DL are achieved 35 Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012 Literature LTE for UMTS; Evolution to LTE-Advanced", John Wiley, 2 nd edition, March 2011, Edited by Harri Holma and Antti Toskala 4G: LTE/LTE-Advanced for Mobile Broadband, Academic Press, 2011, Edited by Erik Dahlman, Stefan Parkvall and Johan Skjold LTE-Advanced; 3GPP Solution for IMT-Advanced", John Wiley, 1 st edition, September 2012, Edited by Harri Holma and Antti Toskala LTE-advanced and 4G wireless communications, IEEE Communications Magazine, vol. 50, no. 2, February Aalborg University/RATE IDA-TTS konference/ Troels B. Sørensen / 4. december 2012