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UMTS Long Term Evolution(LTE)Reiner StuhlfauthReiner.Stuhlfauth@rohde-schwarz.comTraining CentreRohde & Schwarz, GermanySu...
Technology evolution path                                   2005/2006                2007/2008                     2009/20...
3GPP work plan   GERAN                                                                EUTRAN                              ...
Overview 3GPP UMTS evolution                                              HSDPA/                                          ...
Why LTE?Ensuring Long Term Competitiveness of UMTS l LTE is the next UMTS evolution step after HSPA and HSPA+. l LTE is al...
Peak data rates and real average throughput (UL)                    100                                                   ...
Comparison of network latency by technology                    800                                                        ...
Round Trip Time, RTT                                                   •ACK/NACK                                          ...
Major technical challenges in LTE    New radio transmission                                      FDD and schemes (OFDMA / ...
Introduction to UMTS LTE: Key parametersFrequency                  UMTS FDD bands and UMTS TDD bandsRange                 ...
LTE/LTE-A Frequency Bands (FDD) E-UTRA        Uplink (UL) operating band                    Downlink (DL) operating band O...
LTE/LTE-A Frequency Bands (TDD)               Uplink (UL) operating band                        Downlink (DL) operating ba...
Orthogonal Frequency Division Multiple Accessl OFDM is   the modulation scheme for LTE in downlink and  uplink (as referen...
What does it mean to use the radio channel?  Using the radio channel means to deal with aspects like:                     ...
Still the same “mobile” radio problem:Time variant multipath propagation                                                  ...
Multipath channel impulse responseThe CIR consists of L resolvable propagation paths                            L 1      ...
Radio Channel – different aspects to discuss   Bandwidth                                                         or       ...
Frequency selectivity - Coherence Bandwidth                     Here: substitute with single      power          Scalar fa...
Time-Invariant Channel: Scenario                                                                 Fixed ScattererISI: Inter...
Motivation: Single Carrier versus Multi Carrier                                           TSC        |H(f)|     f         ...
Motivation: Single Carrier versus Multi Carrier                                          TSC        |H(f)|   f            ...
What is OFDM? Single carrier transmission, e.g. WCDMA                            Broadband, e.g. 5MHz for WCDMAOrthogonalF...
Idea: Wide/Narrow band conversion           ƒ                     …                                                    S/P...
COFDM                         Mapper                                     X                                            +   ...
OFDM signal generation  00 11 10 10 01 01 11 01 ….                                              e.g. QPSKh*(sinjwt + cosjw...
Fourier Transform, Discrete FT                              Fourier Transform                                             ...
OFDM Implementation with FFT(Fast Fourier Transformation)Transmitter                                                      ...
Inter-Carrier-Interference (ICI)                                                                                          ...
Rectangular Pulse                                                           A(f)                      Convolution         ...
Orthogonality       Orthogonality condition: Δf = 1/Δt                           Δf                November 2012 | LTE Int...
ISI and ICI due to channel       Symbol               l-1                 l               l+1                            ...
ISI and ICI: Guard Intervall        Symbol                l-1                    l                 l+1                    ...
Guard Intervall as Cyclic Prefix                                        Cyclic Prefix        Symbol             l-1       ...
Synchronisation                                    Cyclic Prefix        OFDM Symbol : l  1                          l    ...
DL CP-OFDM signal generation chain     l   OFDM signal generation is based on Inverse Fast Fourier Transform         (IFFT...
OFDM: Pros and Cons          Pros:                 scalable data rate                 efficient use of the available ban...
MIMO =Multiple Input Multiple Output Antennas    November 2012 | LTE Introduction |   37
MIMO is defined by the number of Rx / Tx Antennasand not by the Mode which is supported                                   ...
MIMO modes in LTE                                                          -Spatial Multiplexing-Tx diversity             ...
Diversity – some thoughtsThe SISO channel:                              Fading on the air interface                       ...
Diversity – some thoughts: matched filterThe SISO channel and matched filter (maximum ratio combining):                   ...
Diversity – some thoughts: performance of SISO                 Euclidic distance                   Detector             0 ...
RX DiversityMaximum Ratio Combining depends on different fading of thetwo received signals. In other words decorrelated fa...
Receive diversity gain – SIMO: 1*NRx                                                               Receive antenna 1      ...
TX Diversity: Space Time Coding                                       Fading on the air interface    data                 ...
Space Time Block Coding according to Alamouti                (when no channel information at all available at transmitter)...
MIMO Spatial Multiplexing                                                     C=B*T*ld(1+S/N)          SISO:          Sing...
Spatial multiplexing – capacity aspects Ergodic mean capacity of a SISO channel calculated as:                            ...
Spatial multiplexing – capacity aspects Ergodic mean capacity of a MIMO channel is even worse                           ...
Spatial multiplexing – capacity aspects  Some theoretical ideas:                                                   ...
The MIMO promisel   Channel capacity grows linearly with antennas                   Max Capacity ~ min(NTX, NRX)l   Assum...
Spatial Multiplexing          Coding             Fading on the air interface   data   data               Throughput:      ...
MIMO – capacity calculations, e.g. 2x2 MIMO                                                                      n1       ...
Introduction – Channel Model II                                        Correlation of                                     ...
Spatial Multiplexing prerequisitesDecorrelation is achieved by:l   Decorrelated data content on each spatial stream       ...
MIMO: channel interference + precodingMIMO channel models: different ways to combat against  channel impact:  I.: Receiver...
MIMO: Principle of linear equalizing   R = S*H + nTransmitter will send reference signals or pilot sequenceto enable recei...
Linear equalization – compute power increase                        h11                                 H = h11       SISO...
transmission – reception model                                                 noise  s                                   ...
MIMO – work shift to transmitter                           Channel                       ReceiverTransmitter              ...
MIMO Precoding in LTE (DL)Spatial multiplexing – Code book for precoding      Code book for 2 Tx:       Codebook       Num...
MIMO precoding           precodingAnt1Ant2                                                             t                  ...
MIMO – codebook based precodingPrecodingcodebook                                                         noise      s     ...
MIMO: avoid inter-channel interference – future outlooke.g. linear precoding:                                             ...
MAS: „Dirty Paper“ Coding – future outlookl   Multiple Antenna Signal Processing: „Known Interference“    l Is like NO int...
Spatial Multiplexing          Codeword            Fading on the air interface data          Codeword  data        Spatial ...
Idea of Singular Value Decomposition                                               s1    MIMO       r1           know     ...
Singular Value Decomposition (SVD)                                 h11 h12          r=                      H             ...
Singular Value Decomposition (SVD)                                    r=Hs+n                              H = U Σ (V*)T   ...
MIMO and singular value decomposition SVDReal channel                                                  n1                 ...
MIMO: Signal processing considerations                MIMO transmission can be expressed as                r = Hs+n which ...
MIMO: limited channel feedback    Transmitter                                  H                             Receiver     ...
Cyclic Delay Diversity, CDD                                              A2                               A1              ...
„Open loop“ und „closed loop“ MIMO Open loop (No channel knowledge at transmitter)            r  Hs  n                  ...
MIMO transmission modes                                Transmission mode2                                                 ...
MIMO transmission modes                               the classic:                               1Tx + 1RXTransmission mod...
MIMO transmission modesTransmission mode 2     Transmit      diversity                                            PDCCH in...
MIMO transmission modes                                                     No feedback regarding                         ...
MIMO transmission modes                                               Closed loop MIMO =                                  ...
MIMO transmission modes     Transmission mode 5      Transmit diversity or        Multi User MIMO                         ...
MIMO transmission modes                                       Closed loop MIMO =                                          ...
MIMO transmission modes     Transmission mode 7Transmit diversity or beamforming                                          ...
Beamforming                                                           Closed loop precoded Adaptive Beamforming           ...
Spatial multiplexing vs beamformingSpatial multiplexing increases throughput, but looses coverage                  Novembe...
Spatial multiplexing vs beamforming        Beamforming increases coverage               November 2012 | LTE Introduction |...
Basic OFDM parameter                                                                                     LTE              ...
LTE Downlink:    Downlink slot and (sub)frame structure                     Symbol time, or number of symbols per time slo...
Resource block definition                                           1 slot = 0,5msecResource block=6 or 7 symbolsIn 12 sub...
LTE DownlinkOFDMA time-frequency multiplexing                                                       frequency    QPSK, 16Q...
LTE: new physical channels for data and control         Physical Control Format Indicator Channel PCFICH:            Indic...
LTE Downlink: FDD channel mapping example                      Subcarrier #0               RB             November 2012 | ...
LTE – spectrum flexibility         l LTE physical layer supports any bandwidth from 1.4 MHz           to 20 MHz in steps o...
LTE Downlink:      baseband signal generationcode words                                             layers                ...
Adaptive modulation and coding    Transportation block size       User data                                 FECFlexible ra...
Channel Coding Performance             November 2012 | LTE Introduction |   95
Automatic repeat request, latency aspects                                                      •Transport block size = amo...
HARQ principle: Stop and Wait                                        Δt = Round trip timeTx    Data      Data   Data      ...
HARQ principle: Multitasking                                        Δt = Round trip timeTx    Data      Data   Data       ...
LTE Round Trip Time RTT          n+4               n+4                         n+4                                        ...
HARQ principle: Soft combininglT i is a e am l o h n e co i g     Reception of first transportation block.   Unfortunately...
HARQ principle: Soft combining      l hi i n x m le f cha n l c ing             Reception of retransmitted                ...
HARQ principle: Soft combining         1st transmission with puncturing scheme P1 l T i is a e am l o h n e co i g        ...
Hybrid ARQChase Combining = identical retransmission                                              Turbo Encoder output (36...
Hybrid ARQIncremental Redundancy                                            Turbo Encoder output (36 bits)                ...
LTE Physical Layer:      SC-FDMA in uplinkSingle Carrier Frequency Division        Multiple Access      November 2012 | LT...
LTE Uplink:How to generate an SC-FDMA signal in theory?       Coded symbol rate= R                                        ...
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
LTE Evolution: From Release 8 to Release 10
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LTE Evolution: From Release 8 to Release 10

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This seminar will provide the basics of this fascinating technology. After attending this seminar you will understand OFDM-principles,
including SC-FDMA as the transmission scheme of choice for the LTE uplink. Multiple antenna technology (MIMO) is a fundamental
part of LTE and its impact on the design of device and network architecture will be explained. Further LTE-related physical layer
aspects such as channel structure and cell search will be presented with an overview of the LTE protocol structure.
The second part of the seminar provides an overview of the evolution in LTE towards 3GPP specification Release 9 and 10. This
includes features and methods for location based services like GNSS support or time delay measurements and the concept of
multimedia broadcast. Finally, we’ll introduce the main features of LTE-Advanced (3GPP Release-10) including carrier aggregation for
a larger bandwidth and backbone network aspects like self-organizing networks and relaying concepts.

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Transcript of "LTE Evolution: From Release 8 to Release 10"

  1. 1. UMTS Long Term Evolution(LTE)Reiner StuhlfauthReiner.Stuhlfauth@rohde-schwarz.comTraining CentreRohde & Schwarz, GermanySubject to change – Data without tolerance limits is not binding.R&S® is a registered trademark of Rohde & Schwarz GmbH & Co. KG. Trade names are trademarksof the owners. 2011 ROHDE & SCHWARZ GmbH & Co. KG Test & Measurement Division - Training Center -This folder may be taken outside ROHDE & SCHWARZ facilities.ROHDE & SCHWARZ GmbH reserves the copy right to all of any part of these course notes.Permission to produce, publish or copy sections or pages of these notes or to translate them must firstbe obtained in writing fromROHDE & SCHWARZ GmbH & Co. KG, Training Center, Mühldorfstr. 15, 81671 Munich, Germany
  2. 2. Technology evolution path 2005/2006 2007/2008 2009/2010 2011/2012 2013/2014GSM/ EDGE, 200 kHz EDGEevo VAMOS DL: 473 kbps DL: 1.9 Mbps Double SpeechGPRS UL: 473 kbps UL: 947 kbps Capacity UMTS HSDPA, 5 MHz HSPA+, R7 HSPA+, R8 HSPA+, R9 HSPA+, R10 DL: 2.0 Mbps DL: 14.4 Mbps DL: 28.0 Mbps DL: 42.0 Mbps DL: 84 Mbps DL: 84 Mbps UL: 2.0 Mbps UL: 2.0 Mbps UL: 11.5 Mbps UL: 11.5 Mbps UL: 23 Mbps UL: 23 Mbps HSPA, 5 MHz DL: 14.4 Mbps UL: 5.76 Mbps LTE (4x4), R8+R9, 20MHz LTE-Advanced R10 DL: 300 Mbps DL: 1 Gbps (low mobility) UL: 75 Mbps UL: 500 Mbps 1xEV-DO, Rev. 0 1xEV-DO, Rev. A 1xEV-DO, Rev. B cdma DO-Advanced 1.25 MHz 1.25 MHz 5.0 MHz DL: 32 Mbps and beyond 2000 DL: 2.4 Mbps DL: 3.1 Mbps DL: 14.7 Mbps UL: 12.4 Mbps and beyond UL: 153 kbps UL: 1.8 Mbps UL: 4.9 Mbps Fixed WiMAX Mobile WiMAX, 802.16e Advanced Mobile scalable bandwidth Up to 20 MHz WiMAX, 802.16m 1.25 … 28 MHz DL: 75 Mbps (2x2) DL: up to 1 Gbps (low mobility) typical up to 15 Mbps UL: 28 Mbps (1x2) UL: up to 100 Mbps November 2012 | LTE Introduction | 2
  3. 3. 3GPP work plan GERAN EUTRAN New RAN Phase 1Phase 2, 2+ UTRAN Rel. 95 … Rel. 97 Rel.7 Rel. 99 Up from Rel. 8 … Rel. 7 Rel. 9 Also contained in Rel. 10 Evolution November 2012 | LTE Introduction | 3
  4. 4. Overview 3GPP UMTS evolution HSDPA/ LTE and LTE- WCDMA WCDMA HSPA+ HSUPA HSPA+ advanced 3GPP 3GPP Study 3GPP release 3GPP Release 99/4 3GPP Release 5/6 3GPP Release 7 3GPP Release 8 Item initiated Release 10 App. year of 2005/6 (HSDPA)network rollout 2003/4 2008/2009 2010 2007/8 (HSUPA) Downlink LTE: 150 Mbps* (peak) 100 Mbps high mobility 384 kbps (typ.) 384 kbps (typ.) 14 Mbps (peak) 28 Mbps (peak) HSPA+: 42 Mbps (peak) 28 Mbps (peak) data rate 1 Gbps low mobility Uplink LTE: 75 Mbps (peak) 128 kbps (typ.) 128 kbps (typ.) 5.7 Mbps (peak) 11 Mbps (peak) HSPA+: 11 Mbps (peak) 11 Mbps (peak) data rate Round Trip Time ~ 150 ms < 100 ms < 50 ms LTE: ~10 ms *based on 2x2 MIMO and 20 MHz operation November 2012 | LTE Introduction | 4
  5. 5. Why LTE?Ensuring Long Term Competitiveness of UMTS l LTE is the next UMTS evolution step after HSPA and HSPA+. l LTE is also referred to as EUTRA(N) = Evolved UMTS Terrestrial Radio Access (Network). l Main targets of LTE: l Peak data rates of 100 Mbps (downlink) and 50 Mbps (uplink) l Scaleable bandwidths up to 20 MHz l Reduced latency l Cost efficiency l Operation in paired (FDD) and unpaired (TDD) spectrum November 2012 | LTE Introduction | 5
  6. 6. Peak data rates and real average throughput (UL) 100 58 11,5 15 10 5,76Data rate in Mbps 5 2 2 1,8 2 0,947 1 0,473 0,7 0,5 0,174 0,153 0,2 0,1 0,1 0,1 0,1 0,03 0,01 GPRS EDGE 1xRTT WCDMA E-EDGE 1xEV-DO 1xEV-DO HSPA HSPA+ LTE 2x2 (Rel. 97) (Rel. 4) (Rel. 99/4) (Rel. 7) Rev. 0 Rev. A (Rel. 5/6) (Rel. 7) (Rel. 8) Technology max. peak UL data rate [Mbps] max. avg. UL throughput [Mbps] November 2012 | LTE Introduction | 6
  7. 7. Comparison of network latency by technology 800 158 160 710 700 140 600 120 3G / 3.5G / 3.9G latency2G / 2.5G latency 500 100 85 400 80 320 70 300 60 46 190 200 40 100 20 30 0 0 GPRS EDGE WCDMA HSDPA HSUPA E-EDGE HSPA+ LTE (Rel. 97) (Rel. 4) (Rel. 99/4) (Rel. 5) (Rel. 6) (Rel. 7) (Rel. 7) (Rel. 8) Technology Total UE Air interface Node B Iub RNC Iu + core Internet November 2012 | LTE Introduction | 7
  8. 8. Round Trip Time, RTT •ACK/NACK generation in RNC MSC TTI Iub/Iur Iu ~10msec Serving SGSN RNC Node B TTI =1msec MME/SAE Gateway eNode B •ACK/NACK generation in node B November 2012 | LTE Introduction | 8
  9. 9. Major technical challenges in LTE New radio transmission FDD and schemes (OFDMA / SC-FDMA) TDD mode MIMO multiple antenna Throughput / data rate schemes requirements Timing requirements Multi-RAT requirements (1 ms transm.time interval) (GSM/EDGE, UMTS, CDMA) Scheduling (shared channels, System Architecture HARQ, adaptive modulation) Evolution (SAE) November 2012 | LTE Introduction | 9
  10. 10. Introduction to UMTS LTE: Key parametersFrequency UMTS FDD bands and UMTS TDD bandsRange 1.4 MHz 3 MHz 5 MHz 10 MHz 15 MHz 20 MHz Channel bandwidth, 1 Resource 6 15 25 50 75 100 Block=180 kHz Resource Resource Resource Resource Resource Resource Blocks Blocks Blocks Blocks Blocks BlocksModulation Downlink: QPSK, 16QAM, 64QAMSchemes Uplink: QPSK, 16QAM, 64QAM (optional for handset) Downlink: OFDMA (Orthogonal Frequency Division Multiple Access)Multiple Access Uplink: SC-FDMA (Single Carrier Frequency Division Multiple Access) Downlink: Wide choice of MIMO configuration options for transmit diversity, spatialMIMO multiplexing, and cyclic delay diversity (max. 4 antennas at base station and handset)technology Uplink: Multi user collaborative MIMO Downlink: 150 Mbps (UE category 4, 2x2 MIMO, 20 MHz)Peak Data Rate 300 Mbps (UE category 5, 4x4 MIMO, 20 MHz) Uplink: 75 Mbps (20 MHz) November 2012 | LTE Introduction | 10
  11. 11. LTE/LTE-A Frequency Bands (FDD) E-UTRA Uplink (UL) operating band Downlink (DL) operating band Operating BS receive UE transmit BS transmit UE receive Duplex Mode Band FUL_low – FUL_high FDL_low – FDL_high 1 1920 MHz – 1980 MHz 2110 MHz – 2170 MHz FDD 2 1850 MHz – 1910 MHz 1930 MHz – 1990 MHz FDD 3 1710 MHz – 1785 MHz 1805 MHz – 1880 MHz FDD 4 1710 MHz – 1755 MHz 2110 MHz – 2155 MHz FDD 5 824 MHz – 849 MHz 869 MHz – 894MHz FDD 6 830 MHz – 840 MHz 875 MHz – 885 MHz FDD 7 2500 MHz – 2570 MHz 2620 MHz – 2690 MHz FDD 8 880 MHz – 915 MHz 925 MHz – 960 MHz FDD 9 1749.9 MHz – 1784.9 MHz 1844.9 MHz – 1879.9 MHz FDD 10 1710 MHz – 1770 MHz 2110 MHz – 2170 MHz FDD 11 1427.9 MHz – 1452.9 MHz 1475.9 MHz – 1500.9 MHz FDD 12 698 MHz – 716 MHz 728 MHz – 746 MHz FDD 13 777 MHz – 787 MHz 746 MHz – 756 MHz FDD 14 788 MHz – 798 MHz 758 MHz – 768 MHz FDD 17 704 MHz – 716 MHz 734 MHz – 746 MHz FDD 18 815 MHz – 830 MHz 860 MHz – 875 MHz FDD 19 830 MHz – 845 MHz 875 MHz – 890 MHz FDD 20 832 MHz - 862 MHz 791 MHz - 821 MHz FDD 21 1447.9 MHz - 1462.9 MHz 1495.9 MHz - 1510.9 MHz FDD 22 3410 MHz - 3500 MHz 3510 MHz - 3600 MHz FDD November 2012 | LTE Introduction | 11
  12. 12. LTE/LTE-A Frequency Bands (TDD) Uplink (UL) operating band Downlink (DL) operating band E-UTRA BS receive UE transmit BS transmit UE receive Operating Duplex Mode Band FUL_low – FUL_high FDL_low – FDL_high 33 1900 MHz – 1920 MHz 1900 MHz – 1920 MHz TDD 34 2010 MHz – 2025 MHz 2010 MHz – 2025 MHz TDD 35 1850 MHz – 1910 MHz 1850 MHz – 1910 MHz TDD 36 1930 MHz – 1990 MHz 1930 MHz – 1990 MHz TDD 37 1910 MHz – 1930 MHz 1910 MHz – 1930 MHz TDD 38 2570 MHz – 2620 MHz 2570 MHz – 2620 MHz TDD 39 1880 MHz – 1920 MHz 1880 MHz – 1920 MHz TDD 40 2300 MHz – 2400 MHz 2300 MHz – 2400 MHz TDD 3400 MHz – 3400 MHz – 41 TDD 3600MHz 3600MHz November 2012 | LTE Introduction | 12
  13. 13. Orthogonal Frequency Division Multiple Accessl OFDM is the modulation scheme for LTE in downlink and uplink (as reference)l Some technical explanation about our physical base: radio link aspects November 2012 | LTE Introduction | 13
  14. 14. What does it mean to use the radio channel? Using the radio channel means to deal with aspects like: C A D B Transmitter Receiver MPPTime variant channel Doppler effectFrequency selectivity attenuation November 2012 | LTE Introduction | 14
  15. 15. Still the same “mobile” radio problem:Time variant multipath propagation A: free space A: free space B: reflection B: reflection C C: diffraction C: diffraction A D: scattering D: scattering D B Transmitter ReceiverMultipath Propagation reflection: object is largeand Doppler shift compared to wavelength scattering: object is small or its surface irregular November 2012 | LTE Introduction | 15
  16. 16. Multipath channel impulse responseThe CIR consists of L resolvable propagation paths L 1 h  , t    ai  t  e     i  ji  t  i 0 path attenuation path phase path delay |h|²  delay spread November 2012 | LTE Introduction | 16
  17. 17. Radio Channel – different aspects to discuss Bandwidth or Wideband Narrowband Symbol duration or t t Short symbol Long symbol duration durationChannel estimation: Frequency?Pilot mapping Time? frequency distance of pilots? Repetition rate of pilots? November 2012 | LTE Introduction | 17
  18. 18. Frequency selectivity - Coherence Bandwidth Here: substitute with single power Scalar factor = 1-tap Frequency selectivity How to combat channel influence? f Narrowband = equalizer Can be 1 - tap Wideband = equalizerHere: find Must be frequency selectiveMath. Equationfor this curve November 2012 | LTE Introduction | 18
  19. 19. Time-Invariant Channel: Scenario Fixed ScattererISI: Inter Symbol Interference: Happens, when Delay spread > Symbol time Successive Fixed Receiver symbols Transmitter will interfere Channel Impulse Response, CIR Transmitter Receiver collision Signal Signal t t Delay Delay spread →time dispersive November 2012 | LTE Introduction | 19
  20. 20. Motivation: Single Carrier versus Multi Carrier TSC |H(f)| f Source: Kammeyer; Nachrichtenübertragung; 3. Auflage 1 B TSC B t |h(t)| t l Time Domain l Delay spread > Symboltime TSC → Inter-Symbol-Interference (ISI) → equalization effort l Frequency Domain l Coherence Bandwidth Bc < Systembandwidth B → Frequency Selective Fading → equalization effort November 2012 | LTE Introduction | 20
  21. 21. Motivation: Single Carrier versus Multi Carrier TSC |H(f)| f Source: Kammeyer; Nachrichtenübertragung; 3. Auflage 1 B B TSC t |h(t)| f t |H(f)| B 1 f   B N TMC t TMC  N  TSC November 2012 | LTE Introduction | 21
  22. 22. What is OFDM? Single carrier transmission, e.g. WCDMA Broadband, e.g. 5MHz for WCDMAOrthogonalFrequencyDivisionMultiplex Several 100 subcarriers, with x kHz spacing November 2012 | LTE Introduction | 22
  23. 23. Idea: Wide/Narrow band conversion ƒ … S/P … …H(ƒ) t / Tb t / Ts h(τ) h(τ) „Channel Memory“ τ τ One high rate signal: N low rate signals: Frequency selective fading Frequency flat fading November 2012 | LTE Introduction | 23
  24. 24. COFDM Mapper X + XDatawith OFDMFEC Σ ..... symboloverhead Mapper X + X November 2012 | LTE Introduction | 24
  25. 25. OFDM signal generation 00 11 10 10 01 01 11 01 …. e.g. QPSKh*(sinjwt + cosjwt) h*(sinjwt + cosjwt) => Σ h * (sin.. + cos…) Frequency time OFDM symbol duration Δt 2012 | November LTE Introduction | 25
  26. 26. Fourier Transform, Discrete FT Fourier Transform  H ( f )   h(t )e 2 j ft dt ;   h(t )   H ( f )e  2 j ft df ;  Discrete Fourier Transform (DFT) N 1 N 1 N 1 n n H n   hk e 2 j k n / N   hk cos(2  k )  j  hk sin(2  k ); k 0 k 0 N k 0 N N 1  2 j k n 1 hk  N H e n 0 n N ; November 2012 | LTE Introduction | 26
  27. 27. OFDM Implementation with FFT(Fast Fourier Transformation)Transmitter Channel d(0) Map IDFT NFFT d(1) P/S S/Pb (k ) Map . s(n) . . d(FFT-1) Map h(n)Receiver d(0) Demap n(n) DFT NFFT d(1) P/Sˆ k S/Pb( ) Demap . r(n) . . d(FFT-1) Demap November 2012 | LTE Introduction | 27
  28. 28. Inter-Carrier-Interference (ICI) 10 SMC  f  0 -10 -20  -30 xx S -40 -50 -60 -70 -1 -0.5 0 0.5 1   f-2 f-1 f0 f1 f2 f Problem of MC - FDM ICI Overlapp of neighbouring subcarriers → Inter Carrier Interference (ICI). Solution “Special” transmit gs(t) and receive filter gr(t) and frequencies fk allows orthogonal subcarrier → Orthogonal Frequency Division Multiplex (OFDM) November 2012 | LTE Introduction | 28
  29. 29. Rectangular Pulse A(f) Convolution sin(x)/x t f Δt Δf time frequency November 2012 | LTE Introduction | 29
  30. 30. Orthogonality Orthogonality condition: Δf = 1/Δt Δf November 2012 | LTE Introduction | 30
  31. 31. ISI and ICI due to channel Symbol l-1 l l+1  h  n n Receiver DFT Window Delay spread fade in (ISI) fade out (ISI) November 2012 | LTE Introduction | 31
  32. 32. ISI and ICI: Guard Intervall Symbol l-1 l l+1  h  n TG  Delay Spread n Receiver DFT Window Delay spread Guard Intervall guarantees the supression of ISI! November 2012 | LTE Introduction | 32
  33. 33. Guard Intervall as Cyclic Prefix Cyclic Prefix Symbol l-1 l l+1  h  n TG  Delay Spread n Receiver DFT Window Delay spread Cyclic Prefix guarantees the supression of ISI and ICI! November 2012 | LTE Introduction | 33
  34. 34. Synchronisation Cyclic Prefix OFDM Symbol : l  1 l l 1 CP CP CP CP Metric - Search window ~ n November 2012 | LTE Introduction | 34
  35. 35. DL CP-OFDM signal generation chain l OFDM signal generation is based on Inverse Fast Fourier Transform (IFFT) operation on transmitter side: Data QAM N Useful 1:N OFDM Cyclic prefixsource Modulator symbol IFFT N:1 OFDM symbols insertion streams symbols Frequency Domain Time Domain l On receiver side, an FFT operation will be used. November 2012 | LTE Introduction | 35
  36. 36. OFDM: Pros and Cons Pros:  scalable data rate  efficient use of the available bandwidth  robust against fading  1-tap equalization in frequency domain Cons:  high crest factor or PAPR. Peak to average power ratio  very sensitive to phase noise, frequency- and clock-offset  guard intervals necessary (ISI, ICI) → reduced data rate November 2012 | LTE Introduction | 36
  37. 37. MIMO =Multiple Input Multiple Output Antennas November 2012 | LTE Introduction | 37
  38. 38. MIMO is defined by the number of Rx / Tx Antennasand not by the Mode which is supported Mode1 1 SISO Typical todays wireless Communication System Single Input Single Output Transmit Diversity1 1 MISO l Maximum Ratio Combining (MRC) l Matrix A also known as STCM Multiple Input Single Output l Space Time / Frequency Coding (STC / SFC) Receive Diversity 1 1 SIMO l Maximum Ratio Combining (MRC) Single Input Multiple Output Receive / Transmit Diversity M Spatial Multiplexing (SM) also known as: l Space Division Multiplex (SDM) l True MIMO 1 1 MIMO l Single User MIMO (SU-MIMO) Multiple Input Multiple Output l Matrix B M M Space Division Multiple Access (SDMA) also known as: l Multi User MIMO (MU MIMO) l Virtual MIMO Definition is seen from Channel l Collaborative MIMO Multiple In = Multiple Transmit Antennas Beamforming November 2012 | LTE Introduction | 38
  39. 39. MIMO modes in LTE -Spatial Multiplexing-Tx diversity -Multi-User MIMO-Beamforming-Rx diversity Increased Increased Throughput per Throughput at Better S/N UE Node B November 2012 | LTE Introduction | 39
  40. 40. Diversity – some thoughtsThe SISO channel: Fading on the air interface h11 transmit signal s received signal r j r  h11  s  n  h11 e s  n Amplitude phase scaling rotation The transmit signal is modified in amplitude and phase plus additional noise November 2012 | LTE Introduction | 40
  41. 41. Diversity – some thoughts: matched filterThe SISO channel and matched filter (maximum ratio combining): h11 h*11 received signal r estimated signal ř transmit signal s ~  h* r  h* h s  h* n  h e  j h e j s  h* n  h 2 s  h* n r 11 11 11 11 11 11 11 11 11 Idea: matched filter multiplies received signal with conjugate of channel -> maximizes SNR Transmitted signal s is estimated as: ~ r ~ s 2 h11 November 2012 | LTE Introduction | 41
  42. 42. Diversity – some thoughts: performance of SISO Euclidic distance Detector 0 threshold 1 Decay with SNR, only one channel available - > fading will deteriorate noise amplitude Bit error rate distribution Modulation Bit error Data rate = bits scheme probability per symbol BPSK 1/(4*SNR) 1 QPSK 1/(2*SNR) 2 16 QAM 5/(2*SNR) 4 November 2012 | LTE Introduction | 42
  43. 43. RX DiversityMaximum Ratio Combining depends on different fading of thetwo received signals. In other words decorrelated fading channels November 2012 | LTE Introduction | 43
  44. 44. Receive diversity gain – SIMO: 1*NRx Receive antenna 1 time r1=h11s+n1Transmit s NTx NRx h11antenna Receive antenna 2 h12 r2=h12s+n2 h1NRx Receive antenna NRx rnrx=h1nrxs+nnrx ~  h* s  h* s  ...  h* s r 11 1 12 2 1nRX nRX Said:   h11  h12  ...  h1nRx  s  h n  h n  ...  h 2 2 2   * * * nnRx diversity   11 1 12 2 1nRx order nRx signal after maximum ratio combining 1 Pe ~ Probability for errors SNR nRx November 2012 | LTE Introduction | 44
  45. 45. TX Diversity: Space Time Coding Fading on the air interface data The same signal is transmitted at differnet antennas space Aim: increase of S/N ratio  increase of throughput  s1  s2  *S2   *  Alamouti Coding = diversity gain time approaches  s2 s1  RX diversity gain with MRRC! Alamouti Coding -> benefit for mobile communications November 2012 | LTE Introduction | 45
  46. 46. Space Time Block Coding according to Alamouti (when no channel information at all available at transmitter) d e1  h1  r1  h2  r2   h1 ²  h2 ²  d1  n1 * * From slide before: d e 2  h2  r1  h1  r2   h1 ²  h2 ²  d 2  n2 * * Probability for errors (Alamouti) 1 Pe ~ SNR 2 Compare with Rx diversityAlamouti coding is full diversity gainand full rate, but it only works for 1 Pe ~2 antennas SNR nRx(due to Alamouti matrix is orthogonal) November 2012 | LTE Introduction | 46
  47. 47. MIMO Spatial Multiplexing C=B*T*ld(1+S/N) SISO: Single Input Single OutputHigher capacity without additional spectrum! MIMO: S C   T  B  ld (1  ) ? min( N T , N R ) i i i 1 N Multiple Input i Multiple Output Increasing capacity per cell November 2012 | LTE Introduction | 47
  48. 48. Spatial multiplexing – capacity aspects Ergodic mean capacity of a SISO channel calculated as: h11 2 C  EH {log 2 (1   h11 )} r  s  h11  n Received signal r with sent signal s, channel h11 and AWGN with σ=n P   represents the signal to noise ratio SNR 2 at the receiver branchOr simplified:  S With B = bandwidth C  B * log 2 1   and S/N = signal to  N noise ratio November 2012 | LTE Introduction | 48
  49. 49. Spatial multiplexing – capacity aspects Ergodic mean capacity of a MIMO channel is even worse        H   C  EH l og 2 det  I nR  HH         nT    n1 n1 n2 n2InR is an Identity matrix with size nT x nR nT nR r  sH nHH is the Hermetian complex Received signal r with sent signal s, channel H and AWGN with σ=n November 2012 | LTE Introduction | 49
  50. 50. Spatial multiplexing – capacity aspects Some theoretical ideas:       H   C  EH l og 2 det  I nR  HH    EH nR * log 2 1          nT    We increase to number of HH H lim  I nR transmit antennas to ∞, and see: nT  nTSo the result is, if the number of Tx antennas is infinity, thecapacity depends on the number of Rx antennas:After this heavy mathematics the result: If we increase thenumber of Tx and Rx antennas, we can increase the capacity! November 2012 | LTE Introduction | 50
  51. 51. The MIMO promisel Channel capacity grows linearly with antennas  Max Capacity ~ min(NTX, NRX)l Assumptions  l Perfect channel knowledge l Spatially uncorrelated fadingl Reality  l Imperfect channel knowledge l Correlation ≠ 0 and rather unknown November 2012 | LTE Introduction | 51
  52. 52. Spatial Multiplexing Coding Fading on the air interface data data Throughput: <200% 200% 100% Spatial Multiplexing: We increase the throughput but we also increase the interference! November 2012 | LTE Introduction | 52
  53. 53. MIMO – capacity calculations, e.g. 2x2 MIMO n1 h11 s1 r1 h12 n2 h21 s2 r2 h22This results in the equations: Or as matrix: r1 = s1*h11 + s2*h21 + n1  r1   h11 h12   s1   n1  r2 = s2*h22 + s1*h12 + n2 r   h  *  s   n   2   21 h22   2   2  100% General written as: r = s*H +n To solve this equation, we have to know H November 2012 | LTE Introduction | 53
  54. 54. Introduction – Channel Model II Correlation of propagation h11 pathes h21 s1 r1 hMR1 h12 s2 h22 r2 estimates Transmitter hMR2 Receiver h1MT h2MT NTx NRx sNTx hMRMT rNRx antennas antennas s H r Rank indicator Capacity ~ min(NTX, NRX) → max. possible rank! But effective rank depends on channel, i.e. the correlation situation of H November 2012 | LTE Introduction | 54
  55. 55. Spatial Multiplexing prerequisitesDecorrelation is achieved by:l Decorrelated data content on each spatial stream difficultl Large antenna spacing Channel conditionl Environment with a lot of scatters near the antenna (e.g. MS or indoor operation, but not BS) Technicall Precoding assist But, also possible that decorrelationl Cyclic Delay Diversity is not given November 2012 | LTE Introduction | 55
  56. 56. MIMO: channel interference + precodingMIMO channel models: different ways to combat against channel impact: I.: Receiver cancels impact of channel II.: Precoding by using codebook. Transmitter assists receiver in cancellation of channel impact III.: Precoding at transmitter side to cancel channel impact November 2012 | LTE Introduction | 56
  57. 57. MIMO: Principle of linear equalizing R = S*H + nTransmitter will send reference signals or pilot sequenceto enable receiver to estimate H. n H-1 Rx s r ^ r Tx H LE The receiver multiplies the signal r with the Hermetian conjugate complex of the transmitting function to eliminate the channel influence. November 2012 | LTE Introduction | 57
  58. 58. Linear equalization – compute power increase h11 H = h11 SISO: Equalizer has to estimate 1 channel h11 h12 h11 h12 H= h21 h22 h21 h22 2x2 MIMO: Equalizer has to estimate 4 channels November 2012 | LTE Introduction | 58
  59. 59. transmission – reception model noise s + r A H R transmitter channel receiver •Modulation, •detection, •Power •estimation •„precoding“, •Eliminating channel •etc. Linear equalization impact at receiver is not •etc. very efficient, i.e. noise can not be cancelled November 2012 | LTE Introduction | 59
  60. 60. MIMO – work shift to transmitter Channel ReceiverTransmitter November 2012 | LTE Introduction | 60
  61. 61. MIMO Precoding in LTE (DL)Spatial multiplexing – Code book for precoding Code book for 2 Tx: Codebook Number of layers  index 1 2 Additional multiplication of the 1  1 1 0 0 0      2 0 1  layer symbols with codebook 0  1 1 1  entry 1 1      2 1 1 1 1 1 1 1  2    2 1 2  j  j 1 1 3   - 2 1 1 1  4   - 2  j 1 1 5   - 2  j  November 2012 | LTE Introduction | 61
  62. 62. MIMO precoding precodingAnt1Ant2 t +  1 2 1 ∑ t + 1 precoding -1 1 ∑=0 t t November 2012 | LTE Introduction | 62
  63. 63. MIMO – codebook based precodingPrecodingcodebook noise s + r A H R transmitter channel receiver Precoding Matrix Identifier, PMICodebook based precoding createssome kind of „beamforming light“ November 2012 | LTE Introduction | 63
  64. 64. MIMO: avoid inter-channel interference – future outlooke.g. linear precoding: V1,k Y=H*F*S+V S Link adaptation + Transmitter H Space time F receiver xk + yk VM,k Feedback about H Idea: F adapts transmitted signal to current channel conditions November 2012 | LTE Introduction | 64
  65. 65. MAS: „Dirty Paper“ Coding – future outlookl Multiple Antenna Signal Processing: „Known Interference“ l Is like NO interference l Analogy to writing on „dirty paper“ by changing ink color accordingly „Known „Known „Known „Known Interference Interference Interference Interference is No is No is No is No Interference“ Interference“ Interference“ Interference“ November 2012 | LTE Introduction | 65
  66. 66. Spatial Multiplexing Codeword Fading on the air interface data Codeword data Spatial Multiplexing: We like to distinguish the 2 useful Propagation passes: How to do that? => one idea is SVD November 2012 | LTE Introduction | 66
  67. 67. Idea of Singular Value Decomposition s1 MIMO r1 know r=Hs+n s2 r2 channel H Singular Value Decomposition ~ s1 ~ r1 SISO wanted ~ ~ s2 r2 ~ ~ ~ r=Ds+n channel D November 2012 | LTE Introduction | 67
  68. 68. Singular Value Decomposition (SVD) h11 h12 r= H s + n h21 h22 h11 h0 d1 12 r= U H (V*)T s + n h0 h22 21 d2 d1 0 (U*)T r= (U*)T U D (V*)T s + (U*)T n 0 d2 ~ = (U*)T U d1 0 ~ ~ (U*)T r D (V*)T s + (U*)T n 0 d2 November 2012 | LTE Introduction | 68
  69. 69. Singular Value Decomposition (SVD) r=Hs+n H = U Σ (V*)T U = [u1,...,un] eigenvectors of (H*)T H V = [v1,...,vm] eigenvectors of H (H*)T  1 0 0  0  i eigenvalues of (H*)T H  0 0   2  0 0 3  singular values  i  i  0  0  ~ = (U*)T r r ~ ~= Σ s + n r ~ ~ s = (V*)T s ~ = (U*)T n n November 2012 | LTE Introduction | 69
  70. 70. MIMO and singular value decomposition SVDReal channel n1 h11 s1 r1 h12 n2 h21 s2 r2 h22Channel model with SVD n1 s1 σ1 r1 U Σ VH n2 s2 σ2 r2 SVD transforms channel into k parallel AWGN channels November 2012 | LTE Introduction | 70
  71. 71. MIMO: Signal processing considerations MIMO transmission can be expressed as r = Hs+n which is, using SVD = UΣVHs+n n1s1 σ1 r1 V U Σ VH n2 UHs2 σ2 r2 Imagine we do the following: 1.) Precoding at the transmitter: Instead of transmitting s, the transmitter sends s = V*s 2.) Signal processing at the receiver Multiply the received signal with UH, r = r*UHSo after signal processing the whole signal can be expressed as:r =UH*(UΣVHVs+n)=UHU Σ VHVs+UHn = Σs+UHn =InTnT =InTnT November 2012 | LTE Introduction | 71
  72. 72. MIMO: limited channel feedback Transmitter H Receiver n1 s1 σ1 r1 V U Σ VH n2 UH s2 σ2 r2 Idea 1: Rx sends feedback about full H to Tx. -> but too complex, -> big overhead -> sensitive to noise and quantization effects Idea 2: Tx does not need to know full H, only unitary matrix V -> define a set of unitary matrices (codebook) and find one matrix in the codebook that maximizes the capacity for the current channel H -> these unitary matrices from the codebook approximate the singular vector structure of the channel => Limited feedback is almost as good as ideal channel knowledge feedback November 2012 | LTE Introduction | 72
  73. 73. Cyclic Delay Diversity, CDD A2 A1 Amp litud D eTransmitter B Delay Spread Time Delay Multipath propagation precoding +  + precoding Time No multipath propagation Delay November 2012 | LTE Introduction | 73
  74. 74. „Open loop“ und „closed loop“ MIMO Open loop (No channel knowledge at transmitter) r  Hs  n Channel Status, CSI Rank indicator Closed loop (With channel knowledge at transmitter r  HWs  n Channel Status, CSI Rank indicatorAdaptive Precoding matrix („Pre-equalisation“)Feedback from receiver needed (closed loop) November 2012 | LTE Introduction | 74
  75. 75. MIMO transmission modes Transmission mode2 Transmission mode3 TX diversityTransmission mode1 Open-loop spatial SISO multiplexing 7 transmission Transmission mode4 Transmission mode7 Closed-loop spatial modes are SISO, port 5 multiplexing defined = beamforming in TDD Transmission mode6 Transmission mode5 Closed-loop Multi-User MIMO spatial multiplexing, using 1 layerTransmission mode is given by higher layer IE: AntennaInfo November 2012 | LTE Introduction | 75
  76. 76. MIMO transmission modes the classic: 1Tx + 1RXTransmission mode1 antenna SISO PDCCH indication via DCI format 1 or 1A PDSCH transmission via single antenna port 0 No feedback regarding antenna selection or precoding needed November 2012 | LTE Introduction | 76
  77. 77. MIMO transmission modesTransmission mode 2 Transmit diversity PDCCH indication via DCI format 1 or 1A Codeword is sent redundantly over several streams1 codeword PDSCH transmission via 2 Or 4 antenna ports No feedback regarding antenna selection or precoding needed November 2012 | LTE Introduction | 77
  78. 78. MIMO transmission modes No feedback regarding antenna selection or Transmission mode 3 precoding needed Transmit diversity or Open loop spatial multiplexing PDCCH indication via DCI format 1A 1 codeword PDSCH transmission Via 2 or 4 antenna ports PDCCH indication via DCI format 2A 1 2codeword codewords PMI feedback PDSCH spatial multiplexing PDSCH spatial multiplexing, using CDD with 1 layer November 2012 | LTE Introduction | 78
  79. 79. MIMO transmission modes Closed loop MIMO = UE feedback needed regarding Transmission mode 4 precoding and antenna Transmit diversity or Closed loop selection spatial multiplexing PDCCH indication via DCI format 1A 1 codeword PDSCH transmission Via 2 or 4 antenna ports PDCCH indication via DCI format 2 precoding precoding 1 2codeword codewords PMI feedback PMI feedback PDSCH spatial multiplexing PDSCH spatial multiplexing with 1 layer November 2012 | LTE Introduction | 79
  80. 80. MIMO transmission modes Transmission mode 5 Transmit diversity or Multi User MIMO PDCCH indication via DCI format 1A 1 codeword PDSCH transmission Via 2 or 4 antenna ports PUSCH UE1Codeword PDCCH indication via DCI format 1D UE2 PDSCH multiplexing to several UEs.Codeword PUSCH multiplexing in Uplink November 2012 | LTE Introduction | 80
  81. 81. MIMO transmission modes Closed loop MIMO = UE feedback needed regarding Transmission mode 6 precoding and antennaTransmit diversity or Closed loop selection spatial multiplexing with 1 layer PDCCH indication via DCI format 1A1 codeword PDSCH transmission via 2 or 4 antenna ports PDCCH indication via DCI format 1B Codeword is split into 1 streams, both streams havecodeword to be combined feedback PDSCH spatial multiplexing, only 1 codeword November 2012 | LTE Introduction | 81
  82. 82. MIMO transmission modes Transmission mode 7Transmit diversity or beamforming PDCCH indication via DCI format 1A1 codeword PDSCH transmission via 1, 2 or 4 antenna ports PDCCH indication via DCI format 1 1codeword PDSCH sent over antenna port 5 = beamforming November 2012 | LTE Introduction | 82
  83. 83. Beamforming Closed loop precoded Adaptive Beamforming beamforming•Classic way •Kind of MISO with channel knowledge at transmitter•Antenna weights to adjust beam •Precoding based on feedback•Directional characteristics •No specific antenna•Specific antenna array geometrie array geometrie•Dedicated pilots required •Common pilots are sufficient November 2012 | LTE Introduction | 83
  84. 84. Spatial multiplexing vs beamformingSpatial multiplexing increases throughput, but looses coverage November 2012 | LTE Introduction | 84
  85. 85. Spatial multiplexing vs beamforming Beamforming increases coverage November 2012 | LTE Introduction | 85
  86. 86. Basic OFDM parameter LTE 1 f  15 kHz  T Fs  N FFT  f N FFT Fs   3.84Mcps 256 f NFFT  2048 Coded symbol rate= R Sub-carrier CP S/P Mapping IFFT insertion N TX Data symbols Size-NFFT November 2012 | LTE Introduction | 86
  87. 87. LTE Downlink: Downlink slot and (sub)frame structure Symbol time, or number of symbols per time slot is not fixed One radio frame, Tf = 307200Ts=10 ms One slot, Tslot = 15360Ts = 0.5 ms #0 #1 #2 #3 #18 #19 One subframeWe talk about 1 slot, but the minimum resource is 1 subframe = 2 slots !!!!! Ts  1 15000  2048 Ts = 32.522 ns November 2012 | LTE Introduction | 87
  88. 88. Resource block definition 1 slot = 0,5msecResource block=6 or 7 symbolsIn 12 subcarriers 12 subcarriers Resource element DL UL N symb or N symb 6 or 7, Depending on cyclic prefix November 2012 | LTE Introduction | 88
  89. 89. LTE DownlinkOFDMA time-frequency multiplexing frequency QPSK, 16QAM or 64QAM modulation UE4 1 resource block = 180 kHz = 12 subcarriers UE5 UE3 UE2 UE6 Subcarrier spacing = 15 kHz time UE1 1 subframe =*TTI = transmission time interval 1 slot = 0.5 ms = 1 ms= 1 TTI*=** For normal cyclic prefix duration 7 OFDM symbols** 1 resource block pair November 2012 | LTE Introduction | 89
  90. 90. LTE: new physical channels for data and control Physical Control Format Indicator Channel PCFICH: Indicates Format of PDCCH Physical Downlink Control Channel PDCCH: Downlink and uplink scheduling decisions Physical Downlink Shared Channel PDSCH: Downlink data Physical Hybrid ARQ Indicator Channel PHICH: ACK/NACK for uplink packets Physical Uplink Shared Channel PUSCH: Uplink data Physical Uplink Control Channel PUCCH: ACK/NACK for downlink packets, scheduling requests, channel quality info November 2012 | LTE Introduction | 90
  91. 91. LTE Downlink: FDD channel mapping example Subcarrier #0 RB November 2012 | LTE Introduction | 91
  92. 92. LTE – spectrum flexibility l LTE physical layer supports any bandwidth from 1.4 MHz to 20 MHz in steps of 180 kHz (resource block) l Current LTE specification supports only a subset of 6 different system bandwidths l All UEs must support the maximum bandwidth of 20 MHz Channel Bandwidth [MHz] Channel Transmission Bandwidth Configuration [RB]bandwidth Transmission BWChannel 1.4 3 5 10 15 20 Bandwidth [RB] Channel edge Channel edge [MHz] Resource block FDD andTDD mode 6 15 25 50 75 100 number of resource blocks Active Resource Blocks DC carrier (downlink only) November 2012 | LTE Introduction | 92
  93. 93. LTE Downlink: baseband signal generationcode words layers antenna ports Modulation OFDM OFDM signal Scrambling Mapper Mapper generation Layer Precoding Mapper Modulation OFDM OFDM signal Scrambling Mapper Mapper generation 1 stream = several Avoid QPSK For MIMO Weighting 1 OFDM subcarriers, constant 16 QAM Split into data symbol per based onsequences 64 QAM Several streams for stream Physical streams if MIMO ressource needed blocks November 2012 | LTE Introduction | 93
  94. 94. Adaptive modulation and coding Transportation block size User data FECFlexible ratio between data and FEC = adaptive coding November 2012 | LTE Introduction | 94
  95. 95. Channel Coding Performance November 2012 | LTE Introduction | 95
  96. 96. Automatic repeat request, latency aspects •Transport block size = amount of data bits (excluding redundancy!) •TTI, Transmit Time Interval = time duration for transmitting 1 transport block Transport block Round Trip Time ACK/NACK Network UE Immediate acknowledged or non-acknowledged feedback of data transmission November 2012 | LTE Introduction | 96
  97. 97. HARQ principle: Stop and Wait Δt = Round trip timeTx Data Data Data Data Data Data Data Data Data Data ACK/NACK Demodulate, decode, descramble, Rx FFT operation, check CRC, etc. process Processing time for receiver Described as 1 HARQ process November 2012 | LTE Introduction | 97
  98. 98. HARQ principle: Multitasking Δt = Round trip timeTx Data Data Data Data Data Data Data Data Data Data ACK/NACK Demodulate, decode, descramble, Rx FFT operation, check CRC, etc. process ACK/NACK Processing time for receiver Rx Demodulate, decode, descramble, process FFT operation, check CRC, etc. t Described as 1 HARQ process November 2012 | LTE Introduction | 98
  99. 99. LTE Round Trip Time RTT n+4 n+4 n+4 ACK/NACK PDCCH PHICH Downlink HARQ Data Data UL Uplinkt=0 t=1 t=2 t=3 t=4 t=5 t=6 t=7 t=8 t=9 t=0 t=1 t=2 t=3 t=4 t=5 1 frame = 10 subframes 8 HARQ processes RTT = 8 msec November 2012 | LTE Introduction | 99
  100. 100. HARQ principle: Soft combininglT i is a e am l o h n e co i g Reception of first transportation block. Unfortunately containing transmission errors November 2012 | LTE Introduction | 100
  101. 101. HARQ principle: Soft combining l hi i n x m le f cha n l c ing Reception of retransmitted transportation block. Still containing transmission errors November 2012 | LTE Introduction | 101
  102. 102. HARQ principle: Soft combining 1st transmission with puncturing scheme P1 l T i is a e am l o h n e co i g 2nd transmission with puncturing scheme P2 l hi i n x m le f cha n l c ing Soft Combining = Σ of transmission 1 and 2 l Thi is an exam le of channel co ing Final decoding lThis is an example of channel coding November 2012 | LTE Introduction | 102
  103. 103. Hybrid ARQChase Combining = identical retransmission Turbo Encoder output (36 bits) Systematic Bits Parity 1 Parity 2 Transmitted Bit Rate Matching to 16 bits (Puncturing) Original Transmission Retransmission Systematic Bits Parity 1 Parity 2 Punctured Bit Chase Combining at receiver Systematic Bits Parity 1 Parity 2 November 2012 | LTE Introduction | 103
  104. 104. Hybrid ARQIncremental Redundancy Turbo Encoder output (36 bits) Systematic Bits Parity 1 Parity 2 Rate Matching to 16 bits (Puncturing) Original Transmission Retransmission Systematic Bits Parity 1 Parity 2 Punctured Bit Incremental Redundancy Combining at receiver Systematic Bits Parity 1 Parity 2 November 2012 | LTE Introduction | 104
  105. 105. LTE Physical Layer: SC-FDMA in uplinkSingle Carrier Frequency Division Multiple Access November 2012 | LTE Introduction | 105
  106. 106. LTE Uplink:How to generate an SC-FDMA signal in theory? Coded symbol rate= R Sub-carrier CP DFT Mapping IFFT insertion NTX symbols Size-NTX Size-NFFT LTE provides QPSK,16QAM, and 64QAM as uplink modulation schemes DFT is first applied to block of NTX modulated data symbols to transform them into frequency domain Sub-carrier mapping allows flexible allocation of signal to available sub-carriers IFFT and cyclic prefix (CP) insertion as in OFDM Each subcarrier carries a portion of superposed DFT spread data symbols Can also be seen as “pre-coded OFDM” or “DFT-spread OFDM” November 2012 | LTE Introduction | 106
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