Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
LTE 시스템의특징: ArchitectureLTE(Long Term Evolution) (=E-UTRAN)
SAE(System Architecture Evolution) (=EPC)
EPS(Evolved Packet System) = E-UTRAN + EPC
Circuit Core
User mgmt.Operator
service
Packet Core
2G
3G
CS Networks
IP Networks
LTE
Non-3GPPWiFi, WiMAX,
CDMA2000/HRPD
Core Network
Internet
Operator
Service etc.
Internet
Operator
Service etc.
EPC (SAE)Core network
EPC (SAE)Core network
E-UTRAN (LTE)Radio Access
Network
E-UTRAN (LTE)Radio Access
Network
EPS : Evolved Packet SystemIP : Internet ProtocolCS : Circuit SwitchingEPC : Evolved Packet CoreSAE : System Architecture EvolutionE-UTRAN : Evolved Universal Terrestrial Radio Access Network
WiFi : Wireless FidelityWiMAX : Worldwide Interoperability
for Microwave AccessCDMA : Code Division Multiple AccessHRPD : High Rate Packet Data
1/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
LTE 시스템의특징: Architecture
One RAN node: eNBOne RAN node: eNB
ATM : Asynchronous Transfer ModeNAS : Non-Access StratumRRM : Radio Resource ManagementPDCP : Packet Data Convergence ProtocolRRC : Radio Resource ControlRLC : Radio Link Control
SGSN : Serving GPRS Support NodeGPRS : General Packet Radio ServicesGGSN : Gateway GPRS Support NodeRNC : Radio Network ControllerMME : Mobility Management Entity
2/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
이동통신서비스의진화와발전
2G, 3G3.5G
(HSDPA, EVDO)4G
(LTE, WiMAX)
Access Scheme CDMA OFDM(A)
Modulation QPSKUp to 16QAM
(64QAM in HSPA+)QPSK, 16QAM,
64QAM
Link Adaptation Mainly PCMainly AMC with channel aware-
scheduler
ARQARQ without soft
combiningHARQ with soft combining
Handover Soft handover Hard handover
Duplexing FDDFDD,
TDD is emerging
Antenna Technology
Rx Antenna Diversity(MIMO in HSPA+)
Various Antenna Diversity, MIMO, BF
CDMA : Code Division Multiple AccessOFDMA : Orthogonal Frequency Multiple AccessQPSK : Quadrature Phase Shift KeyingQAM : Quadrature Amplitude ModulationHSPA : High Speed Packet AccessPC : Power Control
AMC : Adaptive Modulation and CodingARQ : Automatic Repeat reQuestHARQ : Hybrid Automatic Repeat reQuestFDD : Frequency Division DuplexTDD : Time Division DuplexMIMO : Multiple Input Multiple OutputBF : Beam-Forming
3/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
LTE 시스템과기존 3G 시스템의비교
CDMAWCDMA
SISOQPSK, 16QAM
CDMAWCDMA
SISOQPSK, 16QAM
OFDMASC-FDMA
MIMO64QAM
OFDMASC-FDMA
MIMO64QAM
Fixed bandwidth
Fixed bandwidth
Flexible bandwidth,
Duplex flexibility
Flexible bandwidth,
Duplex flexibility
Circuit Core Packet CoreCircuit Core Packet Core
EPCPacket Core only
EPCPacket Core only
BetterData RateandLatency
SpectrumFlexibility
SimpleArchitecture
Latency: 5msBandwidth: up to 20MHz
Peak data rate: 326.4MbpsSpectral eff.:
2.67bps/Hz/cell
Latency: 5msBandwidth: up to 20MHz
Peak data rate: 326.4MbpsSpectral eff.:
2.67bps/Hz/cell
Roughly 3~4 times performance improvement than 3G
Roughly 3~4 times performance improvement than 3G
Latency: 20msBandwidth: 5MHz
Peak data rate: 42MbpsSpectral eff.:
0.53bps/Hz/cell
Latency: 20msBandwidth: 5MHz
Peak data rate: 42MbpsSpectral eff.:
0.53bps/Hz/cell
Low prices
Simple andvalue added
Higher quality
Ubiquity
EPC : Evolved Packet Core
4/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
LTE 시스템과기존 3G 시스템의비교HSPA HSPA+ WiMAX wave2 LTE WiMAX 802.16m
Bandwidth(MHz) 5 5 5, 7, 8.75, 10 1.4, 3, 5, 10, 15, 20 5, 7, 8.75, 10 ,20 ,40
Multiple Access CDMA CDMA OFDMA OFDMA/SC-FDMA OFDMA
Duplex FDD FDD TDD FDD, TDD FDD, TDD
MIMO - MIMO(2×2, 4×4) MIMO(2×2, 4×4) MIMO(2×2, 4×4) MIMO(2×2, 4×4, 8×8)
Peak Modulation(UL/DL) & Coding
16QAM/QPSKTurbo Code/HARQ
64QAM/16QAMTurbo Code/HARQ
64QAM/16QAMTurbo Code/HARQ
64QAM/64QAMTurbo Code/HARQ
64QAM/64QAMTurbo Code/HARQ
User Plane Latency 25ms 20ms 20ms 5ms 10ms
DL Peak Data Rate 14.4Mbps 42Mbps14.4Mbps
(10MHz, 2×2 MIMO)(DL:UL=2:1)
§ 172.8Mbps(20MHz, 2×2 MIMO)
§ 326.4Mbps(20MHz, 4×4 MIMO)
§ 160Mbps(20MHz, 2×2 MIMO)
§ 300Mbps(20MHz, 4×4 MIMO)
UL Peak Data Rate 5.76Mbps 11.52Mbps13Mbps
(10MHz, 1×2 MIMO)(DL:UL=2:1)
§ 86.4Mbps(20MHz, 1×2 MIMO)
§ 172Mbps(20MHz, 2×4 MIMO
§ 56Mbps(20MHz, 1×2 MIMO)
§ 135Mbps(20MHz, 2×4 MIMO
Service CS & PS CS & PS PS & Voice(VoIP) PS & Voice(VoIP) PS & Voice(VoIP)
Mobility Up to 350Km Up to 350Km Up to 120Km Up to 350Km Up to 350Km
CS : Circuit SwitchingPS : Packet SwitchingVoIP : Voice over Internet Protocol
5/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
LTE System PerformancePeak Data Rate
1) ~14% reference signal overhead (4 Tx antennas in DL)~10% common channel overhead (1 UE/subframe)~7% waveform overhead (CP)~10% guard band~ (1/1) code rate
2) ~14% reference signal overhead (1 Tx antenna in UL)~0.6% random access overhead~7% waveform overhead (CP)~10% guard band~ (1/1) code rate
Case Peak Data Rate (Mbps)Downlink(64QAM, 20MHz)
2x2 MIMO 150.84x4 MIMO 302.8 1)
Uplink(20MHz)
16QAM 51.064QAM 75.4 2)
6/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
LTE Key FeaturesDownlink: OFDMA (Orthogonal Frequency Division Multiple Access)o Less critical AMP efficiency in BS side
o Concerns on high RX complexity in terminal side
Uplink: SC-FDMA (Single Carrier-FDMA)o Less critical RX complexity in BS side
o Critical AMP complexity in terminal side (Cost, Power consumption, UL coverage)
Single node RAN (eNB)
Support FDD (frame type 1) & TDD (frame type 2 for TD-SCDMA)
User data rateso DL (baseline): 150.8 Mbps @ 20 MHz BW w/ 2x2 SU-MIMO
o UL (baseline): 75.4 Mbps @ 20 MHz BW w/ non-MIMO or 1x2 MU-MIMO
Radio frame: 10 ms (= 20 slots), Sub-frame: 1 ms (= 2 slots), Slot: 0.5 ms
TTI (transmit time interval): 1 ms (= 1 sub-frame)
HARQo Incremental redundancy is used as the soft combining strategy
o Retransmission time: 8 ms
Modulationo DL/UL data channel = QPSK/16QAM/64QAM
Hard handover-based mobility
Making MS as cheap as possible by moving all the
burdens from MS to BS
7/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
LTE Key Features – cont’dMIMO SM (Spatial Multiplexing), Beamforming, Antenna DiversityMin requirement: 2 eNB antennas & 2 UE rx antennaso DL: Single-User MIMO up to 4x4 supportable, MU-MIMOo UL: MU-MIMO
Resource blocko 12 subcarriers with subcarrier BW of 15kHz à “180kHz”o 24 subcarriers with subcarrier BW of 7.5kHz (only for MBMS)
Subcarrier operationo Frequency selective by localized subcarriero Frequency diversity by distributed subcarrier & frequency hopping
Frequency hoppingo Intra-TTI: UL (once per 0.5ms slot), DL (once per 66us symbol)o Inter-TTI: across retransmissions
Bearer serviceso Packet only – no circuit switched voice or data services are supportedo Voice must use VoIP
MBSFNo Multicast/Broadcast over a Single Frequency Network o To support a Multimedia Broadcast and Multicast System (MBMS)o Time-synchronized common waveform is transmitted from multiple cells for a given durationo The signal at MS will appear exactly as a signal transmitted from a single cell site and subject to multi-patho Not only “improve the received signal strength” but also “eliminate inter-cell interference”
8/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
LTE Modulation SchemesDownlinkDownlink channels Modulation scheme
PBCH (Physical Broadcast Channel) QPSK
PDCCH (Physical Downlink Control Channel) QPSK
PDSCH (Physical Downlink Shared Channel) QPSK, 16QAM, 64QAM
PCFICH (Physical Control Format Indicator Channel) QPSK
PHICH (Physical Hybrid ARQ Indicator Channel) BPSK modulated I and Q
Physical signals Modulation scheme
RS (Reference Signal) Complex I+jQ pseudo random sequence
P-SS (Primary Synchronization Signal) One of three Zadoff-Chu sequence
S-SS (Secondary Synchronization Signal) Two 31-bit BPSK M-sequence
UplinkPhysical channels Modulation scheme
PUCCH (Physical Uplink Control Channel) BPSK, QPSK
PUSCH (Physical Uplink Shared Channel) QPSK, 16QAM, 64QAM
PRACH (Physical Random Access Channel) uth Zadoff-Chu
Physical signals Modulation scheme
Demodulation RS (Demodulation Reference Signal) Zadoff-Chu
Sounding RS (Sounding Reference Signal) Based on Zadoff-Chu
9/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
Vertical/Horizontal MIMO
Antenna 마다 다른 FEC 및 modulation
Vertical Encoded 2x2 MIMO System = Single CodeWord MIMO (SCW MIMO)
Horizontal Encoded 2x2 MIMO System = Multiple Codeword MIMO (MCW MIMO) : MU-MIMO
같은 FEC 및 modulation
Uplink? Downlink?
10/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
SFBC STBC (Space Time Block Code)
SFBC (Space Frequency Block Code)
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
Cyclic Delay Diversity (CDD)3GPP Release 8 LTE 표준
채널의심한변화
Scattered frequency selective fading주파수영역에서인터리빙
주파수코딩이득증대Burst frequency selective fading
12/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
AMS (Adaptive MIMO Switching)
§ CQI (Channel Quality Index) : AMC§ PMI (Precoding Mapping Index) : Precoder§ RI (Rank Index) : Number of stream
13/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
MIMO 기법Open/closed loop MIMO
Multicell MIMO, COMP(cooperative multi-point Tx & Rx) – LTE-A
14/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
R8 LTE MIMO Design PrinciplesAnti-fading: TD(Transmit diversity) (and SM)
Enhance spectral efficiency: SM (TD and BF)
Enhance SNR: BF (and codebook-based precoding)
Channel adaptive: CL precoding, Rank adaptation
15/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
R8 LTE MIMO Summary
(Frequency switched transmit diversity)
(Precoding vector switching)(Time switched transmit diversity)
(Demodulation)16/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
LTE 물리채널별 MIMO 기술Physical channel Usage Tx Diversity SM-MIMO CDD
Reference Signal X X XPrimary, & Secondary Synch Signal X X X
Physical Broadcasting Channel
System information (Master information Block)
O X X
Physical Control Format Indication Channel
Control FormatIndicator( Subframe마다전송, OFDM symbol 수)
O X X
Physical Downlink Control Channel
자원할당, HARQ 및scheduling 정보 O X X
Physical Multicast Channel
방송형 data O O X
Physical Downlink Shared Channel
Downlink user data O O O
17/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
LTE PHY - DL
Contents
o Frame and Slot Structure
o Physical Channel Processing
o Physical Signals
o Physical Channels
18/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
LTE DL 기술의개요Multiple Accesso DL : OFDMA
Bandwidth : Scalable bandwidth up to 20Mhz : 1.4M, 3M, 5M, 10M, 20M
FDD와 TDD의동시지원 (FDD가대부분)o TDD 방식은중국의 TD-SCDMA에서 LTE로의진화를정의
Modulation for DL/UL : QPSK, 16QAM, 64QAM
10ms PHY frame, 1ms TTI
Resource Block (RB)o 180khz(15khz Subcarrier × 12개) : 일반 resource block
o 180khz(7.5khz Subcarrier × 24개) : MBMS resource block
다양한안테나기술
o 2 ×2, 4 ×4 MIMO for DL
o Rx diversity
19/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
E-UTRA Channel Bandwidth*
1RB (15KHz/carriers, 12 carriers) = 180kHz
à 6RBs = 1.08MHz, à 100RBs = 18MHz
6RBs (72 subcarriers) with 128 FFT, 100RBs (1200 subcarriers) with 2048 FFT
Table 5.6-1 Transmission bandwidth configuration NRB in E-UTRA channel bandwidths
Figure 5.6-1 Definition of Channel Bandwidth and Transmission Bandwidth Configuration for one E UTRA carrier
* 3GPP TS 36.101, E-UTRA: UE radio transmission and reception, Release 9
Channel Bandwidth (MHz) 1.4 3 5 10 15 20
Number of Occupied Subcarrier including DC (Nsc)
73(12*6+1)
181(12*15+1)
301(12*15+1)
601(12*50+1) 901 1201
FFT Size (N) 128 256 512 1024 1536 2048
Sampling Rate (MHz) 1.92 3.84 7.68 15.36 23.04 30.72
Number of Resource Blocks (NRB) (12 carriers/RB) 6 15 25 50 75 100
20/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
Flexible Frequency Channel of LTELTE 에서는공통제어신호를전송하는 1.4Mhz를포함하는다양한채널대역폭할당가능
채널 BW에따른 RB수및전송 BW채널 BW 1.4Mhz 3Mhz 5Mhz 10Mhz 20Mhz
RB수/tone 수 6/72 15/180 25/300 50/600 100/1200
전송 BW 10.8Mhz 2.7Mhz 4.5Mhz 9Mhz 18Mhz
21/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
DL Physical Channel Processing
Scrambling of coded bits in each of the code words to be transmitted on a physical channel
Modulation of scrambled bits to generate complex-valued modulation symbols
Mapping of the complex-valued modulation symbols onto one or several transmission layers
Precoding of the complex-valued modulation symbols on each layer for transmission on the antenna ports
Mapping of complex-valued modulation symbols for each antenna port to resource elements
Generation of complex-valued time domain OFDM signal for each antenna port
22/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
Modulation
Physical channel Modulation schemesPDSCH QPSK, 16QAM, 64QAMPMCH QPSK, 16QAM, 64QAM
Physical channel Modulation schemesPBCH QPSK
Physical channel Modulation schemesPCFICH QPSK
Physical channel Modulation schemesPDCCH QPSK
Physical channel Modulation schemesPHICH BPSK
Physical signalso A set of resource elements not carrying
information§ Reference signal
§ Synchronization signal
Physical channelso A set of resource elements carrying
information§ Physical Downlink Shared Channel, PDSCH
§ Physical Broadcast Channels, PBCH
§ Physical Multicast Channel, PMCH
§ Physical Control Format Indicator Channel, PCFICH
§ Physical Downlink Control Channel, PDCCH
§ Physical Hybrid ARQ Indicator Channel, PHICH
23/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
Layer mapping and Precoding
24/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
Layer Mapping
25/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
PrecodingThe precoder takes as input a block of vectors
and generates a block of vectors
to be mapped onto resources on each of the antenna port where
represents the signal for antenna port p.
( ) ( ) ( ) ( ) ( )0 1 layersymb, 0,1, , 1
Tvx i x i x i i M-é ù= = -ë ûL L
( ) ( ) ( ) apsymb, 0,1, , 1
Tpy i y i i Mé ù= = -ë ûL L L
( )( )iy p
Precoding without CDD Precoding for large-delay CDD
( )( )
( )( )( )
( )( )
( )( )úúú
û
ù
êêê
ë
é
=úúú
û
ù
êêê
ë
é
-- ix
ixiW
iy
iy
vP 1
0
1
0
MM
( )( )
( )( )( ) ( )
( )( )
( )( )úúú
û
ù
êêê
ë
é
=úúú
û
ù
êêê
ë
é
-- ix
ixUiDiW
iy
iy
vP 1
0
1
0
MM
26/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
Precoding
27/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
Codebook for Precoding – 2 portsThe precoding matrix W(i) shall be selected from below table
28/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
Codebook for Precoding – 4 portsdenotes the matrix defined by the columns given by the set {s}
22 nHnnn uuuIW -=
{ }snW
29/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
Open loop Spatial MultiplexingTwo antenna ports caseo Large delay CDD along with a fixed precoder matrix is used
Four antenna ports caso Precoder cycling is used
30/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
Transmit Diversity SchemesSpace Frequency Block Codes (SFBC)o SFBC is a frequency domain version of the STBC (Alamouti codes)
o Transmit diversity streams are orthogonal and achieve the optimal SNR with a linear receiver
Frequency Switched Transmit Diversity (FSTD) Combining with SFBC
31/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
Transmit Diversity SchemesThe transmit matrix for the balanced SFBC-FSTD scheme is given as
The equivalent channel matrix for the balanced SFBC-FSTD scheme is
assuming a matched filter receiver, the resulting channel gains matrix is
(0) (1)(0) (0) (0) (0)
(2) (3)(1) (1) (1) (1)
((2) (2) (2) (2)
(3) (3) (3) (3)
( ) ( ) 0 0(4 ) (4 1) (4 2) (4 3)0 0 ( ) ( )(4 ) (4 1) (4 2) (4 3)
(4 ) (4 1) (4 2) (4 3)(4 ) (4 1) (4 2) (4 3)
x i x iy i y i y i y ix i x iy i y i y i y i
xy i y i y i y iy i y i y i y i
é ù+ + +ê ú+ + +ê ú = -ê ú+ + +ê ú
+ + +ë û
( ) ( )( ) ( )
* *1) (0)
* *(3) (2)
( ) ( ) 0 0
0 0 ( ) ( )
i x i
x i x i
é ùê úê úê úê úê ú
- -ê úë û
*0 2
*2 0
4 *1 3
*3 1
0 00 01
0 040 0
SFBC FSTD
h hh h
Hh hh h
- -
é ù-ê úê ú=ê ú-ê úê úë û
2 20 2
2 20 2
2 21 3
2 21 3
( ) 0 0 02
( )0 0 02
( )0 0 02
( )0 0 02
h h
h h
h h
h h
é ù+ê úê ú
+ê úê ú
= ê ú+ê ú
ê úê ú
+ê úê úë û
32/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
Physical signals and channelsPhysical signalso A set of resource elements not carrying information
§ Reference signal
§ Synchronization signal
Physical channelso A set of resource elements carrying information
§ Physical Downlink Shared Channel, PDSCH
§ Physical Broadcast Channels, PBCH
§ Physical Multicast Channel, PMCH
§ Physical Control Format Indicator Channel, PCFICH
§ Physical Downlink Control Channel, PDCCH
§ Physical Hybrid ARQ Indicator Channel, PHICH
33/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
DL Physical SignalsReference signals (RS)o Cell-specific RS: associated with non-MBSFN transmission (unicast RS)
§ Transmitted in every downlink subframe, and span entire cell BW
§ Used for initial cell search
§ Used for downlink signal strength measurements for scheduling and handover
§ Using antenna ports {0, 1, 2, 3}
o MBSFN RS: associated with MBSFN transmission§ Used for channel estimation for coherent demodulations of signals being transmitted by means of
MBSFN
§ Using antenna ports 4
o UE-specific RS§ Specifically intended for channel estimation for coherent demodulation of DL-SCH when non-
codebook-based beamforming is used
§ Using antenna port 5
Synchronization Signals (SS)o Carries frequency and symbol timing synchronization
o PSS (Primary SS) and SSS (Secondary SS)
34/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
Cell-Specific RS mapping
Normal CP
Extended CP
1 Tx ant 4.76% 5.56%
2 Tx ant 9.52% 11.11%
4 Tx ant 14.29% 15.87%
35/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
UE-specific RS on top of Cell-specific RSUE-specific RS (antenna port 5)o 12 symbols per RB pair
DL CQI estimation is always based on cell-specific RS (common RS)
36/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
LTE Cell Search
37/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
LTE Cell Search
38/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
PDSCH
39/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
7 Tx modes in PDSCHMode 1 : Single-antenna port; port 0o DL transmissions using a single Tx antenna at eNB
Mode 2 : Transmit diversityo DL transmission using Alamouti-like transmit diversity schemes
o The number of layers is equal to the number of antenna ports
40/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
7 Tx modes in PDSCHMode 3 : Open loop spatial multiplexingo Transmit different streams of data simultaneously on the same RB(s) by exploiting the
spatial dimension of the radio channel. These data streams belong to the same user
o Up to 2 codewords transmissions with “no PMI feedback”
o Exploits CDD in DL transmissions
o Up to 4 layers and 4 antennas
41/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
7 Tx modes in PDSCHMode 4 : Closed loop spatial multiplexing (SU-MIMO)o Transmit different streams of data simultaneously on the same RB(s) by exploiting the
spatial dimension of the radio channel. These data streams belong to the same user
o Up to 2 codewords transmissions with “RI and PMI feedback”
o Exploits CDD in DL transmissions
o Up to 4 layers and 4 antennas
42/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
7 Tx modes in PDSCHMode 5 : Multi-user MIMO (MU-MIMO)o Transmit different streams of data simultaneously on the same RB(s) by exploiting the
spatial dimension of the radio channel. These data streams belong to different users
o Also known as downlink SDMA
o Single codewords and single Layer per user (UE reports only PMI, no RI is reported)
o Up to 4 Tx antennas at eNB
o Different users can use the same time/freq resources in different location within a cell
43/44
Note 16. MIMO-OFDM for LTE연세대학교 전기전자공학과 최수용
7 Tx modes in PDSCHMode 6 : Closed loop Rank=1 precodingo Same as Mode 4 with Rank restriction 1
o No Rank reports are required
Mode 7 : Single antenna port; port 5o Same as Mode 1 using UE-specific Reference Signals instead of Cell-specific
Reference Signals (with the help of sounding reference signal)
44/44
Top Related