3 Lte Bt04 e2 1 Mimo Principle-34

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MIMO Principle

ZTE University

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Objects

n After the course,you will:l Know the MIMO mode in LTEl Know the benefits of MIMOl Understand the transit mode of MIMOl Know the MIMO Performance and Application






Content

LTE MIMO IntroductionTransmit Modes Theory IntroductionMIMO PerformanceMIMO Application






Inputs and Outputs

Single Input Single Output Multi Input Single Output

Single Input Multi Output Multi Input Multi Output

n In the specifications, the terms input ! and output ! apply to the mediumbetween the transmitters and receivers, including the RF components of

both "

known as the channel!

.






What is MIMO?

n MIMO (Multiple Input Multiple output) A set of techniques that rely on the use of multiple antennas atthe receiver and/or transmitter. It can be used to achieveimproved system capacity and improved coverage area.

Multiple-input, multiple-output (MIMO) techniques have been integrated asone of the key approaches to provide the peak data rate, average

throughput, and system performance in 3rd Generation Partnership Project(3GPP) long term evolution (LTE). Based on the function of the multipletransmission symbol streams in MIMO, the operation mode of multipletransmit antennas at the cell site (denoted as MIMO mode) have spatialdivision multiplexing (SDM), precoding, and transmit diversity (TD). Base onthe allocation of the multiple transmission streams in MIMO, the MIMOmode is denoted as single user (SU)-MIMO if the multiple transmissionsymbol stream is solely assigned to a single UE and multiuser (MU)-MIMO ifthe SDM of the modulation symbol streams for different UEs use the sametime-frequency resource.






LTE MIMO Mode

Multi-antenna Technology

LTE adopts MIMO as multi-antenna technology

LTE basic antenna configuration is DL 2*2 (Double Transmitters Double Receivers) and UL1*2 (Single Transmitter Double Receivers). LTE maximum antenna configuration is 4*4(Quadruplex Transmitters Quadruplex Receivers).

SU-MIMO

This is an example of downlink 2 2 single user MIMO with precoding

Two data streams are mixed (precoded) to best match the channel conditions

The receiver reconstructs the original streams resulting in increased single user data rateand corresponding increase in cell capacity

2 2 SU-MIMO is mandatory for the downlink and optional for uplink

MU-MIMO

Example of uplink 2 2 multiple user MIMO

In multiple user MIMO the data streams come from different UE

There on possibility to do the precoding since the UE are not connected but the winder Txantenna spacing gives better de-correlation in the channel

Cell capacity increases but not the single user data rate

The key advantage of MU-MIMO over SU-MIMO is that cell capacity increase can be hadwithout the increased cost and battery drain of two UE transmitters

MU-MIMO is more complicated to schedule than SU-MIMO






MIMO System Capacity

!"#!"$%MIMO&'(

)

*"#!"$% SIMO &

'( )

22

1

log (1 | | ) / / M

i

i

C h b s H z ρ=

= + ∑2

21

log (1 | | ) / / N

i

i

C h b s H z N

ρ=

= + ∑

*2 2

1log [det( )] log (1 ) / /

m

EP M ii

C I HH b s Hz N N

ρ ρλ== + = +∑

In MIMO system, the number of antenna is related with the system capacity.

22log (1 | | ) / /C h b s Hz ρ= +*"#*"$% SISO &'( )

MISO System

MIMO System )

SIMO System )

SISO System )






Why select MIMO ?

finit






Content







MIMO System Model

11 12 1 1 11

21 22 2 2 22

1 2

t

t

t t r r r r t

N

N

N N N N N N N

h h h x nr h h h x nr

x nr h h h

= +

LL

M MM M M M M

M

MIMO Signal Model Expression

MIMO System Model

10






LTE Key Technology---MIMO Theory

Space multiplexing & space diversity leads to higher bit rate.

Receiver

Datastream

EncodeEncode

EncodeEncode Channel

Interleave

ChannelInterleave

ChannelInterleave

ChannelInterleave

Modulator QPSK

16QAM

Modulator QPSK

16QAM

Modulator QPSK

16QAM

Modulator QPSK

16QAM

Detector Detector

Detector Detector

MUXMUX

Datastream

v12

v21

v11

v22

Transmitter DeMUX

DeMUX

MIMO Technologies include: Space multiplex (SM), Space division multipleaddress (SDMA), Pre-coding, Rank-adaptation and open loop Tx diversity

(STTD, mainly used to control the transmission of control signaling).The concrete technology is in consideration and not yet determined.






Structure of Downlink Reference Signals

The Structure of CRS in different antennas

In case of two antenna port: The CRS of second antenna port are a

frequency offset of three sub carriers compared to the firstantenna port;

In case of four antenna port: The CRS of the third and the forthantenna port are only two OFDM symbols in one slot due to limitthe reference signals overhead.

The Structure of UE-Specific Reference Signals

Only be used by the specific terminal of non codebook beam-formingtransmission;

It is also referred to as transmission using single antenna port 5;

It is inserted in the data part of allocated resource blocks;It is used for the estimation of demodulation for the beam-formed

data transmission.






Transmit Diversity 2 Antennas !

Transmit Diversity

No enough knowledge from downlink channels of different antennas,

such as in high mobility environment;SFBC for two antenna ports;

SFBC + FSTD for four antenna ports;

Large Delay CDD






SFBC + FSTD

n SFBC for two antenna ports

n SFBC + FSTD for four antenna ports

n Application Scenario for SFBCl SFBC enhance system coverage :Improving quality in multi-path fadingl SFBC application scenario : all environment

n Large Delay CDD : Suitable for high mobility scenario

SFBC: Space frequency block codeFSTD: frequency switched transmitted diversitySFBC for two antenna ports

Rank is equal to one;On the first antenna port: Modulation symbol a0 and a1 are mapped on adjacent sub carriers;On the second antenna port:

the swapped and transformed symbols a1* and a0* are transmitted on the corresponding sub-carriers.

SFBC + FSTD for four antenna portsCombined SFBC/FSTD is used for PDSCH, PCFICH, PHICH and PDCCH;

Antenna 0/2 and 1/3 are two pairs of antenna ports;While transmission is on one pair, there is no transmission on another pair.

Applic ation Scenario for SFBC SFBC enhance system coverage

Single data stream replicated and transmitted over multiple antennasRedundant data stream encoded known as space frequency block codes

Improving quality in multi-path fading Improving SNR, especially in the cell-edgeReceiver can use MRC techniques to combine the multiple signals

SFBC application scenarioUsed in open-loop SM Used in Control channel and data channel No require feedback from receiver Complex or simple multi-path environmentsHigher or minor speed mobility Seem to suited for all environment, such as correlation

Channel or un-correlation channel

Large Delay CDDNo require PMI information for terminal;

Suitable for high mobility scenario;Only applicable for two or more layers;IF one layer ( RANK =1), Open loop SM corresponds to SFBC

CDD: cyclic delay diversity






Spatial Multiplexing

n Code words + Layers + Tx antennas

n Different data content ## Increase throughput

n More complex precoding ## Code book

15








Application Scenario for Beam-Forming

Low correlation antenna

High correlation antenna

Low correlation antenna

Antenna configuration with a large antenna distance or different

polarization antenna;The antenna weights include the phase and amplitude;

Phase rotates the transmitted signals to compensate for the channel phase and ensure that the received signals are phase aligned;

Allocates more power to the antennas with good channel condition;

Mode-7, Non codebook BF;

High correlation antenna

Antenna configuration with a small inter-antenna distance;

The Antenna weights are same between different antenna ports,including channel fading;

Different phase shifts to the direction of the terminal;

Increase the received signal strength rather than provide diversityagainst channel fading;

Be suitable for large area coverage;

Mode-6, Codebook BF;

BF is the shaping of the overall antenna beam in the direction of atarget receiver

Improve cell-edge data rates in downlink: Increases power in thedirection of the signal and meanwhile suppress interference

None codebook Beam-forming: Based on directionality and channelconditions from uplink measurement, base station calculates weights






Beam-Forming in LTE

Codebook based Beam-formingMode-6 and Single stream Precoding;The terminal select a recommendation PMI information and report to the Base Station;

Only use cell-specific reference signal;Non Codebook based Beam-forming

Mode-7, Single antenna port (port 5)Based on directionality and channel conditions from uplink measurement;Base station calculates weights assigned to each transmitter controlling phase and relativeamplitude of the signals;Use cell-specific reference signal and UE-specific reference signal

Codebook based Beam-formingThe mobile terminal report PMI to Base StationThere is a PMI correction when Base Station transmit one pre-coding vector if the channelshifts fast between downlink and uplink;For FDD, it is a better choice due to different fading channel between downlink and uplink

channel.Non Codebook based Beam-forming

Base station calculates the weight based on the uplink measurements; Additional overhead of UE-Specific and calibrate RF hardware;For TDD, it is a better choice due to a high fading correlation between downlink and uplinkchannel, especially for 8 antenna;The performance between codebook and non codebook for 4 antennas are similar;There is no requirement at recently time, especially for 4 antennas of FDD.






Content







MIMO Simulation Results-Case 1

n Cell Spectrum efficiency n Cell Edge SE (5% CDF)

eNodeB UE

0.045

0.047

0.054

1T2R

0

0.4

0.8

1.0

1.4

1.8

2.2

1.34 0.045

0.047

0.054

1T2R

0

0.01

0.02

0.03

0.04

0.05

0.06

0.042

Case 1: Simulation Results

One transmit antenna, two receiver antenna

Receiver antenna configuration: 0.5 λFrequency bandwidth: 10MHz;

Frequency reuse 1;

Marco ISD 500m;

CDF ) Cumulate density function ,-./01








Rank

eNodeB UE

0.045

0.047

0.054

2T2R

0

0.4

0.8

1.0

1.4

1.8

2.2

1.6763

0.045

0.047

0.054

2T2R

0

0.01

0.02

0.03

0.04

0.05

0.06

0.0437


Two Transmit antenna; Two Receiver antenna;

eNodeB antenna configuration: cross-polarizationUE antenna configuration: 0.5 λRank adaptive;

RI=1 Single stream;

RI>1 Double stream

Cumulate density function ,-./01








0.045

0.047

0.054

4T2R

0

0.4

0.8

1.0

1.4

1.8

2.2

1.7488

0.045

0.047

4T2R

0

0.01

0.02

0.03

0.04

0.05

0.06

0.0495

Rank

eNodeB UE


Four Transmit antenna; Two Receiver antenna;

eNodeB antenna : 10 λ between two pairs of cross-polarizationUE antenna configuration: 0.5 λRank adaptive;

RI=1 Single stream;

RI>1 Double stream






MIMO Simulation Results


46dBm/Antenna Macro ISD= 500m, 2*2 MIMO

0.045

0.047

0.054

4T2R0

0.4

0.8

1.0

1.4

1.8

2.2

1.748

4T2R0

0.01

0.02

0.03

0.04

0.05

0.06

0.04951.6763

2T2R

1.34

1T2R

0.0437

2T2R

0.042

1T2R25% 30% 4% 18%

Summary






Simulation Results of Different MIMO Modes

FRAverage CellThroughput

Mbps

FrequencyEfficiency

Mbps/Hz

Cell EdgeData Rates Mbps

Cell Edge FrequencyEfficiency

Mbps/Hz

Case 1

43dBm/Antenna Macro ISD=500m,10,2*2MIMO,Rank

Adaptive,20dB, 3km/h 1 8.5631 1.5774 0.2751 0.0507

Case 2

33dBm/Antenna Macro ISD= 500m,4TxBF,SingleStream,20dB, 3km/h 1 13.9773 2.5747 0.9195 0.1694

Case 3

33dBm/Antenna Macro ISD500m,4TxBFprecoding,

Du al Stream,20dB, 3km/h 1 13.4 308 2.47 41 0.89 35 0.164 6

Case 1

43dBm/Antenna Macro ISD =500m,2*2MIMO,Rank

Adaptive,20dB, 3km/h 3 21.7142 1.3333 1.0842 0.0666

Case 2

33dBm/Antenna Macro ISD =

500m,4TxBF,SingleStream,20dB, 3km/h 3 18.6087 1.1426 1.9028 0.1168

Case 3

33dBm/Antenna Macro ISD =500m,4TxBF,precoding,Dual

Stream,20dB, 3km/h 3 28.6932 1.7619 2.2303 0.1366

Frequency reuse =1, The environment can be seen as interference-limited,

Beam-forming can improve the UE $s receiver power, meanwhile

suppress the interference, especially in the cell edge. It is efficiency thanPre-coding MIMO in this environment.

Frequency reuse =3, The SINR is higher than FR=1, especially in the celledge. The environment can be seen as bandwidth-limited, MIMO doublestream can improve peak data rates than single stream, for example, Beam-forming. In this environment, MIMO is efficiency than Beam-forming.

24






Content







6 Mode 6 Codebook BF

High priority

High priority for two antennas,Medium priority for four antennas

Medium/Low priority

Medium priority for four antennas

1 Mode 1 Single Antenna Port

2 Mode 2 Transmit Diversity

3 Mode 3 Open Loop SM

4

5

7

Mode 4 Closed-Loop SM

Mode 5 MU-MIMO

Mode 7 Non Codebook BF

High priority for non-MIMO system

High priority for two antennas,Medium priority for four antennas

MIMO Modes in LTE

Low priority, especially for LTE FDD

Transmit DiversityProvide additional diversity against fading on the radio channel;High or low mobility;Low mutual correlation antenna;Such as Mode 2 and Mode3;

Beam-formingThe shaping of the overall antenna beam in the direction of a target receiver;Improve cell-edge data rates in downlink: Increases power in the direction of thesignal and meanwhile suppress interference;Low mobility;codebook Beam-forming and non codebook beam-forming;Such as Mode 6 and mode 7;


Create what can be seen as multiple parallel channels;Signal splitting into multiple streams and transmitted over different antenna;Multiple signals arrive at the receiver antenna with different ! Space signature " ;SM provides a means for increasing channel capacity, applicable for bandwidthlimited system (higher SNR, especially in the centre of the cell);Low mutual correlation antenna;Relatively lower speed mobility;PMI and RI feedback from UE;Such as mode 4;






6 Mode 6 Codebook BF

Provide Diversity Against Fading

Improve Peak data rates

Improve system Capacity

Improve cell Coverage andSuppress Interference

1 Mode 1 Single Antenna Port

2 Mode 2 Transmit Diversity

3 Mode 3 Open Loop SM

4

5

7

Mode 4 Closed-Loop SM

Mode 5 MU-MIMO

Mode 7 Non Codebook BF

Correspond to Single Antenna Port

High Mobility Environment

Benefits of Different MIMO Modes in LTE

Transmit DiversityProvide additional diversity against fading on the radio channel;High or low mobility;Low mutual correlation antenna;Such as Mode 2 and Mode3;

Beam-formingThe shaping of the overall antenna beam in the direction of a target receiver;Improve cell-edge data rates in downlink: Increases power in the direction of thesignal and meanwhile suppress interference;Low mobility;codebook Beam-forming and non codebook beam-forming;Such as Mode 6 and mode 7;


Create what can be seen as multiple parallel channels;Signal splitting into multiple streams and transmitted over different antenna;Multiple signals arrive at the receiver antenna with different ! Space signature " ;SM provides a means for increasing channel capacity, applicable for bandwidthlimited system (higher SNR, especially in the centre of the cell);Low mutual correlation antenna;Relatively lower speed mobility;PMI and RI feedback from UE;Such as mode 4;






MIMO Modes in Downlink Physical Channel

Mode1 Mode 2 Mode3 " Mode 7PDSCH C C C

PBCH C C

PCFICH C C

PDCCH C C

PHICH C C

SCH C C

The Structure of CRS in different antennas

In case of two antenna port: The CRS of second antenna port are a

frequency offset of three sub carriers compared to the firstantenna port;

In case of four antenna port: The CRS of the third and the forthantenna port are only two OFDM symbols in one slot due to limitthe reference signals overhead.

The Structure of UE-Specific Reference Signals

Only be used by the specific terminal of non codebook beam-formingtransmission;

It is also referred to as transmission using single antenna port 5;

It is inserted in the data part of allocated resource blocks;It is used for the estimation of demodulation for the beam-formed

data transmission.

Three sub carriers: 23456789:;<=>?@ABCDEF8






Application Selection of MIMO Modes

Cell EdgeCell Center

Urban Area

High Speed

Cell Edge

Low Speed % Indoor &

MediumSpeed

Mode-2, Transmit Diversity

Provide additional diversity against fading on the radio channel;

Suitable for cell edge;Mode-3, Open-Loop SM

High speed Mobility environment;

Mode-4, Close-Loop SM

Two codeword: Higher SNR, the center of cell;

One codeword; Increase power and suppress interference, the cell edge;

Mode-5, MU-MIMO

Improve system capacity;

Be suitable for uplink transmission;

Be suitable for Indoor coverage;

Mode-6, CL Rank=1 Precoding

Increase Power;

Such as large area coverage, such as rural area;

Mode-7, single antenna port, port 5

Non codebook beam-forming;

Be suitable for TDD technology;

Increase power and suppress interference;

Be suitable for cell edge;






Handset Adaptation to MIMO Modes

2 Transmit Diversity

3 Open-Loop SM

4

5

7

Closed-Loop SM

MU-MIMO

Non Codebook BF

6 Codebook BF

Mobility Speed Changes

Rank Changes

Location to Cell Changes

Three Main Factors lead to handset adaptation to MIMO Modes:Mobility environment changes;Users changers from cell center to cell edge;Channel correlation corresponding to RANK changes

Higher Mobility speed EnvironmentMode 2: Transmit Diversity;Mode 3: Open-Loop ;No PMI requirement feed back from Terminal.

Lower Mobility speed EnvironmentMode 4: Closed-Loop Precoding;Mode 5: MU-MIMO;Mode 6: Codebook BF;Mode 7: Non codebook BF;PMI/RI requirement feed back from Terminal.

Mobility Environment ChangesIf changes from lower to higher, Mode 2 and Mode3 is adopted;If changes from higher to Lower, Mode4 and Mode6 is adopted.

Low Correlation Environment;RANK >=2;Large-Delay CDD and Double stream Precoding;Complex Multi-path environment.

High Correlation Environment;RANK =1;Codebook Beam-forming /or SFBC;Simple Multi-path environment;

Correlation channel changes;If changes from low to high correlation, SFBC and codebook BF are adopted;If changes from high to low correlation, Double stream Precoding is adopted.

Cell Center Environment;Higher SNR;Double stream Precoding will maximum system capacity;

Cell edge Environment;Lower SNR;Single stream Precoding will improve coverage;

While users move;If move from cell center to cell edge, Single stream will be adopted, such as SFBC and codebook BF;If move from cell edge to cell center, Double stream will be adopted if Rank is larger than 1.






MIMO Modes Conclusion

TransmitScheme

Rank ChannelCorrelation

MobilityEnvironment

Data Rates Location inthe Cell

TransmitDiversity(SFBC)

1 Lowcorrelation

High/MediumSpeed

Lower DataRates

Cell Edge

Open-Loop SM 2/4 Lowcorrelation

High/MediumSpeed

Medium/Lower

Cell centre/Cell Edge

Double StreamPrecoding

2/4 Lowcorrelation

Low Speed Higher Datarates

Cell Centre

MU-MIMO 2/4 Lowcorrelation

Low Speed Higher Datarates

Cell Centre

CodebookBeam-forming

1 Highcorrelation

Low Speed Lower Datarates

Cell Edge

Non CodebookBeam-forming

1 Highcorrelation

Low Speed Lower Datarates

Cell Edge






LTE Antenna Correlation

Two antenna at eNB Four antenna at eNB

Case 2: Low Correlation (10 λ )Be suitable for above 2GHz

Ant1 Ant2

Case 3: Low Correlation(4 λ or 10 λbetween two Pairs )

Ant1 Ant2

Ant3 Ant4

Case 4: High correlation (0.5 λ )

Ant1 Ant2 Ant3 Ant4

Case 1: Medium Correlation (4 λ )

Ant1 Ant2

Antenna application selectionIn simple multi-paths environment, such as rural area, High correlation antenna (case 4) is usually usedfor increasing cell radius.In complex multi-paths environment, such as urban area, low correlation antenna (case1,case2 andcase3) are usually used for increasing peak data rates.

Case 1Basic requirement for LTE initial development;Be suitable for most cases; high/low mobility speed, high/low correlation channel fading;The performance is a bitter lower than Case 2,Be suitable for Mode 2, Mode 3, Mode 4 and Mode 5.

Case 2Be suitable for hot-spot area and rich multi-path environment;Improve System capacity;Be difficult to install, especially for the frequency below 2GHz;Be suitable for Mode 4 and Mode 5;

Case 3Be suitable for all modes;The most benefit compared to two antenna ports is to improve uplink coverage due to four antenna

ports at Base Station;May not enough space to install;Case 4

Be suitable for Mode-6;Be suitable for large area coverage, such as rural area coverage;

Consideration on the select of LTE antenna typesIn the initial development, Case 1 is a better choice; It can develop the LTE network in most scenarios;Case 2 can be used in urban area where there is higher data rate requirement and rich multi-pathenvironment;Case 3 and Case 4 can be used in the second network development. It can Improve LTE network area,especially for uplink.






MIMO Deployment Consideration

n Scenario A

n Scenario B

n Scenario C

Linear Antenna

Cross-polarization1~3F

4~6F

7~9F

10~12F

13~15F

16~18F

19~21F

22~24F

25~27F

28~30F

31~33F

34~36F

37~39F

40~42F

43~45F

46~48F

Scenario ALarge Coverage, such as rural area, traffic highways;Good Los condition, simple multi-path environment;Mode 6, Codebook Beam-forming;Four transmit antenna with half wavelength spacing;Increase about 4dB in Link Budget.

Scenario BUrban, suburban, hot-spot area, Multi-path environment;Focus on Capacity rather than coverage;2/4 transmit antenna with Cross polarization;Low mobility: Mode 4, CL SM;High mobility: Mode 3 and Transmit Diversity.

Scenario C

Indoor Coverage;Mode 5, MU-MIMO;For Indoor coverage, MU-MIMO are

Similar with SDMA;One user uses a radio resource in one floor,

while another user can use the same radioresource in another floor due to low correlation

between different floors.






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3 Lte Bt04 e2 1 Mimo Principle-34