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
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Content
LTE MIMO IntroductionTransmit Modes Theory IntroductionMIMO PerformanceMIMO Application
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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!
.
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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.
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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
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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 )
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Why select MIMO ?
finit
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Content
LTE MIMO IntroductionTransmit Modes Theory IntroductionMIMO PerformanceMIMO Application
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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
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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.
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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.
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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
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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
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Spatial Multiplexing
n Code words + Layers + Tx antennas
n Different data content ## Increase throughput
n More complex precoding ## Code book
15
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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
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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.
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Content
LTE MIMO IntroductionTransmit Modes Theory IntroductionMIMO PerformanceMIMO Application
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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
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MIMO Simulation Results-Case 2
n Cell Spectrum efficiency n Cell Edge SE (5% CDF)
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
Case 2: Simulation Results
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
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MIMO Simulation Results-Case 3
n Cell Spectrum efficiency n Cell Edge SE (5% CDF)
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
Case 3: Simulation Results
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
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MIMO Simulation Results
n Cell Spectrum efficiency n Cell Edge SE (5% CDF)
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
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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.
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Content
LTE MIMO IntroductionTransmit Modes Theory IntroductionMIMO PerformanceMIMO Application
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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;
Spatial Multiplexing
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;
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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;
Spatial Multiplexing
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;
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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
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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;
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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.
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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
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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.
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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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