MIMO Mode Control
Overview
Overview
• Main contribution to high spectral efficiency
• MIMO is the deployment of multiple antennas at Tx and Rx
• 3GPP defines 7 DL transmission modes
• RL30 allows for DL:
- Transmission
on single antenna port (SISO/SIMO)
- TX diversity (2x2)
- Static open loop spatial multiplexing (2x2)
- Dynamic open loop: TX diversity (2x2)
open loop spatial multiplexing
- Adaptive closed loop (Single stream CL SM
Dual stream CL SM)
Overview
MIMO
Data Transmission
Number of Antennas
Number of Users
SISO
SU-MIMO
(Single Input Single Output)
(Single User MIMO)
pre-coding
Pre-Coding
(beamforming)
single data stream sent over
multiple input antennas
X
…
MISO
…
(Multiple Input Single Output)
…
Spatial Multiplexing
X1
…
Xn
pre-coding
multiple data stream sent over
multiple input antennas
SIMO
(Single Input Multiple Output)
…
…
…
MIMO
(Multiple Input Multiple Output)
Diversity Coding
single data stream sent over
multiple input antennas
with different coding
e.g. CDMA soft handover
MU-MIMO
…
…
Multiple-Input Multiple-Output MIMO Principle (1/2)
Signal from jth Tx antenna
Sj
T1
R1
MIMO
Input
T2
R2
•
•
•
•
•
•
Tm
MxN
MIMO
system
Processor
Output
Rn
• MIMO: Multiple-Input Multiple Output
• M transmit antennas, N receive antennas form MxN MIMO system
• huge data stream (input) distributed toward m spatial distributed antennas; m parallel bit streams (Input 1..m)
• Spatial Multiplexing generate parallel “virtual data pipes”
• using Multipath effects instead of mitigating them
MIMO Principle (2/2)
Signal from jth Tx antenna
Signal at ith Rx antenna
h1,1
Sj
T1
hn,1
Yi
h2,1
h1,m
h1,2
R1
h2,2
Input
T2
hn,2
•
•
•
MIMO
h2,m
Processor
Output
•
•
•
hn,m
MxN
Tm
R2
Rn
MIMO
H=
h1,1
h1,2
•••
h1,m
h2,1
h2,2
•••
h2,m
•
•
•
•
•
•
hn,1
hn,2
•
•
•
•••
hn,m
• Receiver learns Channel Matrix H
• inverted Matrix H-1 used for recalculation
of original input data streams 1..m
m
yi = ∑ hi , j ∗ s j + ni
j =1
ni: Noise at receiver
3GPP Rel8 Transmission Modes (1/2)
Mode 1
Mode 3
•Single antenna port; port 0
•1 TX antenna transmitting always on
•Open loop spatial multiplexing.
•Multiple antennas transmitting
port 0.
different signals.
•No feedback from the UE used.
•Improves user data rate.
Mode 2
•Transmit diversity.
•Multiple antennas transmit same
signal.
•Improves SINR.
Mode 4
•Closed Loop spatial multiplexing.
•Multiple antennas transmitting
different signals.
•Feedback from the UE used.
•Improves user data rate.
3GPP Rel8 Transmission Modes (2/2)
Mode 5
Mode 7
•Multi user MIMO.
•Multiple antennas transmitting to
•Single Antenna port; port 5.
•Beamforming.
•UE specific reference signals are
different UEs in the cell.
•Increase sector capacity.
Mode 6
•Closed-loop Rank=1 precoding.
•Beamforming.
•UE signals back the suitable precoding
for the beamforming operation.
generated for feedback.
RL30 supported transmission modes (DL)
• Single-antenna port; port 0
• Transmit diversity
RL10 (MIMO: max 2x2)
• Open-loop spatial multiplexing
• Dynamic Open loop MIMO
• Closed-loop spatial multiplexing
RL20 enhancements; max (2x2)
numOfTxPorts
dlMimoMode
Number of antenna ports
LNCEL; 1 (0), 2 (1); 2 (1)
Number of antenna ports
LNCEL; SingleTX (0), TXDiv (1),
Static Open Loop MIMO (2),
Dynamic Open Loop MIMO (3),
Closed Loop Mimo (4); TxDiv (1)
Overview
Single antenna port transmission
Single antenna port transmission
• 1x1 SISO or 1x2 SIMO
• Supported: DL and UL
• Flexi eNB supports 2-branch RX diversity (future: 4-branch)
- SINR enhanced
- Based on Maximum Ratio Combining (MRC)
- Additional gain from MRC: up to 6 dB (10% BLER, depending on conditions)
- Requires: uncorrelated antennas, x-polarized or d > 10 x wavelength
Transmission on a single antenna port, port 0: DL processing
Layer
Mapper
Precoding
Complex symbols after
scrambling and modulation
1 Layer
(Rank = 1)
RE mapping
OFDM signal generation
Transmit diversity
Transmit Diversity
• 2x2 based on Space Frequency Block Coding (SFBC); future: also 4x4
• Supported: DL
• Increases robustness, enhances cell edge performance
• Link budget gain: min 3 dB wrt 1x2 case (Tx power per Tx branch as in single ant. case)
capacity and coverage enhancements
• Rank 1 transmission, i.e. no multiplication of data rates
• aka Alamouti scheme
• Coverage improvement example:
- 592 m 808 m (dense urban)
- 694 m 948 m (urban)
- 2024 m 2970 m (suburban)
- 7665 m 11248 m (rural)
Single antenna Tx
Tx Div
Tx Diversity
Example: 2 antenna ports
Symbols after scrambling
and modulation,
1 code word
RE mapping, OFDM signal
2 layers (but: rank = 1)
y(0)
x(0)
Layer
Mapper
 y ( 0 ) ( 2i ) 
1
 (1)


 y ( 2i )  = 1  0
 y ( 0 ) ( 2i + 1) 
2 0
 (1)


1
 y ( 2i + 1) 
0
j
−1 0
1
0
0 − j
Precoding
y(1)
x(1)
0   Re

j   Re
j   Im

0   Im
(x
(x
(x
(x
)
)
)
)
(i ) 

(1)
(i ) 
(0)
(i ) 

(1)
(i ) 
(0)
X*
- X*
Feedback:
CQI
RI
Open loop spatial multiplexing
OL Spatial Multiplexing
Overall precoding is given by:
• Rank 2 transmission throughput enhancements
• 2 code words
• Precoding based on large delay CDD: W D U
• code book (no PMI feedback, i.e. open loop):
1 1 0 
W´= WxP with P =UxD


2 0 1 
precoding matrix
W:
1 1 1 


2 1 −1
D:
0 
1
0 e − j 2πi 2 


U:
1 
1 1
1 e − j 2π 2 
2

1 1 1 


2  j − j
Layer
Mapper
Precoding
2 data streams are supported
RE map, OFDM signal
Symbols after scrambling and modulation, 2 code words
Feedback:
*CDD = Cyclic Delay Diversity
CQI
RI
Closed loop spatial multiplexing
CL Spatial Multiplexing single stream
• closed loop rank 1 with precoding
• 1 code word
• Precoding w/o CDD: matrix W
1 1

2 1
1 1
 
2 −1
• code book based
precoding matrix
W:
• no code book restriction
• UE feedback: precoding matrix indicator (PMI)
Layer
Mapper
1 1 
 
2  j
1 1 
 
2 − j 
Precoding
1 data stream
Feedback:
Symbols after scrambling and modulation, 1 code word
CQI
RI
PMI
CL Spatial Multiplexing dual stream
• Rank 2 transmission throughput enhancements
• 2 code words
• Precoding w/o CDD
• code book based
precoding matrix W:
•UE feedback: precoding matrix indicator (PMI)
Layer
Mapper
1 1 1 


2 1 −1
1 1 1 


2  j − j
Precoding
2 data streams are supported
Feedback:
CQI
RI
PMI
Dynamic Open loop MIMO
Dynamic Open loop MIMO
Depending on Radio Conditions:
switch between Transmit Diversity and Spatial Multiplexing
- Open loop MIMO Switch Algorithm
- Open loop adaptive MIMO Algorithm
- Support of UE Capabilities
- UE basis
- CQI and Rank Information: used as switching criteria
Spatial
Multiplex
Diversity
x
Dynamic MIMO mode
Simulation Results (Source 4GMAX)
Dynamic (Adaptive) OL Switching
Various parameters are to support adaptive switching between 1-stream Transmit
Diversity and 2-stream Spatial Multiplexing:
• mimoOlCqiThD - This defines the CQI Threshold
Downgrade Switch::
for fallback to Open Loop MIMO diversity (in CQI).
• mimoOlCqiThU - This defines the CQI Threshold
for activation of Open Loop MIMO Spatial
CQI).
• mimoOlRiThD - This defines the Rank Threshold
for fallback to Open Loop MIMO diversity.
• mimoOlRiThU - This defines the Rank Threshold
for activation of Open Loop MIMO Spatial Multiplexing.
mimoOlCqiThD
CQI Threshold For
Fallback To Open Loop
MIMO diversity
LNCEL; 0...16; 0.1 ; 7
mimoOlCqiThU
CQI Threshold For
Activation Of Open Loop
MIMO Spatial
Multiplexing
LNCEL; 0...16; 0.1 ; 8
If
mimoCQI <= mimoDivCqiThDownOL
or
Multiplexing (in
mimoRANK <= mimoDivRiThDownOL
Upgrade Switch :
If
mimoCQI > mimoSmCqiThUpOL
and
mimoRANK > mimoSmRiThUpOL
mimoOlRiThD
Rank Threshold For
Fallback To Open Loop
MIMO diversity
LNCEL; 1...2; 0.05 ; 1.4
mimoOlRiThU
Rank Threshold For
Activation Of Open Loop
MIMO Spatial
Multiplexing
LNCEL; 1...2; 0.05 ; 1.6
Dynamic Open Loop MIMO mode
CQI
SM
SM
mimoOlCqiThU
mimoOlCqiThD
Time
RI
Filtered:
Filtered
cqi, ri
mimoOlRiThU
Inactivity:
Inactivity:
Aging
aging
applied
mimoOlRiThD
Time
Adaptive Close loop MIMO
MIMO Adaptive Closed Loop
• Feature LTE703 defines the use of Adaptive Closed Loop (CL) MIMO.
• The eNB scheduler selects Spatial Multiplexing dynamically while applying
closed loop MIMO for two antennas.
• The adaptive algorithm provides the gain of high peak rates (dual stream) when
close to the cell and good cell edge performance (single stream).
• Spatial multiplexing is applied only for the PDSCH.
Dual
Stream
x
x Adaptive Switching
Single
Stream
Dynamic (Adaptive) CL Switching
Various parameters are added to RL15TD to support adaptive switching between
CL MIMO 1 CW Mode and CL MIMO 2 CW Mode:
• mimoClCqiThD - This defines the CQI Threshold
for fallback to closed loop MIMO single codeword
transmission (in CQI).
• mimoClCqiThU - This defines the CQI Threshold
for activation of closed loop MIMO dual codeword
transmission (in CQI).
• mimoClRiThD - This defines the Rank Threshold
for fallback to closed loop MIMO single codeword
transmission.
• mimoClRiThU - This defines the Rank Threshold
for activation of closed loop MIMO dual codeword
transmission.
mimoClCqiThD
mimoClCqiThU
mimoClRiThD
CQI Threshold For
Fallback To CL MIMO
1 CW Mode
LNCEL; 0...16; 0.1 ; 7
CQI Threshold For
Activation Of CL MIMO
2 CW Mode
LNCEL; 0...16; 0.1 ; 8
Rank Threshold For
Fallback To CL
MIMO 1 CW Mode
LNCEL; 1...2; 0.05 ;
1.4
mimoClRiThU
Rank Threshold For
Activation Of CL MIMO 2
CW Mode
LNCEL; 1...2; 0.05 ; 1.6
Dynamic Close Loop MIMO mode
CQI
2CW
2CW
mimoClCqiThU
mimoClCqiThD
Time
RI
Filtered:
Filtered
cqi, ri
mimoClRiThU
Inactivity:
Inactivity:
Aging
aging
applied
mimoClRiThD
Time
Parameters
Parameters Summary
Name
Object Abbreviatio Range
n
Downlin LNCE
k MIMO L
Mode
dlMimoMod
e
SingleTX
(0), TXDiv
(1), Static
Open Loop
MIMO (2),
Dynamic
Open Loop
MIMO (3),
Closed
Loop Mimo
(4)
LNCE
MIMO
compen L
sation
dlpcMimoCo 0...10 dB,
mp
step 0.01
dB
Description
Default
The used DL mimo mode for each physical channel is the following:
0: Single Stream Downlink: All downlink physical channels are transmitted using this
mode;
1: Single Stream Downlink Transmit Diversity: All downlink physical channels are
transmitted using this mode;
2: Dual Stream MIMO Spatial Multiplexing: SRB1 (DCCH) and RBs(DTCH) on PDSCH
are transmitted using Dual Stream MIMO with spatial multiplexing; SRB0 (CCCH),
BCCH and PCCH on PDSCH and all other physical channels are transmitted using
Single Stream Downlink Transmit Diversity;
3: Dynamic Open Loop MIMO: SRB1 (DCCH) and RBs(DTCH) on PDSCH are
transmitted using either Single Stream Downlink Transmit Diversity or Dual Stream
MIMO with spatial multiplexing depending on radio conditions; SRB0 (CCCH), BCCH
and PCCH on PDSCH and all other physical channels are transmitted using Single
Stream Downlink Transmit Diversity;
4: Dynamic Closed Loop MIMO: SRB1 (DCCH) and RBs(DTCH) on PDSCH are
transmitted using either Single Stream Downlink Transmit Diversity or Single or Dual
Stream MIMO with Closed Loop spatial multiplexing depending on radio conditions and
UE category; SRB0 (CCCH), BCCH and PCCH on PDSCH and all other physical
channels are transmitted using Single Stream Downlink Transmit Diversity
TXDiv (1)
The parameter determines the power compensation factor for antenna-specific
maximum power in case of a downlink transmission using at least two TX antennas.
This means that every single subcarrier power determined for multiple TX antenna
transmission is reduced by this factor. The parameter does not apply in case of a single
TX (TM1) transmission, and thus neither affects the power of cell-specific reference
signal transmission. Note that only the limited set of dlpcMimoComp values (0dB,
1.77dB, 3dB, 4.77dB, 6dB) can be communicated to the UE due to p-a signaling
restrictions and the extended range has been determined only for finetuning purposes.
Please be informed that Nokia Siemens Networks does not quarantee a successful DL
transmission using amplitude dependent modulations, especially 64QAM, if other
values than the values presented in the limited set (0dB, 1.77dB, 3dB, 4.77dB, 6dB) are
used.
0 dB
Parameters Summary
Name
Object
Abbreviation
Range
Description
Defaul
t
CQI Threshold For Fallback
To CL MIMO 1 CW Mode
LNCEL
mimoClCqiThD
0...16, step
0.1
CQI Threshold for fallback to closed loop
MIMO single codeword transmission (in CQI)
7
CQI Threshold For
Activation Of CL MIMO 2
CW Mode
LNCEL
mimoClCqiThU
0...16, step
0.1
CQI Threshold for activation of closed loop
MIMO dual codeword transmission (in CQI)
8
Rank threshold for fallback
to CL MIMO 1 CW mode
LNCEL
mimoClRiThD
1...2, step
0.05
Rank threshold for fallback to Closed Loop
MIMO single Code Word transmission.
1.4
Rank threshold for
activation of CL MIMO 2
CW mode
LNCEL
mimoClRiThU
1...2, step
0.05
Rank threshold for activation of Closed Loop
MIMO dual Code Word transmission.
1.6
CQI threshold for fallback to LNCEL
MIMO diversity
mimoOlCqiThD
0...16, step
0.1
CQI threshold for fallback to Open Loop MIMO
diversity (in CQI).
7
CQI threshold for activation
of OL MIMO SM
LNCEL
mimoOlCqiThU
0...16, step
0.1
CQI threshold for activation of Open Loop
MIMO Spatial Multiplexing (in CQI).
8
Rank threshold for fallback
to MIMO diversity
LNCEL
mimoOlRiThD
1...2, step
0.05
Rank threshold for fallback to Open Loop
MIMO diversity.
1.4
Rank threshold for
activation of OL MIMO SM
LNCEL
mimoOlRiThU
1...2, step
0.05
Rank threshold for activation of Open Loop
MIMO Spatial Multiplexing.
1.6
Timer for aperiodic CQI /
PMI feedback requesting
LNBTS
cqiAperPollT
0...100 TTI,
step 1 TTI
This parameter defines a timer in TTIs for
polling aperiodic CQI / RI / PMI feedback. The
scheduler handles the aperiodic feedback
requesting based on this timer.
3 TTI
Parameters Summary
Name
Object
Timer for aperiodic
CQI / PMI feedback
requesting
Abbreviation
Range
Description
Default
LNBTS cqiAperPollT
0...100
TTI, step
1 TTI
This parameter defines a timer in TTIs for polling
aperiodic CQI / RI / PMI feedback. The scheduler
handles the aperiodic feedback requesting based
on this timer.
3 TTI
DL AMC CQI comp
for CL MIMO SM
with RI1
LNBTS cqiCompSmRi1Cl
-10...0,
step 0.1
The parameter defines the CQI compensation value
for DL AMC when Spatial Multiplexing transmission
mode is used but Rank Indication of 1 is received
from the UE. Applicable when the Closed Loop
MIMO Spatial Multiplexing has been configured to
use i.e. when dlMimoMode parameter is 4. This
parameter is vendor-specific.
-3
DL AMC CQI comp
for Dynamic OL
MIMO SM with RI1
LNBTS cqiCompSmRi1Ol
-10...0,
step 0.1
The parameter defines the compensation value CQI -3
for DL AMC for when the Spatial Multiplexing
transmission mode is used but a Rank Indication of
1 is received from the UE. Applicable when dynamic
Open Loop MIMO Spatial Multiplexing has been
configured to use i.e. when the dlMimoMode
parameter is 3. This parameter is vendor-specific.
DL AMC CQI comp
for CL MIMO TXdiv
with RI2
LNBTS cqiCompTdRi2Cl
0...10,
step 0.1
The parameter defines the compensation value CQI
for DL AMC for when TX diversity transmission
mode is used but a Rank Indication of 2 is received
from the UE. Applicable in the case when Closed
Loop MIMO Spatial Multiplexing has been
configured to use i.e. when the dlMimoMode
parameter is 4. This parameter is vendor-specific.
3
Parameters Summary
Name
Object
DL AMC CQI comp
for Dynamic OL
MIMO TXdiv with
RI2
Abbreviation
Range
Description
Default
LNBTS cqiCompTdRi2Ol
0...10, step 0.1
The parameter defines the compensation
value CQI for DL AMC for when the TX
diversity transmission mode is used but a
Rank Indication of 2 is received from the
UE. Applicable when Dynamic Open Loop
MIMO Spatial Multiplexing has been
configured to use i.e. when the
dlMimoMode parameter is 3. This
parameter is vendor-specific.
3
CQI compensation
when reported RI=2
LNBTS mimoOlCqiComp
0...10, step 0.1
CQI compensation applied to CQI
measurements when reported RI=2 (in
CQI). The reported CQI in Open Loop
Spatial Multiplexing case is smaller than
for the diversity transmission. With this
compensation a normalization towards
diversity is obtained.
3
CQI Compensation
When Reported RI
Equals 2 In CL SM
LNBTS mimoClCqiComp
0...10, step 0.1
CQI Compensation applied to closed loop
CQI Measurements when reported RI=2
(in CQI). The reported CQI in closed loop
dual codeword transmission case is
smaller than for single codeword
transmission. By this compensation a
normalization towards single codeword
case is obtained.
This parameter is vendor specific.
3
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