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Greater insight. Greater confidence. Accelerate next-generation wireless.
Verify and Visualize your LTE MIMO Beamforming Signals
Craig Grimley, R&D Developer
Electronic Measurement Group, Agilent Technologies
LTE World Summit, May 2012
© Agilent Technologies
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What is MIMO Beamforming ?
Multi-antenna techniques
Introduction to beamforming
What are benefits ?
Benefits for cellular network
Use within LTE transmission modes
What are the test verification challenges ?
Typical TD-LTE eNB test configuration
Agilent 8-Chan N7109A SA + 89600 VSA test solution
Verify and Visualize your
LTE MIMO Beamforming Signals
LTE World Summit, May 2012
© Agilent Technologies
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LTE World Summit, May 2012
© Agilent Technologies
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Multi-Antenna Techniques
Tx Rx :
SIMO
- Rx diversity
- Rx smart antenna
(beamforming)
- Improved SINR
Tx Rx :
MISO
- Tx diversity
- Tx smart antenna
(beamforming)
- Improved SINR
Tx Rx : :
MIMO
- Tx/Rx diversity
- Tx/Rx smart antenna
(beamforming)
- Spatial multiplexing
- Improved SINR
or
Improved Spectral
Efficiency / Data Rates
Tx Rx
SISO - No diversity protection
against channel fading
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LTE World Summit, May 2012
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Multi-Antenna Techniques
Tx Diversity • Orthogonally modified redundant copies
transmitted across multiple antenna’s
• Robustness to channel fading / noise
S1 S0
-S1*
Tx0
Tx1 S0*
Frequency domain
Spatial Multiplexing • Simultaneous unique data streams
transmitted across multiple antenna’s
• Improved spectral efficiency / throughput
S0
S1
Tx0
Tx1
Beamforming • Per antenna weighted signal copies
transmitted across multiple antenna’s
• Coherent beamforming gain (dB) at receiver
S0.w0
S0.w1
Tx0
Tx1
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Introduction to Beamforming
Relative field strength example
1 Antenna Element
|
-90 deg
-60 deg
-30 deg
0 deg
+30 deg
+60 deg
+90 deg
Main Lobe = omnidirectional
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Introduction to Beamforming
Relative field strength example
2 Antenna Elements
Co-polarized 0.5 wavelength separation
0deg phase shift per element
| |
-90 deg
-60 deg
-30 deg
0 deg
+30 deg
+60 deg
+90 deg
Main Lobe = 0deg azimuth
Number of Nulls = 1 Constructive
Interference
Power Gain
Destructive
Interference
Power Null
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LTE World Summit, May 2012
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Introduction to Beamforming
Relative field strength example
3 Antenna Elements
Co-polarized 0.5 wavelength separation
0deg phase shift per element
| | |
-90 deg
-60 deg
-30 deg
0 deg
+30 deg
+60 deg
+90 deg
Main Lobe = 0deg azimuth
Number of Nulls = 2
Improved
Beam
Selectivity
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LTE World Summit, May 2012
© Agilent Technologies
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Introduction to Beamforming
Relative field strength example
4 Antenna Elements
Co-polarized 0.5 wavelength separation
0deg phase shift per element
| | | |
-90 deg
-60 deg
-30 deg
0 deg
+30 deg
+60 deg
+90 deg
Main Lobe = 0deg azimuth
Number of Nulls = 3
Improved
Beam
Selectivity
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LTE World Summit, May 2012
© Agilent Technologies
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Introduction to Beamforming
Relative field strength example
4 Antenna Elements
Co-polarized 0.5 wavelength separation
90deg phase shift per element
| | | |
-90 deg
-60 deg
-30 deg
0 deg
+30 deg
+60 deg
+90 deg
Main Lobe = -30deg azimuth
Number of Nulls = 3
Beam
Control
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-90 deg
-60 deg
-30 deg
0 deg
+30 deg
+60 deg
+90 deg
| | | |
4 Antenna Elements
Co-polarized 0.5 wavelength separation
90deg phase shift per element
LTE World Summit, May 2012
© Agilent Technologies
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Introduction to Beamforming
• Used in many technologies:
radar, sonar, seismology, wireless communications, radio astronomy, acoustics
• Takes advantage of multi-antenna interference patterns
Constructive (in-phase)
interference
Power Gain
Destructive (out-of-phase)
interference
Power Nulling
Antenna array geometry
+
Relative mag / phase
weightings
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• Coherent Beamforming Gain (dB)
Improved SINR observed at UE device
Increased throughput at cell-edge
Increased cell coverage or size
• Spatial Selectivity
Mitigate intra-cell interference
Mitigate inter-cell interference
Improve spectrum efficiency
(SDMA, Space Division Multiple Access)
LTE World Summit, May 2012
© Agilent Technologies
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eNB3
UE3
UE4
eNB1 eNB2
UE1
UE2
Null
Null
Benefits for Cellular Network
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LTE World Summit, May 2012
© Agilent Technologies
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3GPP Release 8:
TM1: SISO single antenna transmissions
TM2 : Tx Diversity using 2 or 4 antennas
TM3: Open-Loop SU-MIMO (Spatial Multiplexing)
TM4: Closed-Loop SU-MIMO
TM5: Closed-Loop MU-MIMO
TM6: Rank 1 Spatial Multiplexing
TM7: Single Layer Beamforming on Port 5
3GPP Release 9:
TM8: Dual Layer Beamforming on Ports 7 & 8
3GPP Release 10:
TM9: Up to 8 layer transmissions using Ports 7 to 14
LTE DL Transmission Modes
TM7 & TM8 Beamforming
is current TD-LTE
market focus
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Channel coding
Rate matching
Code block
concatenation
110 ,...,, Aaaa
110 ,...,, Bbbb
110 ,...,, rKrrr ccc
)(
1)(
1)(
0 ,...,, iDr
ir
ir r
ddd
110 ,...,, rErrr eee
110 ,...,, Gfff
Transport block
CRC attachment
Code block segmentation
Code block CRC attachment
LTE World Summit, May 2012
© Agilent Technologies
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LTE Signal Processing (TM7 & TM8) (Adapted from 3GPP 36.211 and 36.212)
ScramblingModulation
mapper
Layer
mapperPrecoding
Resource element
mapper
OFDM signal
generation
Resource element
mapper
OFDM signal
generationScrambling
Modulation
mapper
layers antenna portscodewords
Cell-specific RS (Reference Signal)
Can be weighted to produce sector wide common control Broadcast pattern
Possible when Num Physical Ports > Num CRS Ports
Cell-specific RS Broadcast pattern
PDSCH (Data)
Channel encoded and mapped onto 1 or 2 codewords (layers)
BF precoding is non-codebook based
BF precoding can vary per RB & per Subframe (TTI)
UE-specific RS (Reference Signal)
Mapped to associated TM7 / TM8 PDSCH RB allocations
Same BF precoding as per associated PDSCH RB
UE-specific RS
UE-specific pattern
UE1
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LTE World Summit, May 2012
© Agilent Technologies
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LTE Signal Processing (TM7 & TM8) (Adapted from 3GPP 36.211 and 36.212)
TM7
Single Layer
UE-specific RS
Port 5
TM8
Dual Layer
UE-specific RS
Port 7
Port 8
Common
Cell-specific RS
Port 0
Port 1
Port 2
Port 3
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A1 A2 A3 A4
A5 A6 A7 A8
LTE World Summit, May 2012
© Agilent Technologies
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Typical TD-LTE eNB Test Configuration
UE1
Uplink feedback
(SRS, CQI, PMI, RI)
UL RF
Channel
Emulator
2x8
DL RF
Channel
Emulator
8x2
~10dB
CAL
Coupler
eNB
RRH
eNB
BB
CAL
Ant 1
Ant 2
Ant 3
Ant 4
Ant 5
Ant 6
Ant 7
Ant 8
A1, A2, A3, A4 = +45 degree polarization
A1 A2 A3 A4
A5, A6, A7, A8 = -45 degree polarization
A5 A6 A7 A8
Common customer problem, need to verify:
RF Circulator
RF Atten
~0.5 * RF carrier wavelength spacing
eNB RF antenna calibration accuracy
BB beamforming weighting algorithm correctness
RF & EVM modulation quality for MIMO single or
dual layer
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LTE World Summit, May 2012
© Agilent Technologies
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UE1
Typical TD-LTE eNB Test Configuration
RF Splitter
Uplink feedback
(SRS, CQI, PMI, RI)
UL RF
Channel
Emulator
2x8
RF Circulator
RF Atten
DL RF
Channel
Emulator
8x2
~10dB
CALIBRATION REFERENCE
SIGNAL RF SOURCE & SPLITTER
Agilent
8-Chan
N7109A
Analyzer
Agilent 89600B VSA
~20dB
CAL
Coupler
eNB
RRH
eNB
BB
CAL
Ant 1
Ant 2
Ant 3
Ant 4
Ant 5
Ant 6
Ant 7
Ant 8
A1, A2, A3, A4 = +45 degree polarization
A5, A6, A7, A8 = -45 degree polarization
A1 A2 A3 A4
A5 A6 A7 A8
~0.5 * RF carrier wavelength spacing
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DL RF
Channel
Emulator
8x2
~10dB
UE1
LTE World Summit, May 2012
© Agilent Technologies
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Typical TD-LTE eNB Test Configuration
RF Splitter
Uplink feedback
(SRS, CQI, PMI, RI)
UL RF
Channel
Emulator
2x8
RF Circulator
RF Atten
CALIBRATION REFERENCE
SIGNAL RF SOURCE & SPLITTER
CAL
Coupler
eNB
RRH
eNB
BB
CAL
Ant 1
Ant 2
Ant 3
Ant 4
Ant 5
Ant 6
Ant 7
Ant 8
A1, A2, A3, A4 = +45 degree polarization
A5, A6, A7, A8 = -45 degree polarization
A1 A2 A3 A4
A5 A6 A7 A8
~0.5 * RF carrier wavelength spacing
Agilent
8-Chan
N7109A
Analyzer
~20dB
Agilent 89600B VSA
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LTE World Summit, May 2012
© Agilent Technologies
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Agilent 8-Chan N7109A SA + 89600 VSA
8 Channel
RF Spectrum
8 Channel
RF Time
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LTE World Summit, May 2012
© Agilent Technologies
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Agilent 8-Chan N7109A SA + 89600 VSA
IQ
Constellations
UE-specific
RS Weights
Cell-specific RS
Weights &
Impairments
UE-specific &
Common Broadcast
Antenna Beampatterns
EVM
Metrics
Detected
Resource
Allocations
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LTE World Summit, May 2012
© Agilent Technologies
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Agilent 8-Chan N7109A SA + 89600 VSA Ant Group 0
pattern
Ant Group 1
pattern
8 Channel
UE-specific RS
Mag/Phase Weights
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LTE World Summit, May 2012
© Agilent Technologies
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Agilent 8-Chan N7109A SA + 89600 VSA
Ant Group 1 Cell-RS Weights
8 Channel
Cell-RS
MIMO
Impairments
& Weights
Ant Group 0
pattern
Ant Group 1
pattern
Ant Group 0 Cell-RS Weights
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LTE World Summit, May 2012
© Agilent Technologies
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Agilent 8-Chan N7109A SA + 89600 VSA
LogMag (dB)
IQ Polar
Beamforming Gain (dB)
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LTE World Summit, May 2012
© Agilent Technologies
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Agilent 8-Chan N7109A SA + 89600 VSA
Provides an 8-channel phase coherent measurement solution to enable
verification and visualization of TD-LTE base station RF antenna
beamforming signals.
TD-LTE (TM7 & TM8) measurement solution
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LTE World Summit, May 2012
© Agilent Technologies
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Application Note: http://www.agilent.com/find/LTE-Forward
Youtube Video: http://www.youtube.com/watch?v=mj58aSOZ1Kc
8-Chan N7109A: http://www.agilent.com/find/N7109A
89600 VSA: http://www.agilent.com/find/89600
LTE: http://www.agilent.com/find/LTE
For more information…
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LTE World Summit, May 2012
© Agilent Technologies
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Thank you !