RFMTC’09
Measuring MIMO Throughput as a
Function of Channel Simulation Using
Dual Reverberation Chambers
Mats Andersson
CEO
Bluetest AB
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RFMTC’09
Optimizing multiport antenna performance
l
l
l
l
l
Complex with software, especially
efficiency.
Most small multi-port antennas are/will
be used in fading environment s.
Traditional antenna test facilities have
no fading.
MIMO and diversity techniques rely on
fading.
Reverberation chambers have fading
with a Rayleigh distribution.
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RFMTC’09
What is a reverberation chamber?
Creates scattering environment
l Average transmission level in
chamber proportional to
Total radiated power
Radiation efficiency of antenna
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l
Uniform field environment
when averaged over large
number of independent field
samples
Rayleigh faded signal
transmission
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Received power (dB)
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4
2
0
-2
-4
-6
-8
-10
0
0.5
1
1.5
Time
2
2.5
3
3.5
RFMTC’09
Simulated Rayleigh field distribution
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RFMTC’09
Rayleigh fading
• Transmission samples in the reverberation chamber are Rayleigh
distributed => Reverberation chamber = HW fading simulator.
• It is possible extract important parameters for multi-antenna units:
– Diversity gain
– MIMO throughput
– ...
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RFMTC’09
Comparison of radiation efficiency
l
Large near-field chamber vs. large Bluetest chamber
TABLE I
COMPARISON OF MEASURED AND SIMULATED RADIATION EFFICIENCY
Antenna
Phantom M ounted Efficiency at
2.45 GHz (%) [equivalent loss, dB]
Simulation
Near-Field
Reverb
HM MPA 10mm
49.0 [3.1]
38.9 [4.1]
42.8 [3.7]
HM M PA 5 mm
45.0 [3.5]
37.6 [4.2]
37.1 [4.3]
M onopole
58.5 [2.3]
51.0 [2.9]
53.4 [2.7]
M PA-F
65.6 [1.8]
67.0 [1.7]
75.1 [1.2]
M PA-S
65.7 [1.8]
61.0 [2.1]
61.2 [2.1]
From measurements by Queen's University Belfast, ”In Situ Measurement of UHF
Wearable Antenna Radiation Efficiency Using a Reverberati on Chamber”, IEEE Antennas
and Wireless Propagati on Letters, Vol. 7, 2008
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RFMTC’09
TRP Repeatability
Channelnr
975 (880 MHz)
dBm
35 (897 MHz)
dBm
124 (915 MHz)
dBm
Pos1_120_40_meas 1
30,81
31,13
29,77
Pos1_120_40_meas 2
30,78
31,06
29,76
Pos1_120_40_meas 3
30,76
31,08
29,72
Pos1_120_40_meas 4
30,76
31,01
29,66
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RFMTC’09
Connected reverberation chambers
H tot = H 1 * K * H 2
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RFMTC’09
MIMO capacity for 2-by-2 system in
connected RC's
( (
C (i ) = log 2 det I + r 2 H (i )H (i ) *
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))
RFMTC’09
More than two connections
H tot = H 1 * K * H 2
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RFMTC’09
More than two connections –
asymptotic behavio r
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RFMTC’09
WLAN in connected chambers
Reverberation chamber 1
Reverberation chamber 2
Test router
Test laptop
Control laptop with throughput software
MMMbps
•
Base station (router) and termi nal placed in
different chambers
•
Up to three c onnections between the
chambers tested
•
Increased throughput with more connections
•
Preliminary results
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RFMTC’09
New and future multiport antenna
measurements
• Multi-user MIMO
• Opportunistic scheduling, tests of scheduling software
• Small base stations (pico, femto, ...)
• Effects of amplifiers and recievers
• Multi-RBS MIMO
• ...
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RFMTC’09
Conclusions
• Connected reverberation chambers can be used as a low
cost channel emulator.
• The measurement s are in very good agreement with
simulations.
• Connected reverberation chamber opens up possibilities
for completely new types of measurement s such as:
– Simultaneous up and downlink throughput using
different channel models, Multi-user MIMO,
Opportunistic scheduling, ...
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