Multipath Simulator (MPS)
for over the air system tests
Jan Welinder1, Lars Fast1, Thomas Bolin2
Presented by Christer Karlsson1
1SP
Technical Research Institute of Sweden,
2Sony Ericsson Mobile Communications AB,
RFMTC 2009
“Chase - the wireless future with Antenna Systems Excellence from CHALMERS”
Traditional radio test
Conditions:
- line of sight
Measurements:
- frequency use
- radiated power
- sensitivity
- etc.
“Chase - the wireless future with Antenna Systems Excellence from CHALMERS”
Wave propagation in the reality
- Multipath and
- Mobility
results in
- Delay spread
- Doppler spread
- Angular distribution
(picture WinProp)
“Chase - the wireless future with Antenna Systems Excellence from CHALMERS”
Features of modern communication
systems
• Adaptivity – power, modulation and coding is adapted
to load and conditions (sometimes in intervals of 1
ms)
• Channel estimation – equalizers and Rake receivers
are used to compensate for the time dispersion
• Antenna systems – multiple antennas are used to
fight fast fading (diversity) and together with signal
processing increase throughput/reliability (MIMO)
“Chase - the wireless future with Antenna Systems Excellence from CHALMERS”
New methods are required for
new systems
• Line of sight is not adequate
• Mobility is currently not included
• Main figure of merit is not only
sensitivity/power but also throughput
• Realistic performance is estimated in
non-repeatable drive tests
“Chase - the wireless future with Antenna Systems Excellence from CHALMERS”
•
•
-
Multipath environment
ray
emulation
The MPS:
generates a number (16) of independent rays
works at the carrier frequency and is independent of modulation etc.
connects base station and terminal directly – true system test
Each ray is described by its individual:
direction (2D – horizontal plane)
polarization (vertical or horizontal)
amplitude
Doppler shift (continuous phase shift)
delay (delay lines)
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MPS block diagram – Next version
Delay
Split 8:32
Phase shift
Attenuation
Combiner 32:16
Antennas
Split 2:8
MIMO Tx1
Base
station Tx2
User
equipment
“Chase - the wireless future with Antenna Systems Excellence from CHALMERS”
Current status:
Experimental MPS system built by SP and
Sony Ericsson
“Chase - the wireless future with Antenna Systems Excellence from CHALMERS”
Simulated fading in time domain 8 antennas (Ez in array center)
Ez
1
0,1
0
100
200
300
400
500
Sample
Narrowband signal
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Probability distribution 2, 4 and 8
antennas (Ez in ring centre)
3000
2500
2000
Rayleigh
1500
1000
700
500
600
0
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
500
400
300
200
100
1000
0
0,0
0,5
1,0
1,5
2,0
2,5
power limitation
0
0
1
2
3
4
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5
Preliminary results on
experimental MPS
•
Some initial measurements are carried out:
•
•
•
•
Fading statistics
Mean effective gain measurement
BER – WCDMA, GSM (phone and CMU 200)
Throughput HSDPA (phones and computer)
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Influence of Doppler spread
Computer - category 6
THroughput (kbit/s)
2000
5000
0 km/h
0,7 km/h
7 km/h
25 km/h
70 km/h
Througput (kbit/s)
Phone - category 3
2500
1500
1000
16QAM
16QAMfading
4000
3000
0 km/h
2000
70 km/h
500
1000
0
-10
-20
-30
Relative power (dB)
-40
-50
0
-10
-15
-20
-25
-30
-35
-40
-45
Relative power (dB)
“Chase - the wireless future with Antenna Systems Excellence from CHALMERS”
-50
Influence of delay profile
Delay off
Delay part 1
5000
Throughput (
kB/s)
1 us delay line is added
to 4 of the 8 antennas
Computer
1 us delay
0 km/h Doppler
4000
3000
2000
1000
0
-70
-80
-90
-100
-110
Discone Rx power (dBm)
“Chase - the wireless future with Antenna Systems Excellence from CHALMERS”
Conclusions
• The multipath fading simulator generates a flexible
2D “over the air” test environment that can be used
for terminal characterization.
• The MPS is a complement to current systems
• Its main advantage is its potential ability to emulate
realistic 2D wave propagation models including
– Angle of arrival
– Delay spread
– Doppler spread
“Chase - the wireless future with Antenna Systems Excellence from CHALMERS”