ESA PROJECT 1300008360
UWB RADIO FOR CABLE REPLACEMENT IN SATELLITES
TECHNICAL NOTE 1.1
“HARDWARE DESCRIPTION, ENVIRONMENT AND TEST PLAN”
© IMEC 2011
INTRODUCTION
Feasibility study for use of UWB radio for cablereplacements in intra-satellite communication.
Project contains 3 activities:
1.
Hardware description, environment and test plan
 Outcome: (TN1.1 = document)
2. Measurement campaign
 Outcome: (TN1.2a=Zip-file)
3. Test report and analyses
 Outcome: (TN1.2= > update of TN1.1)
 2 versions: with and without confidential information
This presentation reports on TN1.2
© IMEC 2011
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OUTLINE OF THE DOCUMENT
1 Introduction ................................................................................. 1
2 IEEE802.15.4a UWB air interface...........................................
3
3 Top-level description of IMEC UWB transceivers..... .........
11
4 Methodology................................................................................
27
5 Venus express Mock-up description ......................................
29
6 Channel Measurements and Modelling .................................
33
7 Simulation framework and results .........................................
67
8 Conclusions and recommendations.......................................
73
9 Bibliography...................................................................................
75
© IMEC 2011
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802.15.4A STANDARD
▸3 modes
=> mean Pulse repetition freq
- 15.6 MHz
- 3.9 MHz
- 62.4 MHz
▸4 submodes
-
=> PHY bitrate
27Mb/s
6.8 Mb/s
850 kb/s
110 kb/s
▸Off standard modes allow for other data rates as well
- Use of ASIP/ASIC combination makes TX/RX flexible!
- Unique to IMEC technology
© IMEC 2011
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METHODOLOGY
© IMEC 2011
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ENVIRONMENT & MEASUREMENTS
Parameters:
▸Satellite:
Channel measurements showed
the validity of these assumption
- Highly reflective environment
- Significant reflection up to one microseconds
▸BW:
- 1-11 GHz (covers much communication standards)
- Time resolution => 100 picoseconds
▸#FreqPoint > 1microsec/100picosec(=10k)
▸Nearest power of 2 => 16384 (DFT => FFT )
▸FreqStep = 610 kHz.
Result: H[f] => H(f)
© IMEC 2011
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FREQ TO DELAY
Freq domain
DFT
Delay domain
H[f,t] (=S21)
<=>
H[tau,t]
Only valid if channel is constant
•True if doors are closed
•Not guaranteed if doors are opened
© IMEC 2011
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MEASUREMENT REQUIREMENT
Measurement of H(f,t) takes approx 2 sec!
Nothing may move more than 0.5cm over 2
seconds in relevant area!
Relevant area = area relevant paths act.
Do relevant paths exit & return from Mock-Up?
 True if doors are closed
 False if doors are opened!
© IMEC 2011
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MEASUREMENT SETUP
=keyhole
Type
amount
remark
Closed doors
36
6 intra cavity, 28 inter cavity, path
Open doors
61
41*(5->6) + 20*(2->5)
Antenna position
21
8*(5->5) + 5*(6->5) + 7*(2->5)
© IMEC 2011
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CHANNEL MEASUREMENT RESULTS
PATH LOSS
0
UWB [500 MHz]
WLAN [20 MHz]
Raw Data [610kHz]
-10
1/f2
Channel Gain [dB]
-20
-30
-40
-50
-60
-70
3
4
5
6
7
Frequency [GHz]
8
9
Channel gain as a function of carrier frequency with a sliding
window.
© IMEC 2011
10
CHANNEL MEASUREMENT RESULTS
PATH LOSS
Path losses (units in dB) for inter cavity measurements.
Cavity
-20
Path
loss
-25
1
2
3
4
5
6
-26
-25
-27
-25
-27
-27
Rx in
1
Rx in
2
Rx in
3
Rx in
4
Rx in
5
Rx in
6
X
-34
-41
-49
-50
-58
-34
X
-47
-42
-56
-53
-41
-47
X
-54
-41
-52
-48
-41
-54
X
-52
-42
-50
-56
-41
-52
X
-39
-56
-52
-52
-42
-39
X
(dB)
-30
Channel Loss[dB]
Cavity
-35
Tx in 1
-40
Tx in 2
-45
Tx in 3
-50
Tx in 4
-55
-60
Tx in 5
Tx in 6
0
0.5
1
1.5
#Keyholes
2
2.5
3
Channel gain as a function of the number of keyholes
Large scale path loss
© IMEC 2011
CHANNEL MEASUREMENT RESULTS
IMPACT OF ANTENNA POSITION
LOS,
0
Close proximity
Channel Gain [dB]
-20
NLOS,
-40
-60
-80
-100
Antennae at opposite
Key holes
Measurement 1
Measurement 2
Measurement 3
Measurement 4
Measurement 5
Measurement 6
Measurement 7
Measurement 8
3
4
5
6
7
Frequency [GHz]
8
9
Intra cavity measurements VNA channel 1 (Tx) and VNA channel
2 (Rx) in cavity 5 with 8 different antenna position configurations.
© IMEC 2011
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CHANNEL MEASUREMENT RESULTS
IMPACT OF OPEN DOORS
-50
-55
-60
-65
-70
-75
3
4
5
6
7
8
9
10
000000
000001
000010
000100
001000
010000
100000
000101
001001
001100
010010
100001
100100
101000
001101
100101
101001
101100
101101
111111
Effect of opening and closing of doors on the link-budget for inter
cavity measurements VNA channel 1 (Tx) in cavity 2 and VNA
channel 2 (Rx) in cavity 5 with many different door configuration.
Doors 2 and 5 have the biggest impact.
•The opening of doors may lead to a channel gain loss up to 18 dB
© IMEC 2011
CHANNEL MEASUREMENT RESULTS
DELAY DOMAIN
RMS delay spread (units in ns) for inter cavity measurements.
-40
S21 [dB] Bandwidth [10 GHz]
Cavity
Real Measurement
Synthetic data
RMS
delay
spread
(ns)
-60
-80
Cavity
-100
Tx in 1
Tx in 2
-120
Tx in 3
-140
Tx in 4
-160
0
200
400
600
800 1000
time [ns]
1200
1400
1600
Real measured data for inter cavity measurement of cavity 1 to
cavity 3, and synthetically generated data with the aid of two
exponential functions and a noise floor describing the envelope.
© IMEC 2011
Tx in 5
Tx in 6
1
2
3
4
5
6
40.7
37.5
34.6
16.0
35.8
34.9
Rx in 1
Rx in 2
Rx in 3
Rx in 4
Rx in 5
Rx in 6
X
57.2
59.3
67.2
77.2
118.6
56.3
X
73.2
46.6
109.5
80.0
59.7
74.5
X
81.8
53.8
82.1
69.0
47.5
82.6
X
77.9
44.6
77.4
109.4
55.6
78.0
X
54.1
110.6
75.8
81.4
44.1
52.3
X
CHANNEL MEASUREMENT RESULTS
DELAY DOMAIN
Ricean factors (units in dB) for inter cavity measurements.
Raw data
Ricean fit
Rayleigh fit
16
Cavity
1
2
-17
14
3
-16
4
-14
5
-12
6
-18
-20
Density
12
Cavity
10
8
6
Rx
1
in
Rx
2
in
Rx
3
in
Rx
4
in
Rx
5
in
Rx
6
Tx in 1
X
-23
-22
-22
-22
-24
Tx in 2
-22
X
-24
-21
-24
-24
Tx in 3
-23
-22
X
-23
-22
-24
-22
-22
-22
X
-22
-22
-23
-24
-22
-23
X
-23
-24
-22
-24
-21
-23
X
4
Tx in 4
2
Tx in 5
0
0
0.02
0.04
0.06
0.08
0.1
Amplitude [V]
0.12
0.14
0.16
Tx in 6
Histogram of received signal voltage from 4 - 5 GHz and the
estimated Ricean and Rayleigh distribution for both VNA
channel 1 (Tx) and VNA channel 2 (Rx) in cavity 2.
Small scale fading is Rayleigh distributed
© IMEC 2011
in
CHANNEL MEASUREMENT RESULTS
MINIMUM AND MAXIMUM PATH LOSSES
0
20
-10
2  interval corresponding to Channel Gain [dB]
UWB [500 MHz]
WLAN [20 MHz]
Raw Data [610kHz]
Channel Gain [dB]
-20
-30
-40
-50
-60
-70
3
4
5
6
7
Frequency [GHz]
8
9
10
Intra cavity measurement in cavity 3 with 2σ confidence intervals
over 1GHz windows. Solid line, UWB, striped line, WLAN, dotted
line, Raw Data.
UWB [500 MHz]
WLAN [20 MHz]
18
16
14
12
10
8
6
4
2
0
0
0.5
1
1.5
#Keyholes
2
2.5
3
The 2σ confidence intervals corresponding to the channel gain
for the seven 1GHz windows for both intra and inter cavity
measurements as a function of the number of 12 x 12 cm
keyholes, i.e. hops.
•2σ 5 dB mean power gain variation due to small scale fading.
•Mean power mainly depends on cavity not on position
© IMEC 2011
SIMULATION RESULTS
Flexible 802.15.4a simulation environment
▸Matlab
Iff CRC passes
Added CRC16
Flexible PSDU
size
non-coherent
reception
Flexible Data rate/
Modulation scheme
© IMEC 2011
Noise equal to measured
RXFE noise-figure
Complex-valued
BB equiv. system model
17
SIMULATION RESULTS
PER as measure for performance:
▸most honest but worse-case performance criteria
-3
1
x 10
CRC
check
0.9
0.8
PHY HDR
decoding
0.7
Amplitude
0.6
Fine acquisition
0.5
SFD detection
0.4
0.3
Fine acquizition
Payload decoding
Preamble tracking and SFD Detection
0.2
0.1
preamble
SFD
PHY header and Data
SHR preamble
0
0
0.5
1
1.5
2
2.5
3
3.5
Time
4
5
x 10
Only successful reception if everything goes well.
© IMEC 2011
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PER WITH CLOSED DOORS
Many things can go wrong, but it does not;-)
Reasons:
▸Low average pathloss,
▸highly reflective environment
▸Keyholes are larger enough
▸Hardly no small-scale fading
▸UWB is able to resolve many
multipath components
© IMEC 2011
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PER WITH OPEN DOORS
Many things can go wrong, and here it does;-(
With 1 hop everything is fine
3 hops is too much
Reason:
• Energy leaks into environment,
lowering RX power
But:
• ‘only’ 10 dB improvement needed
• Link improvement are possible
• ↑TX power, ↓noise figure
• Tailor BB processing
• Network layer
© IMEC 2011
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CONCLUSION
The satellite’s radio channel is a high reflective/multipath-rich environment in which
radio signal are able to propagate from one cavity to the next.
The large scale path loss of the channel for a frequency range of 3-10 GHz varies
between -25dB (intra-cavity) to-58dB (cavity 1 to cavity 6) with closed doors.
The RMS delay spread varies between 40.7 ns (intra-cavity) and 118.6 ns (cavity 1 to
cavity 6).
The small-scale-fading for narrowband systems is Rayleigh distributed even in LOS
conditions. An example of such a narrowband system is 802.15.4. To obtain robust
communication links, some form of diversity will be needed.
UWB systems experience a mean power gain variation of at most 5 dB due to
small-scale-fading, due to its inherent frequency diversity.
The mean power gain of the channel depends mainly on the cavities of TX and RX,
i.e. the exact position of the TX/RX within these cavities has little impact.
© IMEC 2011
CONCLUSION
Opening of the satellite doors may lead to a decrease of the channel gain in the
order of 15-18 dB for intra cavity channel and 10-13 dBs for inter cavity channels;
depending on the contribution of the door as reflective object to the overall
channel transfer function.
The most difficult channels are measured from cavity 1 to cavity 6 with open doors
at high frequencies (6-10 GHz), where a mean power gain of -70 dB was recorded.
Imec’s current 802.15.4a-compliantUWB radio technology is able to provide for
robust communication links at 600 kb/s netto data rate without packet loss:
▸ from each cavity to every other cavity, if the doors are closed.
▸ Very likely from each cavity to adjacent cavities with open doors.
Imec’s current 802.15.4a-compliant UWB radio technology is not able to provide
for robust communication links from each cavity to every other cavity at 600 kb/s
netto data rate without packet loss, if all doors are open and the cavity distance
(hops) is larger than 1.
© IMEC 2011
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CHANNEL MEASUREMENT RESULTS
The satellite’s radio channel is a high reflective/multipath-rich environment in which radio signal
are able to propagate from one cavity to the next.
The large scale path loss of the channel for a frequency range of 3-10 GHz varies between 25dB (intra-cavity) to-58dB (cavity 1 to cavity 6) with closed doors.
The RMS delay spread varies between 40.7 ns (intra-cavity) and 118.6 ns (cavity 1 to cavity 6).
The small-scale-fading for narrowband systems is Rayleigh distributed even in LOS conditions.
An example of such a narrowband system is 802.15.4. To obtain robust communication links,
some form of diversity will be needed.
UWB systems experience a mean power gain variation of at most 5 dB due to small-scale-fading,
due to its inherent frequency diversity.
The mean power gain of the channel depends mainly on the cavities of TX and RX, i.e. the exact
position of the TX/RX within these cavities has little impact.
Opening of the satellite doors may lead to a decrease of the channel gain in the order of 15-18
dB for intra cavity channel and 10-13 dBs for inter cavity channels; depending on the
contribution of the door as reflective object to the overall channel transfer function.
© IMEC 2011
RECOMMENDATIONS
EMC
▸Study ESA’s EMC requirement wrt FCC part 15
regulation for intentional radiators
▸EMC center Eindhoven could play a role!
© IMEC 2011
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RECOMMENDATIONS
Centralized network topology
▸Only intra-cavity communication,
▸Inter cavity communication via wired bus system
▸Increased system capacity
▸Beneficial if one of few data-sink can be identified
Ad-hoc network topology
▸Each sensor/tag may communicate to any other
sensor/tag
▸More complicated MAC (assuming no fixed
addressing)
© IMEC 2011
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