Upload
arthur-gibbs
View
219
Download
2
Tags:
Embed Size (px)
Citation preview
Wireless infrared indoor communications: Wireless infrared indoor communications: how to combat the multi-path distortionhow to combat the multi-path distortion
S. Jivkova and M.KavehradS. Jivkova and M.KavehradCenter for Information & Communications Technology Research (CICTR)Center for Information & Communications Technology Research (CICTR)
Department of Electrical EngineeringDepartment of Electrical EngineeringThe Pennsylvania State UniversityThe Pennsylvania State University
Photonic EAST 2000Photonic EAST 2000
OutlineOutline
• Multi-Spot Diffusing Configuration (MSDC): characteristic features
• Multi-path distortion
• Receiver geometrical configuration
• Channel parameters
• Novel receiver optical front-end design
• Conclusions
Photonic East 2000Photonic East 2000
Characteristic features
• One-to-many and many-to-one communications
• Lack of alignment requirement
• Roaming possible
• Can be virtually free from multipath induced temporal distortion
• Relatively large cell size
• Tolerance to shadowing and blockage
Quasi non-directed non-LOS configuration
Element
0
)( )()(k
k thth
T
R
Multipath distortion
Multi-spot diffusing configurationMulti-spot diffusing configuration
At least one diffusing spot lies
within each branch field-of-view
At most one diffusing spot lies within each branch
field-of-view
FOV1 FOV2
Multi-spot diffusing configurationMulti-spot diffusing configuration
FOV1
FOV2
6m
6m
Multi-spot diffusing configurationMulti-spot diffusing configuration
Circle areas on the ceiling covered by the central receiver branch for a receiver position (0.3m, 05m) measured from the room corner
Room size: 6m x 6m x 3mReflectivity of room surfaces: 0.7 (walls and ceiling),
0.3 (floor)Number of reflections considered: 3Transmitter position: center of the room,
0.9m above the floor
time [ns]
0 20 40 60 80
impu
lse
resp
onse
[s-1
]
0
1
2
3
300
400
500
three bounces
0 20 40 600123
0 20 40 600123
0 20 40 600
200
400
6001st bounce (88.8%)
2nd bounce (1.7%)
3rd bounce (9.5%)
frequency [MHz]
0 50 100 150 200 250
mag
nitu
de r
espo
nse
[dB
]
-144
-142
-140
-138
one bounce (f3dB=236.6MHz)
two bounces (f3dB=232MHz)
three bounces (f3dB=191MHz)
FOV1 (two diffusing spots within receiver branch FOV)
time [ns]
0 20 40 60 80
impu
lse
resp
onse
[s-1
]
0
1
2
3
300
400
500
three bounces
0 20 40 600123
0 20 40 600123
0 20 40 600
200
400
6001st bounce (92%)
2nd bounce (0%)
3rd bounce (8%)
frequency [MHz]
0 50 100 150 200 250m
agni
tude
res
pons
e [d
B]
-148
-146
-144one bounce (f3dB=2.82GHz)
three bounces (f3dB=2.47GHz)
FOV2 (one diffusing spot within receiver branch FOV)
Multi-spot diffusing configuration:Multi-spot diffusing configuration:Channel characteristics
Field-of-view of a 7-branch
composite receiver
r
1H2
ΔS)FOVtan(
r22 H
ΔDΔS)tan(FOV)tan(3FOV
Number of spots covered by each branch:
- At least one:
- At most one:
S
2ΔS/
D
FOV2
FOV1
ΔD-ΔS
central side
central
Multi-spot diffusing configurationMulti-spot diffusing configuration
Multi-spot diffusing configurationMulti-spot diffusing configurationReceiver optical subsystem
Major factors in receiver optical subsystem design:Major factors in receiver optical subsystem design:
• Signal gain
• Ambient light rejection
• Physical weight, size and cost
wave 1,
wave 2,
hologram
two plane waves,plane substrate
(plane holographic mirror)
wave 2,
wave 1,
hologram
two spherical waves,curved substrate
(spherical holographic mirror)
two spherical waves,plane substrate
(spherical holographic mirror)
wave 2,
wave 1,
hologram
Recording of Reflection Holograms
Multi-spot diffusing configurationMulti-spot diffusing configurationReceiver optical subsystem
Holographic curved mirror as a receiver optical front-end
Multi-spot diffusing configurationMulti-spot diffusing configurationReceiver optical subsystem
photodetector
holographic curved mirror
2
dielectricfilling
Multi-spot diffusing configurationMulti-spot diffusing configurationReceiver optical subsystem
Angular and spectral selectivity of a reflection hologram
Multi-spot diffusing configurationMulti-spot diffusing configurationReceiver optical subsystem
0.0
0.5
1.0
-10
0
10
20 820830
840850
860
diff
r. e
ffic
ienc
y
angle of incidence
[deg]
wavelength [nm]
=0, =, =850nm, n=1.5, n=0.01, d=60m
angle of incidence [deg]
-15 -10 -5 0 5 10 15
diff
ract
ion
effi
cien
cy
0.0
0.2
0.4
0.6
0.8
1.0
844nm
846nm
848nm
850nm
angle of incidence [deg]
0 2 4 6 8 10 12 14
effective area
[cm
2 ]
0
2
4
6
8
=3mm=4mm=5mm
angle of incidence [deg]
0 2 4 6 8
effective area
[cm
2 ]
0
2
4
6
8=1mm=2mm=3mm=4mm=5mm
angle of incidence [deg]
0 2 4 6 8 10 12 14
effective area
[cm
2 ]
0
2
4
6
8
=3mm=4mm=5mm
angle of incidence [deg]
0 2 4 6 8
effective area
[cm
2 ]
0
2
4
6
8
=1mm=2mm=3mm=4mm=5mm
HSM
HPM
Multi-spot diffusing configurationMulti-spot diffusing configurationReceiver optical subsystem
angle of incidence [deg]
0 2 4 6 8 10 12 14
figu
re of merit gain [dB]
-10
-5
0
5
10
15
20
=3mm=4mm=5mm
angle of incidence [deg]
0 2 4 6 8
figu
re of merit gain [d
B]
-10
-5
0
5
10
15
20
25
=1mm=2mm=3mm=4mm=5mm
angle of incidence [deg]
0 2 4 6 8 10 12 14
figu
re of merit ga
in [dB
]
-10
-5
0
5
10
15
20
=3mm=4mm=5mm
angle of incidence [deg]
0 2 4 6 8
figu
re of merit gain [dB]
-10
-5
0
5
10
15
20
25
=1mm=2mm=3mm=4mm=5mm
HSM
HPM
Multi-spot diffusing configurationMulti-spot diffusing configurationReceiver optical subsystem
Diffuse configuration:Diffuse configuration:Channel characteristics
time [ns]
0 20 40 60 80
impu
lse
resp
onse
[s-1
]
0
20
40
60
80
100
120
1st bounce (53.7%)
2nd bounce (26.5%)
3rd bounce (19.8%)
frequency [MHz]
0 50 100 150 200 250
mag
nitu
de r
espo
nse
[dB
]
-145
-140
-135
-130
-125
-120
one bounce (f3dB=49.9MHz)
two bounces (f3dB=35.5MHz)
three bounces (f3dB=19.2MHz)
time [ns]
0 20 40 60 80
impu
lse
resp
onse
[s-1
]
0
2
41st bounce (45.7%)
2nd bounce (25.6%)
3rd bounce (28.7%)
frequency [MHz]
0 50 100 150 200 250
mag
nitu
de r
espo
nse
[dB
]
-175
-170
-165
-160
-155
-150
one bounce (f3dB=188MHz)
two bounces (f3dB=91MHz)three bounces (f3dB=23MHz)
FOV=70deg
FOV=10deg
Diffuse configuration:Diffuse configuration:Channel characteristics
emitter to receiver distance [m]
0 1 2 3 4 5
3dB
ban
dwid
th [
MH
z]
1
10
100
100010deg 30deg 50deg 70deg 90deg
Room size: 8m x 8m x 4mReflectivity of room surfaces: 0.7Number of reflections considered: 5Transmitter position: center of the room, 1m above the floor
Lomba, Valadas and Duarte, 6th IEEE Intl. Symp. On Personal, Indoor and Mobile Radio Communications, Sept. 27-29, 1995, Toronto, Canada, Proc., pp.321-325
Comparison between Pure-Diffuse and Multi-Spot Diffuse (MIMO) in terms of 3-dB Optical Channel Bandwidth for a Sample Receiver Position 3.7m away
from Transmitter
3-dB BandwidthArchitecture Type Field-of-View
Diffuse
Multi-Spot-Diffuse
70 deg
10 deg
FOV1
FOV2
19MHz
23MHz
190MHz
2.4GHz
Photonic East 2000Photonic East 2000
Conclusions
• Major factors causing channel distortion- Higher order reflections- Number of diffusing spots- Diffusing spot size
• Virtually ideal channel: conditions- FOV1 (3dB < 200MHz)- FOV2 (3dB > 2GHz)
• Holographic curved mirror as a receiver optical front-end- Multi-functionality- Insignificant physical weight
Photonic East 2000Photonic East 2000