Transcript Free Space Optical (FSO) Communications in Next Generation
Survey of Free Space Optical
(FSO)
Communications Opportunities in Next Generation Cellular Networks Frédéric Demers, Halim Yanikomeroglu & Marc St-Hilaire Presented at the Communication Networks and Services Research Conference 4 May 2011
Outline
Motivation & Key Characteristics of FSO systems Channel model and path loss overview Recent advances in FSO communications Full Optical FSO systems Hybrid RF/FSO systems Mobile FSO systems Indoor diffuse FSO systems Applications within Next Generation Cellular Networks Conclusions 2
Motivation & key characteristics
RF spectrum scarcity vs increasing throughput requirements A single FSO channel can offers Tb/s throughput wirelessly Free space optical spectrum is license free and nearly unlimited (very dense reuse) FSO systems are generally very difficult to intercept Effective range limited by weather and eye safety considerations 3
Channel model
Factors affecting light propagation through the atmosphere Physical composition of atmosphere Changes in refractive indices
Aerosol particles
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Channel model
850 nm 1550 nm
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Channel model
Channel effects: Absorption Diffraction Rayleigh scattering (atmospheric gases molecules) Mie scattering (aerosol particles) Atmospheric (refractive) turbulence: Scintillation Beam wander
Weather
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Channel model
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Path loss, RF
Typical RF attenuation (e.g. 2 GHz, 15 dBi antenna gains) Avg path loss in free space -> 68 dB @ 1km , 118 dB @ 10 km Avg path loss in mobile radio (n=3.4, d 0 =100 m) -> 82 dB/km, 146 dB @ 10 km
PL
mobile-radio 4
d
0 2
d d
n
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Path loss, FSO
Intensity of light at point
x
and time
t’ I
I
e
0
x
Beer-Lambert Law Space time distribution of species Intensity of transmitter
a
R
M
Mie Scattering Absorption Raleigh Scattering M. Bass, "Atmospheric optics," in Handbook of Optics ,Third Edition ed., vol. 5, M. Bass, Ed. McGraw-Hill, pp. 3.3., 2010.
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n
0
Path loss, FSO
Pressure
p
Temperature 2 3 7733
q T
10 6 Refractive index of air Humidity
n T
n
0
n
Point in space Stochastic component 10
Path loss, RF vs FSO
Typical RF attenuation (e.g. 2 GHz, 15 dBi antenna gains) Avg path loss in free space ->
68
dB @ 1km ,
118
dB @ 10 km Avg path loss in mobile radio (n=3.4, d 0 =100 m) ->
82
dB @ 10 km dB/km,
146
Typical optical attenuation (e.g. 1550 nm or 194 THz) clear atmospheric conditions ->
0.2
dB/km urban (because of dust) ->
10
dB/km Rain ->
2-35
dB/km Snow ->
10-100
dB/km light fog ->
120
dB/km dense fog ->
300
dB/km maritime fog ->
480
dB/km 11
Full Optical FSO
No requirement for electrical-optical conversion Easy extension of RF-over-fibre links Wavelength division multiplexing K. Kazaura, K. Wakamori, M. Matsumoto, T. Higashino, K. Tsukamoto and S. Komaki, "RoFSO: A universal platform for convergence of fiber and free-space optical communication networks," Communications Magazine, IEEE, vol. 48, pp. 130-137, 2010.
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Hybrid RF/FSO
FSO is most affected by fog, RF by rain RF links complements FSO to achieve carrier class availability (99.999%) Lower throughput in adverse weather I. I. Kim and E. Korevaar, "Availability of free space optics (FSO) and hybrid FSO/RF systems," Optical Wireless Communications IV, EJ Korevaar, Eds. , Proc. SPIE, vol. 4530, pp. 84-95, 2001.
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Mobile FSO Systems
Tightly packed LED transceivers around spherical device Able to maintain optical link in motion Experiment rather simplistic J. Akella, C. Liu, D. Partyka, M. Yuksel, S. Kalyanaraman and P. Dutta, "Building blocks for mobile free-space-optical networks," in Wireless and Optical Communications Networks, 2005. WOCN 2005. Second IFIP International Conference on, pp. 164-168, 2005.
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Indoor Diffuse Optical Wireless
Non Line-of-Sight optical communications Multipath interference an issue, limiting throughput Hybrid narrow-beam designs provide both bandwidth and coverage R. J. Green, H. Joshi, M. D. Higgins and M. S. Leeson, "Recent developments in indoor optical wireless systems," IET Communications, vol. 2, pp. 3, 2008 15
Next Generation Cellular Networks
Densification of access points (eNodeB) Shorter hops Suitability to mesh connectivity Heterogeneous access points Relaying Distributed antennas Coordinated Multi-Point Transmission & Reception (CoMP) Self-Organizing Networks
Next Generation Cellular Networks
Evolved UMTS Terrestrial Access Network (E-UTRAN) Evolved Packet Core aGW UE p-eNB p-eNB eNB MME SAE GW aGW relay relay eNB UE Indoor AP PDN GW
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Conclusions
Radio frequencies alone will not suffice to provide the required throughput to the end-users PHY layer is not dead!
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Main references
2.
3.
1.
4.
5.
J. Akella, C. Liu, D. Partyka, M. Yuksel, S. Kalyanaraman and P. Dutta, "Building blocks for mobile free-space-optical networks," in Wireless and Optical Communications Networks, 2005. WOCN 2005. Second IFIP International Conference on, 2005, pp. 164-168. Available: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.143.6352&rep=rep1&type=pdf M. Bass, "Atmospheric optics," in Handbook of Optics ,Third Edition ed., vol. 5, M. Bass, Ed. McGraw-Hill, 2010, pp. 3.3.
R. J. Green, H. Joshi, M. D. Higgins and M. S. Leeson, "Recent developments in indoor optical wireless systems," IET Communications, vol. 2, pp. 3, 2008. Available: http://www.ieeexplore.ieee.org.proxy.library.carleton.ca/stamp/stamp.jsp?tp=&arnumber=4446 618 K. Kazaura, K. Wakamori, M. Matsumoto, T. Higashino, K. Tsukamoto and S. Komaki, "RoFSO: A universal platform for convergence of fiber and free-space optical communication networks," Communications Magazine, IEEE, vol. 48, pp. 130-137, 2010. Available: http://www.ieeexplore.ieee.org.proxy.library.carleton.ca/stamp/stamp.jsp?tp=&arnumber=5402 676 I. I. Kim and E. Korevaar, "Availability of free space optics (FSO) and hybrid FSO/RF systems," Optical Wireless Communications IV, EJ Korevaar, Eds. , Proc. SPIE, vol. 4530, pp. 84-95, 2001. Available: http://www.ece.mcmaster.ca/~hranilovic/woc/resources/local/spie2001b.pdf
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