High Availability Free Space Optical (FSO) and MM … Availabilty FSO.pdfHigh Availability Free...
Transcript of High Availability Free Space Optical (FSO) and MM … Availabilty FSO.pdfHigh Availability Free...
High Availability Free Space Optical (FSO) and MM-Wave Hybrid Wireless Networks;
Concept, Architecture, Experimental Verifications and Path Forward
MSU - OCT 3rd, 2005
Hoss IzadpanahCollege of Optics and Photonics
UCF – Orlando [email protected]
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Terrestrial Fiber and MM-Waves Wireless Networks Physical Layer Architecture
Terrestrial Fiber NetworksCore communications network through DWDM led to massively increased transmission capacityTerabit, many 1000’s miles with mw power and extreme highest network capacity and lowest transmission BERBackbone, metro, LAN and access to include 40 Gbps research networksBut less than 10% high bandwidth users have access to fiber: Last mile bottleneckCostly and lengthy new fiber wiring
RF and Mm-waves WirelessNew mm-wave bands opportunitiesSpectra limitations & license requirementsP-t-P & P-t-MP up to lower Gbps rates Relative costly & complex technologyPower consumptionLimited “Networked” potentialChannel isolation, xtalk, etc.
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FSO Wireless Technology Its Role In Terrestrial and Space Communications Networks
LaserComIn 60’s and 70’s made its mark on inter-satellite, satellite-ground and satellite-submarine Now is becoming a feature of urban terrestrial communications technologyMany commercial operating units for short distance (100’s meters to few km)
Backbone and interconnectionsLast mile, campus intranet, small communities, airports, etc.
Under fast development/deployment stages, at Gbps data rates:Airborne- (inter-, to and from) ground high speed and high capacityMOBILE links and SPACE GRIDHigh speed inter-planetary Internet connections
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Airborne Gbit Communications GridHigh Compatibility for FSO Link Requirements
Satellite and Airborne FSO LinksLow weight, low complexity and low power
• No nonlinear Up/Down converters, no power hungry DAC or ADC or ADCHigh capacity and high date rates
• Doubled spectral efficiency with dual polarization practiced in FSO and RF system today
WAN
MMW
WAN WAN
RF RFRF
MMWMMW
FSO
FSO FSO
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Free Space Optical (FSO) Wireless All Weather Hybrid Optical/MM-Wave Wireless Network Architecture
LaserCom
Hybrid Fail/Safe Rings
ANAN
AlternateProtection SW
Mm-Wave
LaserComAN
Optical and RFWireless Bridge
BackboneWDM
Fiber Network
AN
AN mm-WaveWireless
Access andDistribution
Network
AN
BackboneFiber Network
SW/GW
PCS, MMDS, LMDS Reach Extension
SW/GW
BackboneFiber Network
RegionalNetwork
• PtP links•All-Weather• Rapidly deployable• Gbit capacity• Flexible traffic routing• “SECURE” Channels
SW SW
RF
FSOW
GW GW
Geophysical Diversity“Single Band”
Wireless Access Network& Distribution Topology
MMDS, LMDS, etc.
BuildingDistribution
NeighborhoodDistribution
BackboneFiber Network
LaserCom
LaserCom
SW/GW
• Fiber access to buildings ~ < 5%• FSO feed To remote Pico-cells• Gbit service delivery to remote RF
“Multi-Band”
• Multi-band, multi-service RF remoting
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Broadband Hybrid MMW/FSO Wireless Access and Distribution SystemFunctional Network Segmentation and Topology
Sub network islands of transparency for all optical managed networksSingle RF platform, modular IF stages on HFR and FSOW towards passive AP connectivityA converged and Integrate the wire and wireless infrastructure for an Internet multi-service networkLeave the RF signal where it belongs (to radiate) and relax network operational complexity
Local
Satellite Downlink
NetworkOperation
Center (NOC)
Processing/Switchingand Service Integration
NGIMAN/WAN
Global Network
NGIMAN/WAN
AP
Hybrid mm-wave & Free-Space Optical
Wireless
AP
< 500 m
Access Point and Distribution
Multi-tenant high bandidth users
OW & Hybrid Fiber Radio
AP
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FSO Bandwidth, Capacity and Link Availability
Fiber optics extremely large amount of bandwidth over continental distances not been matched in FSOFSO links present unpredictable channel impairments (attenuation, delay and aberrations)- over times as short as msecDemonstrations of 160 GHz DWDM link BUT commercial FSO links are limited to a few GHz over distances of a few tens of kmMoving beyond these limitations requires
Agility in transmission power, modulation format and rates as well as laser emission wavelength
AtmosphericTurbulenceEffect Close
To Buildings
Like a Phase Mask
LOS
Scattered
Pointing Error
*** Spatial, angular and temporal spread of signal
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High Availability FSO/MM-Wave Combined LinksDesign challenges and potential solutions
Real-time link performance characterization and adaptation for enhanced performance during adverse weather
Dynamic transmitter power control• Large FSO link margin combats many scintillation/turbulence fades• Dynamic FEC & Control
Modulation and data rate control • Format at 64 QAM to 32, …,QPSK & BPSK• Rate reduction from high say OC-48 to 12, or even OC-3)
Hybrid FSO/RF Wireless Network for High AvailabilityRF layer to increase link availability in times of several cloud blockagePath diversity, dynamic load switching and multi-hop routing (mesh network) to maintain the link/network availability and connectivity
Proactive SchemesIdentify & initiate, in a real time, restoration of the FSO link
Channel ConditioningAdaptive and Multiple Antennas, Alignment and Trakting
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RF photonic based signal generation, modulation and transport• delivery in the 30-140 GHz spectral region
Combined RF/MMW and FSO diversity solution for DLS and traffic portioning
Millimeter Wave & Optical SpectrumGbit RF/MMW and FSO Hybrid Link
10GHz
100GHz
1THz
10THz
100THz
1000THz
94 GHz *
140 GHz *
220 GHz *
CurrentFrequency RangeMillimeter Wave
Radios
50 GHz x160 Channels
Newly Opened Frequencies
* In Development
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Multi-hop Routing Approach to Enhanced the Link Availability
Objective:To improve FSO link and network availability within the system power budget (excessive attenuation)
Trade-offs:Path Availability: favors short links (=> more hops)Path Delay: favors long links (=> less hops)
Problem Statement:Determine the route from source-to-destination that strikes a balance between availability and delay depending on the source-to-destination distance, traffic type and QoS constraints.
Link Metric:The link atmospheric attenuation should be incorporated along with the classical link delay and link load criteria.
AvailabilityRouting Algorithm
for a Mesh Topology
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Comparing ArchitecturesCourtesy: Carlton O’Neal – Ensemble Comm
Mesh-Point to Pointn Base stations with shared bandwidth
over large area (> 75 sq kms)
n One antenna per customer
n Rapid, planned coverage of an area
n Good for carrier class ntwk/growth
Point to Multipointn Series of radios units connecting
individual buildings (served or not)n Multiple antenna placementsn “Biological” network deployment
using planning/operations softwaren Good for cheap/fast connectivity
Sou
rce:
Rad
iant
Net
wor
ks
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1.E-11
1.E-07
1.E-03
1.E+01
12:00 16:00 20:00 0:00 4:00 8:00 12:00Time (hrs)
Inst
. BER
BER 1BER 10
FSOW at OC-12August 18 and 19, 2001Cascaded Link Length - 940m
1.E-11
1.E-08
1.E-05
1.E-02
12:00 16:00 20:00 0:00 4:00 8:00 12:00
Inst
. BER
BER 1BER 10
FSOW at OC-3August 13 and 14, 2001Cascaded Link Length - 940m
Signal Formats:
Double Pass Repeated 1000 meter FSO LinkCharacterization and Performance Evaluation
Digital Baseband, QPSK and 16Qam SCM on 140 MHz
Channel Rates:
80, 120, 155, 240, and
622 (OC-12) Mbps
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Dynamic Load Switching (DLS)Enhances the Link Availability and Maximizes the Capacity
At t=0: RFSOW = RRMMW = 0
Compute the actual atmospheric attenuation for each link averaged over window of Length W
Compute the permissible atmospheric attenuation for each link
Decide the FSOW and MMW link states
Switch load to enhance link availability
Objective:To detect the dynamic status (Available/outage) of FSO links in order to activate necessary procedures for link restoration (if necessary)
Problem:High rate of change of the measured BER causes
• Intermittent short periods (< pre-specified threshold) of link outage • Unnecessary activation of expensive availability enhancement
algorithms (e.g. DLS)Solution:
Sliding Window averaging to filter out frequent oscillations in the BER data.• Window shape: rectangular.• Window length (W): depends on rate of weather changes and
BER/RSSI models
Demonstrated availability figure better than 99.998%
Four possible cases are considered:Both links are availableFSOW failure and RF availableRF failure and FSOW availableBoth links fail
Attenuation threshold settingsBER/RSSIChannel bit rateDLS algorithm
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Instantaneous Link Availability vs. Window Lengths
Impacts of Different Window LengthsShort (W=1, 5? min): high rate BER changesLarge (W= 100 min): info loss, inaccurate availability figure, and unpractical outageIntermediate (10, 20): provides balance between filtering, data loss and availability
Measured FSOW BER at OC-3 Rate
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Real Time Proactive “Availability/Outage” Link CharacterizationDemonstrated Automated Performance Monitoring
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Measured Hybrid Accumulated PerformanceHeavy Fog Day’s Samples
• Hybrid architecture provides higly reliable broadband wireless connectivity during adverse weather events
10 /25 /01 P e rfo rm a n c e o f U n p ro te c te d a n d P ro te c te d IR L in k s
1 .E -12
1 .E -10
1 .E -08
1 .E -06
1 .E -04
1 .E -02
1.E + 00
1.E + 02
1.E + 04
12 :00 14:00 16:00 18 :00 20 :00 22 :00 0:00 2 :00 4 :00 6:00 8:00 10 :00 12 :00T im e (h rs)
Inst
. BER
W e a t h e r D a t a ( 7 6 1 ) f o r 1 0 / 2 5 / 0 1
5 0
5 5
6 0
6 5
7 0
7 5
8 0
1 2 : 0 0 1 4 : 0 0 1 6 : 0 0 1 8 : 0 0 2 0 : 0 0 2 2 : 0 0 0 : 0 0 2 : 0 0 4 : 0 0 6 : 0 0 8 : 0 0 1 0 : 0 0 1 2 : 0 0T im e
Tem
pera
ture
, F
8 4
8 6
8 8
9 0
9 2
9 4
9 6
9 8
1 0 0
Hum
idity
,%
H i T e m pD e w P t
H u m id it y
Protected
SW Events
Unprotected
• Accomplished 306 Hrs of SW’d link availability figure better than 99.998%
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CONCLUSIONTransparent RF/Optical Network Interface Technology
Hybrid FSO/MM-wave architecture and technology enabling to complement and extend the capabilities of the terrestrial fiber grid for air and space communication networksReactive and proactive dynamic link and network level protection to maintain connectivity with high availability
“Dynamic” link performance managements and data rate control“Real time” network topologies, connectivity, and redundancy managements
• Leveraged dynamic load switching and traffic portioning to overcome traditional free-space optical communications pitfalls
• Multi-hop routingFurther research direction
In the system physical interconnected layers, no RF/Optical data FORMAT transformation/conversion should be required as otherwise is practiced today by the present RF wireless cumbersome modulation schemes