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Key System Technologies for future satellite mobile systems
R A Pearson and M W Shelley, ERA Technology Ltd
2 Antenna and Electronic Systems
Presentation Overview
Evolution of Ka-band satellite systems for mobile comms
Advantages / disadvantages of these systems
Key antenna technology issues
ERA work in Ka-band for mobile applications
S-band satellite systems
Overview of new S-band systems and applications
Ancillary Terrestrial Component
Use of an Ad-hoc Terrestrial Component for disaster recovery, security & humanitarian applications
ERA demonstration programme
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Why Ka-Band?
Greater available spectrum
Smaller terminal equipment
Less inter-satellite interference
In the mobile environment, simpler antenna technology due to the use of circular polarisation
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Why not?
Higher cost of equipment
Fewer high power satellites
Greater link losses
Wide frequency separation between TX and RX, creating significant antenna challenges for mobile systems
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Ka-Band satellite segment
50 Ka-band satellites in orbit, 34 are active.
Most use old-fashioned “bent-pipe” technology
New satellites are being designed and built using on-board processing (e.g., multi-beam antennas with flexible antenna pointing systems)
frequency re-use
increased capacity
reduced transponder costs
Eutelsat Ka-Sat
multi-spot satellite providing good QoS at an affordable price
80 spot-beams, offering capacity equivalent to 10 Ku-band satellites
charges reduced by factor of eight compared to Ku-Band
Launch scheduled for 2010
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Ka-Band satellite segment
Avanti Communications Hylas
two-way data communications for:
Resilient, ultra-high speed corporate networks
Two-way broadband access services
IPTV platform distribution
Ka-band Interactive TV return channel
HylasOne launch scheduled for 2009
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Target markets
emergency services (e.g., humanitarian disaster relief)
homeland security
broadcasting
military communications
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Mobile antenna solutions
Given the widespread need for low profile and small size, this is probably the most critical ground terminal component
Key challenges:
accommodating wide frequency separation in single aperture
achieving hemispherical or near hemispherical coverage
Opportunity for smaller mobile and on-pause broadcast
Air transport, also UAV (civil & military)
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Circular reflector
Advantages
Simple design
Lightweight reflector, allowing high dynamic performance
Simple dual band operation
Full hemispherical coverage possible
Uniform system performance for all locations
But …
Not low profile (typically > 20”)
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Elliptical reflector
Design options
Dual offset for compactness
Single offset for simplicity
Advantages
Lightweight reflector, allowing high dynamic performance
But …
Difficult to control illumination and efficiency
Medium height profile (typically 15-18”)
Scan limitations
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Fixed beam array
Fixed beam array, mechanically steered in two planes
Advantages
Highly adaptable geometry
Excellent control of azimuth illumination
Simple to balance for high dynamics
Full hemispherical coverage possible
Low profile (6-10”) – radome dependent
But …
Complex feed structure
Difficult to configure for Ka-Band TX and RX
ERA Ku-band system
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Cylindrical reflector
Offset reflector with azimuth array feed
Advantages
Highly compact geometry
Very high efficiency
Excellent control of azimuth illumination & sidelobes
Simple to balance for high dynamics
Full hemispherical coverage possible
But …
Complex array feed
Low/medium height profile (10-12”)
ERA Ku-band proof of concept aperture
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Hybrid flat plate arrays
Cobham Ku-band “G2” dual aperture hybrid array: 3” height
Azimuth rotation; elevation scan without change of profile
Advantages
Generally good control of
azimuth illumination
Ultra-low profile 3” / multi-panel 6-8”
Single band designs
But …Variable elevation pattern
Limited instantaneous
bandwidths (frequency scan)
Coverage limited close to
horizon (typically > 20°)
Complex mechanical actuation
Poor elevation radiation patterns for multi-panel
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Phased arrays
Electronic scan in two planes “holy grail”
Advantages
Excellent radiation patterns
Solid state design
high dynamics/multibeam
Ultra-low profile
But …
Two aperture required for RX/TX operation; wideband studies
Order of magnitude more expensive than other solutions
Coverage limited towards horizon (> 20° above horizon)
Complex RF electronics and control circuitry
ERA proof-of-concept Ka-band phased array tile (+/-70°, 40% bandwidth)
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Antenna developments needed
Launch Products:
Low profile reflector systems
Future:
Hybrid antennas using single electronic scan
Dual band apertures with full electronic scan
ERA development of Ka-band demonstrator for use with Hylasstarted April 2008
Based on cylindrical reflector
Modular upgrade to Ku-band Spitfire system
Further R&D needed to advance the Ka-band tile technology
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The case for S-band
Other bands:
L-band systems provide modest data rates (<500Kbit/s)
Require high gain antennas to realise higher data rates
Iridium: global coverage, but modest data rates
Ku-band systems: Mbit/s data rates but large antenna terminals
Ka-band system: Mbit/s data rates, similar terminals (rain fade)
A new generation of S-band satellite systems being developed:
Video and multimedia services – mainstream market
Emergency service use – niche market
Handheld / very small terminals:
Video and interactive services
Adjacent band to terrestrial mobile systems – dual mode handsets
Auxiliary Terrestrial Component (ATC) proposed for urban areas
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Ancillary Terrestrial Component (ATC)
Urban areas: good terrestrial coverage – fixed sites link to satellite and link to mobile via terrestrial infrastructure; notyet developed – business case (will it fly?)
Rural areas: limited coverage – direct link to satellites
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Competitor Service Providers
Inmarsat Global Ltd; established player – ATC authorisation from FCC
Iridium; Next - improved data rates – ATC authority from FCC
Globalstar – next generation – ATC authority from FCC
Terrestar/TMI
Plans for 4G (satellite and terrestrial)
Terrestar-1; spots -CONUS, Canada, Alaska, Hawaii, Puerto Rico
ATC for urban canyons, dense forests, areas where will be blocked
Mobile Satellite Ventures; ATC authorisation
MSAT-1 & MSAT-2 aim to deliver mobile wireless voice & data
Public safety, security, fleet & asset tracking in U.S. & Canada
ICO Global Communications
Created in 1990’s out of a programme called Project 21
MEO 1st satellite (UK entity) – ground infrastructure, 10 satellite in storage
First GEO (US entity); launched in April 2008
Eutelsat/SES
Supported by ARTES
W2A satellite in 2009
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ICO S-band: CONUS and MEO
GEO; launched 14th April MEO; initial satellite in orbit
Future constellation illustrated
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Mobile Services
Example services (ICO)
ERA was involved in Ku-band TV to car – large antennas required
New S-band service only requires low gain terminal antennas
$15-25 per month subscription
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Ad-hoc Terrestrial Component (Ad-TC)
Could be made compatible with ATC but will function independently
Why is this important?
ATC may not develop
May not be available in a given region
Infrastructure may be intentionally blocked or jammed
May not be unavailable following a natural disaster / terrorist incidence
Ad-hoc network will:
Extend coverage in urban areas, even into collapsed buildings and underground train systems
Can be used independent of satellite if the link cannot be formed
Will enable multiple groups to be networked together or backhauled to a remote operations centre
Will enable talk-through multiple radio and satellite hops
Provide data transfer via an IPv6 overlay
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Emergency & Disaster Recovery
Essential voice and data communications
Fire Rescue
Chemical and Biological Hazards
Collapsed sites
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Disaster Life Cycle Management
Stage 1: Immediate: Rapidly deployable, highly portable, small,lightweight equipment
Ease of use – non technical users
Voice & data – voice & SMS contact with HQ
Internet & VPN – initial access to emergency management application
Stage 2: 48 hours: Networked communications with a high level ofinteroperability
Voice & data – on-going coordination
Internet & VPN – increasing activity via emergency management – higher data
Stage 3: beyond 48 hours: Longer term installations
Voice & data – on-going coordination
Internet & VPN – heavy traffic via emergency management systems
Technical operators
Humanitarian life cycles are typically much longer, but “disaster” area can be huge (size of a country)
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How does an ad-hoc network work?
Radios talk with each other via other radios in the group
No master radio – dynamically finds radio at “centre” of mesh
Range rapidly reduces in urban or disaster conditions:
Inside buildings/collapsed structures, underground, inside-to-outside communications
Satellite link will generally fail under such circumstances
Combined satellite/terrestrial provides local & reach-back communications
Not infrastructure dependent
User A User B
2.4GHz Ad-hoc Mesh Network
Node 1
Node 3
Node 5
Node ANode
B
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Self-adaptingmesh network
Self-healing
Mesh network nodesoffer potential to extend range
ERA Ad-hoc Mesh Radio
Emergency Scenarios:- Collapsed buildings
- Mines / Caves / Metro- Fires and chemical hazards
- Outdoor-to-indoor connectivity
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Initial Ad-hoc Mesh Trials
Initial ERA radio trials at 2.4GHz undertaken in US using mesh network radio
ERA trials in Centre for National Response – network of mines
Indicate terrestrial coverage maintained inside-to-outside
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Vision: Ad-TC with satellite connectivity
Separate ad-hoc groups can communicate:
Terrestrially with each other within local ad-hoc mesh
Terrestrially mesh-to-mesh when in range
Via satellite between ad-hoc mesh groups
Via satellite to control centre/web – single link possible
No dependence on ANY terrestrial infrastructure
Satellite Gateway:
voice or data to control
centre or web access
One or more radios in mesh is satellite enabled/ linked to satellite
modem
voice & data enabled handheld IPv6 radios
Ad-hoc mesh 1
Terrestrial link up to
~1kmIn-building comms
Ad-hoc mesh 2
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Conclusions
S-band offers:
Mainstream multimedia services, e.g. to cars – removes need for large Ku-band antennas
Convergence between terrestrial and satellite communications
Emergency and Disaster Recovery use – EU allocated spectrum
Question marks about the commercial viability of ATC
Large infrastructure investment - sense of deja-vu
Satellite with Ad-hoc Terrestrial Component (AdTC):
Provide seamless connectivity for emergency services, NGOs, Govt users; local & global
Fulfils niche disaster recovery applications
Interoperable with ATC, but not dependent on it
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Future Work
Further development of mesh network technology is required to demonstrate:
Dual mode terrestrial-satellite connectivity
Voice and data
In-building/outdoor connectivity
Enhanced network connectivity and scenario specific operation
Benefits of mesh network nodes
IPv6 will be critical as an overlay for such networks
ERA started a project April 2008 to adapt its military ad-hoc radio technology, add IPv6 & develop functionality for disaster management application & link to satellite system
Aiming to demonstrate with S-band satellite as part of a hybrid terrestrial / satellite network for humanitarian application in 2009
Have interest for trial by humanitarian charity
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