vsat-gps1
DESCRIPTION
vsat noteTRANSCRIPT
Introduction
Global Navigation Satellite Systems (GNSS) characteristics
• 20 - 30 satellites constellation• 20 - 30 satellites constellation
• Medium Earth Orbit (MEO) approx. altitude 20,000 km
• Inclined orbital planes > 50°
• Provide autonomous geo-spatial positioning with global coverage
• Accuracy 10 m or better
September 2013 2
GNSS
• Global operational in 2013:
GPS (United States of America)
GLONASS (Russian Federation)
• Regional operational, expanding to be global in 2020:
BeiDou/Compass (China)BeiDou/Compass (China)
• Initial deployment phase, fully operational in 2020:
Galileo (European Union)
• France, India, and Japan are in the process of developing regional navigation systems.
WHAT IS GPS?
• GPS stands for global position satellite• worldwide radio-navigation system formed from a
constellation of 30 satellites up to now.• The GPS was developed as a US military navigation
system but now open to the public uses.
September 2013 4
September 2013 5
• There are four satellites in each of 6 orbital planes.
• Each plane is inclined 55 degrees relative to the equator, which means that satellites cross the equator tilted at a 55 degree angle. angle.
• The system is designed to maintain full operational capability even if two of the 24 satellites fail.
September 2013 6
September 2013 7
CONTROL SEGMENT
• The U.S. Department of Defense maintains a master control station at Falcon Air Force Base in Colorado Springs
• There are four other monitor stations • There are four other monitor stations located in Hawaii, Ascension Island, Diego Garcia and Kwajalein
• The stations measure the satellite orbits precisely.
September 2013 8
September 2013 9
GPS Control Segment
SATELLITE SIGNALS
• GPS satellites continuously broadcast satellite position and timing data via radio signals on two frequencies (L1 and L2).
• Two kinds of code are broadcast on the L1 • Two kinds of code are broadcast on the L1 frequency (C/A code and P code)
• C/A (Coarse Acquisition) code is available to civilian GPS users and provides Standard Positioning Service (SPS).
• P code, used for the Precise Positioning Service (PPS) is available only to the military.
September 2013 11
GPS Basic Frequencies
• All signals and time information are coherently derived from the same clock with a frequency of f0 =10.23 MHz.
• Two carrier frequencies:
L1 = 1575.42 MHz (154 x f0) (wavelength 19.05 cm)L1 = 1575.42 MHz (154 x f0) (wavelength 19.05 cm)
Used in civil GPS receivers
L2 = 1227.60 MHz (120 x f0) (wavelength 24.45 cm)
mostly found in military GPS receivers.
• For (uplink), ground stations use S-band signals.
September 2013 13
GPS Basic Signals (3/4)
• NAV data message includes:
– Almanac
Approximate orbit information for all satellites in the constellation.
– Ephemeris– Ephemeris
Predictions of the transmitting satellite’s current position and velocity as determined by the Master Control Station and uploaded to the satellites.
– Satellite clock correction parameters
– Satellite health data
GPS Signals Modulation (2/2)
• Direct Sequence Spread Spectrum (DSSS) is used to limit the interference from other signals and to prevent jamming and spoofing.
• (C/A) code bandwidth = 2.046 MHz• (C/A) code bandwidth = 2.046 MHz
• (P) code bandwidth = 20.46 MHz
• Code Division Multiple Access (CDMA) is utilized for all the GPS signals.
(all of the satellites broadcast their signals upon the same carrier frequencies).
GPS Signals Spectrum
September 2013 17
• The satellites measure the distance between itself to the GPS receiver.
• The position of a GPS receiver is found by trilateration.
September 2013 18
TRILATERATION
September 2013 19
POSITION LOCATION IN GPS
• Four GPS satellite signals are used to compute positions in three dimensions and the time offset in the receiver clock
• Three measurements can be used to • Three measurements can be used to locate a point
September 2013 20
R2 R3
R1
R4
September 2013 21
• Position dimensions are computed by the receiver in Earth-Centered, Earth-Fixed X, Y,Z (ECEF XYZ) coordinates.
September 2013 22
• The measured distance to satellite i is called a pseudorange, PRi
PRi = Ti × c
where where
PRi is the pseudorange
Ti is the time delay between the satellite and the receiver
c is the velocity of EM waves (3 × 108 ms-1)
September 2013 23
• The satellite and the receiver clocks must be synchronized
• If the two clocks are off by only a small fraction, the determined position data may be considerably distorted
• For example, suppose the receiver clock has an offset of 10ms relative to GPS time:offset of 10ms relative to GPS time:
PR = t x c
=
= 3000 km
( )( )183 1031010 −− ×× mss
September 2013 24
The equations which relate pseudorange to time delay are called ranging equations:
( ) ( ) ( ) ( )2
1
2
1
2
1
2
1 cPRUZUYUX zyx τ−=−+−+−
( ) ( ) ( ) ( )2
2
2
2
2
2
2
2 cPRUZUYUX zyx τ−=−+−+−
( ) ( ) ( ) ( )2222cPRUZUYUX τ−=−+−+−( ) ( ) ( ) ( )2
3
2
3
2
3
2
3 cPRUZUYUX zyx τ−=−+−+−
( ) ( ) ( ) ( )2
4
2
4
2
4
2
4 cPRUZUYUX zyx τ−=−+−+−
where τ is the receiver clock error
U is the location of the GPS receiver
c is the velocity of EM waves (3 × 108 ms-1)September 2013 25
GPS ERROR SOURCES
• The GPS system has been designed to be as nearly accurate as possible.
• There are several sources for these errors, the most significant of which are discussed the most significant of which are discussed below:
Atmospheric Conditions
Ephemeris Errors/Clock Drift/Measurement Noise
September 2013 26
HOW TO REDUCE GPS ERROR?
• Differential correction is a method used to reduce the effects of atmospheric error and other sources of GPS positioning error
• Differential GPS (DGPS) Techniques:-• Differential GPS (DGPS) Techniques:-
The idea behind all differential positioning is to correct bias errors at one location with measured bias errors at a known position. A reference receiver, or base station, computes corrections for each satellite signal.
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GPS ACCURACY
• The accuracy depends on:
– Type of equipments used
– Time of observation– Time of observation
– The position of the satellite being used to compute position
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Receiver using C/A code
Without differential correctionAccuracy between
5 – 15 meters
With differential correctionAccuracy between
1 – 5 meters
September 2013 30
• “Carrier-Smoothed code” can be used to increase the accuracy of C/A code
� involves measuring the distance from the receiver to the
satellites by
counting the number of waves thatcounting the number of waves that
carry the C/A code signal
• Accuracy increase to 10 cm to 1 meters
with differential correction.
September 2013 31
GPS APPLICATIONS
�AIRBONE
- Navigation by general aviation and commercial aircraft
�SEA
- Navigation by recreational boaters, commercial fisherman and professional mariners
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� LAND
a) Surveyors
b) Mapping
c) Recreational
d) Automobile
September 2013 33
� LAW ENFORCEMENT
- Support a variety of policing and criminal justice functions
- Enhance the efficiency of the aviation units
- Assist personal operating in ground - Assist personal operating in ground vehicles
September 2013 34
�MILITARY
- Navigation,reconnaissance and missile guidance systems
� AGRICULTURE
- Precision on farming techniques that can help increase profits and protect the environment.
- Precision involves when applying fertilizer and pesticides
September 2013 35
REFERENCE• Pratt, Bostian and Allnutt, Satellite
Communications, John Wiley and Sons, pp. 458-485. 2003.
• http://www.colorado.edu/geography/gcraft/notes/gps/gps_f.htmlnotes/gps/gps_f.html
• http://www.montana.edu/places/gps/understd.html
• http://www.cmtinc.com/gpsbook
September 2013 36
VSAT NETWORKS
September 2013 37
Overview
� Introduction
� Network Architecture, Protocols and Access techniques
38
� VSAT Earth stations (HUB and Remote) Engineering
� Link budget and performances
� Conclusion
September 2013
Introduction
• VSAT : Very Small Aperture Terminal
• A small earth station, usually from 1.2 to 2.4 meters, used for satellite data communications. One form of datacasting.
• In common practice, the VSAT label does not so much establish the size of the dish as it indicates two-way data communication.
39
the size of the dish as it indicates two-way data communication.
• Retail credit card authorizations are a widespread application of VSAT technology.
• Significant increase in the transmit power capabilities of satellites, and move to frequency bands above C Band made the access of the satellite more affordable.
September 2013
Introduction
• The basic structure of a VSAT network consists of a hub station which provides a broadcast facility to all the VSATs in the network…
• The hub station is operated by the service provider.
40
• Each user organization has exclusive access to its own VSAT network.
• Transmitter power : 1 to 2 W
• Antenna diameters:– C-Band 1.8, 2.4, 3.5, and 3.5m
– Ku-Band 1.2, 2.4, 3.5
September 2013
VSAT Network Architecture
• VSATs are connected by radio frequency links via a satellite.
• The overall link from station to station, called hop, consists of an uplink and a downlink.
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• The are three network types of VSAT’s – One-way Implementation
– Split-two-way Implementation
– Two-way Implementation
September 2013
VSAT Network Architecture
� One-way Implementation
� The mode of satellite used in broadcast satellite service (BSS)
� The hub transmits carriers to receive-only VSATs. � The hub transmits carriers to receive-only VSATs.
� This configuration supports broadcasting services from a central site where the hub is located to remote sites where the ROVSATs are installed.
42September 2013
VSAT Network Architecture
� Split-two-way Implementation
� This implementation is used when there is no normal return channel : BSS BSS
� The relatively high capacity of the downlink is not complemented by an uplink capability from the user terminal.
� Internet split IP
43September 2013
VSAT Network Architecture
� Two-way Implementation
� The VSATs can transmit and receive. Such networks support interactive trafficinteractive traffic
� Can be achieved either of two ways:
� Either direct links from VSAT to VSAT via satellite , should link performance meet the requested quality.
� Or by double hop from VSAT to hub and then a second hop using the hub as a relay to the destination VSAT.
44September 2013
Protocols• ISO/OSI seven-layer stack for interconnecting data terminals
• The satellite communications occupies primarily the physical layer where the bits are carried between terminals.
• A VSAT must have terminal controller at each end of the link (network & link layer)
• The network control center typically controls the system and is responsible for the remaining layers. responsible for the remaining layers.
• Error control method in TCP/IP : ACK NAK ARQ
• X.25, X.75 use ARQ
• Frame relay and ATM flag retransmission but continue the flow of information.
• The propagation delay and the induced errors are critical design elements in digital VSAT connections.
45September 2013
Protocols • User 1 and user 2 are
conducting a two-way communications session with each other.
• Each user interacts with their local device at the application layer of the ISO-OSI stack.layer of the ISO-OSI stack.
• The transaction is then routed via the various layers with suitable processing
• By then, the content is ready to be transmitted via the physical layer.
46September 2013
Access Techniques
• The most popular access method is FDMA which allows the use of comparatively low-power VSAT terminals.
• TDMA can also be used, but is not efficient for low-density up-link traffic from VSAT.– Inventory control– Credit verification
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– Credit verification– Reservation requests
• The traffic in VSAT network is mostly data transfer of a bursty nature occurring in random and possibly infrequent intervals.
• The allocation of time slots in the normal TDMA can lead to a low channel occupancy.
• Demand Access Multiple Access (DAMA)
September 2013
Access Techniques
• Channel capacity is assigned in response of the fluctuating demands of the VSATs in the network.
• DAMA can be used in both FDMA and TDMA
• Examples of access technologies: – SCPC (Single Channel Per Carrier)
– TDM/SCPC Return (Time Division Multiplex) – Asymmetrical SCPC
– TDM/TDMA Return (Time Division Multiple Access)
48September 2013
Single Channel Per Carrier
• Each Carrier Pair Dedicated to
a Customer• No Sharing of Bandwidth
between Carriers
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Advantages•Simple•Easy to Troubleshoot •Minimal Equipment Required•Maximum Bandwidth Availability
Disadvantages
•Hard to manage centrally•High Maintenance•Bandwidth Inefficient•Extremely Inflexible
September 2013
TDM/SCPC
A
B
C
D1
1
•Outbound TX from HUB is shared among all remotes.•Each remote has individual carrier to return data (SCPC
• Shared outbound corresponds to the highest data rate direction
• Since shared, actual utilization tends to flatten out…
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A
D
A
B
C
D
1
A
B
C
1
Advantages
• Bandwidth efficient outbound• Flexible• Ability to burst• Dedicated return
Disadvantages• Inefficient return• More complex than SCPC• No reduction in eq. cost.
September 2013
TDM/TDMA Return
A
B
C
DC
D1
1
B
- Outbound and Inbound are shared.- Remotes are shared amongst assigne
return carriers.- Since shared, actual utilization tends
to flatten out for both Outbound andInbound.
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A
D
A
B
C
D
1
A
B1
B
C
D
A
Advantages• Bandwidth efficient• Flexible• Bursting, QoS, VPNs w/ TCP Acceleration, CIR/Burst Dedicatedreturn
• Centralized management
Disadvantages•Complexity
September 2013
Technologies Fit Different Usage ProfilesP
ric
e o
f S
erv
ice
SCPC Dedicated Link
• Single user sites
• Limited # phone lines
• Basic broadband access
• Infrequent use
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Shared DedicatedSemi-Dedicated
Pri
ce
of
Se
rvic
e
Bandwidth Utilization
TDMA
SCPC Asymmetric Cloud
• Infrequent use
• Call centers
• Streaming content
• Real-time video
• Continuous use
September 2013
VSAT Earth Station (HUB and Remote) Engineering
53September 2013
VSAT Network Earth Station
• VSAT station is made of two separate sets of equipment:
– The outdoor unit (ODU): Interface to the satellite
– The indoor unit (IDU) : Interface to the customer’s terminals or LANs
54September 2013
Schematic of a VSAT User Setup
� The outdoor unit is located where it will have a clear line of sight to the satellite and is free from casual blockage.
� Interfacility link (IFL) carries the electronic signal between the ODU and indoor unit (IDU) aswell as power cables for the ODU well as power cables for the ODU and control signals from the IDU.
� IDU : Workstation ( baseband processor units and interface equipments)Modem, mux/demux.
55September 2013
Typical Configuration of a VSAT Earth Station
� LNC receives the RF signal,amplifies, and mixes it down to IF for passing over the IFL to the IDU.
� In the IDU, demodulator extracts the information signal from thecarrier and passes it at basebandprocessor.processor.
� The data terminal equipment thenprovides the application layer forthe user to interact with the information input.
� On the transmit operation, the opposite is performed.
56September 2013
Typical Hub Master Control Station
� The line interface equipment handles the terrestrial ports tothe host computer.
� the control bus via the hubcontrol interface allows all of thetransmit, receive, and switchingfunctions to be carried out.
� The transmit processing andcontrol equipment (PCE)control equipment (PCE)prepares the TDM stream for theoutbound link to the VSATs.
� This stream passes through the IFinterface to the up-convertor thatmixes the IF to RF.
� On the receive side, the antennapasses individual inbound MF-TDMA signal to the LNA foramplification prior to DC, DEM, and so on to the user.
57September 2013
Link Budget and Performances• The minimum allowed carrier to noise (C/N)o for a typical
inbound VSAT is 6dB, with BPSK modulation and half rate FEC encoding, giving a BER of 10-6 (Threshold).
• Varies depending on the modulation and FEC methods used on the link.
• Rain fade on the uplink or rain fade on the downlink can reduce the clear sky (C/N)o
• The entire two way system drops below the performance minimum.
• Failure at Satellite-hub link should be much less likely, otherwise failure will affect the every VSAT in the network.
58September 2013
Link Budget : Preliminary Calculations
• All link budgets require knowledge of the – free space path loss between the earth station and the satellite and
– the noise power in the operation BW
• Noise powers: • Noise powers: – Noise power in transponder 1, Inbound SCPC FDMA Channels
– Noise power in the Hub Station Receiver, Inbound SCPC FDMA Channels
– Noise power in the Transponder 2, Outbound TDM Channels
– Noise power in the VSAT Receivers, Outbound TDM Channels.
59September 2013
Examples: Stabilized VSAT Systems
• Both C- & Ku-Band applications– C-Band Systems from 2.4
meter and larger– Ku-Band systems from 1.0
meter and larger
60September 2013
Maritime VSAT Systems• 3-axis stabilization
• Pointing accuracy less than 0.2°
• Withstands harsh maritime conditions
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maritime conditions– Corrosion
– Shock & Vibration
– High wind load
– Vessel movements
September 2013
Mobile VSAT Systems• Self-contained & mobile
• Always ready for communication
• Full-motion video while moving
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moving
• Wireless connectivity to external voice, video and data sources
September 2013
Rapid-Deploy VSAT Systems• Self-contained
• Includes power & wireless links
• Automatic deployment of
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deployment of antenna
• Acquisition of satellite within 5 min.
September 2013
Conclusion
• The need to make access to the satellite more affordable and the rapid expansion of the satellite communications worldwide brought forward VSAT.
• A significant increase in the transmit power capabilities of satellite and the move to frequency bands above C band lead to the and the move to frequency bands above C band lead to the reduction of the size and cost of earth station antenna.
• VSAT technology now occupies the context of satellite communications in terms of network configuration, services, economics, operational and regulatory aspects.
64September 2013
References
• Pratt Timothy, Bostian C.W. and Allnutt J.E., (2003), Satellite Communications, John Wiley & Sons.
• G. Maral. VSAT Networks. 2nd Edition
65September 2013
Iridium
Satellite
September 2013 66
History
• Iridium communications service was launched on November 1, 1998. The first Iridium call was made by then-Vice President of the United States Al Gore. Motorola provided the technology and Motorola provided the technology and major financial backing.
September 2013 67
History • The 1990s The original Iridium LLC enters bankruptcy in August
1999.
Dec 2000“ Iridium Satellite LLC" acquires Iridium's assets out of bankruptcy. U.S. DoD awards contract.
Mar 2001 Iridium begins offering commercial service for mobile voice; shifts company's strategy to vertical markets.
June 2001 Introduces data and Internet services.June 2001 Introduces data and Internet services.
Feb 2002 Announces successful deployment of in-orbit spares.
June 2003 Introduces short-burst data (SBD) services.
Aug 2003 Announces short messaging services (SMS).
Mar 2004 Launches fax and enhanced messaging services.
June 2004 FCC grants access to 3.1 MHz of additional spectrum.
July 2004 Surpasses 100,000+ subscribers;September 2013 68
History • Sep 2005 Provides critical telecommunications to first
responders in Hurricane Katrina region. Regional traffic increases more than 3000%.
Feb 2006 Launches compact lower-cost satellite data transceiver for supply chain management, field force automation and remote asset tracking. Commences automation and remote asset tracking. Commences engineering studies for future satellite replenishment and replacement plan.
• Nov 2006 Announces 169,000+ subscribers.
Feb 2007 Announces 183,000+ subscribers.
July 2007 Announces 203,000+ subscribers.September 2013 69
Services
All Gateways Support Voice and Data
Services
– Dial-up
– Direct Internet – Direct Internet Access
– Short Message Service
– Short Burst Messaging
– PagingSeptember 2013 70
Global Commercial Usage
Telephony Traffic, November 2003September 2013 71
General Information• The satellites are in a near-polar orbit.
• Using 6 orbital planes with the inclination of 86.4 degrees.
• the altitude of 485 miles (780 km).
• The 66 active satellites plus 6 in-orbit backup satellites fly in formation in six orbital planes, fly in formation in six orbital planes,
• each with 11 satellites equally spaced apart from each other in that orbital plane.
• Orbital period 100 minutes, 28 seconds.
• traveling at a rate of 16,832 miles per hour, and traveling from horizon to horizon across the sky in about ten minutes.
• As a satellite moves out of reach, the call is seamlessly handed over to the next satellite coming into view.
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General Characteristics
• Satellite weight - 700 kg (1500 lb),
• Spot beams - 48 per satellite,
• link margin - 16 decibels (average),
• lifetime - 5-8 years.
Allocated frequencies:Allocated frequencies:
• Direction Frequency
Iridium Phone-Satellite 1616-1626.5MHz
Satellite-Iridium Phone/Pager 1616-1626.5MHz
Satellite-Satellite 23.18-23.38GHz
Satellite- Gateway 19.4-19.6GHz
Gateway-Satellite 29.1-29.3GHzSeptember 2013 73
How it Work
September 2013 74
Battery &
Radiator
Satellite weight…………..700 Kg
Instant. Peak Power…...>4000 W
Avg. Power Load…………620 W
Vehicle Length……………160 in
Vehicle “Wingspan”..........330 in
Iridium Satellite Vehicle (SV)• Three Principal Elements Of SV:
– Payload – Provides All Command, Control and Communications Functions
– Main Mission Antennas (MMAs) – Provide L-Band Telephony Functions
– Bus – Platform For SV Operations, Provides Power, Pointing, Propulsion
Solar Array Panels (2)
Ka-Band Cross-
Link Antenna (4)Ka-Band Feeder
Link Antenna (4)
L-Band
MMA (3)
Payload
Electronics
Vehicle “Wingspan”..........330 in
• Seven Power PC Processors
• Four Gimbaled K-Band Feederlinks
• Four K-Band Crosslinks (2 Fixed & 2
Gimbaled)
• Three L-Band Phased Arrays
• Two 42.5 sq. ft. GaAs Solar Arrays
• One 60A-hr SPV NiH2Battery
• Three-Axis Momentum-Biased Attitude
Control System
• Redundant Orbit Adjust
• Graphite Epoxy Structure
• Active & Passive Thermal Control
• Life time is 5-8 years.Launch Configuration
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Present Constellation Configuration6
6 O
per
ati
on
al
Sa
tell
ites
Plane 1 Plane 2 Plane 3 Plane 4 Plane 5 Plane 6
SV74 SV55 SV50Slot 1 MS-9 5/17/98 SV22 MS-8 3/30/98 SV19 MS-7 2/18/98 SV18 Slot 1
SV72 MS-3 8/21/97 SV28 MS-4 9/27/97 SV56 MS-2 7/9/97
Slot 2 MS-9 5/17/98 SV23 PR-2 9/14/97 SV34 MS-7 2/18/98 SV42 Slot 2
SV75 MS-3 8/21/97 SV29 MS-4 9/27/97 SV52 LM-1 12/8/97
Slot 3 MS-9 5/17/98 SV76 PR-2 9/14/97 SV35 MS-7 2/18/98 SV40 Slot 3
SV70 LM-4 8/19/98 SV31 MS-4 9/27/97 SV53 MS-5 11/9/97
Slot 4 MS-9 5/17/98 SV25 PR-2 9/14/97 SV36 MS-7 2/18/98 SV39 Slot 4
SV62 MS-3 8/21/97 SV30 MS-4 9/27/97 SV84 MS-5 11/9/97
Slot 5 PR-3 4/6/98 SV45 PR-2 9/14/97 SV05 MS-11 11/6/98 SV80 Slot 5
SV63 MS-6 12/20/97 SV32 MS-1 5/5/97 SV10 MS-10 9/8/98
Slot 6 PR-3 4/6/98 SV46 PR-2 9/14/97 SV06 PR-1 6/18/97 SV17 Slot 6
SV64 MS-6 12/20/97 SV33 MS-1 5/5/97 SV54 MS-2 7/9/97
Slot 7 PR-3 4/6/98 SV47 PR-2 9/14/97 SV07 MS-7 2/18/98 SV15 Slot 7
66
Op
era
tio
na
l S
ate
llit
es1
2 S
pa
re S
ate
llit
es
Slot 7 SV47 SV07 SV15 Slot 7
SV65 MS-6 12/20/97 SV57 MS-1 5/5/97 SV12 MS-2 7/9/97
Slot 8 PR-3 4/6/98 SV20 (89) MS-8 3/30/98 SV08 PR-1 6/18/97 SV81 Slot 8 Color Codes:
SV66 LM-5 12/19/98 SV58 MS-1 5/5/97 SV13 MS-10 9/8/98 Delta
Slot 9 PR-3 4/6/98 SV49 MS-8 3/30/98 SV04 PR-1 6/18/97 SV82 Slot 9 Proton
SV67 MS-6 12/20/97 SV59 MS-1 5/5/97 SV83 MS-10 9/8/98 Long March
Slot 10 PR-3 4/6/98 SV26 MS-8 3/30/98 SV37 MS-11 11/6/98 SV41 Slot 10 Eurockot
SV68 MS-3 8/21/97 SV60 MS-4 9/27/97 SV86 MS-5 11/9/97 NOTE: All launch dates
Slot 11 PR-3 4/6/98 SV03 (78) MS-8 3/30/98 SV61 MS-11 11/6/98 SV43 Slot 11 are GMT
LM-4 8/19/98 LM-2 3/25/98 MS-5 11/9/97
Spare1 SV14 (92) SV11 (88) SV90 SV51 SV77 Spare1LM-6 6/11/99 LM-5 12/19/98 IS-1 2/11/02 LM-2 3/25/98 MS-10 9/8/98
Spare2 SV21 (93) SV91 SV97 Spare2LM-6 6/11/99 IS-1 2/11/02 IS-2 6/20/02
Spare3 SV94 Spare3IS-1 2/11/02
Spare4 SV95 Spare4IS-1 2/11/02
Spare5 SV96 Spare5IS-1 2/11/02
Drifter SV98 DrifterIS-2 6/20/02
(May 2006)
September 2013 76
Multiple Launch Vehicles Used
DELTA IIDELTA II PROTONPROTON12 launches12 launches
5 SVs / LV5 SVs / LV
3 launches3 launches
7 SVs / LV7 SVs / LV
LONG MARCH 2CLONG MARCH 2C EUROCKOTEUROCKOT6 launches6 launches
2 SVs / LV2 SVs / LV
1 launch1 launch
2 SVs / LV2 SVs / LV
September 2013 77
A Boeing Delta II rocket launched the latest additions to the Iridium satellite constellation Monday Feb. 11, 2002from Vandenberg Air Force Base, Calif. at 9:44 a.m. PST.
The Delta II launch vehicle deployed five vehicle deployed five satellites into low-Earth orbit to serve as spares for Iridium Satellite’s worldwide communications network.
September 2013 78
Iridium Satellite
Constellation
•Each Satellite Footprint is
Approximately 2800 Miles
in Diameter
•All Satellite Footprints •All Satellite Footprints
Overlap
•Each Satellite has 48 Spot
Beams
•Size of Each Spot Beam is
Approximately 250 Miles
in Diameter
•All Spot Beams on a
Satellite OverlapSeptember 2013 79
Handover in satellite systems• Several additional situations for handover in satellite systems
compared to cellular terrestrial mobile phone networks caused by the movement of the satellites
– Intra satellite handover
• handover from one spot beam to another
• mobile station still in the footprint of the satellite, but in another cell
– Inter satellite handover– Inter satellite handover
• handover from one satellite to another satellite
• mobile station leaves the footprint of one satellite
– Gateway handover
• Handover from one gateway to another
• mobile station still in the footprint of a satellite, but gateway leaves the footprint
– Inter system handover
• Handover from the satellite network to a terrestrial cellular network
• mobile station can reach a terrestrial network again
September 2013 80
Overview of LEO/MEO systems
Iridium Globalstar ICO Teledesic# satellites 66 + 6 48 + 4 10 + 2 288altitude(km)
780 1414 10390 ca. 700
coverage global ±70° latitude global global
min.elevation
8° 20° 20° 40°
frequencies 1.6 MS 1.6 MS ↑ 2 MS ↑ 19 ↓frequencies[GHz(circa)]
1.6 MS29.2 ↑19.5 ↓23.3 ISL
1.6 MS ↑2.5 MS ↓5.1 ↑6.9 ↓
2 MS ↑2.2 MS ↓5.2 ↑7 ↓
19 ↓28.8 ↑62 ISL
accessmethod
FDMA/TDMA CDMA FDMA/TDMA FDMA/TDMA
ISL yes no no yesbit rate 2.4 kbit/s 9.6 kbit/s 4.8 kbit/s 64 Mbit/s ↓
2/64 Mbit/s ↑# channels 4000 2700 4500 2500Lifetime[years]
5-8 7.5 12 10
costestimation
4.4 B$ 2.9 B$ 4.5 B$ 9 B$September 2013 81