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					VSAT– the only viable solution for
        Rural Pakistan




                                     1
                    Why VSAT?
VSAT networks provides:
 Reliability in transmission of data (data, voice, video)
 Allocation of resources to different users
  (bandwidth, amplification power)
 Fixed network solutions at reasonable price
 Provide point-to-multipoint (broadcast), multipoint-
  to-point (data collection), point-to-point
  communications and broadband multimedia
  services.
 Serviced in land area which are difficult to install
  (remote locations ,desert areas).
 An ability to have direct access to users and user
  premises.



                                                             2
           Satellite Services & Applications
        Voice/Video/Data Communications              GPS/Navigation
        • Mobile Telephony                           • Position Location
        •Rural Telephony                             • Timing
        • News Gathering/Distribution                • Search and Rescue
        • Internet Trunking                          • Mapping
        • Corporate VSAT Networks                    • Fleet Management
        • Distance-Learning                          • Security & Database Access
        • Videoconferencing                          • Emergency Services
        • Business Television
        • Broadcast and Cable Relay
        • VOIP & Multi-media over IP
                                          Remote Sensing
                                          • Pipeline Monitoring
                                          • Infrastructure Planning
Direct-To-Consumer
                                          • Forest Fire Prevention
• Broadband IP
                                          • Urban Planning
• DTH/DBS Television
                                          • Flood and Storm watches
• Digital Audio Radio
                                          • Air Pollution Management
• Interactive Entertainment & Games
• Video & Data to handhelds               • Geo-spatial Services

                      Infrastructure / Support Services
   Launch Vehicles Ground Equipment Insurance Manufacturing                    3
     VSAT Characteristic and Advantage
 Reliability: reliable satellite transmission of data, voice and video
   between an unlimited number of geographically dispersed sites or
   from these sites to headquarters

 Flexibility: The VSAT networks offer enormous expansion
   capabilities; On the other hand, VSATs offer unrestricted and
   unlimited reach. Additional VSATs can be rapidly installed to support
   the network expansion to any site, no matter however remote.

 Network Management: Network monitoring and control of the
   entire VSAT network is much simpler than a network of leased lines,
   easily integrates end-to-end monitoring and configuration control for
   all network subsystems.

 A low mean-time to repair - few hours, compare to leased
   lines which extends up to a few days. Essentially, lesser elements
   imply lower MTTR. Uptime of up to 99.5 percent is achievable on a
   VSAT network. This is significantly higher than the typical leased line
   uptime of approximately 80-85%.


                                                                             4
    VSAT Characteristic and Advantage
 Cost: VSAT network offers significant savings over 2-3 years
  timeframe. The service charges depend on the bandwidth
  which is allocated to the network in line with customer
  requirements. In Pakistan’s scenario, The cost of bandwidth on
  optical fibre is comparably high than the satellite bandwidth
  when the distance increases a distance of 500 km. (Satellite
  communication is totally distance-sensitive.)

 Link Budgets: RF equipment would cater to the requirements of
  the network topology and satellite modems in use. The link
  Budget estimates the ground station and satellite EIRP
  (Effective Isotropic Radiated Power) required. Calculations of
  signal levels through the system to ensure the quality of
  service should normally be done, prior to the establishment of
  a satellite link.




                                                                   5
                    Satellite-Fiber Comparison
                                Comparing Satellite and Fiber Characteristics

   Capability         Fiber Optic       Geo Satellite in a      Meo Satellite in a     Leo Satellite in a
                         Cable           Global System           Global System          Constellation
                        Systems
  Transmission        10 Gbps - 3.2         Single Sat              Single Sat            Single Sat
      Speed         Terabits/second*     1 Gbps - 10 Gb ps      0.5 Gbps - 5 Gbps      .01 Gbps - 2Gbps
                         - 11  - 12            -6   - 11               -6  - 11              -2    91
    Quality of         10 10                10 10                   10 10                  10 10
     Service
  Transmission        25 to 50 ms            250 ms                100- 150 ms             25- 75 ms
     latency
     System           93 to 99.5%      99.98% (C - Ku band)    99.9% (C - Ku band)   99.5% (L -C- Ku band)
 Availability w/o                         99% (Ka ban d)         99% (Ka band)          99% (Ka band))
     Backup
  Broadcasting        Low to Nil              High                    Low                    Low
   Capabilities
 Multi - casting         Low                  High                    High                 Medium
   Capabilities
Trunking               Very High              High                  Medium                   Low
Capabilities
Mobile Services           Nil           Medium -to- High              High                   High

                                                                                                       6
                “Typical” Fixed Satellite Network
 Applications
 • Credit Card Validation
 • ATM/Pay at the Pump
 • Inventory Control
 • Store Monitoring
 • Electronic Pricing                                                 Network HUB
 • Training Videos
 • In-Store Audio
 • Broadband Internet Access
 • Distance Learning


Apartment
 Buildings                                                 Internet


 Gas Stations

                                                                         Corporate Data
                                                                           Center/HQ
 Branch Offices          Corporate Offices   Residential


  Some large scale corporate networks have as many as 10,000 nodes
                                                                 7
                     Satellite Frequencies
 There are specific frequency ranges used by commercial satellites.
     L-band                     (Mobile Satellite Services)
         1.0 – 2.0 GHz
     S-band                     (MSS, DARS – XM, Sirius)
         1.55 – 3.9 GHz
     C-band                     (FSS, VSAT)
         3.7 – 6.2 GHz
     X-Band                     (Military/Satellite Imagery)
         8.0 – 12.0 GHz
     Ku-band                    (FSS, DBS, VSAT)
         11.7–14.5 GHz
     Ka-band                   (FSS “broadband” and inter-satellite links)
         17.7 - 21.2GHz and 27.5 – 31 GHz                                    8
                           Orbital Options

 A Geosynchronous satellite (GEO) completes one
  revolution around the world every 23 hrs and 56
  minutes in order to maintain continuous positioning
  above the earth’s sub-satellite point on the equator.

 A medium earth orbit satellite (MEO) requires a
  constellation of 10 to 18 satellites in order to
  maintain constant coverage of the earth.

 A low earth orbit satellite (LEO) offers reduced
  signal loss since these satellites are 20 to 40 times
  closer to the earth in their orbits thus allowing for
  smaller user terminals/antennas.

                                                          9
               Geostationary Orbit (GEO)
Characteristics of Geostationary (GEO) Orbit Systems
•   User terminals do not have to track the satellite
•   Only a few satellites can provide global coverage
•   Maximum life-time (15 years or more)
•   Above Van Allen Belt Radiation
•   Often the lowest cost system and simplest in terms of tracking and high
    speed switching

Challenges of Geostationary (GEO) Orbit
•   Transmission latency or delay of 250 millisecond to complete up/down link
•   Satellite antennas must be of larger aperture size to concentrate power and
    to create narrower beams for frequency reuse
•   Poor look angle elevations at higher latitudes



                                                                              10
Geostationary Orbit Today




                            11
               Low Earth Orbit (LEO)
Characteristics of Low-Earth Orbit (LEO) Systems
 - Low latency or transmission delay
 - Higher look angle (especially in high-latitude regions)
 - Less path loss or beam spreading
 - Easier to achieve high levels of frequency re-use
- Easier to operate to low-power/low-gain ground antennas
Challenges of Low-Earth Orbit (LEO) Systems
- Larger number of satellites (50 to 70 satellites). Thus higher
  launch costs to deploy, build, and operate.
- Harder to deploy, track and operate. There is higher
  TTC&M costs even with cross links.
- Shorter in-orbit lifetime due to orbital degradation



                                                                   12
            Medium Earth Orbit (MEO)
Characteristics of Medium-Earth Orbit (MEO) Systems
• Less latency and delay than GEO (but greater than LEO)
• Improved look angle to ground receivers in higher latitudes
• Fewer satellites to deploy and operate and cheaper TTC&M
  systems than LEO (but more expensive than with GEO)
• Longer in-orbit lifetime than LEO systems (but less than GEO)


Challenges of Medium-Earth Orbit (MEO) Systems
• More satellites to deploy than GEO (10 to 18 vs. 3 to 4)
• Ground antennas are generally more expensive and complex
  because of the need to track satellites. Or, one must use lower-
  gain, quasi-omni antennas.
• Increased exposure to Van Allen Belt radiation
                                                                13
                           Transponders
• The transponder is the “brain” of the satellite - provides the
  connection between the satellite’s receive and transmit
  antennas.
• Satellites can have 12 to 96 transponders plus spares,
  depending on the size of the satellite.
• A transponder bandwidth can frequently be 36 MHz, 54 MHz,
  or 72 MHz or it can be even wider.
• A transponders function is to
   • Receive the signal, (Signal is one trillion times weaker then when transmitted)
   • Filter out noise,
   • Shift the frequency to a down link frequency (to avoid interference
     w/uplink)
   • Amplify for retransmission to ground
                                                                                  14
            Frequency Efficiency
• The vital resource in satellite communications is spectrum.
• As the demand for satellite services has grown, the solution
  has been;
   • To space satellites closer together,
   • Allocate new spectrum in higher bands,
   • Make satellite transmissions more efficient so that more
     bits/Hz can be transmitted, and
   • To find ways to re-use allocated spectrum such as through
     geographic separation into separated cells or beams or through
     polarization separation
• Today the satellites systems transmit more efficiently than
  ever before but interference is now a bigger problem - there
  is a basic trade off;
   • The higher the frequency the more spectrum that is available
   • But, the higher the frequency the more problems with
     interference from other users terrestrial, unlicensed, etc.

                                                                      15
World Satellite Industry Revenues

                                                            $91.0
                                                    $86.1
                                            $78.6
                                    $73.7

                            $60.4
                    $55.0
            $49.1
    $38.0




                                                                    16
               World Satellite Services Revenue
                                                                                                $55.9
                                                                                        $49.1
                                                                           $ 46.5
                                                                 $ 39.2

                                                        $ 29.7
                                            $ 24.4
                                 $ 21.1
                       $15.8




            FSS $      6.1     $ 6.8      $ 7.3      $ 8.6    $ 9.2    $    8.9     $     8.7   $    9.6
            MSS $      0.7     $ 0.8      $ 1.0      $ 1.3    $ 2.1    $    1.4     $     1.3   $    1.7
            DBS $      9.0     $ 13.5     $ 16.1     $ 19.8   $ 27.9   $   36.2     $    39.1   $   44.7

FSS=VSAT services, remote sensing, and transponder leasing
MSS=Mobile telephone and mobile data
DBS/DARS=DTH TV, DARS, and Broadband
                                                                                                           17
World Ground Equipment Revenues




  Includes: Gateways, NOCs, Satellite News Gathering equipment, flyaways,
 VSATs, DBS Dishes, DARS equipment, satellite phone booths, satellite phones
                                                                               18
                                              Global Supply vs. Demand
                                               GEO Communications Satellites and Launches

                                70


                                60
Number of Satellites/Launches




                                50


                                40


                                30


                                20


                                10


                                 0
                                     1995   1996    1997      1998         1999     2000       2001    2002   2003
                                                      Launches                    Satellites Ordered
                                                      Satellite Capacity          Launch Capacity               19
                    Ground Antennas
 The size of the antenna depends on the satellite
  frequency band used, the data rate, and whether the
  service is bidirectional or receive only
    Higher data rates require larger antennas and/or higher
     power
    Higher transmit capability (EIRP) of the satellite allows
     the antenna size to be reduced
    The use of spot beams instead of global beams improves
     VSAT link performance
    Receive-only antennas can be substantially smaller




                                                                 20
     Critical to Flow of Information
• Newsgathering – First choice
  for live coverage, providing
  high-bandwidth video links
  from remote locations to
  capture “breaking news”


• Program Delivery – National broadcasts from four major
  television networks and more than 180 cable channels are
  relayed to over 10,000 local cable systems via satellite




                                                             21
              VSAT Technology
 Bands C-band (4-6 GHz), Ku-band (10-20 GHz)
  and Ka-band (20-30 GHz) that require different
  licensing approaches.
 Entities
    a) the Space Segment operator; b) the satellite network
     operator, who operates one or more Gateway Stations or
     Network Control Stations (HUBs) or other ground stations;
     c) the Satellite Service Provider; d) the subscriber who uses
     individual VSAT equipment
 Types – Oneway – DTH and Two-way
 Connectivity – Point to Point (Mesh), Point to
  Multipoint (star, hub at centre), Multipoint to
  multipoint (hybrid)
                                                                     22
23
     VSAT: A Consistent Performer
160,000

140,000

120,000

100,000

 80,000

 60,000

 40,000

 20,000

     -
          85   86   87   88   89   90 91   92   93   94   95 96   97   98   99   00   01
                                                                                      24
       VSAT Vs. Leased Line
 VSAT
   Footprint across the country
   High initial investment
   High reliability – Uptime of 99.5%
   No recurring b/w costs
 Leased Line
   Option available only at areas with an
    existing VSAT hub
   Low initial investment
   Dependant on the Local Hub
   Recurring Bandwidth costs



                                             25
DVB - RCS




            26
                DVB-RCS
 Standardisation:
   DVB-RCS compliant terminals can speak to
    all DVB-RCS compliant Gateways.

   The terminal is primarily a slave and the
    Gateway is in charge of efficient resource
    utilisation, fair sharing of resources and
    optimising performance.




                                                 27
                                  DBV-RCS
•   A DVB/RCS user will typically require Internet access on best effort basis.

•   He will not run a time critical application (i.e.video).

•   This customer must accept limited/occasional accessibility due to the shared usage
    of the capacity.

•   He has no need for dedicated channel, and his applications are not time critical.

•   He must accept shared use of common infrastructure with other users.

•   If there is a need for crypto, the crypto equipment will need to synchronies each
    time the remote terminal make a connection.

•   A good solution if Internet & Data is the most important services and a best effort
    service is what the users require. VoIP can be used as a additional service and with
    limited usage of voice service DVB-RCS can still be a type of service that a very
    small office.                                                                    28
 Fixed Satellite Technology Options
TDM/TDMA
                      Traditional data VSAT
                       systems
                      Low cost remotes,
                       expensive hub
                      Star network topology
                      Transactional data
                                    Credit card validation/POS
                                    Internet …
                      Low user data rate




                       Frequency
                                              Time




                                                              29
 Fixed Satellite Technology Options
SCPC/MCPC (FDMA, Frequency divided
 multiple access)
                         Point-to-Point
                         IDR –
                          DCME(compression)
                         Gateways
                         Uplinks
                         Fixed bandwidth
                         Broadcast




                         Frequency
                          Audio/Video
                         Static traffic patterns

                                     Time




                                                    30
                      SCPC / MCPC
 A typical SCPC customer runs business critical real time applications.
 This customer has high requirements to QoS.
 He also typically runs a wide range of services such as voice, video,
  Internet, ERP systems.
 Crypto equipment will have no difficulties in this environment, as there
  are dedicated channels that are always on.
 This customer demands a fixed Star network, which will fulfil the
  requirements he operates in that might be difficult to predict in advance
  (especially geographically diversity).
 Technology typically used as a Star VSAT Network or as Point to Point
  connection, (SCPC duplex)
 This customer dos not have the need for occasional “bursting” or
  accept to pay for the bandwidth required.




                                                                              31
 Fixed Satellite Technology Options
SCPC/DAMA
                      Centralized Net Mgmt
                      Star and Mesh
                      Low cost remotes
                      One modem/Interface
                       per channel
                      Large gateways
                       required




                      Frequency   Time




                                              32
                       SCPC / DAMA
 A typical SCPC / DAMA user, runs business critical real time
  applications, but has to make sure that the application allows the
  DAMA system to burst (increase or decrease the bandwidth). Or use
  dedicated bandwidth for the RTA when required (When the application
  is in use).
 This customer has high requirements to QoS.
 He also typically runs a wide range of services such as voice, video,
  Internet, ERP systems.
 Crypto equipment will have no difficulties in this environment.
 This customer demands a flexible network, which will fulfil the
  requirements he operates in that might be difficult to predict in advance
  (especially geographically diversity) and have a demand / need of
  bursting (higher data rate if available).
 Technology typically used for a VSAT Network as Star or/and Mesh,
  with a number of remote terminals that cheers the total allocated
  bandwidth pool (Inbound).
 In cases where there is time diversity between the remote terminals, the DAMA
  functionality improves the efficiency and utilisation of space segment.
 He also wants a dedicated network/bandwidth with no sharing of resources with
  other customers.                                                                33
    Satellite Technology Options
TDMA/DAMA
                      Star/Mesh/Hybrid
                       networks
                      Multimedia,
                       multiservice
                      Efficient space
                       segment utilization
                      Easily expand
                       network and site
                       capability




                                             34
      Satellite Technology Options

SCPC     Frequency



                              Time
         Frequency




DAMA
                              Time



  Sample when a SCPC system is cost-effective




  Sample when a DAMA system is cost-effective
  If is a number of sites in a VSAT Network
                                                One block = 64 Kbps

                                                                      35
                   Summary
Satellite technology is the fastest way to get a
 reliable connection from A to B in an emergency
 situation.

  Both a SCPC and a DAMA solution can be used
   in an emergency situation as a VSAT
   connection. Both technologies can be used as
   a FlyAway (Quick deploy) system. Both
   systems can run the same services.




                                                    36
               Type of satellite service

 International Telephony – using Public Switched
  Telephone Network (PSTN)
    Intermediate Data Rate (IDR)
    Time Division Multiple Access (TDMA)
 Broadcasting
    TV Uplink
    Television Receive Only (TVRO)
    Digital Satellite News Gathering (DSNG)
 VSAT
      Personal Earth Station (PES-TDMA)
      Telephony Earth Station (TES-TDMA)
      Domestic IDR/Single Channel Per Carrier (SCPC)
      FDMA (Frequency Division Multiple Access)



                                                        37
                 Type of VSAT technology
              TDMA
          Time-division
          Multiple Access



              VSAT                                     PAMA
           TECHNOLOGY                               Pre-Assigned
                                                    Multiple Access
    SCDC                 FDMA
Single-carrier    Frequency Division
 per Channel        Multiple Access

                                                          FDMA

                                           DAMA                     CDMA
                                       Demand Assigned           Code Division
                                        Multiple Access          Multiple Access



                                                                           38
                    VSAT Topology
 STAR - the hub station controls and monitors can
  communicates with a large number of dispersed VSATs.
  Generally, the Data Terminal Equipment and 3 hub antenna is in
  the range of 6-11m in diameter. Since all VSATs communicate
  with the central hub station only, this network is more suitable
  for centralized data applications.

 MESH - a group of VSATs communicate directly with any other
  VSAT in the network without going through a central hub. A
  hub station in a mesh network performs only the monitoring
  and control functions. These networks are more suitable for
  telephony applications.

 HYBRID Network - In practice usually using hybrid networks,
  where a part of the network operates on a star topology while
  some sites operate on a mesh topology, thereby accruing
  benefits of both topologies.




                                                                     39
         TDMA (time-division multiple access)

 When numerous remote sites communicate with one
  central hub, this design is similar to packet-switched
  networks.
 Because of competition with one another for access
  to the central hub, it restrict the maximum bandwidth
  in most cases to about 19.2 kbps.
 all VSATs share satellite resource on a time-slot
  basis.
 Usually used in STAR topology as a transmission
  technique.
 Offered to domestic needs.




                                                           40
                 TDMA (time-division multiple access)




     Copyright Maxis

The VSAT Hub communicates with all dispersed VSATs (typically a 1.8-meter
diameter parabolic-shaped dish) on an outgoing channel of up to 512kbps based on
the TDM scheme. The incoming or return channel from the dispersed VSATs uses
the TDMA channel technology that enables a large number of the respective VSATs
to share this single return channel. The incoming routes typically operate at
128kbps, and can go up to a maximum bandwidth of 256kbps.                     41
      SCPC (single-carrier per channel)

 SCPC-based design provides a point-to-point
  technology, making VSAT equivalent to
  conventional leased lines.
 dedicated bandwidth of up to 2 Mbps
 Usually use in an international VSAT
  services in Asia-Pacific.




                                                42
                  SCPC (single-carrier per channel)




Copyright Maxis

In the Hub-to-Remote configuration, one end of the VSAT link (normally the
customer's HQ) is connected to the 11-meter VSAT Hub (Earth Station) via a
terrestrial leased line. A VSAT antenna at the remote end or the distant end
(normally the branch office) of the VSAT link is then interconnected to the VSAT
hub via the satellite.                                                             43
                   SCPC (single-carrier per channel)




 Copyright Maxis



VSAT links with a Remote-to-Remote configuration bypass the VSAT
Hub and has a stand-alone VSAT antenna at both ends of the link.
Typical VSAT antenna size ranges from 1.8m to 2.4m.

                                                                   44
         FDMA (Frequency Division Multiple Access)

 oldest method for channel allocation
 the satellite channel bandwidth is broken into
  frequency bands for different earth stations
 the earth stations must be carefully power-controlled
  to prevent the microwave power spilling into the
  bands for the other channels. Here, all VSATs share
  the satellite resource on the frequency domain only.

3 type:
 PAMA (Pre-Assigned Multiple Access);
 DAMA (Demand Assigned Multiple Access); and
 CDMA (Code Division Multiple Access).




                                                          45
     PAMA (Pre-Assigned Multiple Access)
 The VSATs are pre-allocated a designated
  frequency. Equivalent of the terrestrial (land
  based) leased line solutions.
 PAMA solutions use the satellite resources
  constantly. Therefore, no call-up delay in the
  interactive data applications or high traffic
  volumes.
 PAMA connects high data traffic sites within
  an organization.



                                                   46
       DAMA (Demand Assigned Multiple Access)
 The network uses a pool of satellite channels, which are
  available for use by any station in that network.
 On demand, a pair of available channels is assigned, so that a
  call can be established. Once the call is completed, the
  channels are returned to the pool for an assignment to another
  call.
 Since the satellite resource is used only in pro-portion to the
  active circuits and their holding times, this is ideally suited for
  voice traffic and data traffic in batch mode.
 DAMA offers point-to-point voice, fax, data requirements and
  supports video-conferencing. Satellite connections are
  established and dropped only when traffic demands them.




                                                                        47
      CDMA (Code Division Multiple Access)
 Under this, a central network monitoring system allocates a
  unique code to each of the VSATs. Enabling multiple VSATs to
  transmit simultaneously and share a common frequency band.
 The data signal is combined with a high bit rate code signal
  which is independent of the data.
 Reception at the end of the link is accomplished by mixing the
  incoming composite data/code signal with a locally generated
  and correctly synchronized replica of the code.
 Since this network requires that the central network
  management system co-ordinates code management and clock
  synchronization of all remote VSATs, STAR topology is the
  best one.
 Mainly used for interference rejection or for security reasons in
  military systems.




                                                                      48
    Opportunities in VSAT technology

 Voice over IP (VoIP) via satellite
 Frame Relay via satellite
 ATM via satellite
 Video-on-demand via satellite
 Multimedia application
   Internet/e-mail connection
   Telemedicine
   Distance learning




                                       49
     VSAT: A Consistent Performer
160,000

140,000

120,000

100,000

 80,000

 60,000

 40,000

 20,000

     -
          85   86   87   88   89   90 91   92   93   94   95 96   97   98   99   00   01
                                                                                      50
          Users of Satellite
          Communications
 Banking Sector
 Data Networks
 Telecommunications (Cellular)
 Power Production
 Infrastructure
 Oil & Gas




                                  51
Motivation to use VSAT

                  VS




     The last mile problem
     Hard to reach areas
     Reliability
     Time to deploy (4-6 months vs. 1-2 weeks)
     Flexibility
     Cost ( If distance is more than 500 km then the
      VSAT solution is more cost-effective as
      compared to the optical fiber.)                   52
  VSAT IMPLEMENTATION - 2
 There are basically two ways to implement
  a VSAT Architecture

 STAR
   VSATs are linked via a HUB
 MESH
   VSATs are linked together without going
    through a large hub




                                              53
               VSAT IMPLEMENTATION - 3




     Higher Propagation delay                            Lower Propagation delay (250 ms)
     Used by TDMA VSATs                                  Used by PAMA/DAMA VSATs
     High central hub investment                         Lower central hub investment
     Smaller VSAT antenna sizes (1.8 m typically)
     Lower VSAT costs
                                                         larger VSAT antenna sizes (3.8 m typically)
     Ideally suited for interactive data applications    Higher VSAT costs
     Large organizations, like banks, with centralized   Suited for high data traffic
         data processing requirements
                                                         Telephony applications and point-to-point high-
                                                             speed links


Source: www.bhartibt.com                                                                           54
Basic Topologies
   Point to Point (SCPC)




    Earth station
                                  Point to Multipoint (TDMA)
    with terrestrial
    tail or
    customer           Customer
    located            located
    antenna            antenna




                                     Earth Station
                                     with terrestrial
                                     tail to customer
                                     premises




                                                               55
    VSAT STAR ARCHITECTURE - 2

• In this network architecture, all of the traffic is routed
via the master control station, or Hub.
• If a VSAT wishes to communicate with another
VSAT, they have to go via the hub, thus necessitating a
“double hop” link via the satellite.
• Since all of the traffic radiates at one time or another
from the Hub, this architecture is referred to as a STAR
network.



                                                           56
VSAT STAR ARCHITECTURE - 2


                         All communications to and
                         from each VSAT is via the
                         Master Control Station or
                         Hub




Master Control Station
     (The Hub)
                               VSAT
                            Community



                                                     57
      VSAT STAR ARCHITECTURE - 3

       VSAT



       VSAT


                                  Satellite                 HUB
       VSAT



       VSAT



       VSAT




Topology of a STAR VSAT network viewed from the satellite’s perspective
Note how the VSAT communications links are routed via the satellite to the
Hub in all cases.

                                                                             58
   VSAT MESH ARCHITECTURE - 1

• In this network architecture, each of the VSATs has
the ability to communicate directly with any of the
other VSATs.
• Since the traffic can go to or from any VSAT, this
architecture is referred to as a MESH network.
• It will still be necessary to have network control and
the duties of the hub can either be handled by one of the
VSATs or the master control station functions can be
shared amongst the VSATs.


                                                        59
     VSAT MESH ARCHITECTURE - 3

       VSAT                                                           VSAT


       VSAT                                                           VSAT

                                      Satellite
       VSAT                                                           VSAT


       VSAT                                                           VSAT


       VSAT                                                           VSAT




Topology of a MESH VSAT network from the satellite’s perspective
Note how all of the VSATs communicate directly to each other via the satellite

without passing through a larger master control station (Hub).

                                                                                 60
VSAT MESH ARCHITECTURE - 2




                    VSAT
                   Community


                               61
      ADVANTAGES OF STAR
 Small uplink EIRP of VSAT (which can be a hand-
  held telephone unit) compensated for by large
  G/T of the Hub earth station
 Small downlink G/T of user terminal compensated
  for by large EIRP of Hub earth station
 Can be very efficient when user occupancy is low
  on a per-unit-time basis




                                                     62
   DISADVANTAGES OF STAR

 VSAT terminals cannot communicate
  directly with each other; they have to go
  through the hub
 VSAT-to-VSAT communications are
  necessarily double-hop
 GEO STAR networks requiring double-hops
  may not meet user requirements from a
  delay perspective



                                              63
     ADVANTAGES OF MESH
 Users can communicate directly with each
  other without being routed via a Hub earth
  station
 VSAT-to-VSAT communications are
  single-hop.
 GEO MESH networks can be made to meet
  user requirements from a delay
  perspective.




                                               64
   DISADVANTAGES OF MESH

 Low EIRP and G/T of user terminals causes
  relatively low transponder occupancy
 With many potential user-to-user connections
  required, the switching requirements in the
  transponder will almost certainly require On-Board
  Processing (OBP) to be employed
 OBP is expensive in terms of payload mass and
  power requirements




                                                       65
            Delay Considerations

Satellite Scenario:
• Typical slant path range for GEO satellite: 36,000 km
• One way transmission: ESSatelliteES: 2 x Range
• One way delay: 2 x (range/velocity) = 260 ms

Fiber Optic Transcontinental Link:
• 4000 km has about 13 ms delay

Additionally to either case: Processing delay.
• Several tens to over a hundred ms.

                                                          66
Satellite Network Configurations
              VSAT




                                   67
 Frequency-Division Multiplexing
 Alternative uses of channels in point-to-point
  configuration
      1200 voice-frequency (VF) voice channels
      One 50-Mbps data stream
      16 channels of 1.544 Mbps each
      400 channels of 64 kbps each
      600 channels of 40 kbps each
      One analog video signal
      Six to nine digital video signals




                                                   68
69
                Value of Satellite Systems

• Value of satellite systems grows with widely distributed networks
  and mobility of users


• Satellite systems perform most effectively when:
   • interconnecting wide distributed networks,
   • providing broadcasting services over very wide areas such as a country,
     region, or entire hemisphere
   • providing connectivity for the “last mile” in cases where fiber networks
     are simply not available for interactive services.
   • providing mobile wideband and narrow band communications
   • satellites are best and most reliable form of communications in the case of
     natural disasters or terrorist attacks - fiber networks or even terrestrial
     wireless can be disrupted by tsunamis, earthquakes, etc..
                                                                            70
71
QUICK LINX WIRELESS




                      72

				
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