types of earth station in satellite communications

Slide Number 1Rev -, July 2001

Technical Introduction to Geostationary Satellite Communication Systems Original Prepared by Telesat Canada

Earth StationsEarth StationsVol 4

Photo Courtesy of Telesat Canada



Vol 4: Earth Stations

4.1: Types of Earth Station

Section 1Section 1

Types of Earth StationTypes of Earth Station

Photos Courtesy of Telesat Canada



4.1: Types of Earth Station

Seven Types of Earth Station

4.1.1 Typical Earth Station

4.1.2 Teleport

4.1.3 VSAT

4.1.4 Tracking Earth Stations

4.1.5 Offshore Earth Stations

4.1.6 Transportable Earth Stations

4.1.7 Receive Only Earth Stations




Typical Earth Station

• Contains an Antenna, LNA, HPA, Downconverter, Upconverter, and Modem.

• May accommodate one customer with a single service, or with several services.

• A typical antenna is 1.8m to 4.8m in size.

• HPA size ranges from 2 to 500 watts depending on application.

• Interfaces to the customer’s equipment directly if located at the customer’s premises, or connects to a terrestrial network via microwave, fiber or copper wire.

Sec 1: Types of Earth Station


4.1.1: Typical Earth Station

Figure 4.1.1. Typical Earth Station, Sable Island, Canada




Teleports• Full service satellite telecommunications

facilities designed to be shared amongst different users.

• Very large Earth Station with multiple antennas.

• Offers access to many satellites, whereas a Typical Earth Station accesses only a single satellite.

• Gateway for multiple types of services such as point to point and point to multipoint, offering broadcast video, program audio, voice & data services.

• Interconnects with regional telco operating companies and other service providers.


4.1.2: Teleports

Figure 4.1.2a. Teleports, Exterior





Teleports can provide studio production, video conferencing, and state-of-the-art editing facilities on premise.

Teleports are integrated facilities that give customers fast, convenient access to advanced telecommunications

The benefits teleports offer their customers include high reliability, high capacity, fast installation, lower costs, shared security, and network monitoring.


4.1.2: Teleports


Teleports

Figure 4.1.2b. Teleports, Interior




VSATsVSAT stands for Very Small Aperture Terminal.

“Aperture,” in this case, simply means “antenna.” Therefore, VSAT sites have small antennas, from 60 cm to 2.4m. These are typically installed on the ground, against a wall, or on a roof

VSAT equipment is usually of an “off the shelf” nature. It includes the antenna, an RF head, a Low Noise Block Downconverter (LNB), an Interfacility Link (IFL), and an Indoor Unit (IDU).

An IDU is a small desktop box or PC that communicates with the customer’s LANs, servers, PCs, TVs, kiosks, etc.


4.1.3: VSATs



Figure 4.1.3. VSATs



VSAT Advantages• VSAT is not limited as to location, as is terrestrial network buried cable.

• VSAT sites provide high quality digital communications regardless of their distance from terrestrial switching offices.

• VSATs are easily expandable and highly reliable.

• VSATs are a single-platform concept, offering the advantages inherent in simplicity.

• Where security is a concern, VSAT can be a private satellite network.

• VSATs Hub/Remote configuration is ideal for corporations requiring a point/multipoint network.

• VSATs offer multiple protocol options: SDLC, X.25, Ethernet (10 Mbps), Token Ring (4/16 Mbps), Transparent Bridging . . . and other specialized protocols.


4.1.3: VSATs




Part 3: VSATs

4.1.3.1: Topology

Vol 4: Earth Stations, Sec 1: Types of Earth Station

Figure 4.1.3.1a Typical VSAT Data Configuration

VSAT TopologySince VSAT is simply a term meaning that a very small antenna is used, VSAT can assume a number of topologies.

While VSAT is used in point-to-point services, it is typically a point-multipoint, star data network, or a full-mesh voice network.

In a data network, the terminus of all data links is called a “hub.”

The hub works to aggregate the customer’s remote data and pass it back and forth to some central location.

Configuration and control of the network is also accomplished from the hub.

Drawing Courtesy of Telesat Canada



Part 3: VSATs

4.1.3.1: Topology


Figure 4.1.3.1b Star versus Mesh Network

VSAT TopologyUnlike VSAT data networks, in VSAT voice networks a hub is not required, only a Network Control System (NCS) to organize the network.

In this case, the NCS sets up and breaks down calls between remotes, assigns resources, and maintains a Call Record Log (CRL) for billing.

A NCS system could be collocated with a Gateway or be a separate Earth Station.

Gateways are required to provide Private Switched Telephone Network (PSTN) access for the remote sites.

Remote to remote calls are permitted provided billing data is tracked.

Drawings Courtesy of Bharti BT



Part 3: VSATs

4.1.3.2: Access Method


Access MethodVSATs have been used in Single Channel per Carrier (SCPC) and Receive Only (RO) applications.

However, in practice, VSAT services are almost always configured as Time Division Multiple Access (TDMA) or Demand Assigned Multiple Access (DAMA).

In a typical TDMA data network, remotes access space segment bandwidth on a number of pre-assigned frequency slots, called “inroutes”. The remotes employ bursting carriers and accurate time synchronization. When given a time slot by the hub, the remote raises a carrier, bursts its data, then drops the carrier once again.



Part 3: VSATs

4.1.3.3: Applications


VSAT Applications• VSAT data networks are typically used for point-of-sale services, for

Automatic Teller Machine (ATM) banking, for stock control, for remote sensing and control, or for a host of other applications.

• VSATs are widely used to implement gas station transactions, and for sales and inventory control at the numerous locations of a chain of retail outlets.

• VSATs are also found in the remote sensing environment, especially for oil pipeline work.

• VSAT lends itself to all office environments and can be used to implement LAN/WAN extensions to a customer’s data network, or for internet access and email services.

• VSAT is the method of choice for telcos or private companies that need to provide telephone service to remote locations.



Tracking Earth StationsTracking Earth Stations use electronics and motors to keep antenna beam axis pointing towards the satellite.

Several factors will affect antenna movement:


• Size of satellite box.

• Mechanical loads on the antenna reflector & structure.

• Variation of propagation conditions, especially at higher frequencies.

4.1.4: Tracking Earth Stations


Figure 4.1.4 A Tracking Earth Station




Tracking Earth Station TypesHorizon to Horizon

• Requires 360 degree tracking from horizon to horizon.

• Used for Tracking LEO and MEO satellites and TT&C functions during launch orbit services.

FSS GEO• FSS GEO satellite tracking antennas are usually encountered on

large antennas of 8.0m or more, or for inclined-orbit satellites.

• For FSS GEO tracking, the antenna moves only millimeters to optimize signal strength.


4.1.4: Tracking Earth Stations


• There are several methods for automatically tracking the satellite:• Step Track• Monopulse • Program/Memory Tracking



Types of Offshore Earth Stations


4.1.5: Offshore Earth Stations


Figure 4.1.5 Types of Offshore Earth Station

4.1.5.1 Fixed 4.1.5.2 Marine Stabilized

Photo Courtesy of Telesat Canada Photo used by Permission

of Sea Tel, Inc.



Fixed• May be installed in very harsh weather environments.

• A high wind-survival antenna must be considered.

• Ocean salt will cause severe corrosion. Hardware must be stainless steel or properly protected.

• Equipment may be mounted indoors or outdoors depending on antenna accessibility.

• Due to remote nature, offshore earth stations are often difficult and costly to reach. Therefore, high availability is required.

• Typical applications include two-way fax, voice, multi-conferencing and Internet access.

• Typical data requirements are 128 to 512 kbps.

Part 5: Offshore Earth Stations

4.1.5.1: Fixed




• Must provide effective antenna stabilization and tracking accuracy in harsh weather conditions.

• Antenna systems are housed under a radome.

• High speed data transmission and multi-channel voice communications offer two-way fax, voice, multi-conferencing, Internet access and video links.

Marine Stabilized

Part 5: Offshore Earth Stations

4.1.5.2: Marine Stabilized


• Typical data requirements are 64 to 256 kbps. Up to 1,544 Mbps have been supported.

• End users include the offshore oil industry, cruise ships, navies around the globe, freighters, tankers and fishing ships.

Figure 4.1.5.2 Marine Stabilized Antenna with Radome

Photo Courtesy of DMS




News happens anywhere at any time. The ability to rapidly deploy to the scene and quickly establish a satellite uplink back to a news gathering studio is important to news organizations. These units may provide only rudimentary satellite links, or may be outfitted with complete video editing studios.Three principle kinds are presented here.

4.1.6.1 Video SNG

4.1.6.2 Data

4.1.6.3 Voice

Types

4.1.6: Transportable Earth Stations




Video Satellite News Gathering (SNG)• The Video SNG is a self contained mobile

unit with many variations and sizes, capable of uplinking and downlinking video, data and voice communications.

• Early models were almost always C-Band, but now most are Ku-Band.

• Options include operating frequency, size of vehicle, type of body, electrical power source, type of antenna, type of traffic (analog or video or both), size and type of HPA, attached editing and production room, attached microwave antenna for TV backhaul.

Part 6: Transportable Earth Sations

4.1.6.1: Video Satellite News Gathering


Figure 4.1.6.1 Video SNG Trucks

• Video SNG truck may be equipped with automatic antenna positioning systems for rapid deployment.

These Photographs are the proprietary property and trade secrets of BAF Communications/Mobil Tech Inc. and are issued in strict confidence. No reproduction or use shall be made without prior written consent of BAF Communications/Mobil Tech Inc.



Data• End users for this type of service include the oil

& gas industry, the military, emergency & disaster response officials, and datalink restoration providers.

• They are designed for 1 person to install and commission within 4 hours of arriving on site.

• The antenna and electronics are packaged for frequent travel.

• Indoor electronics are installed in shock mounted racks.

• This earth station can be a trailer type or a collection of hard and soft transit cases.

• Typical data requirements are 64 to 256 kbps. Up to 1,544 Mbps have been supported.


4.1.6.2: Data


Figure 4.1.6.2a Data Transportables


Photo Courtesy of BAF Communications/Mobil Tech Inc.



Data• Transit cases come in various forms and sizes.

• Options are numerous, as are the types of materials used in case construction.

• Weight is a very important consideration. Soft packs are very light but less protective. Aluminum or plastic cases are much heavier but offer better protection.

Figure 4.1.6.2b. Data Transportable Transit Cases


4.1.6.2: Data





Voice• Voice transportables cases are identical to data transportables except

that they use different baseband equipment.

• Voice channels could be mutiplexed onto one data carrier or individually modulated as per SCPC type systems.

1.2m Voice Transportable IDU with 4 voice circuits

in a shock mounted rack1.8m quick deployantenna


4.1.6.3: Voice


Figure 4.1.6.3 Voice Transportable SystemsPhotos Courtesy of Telesat Canada



Receive Only (RO) Earth Stations• The first satellite television systems for the consumer were Television

Receive Only (TVRO) systems.

• TVRO satellite systems are characterized by big C-Band dishes, typically 6-12 feet across. Many use motorized antennas to access multiple satellites.

• Programming is available in clear and scrambled mode, where scrambled channels require a subscription.

• Distribution of clear signals to cable head-ends includes hotels, educational institutions, sports, news events, foreign language service, music, shopping channels, and major network program distribution

• TVRO owners can now receive both C and Ku-Band on a single dish.


4.1.7: Receive Only Earth Stations


Figure 4.1.7a C-Band TVROs




Receive Only Earth Stations• In the 1990’s, Direct Broadcast Satellites (DBS) appeared.

• These high powered, high frequency satellites allow for a much smaller receive antenna.

• Current DBS systems use scrambling equipment to prevent unauthorized access.

• Digital television has become economical due to compression algorithms permitting 10 or more television channels per transponder, and because mass production hardware costs have been significantly reduced.


4.1.7: Receive Only Earth Stations


Ku-Band 30 inch elliptical TVRO with single LNB

Dual LNB configuration for receiving 2 satellites

Figure 4.1.7b. DBS Systems

Photos Courtesy of www.kusat.com

types of earth station in satellite communications

Engineering