What is Satellite Gateway | Advantages of Satellite Gateway

This page covers Satellite Gateway working operation and its basics. It mentions benefits or advantages of Satellite Gateway.

What is Satellite Gateway ?

The device which interfaces one side with the satellite and the other side with LAN (Local Area Network) is known as satellite gateway. The satellite gateway houses antenna and equipments which converts radio frequency signals to IP signals and vice versa as per terrestrial connections. IP refers to Internet Protocols used for internet access and for data transfer. Voice information can also be carried using Voice over IP protocol.

The major functions of a satellite gateway are as follows.
• It provides connectivity of terrestrial backhaul network with satellite (either GEO or LEO) using RF antenna. LEO satellites are placed in lower Earth orbit (~ 500 to 1500 Km) compare to Geostationary orbit satellites (~ 35800 Km) .
• It converts baseband data into RF signal for transmission to satellite over the air.
• It converts received RF signal back to baseband for decoding the data informations in various forms (voice, image, video, text) as desired.
• Content is delivered to cache/storage either by satellite via gateway or through terrestrial connectivity to EPC or CDN. EPC refers to Evolved Packet Core where as CDN refers to Content Delivery Network edge network.

Hybrid network architecture
Image courtesy : http://www.etsi.org/

The figure-1 depicts general architecture of hybrid network. Access side and core side are connected via various resources to server the users or customers requiring different services. The resources can be satellite based network, fixed network and mobile network as per different cellular technologies such as GSM, CDMA, 4G LTE, 5G etc. Intelligent User Gateway (IUG) provides secure broadband access, storage and QoS provisions at CPE (Customer Premises Equipment). Intelligent Network Gateway (ING) is a place where different user traffic are handled using various access links such as xDSL (e.g. ADSL, VDSL) , satellite, terrestrial lines and other mobile networks (e.g. EDGE (2G), UMTS (3G), HSPA (3G), LTE (4G) ). Both IUG and ING work together for routing different traffic types.

Following are the different scenarios for mobile communication using satellites and other cellular mobile networks. Landline subscribers are interfaced using PSTN either through cellular MSC (Mobile Switching Center) or through Gateway terrestrial connectivity.
Case #1 : Two mobile users can directly communicate to each other via satellites (such as LEO).
Case #2 : Two mobile users can communicate to each other via satellite gateway if they are located in vicinity of different satellites.
Case #3 : Mobile user and PSTN user can communicate using cellular mobile network such as GSM or using satellite via gateway.

Satellite Gateway working operation

The satellite gateway is installed with clear line of sight with the satellite from the ground. It is the only system which interfaces satellite from the earth for various services viz. voice, data and video over IP. It has to be maintained for years to provide support to long life of the satellites which is about 15 to 25 years. There should be sufficient place near the antenna of the satellite gateway to house indoor equipments for future expansion as well as to counter severe weather conditions. In order to avoid other regulatory issues, the land where satellite gateway has to be installed should be owned by the gateway operator in that region.

Satellite Network Architecture
Image courtesy : http://www.etsi.org/ , document : ETSI TR 103 272 V1.1.1

The figure-2 depicts architecture of the satellite network housing satellite gateway. Let us understand functions of different subsystems located at the satellite ground station. In the figure, ING and IUG refers to Intelligent Network Gateway and Intelligent User Gateway respectively.
➨TTC (Telemetry Tracking and Control) : It takes care of monitoring and controlling of transmit/receive information to/from the space segment.
➨SCC (Satellite Control Center) : It monitors and controls the space segment.
➨NCC (Network Control Center) : It takes care of control and synchronization of entire satellite ground station network.
➨NMS (Network Management System) : It takes care management of resources such as time instants, frequencies, codes, power levels etc. for uplink and downlink signals in the entire network. Refer VSAT NMS tutorial.
➨ST (Satellite Terminal) : These are small antenna size terminals located directly at user or company premises. Refer VSAT system basics for more information.
➨GW (Gateway) : It is the satellite gateway with large size antenna and other components as described in figure-3 below.

satellite ground station

The figure-3 depicts inside modules of a satellite gateway and their functions. Let us understand functions of different modules in a satellite gateway (GW1) terminal above.
➨RF Antenna : During transmission, it is used to relay modulated RF signal into the air to reach it to satellite with proper amplitude to overcome pathloss from ground to the satellite. During reception, it receives the satellite signal and pass it to the next module after applying its gain for decoding the information back.
➨Diplexer or OMT : It is used to separate both transmit and receive signals to their appropriate chains.
➨Transmit chain modules : Mux (Multiplexer), Modulator, Up converter, RF Power combiner, Power Amplifier are used during transmission.
➨Receive chain modules : Low Noise Amplifier, RF divider, Down converter, demodulator, demultiplexer are used during reception.
➨Baseband connectivity : Satellite modem such as DMD2400/2401 are used to provide baseband (voice/data) connections.
Refer article on Satellite Ground Station for more information.

Benefits or advantages of Satellite Gateway

Following are the benefits or advantages of Satellite Gateway:
➨It offers bidirectional access to the satellite from ground.
➨It connects access links and core networks via satellite where other transmission mediums are not possible to be deployed.
➨It offers higher system gain due to large antenna size.
➨It can be easily installed either directly on the ground or on vehicle with adequate battery power.

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