A brief explanation of some of the terms used in the satellite connectivity industry.


The amount of data that can be transmitted in a fixed amount of time. Most commonly expressed in bits-per-second (bps with a small b) but occasionally in Bytes-per-second (Bps with an upper case B). Kbps is kilobits per second, or 1000 bits per second. Mbps is a million bits per second.


The C-band is primarily used for voice and data communications as well as backhauling. Because of its weaker power, it requires a larger antenna, usually above 1.8m (6ft). However, due to the lower frequency range, it performs better under adverse weather conditions on the ground. It operates in the frequency range for VSAT satellite communication from 3.7 to 4.2GHz for downlink and 5.925 to 6.425GHz for uplink communication. C-band systems are light-heartedly referred to as a ‘BUD’ – or big ugly dish.


Decibel watts is a measurement of energy beamed from a satellite to a point on the earth. The higher the dBW, the stronger the signal strength, and the smaller the satellite dish that’s required.


Dynamic host configuration protocol is a protocol for assigning dynamic IP addresses to devices on a network. With dynamic addressing, a device may have a different IP address each time it connects to the network. DHCP also supports a mix of static and dynamic IP addresses. Windows ICS uses the address range of through when it assigns addresses. It also works fine when computers on the ICS network are assigned addresses in that range statically, but it’s a good idea to use high numbers to avoid conflicts.


Domain name system (or service or server), is an internet service that translates domain names into IP addresses. Because domain names are alphabetic, they’re easier to remember. The internet however, is really based on IP addresses. Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address. For example, the domain name translates to The DNS system is, in fact, its own network. If one DNS server doesn’t know how to translate a particular domain name, it asks another one, and so on, until the correct IP address is returned.


Refers to the addresses assigned by the router your computer is connected to each time you log into the network. The IP address is how all information flows to and from your computer. Like a street address, it’s an address required for communication. The reason it’s dynamic (and not static) is because it changes each time you log on to a network (or the internet). Alternatively, a static IP address never changes for your computer.


Effective isotropic radiated power is the measure of the strength of the signal leaving a satellite antenna in a particular direction, equal to the product of the power supplied to the satellite transmit antenna and its gain in that direction.


The vertical axis (up and down) motion of pointing a satellite dish. Some satellite transceivers are auto-pointing, and transceivers using satellite constellations in low earth orbit (LEO) do not require pointing at all.


Fair access policy, pronounced as a word. Satellite connections, while always on, are not unlimited. Bandwidth is a finite resource, so the method used to provide high download bandwidth for all while preventing any one user from hogging that bandwidth is FAP.


The satellite signal strength as it falls on the earth. It can also be called a coverage map.


Internet protocol, pronounced as two separate letters. IP specifies the format of packets and the addressing scheme used on the internet. The internet combines IP with a higher-level protocol called transmission control protocol (TCP), which establishes the connection between a destination and a source. IP by itself is something like the postal system. It lets you address a package and drop it in the system, but there’s no direct link between you and the recipient. TCP/IP, on the other hand, establishes a connection between two hosts so that they can send messages back and forth for a period of time. IP addresses are in the form of a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, could be an IP address. Within a LAN, you can assign IP addresses at random as long as each one is unique; addresses which are public to the internet must be within assigned ranges in order to avoid duplication. The authorities that assign public internet addresses have designated certain ranges as never to be used on the internet. By convention, those are normally used as private addresses on a LAN. The ranges for private addresses are all addresses starting with 10 (e.g., addresses between and, and addresses between and


Indoor unit. Where used, it refers to equipment the satellite dish connects to inside of a building, such as a satellite modem.


A physical device and/or software program that delivers device-to-device or device-to-cloud connectivity. An IoT Gateway links your remote application with your server, in Ground Control’s case, via a device such as the RockBLOCK or RockREMOTE, coupled with satellite or cellular connectivity, and Cloudloop to deliver your data to your server in the format you need.


Kilobits per second. Thousands of bits that are transferred in one second. KBps represents (Upper case B) represents thousands of bytes (a byte is made up of 8 bits) in one second.


The Ka-band is primarily used for two-way consumer broadband and military networks. Ka-band dishes can be much smaller and typically range from 60cm-120cm (2′ to 4′) in diameter. Transmission power is much greater compared to the C, X or Ku-band beams. Due to the higher frequencies of this band, it can be more vulnerable to signal quality problems caused by rain fade.


Pronounced ‘kay-yoo’, the Ku-band is used typically for consumer direct-to-home access, distance learning applications, retail and enterprise connectivity. The antenna sizes, ranging from 0.7m to 2.4m, are much smaller than C-band because the higher frequency means that higher gain can be achieved with smaller antenna sizes than C-band. Networks in this band are more susceptible to rain fade, especially in tropical areas. Ku communication is the microwave range of the electromagnetic frequency from 11.7 to 12.7GHz (downlink frequencies) and 14 to 14.5GHz (uplink frequencies). An interesting note is that older and grey-market radar detector / jammers operate on the Ku-band frequency and have caused interference to disable a VSAT satellite systems.


Operating in the frequency range from 1,530 to 2.7 Ghz, the L-band has a longer wavelength, and is therefore not affected by rain fade (which can impact the Ku- and Ka- frequency bands). Indeed the main selling point of the L-band is its resilience and stability. L-band antennas are small and lightweight, so they’re particularly useful for portable and mobile use, such as military, marine, and transport applications. Inmarsat’s FleetBroadband, and the Iridium Certus service, both leverage L-band frequencies; the Cobham Sailor range uses FleetBroadband, and the RockREMOTE and MCD-Missionlink products use Iridium Certus.


(Also known as ping time.) Internet traffic travels at the speed of light – a New York to California fibre-optic connection will take 0.03 seconds (30 milliseconds) as a round trip. In reality, the overhead processes of a dozen or more routers and switches adds a bit of time, so an average connection would be about 50 to 90 milliseconds. With satellite connections, the distances are so vast that even light speed isn’t fast enough. Why? Because all stationary satellites are located 22,300 miles above the equator, so the round trip is 90,000 miles or more. The speed of light is 186,000MPH, so the time it takes for a round trip is just under 500 milliseconds (half a second).

Satellites in low earth orbit (LEO) are much closer to the earth – 200 – 1,600km (373 – 932 miles) – which lowers the latency to 40 to 50 milliseconds.


Where the orbiting geostationary satellite acts as a “router in space” and can direct traffic to other satellite dishes on the ground. This topology cuts satellite latency (ping times) in half because data doesn’t need to make two round trips to the orbiting satellite as with the more common star topology satellite network. Mesh networks can also be a combination of star and mesh where some traffic may be routed through an Earth-based NOC.


MQTT stands for Message Queuing Telemetry Transport; it is a messaging protocol (i.e. a means of passing messages between components) for the Internet of Things (IoT). It has been designed to be extremely lightweight, making it ideal for connecting remote devices with a small code footprint, and minimal network bandwidth.


This is the time required to send a signal in both directions over a particular communication link. This is the soonest that it is possible to receive an acknowledgement of a message.


A device that forwards data packets along networks. Typically, a router will have a single WAN connection (like the internet) and one or more LAN connections (such as the computers in an office). As computers on the LAN make requests from internet servers, the router forwards those requests to the internet, and then routes the response to the computer that made the request. Routers can be distinct devices that do nothing but routing, or they can be combined in a single box with other devices including modems, hubs or switches, and wireless access points.


The rotation of a VSAT satellite dish (such as the TSAT) around its centre point. Seen as a clockwise or counter-clockwise rotation when facing the front of the dish. Skew is needed to align the antenna with the polarisation of the satellite signal when the dish is not located on the same longitude as the satellite. When a dish is west of the satellite, the skew is a negative number, and from the front of the dish the left edge will be higher than the right. When the dish is east of the satellite it will have a positive skew, with the left edge lower than the right edge.


These use an Earth-based NOC (network operations centre) to route all traffic to and from the geostationary orbiting satellite to smaller VSAT dish clients. Star networks differ from mesh networks because mesh networks avoid an Earth-based NOC, and route traffic from the orbiting satellite. The obvious advantage is mesh networks’ latency (ping time) is half as much as a star network’s because mesh doesn’t need to take two round trips to the satellite in order for information to be requested and received from a client star network VSAT site. Mesh networks are also inherently more secure because data is transmitted from VSAT dish to VSAT dish.


Refers to an IP that is permanently assigned, and does change each time that you log on to a network (or the internet). It’s possible for a static IP to be a private one, meaning that a computer with that IP is invisible to other computers on the internet. That sort of static IP occurs when a computer owner chooses to set the network properties directly for a computer that would otherwise have a dynamic IP assigned by DHCP. In the satellite world, most references to static IPs mean public IPs, visible from the internet. Such IPs are desired for a number of applications, such as VPNs, or to run a server such as a web cam. When a satellite modem has a static IP, that IP can only be assigned to a single computer (an exception is the DW4020 modem, which can be ordered with up to 5 static IPs). Other computers on the network will normally be assigned private dynamic IPs by a router with DHCP server. That router/server can be an ICS compute on a DW4000 system, or a broadband router on a DW4020 or DW6000 system. A computer with a public static IP should always have good firewall software running to avoid malicious intruders. Computers that are behind a router and have private IPs, dynamic or static, are nearly immune from such intrusion.


Virtual private network, pronounced as three letters. Computers connected by dedicated wires form a ‘private network’. A VPN uses the internet or public channels and create an encrypted secure date tunnel from point to point.


Standing for very small aperture terminal, VSAT is two-way (transmit and receive) satellite dish that’s normally under three square meters in size. VSAT dishes only communicate with geostationary orbiting satellites, and they’re on the client-side of the satellite network (where the network operations centre or NOC is on the other side). Frequency bands used by VSAT dishes are C-band, Ku-band, Ka-band and X-band. A VSAT system is comprised of the reflector (dish or antenna), the transmitter (BUC), the receiver (LNB), the waveguide, and the indoor unit (IDU).


The X-band is used mainly for military communications and wideband global SATCOM (WGS) systems. With relatively few satellites in orbit in this band, there’s a wider separation between adjacent satellites, making it ideal for comms-on-the-move (COTM) applications. This band is less susceptible to rain fade than the Ku-band due to the lower frequency range, resulting in a higher performance level under adverse weather conditions. The X-band uses 7.9 to 8.4GHz for the uplink and 7.25 to 7.75GHz for the downlink. The X-band is heavily used by military organizations.

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