LWIS.net Angelia   Expert of Satellite Broadband Technologies



Satellite Broadband Indoor Units (IDU)


An IDU, or In-Door Unit, is a telecommunication device that is used in satellite Internet service to receive and decode satellite transmissions. An IDU is a box that connects to the user’s router and contains a built-in satellite receiver that may also be connected to a satellite dish on the roof or exterior wall of the user’s home. An IDU is responsible for receiving the satellite signals broadcasted by the user’s satellite service provider and decoding them in order to provide the user with satellite Internet access.

When a satellite provider broadcasts a transmission, that data is received by a satellite in Earth’s orbit and retransmitted to a specific area on the Earth’s surface. Any satellite dish in that area that is setup to receive that transmission’s frequencies can then receive the transmission and convert it into electrical impulses that are sent to the user’s IDU. The IDU can then convert the information into digital data and pass it through the user’s modem and/or router in order to provide the user with Internet access.

IDUs are advantageous because they sit near the user’s end and provide Internet access without being exposed to the open environment. IDUs are relatively easy to operate and can provide the user with services such as Channel Guide and On Demand. IDUs are also lightweight and do not usually need to be directly operated in order to provide services to the user.

Many people appreciate having IDUs because of the ease in operations and the hassle-free installation. It is typically connected near the computer router and does not take too much space. Operating it is also made simple and easy making navigation of the internet smooth and hassle-free. With IDUs installed in homes and offices, these devices are also equipped with internal testing functionality to ensure that they are functioning well.

Along with ongoing enhancements in satellite internet technology, some companies have also made enhancements to their indoor units or IDUs. Some of these units not only receive and decode satellite signals but also provide added features like pay-per-view options. There are also some who configured IDUs to receive transmissions and signals from other satellites which is typically illegal in nature. Despite this concern though, the use of satellite-based television and internet service is growing more and more popular in the US and in many industrialized and developing countries around the world.


Applications of Satellite Indoor Units


An IDU is used solely for the purpose of receiving and converting satellite transmissions into usable data for television service and Internet access. While IDUs have been modified in the past to provide users with additional services, such as Pay-Per-View channels or non-related satellite-based transmissions, this is often illegal and may result in loss of the user’s regular services if the IDU becomes damaged.

Depending upon the specific usage circumstances, we may classify the applications into several categories, where there are noticable differences of technological requirements and other application conditions, such as:

  • Military
  • Government
  • Commercial and
  • Residential/Personal/Professional (this project).

We will currently focus on the last application case.


Components of Satellite Indoor Units

IDU consists of MUX/DEMUX, Satellite modem (modulator-demodulator), EDU (Encryption decryption Unit) and subscriber interfacing part.


It is used to provide multiplexing of voice channels and data channels at the transmit end while demultiplexing at the receive end.

• Satellite Modem:

It consists of modulator at transmit end and demodulator at receive end. Modulator does modulation of baseband information (voice/data) at IF (either 70+/-18 MHz or 140+/-18 MHz). Modulator generated modulated IF frequency. Demodulator does the reverse operation i.e. demodulation of modulated IF to retrieve baseband information.

• Baseband interface:

This is voice and data connectivity. Usually voice can be a subscriber line or exchange connection with 2W E&M or 4W E&M etc. configurations.


Satellite Modem


What is a Modem?

The word modem means modulator or demodulator. Satellite modems transform and receive an input bit stream to a radio signal. However, some satellite modem devices only have a demodulator that is used to access satellite Internet, whereas data is transferred in other directions via the use of a conventional PSTN model or an ADSL modem.

How Do Satellite Modems Work?

Satellite modems are often used by consumers who reside in rural areas and are not within close proximity of a phone company or DSL company and desire broadband access. Internet service provided via satellite is not connected through telephone lines or cable systems. In contrast, a satellite dish is used for two-way (upload/download) data exchanges. The upload speed via a satellite dish is approximately one-tenth of the 500 kbps download speed. Consumers with DSL and cable connections benefit from having higher download speeds in comparison to satellite. However, satellite connections are approximately ten times faster in operation than a normal modem.

When installing a satellite modem, there must be a clear view to the south. This is a necessary requirement because the orbiting satellites are located over the equator region. Heavy rains and tall trees affect the reception of both Internet signals and satellite TV signals. Two-way satellite Internet modems work by using Internet Protocol (IP) multicasting technology. Approximately 5,000 channels of data exchange can concurrently be supplied by one solitary satellite. Data is sent in a compressed format from one point to numerous other points, simultaneously, through IP multicasting. Compressing the data decreases the data size and the bandwidth. Regular land-based, dial-up global systems are limited and prevent multicasting on this scale. However there are some satellite services that necessitate a consumer to have either a cable modem connection or a dial-up connection to facilitate the data sent to the Internet. The satellite transmits data to the computer through the same satellite dish connection that facilitates pay-per-view television programming.


Satellite Broadband Routers


What’s a router? Basically, if you have multiple devices trying to access the Internet, a router can handle all of the various requests and direct each device in the right direction.

Unless you only have one computer and it’s in the same room as your modem, chances are you may be interested in using a router. A router allows a satellite Internet connection to be shared by multiple computers. Your router turns your internet connection into your home network. Your wireless router allows you to connect several computers to a single network without the need for an Ethernet cable connection. It also allows for mobile connections within the signal range. If you want a wireless network, make sure your router has Wi-Fi capability. Often your modem will contain a built-in router so you don’t need to worry about another piece of equipment.

More information.