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.


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.



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