Iridium

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Iridium
IridiumTDMA.png
Frequencies 1616 MHzMegaHertz (MHz) 10^6 Hz1,616,000,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
1,616,000 kHzKiloHertz (kHz) 10^3 Hz
,1626.5 MHzMegaHertz (MHz) 10^6 Hz1,626,500,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
1,626,500 kHzKiloHertz (kHz) 10^3 Hz
1,616,000 kHzKiloHertz (kHz) 10^3 Hz
1,616 MHzMegaHertz (MHz) 10^6 Hz
1,626,500 kHzKiloHertz (kHz) 10^3 Hz
1,626.5 MHzMegaHertz (MHz) 10^6 Hz
Frequency Range 1,616 MHzMegaHertz (MHz) 10^6 Hz1,616,000,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
1,616,000 kHzKiloHertz (kHz) 10^3 Hz
- 1,626.5 MHzMegaHertz (MHz) 10^6 Hz1,626,500,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
1,626,500 kHzKiloHertz (kHz) 10^3 Hz
Mode RAW
Modulation PSKPhase-Shift Keying
ACF
Bandwidth 31.5 kHzKiloHertz (kHz) 10^3 Hz31,500 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
0.0315 MHzMegaHertz (MHz) 10^6 Hz
31.5 kHzKiloHertz (kHz) 10^3 Hz
0.0315 MHzMegaHertz (MHz) 10^6 Hz
31.5 kHzKiloHertz (kHz) 10^3 Hz
0.0315 MHzMegaHertz (MHz) 10^6 Hz
Location Worldwide
Short Description This is the L-band uplink/downlink for the Low Earth Orbit Iridium Satellite Constellation. This system is used for satellite based phone calls.
I/Q Raw Recording
Audio Sample

This is the L-band uplink/downlink for the Low Earth Orbit Iridium Satellite Constellation. This system is used for satellite based phone calls.


Characteristics[edit]

Iridium uses Differentially Encoded QPSKQuadrature Phase-Shift Keying (2 bits per symbol) (DEQPSK) with an occupied bandwidth of 31.5 kHzKiloHertz (kHz) 10^3 Hz. Each channel is spaced 41.667 kHzKiloHertz (kHz) 10^3 Hz from each other as this is the minimum bandwidth needed for receivers to properly receive Iridium signals. Iridium uses both TDMATime Division Multiple Access and FDMAFrequency Division Multiple Access in its transmissions.

The transmitter duty cycle allows for bursted transmission every 8.28 msmilliseconds (.001 of a second) out of 90 msmilliseconds (.001 of a second), or 9.2%, at a rate of 50 kbpsKilobits per second (kbps), with a symbol rate of 25000 bdBaud (unit symbol Bd) is the unit for symbol rate or modulation rate in symbols per second..

For the voice communications, Iridium uses a 2.4 kbpsKilobits per second (kbps) Advanced Multi-Band Excitation (AMBE) vocoder developed by Digital Voice System Inc. (DVSI). This vocoder is tailored to the Iridium communication channel.


Samples[edit]

Iridium TDMATime Division Multiple Access (Sample scaled down from 100kHz to 10 kHzKiloHertz (kHz) 10^3 Hz scale for listening purposes):

Frequencies[edit]

The subscriber links are in L-band between 1616 MHzMegaHertz (MHz) 10^6 Hz and 1626.5 MHzMegaHertz (MHz) 10^6 Hz. There are 240 main channels between 1616 MHzMegaHertz (MHz) 10^6 Hz and 1626 MHzMegaHertz (MHz) 10^6 Hz. These are spaced 41.667 kHzKiloHertz (kHz) 10^3 Hz from each other. The center frequency of each channel can be calculated by 1616 + 0.020833(2n - 1) MHzMegaHertz (MHz) 10^6 Hz where (n = 1, ..., 240).

In addition, A 12-frequency access band is reserved for the simplex (ring alert and messaging) channels. These channels are located in a globally allocated 500 kHzKiloHertz (kHz) 10^3 Hz band between 1626.0 MHzMegaHertz (MHz) 10^6 Hz and 1626.5 MHzMegaHertz (MHz) 10^6 Hz. They are:

Channel Number Center Frequency Allocation
1 1626.020833 MHzMegaHertz (MHz) 10^6 Hz Guard Channel
2 1626.062500 MHzMegaHertz (MHz) 10^6 Hz Guard Channel
3 1626.104167 MHzMegaHertz (MHz) 10^6 Hz Quaternary Messaging
4 1626.145833 MHzMegaHertz (MHz) 10^6 Hz Tertiary Messaging
5 1626.187500 MHzMegaHertz (MHz) 10^6 Hz Guard Channel
6 1626.229167 MHzMegaHertz (MHz) 10^6 Hz Guard Channel
7 1626.270833 MHzMegaHertz (MHz) 10^6 Hz Ring Alert
8 1626.312500 MHzMegaHertz (MHz) 10^6 Hz Guard Channel
9 1626.354167 MHzMegaHertz (MHz) 10^6 Hz Guard Channel
10 1626.395833 MHzMegaHertz (MHz) 10^6 Hz Secondary Messaging
11 1626.437500 MHzMegaHertz (MHz) 10^6 Hz Primary Messaging
12 1626.479167 MHzMegaHertz (MHz) 10^6 Hz Guard Channel

Decoding Software[edit]

Hobby Level Software

Video Examples[edit]

Additional Links[edit]

Additional Images[edit]