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Update for 16-01-22 16:45

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Tyler Perkins 2022-01-16 16:45:01 -05:00
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tech/GSM.wiki
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@ -3,6 +3,24 @@
GSM or the global system for mobile communications is a standard developed to
standardize cellphones and their communication and infrastructure.
GSM handsets derive the baudrate from very very accurate clocks on the base
station.
== Bands ==
GSM occupies
* 850 (USA)
* 900 (europe)
* 1800 (europe)
* 1900 (USA)
*NOTE* GSM-900 uses 880-914mhz
The 33cm ham band is 902-928mhz. Therefore, for 902-914 we can transmit legally
as a eurpean tower.
This band is also the ISM (industrial scientific medical) band. Most devices on
this band are low power and low utilisation.
== IMSI ==
International Mobile Subscriber Identity is a way for devices to id themselves
@ -12,3 +30,6 @@ on a GSM network. An IMSI is a secret key that is stored on the SIM card.
A spoofed GSM tower. In GSM the base station (tower) picks all settings
including Tx power, Rx gain, encryption, etc
When the tower tells the handset to disable encryption (A5/0), and handset
_should_ tell user about this. Hoever every manufacturer disables this