Gsm Architecture Flashcards
Expand GSM
Global system for mobile communications
What is the gsm mobile phone know as ?
Mobile station or ms
What two elements does a mobile station (MS) have ?
The mobile equipment (ME)
Subscriber Identity Module (SIM)
What is the air interface ?
It is the radio frequency link between the mobile station and the tower
What information can a sim contain ?
Phone book Imsi Tmsi Authentication and encryption keys Services available Msisdn
Expand MSISDN
Mobile station interested services digital network number
Expand IMSI
International mobile subscriber identification
Expand TMSI
Temporary mobile subscriber identification
Expand IMEI
International mobile equipment identification
What is the msisdn ?
Mobile stations phone number
How many digits is the msisdn made up of ?
A maximum of 15 digits
How is a msisdn broken down ?
First 2 digits = country code
Next 3 digits = the national destination code
Remaining digits = unique serial number
Expand NDC
National destination code
Expand PLMN
Public land mobile network
What is the national destination code identifying?
Which public land mobile network the ms is associated with
O2 or EE
Expand SNR
Unique serial number
How is a international mobile subscriber identity broken down ?
First 3 digits = mobile country code
Next 2 digits = mobile network code
Remaining digits = operator specific
Expand MCC
Mobile country code
Expand MNC
Mobile network code
What identity is the most commonly sent between the MS and the network
True tmsi or temporary Mobile subscriber identity
How is a tmsi generated ?
It is a randomly allocated hexadecimal number that is given to the ms after initial authentication
Why effects the tmsi ? When is it updated?
Each time the mobile moves to a new geographical area
How can the network use a tmsi
As a security feature, to ensure the subscribers identity remains secure and is not tracked while accessing the network
Where is international mobile subscriber or imsi held ?
On the SIM card
What is associated with the imsi
All subscriber related information like billing
Expand imei
International mobile equipment identity
What could a imei also be known as ?
Eir or equipment identity register
How is a imei broken down ?
First 8 digits = type allocation code (tac).
Next 6 digits = serial number
Last digit = check digit
How is the type allocation (tac) broken down ?
First 2 digits = reporting body identifier
Next 6 = mobile equipment type identifier
Expand SNR and what is it used for ?
Serial number
Used to uniquely identify each individual mobile equipment
What is the purpose of a check digit
To help guard against incorrect entries into the equipment identity register
When is the imei broadcast ?
Powering on the mobile station
Change of SIM card
Expand BTS
Base transceiver station
What role does the Bts play ?
What will it typically have ?
It is responsible for the radio functions associated with connection to and from the ms
Several transceivers
What is bts commonly referred to as ?
Mobile phone Mast
What functions does a bts provide ?
Radio frequency carriers Modulation and demodulation of rf carriers Data processing Error coding Ciphering Channel mapping
What is the link between the mobile station and base transceiver station know as ?
Um or air interface and is an encrypted radio frequency link
What are the most common antenna types used in gsm ?
Macro - range < 35km
Micro - range < 5 km
Pico - around a hundred meters
Micro wave radio relay - link bts to other bts
