IMSI attach refers to the procedure used when a mobile station (MS) joins a GSM
ID: 3603169 • Letter: I
Question
IMSI attach refers to the procedure used when a mobile station (MS) joins a GSM network. Suppose that the MS has changed its location while it was powered off. The MSC and VLC needs to register the MS in the network and the location must be updated. Using message flow diagram only, show how message flow during the IMSI attach and the location update procedures? Ignore the authentication and the data encryption steps. IMSI attach refers to the procedure used when a mobile station (MS) joins a GSM network. Suppose that the MS has changed its location while it was powered off. The MSC and VLC needs to register the MS in the network and the location must be updated. Using message flow diagram only, show how message flow during the IMSI attach and the location update procedures? Ignore the authentication and the data encryption steps. IMSI attach refers to the procedure used when a mobile station (MS) joins a GSM network. Suppose that the MS has changed its location while it was powered off. The MSC and VLC needs to register the MS in the network and the location must be updated. Using message flow diagram only, show how message flow during the IMSI attach and the location update procedures? Ignore the authentication and the data encryption steps.Explanation / Answer
Absolute Radio Frequency Channel Number (ARFCN)
The designator for the physical GSM channel consisting of two associated frequencies (an uplink and a downlink ) These channels are predetermined and set by a national or international standard.
Base Station Controller (BSC)
A component of the BSS used to control 10's - 100's of BTS's
Base transceiver Station (BTS)
A component of the BSS/RAN. The BTS is also known as the tower and deals directly with the MS trough the air interface.
Frequency Division Multiple Access (FDMA)
An access scheme where the assigned frequency band for a network is divided into sub-bands (frequencies) which are allocated to a subscriber for the duration of their calls.
Home Location Register (HLR)
The component of the NSS that stores permanent subscriber data as well as the subscriber's current LA. Typically, one logical HLR exists per PLMN.
Location Area Identity (LAI)
Used in GSM to identify an area. It consists of a MCC, MNC, and a LAC.
Mobile Switching Center (MSC)
The component of the network architecture that is responsible for an entire LAC or SID/NID and is known as the "brain" because it is responsible for the most of the interaction between the network snd the subscriber.
Public Land Mobile Network (PLMN)
(The name of a network, consisting of the MCC and MNC.) some network providers are so large they require more than one PLMN but typically one PLMN exists per provider.
Time Division Multiple Access (TDMA)
A channel access method for shared radio networks. It allows several users to share the same ARFCN by dividing the signal onto different time slots.
Visitor Location Register (VLR)
A temporary database used in GSM and CDMA that holds information about all users who are registered within the MSC it serves. (It holds such information as the IMSI, IMEI, MIN, MEID and HLR address. For GSM, it produces both the TMSI and MSRN.)
The path of radio signal
Simple (tends to ravel in strait line) Complex ( Because of what happens between the transmitting antenna and the recipe antenna.
Radio waves
Radio waves travel a the speed of light also fade away over distance they can reflected off, refracted through, diffracted around, and absorbed by a surface.
Reflection
when a signal hits an object it bounces off and continues straight on.
Refraction
The bending of the light that takes place at a boundary between two mediums due to a change in the speed of lights it passes from one medium to another.
Diffraction
Signal passes an edge of an object it will bend around it.
Absorption
When radio wave hits an object, some of its energy may be absorbed.
Path loss
When signal will eventually fade away to nothing, or a least to a signal too weak to used naturally.
Multiple paths
When the signal hits many obstacle along the path. Multi path is destructive to a signal.
Interference
Three type of man-made interference: Co-channel, Adjacent channel, and Inter-moculation.
Co-Channel
When the receiving device receives the same frequency from two different sources.
Adjacent Channel
When two frequencies are close together. This can combine the signals to cause noise and make it difficult for the receiver to filter out its intended channel.
Inter-modulation
This is produced by mixing together several signals. Could be any number of different types of signals and frequency ranges transmitted from the same location.
Ducting
Natural occurrence when the air temperature is much different at ground level compared to he air temperature at a higher altitude.
Link Budget
Accounting of the gains and losses from the transmitter
Effective Radiated Power (ERP)
Actual power, in watts, coming out the transmit antenna.
Decibles
Convenient way to measure power
Received Signal Strength Indicator (RSSI)
Signal strength RSSI value is simply how our tools display the measured power and is displayed in Dbms.
Two Types of path loss
Free space, and Non-free space
Free space
there is nothing affecting the signal
Non-free space
Involves propagation factors such as multi-path and absorption
PLMN components
Mobiles Subscriber (MS), Base station Subsystem (BSS), Network switching Subsystem (NSS).
Network Switching Subsystem (NSS) consist of 10 components
HLR, AuC, EIR, ABC, MSC, VLR, OMC, SMSC, CBS, and GMSC.
Base station Subsystem (BSS) consist of two components
Base station controller (BSC), Base Transceiver Station (BTS)
Mobile Subscriber (MS) component two separate entities
Mobile Equipment (ME), and Subscriber Identity Module (SIM).
Home location Register (HLR)
Permanent database for the network
Mobile subscriber integrated service digital network (MSISDN)
phone number located in the SIM
Mobile subscriber roaming number (MSRN)
When the subscriber roam into another network
Authentication Center (AuC)
Initiates the validation process of a GSM subscriber
Triples
Signed Responses (SRES), Session Key (Kc) Random number (RAND).
Equipment Identity register (EIR)
Checks the IME international mobile equipment against White grey black list.
Administration and Billing Center (ABC)
Ensures everyone gets charge and paid accordingly
Cell Broadcast service (CBS)
Responsible to handle point to area and point to many types of traffic example weather alerts vehicle accidents
Short Message Service Center (SMSC)
responsible to routing subscribers text message traffic. normally store 24 hr
Location area code (LAC)
Geographical area on the surface of the earth identified by a number (code) consisting of up to 5 digits
Mobile Switching Center (MSC)
Responsible for all the activity within the LAC, Registrations, location updates paging, MS handoffs, call setup and call tear - down. Brain of the network.
Visitor location network (VLR)
temporary database for every handset register in the LAC. It has both permanent and temporary information and follow the subscriber when they change LAC, Generate the TMSI also store the triplets.
Operational and Maintenance Center (OMC)
responsible to send personnel for repairs
Gateway MSC (GMSC)
normal MSC but additional duty routes traffic outside the network.
Base Station Subsystem (BSS)
Two components (BSC and BTS)
Base Station Controller (BSC)
Controls numerous BTS and talks to MSC some of the functions are radio resource allocation frequency
Base Transceiver Station (BTS)
The tower communicates with the GSM handset process the signal sent from the handset to the network.
Global Cell Identifier (GCI)
Grid coordinate take you to specific sector.
Types of BTS
Macro - large, Macro - smalls, Micros, Pico, Femto.
Types of Sectoring
Omni, Bi-Sectored, Tri-Sectored.
Cluster
Applies to the design utilized by an engineer to lay out this frequency re-use.
The MS
Mobile equipment and Subscriber Identity Module.
Mobile Equipment (ME)
Actually a radio and more
IMEI
15 digits first 8 TAC type allocation code next 6 serial number SN and the last digit is check digit CD.
To get the IMEI
*#06#
IMSI International mobile subscriber
another 15 digit associated with a handset and individual subscriber. first 5-6 are the PLMN MCC 3 digits MNC can either be 2-3 the remain digits either 9 -10 are the mobile subscriber identification number (MSIN) just the SIM serial number.
SIM stored these data
IMSI
Ki
Kc
LAI
A3 and A8 algorithms
A5x encryption
Barred roaming list (BRL)
SMS messages
Last 10 numbers dialed and received
phone book
Operator specific emergency number
Value added service application (APPS)