Explain GSM and Mobility.
GSM (Globle System For Mobile Communications) :
Time Division Multiple Access(TDMA) : a digital wireless telephony transmission technique. TDMA allocates each user a different time slot on a given frequency. TDMA divides each cellular channel into three time slot in order to increse the amount of data that can be carried.
CDMA does not assign a specific frequency to each user. instead, every channel uses the full available spectrum. Ex. 3G
The GSM network has four separate parts that work together to function as a whole:
1. The mobile device itself
2. The base station subsystem(BSS)
3. The network switching subsystem(NSS)
4. The operation and support subsystem(OSS)
The mobile device connects to the network via hardware.
The subscriber identity module(SIM) card provides the network with identifying information about the mobile user.
Mobility :
1) User Mobility
User should be able to move from one physical location to another location and use the same service.
Example: User moves from london to new york and uses the internet in either place to access the corporate application.
2) Network Mobility
user should be able to move from one network to another network and use the same service.
Example: User moves from hong kong to singapore and uses the same GSM phone to access the corporate application.
3) Bearer Mobility
User should be able to move from one bearer to another while using the same service.
Example: User is unable to access the WAP bearer due to some problem in the GSM network then he should be able to use voice or SMS bearer to access that same corporate application.
4) Device Mobility
User should be able to move from one device to another and use the same service.
Example: User is using a PC to do his work. During the day, While he is on the street he would like to use his mobile to access the corporate application.
5) Session Mobility
A user session should be able to move from one user-agent environment to another.
Example: An unfinished session moving from a mobile device to a desktop computer is a good example.
6) Service Mobility
User should be able to move from one service to another.
Example: User is writing a mail. Suddenly,he needs to refer to something else. In a PC, user simply opens another service and move between them. User should be able to do the same in small wireless devices.
7) Host Mobility
User should be able to move while the device is a host computer.
Example: The laptop computer of a user is a host for grid computing network. it is connected to a LAN port. Suddenly,the user realize that he needs to leave for an offsite meeting. he disconnects from the LAN and should get connected to wireless LAN while his laptop being the host for grid computing network.
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