Draw the system architecture of GSM and explain the functionality of HLR and VLR. Why is the cell structure supposed to be a hexagon in a mobile network?
<strong">GSM architecture:
The GSM network can be divided into five main groups:
1) Mobile station(MS): It include mobile equipment(ME) and the subscriber identity module(SIM)
2)Base station subsystem(BSS): It include Base transceiver station(BTS) and the base station controller(BSC)
3) The network and switching subsystem(NSS): it consists of VLR and HLR.
4) The operation and support subsystem(OSS)
The functionality of HLR(home location register): it is a central database. It contains the following information:
1)each mobile phone subscriber that is authorized to use the GSM core network
2)every SIM card issued by the mobile phone operator.
3)GSM services that the subscriber has requested or given.
4)Current location of subscriber.
5)Call divert settings applicable for each associated MSISDN.
6)Manage the mobility of subscriber by means of updating their position is administrative areas called location areas, which are identified with a LAC.
The functionality of visitor location register(VLR):
1)to inform the HLR that a particular subscriber has arrived in the particular area covered by the VLR.
2)To track where the subscriber is within the VLR area when no call is ongoing.
3)To allow or disallow which services the subscriber may use.
4)To allocate roaming numbers during the processing of incoming calls.
5)To delete the subscriber record when a subscriber explicitly moves to another, as instructed by the HLR.
The size of the cell is selected to be hexagon in mobile network because:
1) The frequency reuse become possible using this shape.
2) The radiation pattern of the antennas used is60 degree which means6 are required for the full360 degrees coverage which is the same no. of sides the hexagon consists.
3) Frequency are emitted in circular way which makes the square, rectangle or a triangle unsuitable shapes for the cell while if we use a circular shape for the cell there will be gaps between cells.
Write short note on Call setup of GSM network for mobile-to-mobile call.
What is multiple access technique? Do a comparative study among FDMA,TDMA and CDMA.
What are hidden station problem and exposed station problem in WLAN? How are the problems solved?
Write a C program to manage array operation using switch case.
Distinguish between Decision table versus decision tree
