The main function of NSS is to connect wireless network with standard wired network such as PSTN. PSTN is called as Public Switched Telephone Network with a collection of interconnected voice-oriented public telephone networks. NSS contains the switches and mobility database to provide the switching function and save the subscriber information used in the mobility management respectively.
A. Mobile Switching Network (MSC):
MSC is used to connect base stations to the Public Switched Telephone Network (PSTN) or other MSC and to provide switching function. Thus MSC is used to provide basic switching function using digital ISDN switch and used to connect the wireless network with wired network.
It uses A interface to connect BSC to the wired network. To provide wireless service to large number of users and cover large geographic area, MSC provide switching services to several BSCs.
The MSC uses additional connections used to connect the MSC to other networks such as PSTN and/or ISDN is called as Gateway MSC (GMSC).
It is used to connect the radio network with the fixed network (i.e. wired networks such as PSTN and ISDN).
MSC handles all the signals that are used to set up the connection, to release a connection and to do a handover to the other MSC. It uses Signalling System 7 (SS7) to handle all the signals.
MSC is also used to provide the supplementary services such as call forwarding, multi=party call and billing etc.
B. Mobility Database:
The NSS contains various mobility databases used to store and maintain the information of the subscriber such as personal information, location information and various services offered to the subscriber.
The mobility databases are earned by the service provider. The information stored in them is updated and maintained by the service providers.
The mobility databases are used to provide the services to the subscribers registered with their service. To get the network services continuously the MS periodically registers its current location to the system.
The MSC communicates with mobility database to get the current location of the MS to forward the call or SMS to the particular BS.
The mobility databases are also used in roaming management. The mobility databases contain the following databases.
Home Location Register (HLR): HLR is a permanent database maintain by each network service provider which is used to store information of all mobile subscribers registered with the network. Its database contains IMSI, IMSISDN, prepaid/post-paid, roaming restrictions, supplementary services
Visitor Location Registers (VLR): It is a temporary database which updates whenever new MS enters its area by HLR database.It controls mobiles roaming in its area. It reduces number of queries to HLR.Its database contains IMSI, TMSI, IMSISDN, MSRN, location, area authentication key.
Authentication Centre (AUC): It provides protection against intruders in air interface. It is used to protect the identity of the user as well as protect the data transmitted through the air. It handles authentication and encryption of each subscriber in HLR and VLR. It maintains authentication keys and algorithms and provides security triplets (RAND, SRES, and Ki). AUC is normally present in secured part of HLR. It consists of EIR (Equipment Identity Register) to check for stolen phones.
and 3 others joined a min ago.
teamques10
★ 67k