GSM Exam Unit 1 Questions & Answers 2024/2025
What is the Global System for Mobile Communications (GSM) - ANSWERS- GSM was designed as a circuit‐switched system that establishes a direct and exclusive connection between two users on every interface between all network nodes of the system
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What is the Global System for Mobile Communications (GSM) - ANSWERS- GSM was designed as a
circuit‐switched system that establishes a direct and exclusive connection between two users on every
interface between all network nodes of the system
- Similar way to fixed‐line phone networks
- GSM is used worldwide by billions of people today.
- A large percentage of mobile voice calls are still handled by GSM
How has the GSM Changed? - ANSWERS- This physical circuit switching has been virtualized and many
network nodes are connected over IP‐based broadband connections today
What happens at the beginning of a call? - ANSWERS- The network establishes a direct connection
between two parties, which is then used exclusively for this conversation
- The switching center uses a switching matrix to connect any originating party to any destination party.
- Once the connection has been established, the conversation is then transparently transmitted via the
switching matrix between the two parties.
- The switching center only becomes active again to clear the connection in the switching matrix if one of
the parties wants to end the call.
- This approach is identical in both mobile and fixed ‐line networks
,What is a Switch matrix systems - ANSWERStypically used in medium- to high-density switching of
multiple channels where any row can be connected to any column, making them ideal for routing
multiple signals between instruments and the device under test.
What is a Switch Center (MSC) Mobile switch center - ANSWERSis the centerpiece of a network switching
subsystem (NSS). The MSC is mostly associated with communications switching functions, such as call
set-up, release, and routing
How did Early fixed‐line telecommunication networks function - ANSWERS- Early fixed ‐line
telecommunication networks were designed only for voice communication, for which an analog
connection between the par- ties was established.
- In the mid‐1980s, analog technology was superseded by digital technology in the switching center.
- Which means that calls were no longer sent over an analog line from the originator to the terminator.
- Instead, the switching center digitized the analog signal that it received from the subscribers, which
were directly attached to it, and forwarded the digitized signal to the terminating switching center
Analog vs Digital Signals - ANSWERS- Digital signals can convey information with less noise, distortion,
and interference.
- Digital circuits can be reproduced easily in mass quantities at comparatively low costs.
- Digital signal processing is more flexible because DSP operations can be altered using digitally
programmable systems.
Define the ISDN (Integrated Services Digital Network) Line - ANSWERS- With this system, the
transmission became fully digital and the conversion back to an analog audio signal was done directly in
the phone
- provides high-speed, high-bandwidth channels to every subscribers on the public switched telephone
network, achieving end-to-end digital functions with standard equipment interface devices
,How do subscribers interact in a GSM? - ANSWERS- The subscribers are mobile and can change their
location at any time.
- Thus, it is not possible to use the same input and output in the switching matrix for a user for each call
as is the case in fixed‐line networks
How can a switch predict where the call should be forwarded to for a certain subscriber? - ANSWERS- As
a mobile network consists of many switching centers, with each covering a certain geographical area, it is
not even possible to predict in advance which switching center a call should be forwarded to for a
certain subscriber.
- This means that the software for subscriber management and routing of calls of fixed ‐line networks
cannot be used for GSM
- Instead of a static call‐routing mechanism, a flexible mobility management architecture in the core
network became necessary, which needed to be aware of the current location of the subscriber and thus
able to route calls to them at any time.
What happens if the subscriber leaves a coverage area? - ANSWERS- It was also necessary to be able to
flexibly change the routing of an ongoing call as a subscriber can roam freely and thus might leave the
coverage area of the radio transmitter of the network over which the call was established.
What is the Mobile Switching Center (MSC) - ANSWERS- The hardware as well as the lower layers of the
software which are responsible, for example, for the handling of the switching matrix were mostly
identical.
Define Internet Protocol (IP) - ANSWERS- a set of rules governing the format of data sent over the
internet or other network.
- Services, such as voice calls, e‐mail, instant messaging (IM), social networks (e.g. Facebook), blogs,
wikis, share the Internet Protocol (IP) as a transport protocol and globally connect people via the
Internet.
, Difference between circuit switching and the Internet? - ANSWERS- While circuit switching establishes an
exclusive channel between two parties
- The Internet is based on transferring individual data packets
How are IP packets transferred on a network? - ANSWERS- A link with a high bandwidth is used to
transfer the packets of many users.
- By using the destination address contained in each packet, each network node that the packet traverses
decides over which outgoing link to forward the packet.
How did network operators deal with the rise of the Internet and IP ‐based applications? - ANSWERS-
Due to the rise of the Internet and IP‐based applications, network operators thus had to maintain two
separate networks:
1. A circuit‐switched network for voice calls
2. A packet‐switched network for Internet‐based services.
Why was the switching matrix in the MSC replaced with the media gateway device? - ANSWERS- As the
simultaneous operation of two different networks is very inefficient and costly, most network operators
have
Benefits of this replacement to the Media Gateway (MG)? - ANSWERS- This allows them to virtualize
circuit switching and to transfer voice calls over IP packet
- The physical presence of a circuit‐ switched infrastructure is thus no longer necessary and the network
operator can concentrate on maintaining and expanding a single IP ‐based network
- This approach has been standardized under the name 'Bearer ‐Independent Core Network' (BICN), used
for supporting narrowband Integrated Services Digital Network (ISDN) service over a broadband
backbone network
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