GSM Subsystems - Network. Subsystem. The Network Subsystem is in affect the Mobile. Switching Center. The central part of the network. The MSC provides. GSM uses narrowband Time Division Multiple Access (TDMA) for providing voice and text based services over mobile phone networks. Audience. This tutorial. Geographical structures in a GSM network. 2. Methods of network GSM is a world-wide standard for mobile communication with an extensive coverage. Due to.
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GSM Architecture. Numbering and Routing. GSM Services. GSM Network Architecture. Engr. Mian Shahzad Iqbal. Lecturer. Department of Telecommunication. GSM Network Structure: Concept. NSS. Network Switching. Subsystem. Control/ switching of mobile services. BSS. Base Station. Subsystem radio access. BSS. ever, one should be careful in differentiating some of the implementation specifics unique to the GSM network architecture and application from the func-.
The BTS is the defining element for each cell. The BTS communicates with the mobiles and the interface between the two is known as the Um interface with its associated protocols. It manages the radio resources and controls items such as handover within the group of BTSs, allocates channels and the like.
It communicates with the BTSs over what is termed the Abis interface.
The base station subsystem element of the GSM network utilised the radio access technology to enable a number of users to access the system concurrently. Each channel supported up to eight users and by enabling a base station to have several channels, a large number of subscribers could be accommodated by each base station.
GSM Seminar and PPT with pdf report
Base stations are carefully located by the network provider to enable complete coverage of an area. The area being covered bay a base station often being referred to as a cell.
As it is not possible to prevent overlap of the signals into the adjacent cells, channels used in one cell are not used in the next. In this way interference which would reduce call quality is reduced whilst still maintaining sufficient frequency re-use. A variety of technologies were used to achieve this. As more data was required with increasing usage of the GSM network, and also as other cellular technologies like 3G became more widespread, many links used carrier grade Ethernet.
GSM – Architecture, Features & Working
Often remote BTSs were linked using small microwave links as this could reduce the need for the installation of specific lines if none were available. As base stations often needed to be located to provide good coverage rather than in areas where lines could be installed, the microwave link option provided an attractive method for providing a data link for the network.
Mobile station Mobile stations MS , mobile equipment ME or as they are most widely known, cell or mobile phones are the section of a GSM cellular network that the user sees and operates. In recent years their size has fallen dramatically while the level of functionality has greatly increased. A further advantage is that the time between charges has significantly increased. Cell horizontal radius varies depending on antenna height, antenna gain, and propagation conditions from a couple of hundred meters to several tens of kilometers.
There are also several implementations of the concept of an extended cell,  where the cell radius could be double or even more, depending on the antenna system, the type of terrain, and the timing advance.
Indoor coverage is also supported by GSM and may be achieved by using an indoor picocell base station, or an indoor repeater with distributed indoor antennas fed through power splitters, to deliver the radio signals from an antenna outdoors to the separate indoor distributed antenna system.
These are typically deployed when significant call capacity is needed indoors, like in shopping centers or airports. However, this is not a prerequisite, since indoor coverage is also provided by in-building penetration of the radio signals from any nearby cell.
Regardless of the frequency selected by an operator, it is divided into timeslots for individual phones. This allows eight full-rate or sixteen half-rate speech channels per radio frequency.
GSM network architecture elements
These eight radio timeslots or burst periods are grouped into a TDMA frame. Half-rate channels use alternate frames in the same timeslot. The channel data rate for all 8 channels is Voice codecs[ edit ] GSM has used a variety of voice codecs to squeeze 3.
Originally, two codecs, named after the types of data channel they were allocated, were used, called Half Rate 6. It also provides an interface to the PSTN so that calls can be routed from the mobile network to a phone connected to a landline.
Interfaces to other MSCs are provided to enable calls to be made to mobiles on different networks.
When a user switches on their phone, the phone registers with the network and from this it is possible to determine which BTS it communicates with so that incoming calls can be routed appropriately. Even when the phone is not active but switched on it re-registers periodically to ensure that the network HLR is aware of its latest position.
There is one HLR per network, although it may be distributed across various sub-centres to for operational reasons. The VLR can be implemented as a separate entity, but it is commonly realised as an integral part of the MSC, rather than a separate entity. In this way access is made faster and more convenient.
Each mobile equipment has a number known as the International Mobile Equipment Identity.
This number, as mentioned above, is installed in the equipment and is checked by the network during registration. Dependent upon the information held in the EIR, the mobile may be allocated one of three states - allowed onto the network, barred access, or monitored in case its problems.
It is used for authentication and for ciphering on the radio channel. The two gateways handle messages directed in different directions. These entities were the main ones used within the GSM network.
They were typically co-located, but often the overall core network was distributed around the country where the network was located. This gave some resilience in case of failure.
Performance Enhancements in a Frequency Hopping GSM Network
Although the GSM system was essential a voice system, the core network was a data network as all signals were handled digitally. The BTS is the defining element for each cell.This gave some resilience in case of failure. Finally, with the development of UMTS , EFR was refactored into a variable-rate codec called AMR-Narrowband , which is high quality and robust against interference when used on full-rate channels, or less robust but still relatively high quality when used in good radio conditions on half-rate channel.
A base station antenna carrying 2G GSM signals GSM network architecture elements In order that the GSM system operates together as a complete system, the overall network architecture brings together a series of data network identities, each with several elements. Even when the phone is not active but switched on it re-registers periodically to ensure that the network HLR is aware of its latest position. Indoor coverage is also supported by GSM and may be achieved by using an indoor picocell base station, or an indoor repeater with distributed indoor antennas fed through power splitters, to deliver the radio signals from an antenna outdoors to the separate indoor distributed antenna system.
As the GSM system was all digital, the network was a data network. Micro cells are cells whose antenna height is under average rooftop level; they are typically used in urban areas. The second aspect is that of security alert which is achieved in a way that on the detection of intrusion, the system allows automatic generation of SMS thus alerting the user against security risk.