Gsm architecture

It defines the different elements and the ways in which they interact to enable the overall system operation to be maintained. The GSM network architecture is now well established and with the other later cellular systems now established and other new ones being deployed, the basic GSM network architecture has been updated to interface to the network elements required by these systems.

Gsm architecture

Base station subsystem — the base stations and their controllers Network and Switching Subsystem — the part of the network most similar to a fixed network, sometimes just called the "core network" GPRS Core Network — the optional part which allows packet-based Internet connections Operations support system OSS — network maintenance Base station subsystem[ edit ] GSM cell site antennas in the Deutsches MuseumMunichGermany GSM is a cellular networkwhich means that cell phones connect to it by searching for cells in the immediate vicinity.

There are five different cell sizes in a GSM network— macromicropicofemtoand umbrella cells. The coverage area of each cell varies according to the implementation environment. Macro cells can be regarded as cells where the base station antenna is installed on a mast or a building above average rooftop level.

Micro cells are cells whose antenna height is under average rooftop level; they are typically used in urban areas.

Picocells are small cells whose coverage diameter is a few dozen meters; they are mainly used indoors. Umbrella cells are used to cover shadowed regions of smaller cells and fill in gaps in coverage between those cells.

Cell horizontal radius varies depending on antenna height, antenna gain, and propagation conditions from a couple of hundred meters to several tens of kilometres.

There are also several implementations of the concept of an extended cell, [18] 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.

GSM network areas

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.

GSM carrier frequencies[ edit ] Main article: 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 architecture

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. These used a system based on linear predictive coding LPC. In addition to being efficient with bitrate s, these codecs also made it easier to identify more important parts of the audio, allowing the air interface layer to prioritize and better protect these parts of the signal.

Finally, with the development of UMTSEFR was refactored into a variable-rate codec called AMR-Narrowbandwhich 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.

This allows the user to retain his or her information after switching handsets. Alternatively, the user can change operators while retaining the handset simply by changing the SIM.

SIM lock Sometimes mobile network operators restrict handsets that they sell for use with their own network. This is called locking and is implemented by a software feature of the phone. A subscriber may usually contact the provider to remove the lock for a fee, utilize private services to remove the lock, or use software and websites to unlock the handset themselves.

It is possible to hack past a phone locked by a network operator. It has considered the user authentication using a pre-shared key and challenge-responseand over-the-air encryption. However, GSM is vulnerable to different types of attack, each of them aimed at a different part of the network.

The security model therefore offers confidentiality and authentication, but limited authorization capabilities, and no non-repudiation.

GSM uses several cryptographic algorithms for security.GSM Architecture. A GSM network consists of the following components: A Mobile Station: It is the mobile phone which consists of the transceiver, the display and the processor and is controlled by a SIM card operating over the network.

The GSM contains most of the necessary capabilities to support packet transmission over GSM. The critical part in the GPRS network is the mobile to GSN (MS-SGSN) link which includes the MS-BTS, BTS-BSC, BSC-SGSN, and the SGSN-GGSN attheheels.com 1 shows block diagram of GSM architecture.

Given below is a simple pictorial view of the GSM architecture. The additional components of the GSM architecture comprise of databases and messaging systems functions: Home Location Register (HLR) Visitor Location Register (VLR) Equipment Identity Register (EIR) Authentication Center (AuC).

Given below is a simple pictorial view of the GSM architecture. The additional components of the GSM architecture comprise of databases and messaging systems functions: Home Location Register (HLR) Visitor Location Register (VLR) Equipment Identity Register (EIR) Authentication Center (AuC).

Ho Chi Minh City University of Technology. Faculty of Electrical and Electronics Engineering Department of Telecommunications GSM Architecture. The GSM network architecture is now well established and with the other later cellular systems now established and other new ones being deployed, the basic GSM network architecture has been updated to interface to the network elements required by these systems.

GSM - Explain GSM architecture with a neat block diagram, highlighting all the interfaces.