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Last Updated: Jul 12, 2024

GSM Architecture

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Global System for Mobile Communications or GSM is a set of protocols and standards governing the 2nd generation networks, better known as 2G networks.  It operates on different frequency bands of 850 MHz, 900 MHz, 1800 MHz and 1900 MHz. 

GSM Architecture

Developed and deployed in Europe, GSM of many functional units, namely:

  • MS or the Mobile Station 
  • BSS or the Base Station Subsystem 
  • NSS or the Network Switching Subsystem 
  • OSS or the Operation Support Subsystem 
  • The Public Network

The  GSM architecture consists of interconnected subsystems. It interacts with itself and the users with the help of certain network interfaces.

The GSM network can be broadly divided into four parts−

  1. The Mobile Station
  2. The Base Station Subsystem (BSS)
  3. The Network Switching Subsystem (NSS)
  4. The Operation Support Subsystem (OSS)

1. The Mobile Station (MS)

It consists of two parts:

Mobile equipment 

It is a portable, vehicle-mounted, handheld device that is uniquely identified by an IMEI number. Sending and receiving SMS, voice and data transmission are some of the perks of this equipment.

Subscriber Identity module(IMSI)

Generally protected with a password or PIN, The sim basically allows the transmission of calls along with other services. It is a miniature chip containing the  International Mobile Subscriber Identity (IMSI) number. 

2. The Base Station Subsystem (BSS) 

Also known as the radio subsystem, it provides and handles radio transmission pathways between the mobile station and the Mobile Switching Centre (MSC). It also comprises of two parts: 

Base Transceiver Station (BTS)

It is responsible for encoding, encrypting, multiplexing, modulating, and feeding the RF signal to the antenna.

Base Station Controller (BSC)

It is responsible for assigning frequency and time slots for all mobile stations in their respective area, along with handling call set-up, transcoding, and adaptation functionality handover for each MS radio power control.

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3. The Network Switching Subsystem (NSS)

It is the most significant part of the Mobile Switching Center (MSC). It is responsible for switching calls between mobile and other fixed or mobile network users, along with the management of mobile services.

It has the following elements:

  • Visitor Location Register (VLR) :The Visitor Location Register is a database that contains the locations of all mobile subscribers in the area of service of the MSC.
  • Home Location Register (HLR) :The Home Location Register is a database that contains all the pertinent data of subscribers authorized to use a GSM network.
  • Equipment Identity Register (EIR): The Equipment Identity Register is a database that contains the record of all the allowed or banned persons in the network.
  • Authentication Center (AC): Authentication Centre provides security against intruders in the air interface along with providing security triplets RAND, SRES, Ki. It also keeps a track of the authentication keys and algorithms.

4. Operation Support Subsystem (OSS) 

The implementation of the Operations and Maintenance Center (OMC) is called the Operation Support Subsystem. The Operation Support Subsystem is an integral part of the overall GSM architecture interlinked with the BSC and NSS components. It administrates commercial and network operations along with security management and maintenance tasks.

The Public Network

The Public Network also comprises of two parts:


Designed in the 1980s and improved in the 1990s, Integrated Services Digital Network is a set of international communication standards.


The Public Switched Telephone Network is the database that contains all the information regarding the interconnected public telephone network worldwide. It was designed for analog calls, but now it is completely digital. 

Also see,  Personal Area Network

Features of GSM 

Some of the salient features of GSM are:

  • GSM supports numerous handheld devices
  • The use of GSM has voice clarity
  • It has international ISDN compatibility
  • It is code efficient and has a low service cost
  • GSM keeps updating with new features and services
  • Spectral frequency efficiency
  • GSM supports international roaming
  • It also supports low-powered devices
  • It has ease in accessing the networks

Applications of GSM

The following are the applications of GSM:-

  1. Medical Services: In cases when a patient, attendant, or hospital staff member gets stranded on hospital grounds due to any unforeseen circumstances like a power outage, the GSM-fixed cellular terminals let the person connect immediately with the nearest emergency responders. GSM is also used in health monitoring sensors that constantly keep track of all the details regarding the patient’s health.
    Also, GSM is used for transferring the acquired health records and transmitting them for further consultation and processing.
  2. Mobile System Handover: Generally, mobile system handovers are necessary and lead to call loss if anything goes wrong. The flexibility of the GSM technique provides more suitable performance to subscribers.

There are four types of handovers in the GSM architecture network:

  • Intra-cell handover: is used for the modification of the carrier signal.
  • Inter-cell handover: is used when the mobile shifts cells while still in the BSC.
  • Inter-BSC handover: BSC can only take a limited number of cells, which is why transferring a phone from one BSC to the other is needed
  • Inter-MSC handoff:  is used when a mobile device moves from an MSC area to the next area. 

Advantages of GSM

  • Plenty of service providers and handsets are available in today’s market. Consumers can choose from a variety of options and take full advantage of them.
  • Also, the service providers have different data and cellular plans according to the needs of the people. They are cost-efficient and also give free SMS services.
  • Value-added services like General Packet Radio Services (GPRS) make GSM a better option.
  • The quality of calls from the GSM are best in the market, as compared to that of the Code-Division Multiple Access (CDMA).
  • Power consumption is significantly less in the GSM mobiles
  • GSM also provides less signal distortion.

Disadvantages of GSM

  • In GSM, the per unit charge is higher than the CDMA.
  • The SIM does not have a backup function, so when it gets lost, the user may lose all the data in the SIM.
  • In GSM, the signals are easily detected as compared to that of CDMA.
  • GSM networks have a limited area range for calls and other services.
  • The GSM networks, in peak hours, can go through network congestion.

Frequently Asked Questions

Why use GSM architecture?

GSM architecture is commonly used for various reasons. It provides clearer voice quality, reduced background noise, and improved call privacy. Additionally, digital data services supported by GSM enable various applications like text messaging and mobile internet access.

What are the three major components of GSM?

GSM consists of the Mobile Station (MS) comprising the mobile device and SIM card, the Base Station Subsystem (BSS) managing the radio interface, and the Network Switching Subsystem (NSS) controlling call switching and mobility.

Which technology is used in GSM?

GSM employs Time Division Multiple Access (TDMA) technology, dividing radio frequencies into time slots for concurrent user transmissions.

What type of modulation is used in GSM?

GSM utilizes Gaussian Minimum Shift Keying (GMSK) modulation, which ensures efficient spectrum use by maintaining constant phase and reducing signal interference.


This article covers the entirety of the GSM architecture along with its services, applications, advantages and disadvantages. Hope this article helped you in your learning journey.

Recommended Readings:

Happy Learning! 

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