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GSM -The Mobile Station


What is GSM?

GSM -The Mobile Station

The development of wireless mobile telecommunications comprises GSM along with different technologies such as Enhanced Data GSM Environment (EDGE), Universal Mobile Telecommunications Service (UMTS), General Packet Radio Service (GPRS), and High-Speed Circuit-Switched Data (HSCSD).


The analogue method was used to build GSM's predecessors, which included the United States Advanced Mobile Phone Service (AMPS) and the United Kingdom's Total Access Communication System (TACS). But when more people used these telecommunications services, they could not grow. These technologies' flaws proved that a more efficient cellular technology that could be used globally is required. The effort to create a European standard for digital telecommunications was established by the European Conference of Postal and Telecommunications Administrations (CEPT) in 1983 to achieve that goal.

CEPT established various requirements for the new network, including support for high-quality voice, low latency, hand-held devices, new services, international roaming, and ISDN (Integrated Services Digital Network) capabilities.

An agreement to implement a telecommunications standard was signed in 1987 by delegates from thirteen European nations. Then, the European Union (EU) passed legislation requiring GSM to be a standard throughout Europe. The European Telecommunications Standards Institute took over management of the GSM project in 1989, succeeding CEPT.

Finland was the first country to provide GSM-based mobile services in 1991. The GSM standard frequency range was extended from 900 MHz to 1,800 MHz in a year. 80% of the worldwide mobile market comprised GSM in 2010.

However, several telecom companies, like Telstra in Australia, have shut down their GSM networks. Singapore shut down its 2G GSM network in 2017.


An extensive GSM mobile station (MS) description can be obtained here.

Mobile Equipment (ME): The physical device, typically your mobile phone or mobile device, is the mobile equipment. The handset, display, keypad, microphone, speaker, and other features like cameras and sensors are all regarded hardware components.

User interface and interaction, such as dialling and receiving calls, sending text messages, and executing different programs, fall under the authority of the ME.

Subscriber Identity Module (SIM) Card: The SIM card is a small, removable card inserted into the phone. Important details specific to the user and their GSM network connection are included in it.

The International Mobile Subscriber Identity, which recognizes the subscriber on the network specifically, and the Integrated Circuit Card Identifier (ICCID), which identifies the SIM card itself, are two crucial bits of data stored on the SIM card. In addition, the SIM card contains other security-related data and authentication keys, such as the Ki (Authentication Key). Users can change their identity and subscription to other mobile devices with a SIM card transfer.

Security and Authentication: The MS is essential to GSM secure communication. It establishes a secure connection with the network using the authentication keys on the SIM card. The SIM card creates a unique random number (RAND) when a mobile device attempts to connect to the network.

The SIM card and the network individually compute a signed response (SRES) using the RAND and the Authentication Key (Ki). The SRES is sent back to the network for validation. A link is made, and the network's and mobile device's authenticity and security are confirmed if the SRES complies with the network's figure.

Network Access: By establishing a connection with the closest Base Transceiver Station (BTS), the MS can communicate with the GSM network. Users can access mobile data services, exchange SMS messages, and make calls through this connection.

The MS can shift its connection from one BTS to another as users travel within the network's service area without disrupting a conversation or data session. One of the most important functions of MS is this seamless transition.

User Interface: To connect with the GSM network and access different services, customers can utilize an easy-to-use interface provided by the MS.

It has audio components for voice communication, a keypad or touchscreen for input, and a display for informational purposes.

Modern mobile devices' sensors, cameras, and application capabilities may also be enhanced.

Composition of the network

GSM -The Mobile Station

The mobile device itself, the base station subsystem (BSS), the network switching subsystem, and the operation and support subsystem are the four distinct components that comprise the GSM network and operate as a whole.

Hardware establishes a connection between the mobile device and the network. The network receives identifying information regarding the phone client from the subscriber identity module (SIM) card.

The BSS manages communication from the cell phone to the NSS. Its primary parts are the Base Station Controller and the Base Transceiver Station. While the BSC supplies the intelligence, the BTS stores the hardware—mostly radio transmitter-receivers and antennas—that facilitates communication with mobile phones. A collection of base transceiver stations is managed and communicated with by the BSC.

The GSM network architecture's NSS, often called the core network, locates callers to facilitate the delivery of cellular services. The NSS belongs to mobile providers. The home location register (HLR) and mobile switching centre (MSC) are two components that constitute the NSS. These parts carry out many tasks, including call routing, SMS (short message service) delivery, SIM card authentication, and caller account data storage.

Users can typically retain phone access when they travel abroad since many GSM network carriers have roaming agreements with other countries. Metered local access SIM cards can be used to replace SIM cards with home network access setups, greatly lowering roaming fees without compromising service.

Security details

"Although GSM was designed to be an encrypted wireless protocol, it is still susceptible to attacks. GSM utilizes pre-shared keys in the form of passwords and challenge-response authentication, where users must provide an authorized response to a question.

Among the cryptographic security techniques used by GSM are stream ciphers, which encrypt plaintext digits to ensure user conversation privacy. Three stream ciphers—A5/1, A5/2, and A5/3—are employed for this purpose. However, it's worth noting that the A5/1 and A5/2 algorithms have been successfully cracked and made public, rendering them vulnerable to plaintext attacks."

GSM uses GPRS, a packet-based communication technology for data transmission, including web browsing. But in 2011, it was also discovered that GPRS's two cyphers, GEA1 and GEA2, were cracked. To track packets on the GPRS network, researchers released open-source software.

What are the limitations of GSM?

While GSM is the technology preferred for today's communications networks, it is not without difficulties. Some of the drawbacks of GSM are as follows:

Electronic interference: GSM is known to interact with equipment like hearing aids since it uses a pulse-transmission technique. Due to electromagnetic interference, mobile phones are prohibited in several locations, including hospitals, petrol stations, and airports.

Slow bandwidth:  Many users share the same bandwidth while utilizing GSM technology, which can occasionally cause significant delays as additional users join the network.

Limited data transfer rate: GSM provides a somewhat limited data transfer rate. A user must upgrade to a device with a more sophisticated GSM to get better data speeds.

Repeaters: Carriers using GSM technology must deploy repeaters to expand coverage.

Applications of GSM

Sending and receiving short messages

SMS is a short messaging service that sends and receives texts between mobile phones. Mutual paging functions are provided via SMS, though the mobile device or port has additional functionality. Text messaging enables users to receive short texts. In the same way, the user can write a quick message and send it to others.

Up to 140 octets of short text messages can be sent via SMS over the control system air interface of the GSM platform. Text messages from mobile users are kept and sent to their intended receivers through the Short Message Service Center (SMSC).

The rapid transfer of communications allows one to utilize it to send and receive quick messages while saving time. Moreover, there's no need to connect to the internet because the mobile device can send and receive short messages with a signal.

GSM and data security

For usage operators, data security is particularly important. Specific features are being developed in GSM to increase privacy. Currently, this framework includes a sign for ME and MS. It suggests two subsystems. The security alert subsystem provides Fully automated security monitoring, while users can remotely operate local devices using the appliance control subsystem.

Based on the individual's requirements and choices, the same system can offer consumers SMS instructions from a specific phone number to modify the home appliance's state. The system can see mobile subscribers in the database since the client is set up via SIM. Additionally, GSM has signal encryption characteristics.

Security alerts, which constitute the second component of GSM security, would be implemented such that, if an attack is detected, the system automatically generates an SMS to warn the user of a possible danger. Communication with anyone, anywhere, at any time, will be possible via GSM technology.

The objective behind GSM's functional design is to take the initial phase towards establishing an authentic personal communication network that is sufficiently uniform to ensure compatibility. This is achieved via the use of complex networking concepts.

GSM for mobile system handover

As with any mobile system, the handover process is crucial. Handover must be done correctly because it's a vital step; otherwise, there might be a call loss. Subscriptions may find missing calls particularly irritating, and as the number of undelivered calls rises, so does user discontent, increasing the possibility that they might switch to another network.

The standard's development, therefore, took GSM handover into a particular account. A radio signal changes from past to new whenever a cellular customer swaps cells. In contrast to other systems, the GSM method offers subscribers greater reliability despite its complexity. This is because it is more flexible. Four fundamental handoff kinds exist in GSM networks:

Intra-cell handover: This kind of handover changes the carrier signal to increase connection efficiency or enhance data throughput within the cell.

Inter-cell handover: While inside the BSC, the mobile switches cells in this case. This transfer procedure is within the authority of the BSC.

Intra-BSC handover: It is also known as the intra-MSC handover. Transferring a phone from one BSC to another can be required since each BSC can only manage a certain amount of cells.

Inter-MSC handoff: In this case, the MSC monitors the handover. When a mobile device switches from one MSC region to the next, it goes through an inter-MSC handoff. The MSC is dispersed widely.

GSM applications in healthcare

It would be easy to contact the nearest hospital if the patient was ill or injured; all they had access to was a phone. The patient could get the first treatment if linked to the doctor on the journey to the medical institution. Medical professionals can conduct necessary tests, review the patient's medical history, and provide the necessary care in the event of an illness. 

In a power outage, GSM-fixed cellular terminals enable anyone to quickly establish communication with nearby emergency responders, whether they be patients, attendants, or hospital staff members stuck on hospital property. The installed Fixed Cellular Terminal (FCT) GSM SIM allows a person in such a situation to request support. Services related to telemedicine are in charge of everything. Any of the following three methods might be employed with the telemedicine system.

  • Patients can communicate directly with doctors while seated in one place via video conferencing, promoting recovery.
  • Health monitoring devices provide hospitals and physicians with real-time data about a patient's condition and aid in treatment decisions.
  • Transferring the acquired medical records and sending the acquired information for review and handling.


The Mobile Station (MS) in GSM consists of two primary components: the Subscriber Identity Module (SIM) card and the Mobile Equipment (ME), also known as the real hardware. Together, these components form the Mobile Station, which serves as the interface between subscribers and the GSM network. It enables users to access voice and data services securely while maintaining mobility and flexibility across multiple devices. The MS plays a crucial role in the GSM ecosystem, handling tasks such as user interface, network access, security, and authentication.