What Is GSM (Global System for Mobile Communications)? Meaning, Working, Architecture, and Applications

GSM (or Global System for Mobile Communications) is defined as a set of mobile communications standards and protocols governing second-generation or 2G networks, first developed and deployed in Europe. This article explains how GSM works, its architecture, and its top applications in 2022.

What Is GSM?

GSM (Global System for Mobile Communications) is a set of mobile communications standards and protocols governing second-generation or 2G networks, first developed and deployed in Europe.

GSM is a digital cellular communication standard that is universally accepted. The European Telecommunications Standards Institute created the GSM standard to define the procedures for second-generation digital mobile networks that are used by devices such as mobile phones. It is a wide-area communications technology program that utilizes digital radio channeling to bring forth audio, information, and multimedia communication systems.

GSM is a mobile network and not a computer networkOpens a new window – this implies that devices interact with it by looking for nearby cells. GSM, including other technological advances, has influenced the evolution of mobile wireless telecommunication services. A GSM system manages communication between mobile stations, base stations, and switching systems. 

Every GSM radio channel is 200 kHz wide and is additionally divided into frames of 8-time slots. The global system for mobile communication (GSM) was first known as Groupe Special Mobile, which is the reason for the acronym. The GSM system comprises mobile stations, base stations, and intertwining switching systems.

The GSM program enables 8 to 16 audio users to share every radio channel, and every radio transmission location may have multiple radio channels. Because of its simplicity, affordability, and accessibility, GSM is presently the most commonly used network technology in the Internet of Things (IoT)Opens a new window applications.

However, this is likely to change in the coming years. Various programs have been designed without the advantage of standardized provisions all through the transformation of mobile telecommunication services.

This significantly created many issues tied directly to consistency as digital radio technology advanced. The global system for mobile communication is designed to address these issues. GSM accounts for about 70% of the world’s digital cellular services. GSM automates and encodes the information before transmitting it via a channel including three distinct streams of user information inside each time slot. For the vast majority of the world, it is also the leading 2G digital cell phone standard. It governs how cell phones interact with the land-based tower system.

In Europe, GSM operates in the 900MHz and 1.8GHz bands, while in the United States, it functions in the 1.9GHz PCS band. GSM describes the overall mobile network, not just the Time division multiple access air interface, as it is centered on a circuit-switched structure that splits every 200 kHz channel into eight 25 kHz time frames. It is a rapidly expanding transmission technique, with over 250 million GSM users by the early 2000s. The one billionth GSM consumer was linked by mid-2004.

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How Does GSM Work?

While using the 900 MHz bandwidth was one of the initial plans for the Global System of the mobile communication path, it is no longer mandatory. GSM systems since then have grown and can now operate in a variety of frequency bands. 

The GSM frequency bandwidths are generally separated into two paths: 900/1800 MHz and 850/1900 MHz. Most of Europe, Asia, Africa, the Middle East, and Australia use the 900 MHz / 1800 MHz band. North and South America, as well as the United States, Canada, Mexico, and other countries, use the 850 MHz / 1900 MHz band. In the Global system for mobile communication, 900 MHz bandwidth spans 880 to 960 MHz, while the 1800 MHz band spans 1710 to 1880 MHz.

The 850 MHz frequency band, on the other hand, spans 824 to 894 MHz, while the 1900 MHz band spans 1850 to 1990 MHz. GSM-based cellular systems use a series of numbers or unique codes to recognize cellular subscribers and deliver the appropriate assistance to them. IMSI (International Mobile Subscriber Identity) is a unique serial code for every SIM card. To conceal the permanent identity, the phone network can create a short-term code called Temporary Mobile Subscriber Identity for each IMSI.

The Mobile Station International Subscriber Directory Number is the complete phone number for a particular SIM, including all prefixes. Lastly, MSRN is an abbreviation for Mobile Subscriber Roaming Number, and it is a short-term cellphone number given to a cellular station if it is not on the local network (roaming). Therefore, any calls or communication systems can be tied to it.

Numerous GSM network carriers have roaming agreements with foreign corporations, allowing people to use their phones when traveling internationally. SIM cards with household network access designs can be changed to those with a metered local connection, lowering roaming costs while maintaining service. The global system for mobile communication organizes the geographical area into hexagonal cells, the size of which is controlled by the transmitter’s power and the number of end-users. The middle of the cell has a base station consisting of a transceiver (which combines the transmitter and reception) and an antenna. 

Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA) are the two critical approaches used by GSM:   

• FDMA is the technique of subdividing frequency bands into many bands, each of which is allocated to specific users.  In GSM, FDMA separates the 25MHz bandwidth into 124 carrier frequencies by 200 kHz. Every base station has one or more carrier frequencies assigned to it.
• Time Division Multiple Access (TDMA) is the practice of allocating the same frequency to multiple users by separating the bandwidths into various time slots. Every subscriber is assigned a timeslot, allowing different stations to split the same transmission area.

TDMA is used to divide each subdivided carrier frequency into different time slots for GSM. Each Time-division multiple access frame does have 8-time slots and takes 4.164 milliseconds (ms). This means that every time slot or physical channel in this structure should take 577 microseconds, and information is transferred in bursts during that time. A GSM system has several cell sizes, including macro, micro, Pico, and umbrella cells. Each cell differs depending on the execution domain.

A GSM network has five cell sizes: macro, micro, pico, and umbrella. Depending on the option provided, the connectivity of each cell differs. The time division multiple access (TDMA) method works by giving every client a varying time slot on a similar frequency. This can easily be adapted to sending and receiving data and voice communication and it can hold bandwidths ranging from 64kbps to 120Mbps.

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The Architecture of GSM

The GSM architecture is made up of three central systems. The following are the primary components of the GSM architecture:

• The network switching system (NSS)
• The mobile station (MS)
• The base station system (BSS)
• The operations and support system (OSS)

1. The network switching system (NSS)

NSS is a GSM element that provides flow management and call processing for mobile devices moving between base stations. The switching system consists of the functional units listed below.

• Mobile Services Switching Center (MSC): Mobile Switching Center is integral to the GSM network architecture’s central network space. The MSC supports call switching across cellular phones and other fixed or mobile network users. It also monitors cellular services, including registration, location updates, and call forwarding to a roaming user.
• Home Location Register (HLR): It is a set of data items used for storing and managing subscriptions. It provides data for each consumer as well as their last known position. The HLR is regarded as the most significant database because it preserves enduring records about users. When a person purchases a membership from one of the operators, they are enlisted in that operator’s HLR.
• Visitor Location Register (VLR): VLR is a database that provides subscriber information necessary for the MSC to service passengers. This includes a short-term version of most of the data stored in the HLR. The visitor location register can also be run as a standalone program, but it is usually implemented as a component of the MSC.
• Equipment Identity Register (EIR): It is the component that determines if one can use particular mobile equipment on the system. This consists of a list of every functioning mobile device on the system, with each mobile device recognized by its own International Mobile Equipment Identity (IMEI) number.
• Authentication Center (AuC): The AUC is a unit that offers verification and encryption factors to ensure the user’s identity and the privacy of every call. The verification center is a secure file that contains the user’s private key in the SIM card. The AUC shields network operators from various types of fraud prevalent in the modern-day cellular world.

2. The mobile station (MS)

The mobile station is a cell phone with a display, digital signal processor, and radio transceiver regulated by a SIM card that functions on a system. Hardware and the SIM card are the two most essential elements of the MS. The MS (Mobile stations) is most widely recognized by cell phones, which are components of a GSM mobile communications network that the operator monitors and works.

Currently, their size has shrunk dramatically while their capabilities have skyrocketed. Additionally, the time between charges has been significantly improved. 

3. The base station system (BSS)

It serves as a connection between the network subsystem and the mobile station. It consists of two parts: 

• The Base Transceiver Station (BTS): The BTS is responsible for radio connection protocols with the MS and contains the cell’s radio transceivers. Companies may implement a significant number of BTSs in a big metropolitan area. Each network cell has transceivers and antennas that make up the BTS. Based on the cell’s consumer density, every BTS includes anywhere from one to sixteen transceivers.
• The Base Station Controller (BSC): The BSC is responsible for managing the radio resources of one or more BTS(s). This manages radio channel configuration and handovers. The BSC serves as the link seen between mobile and MSC. It allocates and emits MS frequency bands and time slots. Additionally, the BSC is responsible for intercell handover and transmits the BSS and MS power within its jurisdiction. 

4. The operations and support system (OSS) 

The operation support system (OSS) is a part of the overall GSM network design. This is linked to the NSS and BSC components. The OSS primarily manages the GSM network and BSS traffic load. As the number of BS increases due to customer population scaling, a few maintenance duties are shifted to the base transceiver stations, lowering the system’s financial responsibility. The essential purpose of OSS is to have a network synopsis and assist various services and maintenance organizations with their routine maintenance arrangements. 

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Top 4 Applications of GSM

The critical applications of GSM technology include:

1. Sending and receiving short messages

The ability to send and receive text messages to and from mobile phones is known as the Short Message Service (SMS). SMS provides services related to two-way paging, except with more features incorporated into the cell device or port. Text messaging allows a cell phone user to receive a quick short message on their cell phone. Similarly, that user can compose a brief message to send to other users.

SMS delivers short text messages of up to 140 octets over the GSM platform’s control system air interface. The Short Message Service Center (SMSC) stores and transmits short messages from mobile users to their intended recipients. One may use it to send and receive brief messages, saving time due to the rapid transmission of communications. Furthermore, there is no need to go online; the mobile device has a signal, and it can send and receive short messages.

2. GSM and data security 

Data security is the most crucial factor for usage operators. Specific aspects are now implemented in GSM to improve security. There is currently an indication for ME and MS in this framework. The system proposes two subsystems. The appliance control subsystem allows users to remotely control household appliances, while the security alert subsystem provides fully automated security monitoring.

This same system can instruct users via SMS from a particular phone number on how to change the condition of the home appliance based on the person’s needs and preferences. The client is configured via SIM, allowing the system to observe Mobile subscribers on the database. GSM also includes features for signal encryption.

The second element of GSM security is security alert, which would be accomplished in such a way that upon identification of an invasion, the system would allow for the automatic creation of SMS, thereby notifying the user of a potential threat.

GSM technology will enable communication with anyone, wherever, at any moment. GSM’s functional architecture employs sophisticated networking principles, and its idea offers the advancement of GSM as the first move towards an authentic personal communication network with sufficient homogeneity to guarantee compatibility.

3. GSM for mobile system handover

The procedure of handover in any mobile system is critical. It is a necessary process, so handover could lead to call loss if done improperly. Undelivered calls could be especially aggravating to subscribers, and as the percentage of undelivered calls grows, so does user dissatisfaction, so they’re more likely to switch to another network.

As a result, GSM handover was given special consideration when creating the standard. Whenever a cellular customer switches cells, the radio signal shifts from past to new. Even though the GSM network is complicated, in contrast to other systems, the flexibility of the GSM procedure provides better performance to subscribers. In a GSM network, there are four basic types of handoffs:

• Intra-cell handover: This type of handover is used to improve data traffic in the cell or to strengthen connection performance by modifying the carrier signal.
• Inter-cell handover: Additionally, it is known as intra-BSC handover. In this instance, the mobile changes cells while remaining in the BSC. Here, the BSC is in control of the transfer procedure.
• Inter-BSC handover: It’s also known as an intra-MSC handover. Because BSC can only handle a restricted number of cells, we may have to move a phone from one BSC to the other. Here, the handover is managed by the MSC. 
• Inter-MSC handoff: This occurs when a mobile device moves from one MSC area to the next. MSC is spread over a wide area.

4. GSM in medical services

If the patient is severely injured or sick, but all they have access to is a phone, trying to connect with the closest hospital would be simple. If the patient is connected to the doctor, they can receive initial care while on the way to the healthcare facility. In the event of a disease, doctors can review patient history and prepare for additional tests while providing proper care. 

Whenever a patient, attendant, or hospital member of staff becomes stranded on hospital grounds due to a power outage, GSM-fixed cellular terminals allow the individual to connect very fast with the closest emergency responders. An individual in that circumstance can request help using the GSM SIM in the installed Fixed Cellular Terminal (FCT). Telemedicine services are responsible for the entire situation. One could use the telemedicine system in any of the three ways listed below.

• Utilizing video conferencing, patients seated in one location can directly communicate with physicians, thus continuing the healing process.
• Leveraging health monitoring sensors that continuously update information about the patient’s health and guide hospitals and doctors to continue treatment.
• Conveying the obtained health records and transmitting obtained data for consultation and processing.

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Takeaway

We live in the 5G generation, yet GSM remains a standard technology for mobile phones and IoT device managementOpens a new window environments. This is because it is a building block for wireless connectivity, particularly in remote regions. GSM also functions as a redundancy method, helping systems stay connected even if the primary networks are offline. Enterprises must understand and accommodate GSM technology to build a sustainable IoT environment.

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