GSM is a set of mobile communications standards and protocols governing second-generation or 2G networks.
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.
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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.
The Working of a GSM Network
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 network – 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) 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.
How Does GSM Work?
At first, GSM used the 900 MHz bandwidth. But now, it can work on many different frequencies.
GSM uses two main frequency bands: 900/1800 MHz and 850/1900 MHz. Europe, Asia, Africa, the Middle East, and Australia use the 900 MHz / 1800 MHz band. The United States, Canada, Mexico, and other countries use the 850 MHz / 1900 MHz band.
The 900 MHz band is from 880 to 960 MHz. The 1800 MHz band is from 1710 to 1880 MHz. The 850 MHz band is from 824 to 894 MHz. The 1900 MHz band is from 1850 to 1990 MHz.
GSM uses unique codes to identify users. IMSI is a serial code for every SIM card. To hide the permanent identity, a temporary code is used.
The Mobile Station International Subscriber Directory Number is the full phone number for a SIM. MSRN is a short-term cellphone number for roaming. It ties calls or communication systems to it.
Many GSM network carriers have roaming agreements. This lets people use their phones abroad. SIM cards can be changed to save on roaming costs.
The GSM system divides areas into hexagonal cells. The size of the cells depends on the transmitter's power and the number of users. The middle of each cell has a base station with a transceiver and an antenna.
FDMA and TDMA are key methods used by GSM:
- FDMA divides frequency bands into many bands for specific users. GSM uses FDMA to separate the 25MHz bandwidth into 124 carrier frequencies by 200 kHz. Each base station has one or more carrier frequencies assigned to it.
- TDMA allocates the same frequency to multiple users by separating bandwidths into time slots. Every subscriber is assigned a timeslot, allowing different stations to split the same transmission area.
TDMA divides each subdivided carrier frequency into different time slots for GSM. Each Time-division multiple access frame has 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 has three main systems. The key parts are:
- 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 crucial for managing mobile devices as they move. It includes several important units.
- Mobile Services Switching Center (MSC): This is a core part of the GSM network. It handles calls and services for users. It also tracks user locations and call forwarding.
- Home Location Register (HLR): It stores user data and subscriptions. The HLR keeps long-term records of users. When someone joins a network, they are added to this database.
- Visitor Location Register (VLR): This database gives MSC the info it needs for users. It's a short-term version of HLR data. VLR can also run as a standalone system.
- Equipment Identity Register (EIR): It checks if mobile equipment is allowed on the system. It lists all devices by their IMEI number.
- Authentication Center (AuC): This unit ensures user identity and call privacy. It uses a secure file with user keys. The AuC helps protect against fraud.
2. The mobile station (MS)
The mobile station is a cell phone with key components. It has a display, processor, and radio. These are controlled by a SIM card.
Cell phones are the most common MS. They have become smaller but more powerful. They also charge faster now.
3. The base station system (BSS)
The BSS connects the network to mobile stations. It has two main parts:
- The Base Transceiver Station (BTS): It handles radio connections with MS. BTSs are used in many areas. Each BTS has transceivers and antennas.
- The Base Station Controller (BSC): It manages radio resources for BTSs. The BSC is the link between mobile and MSC. It controls frequency allocation and handovers.
4. The operations and support system (OSS)
The operation support system (OSS) is a key part of GSM network design. It works with the NSS and BSC parts. The OSS manages the GSM network and BSS traffic load.
As more BS are added due to growing customer numbers, some maintenance tasks move to base transceiver stations. This reduces the system's financial burden. The main goal of OSS is to give a network overview. It helps various services and maintenance teams with their daily tasks.
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Top 4 Applications of GSM
GSM technology has several important uses:
1. Sending and receiving short messages
The ability to send and receive text messages is known as the Short Message Service (SMS). SMS offers more features than two-way paging. It lets users send and receive brief messages quickly.
SMS sends short text messages up to 140 octets over the GSM platform. The Short Message Service Center (SMSC) stores and sends these messages. It's fast and doesn't require an internet connection.
2. GSM and data security
Data security is crucial for GSM users. GSM has added features to improve security. It includes two subsystems: appliance control and security alert.
This system can send instructions via SMS to control home appliances. It's configured via SIM, allowing it to monitor Mobile subscribers. GSM also has signal encryption features.
The security alert system automatically sends SMS if it detects an invasion. This notifies the user of a potential threat.
GSM technology allows communication anywhere, anytime. Its architecture uses advanced networking principles. It aims to create a personal communication network with full compatibility.
3. GSM for mobile system handover
Handover is a critical process in mobile systems. It's essential to avoid call loss during handover. Improper handover can lead to undelivered calls, causing user dissatisfaction.
GSM handover was a key focus in its development. It ensures smooth signal transfer when a user switches cells. GSM's flexibility offers better performance to users. There are four main types of handoffs in GSM networks.
- 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 management 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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