What is GSM (Global System for Mobile Communications)?
GSM (Global System for Mobile Communications) is the standard technology behind 2G cellular networks. For decades, it was the dominant mobile communication technology, enabling voice calls, Short Messaging Service (SMS) messaging, and basic data services. While newer generations like 3G, 4G, and 5G have primarily replaced it for high-speed data, GSM still plays a vital role in specific applications and regions.
GSM was developed by the European Telecommunication Standards Institute (ETSI). In the 1980s, ETSI recognized the need for a pan-European digital cellular system to replace the fragmented analog systems of the time. This led to the creation of the GSM standard, which quickly gained global acceptance due to its open nature and technical superiority.
GSM networks are designed with flexibility in mind, utilizing four different cell sizes to optimize coverage and capacity:
- Macro cells: These are the largest cells, typically covering several kilometers in radius. They are used to provide wide-area coverage in rural or sparsely populated areas. Macro cells usually have tall antenna towers to maximize signal range.
- Micro cells: Smaller than macro cells, micro cells are often used in urban areas to increase capacity and improve coverage in areas with high user density. Their antennas are typically mounted on rooftops or other structures below the average roof level.
- Pico cells: These are the smallest cells, with a diameter of just a few meters. Pico cells are deployed in high-traffic areas like airports, stadiums, or shopping malls to provide localized coverage and capacity boosts.
- Umbrella cells: Umbrella cells are strategically placed to fill in coverage gaps or shadowed regions between other cell types. They can also provide additional capacity in areas with fluctuating demand.
The architecture of GSM
GSM networks are structured into three main subsystems, each with specific functions:
Mobile station (MS)
- This is the user’s mobile phone or device.
- It consists of the mobile equipment (the physical phone) and a Subscriber Identity Module (SIM) card.
- The SIM card holds the user’s subscription information, phone number, and security keys.
Base station subsystem (BSS)
- This subsystem handles the radio link between the mobile station and the network.
- It consists of two main components:
- Base transceiver station (BTS): The BTS houses the radio transceivers communicating with the mobile stations within its cell. It manages radio channels, signal strength, and handovers between cells.
- Base station controller (BSC): The BSC controls multiple BTSs, manages resource allocation, and handles handovers between cells.
Network and switching subsystem (NSS)
- This is the core of the GSM network, responsible for call routing, mobility management, and other essential functions.
- Key components include:
- Mobile switching center (MSC): The MSC is the central switching node that routes calls between mobile users and to other networks (e.g., PSTN or ISDN).
- Home location register (HLR): The HLR database stores permanent subscriber information, such as their phone number, service profile, and current location.
- Visitor location register (VLR): The VLR is a temporary database that stores information about subscribers currently roaming in a particular area.
- Authentication center (AuC): The AuC is responsible for authenticating subscribers and generating security keys for encryption.
Additionally, there’s the Operation support subsystem (OSS), which network operators use to manage and maintain the network.
How it works together
- Call initiation: When a user calls, their mobile station sends a signal to the nearest BTS.
- BSS connection: The BTS relays the signal to the BSC, which connects it to the MSC.
- Network routing: The MSC determines the location of the called party by querying the HLR and VLR. It then establishes a connection between the two parties.
- Communication: Voice or data is transmitted over the radio link between the mobile stations and the BTSs and through the network via the BSCs and MSC.
This layered architecture ensures efficient communication, resource management, and security within a GSM network.
What are the GSM vs. CDMA vs. LTE differences?
| GSM (2G) | CDMA (2G/3G) | LTE (4G) | |
|---|---|---|---|
| Technology | Time Division Multiple Access (TDMA) | Code Division Multiple Access (CDMA) | Orthogonal Frequency Division Multiplexing (OFDM) |
| Access | Each user gets a specific time slot | Each user receives a unique code | Multiple users share frequencies simultaneously |
| SIM card | Uses a removable SIM card | Traditionally, didn’t use a SIM card | Uses a SIM card |
| Roaming | Generally easier roaming between networks | More limited roaming due to carrier specifics | Roaming depends on agreements between carriers |
| Speed | Slower data speeds | Faster data speeds than GSM | Significantly quicker data speeds than GSM and CDMA |
| Voice | Circuit-switched voice calls | Circuit-switched or packet-switched voice | Voice over LTE (VoLTE) – packet-switched |
GSM or CDMA: Which is more popular?
Global System for Mobile Communications has historically been the more popular technology globally, accounting for over 80% of mobile connections worldwide. However, it’s important to consider regional variations:
- Global dominance: Global System for Mobile Communications became the dominant standard early on, thanks to its open nature, support for SIM cards, and ease of roaming between networks. This led to widespread adoption across Europe, Asia, and many other regions.
- CDMA pockets: CDMA found strongholds in specific markets, notably in the United States with carriers like Verizon and Sprint (before the merger) and in parts of Asia.
- Shift towards LTE: The landscape has shifted with the rise of 4G LTE, the prevalent technology for high-speed mobile data. While LTE is based on GSM’s foundation, it has largely superseded the distinction between GSM and CDMA for most users.
- Legacy use cases: Global System for Mobile Communications still holds relevance in areas with limited infrastructure or for specific applications like IoT devices where its low-bandwidth capabilities and long battery life are advantageous.
What are the benefits of GSM?
- Global reach and roaming: GSM is a globally recognized standard, making it easy for users to roam between different countries and networks seamlessly. This is a significant advantage for travelers and businesses operating internationally.
- Established infrastructure: Global System for Mobile Communications networks have been built and refined over decades, resulting in extensive coverage and reliable connectivity in many parts of the world, including rural areas.
- Cost-effectiveness: Due to its mature technology and widespread adoption, GSM infrastructure is relatively inexpensive to deploy and maintain compared to newer technologies. This can translate to lower costs for consumers and businesses.
- Reliability for Voice and SMS: GSM is known for its reliable voice call quality and SMS delivery, making it a dependable option for essential communication needs.
- Wide device compatibility: Global System for Mobile Communications is supported by a wide range of mobile devices and IoT modules, making it a versatile choice for various applications.
- Security features: While not as robust as newer technologies, GSM does include security measures like encryption and authentication to protect user data and privacy.
- IoT applications: GSM’s low power consumption and wide coverage make it suitable for IoT devices that require long battery life and reliable connectivity, such as asset trackers, smart meters, and remote sensors.
- SMS for critical alerts: GSM’s highly reliable SMS capabilities are ideal for delivering critical alerts and notifications, such as emergency broadcasts or two-factor authentication codes.
What are some limitations of GSM?
While Global System for Mobile Communications has played a significant role in mobile communication, it does have some limitations, particularly compared to newer technologies:
- Data speed limitations: GSM’s data speeds are relatively slow compared to 3G, 4G, and 5G networks. This can make it less suitable for data-intensive tasks like streaming high-definition videos or downloading large files.
- Limited capacity: GSM networks have a finite capacity for handling simultaneous calls and data traffic. This can lead to network congestion in densely populated areas, resulting in dropped calls or slower data speeds.
- Security vulnerabilities: While GSM has security measures, it is still vulnerable to specific attacks, such as eavesdropping and SIM cloning. Newer technologies like LTE and 5G offer more robust security features.
- Limited frequency bands: GSM operates on specific frequency bands (900 MHz and 1800 MHz), sometimes leading to interference issues or limited coverage in certain areas.
- Legacy technology: Global System for Mobile Communications is considered legacy compared to newer generations as a 2G technology. This means ongoing support and development for infrastructure might be limited as the industry focuses on 4G and 5G.
- Power consumption: Global System for Mobile Communications devices can consume more power than those using newer technologies, potentially leading to shorter battery life, especially for data-intensive applications.
