What is GSM in Telecommunications?

GSM stands for Global System for Mobile Communications which is a technology behind 2G networks. It is a cellular network technology enabling communication via a series of connected base stations and devices. It uses time division multiple access (TDMA) to split frequency bands into time slots, enabling multiple users to share the same frequency channel. This technology used to be widely spread within businesses to deploy their IoT and M2M devices. But as we are expecting a 2G sunsetting over coming years, it becomes less actual for IoT deployments these days.  

What Are GSM Components and Their Functions? 

  • Base Transceiver System (BTS) is responsible for managing the radio components and maintaining communication with the Mobile Station (MS). 

  • Base Station Controller (BSC) allocates necessary time slots between the BTS and the Mobile Switching Center (MSC). 

  • Home Location Register (HLR) is a reference database that stores subscriber parameters such as the subscriber's ID, location, and authentication key. 

  • Visitor Location Register (VLR) comprises a temporary copy of most of the data stored in the HLR, specifically related to active subscribers within a particular area. 

  • Equipment Identity Register (EIR) is a database that maintains a list of valid devices authorized to connect to the network. 

  • Authentication Center (AuC) enables authentication of subscribers, ensuring the security and validity of their access to the network. 

Basic Standards Applied to IoT Connectivity 

The below standards are commonly used in GSM-based IoT connectivity: 

  • GPRS (General Packet Radio Service) which enables packet-switched data transmission. It provides an "always-on" internet connection for IoT devices in order to send and receive efficiently. 

  • EDGE (Enhanced Data Rates for GSM Evolution) entails higher data transfer rates.  IoT devices transfer and receive data at higher speeds, applicable to cases requiring more bandwidth, for instance video streaming. 

  • SMS (Short Message Service) enables short text messages, including alerts, notifications, and commands, to the devices. 

How GSM Works 

GSM incorporates TDMA (Time Division Multiple Access), FDMA (Frequency Division Multiple Access), and Frequency hopping. It used to utilize two frequency bands spanning a width of 25 MHz: the frequency band from 890 MHz to 915 MHz for up-link communication and the frequency band from 935 MHz to 960 MHz for down-link communication. Subsequently, two additional bands with a width of 75 MHz each were introduced: the up-link band ranging from 1710 MHz to 1785 MHz and the down-link band ranging from 1805 MHz to 1880 MHz. GSM splits the 25 MHz band into 124 channels, with each channel width of 200 KHz.  

GSM VS CDMA VS LTE VS 5G 

Technology 

GSM 

CDMA 

LTE 

5G 

Generations 

2G 

2G, 3G 

4G 

5G 

Multiple Access Technique 

TDMA 

CDMA 

OFDMA 

OFDMA, SC-FDMA 

Data Transfer Speeds 

Up to 384 Kbps (GPRS/EDGE) 

Up to 2.4 Mbps (CDMA2000 1xRTT) 

Up to 100 Mbps (LTE) 

Up to 10 Gbps (5G) 

Latency 

Moderate 

Moderate 

Low 

Ultra-Low 

Spectral Efficiency 

Low 

Moderate 

High 

Very High 

Frequency Bands 

Various (850 MHz, 900 MHz, 1800 MHz, 1900 MHz) 

Various (450 MHz, 800 MHz, 1900 MHz, 2100 MHz) 

Various (700 MHz, 800 MHz, 1800 MHz, 2600 MHz) 

Various (Sub-6 GHz, mmWave) 

Usage 

Global 

Global 

Global 

Global 

Key Advantages 

Wide coverage, voice-centric, backward compatibility 

Increased capacity, better call quality, backward compatibility 

High-speed data, low latency, efficient spectrum utilization 

Ultra-high data rates, ultra-low latency, massive device connectivity 

Key Applications 

Voice calls, text messaging 

Voice and data services 

Mobile internet, video streaming, real-time applications 

IoT, augmented reality, autonomous vehicles, mission-critical communications