2G

The most common 2G technology was the time-division multiple access (TDMA)-based GSM standard, used in most of the world outside Japan.^{[citation needed]} In North America, Digital AMPS (IS-54 and IS-136) and cdmaOne (IS-95) were dominant, but GSM was also used.^{[2][citation needed]} In Japan the ubiquitous system was Personal Digital Cellular (PDC), though another, Personal Handy-phone System (PHS), also existed.^{[citation needed]}

Three primary benefits of 2G networks over their 1G predecessors were:

• Digitally encrypted phone conversations, at least between the mobile phone and the cellular base station but not necessarily in the rest of the network.
• Significantly more efficient use of the radio frequency spectrum enabling more users per frequency band.
• Data services for mobile, starting with SMS text messages then expanding to Multimedia Messaging Service (MMS).

2.5G ("second-and-a-half generation") refers to 2G systems that incorporate a packet-switched domain alongside the existing circuit-switched domain, most commonly implemented through General Packet Radio Service (GPRS).^[3] GPRS enables packet-based data transmission by dynamically allocating multiple timeslots to users, improving network efficiency. However, this does not inherently provide faster speeds, as similar techniques, such as timeslot bundling, are also employed in circuit-switched data services like High-Speed Circuit-Switched Data (HSCSD). Within GPRS-enabled 2G systems, the theoretical maximum transfer rate is 40 kbit/s (5 kB/s).^[4]

2.75G refers to the evolution of GPRS networks into EDGE (Enhanced Data Rates for GSM Evolution) networks, achieved through the introduction of 8PSK (8 Phase Shift Keying) encoding. While the symbol rate remained constant at 270.833 samples per second, the use of 8PSK allowed each symbol to carry three bits instead of one, significantly increasing data transmission efficiency. Enhanced Data Rates for GSM Evolution (EDGE), also known as Enhanced GPRS (EGPRS) or IMT Single Carrier (IMT-SC), is a backward-compatible digital mobile phone technology built as an extension to standard GSM. First deployed in 2003 by AT&T in the United States, EDGE offers a theoretical maximum transfer speed of 384 kbit/s (48 kB/s).^[4]

Evolved EDGE (also known as EDGE Evolution or 2.875G) is an enhancement of the EDGE mobile technology that was introduced as a late-stage upgrade to 2G networks. While EDGE was first deployed in the early 2000s as part of GSM networks, Evolved EDGE was launched much later, coinciding with the widespread adoption of 3G technologies such as HSPA and just before the emergence of 4G networks. This timing limited its practical application.

Evolved EDGE increased data throughput and reduced latencies (down to 80 ms) by utilizing improved modulation techniques, dual carrier support, dual antennas, and turbo codes. It achieved peak data rates of up to 1 Mbit/s, significantly enhancing network efficiency for operators that had not yet transitioned to 3G or 4G infrastructures. However, despite its technical improvements, Evolved EDGE was never widely deployed. By the time it became available, most network operators were focused on implementing more advanced technologies like UMTS and LTE. As of 2016, no commercial networks were reported to support Evolved EDGE.

2G, understood as GSM and CdmaOne, has been superseded by newer technologies such as 3G (UMTS / CDMA2000), 4G (LTE / WiMAX) and 5G (5G NR). However, 2G networks were still available as of 2023^[update] in most parts of the world, while notably excluding the majority of carriers in North America, East Asia, and Australasia.^[5][6][7]

Many modern LTE-enabled devices have the ability to fall back to 2G for phone calls, necessary especially in rural areas where later generations have not yet been implemented.^[8] In some places, its successor 3G is being shut down rather than 2G – Vodafone previously announced that it had switched off 3G across Europe in 2020 but still retains 2G as a fallback service.^[9] In the US T-Mobile shut down their 3G services while retaining their 2G GSM network.^[10][11]

Various carriers have made announcements that 2G technology in the United States, Japan, Australia, and other countries are in the process of being shut down, or have already shut down 2G services so that carriers can re-use the frequencies for newer technologies (e.g. 4G, 5G).^[12][13]

As a legacy protocol, 2G connectivity is considered insecure.^[14] Specifically, there exist well known methods to attack weaknesses in GSM since 2009^[15] with practical use in crime.^[16] Attack routes on 2G CdmaOne were found later and remain less publicized.^[17]

Android 12 and later provide a network setting to disable 2G connectivity for the device.^[18] iOS 16 and later can disable 2G connectivity by enabling Lockdown Mode.^[19]

In some parts of the world, including the United Kingdom, 2G remains widely used for older feature phones and for internet of things (IoT) devices such as smart meters, eCall systems and vehicle trackers to avoid the high patent licensing cost of newer technologies.^[20] Terminating 2G services could leave vulnerable people who rely on 2G infrastructure unable to communicate even with emergency contacts, causing harm and possibly deaths.^[21]

• Cliff effect
• Dropout
• List of mobile phone generations
• Mobile radio telephone, also known as 0G
• 1G
• 3G
• 4G
• 5G
• 6G
• Wireless device radiation and health