Mobile Phones to Smartphones

In 2024, there are more than 8.6 billion mobile subscriptions worldwide, more than the number of people on Earth. The mobile phone, in less than half a century, has gone from a brick-sized luxury for the rich to a pocket computer that more than 80 percent of the world’s adults carry every day. The story of how a network of radio towers, a stack of cellular protocols, and a remarkably successful design converged to make this possible is, in retrospect, one of the most consequential technology stories of the late twentieth and early twenty-first centuries.

The pre-cellular era: 0G and 1G

The first mobile telephone networks, in the 1940s and 1950s, were not cellular. They used a single high-power transmitter to cover a large area, and the capacity was limited to a few dozen simultaneous calls. The Mobile Telephone Service (MTS) in the US, launched in 1946, supported perhaps 5,000 customers in a single city. The system was a luxury: a car-mounted phone with a separate handset, a hefty monthly bill, and a long waiting list for a connection. The system was, in short, a niche product, not a mass-market technology.[1, 2, 9]

The cellular concept was proposed by Bell Labs engineers Douglas Ring and Rae Young in 1947. The idea was to divide the service area into small cells, each served by a low-power transmitter, and to reuse the same frequencies in non-adjacent cells. The capacity of the system scaled linearly with the number of cells, and the cost of the system scaled sub-linearly. The technical challenge was the handover — the smooth transfer of a call from one cell to the next as the user moved — and the first handover was demonstrated by Bell Labs in 1970. The first commercial cellular network, the NTT system in Tokyo, was launched in 1979, followed by the Nordic NMT system in 1981 and the US AMPS system in 1983.[1, 2, 9]

The first generation, 1G, was analogue. The dominant standards were AMPS in the US, NMT in the Nordic countries, TACS in the UK, and C-450 in Germany. The handsets were bulky (the Motorola DynaTAC 8000X, launched in 1983, weighed nearly a kilogram and cost $3,995), the calls were insecure (anyone with a radio scanner could listen in), and the capacity was limited (a few hundred thousand subscribers per city). The technology was, however, the first mobile telephone service that was portable, and it established the cellular concept as the foundation of everything that followed.[1, 2, 9]

2G and the GSM revolution

The second generation, 2G, was digital. The dominant standard, GSM (Global System for Mobile Communications), was developed by the European Conference of Postal and Telecommunications Administrations (CEPT) in the 1980s and first deployed in 1991 in Finland. GSM used time-division multiple access (TDMA) to allow up to eight users to share a single frequency channel, and used digital modulation (Gaussian minimum-shift keying) to provide better voice quality and more efficient use of the spectrum than the analogue 1G systems. The GSM standard also specified the SIM card, a small smart card that stored the subscriber’s identity and credentials, and that could be moved between handsets. The SIM card was, in retrospect, a critical innovation: it made mobile telephony a global, interoperable service, and it enabled the later boom in international roaming.[2, 3, 10]

The 2G era introduced SMS (Short Message Service) text messaging, which was originally designed as a side feature for signalling but quickly became a global cultural phenomenon. The first SMS was sent in December 1992, and by 2010 more than 6 trillion SMS messages were being sent per year. The popularity of SMS was, in part, a function of the cost (a flat rate per message, regardless of destination) and the convenience (a quick way to communicate without a phone call). The dominance of SMS has since been replaced by instant-messaging apps (WhatsApp, iMessage, WeChat, Signal) running over the mobile data network, but the cultural legacy remains.[2, 3, 10]

The 2G era also saw the rise of competing standards. CDMA (Code-Division Multiple Access), developed by Qualcomm and adopted in the US and parts of Asia, used a different multiple-access scheme (spread spectrum) and provided higher capacity than GSM. PDC (Personal Digital Cellular), developed in Japan, was used exclusively in Japan and was eventually phased out in favour of 3G. The 2G era ended in the mid-2000s, with most operators upgrading to 3G, but 2G networks are still operating in some countries and remain the primary mobile technology in parts of Africa and South Asia.[2, 3, 10]

3G and the mobile internet

The third generation, 3G, was defined by the ITU’s IMT-2000 standards, and was the first generation designed from the outset for data as well as voice. The dominant standard, UMTS (Universal Mobile Telecommunications System), was developed by the 3GPP (3rd Generation Partnership Project) and deployed worldwide from 2001 onwards. UMTS used wideband CDMA, with a 5 MHz channel, and supported peak data rates of 2 Mbps (in practice, more like 384 kbps). The competing standard, CDMA2000, was used in the US and parts of Asia, and was based on Qualcomm’s IS-95. The two standards were technically incompatible, and the global mobile industry split between them for most of the 2000s.[3, 4, 11]

The killer app of 3G was not the data rate, which was modest, but the smartphone. Apple’s iPhone, launched in 2007, transformed the mobile phone from a communication device into a pocket computer. The iPhone combined a multi-touch screen, a web browser, a music player, a camera, and an app store into a single device. The Android ecosystem, launched by Google in 2008, brought the same paradigm to a wider range of devices, and the global smartphone market grew from a few million units per year in 2007 to more than 1.5 billion units per year by 2015. The combination of the iPhone and Android, and the 3G data networks that supported them, was the most consequential technology shift since the introduction of the personal computer.[3, 4, 11]

The 3G era also saw the rise of mobile data as a mass-market product. The first mobile data services, in the late 1990s and early 2000s, were expensive and slow (a few cents per kilobyte, with rates measured in tens of kbps). The 3G era saw the introduction of flat-rate data plans, which made mobile internet access affordable for the first time. The shift, in retrospect, was the most important economic change in the mobile industry since the introduction of the cellular concept, and it enabled the entire app economy — from social media to ride-sharing to mobile banking — that we now take for granted.[3, 4, 11]

4G and the smartphone era

The fourth generation, 4G, was defined by the ITU’s IMT-Advanced standards, and was implemented as LTE (Long-Term Evolution) in most of the world. The peak data rate was 100 Mbps to 1 Gbps, the latency was 10–50 milliseconds, and the architecture was all-IP (no separate voice and data networks). The first LTE networks were deployed in 2009 in Norway and Sweden, and the technology has since been deployed in more than 700 networks in more than 200 countries. The successor, LTE-Advanced (LTE-A) and LTE-Advanced Pro, pushed the peak data rate to 3 Gbps and added features like carrier aggregation, higher-order MIMO, and small cells.[4, 5, 12]

4G made the mobile internet the default. Mobile video, which had been a niche application on 3G, became a mass-market product on 4G. The launch of Netflix’s streaming service in 2007, the launch of YouTube’s mobile app in 2011, and the launch of TikTok in 2016 were all enabled by 4G. Mobile gaming, mobile cloud services, and mobile-first social media (Snapchat, Instagram, TikTok) all became mainstream on 4G. The smartphone, in turn, became the dominant computing device of the decade, replacing the personal computer for many everyday tasks. The average US adult, in 2024, spends more than four hours per day on their phone — more than on television, and more than on any other single activity.[4, 5, 12]

The 4G era also saw the rise of the app economy. The Apple App Store, launched in 2008, and the Google Play Store, launched in 2008 as well, created a new distribution model for software: developers could write an app, submit it to the store, and reach billions of users worldwide. The model spawned a wave of new companies (Uber, Airbnb, Instagram, WhatsApp, TikTok) and transformed existing industries (retail, media, transportation, hospitality). The app economy, in 2024, generates more than $500 billion in annual revenue and is one of the most important economic forces in the world.[4, 5, 12]

5G and the new use cases

The fifth generation, 5G, was defined by the ITU’s IMT-2020 standards, and is being deployed worldwide from 2019 onwards. The headline features are peak data rates above 10 Gbps, latency below 5 milliseconds, and the ability to support up to a million devices per square kilometre. The new use cases enabled by 5G are not just faster smartphones but fixed wireless access (using 5G as a home internet connection), industrial IoT (sensors and robots in factories), autonomous vehicles (vehicle-to-everything communication), remote surgery (low-latency video and control), and augmented reality (high-bandwidth, low-latency streaming of 3D content). The deployment is uneven: the US, China, South Korea, and parts of Europe have wide 5G coverage, but many countries are still in the early stages.[5, 6, 13]

5G uses three different frequency bands. Low-band 5G (below 1 GHz) provides wide coverage but modest speeds (50–250 Mbps), similar to good 4G. Mid-band 5G (1–6 GHz, particularly the 3.5 GHz band) provides the best balance of coverage and speed, with peak rates of 1–3 Gbps and typical rates of 100–500 Mbps. High-band 5G (24–47 GHz, the “millimetre wave” bands) provides very high speeds (5–10 Gbps) but very limited coverage (a few hundred metres per cell, blocked by walls and foliage). Most operators have focused on mid-band 5G, with high-band deployed in dense urban areas and low-band used for wide-area coverage.[5, 6, 13]

The use cases beyond the smartphone are, in 2024, still emerging. The most successful is fixed wireless access: in the US, T-Mobile and Verizon have signed up millions of subscribers to 5G home internet, particularly in areas where fibre-to-the-home is not available. The second is industrial IoT: factories in Germany, China, and the US are using 5G to connect sensors, robots, and autonomous vehicles. The third is private 5G networks: enterprises (ports, mines, hospitals, factories) are deploying their own 5G networks, with their own spectrum, to provide coverage in areas that the public networks do not reach. The fourth, still in early development, is vehicle-to-everything (V2X) communication, which uses 5G to allow cars to talk to each other and to the infrastructure. The transformation, when it comes, will be slower than the smartphone revolution, but it may be larger.[5, 6, 13]

The future: 6G, foldables, and the end of the smartphone

The sixth generation, 6G, is in early research, with the first deployments expected in the early 2030s. The key features are likely to be integration with satellite networks (for truly global coverage, using LEO constellations like Starlink), terahertz frequencies (for multi-hundred-gigabit data rates in dense urban areas), and AI-driven network management (for self-optimising networks that adapt to traffic patterns in real time). The use cases, in addition to faster smartphones, are likely to include holographic communication, immersive extended reality, digital twins, and the Internet of Everything. The transition from 5G to 6G will be, in many ways, a transition from a network optimised for the smartphone to a network optimised for a world of connected devices.[6, 7, 14]

The smartphone form factor, meanwhile, is showing signs of strain. Global smartphone shipments have been flat or declining since 2017, and the new growth areas are wearables (smartwatches, earbuds, smart glasses) and other form factors (foldables, rollables, embedded devices). The foldable smartphone, pioneered by Samsung and Huawei in 2019, has become a small but growing segment of the market, and the technology is improving rapidly. The next decade of mobile telephony will be, in significant part, a story of the smartphone’s gradual replacement by a constellation of always-connected devices — watches, glasses, earbuds, cars, appliances — each with a different form factor and a different use case.[6, 7, 15]

The other long-term trend is the integration of mobile and satellite networks. The 3GPP standards body is now working on specifications for non-terrestrial networks (NTN), which will allow standard 5G and 6G handsets to connect directly to satellite constellations. The integration will, in the long run, eliminate the need for separate satellite phones and provide truly global coverage. The combination of LEO constellations (Starlink, OneWeb, Kuiper, Guowang) and standard mobile handsets will, in the next decade, make mobile telephony truly global — a phone that works anywhere on Earth, at any time, with a single subscription. The cellular concept, in other words, is being extended to the whole planet.[6, 7, 16]

Comparison: generations of mobile telephony

Generation	Era	Modulation	Multiple access	Peak data rate	Killer app	Approx. global subscribers (peak)
1G	1980s	Analogue FM	FDMA	—	Portable voice	~20 million
2G (GSM)	1990s	GMSK	TDMA	~64 kbps	SMS	~1 billion
3G (UMTS)	2000s	QPSK / 16-QAM	W-CDMA	~2 Mbps	Mobile internet, smartphone	~2 billion
4G (LTE)	2010s	Up to 256-QAM	OFDMA	~1 Gbps	Mobile video, app economy	~5 billion
5G	2020s	Up to 256-QAM	OFDMA + flexible numerology	~10 Gbps	FWA, IoT, V2X	~2 billion (growing)
6G	2030s (planned)	Higher-order QAM, terahertz	OFDMA + AI-driven	~100+ Gbps	Holographic comms, IoE	TBD

Key numbers

• ~8.6 billion: mobile subscriptions worldwide (2024).
• ~5 billion: unique mobile subscribers worldwide (2024).
• ~1.2 billion: 5G subscriptions worldwide (2024).
• ~4 hours: average daily smartphone use in the US (2024).
• ~$500 billion: annual revenue of the app economy (2024).
• ~$1.5 trillion: annual mobile network operator revenue (2024).
• 1979: year of the first commercial cellular network (NTT, Japan).
• 1983: year of the first US cellular network (AMPS, Chicago).
• 2007: year of the iPhone launch.
• 2008: year of the Android launch.

References

1. Wikipedia, “Cellular network.” (Standard reference on the cellular concept and its history.) https://en.wikipedia.org/wiki/Cellular_network
2. Wikipedia, “1G.” (Standard reference on the first generation of mobile telephony.) https://en.wikipedia.org/wiki/1G
3. Wikipedia, “2G.” (Standard reference on the second generation of mobile telephony, focused on GSM.) https://en.wikipedia.org/wiki/2G
4. Wikipedia, “3G.” (Standard reference on the third generation of mobile telephony.) https://en.wikipedia.org/wiki/3G
5. Wikipedia, “4G.” (Standard reference on the fourth generation of mobile telephony, focused on LTE.) https://en.wikipedia.org/wiki/4G
6. Wikipedia, “5G.” (Standard reference on the fifth generation of mobile telephony.) https://en.wikipedia.org/wiki/5G
7. Wikipedia, “6G.” (Standard reference on the sixth generation of mobile telephony, in research.) https://en.wikipedia.org/wiki/6G
8. Wikipedia, “Foldable smartphone.” (Standard reference on the foldable smartphone form factor.) https://en.wikipedia.org/wiki/Foldable_smartphone
9. Wikipedia, “Mobile Telephone Service.” (Standard reference on the pre-cellular mobile telephone service.) https://en.wikipedia.org/wiki/Mobile_Telephone_Service
10. Wikipedia, “GSM.” (Standard reference on GSM, the dominant 2G standard.) https://en.wikipedia.org/wiki/GSM
11. Wikipedia, “IPhone.” (Standard reference on the iPhone, the device that defined the smartphone era.) https://en.wikipedia.org/wiki/IPhone
12. Wikipedia, “LTE (telecommunications).” (Standard reference on LTE, the dominant 4G standard.) https://en.wikipedia.org/wiki/LTE_(telecommunications)
13. Wikipedia, “IMT-2020.” (Standard reference on the ITU’s 5G standards.) https://en.wikipedia.org/wiki/IMT-2020
14. Wikipedia, “Non-terrestrial network.” (Standard reference on 5G/6G integration with satellite networks.) https://en.wikipedia.org/wiki/Non-terrestrial_network
15. Wikipedia, “Samsung Galaxy Z series.” (Standard reference on the Samsung Galaxy Z foldable phone series.) https://en.wikipedia.org/wiki/Samsung_Galaxy_Z_series
16. Wikipedia, “Terahertz radiation.” (Standard reference on terahertz frequencies, expected to be used in 6G.) https://en.wikipedia.org/wiki/Terahertz_radiation