The problem with early radio telephones
A radio telephone needs a channel, and early systems had very few. In the mid-twentieth century, a city-wide mobile telephone service used a single powerful transmitter on a hill or a tall building, which covered a large area but could carry only a small number of calls at once. If every channel was in use, the next caller simply waited. Some early systems supported only a few dozen customers in a whole city, and calls were often placed through an operator.
This is why mobile telephony was a service for a few, not a mass product, for several decades. The handset was only one part of the problem. The deeper issue was how to serve many people with a limited share of the radio spectrum.
The cell idea
The solution that became standard is the cellular system. Instead of one big transmitter, a region is divided into many small areas called cells, each served by its own base station with low power. Because the signal fades over a short distance, the same frequencies can be used again in cells that are far enough apart without interfering. Reuse of frequencies is the core idea: the same limited spectrum is used many times over, so capacity grows as the cells are made smaller.
Engineers at Bell Labs described the concept in the late 1940s, and it was developed there over the following decades. A cellular system needs several things that were hard to build at the time:
- Many base stations, connected to the wider telephone network.
- Handoff, in which a call moves from one cell to the next as the caller travels, without being dropped. This requires the system to measure signal strength and switch channels quickly.
- Tracking of phones, so the network knows roughly where to send an incoming call.
- Automatic switching, building on the exchange technology of the wired network, with more computing power in the switching centers, which improved greatly with the arrival of silicon chips.
First networks
The first commercial cellular networks arrived in the late 1970s and early 1980s, using analog radio. Japan’s NTT launched a system in Tokyo in 1979. The Nordic countries launched a shared system in 1981, which allowed users to travel between countries, a feature that was unusual. In the United States, the system known as AMPS was tested in the late 1970s and launched commercially in 1983 in Chicago. In Britain, analog services began in 1985.
These first-generation networks were popular but crowded, and the phones were expensive. A call could be overheard by someone with a suitable scanner. Different countries used different standards, so a phone from one country often did not work in another. The story of the first handset on these networks is told in the DynaTAC article, and the broader question of early firsts in the account of the first mobile phone.
Digital networks and GSM
The 1990s brought second-generation digital networks. Digital transmission used the spectrum more efficiently, improved voice quality, and made encryption and data services possible. In Europe, telecom operators and regulators agreed on a common digital standard, known as GSM. The first GSM networks began operating in 1991, and the standard was adopted far beyond Europe. Agreement on a shared standard made it easier for manufacturers to build phones at scale and for users to roam between countries.
Digital systems also made the short text message possible. The first text message is commonly dated to December 1992, in a test on a GSM network. At first, texting was a minor feature, but it became hugely popular in the following years, particularly among younger users and in countries where calls were costly.
Other standards existed alongside GSM, including digital systems in the United States and Japan, and for a time operators and users had to deal with competing technologies. Over time, networks tended to converge on a smaller set of standards.
Data and later generations
Third-generation networks, from the early 2000s, were designed to carry data more quickly, which made web browsing and email on phones more practical. Fourth-generation networks, from around 2010, carried video and apps at much higher speeds. Phones also took over some jobs of the older long-distance messaging systems, and eventually of camera phones and navigation devices. Fifth-generation networks started to be deployed in the late 2010s. Each generation used new radio techniques, and each needed new equipment at base stations, so rollouts took years and varied by country.
Throughout, the basic logic remained: small cells, reused frequencies, handoff and a link to the wider telephone and internet network. In recent years, small cells in cities and indoor coverage have been added to cope with demand, and some of the ties between phones and satellite services have begun to be explored.
How phones spread worldwide
Several things helped mobile phones move from a business tool to a worldwide product.
- Falling prices. As chips improved and volume increased, handsets and equipment became cheaper.
- Prepaid service. Paying for credit in advance, without a contract or credit check, opened the market to people who could not easily get a monthly bill.
- Places without landlines. In many regions, building a fixed telephone network to every home was costly and slow, while building towers was faster. For many people, a mobile phone was their first telephone.
- Shared standards. Common standards made large production runs and international roaming practical.
By the 2010s, the number of mobile subscriptions worldwide was in the billions, although a single person might hold more than one, so subscription counts and numbers of users are different things.
Beyond calls
Once networks carried data, the phone became a device for much more than talking. That change is covered in the history of smartphones, while this article’s focus is on the system that made the phone portable. A phone is, in a sense, one end of a large radio network that includes towers, switching centers and links to the wider world, and it is this network that turned a clever handset into a service used by most of the world.