Get email delivery of the Cadence blog featured here
You can't read anything about technology these days without reading about 5G. But before there was 5G, there was 4G. And before that 3G, 2G, and 1G. A 0G even.
For the next few Thursdays, Breakfast Bytes will be taking a look at the history of mobile. If we can have Taco Tuesdays, we can have Telecom Thursdays. Served with guacamobile.
There had been "mobile" phones around before cellphones. But these were 50-pound vehicle-mounted behemoths that required selecting a frequency, and those frequencies could not be shared. As a result, a city the size of St Louis could have...count'em...three simultaneous phone calls across the entire city. These were called radio-telephones at the time, starting as early as 1946 just after the war, and sometimes today are referred to as 0G.
The first generation of cell-phones, like the first generation of anything, wasn't actually called 1G until later, I think around the time 3G came along. I don't remember 2G ever being called 2G either, it was just "digital" in comparison to 1G. From that, you could guess, correctly, that 1G was analog. Each phone call was allocated a frequency and transmitted and received in its assigned frequency (in one direction at a time). The carrier was modulated just like a radio station transmission and was tuned by moving the equivalent of the tuning knob just like a normal radio. There was no encryption so anyone with a radio receiver that covered the correct frequency band could listen to calls. Since each call was assigned to a frequency band, and lots of calls could be handled at the same time on different frequencies, this was known as FDMA, or Frequency Division Multiple Access.
The standard in North America (both US and Canada) was known as AMPS (for Advanced Mobile Phone Service). But many large countries in the world had their own standards and required basestations and handsets to be manufactured to that standard. There was very little international interoperability. For example, AMPS was also used in Israel, Australia, Singapore, and Pakistan. But go anywhere else and you were out of luck. But remember, these were mostly carphones. But not all of them. Gordon Gecko famously had one of these early "portable" phones in the movie Wall Street:
Carphones had a couple of advantages over handheld cellphones. The first was that cars have big batteries and an alternator and so never run out of battery. The second is that the handset does not have to contain the main electronics, so it can be small and comfortable. The bulky, heavy electronics can be hidden away in the trunk or, as in the case of the carphone I had towards the end of the 1G era, behind a panel in front of the passenger seat of my Miata.
Some of the basic ideas of cellphones were present though. Mobile phones were usually called cellphones back then. The name came from the roughly hexagonal cells (like in a beehive) with a basestation at the center of each. As the phone moved, the system would monitor the signal strength at the basestation communicating with the phone. But it would also check the signal strength at the other neighboring basestations. If the signal was stronger at another basestation, then the call would switch cells. This required the new basestation to have a frequency band available, otherwise the call was unceremoniously dropped. How did the phone get told the new frequency? AMPS used what is called in-band signaling. This transmitted modem tones to the phone in the frequency band that it was using for voice. These messages instructed the phone to switch to a new frequency and a new basestation. I think these were blanked out, on AMPS, but on some other systems you could hear a burst of modem. Planning a network required careful allocation of frequencies since neighboring cells could not use the same frequency or they would interfere. But towers further away could, just as radio stations in different cities can use the same FM frequency.
Of course, all that assumes you are on a call already. If you are not, then you don't have a frequency band for the basestation to do in-band signaling. There was another channel at each basestation known as the paging channel. When a phone was not on a call, it would listen for modem tones on the paging channel (which was obviously shared among all the potentially many phones in a cell that were not making a call).
I said above that generally different countries had different standards. In the UK it was TACS, in Germany (and some other countries) C-450, in France Radiocom 2000, and so on. In Japan, there were three standards, all developed by NTT, and as if that wasn't enough, their competition used a version of AMPS.
But one area that did not was Scandinavia (actually, Scandinavia doesn't include Finland technically, so I should say the Nordic Countries really). Norway, Sweden, Denmark, and Finland decided it would be silly to have four non-interoperable standards and created Nordic Mobile Telephone (NMT). This was actually the first cell-phone service in the world and started in October 1982. AMPS, in North America, only opened for business a year later in October 1983. Having a common standard was also important because, unlike the US and Pakistan, a lot of people really did drive from one Scandinavian country to another. Another key thing about NMT was that the standards were free and open and so anyone could build equipment to the specification, driving down prices, and driving up growth. As a result, by 1985, NMT was the largest network in the world. Many other countries adopted the standard since they could easily acquire equipment. Two companies who grew up in this era in Scandinavia were Ericsson (in Sweden, and already a telecommunications company) and Nokia (in Finland and a...forest products company).
The Scandinavian experience turned out to be very influential. Everyone who already used NMT was going to use whatever NMT came up with. The big European countries were not going to let themselves be bossed around by the Nordics, so they pushed for a European wide standard. A special working group was set up. Since French is the official international language for post and telecommunications, it was called the Groupe Spécial Mobile ("mobile special group" in French). Look at those initial letters. GSM. Sound familiar?
Coming up soon, the story of 2G in general and GSM in particular.
Sign up for Sunday Brunch, the weekly Breakfast Bytes email.