3G and 4G: The Internet Arrives

14 May 2020 • 7 minute read

In posts over the last couple of weeks, I covered 1G and 2G mobile:

Today it is the turn of 3G, 3.5G, and 4G. I'll omit the angels-on-a-pinhead wars about whether the first LTE phones were truly 4G or should be called 3.95G. There have been similar arguments about where the line between 4G and 5G should be drawn, with AT&T clearly jumping the gun and calling LTE-advanced 5G. The 3GPP that owns the standards defines what can be called what generation, and the sort of people who work at those organizations get upset when the marketing people at mobile operators ignore them. It's not completely irrelevant. If you have an xG phone then you expect it to work on an xG network in any country these days. You (if you are a normal man-in-the-street and that street is not University Avenue in Palo Alto) have never heard of any of the acronyms that pepper these posts.

3G

At the beginning of the 3G area, cellphones were still used primarily for voice calls, with teenagers, in particular, using their phones mostly for texting. Phones still only had a numeric keyboard, so texting required multiple presses per letter. There was a rudimentary data capability slapped onto the side of GSM called GPRS, and an upgraded version called EDGE. But the datarates were too low for internet access on phones to be commonplace. In fact, at this point, data was so slow that it was free. A typical phone plan would provide a certain number of voice minutes, plus a certain number of text messages. If you went over those limits, you paid more. Data was something you got along with those voice minutes, in the same way today that voice is thrown in along with those data plans.

The world (apart from Japan) was thus pretty much in either the cdmaOne camp or the GSM/EDGE camp. For 3G, the CDMA camp moved to CDMA2000 and the GSM camp moved to a technology they called UMTS for Universal Mobile Telephone System. This was based on CDMA using a technology called Wideband-CDMA or W-CDMA (sometimes WCDMA). Despite the fact that both these technologies were CDMA-based, they were still incompatible.

One advantage/disadvantage of UMTS is that it required wider channels. The disadvantage was that meant a new spectrum was required, which delayed rollout, especially in the US. The advantage was that it higher data rates when it did become available. 384kbps for UMTS versus 153kpbs for CDMA2000.

In 2007, the iPhone was launched and we entered the smartphone era. As I said in the earlier post, the iPhone (what we now call the iPhone 1) was 2.5G and supported just GSM/EDGE. AT&T had made a deal that the iPhone would only be available on their network at first but iPhone was not required to live in some sort of walled garden as the other carriers insisted on. Of course, iPhone was an instant huge success, which caused AT&T problems. It didn't support 3G but AT&T wanted to build out more of their 3G network, not go back and backfill 2.5G to cope with the iPhone demand. That became manageable when the iPhone 2 supported 3G and AT&T was just faced with the "problem" of building out their network fast enough to cope with the exploding demand.

3.5G

The CDMA camp launched a technology called EV-DO which is EVolution Data Only, giving 1Mbps (at least in theory — just like today the marketing number doesn't really match day-to-day experience). This leaped over UMTS which was still deploying really slowly. In fact when iPhone launched, only about 20% of GSM (2.5G) users had moved to 3G. The fact that iPhone didn't initially support 3G, only 2.5G, didn't help that statistic. Soon after, GSM launched their next improved datarate (and new name) HSDPA for High-Speed Downlink Packet Access followed soon after by HSUPA (High-Speed Uplink Packet Access. The CDMA camp when through two revisions of EV-DO. Then GSM introduced HSPA+ (at least without a new name this time) with theoretical speeds of up to 100mbps.

So that was the landscape at the end of 3G. New incremental standards were rolled out regularly, with the two camps leapfrogging each other. But the effect for users was that internet access gradually got more and more responsive. The complexity of all the standards and frequency bands were hidden from users by the increasingly smart smartphones (smarterphones?) which could take advantage of whatever technology was available and simply display "3G" to the user.

4G

It looked like 4G was going to be like 3G with two main competing standards. There was even a third entrant called WiMax (Worldwide Interoperability. for Microwave Access). This was originally intended to be a broadband wireless technology to compete with cable and ADSL for supplying internet access, with datarates up to 30-40Mbps for mobile access and up to 1Gbps for fixed access. Qualcomm had a new generation of CDMA being readied. The GSM upgrade path was to a technology called LTE (for Long Term Evolution...3GPP really needs to hire better good naming consultants).

And then a miracle happened.

Everyone got behind LTE. The latest WiMax standard, for example, is compatible with (some) LTE. Verizon in the US, which had been in the CDMA camp, actually rolled out their 4G LTE network before AT&T who had been in the GSM camp ever since they shut down D-AMPS. Qualcomm switched its development to the same standard. Suddenly, out of nowhere, the entire industry was behind the same standard across the whole world.

This is great for consumers, of course. Outside of weirdos like the people who read Breakfast Bytes, nobody cared (or understood) the difference between CDMA and UMTS anyway. Even the carriers didn't care, they just wanted cheap equipment and lots of phone contracts.

During the 3G and 4G periods, or the smartphone era which are pretty much the same thing, people's use of phones changed and so did carrier business models. People rarely made phone calls, and with the increasing prevalence of spam phone calls, people rarely answered calls from unknown numbers. Phone contracts switched from being a number of minutes of voice and limited data, to large (or unlimited) data and all the calls that you want. In fact, 4G doesn't support voice at all. It is a pure data standard. Voice is handled either by a voice-over-IP technology (so similar to Skype) called VoLTE, or by falling back to use the 3G network for voice calls. This works because 4G phones generally have to support 3G and 2G for times when 4G is not available. Another change is that until the smartphone era, phones were getting smaller: she who had the smallest phone wins. But now they are getting bigger again.

LTE actually uses a few technologies that it is worth at least knowing the name of:

It uses OFDMA which is Orthogonal Frequency Division Multiple Access, with each user being assigned different subsets of small frequency bands
It uses MIMO which is multiple-input-multiple-output, being able to use multiple antennas to take advantage of reflections to improve data rates
It uses carrier aggregation which is having multiple channels to the basestation when there is available extra capacity
It has a much more efficient radio interface using QAM (quadrature amplitude modulation) at increasingly high levels. If you know what PAM4 Is in SerDes (2 bits per symbol) there are QAM schemes up to 64 bits for each transmitted symbol that I find amazing can be resolved.

In theory, you can get 1Gbps. But your mileage may not just vary, it simply won't reach those levels in any real situation.

The LTE protocols seem to be supported in all countries, even though some countries such as Japan and China have other protocols (and, of course, for backward compatibility have to support the 3G protocols that were, and to some extent still are, in use there).

5G

That brings us up to today, on the dawn of 5G. I'm not going to cover that here, I've already covered it extensively:

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