There's a common misconception that 5G specifically means you need to use millimeter wave (very high-band) networks. 5G can be on the same frequency as 4G, and it is more efficient than 4G - so with greater efficiency, it's easier to get usable output from that signal than with 4G. The signals will go "as far" regardless of 3G/4G/5G assuming they're broadcasted at the same frequency and power level, but the device being able to use it is a different story.

The reason 2G and 3G can sometimes reach further than LTE is for a similar reason - because it's easier to "hang onto" a 2/3G signal. The reason it's easier though is different - not because 3G is more efficient, but because it's less complex. This reddit thread[0] explains it better than I can, so I'll paste a comment from it here:

>>> The modulation scheme (how the digital "data" is packed into the "analog" wave to transmit it over the air) is simpler for [2G], which requires a lower wave quality to decode. It's the same reason you are more likely to get an [2G] signal farther away than LTE

Note that the reason 3G might be "faster" is probably due more to the congestion issue I talked about before - when the LTE network is oversubscribed, meaning too many people are connected to it and are slowing it down, sometimes dropping back to 3G (which very few people are connected to in 2021) can lead to you fighting less over your data.

[0] https://www.reddit.com/r/tmobile/comments/lwwkrl/when_was_th...

But how much is 5G faster than LTE in same frequency usage? Higher QAM would improve throughput but only on great place near the station.

Better beamforming means that at the same distance from the BS you have better signal quality, so you can use higher QAM.

True, millimeter wave bands, introduced in 5G, don't go as far as 4G. But those bands are in the 5G standard additionally to the lower bands similar to 4G, and are beneficial in places like busy airports, train stations and urban areas. 5G does not mandate to only use the millimeter wave bands (or, for the mater of act, to use them at all).

So in rural areas 5G signals would still use frequencies similar to 4G,so the more efficient use of spectrum will improve coverage and speed.

Regarding the observation that sometimes 3G signals are better than 4G - that might as well be because 4G has problems with congestion when many clients are connected to the same base station. One of areas which also 5G is also improving.

5G is several parts. The high frequency, hugh bandwidth stuff doesn't go far.

The same as existing mobile frequency stuff has about the same penetration as existing service, but because its more efficient, it allows towers to increase power to expand their coverage area. Generally towers will modulate their output power to reduce coverage when congested, hoping devices will attach to other towers; works well when there's enough towers with overlapping coverage, but not as well when towers are sparse.

It doesn't have to be purely power either, antenna angle makes a big difference, and phased antennas mean you can change effective angle without mechanically changing the angle.

5G is just instructions on how devices should talk over radio waves. The waves the devices decide to talk over very dramatically. On the short-range end, they can talk on 30-60ghz bands; these bands have lots of room to talk, but they’re hard to hear, especially through walls or long distances. On the other end, they can talk on frequencies as low as <600mhz. These are great at penetrating barriers (they’re probably what you use in the middle of nowhere) but there’s less room (free spectrum real estate available) to talk.

> FWIW, there are a number of places in my regular [pre-pandemic] travels where the 3G signal is better and even faster than 4G signals

This will rely heavily on the network design decisions made. Where I live, the digital TV switchover happened after LTE buildout was well on it's way, so all those juicy 700 MHz bands went to LTE. I literally can't remember the last time I saw my phone on 3G here, even out in the countryside with marginal coverage/dropouts. It's been at least 4 years.

The thing that is confusing is two things are wrapped up together as "5G": (a) the actual 5G standards, and (b) the spectrum that is used. To add to the confusion, (b) is composed of frequency and bandwidth, and those are often different both between and within countries.

For instance, one of the biggest benefits of 5G is that channels (bandwidth) can be much wider, and several can be stacked together, which means more data can be transferred. But even though that can be done, there may not be enough spectrum at a specific frequency to be able to take advantage of that.

Then the high-band (millimeter wave) can have even more channels than the low- and mid-band 5G. But high-band doesn't travel far and it doesn't penetrate walls well.

If you want a good primer on it that is accessible, I recommend the regularly updated "What Is 5G?" article from Sascha Segan at PCMag.[1] I think he's the best journalist writing about 5G.

[1] https://www.pcmag.com/news/what-is-5g