I want to build a device that is expected to consume very little energy.

I don't know if it will be better to have it compatible with 5G or just leave to be compatible with 4G.

So, do the 5G consume less power than the 4G for very low transfer rates? my device will send a at most 5MB per minute.

I have heard also somewhere that with 5G the devices will be able to choose what is best connection, that is, will be able to automatically switch to 4G, 3G or even 2G if the requirements won't be too demanding.

My project is to make smartwatch like the thor-5, which has localization technology and 3G capability.

But with my smartwatch, I will just track the location and be connected to the internet to send its coordinates to the server and better determine its position.

I have to decide if I will implement it with 5G or other technologies to better optimize its energy consumption.

I think that for all my needs GPRS (2G) will be enogh, but anyway, maybe 5G will be better.

My smartwatch will have also WiFi 6 and bluetooth 5.1.

Btw, will it worth putting a more modern SoC/SiP ?

I plan my smartwatch to have google wear OS or android go.

  • \$\begingroup\$ um, what kind of 5G device are you even thinking about? And I wouldn't call 5MB per minute a very low transfer rate for a device consuming very little energy. \$\endgroup\$ – Marcus Müller Jun 10 at 16:53
  • \$\begingroup\$ Aynway, this is way too broad – we don't even know what you mean with "very little energy". You'll need to give us way, way more information on what you're intending to build. \$\endgroup\$ – Marcus Müller Jun 10 at 16:54
  • \$\begingroup\$ As written, this question seems to be fishing for a generalized comparison between cell standards/request for what is best, which is very broad, but I think it could be edited down into a specific power comparison question. A relative power comparison between 4G and 5G standards at a given data rate (5MB/min) seems to be a specific question IMO. \$\endgroup\$ – Chris Fernandez Jun 10 at 17:02
  • 2
    \$\begingroup\$ @ChrisFernandez on the minute scale? not really! If I can get the data out in 1s within that minute and then sleep for 59s, the energy per bit of the standard and hardware doesn't matter as much. If we're talking about a modem that has to stay on the full minute, anyway, well, you need to do very different calculations. \$\endgroup\$ – Marcus Müller Jun 10 at 17:10
  • \$\begingroup\$ @Marcus Müller, thank you very much for the remarks, i see that i have made a very generalized question. i have updated my question. \$\endgroup\$ – user2340356 Jun 11 at 0:27

Since you require low data rates and a lower power consumption, why not look into LPWAN(Low Power Wide Area Network) Technology.

3G-PP has proposed 2 LPWAN technologies, LTE-M and NB-IoT which can be used to reduce power consumption and increase range at lower data rates. LTE-M works on existing LTE towers and hence you can be using it wherever there is an LTE coverage.

There are many options such as LoRa, Sigfox, RPMA, etc that you could look into for such applications


I think that for all my needs GPRS (2G) will be enogh, but anyway, maybe 5G will be better. My smartwatch will have also WiFi 6 and bluetooth 5.1.

Your design so far just consists of throwing the latest and greatest standards into one pot in stirring.

These standards are so new, there's not really any commercially available system that you could even buy for BT5.1 as far as I know. WiFi 6 (which is an incredibly stupid marketing name), better known as IEEE802.11ax is clearly something you'd want in modern high-rate devices, but on a smart watch, the MIMO features simply can not work, due to size constraints.

So, instead of just throwing together standards and thinking that'll be good, start researching what they actually technically mean and what their benefit is.

Just like you do for the power usage of 5G vs 4G, which is an excellent question!

Btw, will it worth putting a more modern SoC/SiP ?

Well, considering you won't get IEEE802.11ax nor BT 5.1 with the SoC that you (unlike Samsung) can buy today, yes, there will be no other way.

I have heard also somewhere that with 5G the devices will be able to choose what is best connection, that is, will be able to automatically switch to 4G, 3G or even 2G if the requirements won't be too demanding.

That's generally more or less true. A modern communications device will typically be backwards compatible. That's typically necessary for coverage reasons!

So, the downer first:

"5G" doesn't mean all that much to customers. The world actually just started auctioning off the spectrum necessary to actually do "5G New Radio", so while you can get phones that have the 5G software stack (most of a modern UE is software defined radio and a lot of data handling done in software with accelerators), you can't buy much New Radio hardware so far, and you'll have to find a network operator that has such a network already running. For that to happen, you'll need to find a country where there's 5G spectrum allocations already happening.

So, while the 5G software side most definitely contains clever enhancements, the difference to you would be small.

That is:

There's LTE NB-IoT (LTE Narrowband IoT) and LTE Cat-M1, both of which are designed for machine-to-machine communications at low rates with low power consumption. Could fit your bill very well!
Your first estimate of 5MB/min was worlds off: you can get at most one GPS fix per second, and you really don't need much cleverness to see that there's at most say 16 bits of difference between consecutive GPS positions then, which leaves you with less than 1 kB per minute. That could be well-covered with much lower rates.

These standards were introduced in LTE Release 15 (I think), which "technically" is 5G, but not marketed as such, because it's not technology targeted at a consumer audience, but engineers. The chips for these standards aren't compatible with 2G, 3G, 4G or the full-speed 5G modes at all – they're doing one job, and that is delivering low-rate sensor data. Coverage, at least in Germany, seems to be pretty good if you pick the right network operator.

Same applies to you having WiFi: that eats a lot of battery, and your user doesn't really profit from it! So, having more features isn't actually good. Reduce your feature set to something your user actually wants.

Generally, your specs simply don't line up with your use case:

If you want your GPS to be running all the time, bad news, your watch battery will be empty within a few hours. GPS' power consumption dwarfs most other peripherals.

You personally probably won't be building an overly feature-rich smartwatch: That requires a lot of engineering and expensive technology that you simply don't get access to. For example, the smartwatch you've referred to supports LPDDR3 RAM – an interface that means you'll have to run many controlled impedance signal lines from the SoC to the RAM chip, which means your PCB will have very many layers. In contrast, a simpler, not-so-feature-rich device could use one of the simpler mediatek chips that integrate RAM and thus have far, far fewer external connections and hence could be much simpler routed and most importantly, without having access to >100,000$ in oscilloscopes.

Start by really writing down your use case. Then, derive technical specs from that, as detailed as the use case allows: start with data rates, and a minimal viable battery life time.

From that, derive which communication interfaces would actually benefit the use case (instead of just being "nice to have"). Then make a market-based decision on what you'll actually equip your device with.

Like it is now, you're starting backwards: You've heard of so many cool interfaces and want them all. But having a 5G radio and 802.11ax doesn't make a good smartwatch.


This is a matter of actual frequency and range.

The higher the frequency you use, the less range you will have and to get to the required range you will have to boost-up your power.

The lower the frequency, better the coverage - means less power consumption.

Also, the penetration through various materials is also lesser for a higher frequency.

A device automatically selecting between 2/3/4/5G will not be power-efficient as it will keep switching to the best connection available.

So since your objective is to save power, you should go for the lowest-G option that gives you sufficient data transfer rate. 5MB/minute may be a too high for 2G, but 3G will certainly handle it.

  • \$\begingroup\$ that's not actually true. 2G uses more power per bit than 3G, for example. And whilst the "longer wavelengths have less free space path loss and material attenuation" is true, 2G has no such things like indoor picocells. So, coverage is not just a function of frequency, but much more of network design. \$\endgroup\$ – Marcus Müller Jun 11 at 6:21
  • \$\begingroup\$ You statement is partially correct. 3G has a higher battery drain, even if it actually uses less Watts per downloaded Kilobyte compared to 2G. 3G is much better for heavy data usage, and will not use much more battery if the 3G signal is strong. If the signal is poor or fluctuating, it will drain your battery as much as twice as fast compared to 2G. Talk time is considerably less than 2G, however, standby drain is about the same. Overall, under typical conditions in suburban areas, you should expect about 2/3 of the 2G battery life. Point is: to get transfer you 1st need proper coverage. \$\endgroup\$ – Overmind Jun 11 at 6:41
  • \$\begingroup\$ Give all that and the bandwidth requirement, I maintain my recommendation to use 3G. \$\endgroup\$ – Overmind Jun 11 at 6:42
  • \$\begingroup\$ talk time is totally irrelevant to the problem at hand: OP is not planning to use his watch to make calls. What matters is how much energy a complete system would have to use to send out occasional packets of a few bytes, so battery usage would look a lot more like the device was in standby than what it'd look like if someone was constantly talking. Point being: in typical Urban, you get few 2G cells, which means high power consumption on average, but very many 4G cells, which, albeit for the same distance maybe a bit more power hungry per bit, will have it easier. \$\endgroup\$ – Marcus Müller Jun 11 at 6:45
  • \$\begingroup\$ and coverage: the US and EU are shutting down their 3G networks in the next few years, or already have (unlike 2G and 4G/5G, which will still be available). So, coverage-wise, I wouldn't recommend 3G. \$\endgroup\$ – Marcus Müller Jun 11 at 6:46

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