Bluetooth Tethering

ShafterGT · October 3, 2019

So I'm currently in a steel building, like the big ass garage ones you can have built. You know the ones. They have some pretty good cell signal blocking properties. Probably something to do with the steel. Anyway, I have a wifi router inside so I'm still connected. I have a Galaxy S10e and and a Galaxy tab S5e. My phone connects to the wifi fine and it works about as well as a 12 year old router should. The Tablet on the other hand, is being difficult. It works on other wireless networks, but not mine. There was a problem with the launch version of this device, the wifi antenna had a problem where you could block the signal with your hand, kinda like the cell signal on the iPhone's from a few years ago. I don't have that problem, so I guess I have a revised version.

Anyway, I decided to just connect my tablet to my phone via bluetooth, and use bluetooth tethering. Like a hotspot, but cutting out the wifi signal part. I figure if the wifi antenna is defective or something, (which it isnt) then bluetooth connectivity is a suitable substitute. But when I go to settings on my phone, and make it a discoverable device, it won't allow me to turn on bluetooth tethering because my phone is connected to wifi. It says "Cant use bluetooth tethering while connected to wifi network." Am I doing this wrong? From what I can tell through about 10 minutes of research, I'm doing it right. So either Its wrong, or the functionality was removed at some point. Cant really think of why they would do that though.

LIGISTX · October 3, 2019

I would assume you can't tether wifi through bluetooth. That.... is a strange use case I doubt there is support for. I could be wrong, but that is something I would never have thought to even be a use case.

Basically, im not surprised it gives you that error. Also, I think the wifi and bluetooth antennas are usually the same, not even sure it COULD do this.

mtz_federico · October 3, 2019

I'm not sure if there is an Android app to do that, but by default with no app you can't do that on a phone.

On a laptop (Mac and Windows as long as they have Bluetooth) you can tether your phone via Bluetooth

ShafterGT · October 4, 2019

10 hours ago, mtz_federico said:

On a laptop (Mac and Windows as long as they have Bluetooth) you can tether your phone via Bluetooth

Exactly, so why would i not have that functionality here?

21 hours ago, LIGISTX said:

I would assume you can't tether wifi through bluetooth. That.... is a strange use case I doubt there is support for. I could be wrong, but that is something I would never have thought to even be a use case.

Not really sure of the point of this statement. You can tether a device to the master devices cell network, but not the wifi network. Im not sure why the network type would matter, the bluetooth signal should be the same no matter what.

21 hours ago, LIGISTX said:

Basically, im not surprised it gives you that error. Also, I think the wifi and bluetooth antennas are usually the same, not even sure it COULD do this.

If that were the case then i would think all WiFi enabled devices would also be Bluetooth enabled, although i could probably poke holes in that assumption myself if i felt like it.

Alex Atkin UK · October 4, 2019

3 hours ago, ShafterGT said:

Exactly, so why would i not have that functionality here?

Not really sure of the point of this statement. You can tether a device to the master devices cell network, but not the wifi network. Im not sure why the network type would matter, the bluetooth signal should be the same no matter what.

If that were the case then i would think all WiFi enabled devices would also be Bluetooth enabled, although i could probably poke holes in that assumption myself if i felt like it.

WiFi and Bluetooth almost always share an antenna, that doesn't mean all WiFi devices have Bluetooth.

My Galaxy S10 seems to work fine when connected to WiFi and then using Bluetooth tethering on my laptop to connect to the phone. Do note that you then have to join the phones Personal Area Network before you actually establish a network, this might be where things are going wrong as the tablet might not support this.

It is REALLY slow though, under 1Mbit each direction.

LIGISTX · October 4, 2019

3 hours ago, ShafterGT said:

Not really sure of the point of this statement. You can tether a device to the master devices cell network, but not the wifi network. Im not sure why the network type would matter, the bluetooth signal should be the same no matter what.

If that were the case then i would think all WiFi enabled devices would also be Bluetooth enabled, although i could probably poke holes in that assumption myself if i felt like it.

If your device you are trying to tether to doesn't have wifi or a cell network, it likely doesn't support "the internet" in general. From a software and hardware perspective, think of how that thought process would have gone. It seems like a weird use case to need to tether "to" a device that doesn't have wifi or cell. The reason I am saying that is the situation you are in, is because thats the logical result of the issue you are posing.

For example, you want to tether your phone to your tablet when your on the bus. Ok, sure, you are going to piggy back the signal from the cell GSM network and send some over bluetooth to your tablet. Easy, this makes sense.

Now say, your on your wifi network at home. And you want to get your phone and tablet on the internet. Well, obviously they both have wifi, so connect to wifi, no need to pass a wifi signal from your phone, through bluetooth, to your tablet. If your phone is on wifi, your tablet can be on wifi as well.

To assume the user would want to share a wifi signal over bluetooth assumes the device receiving the signal doesn't have wifi... Sure, it could be a desktop PC with a etherent port and no wifi card, but then.... that is an entirely other issue that would be solved a different way.

My point here is, it wouldn't surprise me if there was a software development decision made along the lines of what I just described...

And my second point is about the physical antenna, not the hardware the antenna is plugged into. Since they share the same antenna, it likely has to switch what signal is being sent/received between the wifi and bluetooth chips which would destroy throughput, or it just sends both signals at once and hope they don't just step all over eachother. Just because a phone has a physical antenna that does both bluetooth and wifi doens't mean all devices that have one ALSO have the other, there is hardware accompanying those antennas that define what capabilities the device has. The antenna is really just a piece of metal at the end of the day, a really well engineered, extremely complicated, absurdly hard to perfectly tune, piece of metal.