Hotspotting Via Bluetooth

I was brief look around, but found nothing explicit nor recent on the subject matter. Are you allowed to hotspot via bluetooth at competions? I am aware that wifi based hotspots aren’t allowed, but I couldn’t find anything explicit on bluetooth. Thanks in advance for the help

The relevant rules from 2019 are E12 and E13. Read them and make a decision.

I have seen those rules, and previously decided that bluetooth hot spots were acceptable, but I wasn’t entirely satisfied so I wanted to see if anyone had some clear interpretation, if there is nothing clear already I’ll chuck it into the Q and A, but I wanted to plan around it as soon as possible.

Since Bluetooth operates in the 2.4 to 2.485 GHz band, I would say that it is not allowed. The whole point of the prohibition is to prevent other networks from interfering with the field system by operating on the same band(s). Bluetooth would definitely qualify.

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After a quick search:
Bluetooth does use the same frequencies as 2.4 ghz wifi, and will interfere with 2.4 ghz wifi.
Especially when there’s a lot of devices and wifi issues (AKA FRC competitions), bluetooth will interfere, while it’s going to interfere much less with less traffic on the band it’s using.
I’d suggest clarifying this in the QA system though, having an official ruling on bluetooth wouldn’t be a bad thing.
If this is for scouting, it may be worthwhile to look into a system that uses texting or a similar wireless communication system to communicate, since FRC almost certainly will not move to those frequencies.
Additionally, the 900 mhz band may be an option. It doesn’t seem to require any special permits, as the FCC says:

There are 900 mhz adapters available, so this is possible, but may or may not be worth it.
Mods, if this should be a linked topic instead, feel free to do so

Hotspotting Via Ethernet
Would that be ok?

Yes. If there is no wireless connection (beyond the 4g/3g data signal) you are fine.

I certainly hope we don’t get an official ruling on bluetooth… Up to now it has been considered a grey area that usually no one will complain about. If they rule on it, there is a solid chance it will go away as a legal option at competitions.

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Yeah, I used it at the 2019 competitions because I assumed it was ok, and had no problems with it. I admit that maybe I should have looked into it further, but I decided from the rules it was ok. Looking at some older threads, there were a apparently a couple situations where they asked refs at events and they said no, and others where they said yes.

We use one of these https://www.amazon.com/gp/product/B01N5ASNTE/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 its a cell to wired network modem / router. you would need a sim card with a cell phone data plan (we use an AT&T “go phone” tablet plan on it, i think it was like 50 bucks for 5 gig of data (plenty for scouting as long as the scouts don’t pull up Facebook or YouTube between matches). From that we connect a small netgear switch and then wired connections to laptops or chromebooks with USB adapters. It has worked very well, and zero risk of interference.

It is a bit of an upfront cost, but has been reliable. Previous to this we used a USB Tethered cell phone to a laptop with internet connection sharing. we ran into issues there with the ease of setup and having to find someone to sacrifice having their phone for the event.

If anyone has questions feel free to let me know!

More on topic, the Bluetooth tethering has never been the cause of an issue that I’ve seen at an event both as mentor, and robot inspector. The robots all use 5ghz and 2.4 is used by the FTAs for diagnosing issues. The amount of BT devices out there (watches, headsets, etc) may cause issues, but the way I read the rule is that 802.11a/b/g/n/ac is prohibited. (ax will probably be added this year to that list) 802.11 is WiFi specifically. 802.15.1 is Bluetooth and is not mentioned in any way. BT is also way less powerful. Most devices have a max range of ~30 feet.

While I am not an LRI or the Q&A I have never heard of a team having issues while using BT for scouting.

My scouting system runs mostly through mobile phones, any clue if you can get something like that to work with lightning cables, usb c and micro usb? I had a bit of a problem with some team members not having access to data, and that’s where I needed the bluetooth hot spot. It is possible just to make sure everyone has access to data, but it can be a little easier to do something else. For computers and laptops I was just running hotspots through usb cables, which I assume there is no problem with.

I have seen some teams use a QR code to “share” the data. encode the scouted data for the match in a QR code then 1 phone with internet service would scan the QR codes and upload them to the system. But unless the rules change or there is a Q&A ruling using BT i would say is fine.

I’m actually curious - Would it be feasible for teams to have extremely short range wifi hotspots?
I’m thinking probably a 10 foot radius would work decently well.
Bluetooth has a range of about 30 feet, so only the very back corner of the stands would really work if my estimation of distances is right.

In 2020 we’re going to be deploying a similar system to what @fimmel mentioned above, but with lightning-to-ethernet adapters + iPads. From our initial tests, it seems to be working great so far. Only downside of a wired solution is the cable spaghetti in the stands, but it’s a small price to pay for peace of mind that we aren’t going to get an FTA shutting the system down.

Well, this topic has circled back to the front page again… my personal opinion is that for better or worse, the rules clearly state that only communication that (1) complies to the IEEE 802.11a/b/g/n/ac standard (E12 provides the two frequencies such communication uses as a reminder that both are prohibited, or as a explanation for why that list of standards was selected, and not, say 802.11ah/ad which use different frequencies, but its position as a parenthetical clearly indicates that is is subordinate in meaning to the neighboring test), and (2) is owned by a team (which is defined as anything connecting in client mode to a third-party base station) is prohibited. So Bluetooth, IMO, is not prohibited by any rule nor to my knowledge has it every caused a conflict with the field.

Someone has already mentioned 902-928 MHz. That can be a workable option, and the range will be larger than Bluetooth, although it is still not going to connect you from one end of worlds to the other. Look into the XBee 900HPs if you want some packet radios that are easy to work with over USB-Serial, they can also relay packets for one another in a mesh network. The max spec power is 1W although I don’t believe the 900HPs can get that high, I think they capped out at 27dBm.

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To add to this, Bluetooth also tends to be significantly shorter-range than WiFi standards, so allowed or not, it’s highly unlikely to cause interference, unless you’re right next to the field (and even then it seems like a stretch).

The downside to devices on the ~900MHz frequency range is that (in my experience at least) they tend to be highly line-of-sight dependent (though perhaps at high enough power outputs this isn’t an issue?).

That said, using ethernet to connect devices to a LAN seems like an interesting solution, especially if you could get a “hot-spot” with an ethernet output (like a cellular home internet router, perhaps?).

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Yeah, after experimenting with a lot of wireless stuff I think Ethernet is realistically the best and easiest way to go if you’re dealing with no cell coverage/non-cellular devices. It allows you to use the same exact code (we used a completely web-based app, so a TCP/IP network was a must for us to get data off the device) and just host the server on a local machine, and its incredible cheap.We spent a lot of time looking into a wireless solution last season (and we learned a lot) but ultimately decided the available options weren’t really worth the time investment.

Looking at the datasheet, the XBees claim 1000ft indoor/urban NLOS range (double at a reduced data rate). Of course, the datasheets are always inflated, but we were able to maintain a working non-line of sight link at about 250ft straight line distance, from the parking lot to an inner room of a concrete building–so they definitely have potential for NLOS applications. And I was wrong about those units’ max power–it was actually only 250mW which is just a quarter of the max power. Unfortunately, there were very few commercially available pre-certified devices that supported the full 1W output so we couldn’t easily test that.

However, when we were doing some testing at worlds, those same devices couldn’t even reach a couple pit aisles over. They would still do fine connecting between devices on the bleachers, but our goal was to get something long-range enough to transmit to the pit and we ultimately decided that was not realistic given the available technology. I’m guessing all the metal around made it impossible for the signal to get through.

We have received confirmation through the q&a system that Bluetooth is allowed.
https://frc-qa.firstinspires.org/qa/125

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Maybe… my laptop can work…
Thank you for clarifying!

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