3G to WiFi Bridge Brings the Internet

[Afonso]’s 77-year-old grandmother lives in a pretty remote location, with only AM/FM radio reception and an occasionally failing landline connecting her to the rest of the world. The nearest 3G cell tower is seven kilometers away and unreachable with a cell phone. But [Afonso] was determined to get her up and running with video chats to distant relatives. The solution to hook granny into the global hive mind? Build a custom antenna to reach the tower and bridge it over to local WiFi using a Raspberry Pi.

The first step in the plan was to make sure that the 3G long-shot worked, so [Afonso] prototyped a fancy antenna, linked above, and hacked on a connector to fit it to a Huawei CRC-9 radio modem. This got him a working data connection, and it sends a decent 4-6 Mbps, enough to warrant investing in some better gear later. Proof of concept, right?

On the bridging front, he literally burned through a WR703N router before slapping a Raspberry Pi into a waterproof box with all of the various radios. The rest was a matter of configuration files, getting iptables to forward the 3G radio’s PPP payloads over to the WiFi, and so on. Of course, he wants to remotely administer the box for her, so he left a permanent SSH backdoor open for administration. Others of you running remote Raspberry Pis should check this out.

We think it’s awesome when hackers take connectivity into their own hands. We’ve seen many similar feats with WiFi, and indeed [Afonso] had previously gone down that route with a phased array of 24 dBi dishes. In the end, the relatively simple 3G Pi-and-Yagi combo won out.

Part two of the project, teaching his grandmother to use an Android phone, is already underway. [Afonso] reports that after running for two weeks, she already has an Instagram account. We call that a success!

39 thoughts on “3G to WiFi Bridge Brings the Internet

    1. In most places, a high-gain antenna can get a defective device blacklisted for exceeding the tower limits, and or ignoring the tower commands to lower broadcast TX power in a given cell.

      However, it is unlikely to be detected as long as there are no other users in the saturated broadcast zone.

      Ubiquiti point-to-point routers would probably cost the same, easily exceed 80Mbps, and not be subject to eventual ban.

    2. Well… if he did live in the US… would 3G even be part 15? Isn’t it some sort of licensed service with the cellular provider owning the license? And I’m guessing that laws are similar in most parts of the world ie his part.

  1. A few years back now the federal government in my country mandated that people be assured access to 3G so a large fund was set up to make such antennas available to anyone with reception problems, but the rest (the WiFi side of the data link) was up to you and so the ISPs stepped in with 3G to LAN/WiFi gateways. Unfortunately the gateways were rebranded gear from Huawei and had suspect security.

  2. Making his own wifi antenna is awesome. I made te mistake of buying an off-the-shelf wifi yagi and they were absolute trash even from a distance of approx 160m between them

      1. The beauty of cheapest from China is you get a big discount but are buying factory seconds, as in you get a knock at this questionable but fixable junk vs any store except maybe a surplus outlet. I treat them as a kit with some risk and usually with some easy tweak have a fully functioning widget. Especially considering I am already going to be doing some hacking this is the good for me and my wallet.

    1. Yep, cheap Chinese are. After that I built a 15 element yagi from scratch from a tested design. measured impedance and fitted a suitable ballun. So I got 16 dBi and 1700m range to a 100 mW router with a standard omni rubber duck

    2. No. Read again. Why would he have built a WiFi antenna? So that Granny’s WiFi would only work in rooms that are a straight line in a specific direction from her Raspi router?

      The yagi isn’t for WiFi. It’s for 3G.

      1. 3G, WiFi, same basic principle, different measurement between elements but largely the same thing. The point I was making is that when it comes to antennas I have found DIY is a much more reliable option than buying something off-the-shelf especially when you are dealing with cheap Chinese sellers.

        1. Yah, that was RW’s third law back in the day…

          “A bent coathanger half wave dipole TV antenna will have 300% of the performance of ANY indoor set top TV antenna of any price.”

  3. Yagis on 3/4G are a common sight in rural Australia. There is no issue of saturating the cell when your signal marginal.

    I’ve played with a few “commercial” antennas off EBAY and they are crap to say the least – they look like s Yagi and have coax and connectors and a mounting system and the description sayes they work – but they only work when you live next to the tower.

    The amazing thing about this project is the ability of the grandmother to embrace the changes in technology. Too many stick their heads in the sand and refuse to even try.

    Good on her and keep up the good work Alfonso

    1. I agree about the china special antennas off ebay. I’m also in Rural Australia and have helped farmers setup 3G yagi’s on their house or a 3G to Wifi bridge to get internet from a hill down to a house. The local made antennas such as RF-Industries are great but expensive although they can be worth it.
      I have had no issue with having gear disabled due to saturating a tower but I have sized the antenna to provide enough gain to reach the tower without too much extra gain.

      As for the router side I’m currently experimenting with using a Pi loaded with Open-WRT for use as a wifi bridge and router.

      I need to finish calibrating my 3D printer so I can create the plastic insulators and mounting points for some custom yagis for use on 3G/4G and other radio stuff.

  4. “The nearest 3G cell tower is seven kilometers away and unreachable with a cell phone. ”

    Where does grandma live? At the bottom of a well?

    The cell should be good for at least 30km.

    1. Maybe in flat land without any vegetation. In woods and in slightly warped terrain 7km and no reception is standard. I had also 7km to nearest tower. To get cell recption you had to find THE spot, and if you wanted internet… forget it. I tried to connect to internet with 20dBi dual panel antenna but could not find signal. Then someone came with small 3g router with two small stick antennas and enerything worked… RF will never cease to amaze me.

    2. Sure… if this were 1980 and the ‘3G modem’ was a bag phone meant to live in her car. Cell towers these days are lower power, higher bandwidth (which also reduces distance) and spaced much less far apart.

  5. The USB-3G to WiFi is brilliant but why not convert to Ethernet? Then you could do a custom POE injection (satisfying his “keep 230 out of box” goal) and then could route the Ethernet down to a router in the house. Probably only need some really basic configuration to get things going and then let the router do the hard work.

    Still a cool project none the less. I will be studying some of that scripting for a project I have in my head.

    1. POE is handy when it’s things like an office full of IP phones, that don’t need separate power supplies, and now the standard’s taking off I’m sure there’ll be plenty of little gadgets using it.

      But for supplying power in this case, it’s just replacing a bit of wire. With a more expensive bit of wire! As well as the injector at one end, and the receiver / convertor at the other. So it’s probably a bad idea. Same for the Wifi, Wifi’s probably best if it’s just someone’s grandma wanting Internet at home. It should be able to cover everything she needs to use it for, and there’s less to go wrong than with wired Ethernet. No hardware involved in the connection, so no cables to fall out. Our guy can manage everything remotely (hopefully!).

    2. Hi!

      I had other priorities so, cost had to be kept down. Despite there are cheap PoE injectors, this would have prevented me of using the Zero and to to a model B instead. It’s bigger, i had a small box, … But yeah, A LOT of room for improvement!

  6. My parents live in a very similar situation, and I could’ve done this with premade components (a Huawei 3G router with LAN ports and WiFi using an external 3G antenna connected via the dedicated port).
    Last year I’ve upgraded their setup to 4G (D-Link DWR-921 router with a B20 LTE compatible antenna), they get a very nice 20-30Mbps downlink in the middle of nowhere.
    So yeah, it’s a nice DIY, but this is nothing new.

      1. Exactly, this is no Panacea. Grandma will run up against data-caps and outrageous overage charges that will put her into bankruptcy PDQ. If at-all possible – STAY OFF CELLULAR FOR DATA! It’s too expensive and corrupt to be truly useful in most any part of the World. Cellular Providers = EVIL!

  7. Congrats, good work!
    I have a similar problem. My family has a summer house with aluminum siding, working like a giant Faraday cage, and some mobile networks work inside, some don’t. I’m thinking about a passive repeater with Yagi/LPDA on an antenna mast, some coax cable and an omnidirectional dipole/two triangles/two circles. I’m not sure if it’ll work but I hope so.

    1. You can get semi-inexpensive (about 100 quid-ish last I looked) mobile repeaters from the phone companies themselves. Meant for use on a household or office scale, for problems just like yours.

      Of course 2 aerials and a bit of wire would be a lot cheaper, if it works.

  8. My experience, both as a User and as an equipment provider, the cellco’s do the monitoring and they get the ‘appropriate authorities’ to do the enforcement. The neat thing about directional antennae is that you can capture a cell tower way off in the wrong direction, away from the nearest one, and the location through triangulation fails! Neither StingRay or any other IMSI-catcher will get you either.

    4G coverage in my country has been tested to 99.1% coverage of the whole country.

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