chemeris's comments

Just to make it clear - current "unlicensed" LTE technologies are LTE-U and LAA require an "anchor" channel in a licensed band. I.e. you still can't run it in your home unless you have a license for one other spectrum band. It's still limited to a carrier play, unfortunately. There is MuLTEfire tech by Qualcomm which can supposedly work completely in unlicensed spectrum, but it's proprietary and not very much is known about it so far.

I'm the CEO of Fairwaves (http://fairwaves.co). We work with telcos, mostly in developing countries. But there are also customers who run our tech in indegineous communities in Mexico (https://rhizomatica.org/), on mining sites, ships and just in their labs as a test tool.

There is a hope that 3.5GHz Citizen Band will make it possible for smaller companies to run LTE.

Speaking of UEs (aka LTE modems) - there is an open-source implementation add well. See srsUE and srsLTE.

As mentioned above, half duplex of HackRF would be a limiting factor, unfortunately.

HackRF can't do it, because it's only half-duplex. But there are plenty of full duplex SDR devices - check out UmTRX and USRP B210. We're also developing a really tiny high performance SDR specifically for LTE - http://XTRX.io

Yes. Osmocom/OpenBSC actually started as an open-source "network in a box" which implements all critical GSM network elements in a single executable. It greatly expanded since then - check out a list of projects there. As I mentioned below, more companies are joining Osmocom and there will be hopefully more work on the core network side. Other open-source projects targeting core network elements are http://www.mobicents.org/ and http://www.projectclearwater.org/ (IMS).

That's not true. To run a benchtop setup you just need an inexpensive SDR (LimeSDR, UmTRX or B200) and your laptop - that's not "high thousands". If you're deploying networks professionally, then yes - you'll spend thousands on proper base stations, software to control them, etc. But in the latter case you should have your spectrum license, so operating a BTS should not be an issue. Also see my post above about 911 services.

Here is a video of tests we're doing at installations with real operators - https://www.youtube.com/watch?v=mxpUXPy1htA (our equipment is almost invisible on the top of the tower, big racks and thick cables are existing infrastructure which was there)

USB3 can pump up to 900mA @ 5V = 4.5W, which is pretty good. But each device has its own specs - e.g. LimeSDR has only 10dBm output power, because it doesn't have a built-in amplifier. So if you (1) don't attach a large antenna to it, (2) you operate in your basement, (3) you choose an unused ARFCn and (4) you operate in closed mode, you should be fine form technical perspective. That said, legality of this is up to you - check your local spectrum rules.

That's a really good idea, btw

Yeah, we're not as well known as some of the more prominent SDRs out ther. We're mostly targeting professional users and have been mostly focused on figuring out how to get our tech into the real telecom world. Stay tuned - you will hear more about us, as we now have our system integrated into operators and have our hardware running in the real world.

Disclosure: I'm CEO of Fairwaves.

Indeed, hardware is the key. You can't run a GSM base station without a good SDR transceiver attached to your PC. :)

In 2009 when we tried to launch OpenBTS with a USRP1 (Osmocom didn't work with SDR back then), it just didn't work and we had to spend days figuring out why and we had to solder a better clock to it to get it working. Today you have a selection of inexpensive SDR devices (B200, BladeRF, UmTRX.org) which let you run a GSM stack at home and LimeSDR is a great progress in this direction, especially given it's OSHW.

Note: always know the laws and check your local spectrum regulation policies if you want to run a GSM station. In most countries you need to get a license to do that even for educational/research purposes.

I also strongly discourage everyone from attaching any amplifiers to the aforementioned boards yourself. Even if you think you're sure you're not disrupting anything. Amplifiers will amplify all noise and spurs generated by your transceiver including ones in other bands you do not expect. So you may (and most likely will) interfere with other services. If you need a high power base station (and you have a license to run it) - get a commercial BTS which is tested to meet requirements and avoid interference. I can definitely recommend our UmSITE (shameless plug), but there are a number of other companies selling commercial BTSes.

If you're not interfering with existing services and run your BTS in a closed mode, 911 is not a concern, because a GSM BTS broadcast channel has a bit which indicates 911 service availability and all open-source GSM software disable this by default. So phones won't camp on your BTS for emergency services. To avoid interference you really should be running at low power like 1mW (on SDRs like UmTRX which have pretty high power by themselves you can easily reduce the power to a reasonable level) and use an unused ARFCN. Make sure to do a proper scan with fosphor/SDRangeLove to see traffic-only channels. Usual scan tools will give you a list of beacon (BCCH) channels, but will miss all TCH-only ones,

We're also partnering with Lime Microsystems (people behind LimeSDR) to create a next gen inexpensive embedded SDR - so you could turn an application you developed with LimeSDR into an industrial/embedded product easily. Check out http://xtrx.io for details.

CEO of Fairwaves here. Just want to slightly correct here. We indeed started with OpenBTS, but we switched to Osmocom years ago for a variety of reasons including better code quality and proper community development model. And while we're not the original authors of Osmocom either, we added SDR devices support to it, polished osmo-trx to a state it can be used in production, wrote first GPRS implementation, etc, etc. Right now Osmocom is a thriving community with several companies actively contributing, so it's moving faster than any other open-source GSM project out there. There will be more really exciting news about Osmocom soon - keep your eyes open. So if you want to go to the source - I suggest http://osmocom.org/projects for real open-source. Btw, no one stops you from using osmo-trx/LimeSDR with YateBTS if that's what you prefer. That's the beauty of choice open-source gives you.

The answer is to work with legal spectrum owners (aka cellular carriers), which is what we (https://fairwaves.co) and other in the space are doing.

Someone mentioned that building a full networks (or even a full base station) is much harder than just apt'ing some software and snapping some cheap SDR. So we spent couple years developing an SDR which is more expensive than your typical hobbyist one (http://umtrx.org) - btw even hardware of the simple version of our SDR is open-source - and then couple years building a base station which complies with all regulations and has open-source in its heart (based on Osmocom obviously). And now we've added a bit of (unfortunately proprietary) glue and we can run fully fledged cellular networks for carriers - mostly in developing countries, as was mentioned before, because demand for simple voice communications is through the roof there. At the same time you can buy one of our stations for your lab and play with it as much as you want (get your test license first though).

So yes, you can't stop progress and technology gets cheaper and more accessible. Which is very exciting.