Hacker News Reader

Comment by finnn | Hacker News Reader

so the core GSM is done by a SIM800L module. Will that work on any normal cell network? I know a certain class of cheap GSM chip only works with a 2G network, and (as I understand it) T-Mobile is the only operator of such a thing in the US, and they're trying to phase it out. Is this correct? Could someone enlighten me as to how all this works?

View on HN

The SIM800L seems to be a Quad-band GSM module with GPRS.

So yes it's only 2G, but you've got the potential for SMS and maybe even 512kbps data. No idea about an audio channel (voice calls).

Whilst 2G is old, it's supprisingly battle tested and goes through walls quite well. A year ago we were told to expect the phasing out of 3G networks and to expect carriers to expand 4/5G with 2G as fallback.

Also, you gotta bear in mind, this module can be bought for £5. Getting a PCI-E 2/3/4G micro-pci card for my laptop is priced at closer to £200, so this is a great starting place. Expanding to a module that supports multi-networks either later or as an upgrade wouldn't be overly difficult - this is just a super cheap way of being able to test with real SMS, real networks and real recipients.

I understand that it's much cheaper than a 3G/4G/LTE connection, but if it's going to become non-functional in the foreseeable future, I'd like to at least be aware of that before building something on it.

At least some mobile operators are getting rid of their 3G networks and shifting focus to 4G/LTE, but keeping 2G because of how common it is.

In Australia all the GSM/2G networks have been killed off. Only 3G and up now.

Correct, the SIM800 line are 2G only which I believe is only provided in the US by T-Mobile as you mentioned. In the UK things are a little different, where the vast majority of the core mobile network providers still supply 2G networks, but I believe some of them have published plans to decommission them within the next couple of years.

In terms of 3G, 4G and LTE modems, they’re a little harder to come by quite so readily, and are a damn sight more expensive too! You can pick up an 800L for £1-1.50, for 3G it’s close to £20-30 from what I remember.

I'm unfamiliar with the baseband scene at that level. Might you know why the difference in price between 2G and 3G modules is so striking?

Well it will work on a GSM/GPRS/2G network. As you noticed, certainly in the US, those are getting rarer by the minute. AT&T shut theirs down on 01.01.2017 [1], and other providers also have plans to discontinue service in the near future.

So on these networks, this module will simply not work or you are always in roaming.

[1]: https://www.business.att.com/content/other/2G-Sunset-FAQ_201...

Reply on news.ycombinator.com