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San Jose, CA

1 recommendation

GSM/GPRS SIMs for telemetry

I'm thinking about some telemetry project, and I need a GSM/GPRS provider in the US with some friendly telemetry pricing.

T-Mobile USA already has a pre-paid 30$/mo plan with unlimited SMS and unlimited 5GB@4G data, and voice support. Since I'd only be using SMS and/or GPRS, 5GB@4G data sounds like way-way-way too much (probably would be enough to last a whole year), yet, at the same time, it seems like noone has any cheaper plans whatsoever anyways.

Perhaps a contract-based data-only T-Mo plan with 200MB/mo at 10$/mo (after a separate-voice-contract discount) is what I'm looking for? But I think my usage might require SMS and a pay-per-minute voice capability, so, a data-only plan might not do it.

What's the best and cheapest 2G GSM/GPRS SIM-card provider, with unlimited SMS or plentiful GPRS data, and pay-per-minute voice? I think the price structure for something like this, with the set-it-and-forget-it attitude, should be more on the order of 10 bucks per month, or less. Otherwise, it makes little sense to pay the same no matter how network-hungry the device is, and makes it prohibitive to have as many devices as necessary to be connected to the net.
2013-01-23 16:36:00


1 edit

Hi Marissa,

I've sent you an email. However, the fact that you seem to be offering personalised service and think that I'm a business, leads me to guesstimate that the prices will likely be much higher than the off-the-shelf prices from T-Mo directly.

So far, with T-Mo, it looks like a heavy-use GSM/GPRS device would cost only 30$/mo with the 5GB@4G plan with unlimited SMS and 100 voice minutes.

As far as ready-to-go-sleeper-agent SMS-only devices go, seems like with T-Mo I might either go with PAYG with 10$/90days with 100 rollover SMS (3.33$/device per month), or with the Pay-By-The-Day plan with 1$/day (on days used) for unlimited SMS, or 2$/day for unlimited SMS and data.

(Anyone knows how PbtD plans are funded and how long the funds are good for? Also, with PAYG, can I re-fill the account with several 10$ re-fills right away at the same time, to make it active for 90days — the number of refills?)

(Also, if no voice or SMS support is needed, a 2-year contract data-only Value plan at 10$/mo for 200MB or 20$/mo for 2GB might be useful; e.g. for some tablet-based telemetry project.)

So, unless I don't understand how those PAYG and Pay-By-The-Day services work, it seems like one active and several sleeper-agent telemetry devices can already be had for about 40$/mo with T-Mo off-the-shelf services as is. I bet there'll be hoops, but for a hobby project, it's not too shabby, after all! :-)

Would be nice if there were other similar off-the-shell plans, without a premium price, and with an emphasis on telemetry applications.

2013-01-24 15:52:10

Ok, there are some more details about T-Mo plans in »[T-Mobile] PAYG and PBTD prepaid plans for backup purposes. Summary: PAYG expiration date resets when you do a refill, instead of the days adding up. However, once you reach Gold status (either through several refills to a 100$ total, or through a single 100$ refill), all subsequent refills reset the expiration date to a year from any refill, instead of just 90 days. None of these rules appear in fineprint, it seems, but they do appear in official faqs (see the tmo thread above for more details).

It's still unclear / unconfirmed what kind of expiration rules are on the PbtD plans.

Also, I thought a little bit more about the 5GB@4G plan, and some common engineering sense (which almost always conflicts with marketing) dictates that using those 5GB over 3G makes use of less resources than 5GB over 2G. I talked to my vendor, and I plan on having about 10MB/day through GPRS; that's 300MB/month on GPRS. Logically, it seems several times more than 5GB@HSPA+; is it at all likely that they will disable an account that's using 300MB/month through GPRS? How swamped are 2G / 2.5G networks nowadays? The whole 2G GSM spectrum is shared between all kinds of 2G / 2.5G and 2.75G devices, right? How efficient or inefficient is periodic (every 10 to 60 seconds) short message passing through TCP or UDP over GPRS compared to the same messages being passed over SMS?


Does T-Mobile USA prepaid offer roaming for SMS?

T-Mobile USA prepaid maps show that they do offer 2G voice roaming even for prepaid customers. It is also know that they supposedly offer no data roaming and no 3G roaming.

How does this affect telemetry? Do I get SMS roaming on AT&T with a tmo repaid sim? But will GPRS not work?


Sunnyvale, CA
·T-Mobile US
·AT&T U-Verse
reply to ConstantineM

Re: GSM/GPRS SIMs for telemetry

said by ConstantineM:

is it at all likely that they will disable an account that's using 300MB/month through GPRS?

I think not not enough cases for them to look for it and I guess the GPRS network is not swamped.

What I would worry about it that the vendors are re-farming the spectrum and moving 2G that might mess you up.

I like SMS as the transport mechanism, the reason is SMS will probably roam much better than GPRS.