iPhone 4 T-Mobile Always Roaming = Happiness
June 8, 2010 8:36 PM   Subscribe

If I jailbreak an iPhone to T-Mobile, can I roam to achieve 3G speeds? (I'm thinking the iPhone 4 here, but nobody can comment on that with complete accuracy, yet.)

So, the iPhone 4 was announced and I'm buying one as soon as I know that it will be jailbreak-able to T-Mobile. I live in South-East South Dakota and, through a long train of events, have T-Mobile. The problem though is that using the iPhone on T-Mobile only gets you EDGE speeds, whereas 3G speeds would be really nice.

BUT, since I'm always roaming here in SD, can I get the 3G speeds because my iPhone will be communicating with cell towers that support iPhone 3G frequencies?


(T-Mobile isn't offered here in South Dakota, which is why I'm roaming.)
posted by 47triple2 to Technology (10 answers total) 1 user marked this as a favorite
Currently the iPhone 3GS only achieves Edge speeds when jailbroken and used on the T-mobile network. (Wikipedia: "T-Mobile exclusively uses the AWS 1700/2100 MHz frequency-band, making it incompatible with other existing 3G UMTS/HSPA networks already established in the United States.")

The iPhone 4 adds new frequencies (full line up for UMTS/HSDPA/HSUPA = 850, 900, 1900, 2100 MHz) but I believe you need both the 1700 and the 2100 MHz for it to work, so it looks like no dice on iPhone 4 either.
posted by sharkfu at 8:51 PM on June 8, 2010

posted by meta_eli at 8:54 PM on June 8, 2010

I understand that explanation if I'm on a T-Mobile network, but if I'm roaming with 1700/2100 towers shouldn't I be able to achieve those speeds? Or is my T-Mobile SIM card going to control which ones I connect to?
posted by 47triple2 at 9:04 PM on June 8, 2010

This is an interesting question. I'm in much the same boat, only I have the original iPhone, so 3G is a non-issue regardless.

Generally, if you're a T-Mobile customer and you're roaming on a non-T-Mobile network WITH a T-Mobile "blessed" phone, you can basically kiss 3G goodbye . . . because only T-Mobile, and none of its roaming partners (among them AT&T) uses the 1700/2100 frequencies.

So, conversely, I'm about 70% sure that if you're using a phone with T-Mobile service that ISN'T "blessed" with T-Mobile frequencies -- i.e., you're roaming on a provider that DOES use the more common 3G frequencies -- you WILL get 3G speeds as a side bonus. I really can't imagine that the roaming agreements they have say "voice and EDGE data, but no 3G." T-Mobile and its roaming partners probably figure the overwhelming majority of T-Mobile roamers will have phones that can't use the partners' 3G networks anyway, so who cares. It's not like carriers charge you more to have 3G data vs. EDGE only, so I don't see why they'd micromanage the roaming to that degree.

I was thrilled to see that the specs said iPhone 4 was "quad-band," then annoyed as hell when I saw the fourth band was for better data coverage in Japan. UGH, would it really kill them to just use the chipset that supports 1700/2100 also? Sony Ericsson, for instance, does it with phones that aren't even offered by T-Mobile USA or Wind (the Canadian carrier that's the only other one in the world that uses 1700/2100) because . . . why not?

So anyway. Yeah. Give it a shot. The worst thing that'll happen is that you'll only have EDGE. But you're used to that anyway.
posted by CommonSense at 9:42 PM on June 8, 2010

Yeah, CommonSense basically just said exactly what I'm thinking! Can anybody actually confirm my (our) suspicions or will I have to bite the bullet and pray for the best?
posted by 47triple2 at 9:48 PM on June 8, 2010

I MAY be wrong about this, but I'm fairly certain that my wife's iPhone 3G had the "3G" icon when we were visiting Toronto a week and a half ago. As with me, the SIM in her phone is a T-Mobile US one, and the phone is (obviously) unlocked.

So . . . for what it's worth and all.
posted by CommonSense at 9:58 PM on June 8, 2010

ATT doesn't offer 3G service in SD yet. ATT customers with 3G iPhones can't get 3G there according to ATT's map. It only has roaming agreements for EDGE/GPRS. ATT bought Alltel but that's a different technology so they'll actually build out its own 3G UMTS network and then, and only then, would your unlocked iPhone 4 work. Maybe. I don't think there's a single place in the US where there's a UMTS 3G signal for AT&T or T-Mo to roam since their 3G frequencies are different.

If you travel outside the US, T-mobile's roaming will be 3G. In 2005 I was thrilled to see my European model SE phone got on 3G in Japan and Europe. It didn't work here because a) there was no 3G from ATT or T-Mo and b) even if they didn't there wasn't the US variant ATT ended up using.

Since 3G is different, it remains to be seen if ATT and T-Mo USA have a 3G roaming agreement. Your T-Mo SIM first looks for its own towers to attach to then a list of partners. If I had to bet the ID for ATT's 3G and EDGE/GPRS are different and so you'd be hosed. In a market with T-Mobile EDGE Service, it would get priority over roaming on a competitor's 3G network.

I've been in the sticks and found my iPhone 3G attaching to T-mobile (EDGE because that's all there was) so such agreements exist for EDGE because they share the same frequencies. Since ATT is such dicks about their 3G bandwidth I really doubt they'd agree to sell (or if they did the price would be sky high that T-Mobile would pass) to T-Mobile because it would only be for a small number of customers that for the most part are probably using ATT phones.
posted by birdherder at 10:20 PM on June 8, 2010

What will likely happen is that if you're in an area with absolutely any AT&T coverage whatsoever, the phone will default to AT&T, even if that is EDGE-only. Actually, it'd default to AT&T even if it gets no data connection whatsoever.

Really, unless you're on a phone that lets you pick a non-preferred network from a list, it's always going to default to the primary when that's available. I was recently roaming in Quebec and the phone connected to a few different carriers, and there actually was a "pick a network" option that appeared, but only when I had absolutely no coverage whatsoever so it didn't help me at all.

So, my guess is that you will never get 3G unless you're in an area with no AT&T towers.
posted by mikeh at 6:45 AM on June 9, 2010

To piggyback, are there no charges for data-roaming on T-Mobile, in the US? I turned off data roaming on my phone because I scary message said turning it on could be very expensive.
posted by 6550 at 8:42 AM on June 9, 2010

It won't work. You are missing the 1700 frequency. That's what you need. When you roam, the phone might pick up AT&T networks. (Or if you come to Toronto, Rogers networks.) I think it only works at all because T-Mobile also uses 2100 MHZ. In Canada you can't use the phone with the new carriers because they are AWS (1700) only.
posted by chunking express at 11:12 AM on June 9, 2010

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