How does roaming work?

[yg17]

I'm curious to know how roaming works with cell phones.

My sister and I just completed a road trip from St. Louis, to Washington DC. I have Cingular, she has T-Mobile. While we were in the middle of nowhere, there were a few cases where I had a signal and she didn't, and vice versa. For example, in Charleston, WV, she was roaming onto West Virginia Wireless's network, while I was still on Cingular. But then, further east of Charleston, I lost signal and she was still on WVW's network. Now, when my phone detects that there's no Cingular towers, shouldn't it also have roamed onto WVW? Likewise, there was another time when I was full signal on Cingular, and she had no signal. Shouldn't her phone have roamed onto Cingular's network? Or when I had nothing and she had full signal on T-Mobile's network, shouldn't my phone have roamed onto T's network? Throughout the trip, I never went onto any other network. It was either Cingular, or nothing. I guess I'm not understanding when a phone goes onto another company's network, and when it doesn't. Thanks.

 

[miniConvert]

Roaming depends on pre-established agreements between operators. You can't roam onto a network that your service provider does not have an agreement with. Hope that helps

 

[yg17]

Roaming depends on pre-established agreements between operators. You can't roam onto a network that your service provider does not have an agreement with. Hope that helps

So Cingular claims free roaming but then doesn't actually make agreements with other operators? Sounds typical of them.

 

[Dr.Gargoyle]

Roaming is basically that you get a "secret" phone number from the local provider. A call from from your cell is then redirected from the "secret phone number" back to your own provider. The local provider will then bill your provider, which in turn will bill you.
As an example. I am from sweden, so when I go to US I will get a for me unknown number, "secret" number. All my calls to my original number are then forwarded from my "secret" number in US. If someone in sweden calls me they will get charged with a local phone call, whereas I will be charged with a international phone call from Sweden to US.
This policy has some really insane implications. Imagine two people standing next to each other on a street somewhere in US, both with Swedish operators. A call from one person to another will be:
"secret" #1 in US -> original #1 in Sweden -> original #2 in Sweden -> "secret" #2 in US. That is, one local call will be charged two international calls.

It gets VERY expensive to use your cellphone in other countries. You are much better off getting a local SIM card together with a calling card.

I hope it made some sense...

 

[Dr.Gargoyle]

So Cingular claims free roaming but then doesn't actually make agreements with other operators? Sounds typical of them.

More or less all operators have agreements with a large number of other operators. Still, it is a hassle to find out how much they charge. You might have free roaming in US, but dont expect it to be free outside US.

 

[mkrishnan]

The way I understand T-Mo's roaming system is that, yeah, like others have said, if you get a signal, you are either on the T-Mo network or on a cell of another network that has a roaming agreement with T-Mo. So if the phone works, you're in a place where you can use it for free, and if it doesn't work, you're in a place where there's no network you have rights to... as opposed to say, Spring phones that roam to analog services with roaming charges. AFAIK, Cingular and T-Mo do this in the same way.

But the whole thing is complicated... in many places, my phone will roam onto Cingular's network. But here in the hospital, Cingular users have service (AFAIK, native service), and I don't have any service.

It's frustrating that the way the American cell phone industry works, we have half a dozen networks carpeting the same areas and no one in the rest of the country....

 

[Dr.Gargoyle]

It's frustrating that the way the American cell phone industry works, we have half a dozen networks carpeting the same areas and no one in the rest of the country....

It gets even worse when you go abroad... The mess is total. I thought it would be better with the introduction of 3G (UMTS) until I realized there are even more non-compatibale systems now than during the GSM/cdma period.

 

[balamw]

In the US we have two frequency bands associated with cell phones, one at 850 MHz and one at 1900 MHz (PCS). In Europe it's 900 and 1800. Roaming on GSM networks (Cingular, T-Mo, ... not Verizon) in the US and abroad will depend on what bands you phone can use, and also on some of the details of the SIM card you have in your phone. Many early GSM phones supported only 900/1800/1900 and thus cannot roam to GSM at 850 MHz which is where lots of spectrum and range is.

I ran into the reverse problem on a recent trip to Europe where my Cingular/AT&T 850/1800/1900 phone worked great in cities where 1800 spectrum was in use, but I couldn't get a signal in the countryside, where the locals were looking at me funny for not being able to use my phone...

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