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Comment by sbierwagen | Hacker News Reader

  And then there’s dual SIM (or even quad SIM). It’s a feature 
  that’s really popular in Asia and Latin America where people 
  might use one network for a local call and another for an 
  international one. That’s largely something MediaTek drove, 
  but now it’s in the Moto E, which also has a feature called 
  SmartCalling to help people set up and swap between SIM 
  preferences and automatically configure access point names.

https://bbot.org/blog/archives/2013/10/28/programmatically_a...

  You know what would be cool? If your phone knew how much 
  bandwidth from each carrier cost, and could switch between 
  them on the fly, depending on which one was cheapest, like a 
  multi-SIM phone that didn't suck.

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Dual SIM is such a cool feature and so common in asia that not having it in Western markets almost seems like a conspiracy.

Work/private phone. Burner. Try out a new network. Add a local SIM when traveling.

Not having it on Western markets? Are you sure you're not confusing US with Western? Here in our very western European country they're common and often advertised. Both my previous phone (crappy Samsung) as well as my current cheap Android were dual sim.

What country in western Europe ? Never heard about anyone talking about a dual-sim telephones in France. But there is not much point of having two subscription to two companies that prices are aligned.

Portugal. The reason I have one is because I have a company-issued SIM card, besides my personal one. But here prices are not actually aligned, since some providers have free, unlimited calls between members of the same plan, but not between members of different providers.

Wiko Mobile is a big name in France (#3 in 2013) and (almost?) all the smartphone they sell are dual sim: http://world.wikomobile.com/p-Wiko-Smartphones they are sold in supermarket as well (Auchan etc..)

It's irritating. Latin America is also entirely western.

I live in Ireland. Haven't seen them here. In SE Asia they seem to be as standard as cameras.

There are a lot of reasons why you might want to use a dual sim phone but burner is not one of them.

Well, let's just say there are different reasons necessitating different levels of operational security, and some are not as demanding as others.

Cheating on your wife with some cheap floozy? Dual SIM phone with a burner chip on a temporary number is fine for that. Spring break? What happens in Vegas stays in Vegas? Sure.

But drug dealers, probably not. Bank robbers, probably not. Anything that's probably somewhat gangster, probably not.

Indeed. I work for clients in two main countries. Having a dedicated mobile number in both countries coming into the same mobile phone would be useful. Currently I carry around two phones.

I considered the HTC Dual Sim http://www.htc.com/uk/go/htc-one-dual-sim/

In the end I got a Nexus 4 and carried on with two phones. I was so impressed by the Nexus.

Would having one cellphone number and then using a service to purchase DIDs and have them forward to your main number work better for you?

>Dual SIM is such a cool feature and so common in asia that not having it in Western markets almost seems like a conspiracy.

When the phone market is dominated by the carriers they don't supply dual-sim phones because they don't want people to easily switch or complement their networks. I know of at least one carrier-named phone sourced from ZTE, whose only difference from the original ZTE model is the removal of the second SIM slot.

Some of it is also the CDMA legacy of the U.S.

(I guess the carriers probably liked that the system didn't use SIMs, but on the other hand, the technology has proven itself)

You can buy all sorts of Chinese phones (with dual SIM) directly from China online on sites like Aliexpress.com. The thing is, US uses weird 3G frequencies or something from the rest of the world.

I bought my 3G MTK phone a year ago on Aliexpress.com. It worked fine perfectly while I was living in Europe. Then I came over and now I'm always on Edge network and network speed is significantly slower.

Carriers don't like to sell multi-sim phones because they are interested in selling you the ultimate expensive plan with a new phone for it. So you have to look at retailers that don't offer voice and data plans.

Technically you could get the functionality of dual sim with software, so ultimately this will be an app on every phone.

Out of curiosity - How does dual SIM work? Does the phone register with both networks, or does it switch allow you to quickly switch over before making an outgoing call?

You're registered to one of them at a time. Baseband chips typically only handle 1 network at a time.

Here's an example http://www.youtube.com/watch?v=nw76tsRKa_Q#t=44

It depends on the type of dual SIM exactly; it could mean anything from not more than being able to switch between two SIMs, to being able to use both of them simultaneously.

The Mediatek dual SIM phones do register to both networks at a time, they have two IMEIs as well.

http://www.youtube.com/watch?v=Ro7k4itFT-U

afaik there are two different ways of operating: DSDS (Dual Sim Dual Standby) e DSFA (Dual Sim Full Active).

The most common is the first one, where the phones are both registered but when you're communicating with one sim the second one is unreachable (as there's only one radio circuit, one antenna, one processor etc..). The second one, as the name says, allow you to use them both but it's more expensive of course because of the presence of two circuits of everything (at least radio-wise, it's like having two different phones in one) so it's far less common.

As far as I know almost all the "chinese" dualsim phones fall in the first category.

There's a service that does something like this: http://www.knowroaming.com/

It basically acts like a local SIM while you're roaming, including getting a local phone number.

You get the usage split out by SIM in the usage screen, so implementing this should not be hard.

dual sim is popular in China

Most android/feature phones will automatically choose which sim card to make a call with depending on what network you are on.

I'm not sure how well this would work in reality, for starters most dual SIM phones only provide 3G service onone of the SIMs, you have to physically swap then over if you want it on the other.

Such an app would also need to keep track of the credit on each SIM, bearing in mind there is no standard way to do so among all operators. It would also need to deal with differences between the phones reported data usage and the operators measured.

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