
Can't see any reviews on Android Google Maps (when a Chinese sim card is in) - techolic
https://productforums.google.com/forum/#!topic/maps/FdWIPFluzBk
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oxidising
I have a China Unicom in my phone currently (as a second SIM, but I might now
take it out) and haven't had any problems with Google Maps. When I was in
China in June I was using Google Maps via VPN. This doesn't mean much of
course as things can move pretty quickly. I also didn't realise a SIM card's
capabilities.

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HillaryBriss
One of the bug commenters said that "neither reviews nor photos" could be seen
and believes that it was because "I once used this app in China" but does not
explicitly mention swapping out the SIM card.

my question: does a visitor to China have to swap out the SIM card in their
phone in order to use it there?

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vinay427
No. T-mobile in the US, for instance, includes roaming (unlimited slower data
and texts) in China with most of its postpaid plans.

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68c12c16
Yes, I heard that the Great Fire Wall in China treats network traffic
differently when one is on T-mobile data roaming...A friend of mine could use
her T-mobile phone to access google, gmail and instagram in china directly,
without using a VPN...But you can only access 2G or 3G network (not 4G) in
most of the areas there...

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bspammer
Somewhat related: I was in China recently, and bought a SIM at the airport.
You know those arrows on the mobile data icon in the notification bar on
Android that tell you whether your device is actively transferring data? The
upload arrow was on non-stop, the entire time I was there. I still have no
clue what it was doing.

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Gorbzel
Pretty obvious, it was uploading your personal data to the state.

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bspammer
That's basically what I assumed, but I wasn't aware that SIM cards had that
kind of access to the device storage. I thought at minimum it was sending out
my location constantly though.

I know next to nothing about telecoms technology, but in my head always
assumed that SIMs were basically just read-only chips containing keys to
authorise the phone to use the network. Clearly my assumption was wrong in
some way.

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allispwned
SIM cards can contain applets that execute on the baseband.

The baseband often uses the same system memory as the application cpu (where
android runs), and might even be in the same package or on the same silicon.
In theory devices shipped with an MMU to prevent the baseband from fucking
with the application processor. In reality, even Qualcomm ships broken MMU
configs, and don't bother to ship a fix until the device is near EOL. I can't
even imagine the horror show of Mediatek's MMU.

Of course it's also possible that this is Google playing nice with Chinese
legislation...

