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T-Mobile lays ground for embedded SIMs

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T-Mobile USA has announced plans to use embedded SIM chips in devices making use of its GSM network, preventing punters from using them on other networks by switching the SIM.

Network locking isn't the motivation behind the move - apparently it's all about getting the SIM smaller and more robust, and to remove the complexity of having to put a SIM into a device which might be anything from a rainfall sensor to an electricity meter.

T-Mobile's new embedded SIM is about the size of a pin head and much more durable than existing models, though it performs the same function in the same way as a traditional SIM.

Even traditional SIMs aren't as large as they appear; the electronics are glued to the back the visible metal contacts and hang in a void cut into the plastic, the components themselves being only a couple of millimetres square. The additional space is used to make the SIM fit human fingers, and is defined as part of GSM. Reducing the size of a SIM is technically easy - just remove the plastic - but doing so means the device no longer conforms to the GSM standard.

In Europe that's a significant problem, as mobile phone networks are required to conform to the GSM standard which includes a removable SIM. It's a requirement that operators have tried to work around many times, including one case where a drop of glue was applied to every SIM to prevent users switching them - conforming to the letter of the law rather than its spirit.

In the USA operators can deploy what they like - CDMA networks have a SIM equivalent, but no one uses it as no one wants customers to be able to switch networks by sliding in a different chip. But when it comes to non-telephony devices, a non-removable SIM might make more sense.

Take the example of the Kindle, which uses Sprint's CDMA network to a Qualcomm back end, with Amazon footing the bill. The Kindle would gain nothing by having a removable SIM - it couldn't be used on any other network, and Amazon would certainly balk at paying the bill, so such a thing would make the service much more difficult to manage. Given that users aren't paying the bill anyway, they shouldn't really care.

So as mobile phones become much more than devices on which to talk, it might be time to consider the embedded SIM, even if it means handing more power to the operators. ®

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