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Wouldn't CSFB need Verizon to take out 10 MHz chunks for UMTS? That would be kind of rough on the current EV-DO network.

Verizon is not doing CS Fallback for voice on their LTE phones. They are pursuing a dual-radio strategy which is similar to how CDMA networks handle ‘3G’ today.

A CDMA network uses a 1xRTT connection (similar to basic GSM) for voice. But recall that 3G data is “EV-DO”, which stands for “data-only”. This means that the 1x connection remains active for voice calls while data runs over the EV-DO network.

Apply this to LTE, and LTE becomes a “DO” network, and the 1x network remains active to provide circuit voice services.

I don’t think this type of dual-radio approach is available to GSM operators. CDMA networks were developed from the ground up to support a dual-connection 1x + EV-DO. GSM never had the concept of two network connections active simultaneously.

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