No simultaneous voice and LTE data on CDMA with iPhone 5
As it turns out, the iPhone 5 won’t be able to do simultaneous voice and LTE data on CDMA networks.
There are other phones that are perfectly capable of doing the job, however Apple have chosen to go with a single chip and singe radio for voice and data, and not to use yet a third antenna. This allowed reducing the size of the handset, yes, but you still cannot make voice calls and use LTE data simultaneously on the CDMA networks.
If you need more info, and a more detailed analysis click here for AnandTech’s full report.