The iPhone can handle phone calls and Wi-Fi data simultaneously regardless of the carrier. However, Verizon iPhone users can't simultaneously use cellular data while making a phone call because of network and device limitations. The CDMA-based 3G network that runs Verizon and Sprint phones can't operate phone calls and data usage at the same time. Verizon iPhones encounter the problem when switching to the 3G network when making phone calls.
Talk and Browse on Wi-Fi
If your iPhone is connected to a Wi-Fi network, you can continue using data access and make phone calls at the same time. If you're mid-call and trying to look up something or use an app, the service will work as long as you remain connected to Wi-Fi; the iPhone loses data access if the Wi-Fi connection is lost. All smartphones on Verizon's network are capable of connecting to Wi-Fi for data use while making phone calls.
No Simultaneous Talk and Cellular Data
The no-talk-and-data problem shows itself when an iPhone is connected to the Verizon wireless network. Since the 4G LTE network is designated for data, the iPhone needs to switch to the 3G network to complete the call. The phone is capable of connecting to only one cellular network at a time. Even if the iPhone supports LTE service, it's stuck with the CDMA 3G network's simultaneous talk and data limitation.
Network Isolated Issue
IPhones running on other carriers like AT&T and T-Mobile that use the HPSA Plus network can use simultaneous talk and cellular data with the iPhone. The HPSA Plus network doesn't have the CDMA network's only-talk or only-data limitation. However, when using talk and data at the same time the iPhone is able to access only the 3G network, which eliminates the speed and performance gains of 4G LTE data during calls. Verizon iPhone users can somewhat work around the system to make calls and use data at the same time by making data-based calls with FaceTime, Google Voice or Skype. Data-based calls, especially ones with video, can quickly use up a limited data plan.
How Other Phones Can Use Data While Calling
Some cellular phone manufacturers have a hardware-based solution to let smartphones on Verizon's network use cellular data while making calls by adding a second cellular antenna. Wi-Fi and cellular use different antennas. The only way to connect to both 3G and 4G at the same time is to incorporate a third antenna in the device. Adding a third antenna inside the device takes up more space and can hinder cross-carrier phone development when allowing for some phones to have an extra antenna. Apple opted out of including the extra antenna in LTE-compatible iPhones.
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