[Hypnotic2010]

EVDO spec does not support simultaneous voice and data. EVDV did- but EVDV is dead- abandoned by all the major carriers in favor of lte/wimax. The reasoning behind this is voip. There is no need for separate voice and data signaling. Voip allows for a single stream that supports all functions. Just like you can stream radio, surf the web and send email at the same time. VoIP lets voice just become another application. All that you need to ensure is that the end user device and network can tag and prioritize the voice packets and have a data connection that is low in latency, jitter and has the capacity to support the call. (not much bandwidth is required) 4g is capable of all this.

Sprint's PPC-6700 device allows WiFi and EVDO (data transmission) to be active simultaneously, however if your phone rings (voice transmission), you drop the data transmission. It's one or the other. Some of it is a technology issue. That is, the chipsets used by the cellphones share the same antenna and can only transmit using one of the wireless standards. Other times, it has nothing to do with the technology - the service provider simply decides to block simultaneous voice & data transmission for the sole purpose of protecting their turf. Perfect example - XV6700 Windows Mobile 5.0 phone (Verizon's exact same model as the Sprint PPC-6700) is restricted to only one network at a time. If you turn on WiFi you can't even receive cellular calls. This forces users to stay in "voice" mode the majority of the time, otherwise you can't receive any phone calls.