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Re: M8 and SVDO
Yep I'm positive. If you'd like to read a well written article on it you can read this. Nexus 5 and LG G2 experience temporary Sprint LTE connectivity issues due to Circuit Switched Fallback technology - Sprint 4G Rollout Updates
Originally Posted by doc31
However, the important part is this if you don't feel like reading it.
"Sprint Triband LTE phones dropped SVLTE for eCSFB/CSFB
Up until these new Triband devices, previous Sprint LTE devices supported simultaneous voice and LTE (SVLTE). It could do so with two separate transmission paths from the antennas to the chipset. Voice/texting could run via 1xRTT on one transmission path. LTE could run a separate path, allowing data and voice to be used simultaneously.
In contrast, Sprint Triband LTE devices do not support two separate transmission paths. They have one path, shared by voice/SMS and data. We were alerted to this months in advance. However, we did not realize that the network would have to run on Circuit Switched Fallback in order for this to work and what the ramifications of this would be.
S4GRU was told by a source this past summer that Sprint and the OEM’s came to the conclusion that these new Triband LTE devices could not use SVLTE in the conventional way they used to, and it would require a lot of engineering, testing and cost to even attempt such a design change. It was decided to release Triband LTE devices without SVLTE. It may seem that the only drawback for doing that is Sprint Triband LTE devices would not be able to run simultaneous LTE data while on a phone call or when actively transmitting a text. But there is another. And it’s why many early adopters of these new Triband LTE smartphones no longer are being able to connect to Sprint LTE in many places that they used to.
How it works
In previous Sprint LTE phones, when a device was in Sprint LTE coverage it would park in both the LTE and CDMA Sprint networks at the same time. When a voice call came in, it would just go straight through to the device. And signal to the LTE network would be maintained the whole time while the call was active.
In contrast, a Sprint Triband LTE device can only stay on one technology at a time. CDMA or LTE, not both. So when a Sprint LTE Triband device is in Sprint LTE coverage it parks only in LTE. And doing so means it cannot transmit calls without Circuit Switched Fallback (CSFB) on the network side. CSFB and eCSFB (Enhanced Circuit Switched Fallback) are network controls that will allow a single mode/single path network to operate in two modes, both CDMA and LTE."