hey, i made a thread over at xda on the nexus 5 e.csfb issue, that helped me -
http://http://forum.xda-developers.com/google-nexus-5/help/nexus-5-e-csfb-issue-t2729014
from within that, i delved into the inner working of sprint half baked network vision set-up nationwide,
what i found, is that the LTE part is actually an overlay on the cdma / evdo network (with sprint), so in essence, it's two separate networks the triband phones with single radio paths have to inter-roam between (or hand-off) to & from from data to voice services, & why they can't do them both at the same time.. when we at times saw *roaming* with full LTE service in incoming calls, it wasn't a flux, the nexus 5 was ACTUALLY inter-roaming within the network, from the LTE channel to the 1xrtt channel to serve the call..
somewhere in between, the phone app would get hung up in the processing because there was a fault on the network side -
i suspect when the google dialer froze on incoming calls, it came from the worse case scenario here ( it didn't happen all the tyme, but sporatically) -
"Call setup reliability
Another key issue for the voice call user experience is call
setup reliability—the ability to successfully establish an
incoming or outgoing call on the first attempt, or within
a time frame that doesn’t indicate call setup failure. The
target is to at least match legacy performance, which is
in the 98% range.
With CSFB switching between LTE and 3G networks, there
are two primary challenges to call setup success: changes
in IRAT conditions between measurement and acquisition
(for handover-based CSFB), and mismatches between
LTE and 3G geographic signal coverage areas that require
server-side updates.
Changing IRAT conditions for handover-based CSFB
With handover-based CSFB, IRAT measurements can
change between the time the measurement is taken using
LTE and the time 3G voice network acquisition is attempted.
In that time, the cell identified and prepared for handover
may become unavailable, resulting in connection failure,
as visualized in Figure 10.
In handover-based CSFB, the measurement is performed
before—on average of 0.3 seconds before, as shown in
Figures 7 and 8 above—the IRAT transition. If the IRAT
conditions change negatively, there is a higher probability
of handover failure, especially in high mobility situations.
Historical experience has already shown somewhat
higher failure rates with inter-frequency handover or
IRAT handover (e.g. 3G to 2G), suggesting that delays
between IRAT measurement and network acquisition
can increase setup failures.
In contrast, redirection-based CSFB can be expected to
deliver higher call setup reliability than handover-based
CSFB, simply because redirection-based CSFB takes the
IRAT measurement immediately before attempting access
on the identified cell. Since the Release 9 SI Tunneling
and Release 8 Skip SIBs redirection-based CSFB methods
have only slightly higher call setup times, their higher call
setup reliability has guided the general industry trend to
rely on redirection-based CSFB approaches.
The reliability of redirection-based CSFB call setup has
been tested using device traces in field testing on live 3G
networks, and no call setup failures were observed out
of more than 160 calls, covering both good and bad RF
conditions for redirection-based CSFB to UMTS. These
results point to call setup reliability on par with legacy call
setup reliability. Similar traces collected on the network
side showed redirection-based CSFB reliability in the 99%
range, on par with UMTS legacy performance. Test data
for handover-based CSFB reliability has not yet become
available, due to its limited use to date.
....
the dialer app froze on totally different parts of town in my home in the suburbs, & inner city at work, i know not the particulars of the kind of sprint sites i was connected to ( was hoping to get that help from s4gur), allowing automatic in system select migitated the dialer freeze on incoming calls, to nil.."
that's where ehrpd comes to play, to *BRIDGE* lte & cdma / 1xrtt for seemless hand-offs, **lte doesn't have the capabilities for circiut switching within it's framework, cdma does, but, lte needs a flattened IP (internet protocol) bridge to evdo data, which then splits to 1xrtt for voice, for seemless transparent work..
on the time thingy, cdma should provide automatic network time sync from the cell sites to your phone, since those very towers are gps sync'd.. obviously when parked in LTE, that link somehow, was broken..
