[Motorola Atrix HD] IronTechmonkey:
On a new Motorola Atrix HD, in a well serviced area, with a full signal strength indicator and the phone having not been moved:

After a period of time (could be 30 minutes to several hours) although the phone shows full bars and a 4G connection, when a call is dialed from the phone it behaves as if it is not on any network and it re-initializes its phone network connection, going through the various icons and network types (no service, emergency calls, 4G ) until it gets to 4G and then the call goes out. While the phone is in that limbo state with full bars and 4G LTE icon it is receiving wireless waves (this is proven) but is not being given the proper command to switch to phone answering mode when a call comes in so the calls go straight to voice-mail and no alerts for missed calls or voice mails are sent to the phone... until the process of making an outgoing call from the phone forces it to re-find the network. Toggling data plan or airplane mode on/off also resets the phone network connection. Then incoming calls and voice mail alerts come through until the next instance. It is also possible that the phone is indeed on the network when the problem is in evidence and that some failure in the network signal or OS on the phone prevents it from changing state to answer the call. This has been happening several times a day for 3 weeks.

ATTEMPTED REMEDIES

- Data refresh (short of factory reset)

- Factory reset

- New sim

IN PROGRESS REMEDIES

- AT&T has forwarded this to engineers who will supposedly look deeper into the relationship between my phone and their service, and I hope, at particular slices in time where the incidents have occurred (I'm keeping a log of the incidents).

PLANNED REMEDIES

- Replacement phone. I will test the new phone before applying any available OS updates or installing apps.

ELIMINATED POTENTIAL SOLE CAUSES

- Disabling of certain native apps. Problem occurs regardless of which apps I have disabled and occurs with all native apps enabled.

- Phone being moved in and out of range. Problem has occurred and testing has been done at one location.

- Service outage at all towers within range. No significant degradation of service during problem incidents.

- Deep sleep mode. Phone goes into deep sleep mode properly and receives calls while in deep sleep mode when the problem is not in evidence.

- A particular app that can force phone to use 4G without LTE has been eliminated as potential cause, as the problem started before that app was ever put on phone and persisted for a week after factory reset and rebuild that did not include that app.

- Duration of idle time. The problem has been detected anywhere from 25 minutes to many hours after the phone was last used.

- Developer Mode USB Debugging. Problem occurs regardless of this setting.

Getting more granular:

For those having this issue on an AT&T 4G LTE phone this may be significant in determining the exact moment that the phone is failing to do something it should, which in turn may help get to the root cause of the problem.

- With data plan off and background data disabled the phone shows a greyed-out 4G LTE data network indicator without radio wave graphic elements. With data plan on it shows the same indicator not greyed-out and with radio wave elements.

- Under normal operation; When a call is placed to the phone (in this case from a land line), well before the ring is heard on the mobile phone and sometimes even before the ring is heard on the calling land line, the LTE part of the indicator turns off and then the call comes through. (The LTE indicator is also turned off when an outgoing a call placed from the mobile phone)

- Some moments after the call is ended the signal bars drop to zero very briefly then the LTE indicator reappears and the bars go back up.

- When the problem of missed calls/vms is in evidence the LTE part of indicator never goes off when a call is incoming and nothing short of manually toggling the network state of the phone seems to set it right

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ADDITION 3/12/13 relating to “Modem Fastdormancy Monitor Service”

- Under normal operation, when a call is placed to or from the mobile phone a process named “Modem Fastdormancy Monitor Service” is invoked. This process seems responsible for toggling the LTE component off during the call and back on when the call is complete, after which the “Modem Fastdormancy Monitor Service” closes its self.

- When the problem is in evidence the “Modem Fastdormancy Monitor Service” is never invoked, the LTE indicator never disappears and phone calls go straight to voice mail even though the phone is, in a technical sense, receiving wireless waves.

- When the phone is forced to use only 4G (instead of 4G LTE) the “Modem Fastdormancy Monitor Service” runs continuously and the problem does not occur. The app that allows this test to be performed has been eliminated as a possible cause.

So... it is at the point during an incoming call when the “Modem Fastdormancy Monitor Service” is supposed to be invoked but is not being invoked that the phone or network is failing to do something. Determining exactly what event invokes the “Modem Fastdormancy Monitor Service” may isolate the failure point and get to a solution.

Here is some hard tech detail about the “Modem Fastdormancy Monitor Service” found by a helpful Motorola tech.

http://www.faqs.org/patents/app/20120124196

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I’m curious to know if others are experiencing this.

Stock ROM, No Root, some reasonable apps installed

Model: Motorola Atrix HD MB886

System Version: 98.4.20.MB886.ATT.en.US

Baseband Version: MB886_BP_100740.071.65.04P

Kernel Version: 3.0.42-gebf622ceaz002@fl36bld22 #1

Android Version: 4.1.1

State: NY