Another Android storm is brewing, and this time it is over reported signal drops on the GSM Galaxy Nexus after upgrading to Android 4.0.4. The problem was first reported in late March as users either received an OTA update directly from Google/Samsung, or by loading a custom ROM with the new AOSP build. The issue has been generally isolated to 4.0.4 though some users have said the issue is present on 4.0.3.
According to an XDA member, this the way to attempt to recreate it: “The issue as described is very easy to replicate – turn off wifi and then turn off the screen. Wait 5 minutes and try to call your phone – it will not work if you have this issue. When you power the screen back on you may see that you have signal, this looks to be just a cached image, after a second of so you will notice an “x” in the signal bar.”
The behaviour seems to be occurring only when the screen is turned off: once turned on, the Galaxy Nexus baseband will reach out again to the network and obtain a 3G signal. However for many users it is preventing them from receiving calls, notifications and text messages when idle in a pocket or on the table. It seems that the baseband is dropping a signal at certain CPU speeds: anything under 700Mhz is low enough to cause a break. And because of the way the Android kernel optimizes battery, by dropping CPU speeds based on predetermined governor to around 350Mhz when the screen is off, this is causing the problem. Rooted users who engage a performance modification app such as SetCPU are finding the problem abating when manually setting their minimum CPU speed to 700Mhz.
The problem is not universal, either: there are many users commenting in the threads peppered around XDA, RootzWiki or Google’s own Android Support site saying there is no issue, and are finding it impossible to recreate it. It hasn’t been isolated to a signal kernel (it’s present on stock and custom ROMs with modified kernels) nor a specific radio build (though Google recommends I9250XXKK6/7 for any user running Android 4.0.3 or 4.0.4).
A Google employee has acknowledged the problem in the Android Issue Tracker forum, and is asking users who are experiencing it to send in log files for reference. Unfortunately for users running stock Android 4.0.4, the only way to alleviate the issue is to either root your phone and change the minimum CPU speed, or to downgrade back to 4.0.1 or 4.0.2, each of which had problems of their own.
Are you experiencing this signal loss bug? If so, have you been able to solve it? Let us know.