Recently, I have noticed that my phone's wifi status is continually showing data transferring. That is, the arrow in the upper left corner of the status icon is always being displayed.

I am sure that this was not always the case. In the past, even recently, the arrow was not displayed most of the time, showing up only when I was actively using the network or, in some infrequent cases, when the phone needed access to data for some background task.

The main reason I noticed this was that battery life on the phone has been drastically shorter than normal. I don't use the phone very much, and can typically go days, sometimes as long as a week without charging the phone. But since this has been happening, the phone will go from fully charged to only 80% just overnight while I'm sleeping.

If I disable wifi before bedtime and have charged to 100%, the phone is only down to 99% by the morning.

I have disabled all of the obvious potential suspects I could think of — uninstalled Skype, turned off auto-updates, turned off auto-backup, all sync options I could find — as well as some other stuff that I think shouldn't be related, just in case (like location services).

The only thing that has been different recently is that I used a hotel's public wifi last week; they use a service provided by a company called Roomlinx. But I haven't heard of any Windows Phone virus that can infect my phone just from being on the public network.

I looked in the Data Sense app, but it doesn't show any volume of activity that seems large enough to account for data being transferred over wifi 24/7. The top app is a Windows Store download of 91MB when I reinstalled Skype after having removed it to check to see if it was the cause (it didn't seem to be). The second largest app is the Weather app, with only 13MB of data usage.

  • Are there any other tools or diagnostic techniques that I could use to track down what's keeping my wifi busy all the time?
  • Are there any "known culprits" for this kind of behavior? I've done searches on the web and here on the Windows Phone Stack Exchange site, and couldn't find anything that seemed relevant.
  • have you checked data sense? – Rowland Shaw Dec 21 '15 at 21:53
  • 1
    @Rowland: Yes. As I wrote above: "I looked in the Data Sense app". – Peter Duniho Dec 22 '15 at 6:38
  • That is the diagnostic tool that the phone has... – Rowland Shaw Dec 22 '15 at 16:01

Ultimately, I was unable to determine for sure what the issue was here. However, I do have a strong suspicion. Last month, engineers at Google and Cisco released a memo describing how misconfigured Wifi routers can significantly impact portable devices' battery life by transmitting network advertising packets with excessive frequency.

This issue persisted for me while I was in range of the hotel's Wifi network, as well as in the home of people I was visiting. But the problem stopped as soon as I got back home from traveling. Using two different make/model of router at home, I'm not having any trouble at all.

So the evidence strongly suggests that the problem was dependent on the Wifi network to which I was connected, which in turn strongly suggests that the configuration issue described by these engineers was related, if not the root cause.

There is a summary of the memo and its implications that was published on the International Business Times web site when the memo came out. You can read that article here.

As far as finding tools for diagnosing the issue, I was unsuccessful. I would have liked to have found something like Wireshark that would work on my Windows Phone device. Unfortunately, there doesn't appear to be anything like that.

Just for the record, users of other phones might be able to take advantage of tools that do exist. For older Windows Mobile 5.0 phones, Microsoft actually has a network analyzer kit that one can install if you have a development workstation configured to install software on the found.

If you are using an Android phone and are willing and able to root it, there is a tool called Shark for Root that will generate network trace files that are viewable using the desktop version of Wireshark.

At least one person has used Wireshark on a machine configured to route traffic for a separate mobile device, so that he could monitor the traffic his Windows Phone 7 device was sending and receiving. Unfortunately, that particular article has broken links to the inline images, but an enterprising individual can get the basic gist from the article to implement a similar solution.

Finally, a team of researchers from University of Texas at Austin, University of Wisconsin-Madison, and Microsoft Research India uncovered potential battery-draining behaviors related to the sleep/wake behavior of mobile devices and the interaction with a protocol called (ironically enough) "Power Saving Mode". An article on MIT's Technology Review web site describes this particular issue. This might be something people seeing similar issues could be experiencing, if not the IPv6/ICMP problem recently described.

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