That Android is Quite the Prober

No bold type introducing today's post, as I'm going to keep things short.

I was doing some work last week looking at Android devices (specifically, a Samsung Galaxy Tab 2) and I noticed some very heavy probing behavior.  We were checking out the device's behavior when it moves from AP to AP, so I set a capture for the target second AP.  I did the test (things went fine, but the WiFi Analyzer app in particular seems to really make Android devices stick to their currently associated BSS) and looked at the capture.

Seeing a ton of Probe Requests from the Tablet was expected.  What wasn't expected was the Android tablet probing even while associated to the first AP.  Even when the received signal was strong (in the -50 to -63 dBm range), the Android was going off channel to probe and probe excessively.

At this point I'm still trying to figure out if physical motion or an app (or lack thereof) caused the probing.  One thing I am pretty confident in saying already is that updates to Android OS and iOS (the one for iPads and iPhones, not the Cisco one) have really seen the two leaders in mobile operating systems take divergent paths concerning WiFi overhead.  Apple seems to be making their smartphones and tablets probe less, while Android devices are probing just as much, maybe even a little more.

Comments

  1. UnknownJune 4, 2013 at 12:58 AM

    Great post!

    I recall the Galaxy Tab 2 completely getting paralyzed on our office network - but not at my home for example. I started logging and noticed the driver worked OK for about 30 seconds, then started choking, and after a few minutes the driver just restarted itself. The process then repeated as long as Wi-Fi was enabled.

    We have every brand of Wi-Fi infrastructure running here, so I'm guessing perhaps one of the vendor APs was sending "exotic enough" packets to kill the Samsung Wi-Fi driver.

    Didn't see this on the other tablets or phones.

    After testing about 50 different Android devices, I have to say the Wi-Fi performance varies a lot: Scanning performance, RSSI readings, throughput, stability, all of that seems to very very much depending on the device.

    It would be interesting to see if the frequent probing is a general Android problem, or something Samsung has done to "optimize" the driver? Wonder if you'd see the frequent probing on vanilla Android, like the Nexus 7?

    Cheers,
    Jussi Kiviniemi / Ekahau

    @jussikiviniemi

    ReplyDelete
  2. Ben MillerJune 11, 2013 at 10:19 AM

    That's a great point. It may be as much a Samsung thing as a Google thing. I'm going to spend more time looking at it soon.

    ReplyDelete
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