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I own multiple access points that braoadcast same SSID. When a WiFi enabled device such as a phone connects to one of the WiFi access points, how can I determine the location of that device?

Is it possible at the AP side to find out signal strength that the device gets, and then calculate the distance based on that information? The devices that are connecting to these access points don't run any software component that I own (so that I could query the location from the device).

xdev
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  • possible duplicate of [Wifi position triangulation](http://stackoverflow.com/questions/16485370/wifi-position-triangulation) – paisanco Jul 04 '14 at 04:44
  • there a rew a few wifi positioning system pieces of software out there you can look into, such as navizon, but it's not particularly easy. You are correct, however, in that signal strength is the best way to determine the location of the device. – John C Jul 04 '14 at 04:45
  • Have a look [here](http://stackoverflow.com/questions/6368538/determining-a-location-based-on-wifi-aps-and-signal-strength).Also, if you are trying to locate the user indoors, have a look at BLE used in conjunction with Bluetooth beacons. – canopi Jul 08 '14 at 07:50

2 Answers2

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In fact this is not as easy. You can't use signal strength as a distance equivalent. In fact if you have some obstacle (wall, people...) the signal will not be proportional to the distance. 

         O
         B
+---+    S     +---+                                         +---+
|AP1|    T     |STA|                                         |AP2|
+---+    A     +---+                                         +---+
         C
         L
         E

In this case, you can have a better signal with AP2 than with AP1.

Nevertheless, you can easily determine if the STA is connected to AP1 or AP2 as each 802.11 frame have:

  • Source mac address:
  • Receiver mac address
  • Transmitter mac address
  • Destination mac address
+----+                                       +----+
|STA1| Source                    Destination |STA2|
+-+--+                                       +----+
  |
  |          Transmitter        Receiver        ^
  |          +---+              +---+           |
  +--------> |AP1|              |AP2+-----------+
             +-+-+              +---+
               |
               |                  ^
               |                  |
               |                  |
               +------------------+
                  via ethernet

So if you are the source, you can send a frame (ping...) and check the for the transmitter address. This way you will have the mac of the AP that you are connected.

jmlemetayer
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-3

Maybe you can use ping to check the delay between device and APs. Bigger delay means longer distance.Then you can calculate the location. That's just a suggestion.

Stephen Lin
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