How often does an IPhone with iOS7 turn on WiFi and send Probe Requests

To look up it’s current Position Smartphones continiously send out WLAN Request to use the Responses for Positioning. The Response includes the SSID of a Access Point close by. This Information can be used to look up in a database and find out the rough position (~15 meters).
This cost a bit of energy though no that much that it would have a big impact in use batterie. And it consumes even much less energy than GPS would.

Normally this lookup happens every 10sec, 30sec, 90sec.  But since the last iOS Update iOS7 it changed fundamentally the behavior of those Lookups on the IPhone.

Experiment with active IPhone:
(time difference to next probe request in sec)
3, 8, 4, 8, 21, 9

Experiment with sleeping IPhone on table:
(time difference to next probe request in sec)
479 (~8min after turn off the screen), … (15 minutes later stilll nothing !)

Experiment with sleeping IPhone in pocket:
still nothing

With iOS7 wifi seems to by totally switched off. Or at least it doesn’t send a single probe request.
Maybe it still monitors the WiFi traffic but i was not able to check this.
 

Capture WiFi / WLAN / 802.11 Probe Request with tcpdump

A Probe Request is a special type of WLAN frame sent from a terminal-device (for example your smartphone) to ask all AP nearby for their presence. [..]

The blog post moved:

HERE Capture WiFi / WLAN / 802.11 Probe Request with tcpdump