http://www.macnn.com/articles/09/06/18/att.iphone.handoffs/
AT&T using 802.21 for handoff of iPhones to Wi-Fi?
updated 04:25 pm EDT, Thu June 18, 2009
AT&T iPhone handoffs
AT&T may be adapting a new protocol to relieve pressure on its 3G network, reports say. The 802.21 protocol may be responsible for the new prompt-free process of automatically transitioning an iPhone from 3G to one of AT&T's Wi-Fi hotspots. The technology is designed to switch to and from cellular, Wi-Fi, Bluetooth, 802.11 and 802.16 networks using handover algorithms.
Whether or not it uses 802.21, the process is being called "auto-authentication" by AT&T and eliminates the previous two-step process of switching between networks. The feature becomes available once the iPhone 3.0 firmware is downloaded. The upgrade was released through iTunes on Wednesday.
Fresh-Faced Recruit
Joined: Jun 2004
Not sure..
I have a WPA-encrypted wifi network at work. Every day I come into work, turn on my iPhone, launch Safari and within seconds I'm connected. When I leave the office I'm back on 3G. So what is this auto-authentication doing for me that I didn't have before?