Android poor at access point handoffs?

[BenYL]

This Dev 2 phone doesn't roam well between WiFi access points in the office. We are trying to setup a VoIP network, but Android waits until the signal is very weak before negotiating a hand-off. iPod does it much better. Can I tweak this, or it is tied to the hardware or some low-level driver? Is it SIPDroid fault?

Ben