Roaming access point wifi phones

We are looking are replacing our aging NEC phone system with Asterisk.
However we are wanting to add a number of cordless VOIP Wifi phones.
Here are the issuse.
We may have up to 24 wifi phone using 8 access points scattered about the buildings.
If a phone starts a call while connected to access point A and moves into access point B, when access point A becomes too weak to support the connections, what happens?
Is the call dropped?
Is there a delay and then a reconnect?
Or is it seamless?

Spectralink has phones that are seemless but they won’t support Asterisk. discusses the problem, but I am still confused.

Hi I have tested this with the Hitachi WIP5000 and Linksys APs and it does handover. You can get a break in RTP stream though. For a more enterprise grade solution look to Meru networks.

The UTStarcom phones (F1000G and F3000) will have over from access point to access point - so long as all are on the same subnet with the same SSID (same DHCP address stays put). The hand over is not what I would call seamless, but it is OK and the phones are considerably cheaper than the Spectralink phones. Also, the phones do not have the range of a PC, since they are lower power, so you may need access points closer together than you would otherwise for just PC connections. We use them with 3 access points (one Linksys WRT54G with a router and 2 “slave” access points plugged into it) and they work OK.