[canook]

Why did RIM choose to implement Wifi calling over UMA for the 9900? UMA was great because the network would seamlessly transition from Wifi to carrier network once you stepped out of range. With stupid Wifi calling I have to hang up and recall someone, as well as that incredibly annoying sound you hear every time wifi signal gets a little low.

Anyone have a proper technical explanation for this?

[habs_fan]

i heard that uma doesn't work over the HSPA networks, so thats why they have just wifi calling

[Phill_UK]

Anyone have a proper technical explanation for this?

It's all explained in detail here... T-Mobile BlackBerry Bold 9900 Won't Use UMA for Wi-Fi Calling | CIO Blogs