There’s one thing about this discussion that’s bothering me.
Cellular phones are a specific technology and protocol set, all the way down to Layer 1. They are designed to handle the things that we are talking about. They use ATM instead of IP to improve the likelihood that these problems will occur. Transit times are minimized because of traffic shaping and lots of other technological advantages that we’re not going to be able to do.
Expecting a WiFi connected device (phone or not) to work over VOIP is just not reasonable.
Sure - we can simulate the things that make cell service work. For example, we can set up a wireless router that handles nothing but VOIP traffic, but as soon as we walk out into the real-world, we’re subject to the vagaries of non-prioritized traffic, long transit times, IP routing delays, etc.
Also, while every phone provider on the planet will deny it, I’m of the opinion that they deliberately mess with VOIP traffic over their 4G networks. If you are anything less than 4G, it’s a pipe dream to hope that your 256kbps asymmetric data connection is going to give you crystal clear connectivity.