The craziest part of Project Fi is that phone calls and network connections do not drop at all while it is switching carriers/WIFI underneath -- there is a lot of low-level networking magic happening here, and the crux of this tech. I hope some day Google will release some code or white paper on this.
- I'd love to read a more indepth analysis about how /well/ this interface/service provider-switching works.
- I want to know if the signal/coverage is comparable or better than Verizon (which IMO has the best quality+coverage in the parts of the US that I've travelled; all over the west coast & hawaii).
You mean they've solved the problem where your phone is useless for 30 seconds after you walk out of your house and lose WiFi? I'd almost switch for that feature alone, if true.
Unfortunately, no. I have Project Fi and this is still an issue. They may only have this feature when actually on a call, since I imagine it uses a lot of power to constantly poll for the power of networks. I can still hope that they'll fix it though.
Could you go more in-depth on your experiences here? Your opinion seems to differ with the review, which refers to it as seamless. It is the main feature I am interested in as I get anywhere from two to zero bars in my apartment complex but have a fairly strong router and would love to have it transition without dropping as I am walking home.
If I am on a call, it's seamless - no issues there. However, it doesn't seem to work for data in general.
I commonly try to get Google Maps directions as I leave the house, and often it just fails since it's still trying to use my WiFi which is too far away to be useful.
I am not sure whether Project Fi uses this technology but Apple have been using Multipath TCP [1] for a while. I think Apple's implementation is limited to data, in the conventional sense, rather than data+voice.
Carriers with wifi calling already manage to transfer calls between wifi and the cell network. However, maintaining network connections between the two is impressive, and quite useful; that makes it much more reasonable to set up various wifi networks and use them seamlessly.
This is a decent article on some of the underlying standards: http://www.radio-electronics.com/articles/cellular-telecoms/... I worked on an implementation of an IPSEC VPN using SIM auth for IMS. GSM standards are amazing in how they make everything work together across many different generations.
The smoothness of this (if it is substantially better than existing VoLTE+Wifi implementations) more than likely has to do with improvements in the handset Wifi implementation and the underlying network evaluation criteria, etc.
Put simply, handsets that are capable of this (and there are many) typically establish an IPSEC VPN back to the IMS network core. When the IMS network needs to switch between cell and IP+IPSEC (usually over Wifi) it is no different than the handoffs that have been happening between individual cell towers since the beginning of cellular. To many aspects of the network the IPSEC VPN looks just like another cell.
The tricky part here is getting the timing right - this is the real reason cell providers and sites have such precise and well coordinated time.
I don't have any experience with it and I haven't seen it work but more than likely the handoff between VoLTE capable carriers is accomplished using similar methods.
- I'd love to read a more indepth analysis about how /well/ this interface/service provider-switching works. - I want to know if the signal/coverage is comparable or better than Verizon (which IMO has the best quality+coverage in the parts of the US that I've travelled; all over the west coast & hawaii).