At my house, it is a DEAD zone and regardless of what technology AT&T is working on, I don't see them fixing my DEAD ZONE any times soon. I have been living here 3 years now, complained the first week we moved in, about the dead zone. AT&T's solution was to give me a M-CELL for my house. Doesn't help me if I am outside my house, outside the range of the M-CELL, I will be lucky to get 1 Bar for Cell Service. With the advent of WiFi calling w/ AT&T, i am thinking of returning the M-CELL , but not sure how well the WiFi calling works, but again, still have issue when I am outside the range of my WiFi. I just looked at AT&T's coverage map for my area and it states I should have HD Voice. Not with 1 bar. I love the service when it works and I have been with AT&T for years. Not ready to switch, just hoping the will address this issue one day.
We have the same problem, and have been using WiFi calling for about a year before getting a Microcell. The problem with WiFi is that it's shared spectrum with other devices. Your home and office WiFi network (as a whole) will slow down to the speed which the furthest device can connect reliably to the network.
WiFi networks will automatically re-negotiate speed to increase speeds. If your on a phone, and you move your head, there will often be a noticable blip, as the network re-negotiates speed. Lost voice packets become much more apparent in HDVoice calls, and I've even noticed people talk like chipmunks when 3 or 4 seconds of voice data can be delivered reliably across unlicensed airwaves.
So let's look at WiFi and the standard.
First, the newest WiFi standard is 802.11ac can be configured to use up to 160Mhz in the 5GHz band. Using 160Mhz of total air space for internet is near to the total amount of airwaves Verizon has IN TOTAL over it's entire network. 802.11ac is designed for distances of 230 feet indoors.
To compare, and on AT&T, a microcell/femtocell usually provides a 5x5MHz channel (10Mhz total) dedicated only to devices you approve. Voice is very low-bandwidth; only needing 60-70kb/s. Your Microcell uses AT&T airwaves and spectrum, which is NOT shared with other consumer devices like cordless phones, microwave ovens, wireless security cameras, WiFi Boosters, and other devices which may interfere with spectrum and the same airwaves WiFi uses.
How blips happen.
So, when interference is detected, WiFi will disconnect/drop and re-negotiate to a new speed, new channel selection isn't automatic for most consumer-grade routers. Generally this takes less than a second. WiFi 802.11ac 5GHz standards alone may negotiate to speeds of 65, 130, 195, 260, 390, 520, 585, 650, 780, or 866.7 (or 58.5, 117, 175.5, 234, 351, 468, 702, 780 if the Guard Interval is disabled on the WiFi network). WiFi calling is worthless on a network with a booster attached. Depending on WiFi router manufacturer, a noisy channel isn't re-selected unless you unplug your router.
People whom have a WiFi 802.11ac router that has 802.11b/g/n enabled for older devices like a laptop, an iPad 3 or AppleTV won't be able to reliably use WiFi calling. As devices connect, and even attempt to logon (WPA2 negotiation) the router can re-negotiate to an earlier standard such as 802.11b/g/n, and in-turn slow everything on the wireless network down further. So, when b/g/n/ac standards are also enabled on a router (often the default), the router may re-negotiate across an additional 20 speeds in the WiFi standard- 15, 30, 45, 60, 90, 120, 135, 150 / 802.11n with guard band enabled= 13.5, 27, 40.5, 54, 81, 108, 121.5, 135; 6, 9, 12, 18, 24, 36, 48, 55 for 802.11g, and 1, 2, 5.5, 11 for 802.11n.
In total, this means up to 30 different speeds would need to be negotiated and re-negotiated on a newer router (like the one sales person at BestBuy or T-Mobile said you needed to make a reliable phone call... right..?) and the likelihood of unreliable calling grows exponentially.
How to fix these pain point problems.
802.11 standards were not built for services that require QoS like voice phone calls. My experience has been that it's best to use a Microcell, which only negotiates a LTE connection on spectrum licensed to the provider.
The best way to handle these issues is actually very simple- Don't sell service to people whom can't get a signal. In situations were a customer has to bear the costs of an ill-designed network exists, those customers whom can't get a signal should be a priority for network expansion and investment. As a customer, it's also best to choose companies that make it a company priority (in investment) to fix network coverage problems instead of giving out band-aids and a crutch in the form of Microcells and also expect customers to use WiFi calling. By piggybacking on DSL/cable and broadband networks for making a phone call, the service doesn't work on its own.
What a carrier can do.
For companies like AT&T and Verizon who provide microcells, they already know the address where coverage is terrible, and those areas should be on a hotlist for network expansion. Customers are forced to pay a third party for service the provider shouldn't be able to brand itself. Maybe it should be more accurate; with additional fine-print. Something like "T-Mobile service powered by Verizon FiOS" or "AT&T service powered by Comcast cable" or something along those lines.