Hi Laura,
I'd add my favourite articles of Devin Akin, they apply to wireless connectivity in general but naturally also have influence on WiFi Calling that might be a delicate kind of traffic:
http://divdyn.com/top-ten-tune-tips/
http://divdyn.com/wi-fi-throughput/
http://divdyn.com/moo-mimo/
Hope that helps,
Tomasz