Let me start this reply stating that all of my observations are speculation based on the behavior I've observed on my phone.
Initially, I set up my iPhone 6 by using the iTunes backup I had made from my old iPhone 4. This turned out to be a big mistake. I had major wifi connectivity issues. I contacted Apple Support. They told me to restore the phone and then set it up as a new phone.
I did this. And still had problems.
I made an appt to go to the Genius Bar because I was experiencing wifi connectivity issues, but when looking at my log I had tons of seld_yyyy-mm-dd-hhmmss.iphone6.ips crashes. They gave me a new phone. Since I was determined to 'get it right', I stayed there with my laptop and took the new phone, updated the os to 8.0.2, and restored from my current iTunes backup. While in the store, I lost wifi connectivity and the "seld" crashes started.
At this point, I wiped the phone and set it up as a brand new phone (still at the Genius Bar). At first I didn't load any apps. I didn't get an seld errors and managed to stay connected to wifi. I then loaded about 6 apps on the phone, opened them up, played around some more, moved some music from iTunes to the phone. I remained connected to wifi and no "seld" crashes in my log. I do get my share of stacks+backboardd crashes.
Arrived home, connected to my wifi. Here's my observation, while I'm using the phone I remain connected to wifi. Once the phone goes to sleep for an extended period of time, and when I wake it up, it may or may not be connected to wifi. Most of the time, it will immediately connect to my wifi. Every once in a while, it'll try to connect to wifi, then immediately switch to 4g/LTE. If I go into Settings/Wifi, I cannot find my home network or guest network. If I put the phone to sleep (i.e., lock it), even for 30 seconds, then wake it back up, it'll reconnect to wifi.
I went into my router's settings and looked at the list of attached devices. I have a NETGEAR WNR2000v2. What I observed is that my iphone will drop in and out of the network while it is locked/sleep. The odd thing is that sometimes it doesn't completely drop. What I see is the MAC address listed without the device name or ip address (shows all ---- in these columns). It looks like it's in somewhat of a semi connected state (not sure what this means). Anyhow, while in this state, I decided to connect my laptop to my network to see what ip address would get assigned. My router did assign it to an unused address. I then tried to wake up the phone. Blammo. Couldn't connect to my wifi. I even started noticing degraded speeds in my network. I also want to add that I already have WMM enabled and am using WPA2.
So here's what I did. I went into my router and assigned my phone to a static ip address that would probably never be used (192.168.1.100). I then reset the network settings on my phone. When I connected to my home network on my phone, I then went into the settings for that connection, and updated the Static tab with the all of the same settings.
After all of this, here is what I've noticed. I seem to connect to my home wifi almost 100% of the time after waking up the phone. I did lose it one time after waking up the phone, but it reconnected.
To me, it appears to be an issue between my router and my phone.
My sister came over today. She has iphone 4s that is updated to ios 8.0.2 When she connected to my network, and put her phone to sleep, her phone totally disappeared from the list of attached devices. Hers didn't show up as a phantom device like the iphone 6 does when iit is asleep. My husband has an Android. His phone never drops from the network (even when it is asleep).
What all of this leads me to believe is that the new phone is not totally removing itself when it goes to sleep and when you wake it back up, it may or may not reconnect because of some glitch between the phone and the router. As other devices try to attach to the network, I'm not sure what my router wants to do with the ip address assigned to the phone (is it available or not?) For me, setting a static ip on my home network to an address that would never get used has re-mediated the problem somewhat.
I still would like to understand what the nature of the conflict is and Apple should have built this to work cleanly with all types of routers. Clearly, not everyone has an Apple Air Port Extreme!
