1. Confirmed wireless connectivity at work and at a friend's house - so far, it's working great everywhere but home. Looks like my home router isn't playing nice with the Intel wireless adapter. (It was working fine with Ubuntu 12.04 on my previous laptop.)
2. Tried to update firmware on router. Xfinity (Comcast) insists that they do regular firmware updates to this model (Arris TC862) themselves, which I can only hope is correct, because their "user friendly" router interface doesn't give me any option to do it myself.
3. Fiddled with 802.11n vs 802.11g settings on router. Had already disabled 802.11n on the Intel adapter via previous troubleshooting instructions, but since the router options were either g,n or b,g,n, this appears to be kind of a moot point.
Current options appear to be:
Ask for a modem/router combo upgrade from Comcast. (Long story, but they owe us at least that much.) Set that up and hope for the best. Not my preferred home networking paradigm, but it wasn't my choice to sign up with them in the first place, so I'm happy to make them do the legwork.
Pick up my own cable modem, use it with the wireless router I have stashed in a box somewhere, and hope for the best.
Update to Ubuntu 14.04 and hope for the best.
Any other suggestions? Any and all ideas welcome.
If you already have another wifi router, you may be able to disable the wifi radio on the modem/wifi device, plug your own wifi access point into a LAN port on the modem (LAN port to LAN port).
Set the access point to access point mode only, i.e. disable it's router functionality, DHCP etc... and let the modem do that.
Configure the WIFI on the access point as necessary.
After some very quick on-my-way-to-bed research on how to do that, it appears this model does not support shutting off the wifi locally and requires a customer service call to Comcast to switch over to bridge mode. But that's not any worse than calling to ask them for a new one (in fact, one user reported success on doing it over chat), so I might give it a shot tomorrow. Thanks.
At the risk of cursing myself by posting too soon, I seem to have fixed the problem by switching routers. Moral of the story: when in doubt, blame Comcast. Their favored Arris TC682 modem/router combo doesn't play well with the Intel AC 7260 wireless adapter. (For the record, I can't say for sure that the original tactic noted above didn't help, as that's all still in place, but it wasn't what finally made the difference in my case.)
I had never experienced it before today, having had a screen replacement to deal with another issue (which thankfully has been fixed). I'm guessing the antenna is in the lid? Why is it after changing the lid I am experiencing this for the first time? Bizarre.
Follow soeren's instructions (a few posts above) and disabling wifi power management (don't forget to set +x flag - as someone else advised) has fixed this issue for me.
I've had my XPS(Swedish version) a year now with a Intel 7260 wireless card on 12.02. A month ago, the wireless connection started to be unstable, weak signal. Very slow at connect. I found this thread and have tried the ideas the great people here come up with, but with no luck at all.I also upgraded to 14.04 but that did not help either. Anyone still having problem?
I too have been experiencing WiFi trouble (good throughput to start with followed by a persistently weak throughput of <1Mbps after several minutes) with my Sputnik 3 and Ubuntu 14.04. 12.04 worked fine. I tried several options including disabling power management and 11n (per Soeren above), upstream kernels etc, but nothing worked. On my holiday travels, I noticed I no longer suffered the throughput throttling and thought the problem may be a 7260 + router combo. I then found vladazhael's note! Finally, someone who shares my pain :). What worked for me was disabling 802.11b on the router (changing the mode to 802.11g only). I haven't had any throughput throttling issues for a few days now.
Edit: I wrote too soon. The problem was not fixed by the above. I hope Dell rolls out support for 14.04 soon!