We are experiencing extremely poor internet performance on the wireless devices in our home.

Our internet connection is a TC cable-based Warpspeed connection which regularly reports almost nominal 100/10 speeds on a PC directly connected by a Gigabit port to our TPLink WDR3600 router.

However, performance on our wireless devices is extremely variable and volatile, ranging from increasingly rare periods with reasonable performance (around 15/3), to increasing periods with performance unusably slow.

It is possible that the problems are exacerbated by some TC network issues and there is a thread about that here: http://www.geekzone.co.nz/forums.asp?forumid=40&topicid=119353

However it also seems like wireless performance could be an issue. Bizarrely things 'seem' to have got worse since I replaced our old Linksys WRT54G router with the newer TPLink WDR3600.  While peak performance has improved (at times), overall performance is terrible.

The problem is that using simpl wifi monitoring and analysis tools I cannot see an obvious glaring cause for the performance problems.

Although it's a dual-band router we're effectively only using 2.4Ghz because of the range limitations on the 5GhZ band. As usual, we are surrounded by other 2.4GhZ networks. We are using channel 11 and have neighbours on channels 6, 9, and - more strongly - 1. We tend to see signal strengths of around -70 to -80 and sometimes up to -60 whereas the other networks are all -80 or worse.

Connection speed reported on my Samsung 9 laptop fluctuates wildly from 1.0 to 144.0 Mbps but most commonly around 50-65Mbps with about 3-4 or sometimes 5 bars. 

I suspect that very poor performance is closely associated with  virtually no speed upstream, probably leading to connection problems that affect downloads. This also seems to be correlated with failure to connect in speedtest and extremely long, variable, or no responses to pinging the router.

Another aggravating factor may be the presence in the house of a uTorrent user. I suspect that this contributes to saturating the uplink at times, exacerbating the overall problem, but is not the whole story as the same problem happens when the uTorrenter is off being a productive member of society.

I'd be grateful for any suggestions about what the problem might be, or even better, methods and tools to accurately identify the root cause.