My first thought is that it could be disconnecting because the power in this area is quite low and power just drops a little bit sometimes.(I'm guessing the solution for this could be an UPS on router)
And the other thing could be about configuration or the problem is in the ISP So here are some Netalyzer results
please tell me if you need some kind of other info that could be usefull
EDIT: when i scanned it again: i've got Network packet buffering may be excessive
Network buffer measurements (?): Uplink 650 ms, Downlink 120 ms –
We estimate your uplink as having 650 ms of buffering. This level can in some situations prove somewhat high, and you may experience degraded performance when performing interactive tasks such as web-surfing while simultaneously conducting large uploads. Real-time applications, such as games or audio chat, may also work poorly when conducting large uploads at the same time.