I read the original post now (in German, and as I am German, no problem). In his case I think "kismet" is a good start. So he can see, if there are other AP on the same frequency. I also suggest "wavemon", which shows all AP and its strenth.
If the neighbour is sending weired pckages (maybe with aireplay-ng, who knows), then wireshark or tshark is working fine for it. Also you have then evidence for his doings, which is illegal (here in Germany). Maybe also the package "horst" is also helpful, which is designed for excactly these issues: check your traffic. (I have never used it for now). Hope this helps Best regards Hans
