"Why not use a Wifi signal booster ? Unless your walls are made of kryptonite, they should help !"
Maybe, but I always think that just increasing the signal is (a) Not necessarily going to help (you don't know, until you've forked out the money), and (b) a bit like putting the Hi-Fi on full volume so that you can hear it all round the house, when extension speakers would be more discreet. :-)