Always use N series compatiable devices such as routers, usb dongles etc... But with ps3 it does not support N wireless connectivity. Max it can handle is G so best solution is to use wired if you have crappy net speeds. ETHERNET cable I would recommend something like this:
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It's super thin.
If you have wireless only then simple tip that could help is install the unit away from electrical equipment that also generates interference. Avoid electric fans, other motors, and flourescent lighting. Any appliance that transmits in the same general range as 802.11b or 802.11g (2.4 GHz) can generate interference.