I found it fairly easy to run a 50 ft ethernet cable to my tv from the router. I have a wireless n router but connection to tv is not reliable which I find odd since my laptop works fine in the same room. If ethernet not an option for you the range extender would be your best bet.
I have the same problem. Samsung tell me the wifi on the tv is only good for about 15' so they recommend a signal booster. Can anyone recommend one they are using presently with a Smart TV, Tv is about 50' away from gateway