No wi-fi in one room of my house?

So, I recently got my sister's old iPhone 4s, since she upgraded to the 5s. The wi-fi usually works fine, but it never works in my bedroom.

My laptop, my sister's laptop, the iPad, iPod, and all the other iPhones have wi-fi in this room, but it's just my iPhone that doesn't get wi-fi.

Does anyone know how I can get wi-fi in here? Everyone else gets wi-fi in this bedroom, just not me.

Raise the height of the router. Experiment with a horizontal vs, vertical placement and move the antennas.
Take your sister's laptop into your room and use the strength meter to see how moving the router affects the signal. If you can get 2 bars, the iphone should work.

If the Wi-Fi works with the phone everywhere else in the house, then the issue is that the signal going to your room is not strong enough. As different devices have different Wi-Fi receivers with different antennas in them, one device can work in your room while another can fail.

The solution is to increase the signal to your room. The easiest way to do that is to move the Wi-Fi router to a location that is closer to your room. Something a move of even 5 feet can make a big difference.

Have you tried disconencting from the Wi-Fi and reconnecting?

You need to update your phone.