It sure does. Whatever signal you have outside will be the same inside depending on size of space.
Installed my T-Mobile signal booster today and was pleasantly surprised with the results. We were getting 2 to 3 bars inside the house but had some dead areas and would drop calls especially if moving around. After installing the signal booster our phones have 5 bars inside. My data speeds are showing an average of 17 mbps which is close to what I had before but while the speed has not increased websites are most definitely loading quicker.
A suggestion I would make when doing the installation is to narrow down the part of your home that has the strongest signal with your cell phone and then plug the window unit into a long drop cord and move slowly around each room in that area searching for the strongest signal. The instructions say a window is usually the best place to get a good signal but while slowly searching the room with the window unit I found a "sweet spot" with 5 bars in the corner of the room about 5 feet above the floor.
At the windows and in the room, I could only get 3 bars and 12 inches above an below the spot I found in the corner I could only get 3 to 4 bars so it pays to take your time and search for the best signal.
I had doubts about how well the signal booster would work and had about made up my mind to invest in an expensive signal booster with a directional exterior antenna but I believe the T-Mobile unit is going to work fine for us. Can't complain about the price either