I use
one of these. It works wonders in my house most of the time.
The antenna for this unit is in my attic, and the repeater portion is in my basement. This gives me cell service in my basement office, home theater, etc.
The thing that people seem to forget is that if you don't have coverage outside, you won't get coverage inside, and they ding the product for that

At home, the outdoor signal is reasonably stable. However I've also tried this up in our cottage in ME where you can only get a signal if you stand in just the right place, in just the right position, and at just the right time. Up there, the signal drifts wildly...so the repeater likewise doesn't do much inside. You get a good connection, then watch it fall away.