There is few reasons why are you getting poor signals which are listed below:
1.Cell tower distance
2. Internal interference (Electronic and magnetic waves may interfere with cell waves. )
3. High buildings around your home or tree maybe.
Solution for this problem can be:
If you are using Android,
Go to Settings>About Phone>Network>Signal Strength
Check Signal Strength which is in dB. If it is -50 then your signal strength is good, if it is -120 then your signal strength is bad.
Find a place in your home where you can get approx -s0 dB signal strength.