Signal inconsistency

Hey guys got a question.

I have the NetGear WNDR4000 and in my HP G6 Laptop is a "Broadcom 4313GN 802.11b/g/n 1x1 Wi-Fi Adapter".

The router is on the main level of my house, and my laptop is in the basement, directly under my router. The problem is, my 30/mbs isnt consistent, it will drop down to 2 or 3 mb/s randomly, and go from full bars to 1 or 2 bars. Along with a lot of cutting out.

Is there any thing i can do or any way i can boost the signal strength?

Thanks