Gateway connectivity issues with gaming console

So I purchased a brand new Xbox thinking my console was simply old, and had connection issues. With my new Xbox the connection was fine at first, I was running 130 mps when downloading games and had zero lag spikes. I had even connected my Xbox to an xfi pod using an Ethernet chord and that seemed to had make the issue worse. Now with wireless connection my Xbox jumps from 30 to 50mps and I cannot play any game without lag spikes. My Xbox is also a floor directly below my gateway router (approximately 7ft). How can I solve this issue immediately please???