Connecting Problem in Wireless N ADSL2+ Modem Router TD-W8151N?

Hi,
It's been a long time since i am suffering this problem and a sure assistance to get it fixed is indeed. The problem that i am facing is that i am unable to use the wifi for just one device at a time means in the meanwhile when i try to connect my other laptop and other personal gadgets, the modem keeps restarting on the own, sometimes it gets connected and when my other device started operating it eventually shuts off again. But if i remove my DSL connection from my modem then all three of my devices gets connected without any prob.

What should i do Please help.