limited access/no internet connection home wifi Dell Precision M4700

I connect my laptop to router at home via wifi. But I got limited access or no internet connections messages quite often. Usually after diagnosing it will reconnect and works fine. However it won't work fine for long. 

The diagnostic looks like this

And the model of my laptop is Precision M4700. I bought this just last year, haven't really used it for a full year. Also, other devices on the home wifi including two laptops made by other manufacturers are fine with the connection. 

I have tried turning the modem on and off but did not help. The house is running on a Xfinity service. This problem suddenly happened sometime in November and did not recover since then. 

Thanks.