wifi problem

i have an ipod 4th gen, i realize that the wifi kinda problem. it shows 3 full bar, but cant connect it to the internet. almost everytime i sleep my ipod then wake it back, it will have this problem (have 3 bars signal but cant connect to internet). to connect it to the internet, i need to off and then open back the wifi at settings. but, when i change the dns to 8.8.8.8 (a google dns if im not mistaken) the wifi problems is solved. just sometimes it will have this problem. is this my router problem or a software problem? even worse, is this some kind of hardware problem?

Since changing the DNS server address resolves the problem, it's probably not a hardware problem. Sounds like the iPod is just sluggish actually talking to your default DNS server. The requests can't be processed because your ipod doesn't know who Google is. By pointing it at a different DNS server, you're getting a faster response back from your DNS queries, so fewer internet issues.

not to mention that i font get the notifications of my facebook app, whoshere app when im not changing the dns although at that time, internet is working, after i changed the dns to 8.8.8.8, then the notifications will work. but using the 8.8.8.8 dns give me another problem, that is whenever i downloaded something from appstore, it will stuck and will not downloading at all, after i changed the dns back to original (by forgetting network and connect it back), then the app will downloading normally. but there is one time, when im going to the mall, and frequently connect with different wi-fi at the mall, when im back to home, without changing the dns, the internet works like charm. i try to reset network setting coz i think the problem is gone and i want to test it, and im wrong, the problems come again. sometime also, without changing the dns, the internet works like charm, but just for a limited time, after that, the problems will come again. even when i changed my dns to 8.8.8.8 there is still problem, there is 3 bars but cant connect to the internet but it is rarely occur. i googled about this, there are also other peoples have this kind of problem... man this is frustrated...