navigator.online can't detect 3G network in blackberry html5 app

Question

I am new to blackberry development. I am creating a html5 app for blackberry.

I need to check the internet connection in every page.So i did this as below in every page.

In javascript

 var a=navigator.online

  if(a)
  {
     // nothing
  }
  else
  {
     alert("check for internet connection");
  }

It is working in Blackberry OS 6 & 7 properly.

But when the mobile is having blackberry OS5 it is showing the else statement.(which should not happen ideally)

Please help me out regarding this.

Thanks