iAd banner blank

Question

I'm trying to use simple iAd banner, but while checking in Simulator, I can see blank banner.

override func viewDidLoad() {
    super.viewDidLoad()
    self.saveJson()
    textField.delegate = self

    self.canDisplayBannerAds = true
    self.bannerAd?.delegate = self
    self.bannerAd?.hidden = true
}

func bannerViewDidLoadAd(banner: ADBannerView!) {
    self.bannerAd?.hidden = false
}

func bannerViewActionShouldBegin(banner: ADBannerView!, willLeaveApplication willLeave: Bool) -> Bool {
    return true
}

func bannerView(banner: ADBannerView!, didFailToReceiveAdWithError error: NSError!) {
    self.bannerAd?.hidden = false
}

Note: I also added iAd.framework into Build phases.

As you can see, iAd at the bottom is not displayed any content...