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Hi,

I could not see any AP using Control Wrapper frame. And also I could not see any application of this frame. Can you please provide some info on this.

Thanks in advance for your time.

A Control Wrapper frame is just a normal control frame with an HT Control field.  If you look at the format of the HT Control field, you can see applications for the Control Wrapper frame.  If a system is capable of advanced HT features (like beamforming), this allows control frames to leverage those features.

--@@ron

Thanks Aaron,,, now I can see the application of these frames. Still I have few more questions for you.

There are some other frames which ll be used for beamforming and also for other applications I believe there will dedicated frames to carry out their function. Why are we wrapping it with another frame? This will make the frame much bigger in length. Will it be used for some kind of protection mechanism??

Also is there any AP which is using it? I googled it and did not get answers ;)

You can read a few more details from a true 802.11 guru (Devin Akin) here:

http://www.cwnp.com/cwnp_wifi_blog/the-802-11-frame-format-new-and-improved/

Some fields are copied from the carried control frame into the control wrapper frame, others are omitted from the carried control frame.  Yes, this adds overhead, just as any HT frame has more overhead.  But there should be an overall performance increase because of the added ability to leverage HT features.
Here is some info from one company that uses TX beamforming:
http://www.ruckuswireless.com/technology/beamflex

...and another article describing why this is kinda cool, but not a silver bullet:
http://www.theruckusroom.net/2012/05/transmit-beamforming-comes-with-a-big-but.html

Again, these wrapper frames can be used to leverage any of the advanced HT features described in an HT control frame.  As far as implementation, I bet it's relatively rare.  You'll find that there are many 802.11 standards that are not widely implemented.  Hope this helps!
--@@ron

Aaron, the link on TxBF was very useful. Thank you!