Please, excuse me my probably old, obsolete or stupid question.
But why we can’t make VirtualAP on wireless interface in Station mode or vice versa. Many times this feature could be useful in a(my) practice and many SOHO products have it as universal repeater. In OpenVRT you just add both AP and Client interfaces.
It isn’t impossible about 802.11 WiFi principles, but maybe it’s hard to make with regard to the ROS nStream and nv2 TDMA protocols?
You can!
Use the wireless-rep package and use the repeater mode. It will allow to make a client and an AP at the same time, on one physical interface.
http://wiki.mikrotik.com/wiki/Manual:Interface/Wireless#Repeater
Great! Now I see it’s a new stuff in 6.35. Already tried it and it works! 
Thak you normis, but I have a question and my example…
I have internet satellite and sometimes is down… rain, problems, etc etc.
For that moments, I want to use my cell phone 3g/4g like an AP, and I wnt my mikrotik 2011 to set like client for that network (cell phonme-mk) and continue using my actual Wireless network created in the RB2011…
Is not a repeater, is a Client with an IP (wireless) and a AP, with new ip, and all the firewall rules in the mk…
It isn’t just a repeater it’s full working parallel Client + AP mode. I think, MKT guys just called it so to make it clear for masses.
You can use the Repeater Setup tool, and then change they SSID’s and bridge/unbridge these interfaces arbitrary. Or you can just add VirtualAP interface (with it’s very own SSID, security profile, lan or address) upon physical Station mode wlan interface. And, just saw it, you can make it vice versa cause there is Virtual Client interface!
So update your RB to the 6.35 + repeater package and add a virtual client interface over the physical wlan, configure it as fallback gateway and you’re ready. All you have to do is to enable AP on the phone then bad weather going.
I have a similar internet backup config on my open-wrt. And now we can have it on our RBs which is nice. 
You can also do that, but you should make a new topic about this, since it is a completely different question
Ohhh I will update my RB751 for testing and I will try… Thank you.