On the Duality of Gaussian Multiple-Access and Broadcast Channels

Although T. Cover has been pointed out in [1] that one would have expected a duality between the broadcast channel(BC) and the multiple access channel (MAC), this problem is partially addressed in [2] untill recently. As the capacity region of general broadcast channel is still unknow, the duality between BC and MAC remains open. In [2], it shows that the Gaussian MAC and the Gaussian BC are essentially dual