  We consider the problem of communication over a two-user Additive White
Gaussian Noise Broadcast Channel (AWGN-BC) with an AWGN Multiple Access (MAC)
active feedback. We describe a constructive reduction from this setup to the
well-studied setup of linear-feedback coding over the AWGN-BC with noiseless
feedback (and different parameters). This reduction facilitates the design of
linear-feedback coding schemes in the (passive) noiseless feedback regime,
which can then be easily and constructively transformed into coding schemes in
the MAC feedback regime that attain the exact same rates. Our construction
introduces an element of interaction into the coding protocol, and is based on
modulo-lattice operations. As an example, we apply our method to the
Ozarow-Leung scheme, and demonstrate how MAC feedback can be used to increase
the capacity region of the AWGN-BC.
