On the cooperative red alert exponent for the AWGN-MAC with feedback

We consider communication over the additive white Gaussian noise multiple-access channel with feedback, an average power and a peak energy constraint within an unequal error protection scenario. We would like to design a codebook with a special red alert message that has an extremely small error probability while we keep other error events unlikely. We design this codebook using an offset construction: a fraction of available power is used to implement Ozarow´s capacity-achieving scheme while the rest of the power is allocated to increase the reliability of the red alert codeword.