Feedback halves the dispersion for some two-user broadcast channels with common message

Kasper Fløe Trillingsgaard, Wei Yang, Giuseppe Durisi, Petar Popovski

Abstract: We investigate the maximum coding rate achievable on a two-user broadcast channel for the case where a common-message is transmitted using fixed-blocklength codes with feedback. Specifically, we focus on a family of broadcast channels composed of two antisymmetric Z-channels. For this setup, we obtain matching upper and lower bounds on the dispersion term in the asymptotic expansion of the maximum coding rate. These bounds reveal that the dispersion is halved compared to the no-feedback case.