Diversity Gain Region of Nakagami-m Faded Z-Channel

The interfering source in a two-user Z-channel can use either single-user (SU) codes or rate splitting (RS)-based multiuser codes. The RS codes are known to achieve better sum-rate than the SU codes. However, if the individual user's reliability requirements are considered in a two-user Z-channel, it is unknown whether the RS codes achieve better performance than SU codes. To this end, the diversity gain region (DGR), which characterizes the diversity order tradeoff between the two users, is characterized for the Nakagami-m faded Z-channel. The DGRs for the RS codes under different operating modes such as altruistic and selfish modes are derived. The RS codes can operate in the altruistic mode for a large range of multiplexing gains compared to that of the SU codes. On the other hand, in the selfish mode, the SU codes achieve better DGR than the RS codes. Moreover, orthogonalization is shown to perform better than SU and RS codes-based interference-limited Z-channel for an only limited multiplexing gain region.