On the Symbol Error Rate and Diversity Gain Region of the Relay-Assisted Z-channel

Interference forwarding in a Z-channel makes interference stronger, which in turn enables usage of simple detectors like successive interference canceler (SIC) at interference-limited destination. In this work, the following protocols with SIC at the interference-limited destination are investigated: direct transmission (SICDirect), half-duplex decode-and-forward (SICDF), and half-duplex amplify-and-forward (SICAF) protocols. The achievable diversity orders of these protocols using M-PAM and M-QAM modulation are obtained. Moreover, minimum required exponential orders of the average received signal powers at the relay and interference-limited destination to restore full diversity are presented. The SICAFand SICDFprotocols are shown to achieve the same diversity order as that of the orthogonal transmission scheme while achieving better spectral efficiency than the orthogonal transmission. Closed-form expressions for the achievable diversity gain regions (DGRs) with the SICDirect, SICDF, and SICAFprotocols are derived. Selective decode-and-forward with SIC (SICSDF) is also considered. The multiplexing gain regions and the interference levels where the SICAFand SICSDFprotocols achieve better DGR than the SICDirectprotocol are obtained.