Covertness Performance Analysis of STAR-RIS Assisted HARQ-RSMA Networks

In this work, we investigate a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) assisted hybrid automatic repeat request (HARQ)-rate-splitting multiple access (RSMA) network with an external detector Willie. The communication reliability and covertness are investigated by determining the connection outage probability (COP) of RSMA users and the detection error probability (DEP) of Willie. We also investigate the average number of transmission and the asymptotic expression of COPs. Meanwhile, we validate the accuracy of the analytical expression through simulation results, and the results show that: 1) As maximum transmission power (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$P_{B,max}$</tex-math></inline-formula>) increases, COPs decrease monotonically, while DEP decreases initially and then increases; 2) Increasing <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$P_{B,max}$</tex-math></inline-formula>, the number of STAR-RIS elements, and maximum number of transmissions (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$I$</tex-math></inline-formula>) will all enhance the reliability performance; 3) At <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$P_{B,max}=25$</tex-math></inline-formula> dB and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$I=5$</tex-math></inline-formula>, the COP of STAR-RIS assisted HARQ-RSMA network decreases by 55.09% compared to STAR-RIS-RSMA and 63.17% compared to HARQ-RSMA network.