Secrecy Performance Analysis of RSMA-Based Communications Under Partial CSIT Against Randomly Located Eavesdroppers

In this letter, we investigate the physical layer security of rate-splitting multiple access (RSMA) scheme in the presence of randomly located non-colluding eavesdroppers. In this complicated case, the number, location, and channel state information (CSI) of eavesdroppers are unknown, posing a significant threat to the system. Moreover, we elaborate on practical scenarios where a multi-antenna base station serves multiple users under partial CSI at the transmitter (CSIT). Analytical expressions for the statistics of signal-to-interference plus noise ratios at both legitimate users and eavesdroppers are derived. Furthermore, we extract approximate theoretical expressions and the lower bound under worst-case eavesdroppers placement for the ergodic secrecy sum rate. Numerical results corroborate the accuracy of our derived analytical results, and indicate that our proposed RSMA scheme exhibits superior secrecy performance when dealing with randomly distributed eavesdroppers and partial CSIT, compared to other conventional multiple access schemes.