  Reconfigurable intelligent surface (RIS) has been recognized as a promising
technique for the sixth generation (6G) of mobile communication networks. The
key feature of RIS is to reconfigure the propagation environment via smart
signal reflections. In addition, active RIS schemes have been recently proposed
to overcome the deep path loss attenuation inherent in the RIS-aided
communication systems. Accordingly, this paper considers the secrecy
performance of up-link RIS-aided multiple users multiple-input single-output
(MU-MISO) communication systems, in the presence of multiple passive
eavesdroppers. In contrast to the existing works, we investigate the impact of
the RIS phase shift errors on the secrecy performance. Taking into account the
complex environment, where a general Rician channel model is adopted for all
the communication links, closed-form approximate expressions for the ergodic
secrecy rate are derived for three RIS configurations, namely, i) passive RIS,
ii) active RIS, iii) active RIS with energy harvesting (EH RIS). Then, based on
the derived expressions, we optimize the phase shifts at the RIS to enhance the
system performance. In addition, the best RIS configuration selection is
considered for a given target secrecy rate and amount of the power available at
the users. Finally, Monte-Carlo simulations are provided to verify the accuracy
of the analysis, and the impact of different system parameters on the secrecy
performance is investigated. The results in this paper show that, an active RIS
scheme can be implemented to enhance the secrecy performance of RIS-aided
communication systems with phase shift errors, especially when the users have
limited transmission power.
