Irregular STAR-RIS-Aided Wireless Systems with a Limited Number of
Passive Elements
Abstract
Simultaneous transmitting and reflecting reconfigurable intelligent
surfaces (STAR-RISs) have recently gained a great deal of attention due
to their ability of providing full-space service coverage. In this
paper, a novel concept called irregular STAR-RIS is proposed with a
small portion of activated transmitting and reflecting elements, where
users in opposite sides of the surface are served simultaneously. In
this proposed system, a tabu search-based sparse deployment and neighbor
extraction-based cross-entropy method for the beamforming optimization
of the proposed irregular STAR-RIS are considered. For the sake of fair
comparison and to highlight the achievable gains, the weighted sum-rate
(WSR) performance of a regular STAR-RIS-aided wireless system and a
traditional system without STAR-RIS is also evaluated. The results show
that the proposed irregular STAR-RIS with a small portion of active
elements is capable of significantly improving the WSR performance
compared to the conventional systems without STAR-RIS. It is also shown
that the position of the users has an impact on the WSR performance, and
that the near users have better performance than the far ones.