Keywords :
Symbol level precoding, reconfigurable intelligent surface, energy efficiency, finite block length, constellation rotation, short packets.
Abstract :
[en] In this paper, we tackle the problem of joint symbol
level precoding (SLP) and reconfigurable intelligent surface (RIS)
phase shift design with constellation rotation in the finite block
length regime. We aim to increase energy efficiency by minimizing
the total transmit power while satisfying the quality of service
constraints. The total power consumption can be significantly
minimized through the exploitation of multiuser interference
by symbol level precoding and by the intelligent manipulation
of the propagation environment using reconfigurable intelligent
surfaces. In addition, the constellation rotation per user contributes to energy efficiency by aligning the symbol phases of the
users, thus improving the utilization of constructive interference.
The formulated power minimization problem is non-convex and
correspondingly difficult to solve directly. Hence, we employ an
alternating optimization algorithm to tackle the joint optimization of SLP and RIS phase shift design. The optimal phase of
each user’s constellation rotation is obtained via an exhaustive
search algorithm. Through Monte-Carlo simulation results, we
demonstrate that the proposed solution yields substantial power
minimization as compared to conventional SLP, zero forcing
precoding with RIS as well as the benchmark schemes without
RIS.
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