Proc. IEEE Int. Conf. on Communications Workshop on Reconfigurable Intelligent Surfaces for Future Wireless Communications,
Jun. 14-18, 2021, Montreal, Quebec, Canada.
Spectral Efficiency vs Complexity in Downlink Algorithms for Reconfigurable Intelligent Surfaces
Pooja Nuti and
Brian L. Evans
Department of Electrical and Computer Engineering,
Wireless Networking and Communications Group,
The University of Texas at Austin,
Austin, TX 78712 USA
Multiantenna Communications Project
Reconfigurable Intelligent Surfaces (RIS) are an emerging technology
that can be used to reconfigure the propagation environment to improve
cellular communication link rates.
RIS, which are thin metasurfaces composed of discrete elements, passively
manipulate incident electromagnetic waves through controlled reflective
In this paper, we investigate co-design of the multiantenna basestation
precoder and multielement RIS phase shifts.
The downlink narrowband transmission uses sub-6 GHz frequency bands, and
the user equipment is equipped with a single antenna.
Subject to the non-convex constraints due to the RIS phase shifts, we
maximize the spectral efficiency or its equivalent channel power proxy.
Our contributions in improving RIS-aided links include
- design of gradient ascent co-design algorithms,
- asymptotic (Big O) computational complexity analysis of proposed
and considered prior algorithms, and
- comparison of seven co-design algorithms in spectral efficiency vs.
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