Reconfigurable Intelligent Surfaces-Enabled Intra-Cell Pilot Reuse in Massive MIMO Systems
CoRR(2023)
摘要
Channel state information (CSI) estimation is a critical issue in the design
of modern massive multiple-input multiple-output (mMIMO) networks. With the
increasing number of users, assigning orthogonal pilots to everyone incurs a
large overhead that strongly penalizes the system's spectral efficiency (SE).
It becomes thus necessary to reuse pilots, giving rise to pilot contamination,
a vital performance bottleneck of mMIMO networks. Reusing pilots among the
users of the same cell is a desirable operation condition from the perspective
of reducing training overheads; however, the intra-cell pilot contamination
might worsen due to the users' proximity. Reconfigurable intelligent surfaces
(RISs), capable of smartly controlling the wireless channel, can be leveraged
for intra-cell pilot reuse. In this paper, our main contribution is a RIS-aided
approach for intra-cell pilot reuse and the corresponding channel estimation
method. Relying upon the knowledge of only statistical CSI, we optimize the RIS
phase shifts based on a manifold optimization framework and the RIS positioning
based on a deterministic approach. The extensive numerical results highlight
the remarkable performance improvements the proposed scheme achieves (for both
uplink and downlink transmissions) compared to other alternatives.
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关键词
Reconfigurable Intelligent Surfaces (RIS),6G,multi-user MIMO,pilot-reuse,manifold optimization
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