Maximizing Spectral and Energy Efficiency in Multi-user MIMO OFDM Systems with RIS and Hardware Impairment
CoRR(2024)
摘要
An emerging technology to enhance the spectral efficiency (SE) and energy
efficiency (EE) of wireless communication systems is reconfigurable intelligent
surface (RIS), which is shown to be very powerful in single-carrier systems.
However, in multi-user orthogonal frequency division multiplexing (OFDM)
systems, RIS may not be as promising as in single-carrier systems since an
independent optimization of RIS elements at each sub-carrier is impossible in
multi-carrier systems. Thus, this paper investigates the performance of various
RIS technologies like regular (reflective and passive), simultaneously transmit
and reflect (STAR), and multi-sector beyond diagonal (BD) RIS in multi-user
multiple-input multiple-output (MIMO) OFDM broadcast channels (BC). This
requires to formulate and solve a joint MIMO precoding and RIS optimization
problem. The obtained solution reveals that RIS can significantly improve the
system performance even when the number of RIS elements is relatively low.
Moreover, we develop resource allocation schemes for STAR-RIS and multi-sector
BD-RIS in MIMO OFDM BCs, and show that these RIS technologies can outperform a
regular RIS, especially when the regular RIS cannot assist the communications
for all the users.
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