MIMO Channel Shaping and Rate Maximization Using Beyond Diagonal RIS
This paper investigates the limits to which a passive Reconfigurable Intelligent Surface (RIS) can reshape a point-to-point Multiple-Input Multiple-Output (MIMO) in terms of singular values for improved wireless (e.g., rate and power) performance. We depart from the Diagonal (D) scattering matrix and adopt a Beyond Diagonal (BD) model that exploits element-wise connections for signal amplitude and phase manipulation. Specifically, analytical bounds are derived under popular RIS deployment scenarios to showcase the shaping potentials of BD-RIS on the channel Degrees of Freedom (DoF), singular value spread, power gain, and capacity. A numerical optimization method is then proposed for a broader range of shaping problems and invoked to characterize the achievable singular value region. As a side product, we tackle BD-RIS-aided MIMO rate maximization problem by a local-optimal Alternating Optimization (AO) and a low-complexity shaping-inspired approach. Results show that BD-RIS significantly improves the dynamic range of all channel singular values and the trade-off in manipulating them, resulting in enhanced power gain and achievable rate. Those benefits become more pronounced when the number of RIS elements or MIMO dimensions increase. Of particular interest, BD-RIS is shown to activate multi-stream transmission (hence achieving the asymptotic DoF) at much lower transmit power than D-RIS thanks to its singular value shaping proficiency.
Code (1)
Similar Papers 제목 키워드 기반
Capacity Maximization for MIMO Channels Assisted by Beyond-Diagonal RIS
Reconfigurable intelligent surfaces (RISs) can improve the capacity of wireless communication links by passively beamforming the impinging signals in desired directions. This feature has been demonstrated both analytical…
Beyond Traditional Beamforming: Singular Vector Projection for MU-MIMO
This letter introduces a low-complexity beamforming approach for MU-MIMO systems with multiple data streams per user, minimizing inter-user interference and improving spectral efficiency (SE). The Interference-Optimized …
Computational EfficiencyManagementBlind Data Detection in Massive MIMO via $\ell_3$-norm Maximization over the Stiefel Manifold
Massive MIMO has been regarded as a key enabling technique for 5G and beyond networks. Nevertheless, its performance is limited by the large overhead needed to obtain the high-dimensional channel information. To reduce t…
User Coordination for Fast Beam Training in FDD Multi-User Massive MIMO
Massive multiple-input multiple-output (mMIMO) communications are one of the enabling technologies of 5G and beyond networks. While prior work indicates that mMIMO networks employing time division duplexing have a signif…
Transmit and Receive Antenna Port Selection for Channel Capacity Maximization in Fluid-MIMO Systems
In this letter, we study a discrete optimization problem, namely, the maximization of channel capacity in fluid multiple-input multiple-output (fluid-MIMO) systems through the selection of antenna ports/positions at both…