Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the Maximum Achievable Sum-rate of the RIS-aided MIMO Broadcast
  Channel   Reconfigurable intelligent surfaces (RISs) represent a new technology that
can shape the radio wave propagation and thus offers a great variety of
possible performance and implementation gains. Motivated by this, we
investigate the achievable sum-rate optimization in a broadcast channel (BC) in
the presence of RISs. We solve this problem by exploiting the well-known
duality between the Gaussian multiple-input multiple-output (MIMO) BC and the
multiple-access channel (MAC), and we correspondingly derive three algorithms
which optimize the users' covariance matrices and the RIS phase shifts in the
dual MAC. The users' covariance matrices are optimized by a dual decomposition
method with block coordinate maximization (BCM), or by a gradient-based method.
The RIS phase shifts are either optimized sequentially by using a closed-form
expression, or are computed in parallel by using a gradient-based method. We
present a computational complexity analysis for the proposed algorithms.
Simulation results show that the proposed algorithms converge to the same
achievable sum-rate, although the gradient-based optimization methods are
generally more time efficient. In addition, we demonstrate that the proposed
algorithms can provide a gain in the RIS-assisted BC assisted by multiple RISs
and that the gain depends on the placement of the RISs.

24
The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
16
The categories of this paper are: stat
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics