Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: IRS-Enhanced OFDMA: Joint Resource Allocation and Passive Beamforming
  Optimization   Intelligent reflecting surface (IRS) is an emerging technique to enhance the
wireless communication spectral efficiency with low hardware and energy cost.
In this letter, we consider the integration of IRS to an orthogonal frequency
division multiple access (OFDMA) based multiuser downlink communication system,
and study the pertinent joint optimization of the IRS reflection coefficients
and OFDMA time-frequency resource block as well as power allocations to
maximize the users' common (minimum) rate. Specifically, due to the lack of
frequency-selective passive beamforming capability at the IRS, only one set of
reflection coefficients can be designed for adapting to a large number of
channels of multiple users over different frequency sub-bands. To tackle this
difficulty, we propose a novel dynamic passive beamforming scheme where the IRS
reflection coefficients are dynamically adjusted over different time slots
within each channel coherence block to create artificial time-varying channels
and select only a subset of the users to be simultaneously served in each time
slot, thus achieving a higher passive beamforming gain. Although the formulated
optimization problem is non-convex, we propose an efficient algorithm to obtain
a suboptimal solution to it. Numerical results show that the proposed scheme
significantly improves the system common rate over the setup without IRS and
that with random IRS reflection coefficients. Moreover, our proposed dynamic
passive beamforming outperforms the fixed passive beamforming which employs a
common set of reflection coefficients in each channel coherence block, by more
flexibly balancing between passive beamforming and multiuser diversity gains.

31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
21
The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
15
The categories of this paper are: nucl-ex
37
The categories of this paper are: supr-con
24
The categories of this paper are: dg-ga