1,074 research outputs found
Double-Active-IRS Aided Wireless Communication: Deployment Optimization and Capacity Scaling
In this letter, we consider a double-active-intelligent reflecting surface
(IRS) aided wireless communication system, where two active IRSs are properly
deployed to assist the communication from a base station (BS) to multiple users
located in a given zone via the double-reflection links. Under the assumption
of fixed per-element amplification power for each active-IRS element, we
formulate a rate maximization problem subject to practical constraints on the
reflection design, elements allocation, and placement of active IRSs. To solve
this non-convex problem, we first obtain the optimal active-IRS reflections and
BS beamforming, based on which we then jointly optimize the active-IRS elements
allocation and placement by using the alternating optimization (AO) method.
Moreover, we show that given the fixed per-element amplification power, the
received signal-to-noise ratio (SNR) at the user increases asymptotically with
the square of the number of reflecting elements; while given the fixed number
of reflecting elements, the SNR does not increase with the per-element
amplification power when it is asymptotically large. Last, numerical results
are presented to validate the effectiveness of the proposed AO-based algorithm
and compare the rate performance of the considered double-active-IRS aided
wireless system with various benchmark systems
Extremal problems for disjoint graphs
For a simple graph , let and
be the set of graphs with the maximum number of edges and the set of graphs
with the maximum spectral radius in an -vertex graph without any copy of the
graph , respectively. Let be a graph with
. In this paper, we show that
for sufficiently large .
This generalizes a result of Wang, Kang and Xue [J. Comb. Theory, Ser. B,
159(2023) 20-41]. We also determine the extremal graphs of in term of the
extremal graphs of .Comment: 23 pages. arXiv admin note: text overlap with arXiv:2306.1674
Spectral extremal graphs for edge blow-up of star forests
The edge blow-up of a graph , denoted by , is obtained by
replacing each edge of with a clique of order , where the new vertices
of the cliques are all distinct. Yuan [J. Comb. Theory, Ser. B, 152 (2022)
379-398] determined the range of the Tur\'{a}n numbers for edge blow-up of all
bipartite graphs and the exact Tur\'{a}n numbers for edge blow-up of all
non-bipartite graphs. In this paper we prove that the graphs with the maximum
spectral radius in an -vertex graph without any copy of edge blow-up of star
forests are the extremal graphs for edge blow-up of star forests when is
sufficiently large.Comment: 22. arXiv admin note: text overlap with arXiv:2208.0655
Beyond OOD State Actions: Supported Cross-Domain Offline Reinforcement Learning
Offline reinforcement learning (RL) aims to learn a policy using only
pre-collected and fixed data. Although avoiding the time-consuming online
interactions in RL, it poses challenges for out-of-distribution (OOD) state
actions and often suffers from data inefficiency for training. Despite many
efforts being devoted to addressing OOD state actions, the latter (data
inefficiency) receives little attention in offline RL. To address this, this
paper proposes the cross-domain offline RL, which assumes offline data
incorporate additional source-domain data from varying transition dynamics
(environments), and expects it to contribute to the offline data efficiency. To
do so, we identify a new challenge of OOD transition dynamics, beyond the
common OOD state actions issue, when utilizing cross-domain offline data. Then,
we propose our method BOSA, which employs two support-constrained objectives to
address the above OOD issues. Through extensive experiments in the cross-domain
offline RL setting, we demonstrate BOSA can greatly improve offline data
efficiency: using only 10\% of the target data, BOSA could achieve {74.4\%} of
the SOTA offline RL performance that uses 100\% of the target data.
Additionally, we also show BOSA can be effortlessly plugged into model-based
offline RL and noising data augmentation techniques (used for generating
source-domain data), which naturally avoids the potential dynamics mismatch
between target-domain data and newly generated source-domain data
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