Jiaqi Li, Guangming Wang, Shuntian Zheng, Minzhe Ni, Xiaoman Lu, Guanghui Ye, Yu Guan. Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers). 2026.

Massive multiple-input and multiple-output (MIMO) systems with orthogonal frequency division multiplexing (OFDM) are foundational for downlink multiuser (MU) systems in future wireless networks, for their ability to enhance spectral efficiency and support a large number of users. However, high user density intensifies severe inter-user interference (IUI) and pilot overhead. Consequently, existing blind and semi-blind channel estimation (CE) and signal detection (SD) algorithms suffer performance degradation and increased complexity, and are further challenged by frequency-selective channels with high-order modulation demands. To this end, this paper proposes a novel semi-blind joint channel estimation and signal detection (JCESD) method. Specifically, the proposed approach employs a hybrid precoding architecture to suppress IUI. Furthermore, we formulate JCESD as a non-convex optimization exploiting constellation affine invariance. A few pilots are used to achieve coarse estimation for initialization and ambiguity resolution. For high-order modulations, a data augmentation mechanism utilizes the symmetry of quadrature amplitude modulation (QAM) constellations to increase the effective number of samples. To address frequency-selective channels, CE accuracy is then enhanced via an iterative refinement strategy that leverages improved SD results. Simulation results demonstrate an average throughput gain of 11% over pilot-based methods in MU scenarios, highlighting its potential for improving spectral efficiency.

Orthogonal time frequency space (OTFS) waveform has emerged as a promising technology for low-earth orbit satellite (LEO) communications owing to its capacity in mitigating Doppler effects. However, the OTFS modulation in LEO communications with massive multiple-input multiple-output (MIMO) techniques suffer from enormous training overhead due to the large number of satellite antennas. In this paper, we propose a hybrid model-data driven channel estimation scheme for massive MIMO-OTFS LEO satellite communications. We first derive the input-output relationship for massive MIMO-OTFS and formulate the channel estimation as a sparse signal recovery problem. Subsequently, we unroll the orthogonal approximate message passing (OAMP) algorithm into a model-driven deep unrolled network (DUN) to recover the sparse channel. On this basis, we design a side information and attention-enhanced OAMP network (SA-OAMPNet), which incorporates a data-driven self-attention mechanism into each iteration of unrolled OAMP network to further exploit the sparsity across the delay-Doppler-angle domain. Simulation results demonstrate that the proposed DUNs outperform conventional algorithms and deep learning methods. Remarkably, the proposed SA-OAMPNet reduces pilot overhead by about 30% without significant degradation in channel estimation accuracy.

The adage "Beautiful Outside But Ugly Inside" resonates with the security and explainability challenges encountered in image aesthetics assessment (IAA). Although deep neural networks (DNNs) have demonstrated remarkable performance in various IAA tasks, how to probe, explain, and enhance aesthetics-oriented "black-box" models has not yet been investigated to our knowledge. This lack of investigation has significantly impeded the commercial application of IAA. In this paper, we investigate the susceptibility of current IAA models to adversarial attacks and aim to elucidate the underlying mechanisms that contribute to their vulnerabilities. To address this, we propose a novel diffusion-based framework as an attacker (DA3Attacker), capable of generating adversarial examples (AEs) to deceive diverse black-box IAA models. DA3Attacker employs a dedicated Attack Diffusion Transformer, equipped with modular aesthetics-oriented filters. By undergoing two unsupervised training stages, it constructs a latent space to generate AEs and facilitates two distinct yet controllable attack modes: restricted and unrestricted. Extensive experiments on 26 baseline models demonstrate that our method effectively explores the vulnerabilities of these IAA models, while also providing multi-attribute explanations for their feature dependencies. To facilitate further research, we contribute the evaluation tools and four metrics for measuring adversarial robustness, as well as a dataset of 60,000 re-labeled AEs for fine-tuning IAA models. The resources are available here.

The past decade has witnessed an increasing demand for enhancing image quality through exposure, and as a crucial prerequisite in this endeavor, Image Exposure Assessment (IEA) is now being accorded serious attention. However, IEA encounters two persistent challenges that remain unresolved over the long term: the accuracy and generalizability of No-reference IEA are inadequate for practical applications; the scope of IEA is confined to qualitative and quantitative analysis of the entire image or subimage, such as providing only a score to evaluate the exposure level, thereby lacking intuitive and precise fine-grained evaluation for complex exposure conditions. The objective of this paper is to address the persistent bottleneck challenges from three perspectives: model, dataset, and benchmark. 1) Model-level: we propose a Pixel-level IEA Network (P-IEANet) that utilizes Haar discrete wavelet transform (DWT) to analyze, decompose, and assess exposure from both lightness and structural perspectives, capable of generating pixel-level assessment results under no-reference scenarios. 2) Dataset-level: we elaborately build an exposure-oriented dataset, IEA40K, containing 40K images, covering 17 typical lighting scenarios, 27 devices, and 50+ scenes, with each image densely annotated by more than 10 experts with pixel-level labels. 3) Benchmark-level: we develop a comprehensive benchmark of 19 methods based on IEA40K. Our P-IEANet not only achieves state-of-the-art (SOTA) performance on all metrics but also seamlessly integrates with existing exposure correction and lighting enhancement methods. To our knowledge, this is the first work that explicitly emphasizes assessing complex image exposure problems at a pixel level, providing a significant boost to the IEA and exposure-related community. The code and dataset are available in \href{https://github.com/mRobotit/Pixel-level-No-reference-Image-Exposure-Assessment}{\textcolor{red} {here}}.

We consider the uplink connectivity for massive machine-type communications (mMTC) assisted by intelligent reconfigurable surfaces (IRSs), where device activity detection (DAD) and channel estimation (CE) are challenging due to limited pilot sequences. Moreover, differentiation among device types causes channels to deviate from the assumed characteristics, leading to performance degradation of conventional compressive sensing (CS) algorithms. To this end, two innovative networks driven by the hybrid of model and data are proposed exploiting the iterative frameworks and deep neural networks. We first present a hybrid driven iterative shrinkage thresholding algorithm, dubbed HISTA-Net, where a dual attention network (DAN) is embedded within the iterations to adaptively suppress iterative noise and enhance sparsity properties. Subsequently, we encapsulate data driven network and the intrinsic channel matrix knowledge, and derive a hybrid driven approximate message passing network (HAMP-Net) to further improve the sparse recovery performance. Our experiments demonstrate that the proposed networks outperform existing CS methodologies and deep learning strategies in accuracy, convergence, and generalization ability. Remarkably, the proposed HAMP-Net reduces pilot overhead by 30%, and achieves an NMSE gain of 3 dB for signal-to-noise ratios exceeding 15 dB.

Intelligent reflecting surfaces (IRS) have been proposed in millimeter wave (mmWave) and terahertz (THz) systems to achieve both coverage and capacity enhancement, where the design of hybrid precoders, combiners, and the IRS typically relies on channel state information. In this paper, we address the problem of uplink wideband channel estimation for IRS aided multiuser multiple-input single-output (MISO) systems with hybrid architectures. Combining the structure of model driven and data driven deep learning approaches, a hybrid driven learning architecture is devised for joint estimation and learning the properties of the channels. For a passive IRS aided system, we propose a residual learned approximate message passing as a model driven network. A denoising and attention network in the data driven network is used to jointly learn spatial and frequency features. Furthermore, we design a flexible hybrid driven network in a hybrid passive and active IRS aided system. Specifically, the depthwise separable convolution is applied to the data driven network, leading to less network complexity and fewer parameters at the IRS side. Numerical results indicate that in both systems, the proposed hybrid driven channel estimation methods significantly outperform existing deep learning-based schemes and effectively reduce the pilot overhead by about 60% in IRS aided systems.

We present a comprehensive study on a new task named image color aesthetics assessment (ICAA), which aims to assess color aesthetics based on human perception. ICAA is important for various applications such as imaging measurement and image analysis. However, due to the highly diverse aesthetic preferences and numerous color combinations, ICAA presents more challenges than conventional image quality assessment tasks. To advance ICAA research, 1) we propose a baseline model called the Delegate Transformer, which not only deploys deformable transformers to adaptively allocate interest points, but also learns human color space segmentation behavior by the dedicated module. 2) We elaborately build a color-oriented dataset, ICAA17K, containing 17K images, covering 30 popular color combinations, 80 devices and 50 scenes, with each image densely annotated by more than 1,500 people. Moreover, we develop a large-scale benchmark of 15 methods, the most comprehensive one thus far based on two datasets, SPAQ and ICAA17K. Our work, not only achieves state-of-the-art performance, but more importantly offers the community a roadmap to explore solutions for ICAA. Code and dataset are available in here.

Transformers have shown great potential in various vision tasks, but none of them have surpassed the best CNN model on image aesthetics assessment (IAA) tasks. IAA is a challenging task in multimedia systems that requires attention to both foreground and background, as well as robustness to noisy and redundant labels. The global and dense attention mechanism of Transformers, designed for saliency-oriented tasks, may miss important aesthetic information in the background, increase the computational cost and slow down the convergence on IAA tasks. To address these issues, we propose an Enhancer for Aesthetics-Oriented Transformers (EAT). EAT uses a deformable, sparse and data-dependent attention mechanism that learns where to focus and how to refine attention by offsets. EAT also guides the offsets to balance the attention between foreground and background according to dedicated rules. Our EAT-enhanced Transformers outperform the previous methods on four representative datasets with fewer training epochs. Code is available in https://github.com/woshidandan/Image-Aesthetics-Assessment