5,515 papers
Partially deterministic sampling for compressed sensing with denoising guarantees
We study compressed sensing when the sampling vectors are chosen from the rows of a unitary matrix. In the literature, these sampling vectors are typically chosen randomly; the use of randomness has enabled major empirical and theoretical advances in the field. However, in practice there are often certain crucial sampling vectors, in which case practitioners will depart from the theory and sample such rows deterministically. In this work, we derive an optimized sampling scheme for Bernoulli selectors which naturally combines random and deterministic selection of rows, thus rigorously deciding which rows should be sampled deterministically. This sampling scheme provides measurable improvements in image compressed sensing for both generative and sparse priors when compared to with-replacement and without-replacement sampling schemes, as we show with theoretical results and numerical experiments. Additionally, our theoretical guarantees feature improved sample complexity bounds compared to previous works, and novel denoising guarantees in this setting.
2604.04802Apr 2026
View
LRC codes over characteristic $2$
In this work the construction of LRC codes given in [6] is completed, in the case of even characteristic. A general construction is presented, that enables us to obtain linear LRC codes of large length $n \approx q^4$, dimension and distance of order $q^4$, and locality $r =q-1$. In addition, the cases $q = 4$ and $q=8$ are studied.
2604.04678Apr 2026
View
2604.04674Identification for Colored Gaussian Channels
We study the identification capacity of discrete-time Gaussian channels impaired by correlated noise and inter-symbol interference (ISI). Our analysis is formulated for deterministic encoding functions subject to a peak power constraint and colored noise whose covariance matrix features a polynomially bounded singular value spectrum, i.e., $\sim [n^{-μ} , n^{μ/2}]$ where $n$ is the codeword length and $μ\in [0,1/2)$ is the spectrum rate. A central result establishes that, even when the ISI memory length grows sub-linearly with $n,$ i.e., $\sim n^κ$ where $κ\in [0,1/2)$ and $κ+ μ\in [0,1/2),$ the codebook size continues to exhibit super-exponential growth in $n$, i.e., $\sim 2^{(n \log n)R},$ with $R$ representing the associated coding rate. Moreover, by employing the well-known Mahalanobis-distance decoder induced by colored Gaussian noise statistics, we characterize bounds on the identification capacity, with the resulting bounds parameterized by $κ$ and $μ.$
2604.04674Apr 2026
View
Pinching Antenna Systems (PASS): Enabling Reconfigurable and Controllable Wireless Channels -- A Comprehensive Survey
The evolution of wireless networks is driving new paradigms for consideration in upcoming generations. To this end, the 6G anticipates the development of several data-rate-hungry applications, in addition to a forecast growth in sensing-centric applications. Such an evolution, however, is unbalanced on the other side by the accentuated scarcity of spectrum, which opens up urgent needs to develop spectrum-efficient communication and sensing techniques. Due to the inability of the traditional multi-antenna schemes to enhance a wireless channel quality, increasing interest has been paid to wireless channel-altering schemes, such as reconfigurable intelligent surfaces and movable antennas. Recently, a new technique in this category, called pinching antennas (PAs), was introduced and tested. PA systems (PASS) are based on extending the reach of a base station by connecting its radio-frequency chains to long waveguides, on which one or many radiating antennas are pinched at custom positions of interest. Thus, such a technique can provide a means of overcoming several unfavorable channel conditions, such as the absence of a line-of-sight and increased free-space path loss. Importantly, such a channel-tuning feature can provide notable enhancements in terms of sensing, network coverage, data rate, and resilience against eavesdropping. In this work, we provide a comprehensive review of research on PASS, designed to meet various system design objectives, such as network coverage and data rate, information-theoretically secure transmission, sensing, integrated sensing and communication, and energy efficiency. A categorization of the surveyed work is established by comparing the various PASS schemes presented. Several takeaways are illustrated on the proposed schemes' potential and limitations, along with several directions forward discussed, in terms of future deployment and implementation.
2604.04521Apr 2026
View2604.04519Linear Exact Repair in MDS Array Codes: A General Lower Bound and Its Attainability
For an $(n,k,\ell)$ MDS array code over $\mathbb{F}_q$, how small can the repair bandwidth and repair I/O be under linear exact repair? We study this question in the regime where the field size $q$, the redundancy $r=n-k$, and the sub-packetization level $\ell$ are fixed, while the code length $n$ varies, and we develop a geometric approach to this setting. Our starting point is an intrinsic reformulation of linear exact repair for MDS array codes in terms of subspace intersections and, for repair I/O, the projective point configurations induced by a parity-check realization. This viewpoint yields a simple projective counting argument establishing the general lower bound $$β_{\mathrm{avg}},β_{\max},γ_{\mathrm{avg}},γ_{\max}\;\ge\;\ell(n-1)-\frac{q^{(r-1)\ell}-1}{q-1}$$ for linear exact repair of every $(n,k,\ell)$ MDS array code over $\mathbb{F}_q$ with redundancy $r=n-k\ge 2$. To our knowledge, this is the first lower bound of this form that applies to arbitrary redundancy $r\ge 2$ and sub-packetization level $\ell$. At first glance, the projective counting bound appears rather coarse and therefore unlikely to be attained. We prove that this intuition is correct whenever $r\ge 3$ and $\ell\ge 2$. For $r=2$, the picture changes completely. Using Desarguesian spreads from finite geometry, we construct MDS array codes that attain the bound over a broad interval of code lengths, up to the maximum possible length $q^{\ell}+1$, and do so simultaneously for both repair bandwidth and repair I/O. In the smallest nontrivial case $(r,\ell)=(2,2)$, we also prove a converse within the regular-spread model. Together, these results identify a uniform obstruction governing linear exact repair and show that, in the two-parity case, this obstruction is tight.
2604.04519Apr 2026
View
Beyond-Diagonal RIS For Enhanced Secrecy and Sensing Gains in Secure ISAC Networks: An Optimization Framework
Integrated sensing and communication (ISAC) has been receiving a notable interest as an energy- and spectrum-efficient enabler for simultaneous communication and sensing. Notably, reconfigurable intelligent surfaces (RIS) is among the key technologies enabling robust communication and sensing, particularly in environments without a line-of-sight (LoS). Recently, a new type of RIS, called beyond-diagonal RIS (BD-RIS), has drawn attention, offering additional degrees of freedom in controlling the propagation medium. In this paper, a novel secure BD-RIS-aided ISAC scheme is proposed and evaluated. The scheme is applicable to a multi-user multi-target ISAC network, where a dual-functional radar-communication (DFRC) base station (BS) simultaneously serves multiple downlink users and senses various targets that aim to eavesdrop on the legitimate signal transmitted to the users. The presence of a BD-RIS enables circumventing the absence of the LoS link and ensures secure transmission and sensing. To this end, an optimization problem is formulated aiming at maximizing a weighted sum of per-target reflected powers, subject to secrecy and transmit power constraints. Thus, by virtue of an alternating optimization (AO)- and Riemannian conjugate gradient-based approach, local optima for the BD-RIS scattering matrix, transmit signal beamforming matrices, and artificial noise covariance matrix are obtained. Numerical results highlight (i) the notable sensing gains of the BD-RIS-aided design with respect to its diagonal RIS (D-RIS)-based baseline and (ii) the improved secrecy-sensing trade-off, whereby the BD-RIS can ensure an increasing system secrecy without degrading the per-target reflected power.
2604.04480Apr 2026
View
Out-of-Air Computation: Enabling Structured Extraction from Wireless Superposition
Over-the-air computation (AirComp) has traditionally been built on the principle of pre-embedding computation into transmitted waveforms or on exploiting massive antenna arrays, often requiring the wireless multiple-access channel (MAC) to operate under conditions that approximate an ideal computational medium. This paper introduces a new computation framework, termed out-of-air computation (AirCPU), which establishes a joint source-channel coding foundation in which computation is not embedded before transmission but is instead extracted from the wireless superposition by exploiting structured coding. AirCPU operates directly on continuous-valued device data, avoiding the need for a separate source quantization stage, and employs a multi-layer nested lattice architecture that enables progressive resolution by decomposing each input into hierarchically scaled components, all transmitted over a common bounded digital constellation under a fixed power constraint. We formalize the notion of decoupled resolution, showing that in operating regimes where the decoding error probability is sufficiently small, the impact of channel noise and finite constellation constraints on distortion becomes negligible, and the resulting computation error is primarily determined by the target resolution set by the finest lattice. For fading MACs, we further introduce collective and successive computation mechanisms, in addition to the proposed direct computation, which exploit multiple decoded integer-coefficient functions and side-information functions as structural representations of the wireless superposition to significantly expand the reliable operating regime; in this context, we formulate and characterize the underlying reliability conditions and integer optimization problems, and develop a structured low-complexity two-group approximation to address them.
2604.04312Apr 2026
View
Robust MMSE Precoding for Out-of-Cluster Interference Mitigation in Cell-Free MIMO Networks
In this work, we develop a linear robust minimum mean-square error (RMMSE) precoder to mitigate the effects of imperfect channel state information (CSI) and the intra-cluster (ICL) and out-of-cluster (OCL) interference in cell-free (CF) multiple-antenna systems. The proposed precoder includes statistical information of the OCL interference in its derivation, allowing a more effective interference mitigation. An analysis of the sum-rate that can be obtained by the CF system is carried out and an expression quantifying the theoretical gains of mitigating OCL interference are derived. Simulation results corroborate that the proposed RMMSE precoder effectively mitigates ICL and OCL interference.
2604.04309Apr 2026
View
Would Learning Help? Adaptive CRC-QC-LDPC Selection for Integrity in 5G-NR V2X
Vehicle-to-everything (V2X) communications impose stringent physical-layer integrity requirements, particularly under short-packet transmission and mobility-induced channel variation. This paper studies whether standard-compliant online selection of Cyclic Redundancy Check (CRC) polynomials and Quasi-Cyclic Low-Density Parity-Check (QC-LDPC) coding rates can reduce silent (undetected) errors in 5G New Radio (5G-NR) V2X links. The joint configuration problem is formulated as a lightweight Contextual Bandit (CB) with a small, discrete action space, and a discounted LinUCB policy is evaluated against greedy online adaptation and a conservative fixed baseline. A 5G-NR-compliant physical-layer simulation is developed using Sionna, modeling mobility through time-correlated Rayleigh fading, where vehicle speed governs channel correlation, and non-stationary interference via a two-state Markov process. The learning agent operates on coarse receiver feedback, including a noisy Signal-to-Noise Ratio (SNR) estimate and indicators of burst interference and deep fades, and targets minimization of the Undetected Error Probability ((P{UE})) while accounting for the Detected Error Probability ((P{DE})). Overall, our objective is to delineate the mobility regimes in which learning-assisted CRC-QC-LDPC configuration improves physical-layer integrity in 5G-NR V2X systems. Our results indicate that learning-assisted adaptation is most effective at low to moderate mobility, reducing (P_UE) by up to 50-70% relative to greedy selection in the low-SNR regime ((-5) to 5~dB) and approaching the best fixed configuration at higher (E_b/N_0). At high mobility (>= 180~km/h), fast channel decorrelation weakens temporal predictability, limiting the effectiveness of online learning and reducing performance differences across policies.
2604.04277Apr 2026
View
Mechanism and Communication Co-Design for Differentially Private Energy Sharing
Integrating distributed energy resources (DERs) is a critical step toward addressing the global climate crisis. This transformation has driven the transition from traditional consumers to prosumers and given rise to new energy sharing business models. Existing works have extensively studied prosumer energy sharing mechanisms, yet little attention has been paid to privacy protection, particularly when communication constraints are taken into account. In this paper, we study an energy sharing mechanism where information is exchanged over wireless channels via over-the-air (OTA) multiple-input multiple-output (MIMO) aggregation to exploit spectral efficiency for scalable prosumer coordination. To characterize the privacy leakage risk during data transmission process, we introduce an adversarial attack model and demonstrate that, under certain conditions, the platform can extract and recover prosumers' private parameters from the base station observations. To safeguard the energy sharing mechanism against such attacks, we propose a differentially private equilibrium-seeking algorithm, analyze the achievable privacy level, and establish convergence guarantees that quantify the impact of privacy on the convergence accuracy. Numerical experiments demonstrate that our approach effectively protects prosumers' privacy while converging to near-optimal solutions.
2604.04125Apr 2026
View
On the Rate Region of I.I.D. Discrete Signaling and Treating Interference as Noise for the Gaussian Broadcast Channel
We revisit the Gaussian broadcast channel (GBC) and explore the rate region achieved by purely discrete inputs with treating interference as noise (TIN) decoding. Specifically, we introduce a simple scheme based on superposition coding with identically and independently distributed (i.i.d.) inputs drawn from discrete constellations, e.g., pulse amplitude modulations (PAM). Most importantly, we prove that the resulting achievable rate region under TIN decoding is within a constant gap to the capacity region of the GBC, where the gap is independent of all channel parameters. In addition, we show via simulation that the weak user can achieve a higher rate with PAM than with Gaussian signaling in some cases.
2604.04092Apr 2026
View
Quasi-BP for BCH Codes and its Optimization
This paper proposes a quasi-belief propagation decoder for BCH codes that systematically integrates domain knowledge--specifically, channel noise variance, the cyclic property of the codes, and the deliberate redundancy in their parity-check matrices--to enable efficient iterative decoding. We rigorously formalize this parallelizable decoder within an information-theoretic framework by tracking mutual information evolution through the constituent variable and check decoders, thereby validating the use of scattered EXIT charts as a tool for optimizing the decoder's parameters. At each iteration, an input dilation operation expands the set of messages, while a subsequent merging operation accelerates mutual information growth, ensuring rapid convergence. The proposed decoder achieves decoding performance approaching that of LDPC codes with comparable rate and blocklength, effectively pioneering the feasible deployment of BP-like decoding for high-density parity-check codes. The generality and robustness of the scheme are demonstrated through extensive simulations across codes of varying rates and blocklengths.
2604.04066Apr 2026
View
CTD-Diff: Cooperative Time-Division Diffusion for Multi-User Semantic Communication Systems
Semantic communication (SemCom) has emerged as a transformative paradigm for efficient information transmission by emphasizing the exchange of task-relevant meaning rather than raw data. While diffusion-based SemCom models have demonstrated remarkable generative capabilities, existing studies predominantly focus on point-to-point links, overlooking the potential of multi-user (MU) cooperation in MU wireless environments. To address this limitation, we propose a Cooperative Time-Division Diffusion (CTD-Diff) framework. Unlike traditional approaches that view channel noise solely as a detriment, our framework innovatively integrates the noisy wireless transmission process directly into the forward diffusion chain. Specifically, we design a multi-user cooperation mechanism based on Time-Division Multiple Access (TDMA), where idle users overhearing the active transmitter act as semantic collaborators. To maximize the signal fidelity, the receiver employs direct signal aggregation to fuse the direct signal with cooperative copies. This aggregated noisy semantic representation serves as the condition for the reverse diffusion process, allowing the receiver to reconstruct high-fidelity data by mitigating the cumulative channel distortions. By effectively converting physical channel noise into diffusion noise, the proposed method significantly enhances the transmission reliability. Extensive experiments demonstrate that CTD-Diff outperforms various baselines regarding the reconstruction accuracy and the perceptual quality, particularly under challenging low signal-to-noise ratio (SNR) conditions.
2604.04057Apr 2026
View
Environment-Aware Near-Field Channel Estimation Leveraging CKM and ISAC
This paper proposes an environment-aware near-field channel estimation framework for integrated sensing and communication (ISAC) systems equipped with extremely large-scale antenna arrays (ELAAs). The proposed framework jointly exploits channel knowledge maps (CKMs) and ISAC to obtain a priori information on static and dynamic environmental features for facilitating channel estimation. In particular, we propose a novel CKM representation, termed the virtual object map (VOM), which stores the locations of virtual environment objects (EOs) to characterize the dominant multipath components (MPCs) induced by static physical EOs. In addition, we design a sensing-assisted channel training protocol, in which the ISAC-enabled base station (BS) transmits downlink pilots while simultaneously collecting monostatic echoes for sensing dynamic targets in the environment, and the user equipment (UE) feeds back a quantized version of its received pilot observation. Based on the VOM prior and the sensed dynamic information, the BS jointly estimates the coefficients of the static and dynamic MPCs to recover the near-field channel. Numerical results demonstrate that the proposed joint VOM- and sensing-aided channel estimation scheme significantly outperforms conventional schemes without VOM-based priors and/or dynamic sensing in terms of both channel estimation accuracy and achievable rate.
2604.04031Apr 2026
View
Characterization of FR3 Cellular Vehicle-to-Base Station Links in HighRise Urban Scenarios
Driven by the escalating demand for wireless capacity and advancements in 6G research, the new Frequency Range 3 (FR3) referred to upper mid-band (7.125-24.25 GHz) has emerged as a highly compelling spectrum candidate. This range offers a trade-off exploiting the high bandwidth capabilities of millimeter wave frequencies and the superior propagation characteristics of sub-6 GHz bands. As such, the upper mid-band presents an opportunity to enhance both coverage and capacity particularly in the context of 6G and Cellular Vehicle-to-Base Station (C-V2B). Crucially, realizing this potential requires overcoming technical challenges through accurate and realistic channel modeling, especially in dense, high-rise urban environments. To address this, we employ a ray-tracing tool to analyze downlink propagation characteristics, enabling detailed channel modeling for reliable C-V2B communication. Our analysis evaluates the signal-to-noise ratio (SNR) and signal-to-interference-plus-noise ratio (SINR) across sub-6 GHz, FR3, and mmWave bands using antenna array configurations designed for high-rise urban areas. Results show that, under equal aperture sizes across frequencies, FR3 achieves superior SNR compared to mmWave in interference-free conditions. Moreover, under the full-interference case, FR3 yields higher SINR for cell-edge User Equipment (UEs). This indicates that the increased array gain at mmWave cannot fully compensate for the severe path loss experienced by cell-edge UEs.
2604.03992Apr 2026
View2604.03991On Polycyclic Codes over $\frac{\mathbb{F}_{p^m}[u]}{\langle u^t \rangle}$ and their Cardinalities
The purpose of this article is to study polycyclic codes over the ring $\frac{\mathbb{F}_{p^m}[u]}{\langle u^t \rangle}, \,t \geq 1$, and their associated torsion codes. It is shown that if $φ$ is a surjective ring homomorphism from a commutative ring $A$ to a Noetherian ring $B$ with $ ker(φ)=\langle π\rangle$ then for every ideal $I$ of $A$, there exists $a_1,a_2,\dots,a_n$ in $I$ such that $I=\langle a_1,a_2,\dots,a_n\rangle+π(I:π)$. Using this, we obtain generators of all ideals of the ring $\frac{\frac{\mathbb{F}_{p^m}[u]}{\langle u^t \rangle}[x]}{\langle ω(x)\rangle},$ where $ω(x)\in \frac{\mathbb{F}_{p^m}[u]}{\langle u^t \rangle}[x] $. For the case when $ω(x)=f(x)^{p^s}$, where $f(x)$ is an irreducible polynomial in $\mathbb{F}_{p^m}[x]$ and $s$ is a non-negative integer, we obtain several other results including computation of torsion ideals and their torsional degrees when $t=4$. We use the torsional degree to compute the cardinality of polycyclic codes over the ring $\frac{\mathbb{F}_{p^m}[u]}{\langle u^4 \rangle}$.
2604.03991Apr 2026
View2604.03987Hemispherical Concentration for Semi-Unsourced Random Access in Many-Access Regime
We study a semi-unsourced random access model in which a lightweight coordinator assigns distinct identifiers from a set $\mathcal{D}$ to the active users. Each active user then chooses a message uniformly at random from $\mathcal{M}$, forming an ID-message pair. The users share a spherical codebook whose codewords are drawn independently and uniformly from the hypersphere of radius $\sqrt{nP}$. We analyze the systme in the many-access channel regime, where the number of active users satisfies $K_a(n)=βn+o(n)$, and assume that the total codebook size is $M_n=|\mathcal{D}||\mathcal{M}|=αn+o(n)$. We show that, for $0<β\leq 1$, any $K_a(n)$-subset is almost surely contained in a single hemisphere, and for $1<β<2$, this hemispherical property holds with probability tending to one exponentially. Upon observing the channel output $\mbox{\boldmath $Y$}$, the decoder operates in two steps. In the pre-filtering step, it restricts the sphere to a sequence of spherical caps $\{ \hat{\mathcal{H}}_{n}\}$ converging to the hemisphere with direction $\hat{\mbox{\boldmath $u$}}=\mbox{\boldmath $Y$}/\| \mbox{\boldmath $Y$}\|$ as $n\rightarrow \infty$. In the subsequent maximum likelihood (ML) step, it performs ML estimation over the reduced candidate set. We show that per-user error probability of the pre-filtering step vanishes as $n\rightarrow \infty$, and that the worst-case asymptotic exponential decay rate of the per-user ML error probability over the reduced search space is $P/4$.
2604.03987Apr 2026
View
Structural Impossibility of Antichain-Lattice Partial Information Decomposition
Partial Information Decomposition (PID) represents multivariate mutual information via antichain-lattice that aims to specify which source groups can recover which informational components of a target. For three or more sources, widely desired PID axioms become mutually incompatible. This is often treated as an axiomatic tuning issue. This paper argues that the obstruction is representational, rooted in the antichain indexing itself, so that purely axiomatic adjustments within an antichain-lattice structure cannot resolve it in general. We first introduce System Information Decomposition (SID) for the special target-free three-variable setting, obtaining a self-consistent entropy decomposition with an operational redundancy definition. More fundamentally, we then show that for general multivariate PID, there is no universal rule that recovers the decomposed mutual information from the antichain-indexed information atoms. In particular, two systems can share identical atoms regardless of any axioms while having different mutual information. These results reveal the limits of antichain-lattice and motivate relation-based foundations for multivariate information measures.
2604.03869Apr 2026
View2604.03734Binary Caps and LCD Codes with Large Dimensions
We establish a connection between linear complementary dual (LCD) codes and caps in projective space. Using this framework and the structure theory of maximal caps, we derive nonexistence theorems for LCD codes with minimum distance at least $4$, providing computation-free proofs that were previously obtained only through exhaustive search. As an application, we completely determine the optimal minimum distances for codimensions $7$ and $8$ for the first time.
2604.03734Apr 2026
View
Region-Based Constellation Designs for Constructive Interference Precoding in MU-MIMO
The performance of constructive interference precoding (CIP) for multi-user multi-antenna (MU-MIMO) systems is governed by the structure of the constructive interference (CI) regions, yet this is overlooked in conventional constellation design. This work proposes the region-based constellation (RBC) model to lay the foundation for CIP constellation design. An RBC directly defines the mapping between messages and their feasible regions, instead of deriving them from an existing constellation. To provide insight for RBC design, we study the limitations of quadrature-amplitude-modulation (QAM)-based CIP. Analytical results show that the restrictive CI regions of QAM symbols are systematically misaligned with the objective-minimising sign pattern, resulting in a significant gap to the theoretical performance limit. From the perspective of improving sign alignment, two novel RBC schemes with non-convex feasible regions are proposed, namely mirrored-ends QAM (ME-QAM) and real-extended ME-QAM. A low-complexity algorithm is also developed for the resulting mixed-integer quadratic program, achieving a complexity comparable to QAM-based CIP. Simulation results with constellation sizes $\{16,64\}$ demonstrate up to $4$~dB signal-to-noise-ratio gain of the proposed schemes over QAM-based CIP. The proposed RBC model is also applicable to other systems with non-bijective modulation, representing a promising direction for future research.
2604.03699Apr 2026
ViewPage 1 of 276
