On the Capacity of Waveform Channels Under Square-Law Detection of Time-Limited Signals

有限信噪比下方形马尔琴科-帕斯图尔（Marčenko-Pastur）多输入多输出（MIMO）容量的闭式解

Finite-SNR Closed Form for the Square Marčenko-Pastur MIMO Capacity

本研究针对方形比值的MIMO信道，通过三角参数化方法获得有限SNR下容量的闭式解，填补了该比值仅能数值计算的空白，还给出了低SNR下容量斜率的闭式结果。

盲二维超分辨率中原子范数去噪的数学理论（扩展版）

Mathematical Theory of Atomic Norm Denoising In Blind Two-Dimensional Super-Resolution (Extended Version)

本文提出基于原子范数的盲二维超分辨率去噪数学框架，可从含噪信号中估计无噪信号与未知参数，推导了均方误差理论界并通过仿真验证结论。

On the capacity of bandlimited optical intensity channels with Gaussian noise

We determine lower and upper bounds on the capacity of bandlimited optical intensity channels (BLOIC) with white Gaussian noise. Three types of input power constraints are considered: 1) only an average power constraint, 2) only a peak power constraint, and 3) an average and a peak power constraint. Capacity lower bounds are derived by a two-step process including 1) for each type of constraint, designing admissible pulse amplitude modulated input waveform ensembles, and 2) lower bounding the maximum achievable information rates of the designed input ensembles. Capacity upper bounds are derive…

Conditional Capacity and Transmit Signal Design for SWIPT Systems with Multiple Nonlinear Energy Harvesting Receivers

We study information-theoretic limits for simultaneous wireless information and power transfer (SWIPT) systems employing nonlinear radio frequency (RF) energy harvesting (EH) receivers (Rxs). In particular, we consider a SWIPT system with one transmitter that broadcasts a common signal to an information decoding (ID) Rx and multiple EH Rxs. Owing to the nonlinearity of the EH Rxs' circuitry, the efficiency of wireless power transfer depends on the waveform of the transmitted signal. We aim to answer the following fundamental question: What is the optimal input distribution of the transmit sign…

Low-Complexity Linear Equalization for OTFS Systems with Rectangular Waveforms

Orthogonal time frequency space (OTFS) is a promising technology for high-mobility wireless communications. However, the equalization realization in practical OTFS systems is a great challenge when the non-ideal rectangular waveforms are adopted. In this paper, first of all, we theoretically prove that the effective channel matrix under rectangular waveforms holds the block-circulant property and the special Fourier transform structure with time-domain channel. Then, by exploiting the proved property and structure, we further propose the corresponding low-complexity algorithms for two mainstre…

Polar coding to achieve the Holevo capacity of a pure-loss optical channel

In the low-energy high-energy-efficiency regime of classical optical communications---relevant to deep-space optical channels---there is a big gap between reliable communication rates achievable via conventional optical receivers and the ultimate (Holevo) capacity. Achieving the Holevo capacity requires not only optimal codes but also receivers that make collective measurements on long (modulated) codeword waveforms, and it is impossible to implement these collective measurements via symbol-by-symbol detection along with classical postprocessing. Here, we apply our recent results on the classi…

单载波、OFDM与OTFS在毫米波多连接下行传输中的比较

A Comparison among Single Carrier, OFDM, and OTFS in mmWave Multi-Connectivity Downlink Transmissions

本文比较了毫米波多连接下行中SC、OFDM和OTFS三种波形，提出OTFS跨域迭代检测，以实际容量评估，显示OTFS以合理复杂度代价显著优于其他两者。

Least Squares Superposition Codes of Moderate Dictionary Size, Reliable at Rates up to Capacity

For the additive white Gaussian noise channel with average codeword power constraint, new coding methods are devised in which the codewords are sparse superpositions, that is, linear combinations of subsets of vectors from a given design, with the possible messages indexed by the choice of subset. Decoding is by least squares, tailored to the assumed form of linear combination. Communication is shown to be reliable with error probability exponentially small for all rates up to the Shannon capacity.

The Capacity Loss of Dense Constellations

We determine the loss in capacity incurred by using signal constellations with a bounded support over general complex-valued additive-noise channels for suitably high signal-to-noise ratio. Our expression for the capacity loss recovers the power loss of 1.53dB for square signal constellations.

On the Capacity of MIMO Interference Channels

The capacity region of a multiple-input-multiple-output interference channel (MIMO IC) where the channel matrices are square and invertible is studied. The capacity region for strong interference is established where the definition of strong interference parallels that of scalar channels. Moreover, the sum-rate capacity for Z interference, noisy interference, and mixed interference is established. These results generalize known results for the scalar Gaussian IC.

Non-Coherent Capacity and Reliability of Sparse Multipath Channels in the Wideband Regime

In contrast to the prevalent assumption of rich multipath in information theoretic analysis of wireless channels, physical channels exhibit sparse multipath, especially at large bandwidths. We propose a model for sparse multipath fading channels and present results on the impact of sparsity on non-coherent capacity and reliability in the wideband regime. A key implication of sparsity is that the statistically independent degrees of freedom in the channel, that represent the delay-Doppler diversity afforded by multipath, scale at a sub-linear rate with the signal space dimension (time-bandwidth…

Joint Transmitter and Receiver Optimization for Improper-Complex Second-Order Stationary Data Sequence

In this paper, the transmission of an improper-complex second-order stationary data sequence is considered over a strictly band-limited frequency-selective channel. It is assumed that the transmitter employs linear modulation and that the channel output is corrupted by additive proper-complex cyclostationary noise. Under the average transmit power constraint, the problem of minimizing the mean-squared error at the output of a widely linear receiver is formulated in the time domain to find the optimal transmit and receive waveforms. The optimization problem is converted into a frequency-domain …

双重稀疏时变信道估计与预测的模型、方法和波形

Models, Methods and Waveforms for Estimation and Prediction of Doubly Sparse Time-Varying Channels

本文针对延迟-多普勒双重稀疏的时变信道，提出基于压缩感知的on-grid估计框架和基于DPSS-BEM的离网格估计与预测模型，并证明AFDM波形在估计精度和开销上优于OFDM和SCM。

ISAC权衡悬崖：波形不确定性与有限块长下的基本极限

The ISAC Tradeoff Cliff: Fundamental Limits under Waveform Uncertainty and Finite Blocklength

本文针对ISAC系统，在有限块长解码不确定性下，推导感知性能的费舍尔信息与CRB，揭示通信可靠性边界即感知信息边界，刻画“权衡悬崖”转变，并给出临界速率表达式，为系统设计提供可靠性余量指导。

具有有限学习能力的集成感知与通信的信息论极限

Information-Theoretic Limits of Integrated Sensing and Communication with Finite Learning Capacity

本文提出了一种信息论框架，研究有限学习能力对集成感知与通信性能的影响，并建立了学习-信息权衡定律，为下一代 ISAC 系统设计提供理论指导。

Using Loaded N-port Structures to Achieve the Continuous-Space Electromagnetic Channel Capacity Bound

A method for achieving the continuous-space electromagnetic channel capacity bound using loaded N-port structures is described. It is relevant for the design of compact multiple-input multiple-output (MIMO) antennas that can achieve channel capacity bounds when constrained by size. The method is not restricted to a specific antenna configuration and a closed-form expression for the channel capacity limits are provided with various constraints. Furthermore, using loaded N-port structures to represent arbitrary antenna geometries, an efficient optimization approach is proposed for finding the op…

Capacity and Normalized Optimal Detection Error in Gaussian Channels

For vector Gaussian channels, a precise differential connection between channel capacity and a quantity termed normalized optimal detection error (NODE) is presented. Then, this C-NODE relationship is extended to continuous-time Gaussian channels drawing on a waterfilling characterization recently found for the capacity of continuous-time linear time-varying channels. In the latter case, the C-NODE relationship becomes asymptotic in nature. In either case, the C-NODE relationship is compared with the I-MMSE relationship due to Guo et al. connecting mutual information in Gaussian channels with …

Optimal Precoding Design for Monostatic ISAC Systems: MSE Lower Bound and DoF Completion

In this letter, we study the parameter estimation performance for monostatic downlink integrated sensing and communications (ISAC) systems. In particular, we analyze the mean squared error (MSE) lower bound for target sensing in the downlink ISAC system that reveals the suboptimality in re-using the conventional communication waveform for sensing. To realize a practical dual-functional waveform, we propose a waveform augmentation strategy that imposes an extra signal structure, namely the degrees-of-freedom (DoF) completion method. The proposed approach is capable of improving the parameter es…

Autocorrelation Function for Dispersion-Free Fiber Channels with Distributed Amplification

Optical fiber signals with high power exhibit spectral broadening that seems to limit capacity. To study spectral broadening, the autocorrelation function of the output signal given the input signal is derived for a simplified fiber model that has zero dispersion, distributed optical amplification (OA), and idealized spatial noise processes. The autocorrelation function is used to upper bound the output power of bandlimited or time-resolution limited receivers, and thereby to bound spectral broadening and the capacity of receivers with thermal noise. The output power scales at most as the squa…

关于随机通信波形的离散模糊函数

On Discrete Ambiguity Functions of Random Communication Waveforms

本文研究了随机通信波形的离散模糊函数，推导了期望边瓣水平和积分边瓣水平的闭式表达式，并揭示了不同调制方式在不同星座分布下的最优性能特性。

Optimal Correlators for Detection and Estimation in Optical Receivers

Motivated by modern applications of light detection and ranging (LIDAR), we study the model of an optical receiver based on an avalanche photo-diode (APD), followed by electronic circuitry for detection of reflected optical signals and estimation of their delay.This model is known to be quite complicated as it consists of at least three different types of noise: thermal noise, shot noise, and multiplicative noise (excess noise) that stems from the random gain associated with the photo-multiplication of the APD. Consequently, the derivation of the optimal likelihood ratio test (LRT) associated …

计算受限信号：一种受计算复杂度约束的信道容量机制

Computation-Limited Signals: A Channel Capacity Regime Constrained by Computational Complexity

提出计算受限信号概念与频谱计算分析框架，刻画计算复杂度开销如何约束通信容量，并证明 OFDM 在 N 点 DFT 下界复杂度未达 Ω(N) 时属于计算受限。

Closed-Form Expressions of Ergodic Capacity and MMSE Achievable Sum Rate for MIMO Jacobi and Rayleigh Fading Channels

Multimode/multicore fibers are expected to provide an attractive solution to overcome the capacity limit of the current optical communication system. In the presence of high cross-talk between modes/cores, the squared singular values of the input/output transfer matrix follow the law of the Jacobi ensemble of random matrices. Assuming that the channel state information is only available at the receiver, we derive a new expression for the ergodic capacity of the MIMO Jacobi fading channel. This expression involves double integrals which can be evaluated easily and efficiently. Moreover, the met…

Deep-Waveform: A Learned OFDM Receiver Based on Deep Complex-valued Convolutional Networks

The (inverse) discrete Fourier transform (DFT/IDFT) is often perceived as essential to orthogonal frequency-division multiplexing (OFDM) systems. In this paper, a deep complex-valued convolutional network (DCCN) is developed to recover bits from time-domain OFDM signals without relying on any explicit DFT/IDFT. The DCCN can exploit the cyclic prefix (CP) of OFDM waveform for increased SNR by replacing DFT with a learned linear transform, and has the advantage of combining CP-exploitation, channel estimation, and intersymbol interference (ISI) mitigation, with a complexity of $\mathcal{O}(N^2)$…

回声状态计算中信息处理能力的渐近评估

Asymptotic evaluation of the information processing capacity in reservoir computing

本文提出了一种基于渐近展开和加权最小二乘拟合的方法，用于评估回声状态计算中无限长数据的信息处理能力，以更准确地评估其性能。

用于稀疏时变信道通信的仿射频分复用

Affine Frequency Division Multiplexing For Communications on Sparse Time-Varying Channels

本文针对双重稀疏的线性时变信道，证明仿射频分复用（AFDM）波形在信道估计中能以最小导频和保护开销实现目标均方误差，优于传统及新近波形。