Capacity Of Communication Channel Research Articles

Effect of Core Geometry on Frequency Correlations and Channel Capacity of a Multimode Optical Fiber

Photons are the fundamental carriers of classical and quantum information across long distances via optical fibers. Multimode fibers with many transverse optical modes can support high‐capacity communication through space‐division multiplexing. While spatial correlations in light transmission via fibers have been investigated for counteracting mode mixing, less is known about frequency correlations, which are critical for high‐capacity communication using ultrashort pulses. This study uses complex wavefront shaping methods to investigate how core geometry affects the frequency correlation bandwidth of structured wavefronts in circular and rectilinear‐core fibers. Measurements reveal that rectilinear‐core fibers exhibit up to a 40% increase in frequency correlation bandwidth compared to circular core fibers, particularly when focusing light away from the fiber center—common in spatially multiplexed optical communication. This enhanced bandwidth results in a 20% boost in optical communication channel capacity, highlighting the potential of rectilinear core fibers. Furthermore, this observation of novel spatiotemporal wave correlations could be exploited for application of rectilinear core fibers in chip‐to‐chip interconnects for photonic quantum processors, contributing to scale up of photonic quantum technologies.

Electromagnetic Signaling Outperforms Quorum Sensing in Bacterial Biofilms: A Communication Channel Capacity Perspective

Electromagnetic Signaling Outperforms Quorum Sensing in Bacterial Biofilms: A Communication Channel Capacity Perspective

Distributed multi-object tracking under limited field of view heterogeneous sensors with density clustering

We consider the problem of tracking multiple, unknown, and time-varying numbers of objects using a distributed network of heterogeneous sensors. In an effort to derive a formulation for practical settings, we consider limited and unknown sensor field-of-views (FoVs), sensors with limited local computational resources and communication channel capacity. The resulting distributed multi-object tracking algorithm involves solving an NP-hard multidimensional assignment problem either optimally for small-size problems or sub-optimally for general practical problems. For general problems, we propose an efficient distributed multi-object tracking algorithm that performs track-to-track fusion using a clustering-based analysis of the state space transformed into a density space to mitigate the complexity of the assignment problem. The proposed algorithm can more efficiently group local track estimates for fusion than existing approaches. To ensure we achieve globally consistent identities for tracks across a network of nodes as objects move between FoVs, we develop a graph-based algorithm to achieve label consensus and minimise track segmentation. Numerical experiments with synthetic and real-world trajectory datasets demonstrate that our proposed method is significantly more computationally efficient than state-of-the-art solutions, achieving similar tracking accuracy and bandwidth requirements but with improved label consistency.

Dual-mode 1 × 2 optical switch with simultaneous modulation based on inverse design devices

Abstract Mode division multiplexing (MDM) technology, based on the parallelism inherent in mode dimensions, provides an advancement in enhancing on-chip optical communication channel capacity. In MDM communication systems, the routing and switching of optical signals are of essential importance. However, conventional multimode optical switches typically follow the demultiplexing-processing-multiplexing technological route, leading to an unavoidable increase in device size. In scenarios where multiple modes need to be routed synchronously, the implementation of simultaneous modulation optical switches offers a more efficient and feasible solution. Here, we propose two 1×2 dual-mode optical switches with simultaneous modulation on a silicon-on-insulator (SOI) platform in the 1525-1565 nm wavelength range, utilizing two optical phase modulation techniques: mode transformation and waveguide widening. Simultaneously, we employ inverse design methodologies based on the adjoint variable method (AVM) and level-set method to create the compact single-connected devices, which are compatible with CMOS fabrication processes. The experimental results show that the insertion losses for both TE0 and TE1 modes are less than 1.6 dB (2.5 dB), with the worst modal crosstalk at most -13.5 dB (-12.7 dB) for the switch based on mode transformation (waveguide widening) strategy at the wavelength of 1550nm. The extinction ratio (ER) of the two proposed optical switches exceeds 25 dB at the same wavelength. Furthermore, the switches exhibit a 10%-90% rise time of 15.2 μs and a 90%-10% fall time of 19.5 μs at 1550 nm, indicating the switching speed can be up to kilohertz (kHz). Our proposed 1×2 optical switches hold potential as a fundamental unit for optical signal switching in high-integration multimode optical communication systems.

Ultra‐Wideband Terahertz Integrated Polarization Multiplexer

AbstractPolarization‐division multiplexing is crucial for increasing channel capacity and spectral efficiency in communications. A key component is the polarization multiplexer, which combines or separates signals with orthogonal polarizations. Existing planar multiplexers lack an ultrawide band for terahertz communications. While microwave‐inspired orthomode transducers (OMTs) provide broadband operation, they suffer from high ohmic loss and bulkiness at terahertz frequencies. Optical integrated polarization beam splitters (PBSs) offer low loss and good integrability but have narrow bandwidths. This work presents a substrateless all‐silicon polarization multiplexer based on tapered directional couplers and air‐silicon effective mediums, integrated monolithically on a compact footprint. The device demonstrates a 37.8% fractional bandwidth, an average insertion loss of 1 dB, and a polarization extinction ratio above 20 dB over 225–330 GHz. This superior performance is enabled by the anisotropy of the effective medium claddings, affecting the two orthogonal guided modes differently. The multiplexer enables simultaneous two‐channel terahertz fiber communications with polarization diversity. It supports aggregated data rates up to 155 and 190 Gbit with bit error rates below hard‐ and soft‐decision forward‐error‐correction limits, respectively. This advancement holds promise for 6G terahertz integrated systems with enhanced channel capacities.

The Design of a Multifunctional Coding Transmitarray with Independent Manipulation of the Polarization States.

Manipulating orthogonally polarized waves independently in a single metasurface is pivotal. However, independently controlling the phase shifts of orthogonally polarized waves is difficult, especially in the same frequency bands. Here, we propose a receiver-phase shift-transmitter transmitarray with independent control of arbitrary polarization states in the same frequency bands, in which transmission rates reach more than 90% in the frequency bands 4.2~4.9 GHz and 5.3~5.5 GHz. By introducing a phase-regulation structure to each element, phases covering 360° for different polarized incident waves can be independently controlled by different geometric parameters, and two-bit coding phases can be obtained. The design principle based on the two-port network's scattering matrix has been analyzed. To verify the independent tuning abilities of the proposed transmitarray for different polarization incidences in the same frequency bands, a multifunctional receive-phase shift-radiation coding transmitarray (RPRCT), which is composed of 16×16 elements, with functions of anomalous refraction (for example, orbital angular momentum wave) and focusing transmission for different polarized incident waves was simulated and measured. The measured results agree reasonably well with the simulated ones. Our findings provide a simple method for obtaining a multifunctional metasurface with orthogonal polarization in the same frequency bands, which greatly improves the capacity and spectral efficiency of communication channels.

Warm Rydberg atom-based quadrature amplitude-modulated receiver.

Rydberg atoms exhibit both remarkable sensitivity to electromagnetic fields making them promising candidates for revolutionizing field sensors and, unlike conventional antennas, they neither disturb the measured field nor necessitate extensive calibration procedures. In this study, we propose a receiver design for data-modulated signal reception near the 2.4 GHz Wi-Fi frequency band, harnessing the capabilities of warm Rydberg atoms. Our focus lies on exploring various quadrature amplitude modulations and transmission frequencies through heterodyne detection. We offer a comprehensive characterization of our setup, encompassing the atomic response frequency range, attainable electric field amplitudes, and sensitivity, which we estimate to be equal to 0.50 µV cm-1 Hz-0.5. Additionally, we delve into analyzing communication errors using Voronoi diagrams and evaluating the communication channel capacity across different modulation schemes. We find that the maximum achievable capacity for a single communication channel equals 19.3 Mbps and can be achieved using the Q A M4 scheme.

High-Capacity Multiple-Input Multiple-Output Communication for Internet-of-Things Applications Using 3D Steering Nolen Beamforming Array

In this paper, a novel 2D Nolen beamforming phased array with 3D scanning capability to achieve high channel capacity is presented for multiple-input multiple-output (MIMO) Internet-of-Things (IoT) applications. The proposed 2D beamforming phased array is designed by stacking a fundamental building block consisting of a 3 × 3 tunable Nolen matrix, which applies a small number of phase shifters with a small tunning range and reduces the complexity of the beam-steering control mechanism. Each 3 × 3 tunable Nolen matrix can achieve a full 360° range of progressive phase delay by exciting all three input ports, and nine individual radiation beams can be generated and continuously steered on azimuth and elevation planes by stacking up three tunable Nolen matrix in horizontal and three in vertical to maximize signal-to-noise ratio (SNR) in the corresponding spatial directions. To validate the proposed design, the simulations have been conducted on the circuit network and assessed in a fading channel environment. The simulation results agree well with the theoretical analysis, which demonstrates the capability of the proposed 2D Nolen beamforming phased array to realize high channel capacity in MIMO-enabled IoT communications.

An artificial potential field approach for event-triggered cooperative control of multiple high-speed trains with free initial states

ABSTRACT In this paper, a multi-algorithm-fusion-based cooperative tracking control strategy is proposed for high-speed trains to achieve the control objectives of reference speed trajectory tracking and adjacent safety distance maintenance simultaneously. First, the multiple high-speed train (MHST) system is formulated as a multi-agent system (MAS) with a virtual leader. Second, a coordination controller that considers the dynamic tracking performance and input saturation is designed by combining the MAS leader-follower consensus algorithm and the improved artificial potential field (APF) method. In addition, within the train-to-train (T2T) communication network, an event-triggered mechanism is introduced in the continuous state transmission process to address the communication channel capacity protection limitation issue. Third, the closed-loop stability of the MHST system is ensured by the comprehensive analysis of a novel log-type Lyapunov function. Finally, the effectiveness of the proposed event-triggered cooperative tracking control strategy is verified through a numerical example of the MHST system on a typical line.

High-speed independent polarization modulation based on dual channel 2DEG anisotropic terahertz metasurfaces.

In communication and imaging systems, anisotropic metasurfaces bring new degrees of freedom for the independent control of electromagnetic waves with different polarizations. This paper proposes a dual-polarization modulation metasurface (DPMM) operating in the terahertz (THz) frequency range, which can effectively and independently modulate two orthogonally linearly polarized electromagnetic waves. The metasurface unit adopts an anisotropic structure, and by integrating multiple GaN-based high electron mobility transistors (GaN-HEMTs) into the anisotropic structure, independent control of the two-dimension electron gas (2DEG) carrier concentration in the dual-polarization channel is achieved, enabling selective modulation of x-polarization and y-polarization waves. Simulation and static experimental results demonstrate the excellent modulation isolation performance of the DPMM, with a maximum isolation exceeding 45 dB. Dynamic experiments further highlight the high-speed modulation effect, with modulation speeds exceeding 1 GHz for a single channel and an overall modulation speed of 2 GHz for dual polarization, highlighting its potential for enhancing channel capacity and information throughput in THz communication and imaging systems.

Modern approaches to compression and noise resistant encoding of photo and video information in radio channels of complexes with unmanned aerial vehicle

Modern complexes with unmanned aerial vehicles (UAVs) of long flight duration (heavy class) are in practice equipped with a wide range of target loads, which leads to the need to transmit a large amount of useful information in real time with the required quality to a remote ground control station (GCS). The large volume of transmitted information imposes serious technical requirements on the capacity of communication channels, which, on the one hand, when designing communication systems within UAVs, is ensured by the use of directional antenna systems, multi-position signal-code structures, noise-resistant coding, high energy in the communication channel, etc. On the other hand, developers simultaneously solve the problem of minimizing the amount of information from target loads supplied to the input of the communication system while maintaining the required quality after compression. This article discusses the main information compression standards used by CUAVs developers, their advantages and disadvantages, as well as video codecs based on three-dimensional orthogonal transformations.

On-chip terahertz orbital angular momentum demultiplexer

The terahertz regime is widely recognized as a fundamental domain with significant potential to address the demands of next-generation wireless communications. In parallel, mode division multiplexing based on orbital angular momentum (OAM) shows promise in enhancing bandwidth utilization, thereby expanding the overall communication channel capacity. In this study, we present both theoretical and experimental demonstrations of an on-chip terahertz OAM demultiplexer. This device effectively couples and steers seven incident terahertz vortex beams into distinct high-quality focusing surface plasmonic beams, and the focusing directions can be arbitrarily designated. The proposed design strategy integrates space-to-chip mode conversion, OAM recognition, and on-chip routing in a compact space with subwavelength thickness, exhibiting versatility and superior performance.

A Joint Intensity-Neuromorphic Event Imaging System With Bandwidth-Limited Communication Channel.

We present a novel adaptive multimodal intensity-event algorithm to optimize an overall objective of object tracking under bit rate constraints for a host-chip architecture. The chip is a computationally resource-constrained device acquiring high-resolution intensity frames and events, while the host is capable of performing computationally expensive tasks. We develop a joint intensity-neuromorphic event rate-distortion compression framework with a quadtree (QT)-based compression of intensity and events scheme. The goal of this compression framework is to optimally allocate bits to the intensity frames and neuromorphic events based on the minimum distortion at a given communication channel capacity. The data acquisition on the chip is driven by the presence of objects of interest in the scene as detected by an object detector. The most informative intensity and event data are communicated to the host under rate constraints so that the best possible tracking performance is obtained. The detection and tracking of objects in the scene are done on the distorted data at the host. Intensity and events are jointly used in a fusion framework to enhance the quality of the distorted images, in order to improve the object detection and tracking performance. The performance assessment of the overall system is done in terms of the multiple object tracking accuracy (MOTA) score. Compared with using intensity modality only, there is an improvement in MOTA using both these modalities in different scenarios.

Differentially Private Consensus for Second-Order Multiagent Systems With Quantized Communication.

This article considers the differentially private consensus problem of discrete-time second-order multiagent systems with partially measurable states and limited communication channel capacity, where only the integer-value information of agents can be transmitted. To reduce the potential risk of state information disclosure in digital communication, a differentially private consensus algorithm via dynamic encoding-decoding is proposed for the second-order multiagent system to make agents achieve mean-square consensus by transmitting quantized integer values with privacy protection. To deal with the uncertainty of the quantizer saturation, the statistical analysis is given for the boundedness of the input of quantizers. It is shown that the expectation of the minimum memory capacity of quantizers is 2 bits. Finally, some simulation results are given to visualize our conclusions.

Improvement of Channel Capacity of MIMO Communication Using Yagi-Uda Planar Antennas with a Propagation Path through a PVC Pipe Wall

Improvement of Channel Capacity of MIMO Communication Using Yagi-Uda Planar Antennas with a Propagation Path through a PVC Pipe Wall

Charakteryzacja termograficznego kanału skrytej komunikacji

The paper presents a method for determining the characteristics of the information capacity of a thermographic covert communication channel made of a heat radiator (technical black body) and a thermal camera. The determined characteristics are an additional parameter describing these devices in the context of their non-obvious use for data transmission.

Hyper-parallel nonlocal CNOT operation assisted by quantum-dot spin in a double-sided optical microcavity

Implementation of controlled-NOT (CNOT) operation between different nodes in a quantum communication network nonlocally plays an important role in distributed quantum computation. We present a protocol for implementation of hyper-parallel nonlocal CNOT operation via hyperentangled photons simultaneously entangled in spatial-mode and polarization degrees of freedom (DOFs) assisted by quantum-dot spin in a double-sided optical microcavity. The agent Alice lets photons traverse the double-sided optical microcavity sequentially and applies single-qubit measurements on the electron and the hyperentangled photon. The agent Bob first performs corresponding unitary operations according to Alice’s measurement results on his hyperentangled photon, and then lets photons traverse the double-sided optical microcavity sequentially and performs the single-qubit measurements on the electron and the hyperentangled photon. The hyper-parallel nonlocal CNOT operation can be implemented simultaneously in spatial-mode and polarization DOFs if Alice performs single-qubit operations in accordance with Bob’s measurement results. The protocol has the advantage of having high channel capacity for long-distance quantum communication by using a hyperentangled state as the quantum channel.

Dual-mode vortex beam transmission metasurface antenna based on linear-to-circular polarization converter.

The generation of multi-mode vortex beams at the same aperture is currently emerging as a research hotspot. In this paper, a method based on a linearly polarized-circularly polarized translational transmission metasurface (TM) is proposed to enable a dual-circularly polarized dual-mode vortex beam generation. Through the judicious implementation of an additional rotational phase and the combination of the initial transmission phase, the phases of the left-hand circularly polarized (LHCP) and right-hand circularly polarized (RHCP) waves can be manipulated arbitrarily and independently. Meanwhile, the design of the array phase is utilized for the dual-mode dual-circularly polarized beam generation. Simulation and sample measurements provide validation data for the feasibility of this method, in which the measurement results are in excellent consistency with the simulation ones. This proposed method paves the way toward the enhancement of the channel capacity of mobile communication.

On the Capacity of Communication Channels With Memory and Sampled Additive Cyclostationary Gaussian Noise

In this work we study the capacity of interference-limited channels with memory. These channels model non-orthogonal communications scenarios, such as the non-orthogonal multiple access (NOMA) scenario and underlay cognitive communications, in which the interference from other communications signals is much stronger than the thermal noise. Interference-limited communications is expected to become a very common scenario in future wireless communications systems, such as 5G, WiFi6, and beyond. As communications signals are inherently cyclostationary in continuous time (CT), then after sampling at the receiver, the discrete-time (DT) received signal model contains the sampled desired information signal with additive sampled CT cyclostationary noise. The sampled noise can be modeled as either a DT cyclostationary process or a DT almost-cyclostationary process, where in the latter case the resulting channel is not information-stable. In a previous work we characterized the capacity of this model for the case in which the DT noise is memoryless. In the current work we come closer to practical scenarios by modelling the resulting DT noise as a finite-memory random process. The presence of memory requires the development of a new set of tools for analyzing the capacity of channels with additive non-stationary noise which has memory. Our results show, for the first time, the relationship between memory, sampling frequency synchronization and capacity, for interference-limited communications. The insights from our work provide a link between the analog and the digital time domains, which has been missing in most previous works on capacity analysis. Thus, our results can help improving spectral efficiency and suggest optimal transceiver designs for future communications paradigms.

Precise On-Chip Spectral and Temporal Control of Single-Photon-Level Optical Pulses

The constantly growing need for fast and secure optical communication systems resulted in the rapid development of classical and quantum photonic technologies. Continuous research on improving the capacities of communication channels and the efficiency of optical information processing systems were naturally followed by miniaturization. Photonic integration combined with spectral-temporal multiplexing has led to improvements in communications. In this paper, we present accurate control of temporal and spectral profiles of optical pulses generated at the telecom wavelengths using an indium phosphide-based photonic integrated circuit. The device enables simultaneous temporally and spectrally resolved measurements using single photon counting. We discuss its applications in multidimensional time-frequency quantum key distribution, where security relies on time-frequency uncertainty, and other applications.