High-speed Wireless Communication Research Articles

Highly reliable integrated W-band transmitter based on an on-chip dual-mode DFB laser and cascaded microring modulators

We propose an integrated W-band transmitter enabled by an integrated dual-mode distributed feedback (DFB) laser and cascaded silicon photonic microring modulators for next-generation wireless communication. 10 Gb/s error-free intensity modulation and direct detection W-band transmission are achieved in experiments by using the dual-mode DFB laser and two free-running lasers. Moreover, we conduct an experiment of dual-carrier modulation based on cascaded microring modulators, achieving 3 dB signal-to-noise ratio improvement and better signaling integrity for wireless communication. The proposed photonic integrated W-band transmitter will be a viable solution for a high-speed and low-power wireless communication system.

Two-Stage Link Loss Optimization of Divergent Gaussian Beams for Narrow Field-of-View Receivers in Line-of-Sight Indoor Downlink Optical Wireless Communication (Invited)

The predominant focus of research in high-speed optical wireless communication (OWC) lies in line-of-sight (LOS) links with narrow infrared beams. However, the implementation of precise tracking and steering necessitates delicate active devices, thereby presenting a formidable challenge in establishing a cost-effective wireless transmission. Other than using none-line-of-sight (NLOS) links with excessive link losses and multi-path distortions, the simplification of the tracking and steering process can be alternatively achieved through the utilization of divergent optical beams in LOS. This paper addresses the issue by relaxing the stringent link budget associated with divergent Gaussian-shaped optical beams and narrow field-of-view (FOV) receivers in LOS OWC through the independent optimization of geometrical path loss and fiber coupling loss. More importantly, the geometrical path loss is effectively mitigated by modifying the transverse intensity distribution of the optical beam using manipulations of multi-mode fibers (MMFs) in an all-fiber configuration. In addition, the sufficiently excited higher order modes (HOMs) of MMFs enable a homogenized distribution of received optical powers (ROPs) within the coverage area, which facilitates the mobility of end-users. Comparative analysis against back-to-back links without free-space transmission demonstrates the proposed scheme’s ability to achieve low power penalties. With the minimized link losses, experimental results demonstrate a 10 Gbps error-free (BER < 10−13) LOS OWC downlink transmission at 2.5 m over an angular range of 10° × 10° without using any optical pre-amplifications at a typical PIN receiver. The proposed scheme provides a simple and low-cost solution for high-speed and short-range indoor wireless applications.

High-Speed Underwater Optical Wireless Communication with Advanced Signal Processing Methods Survey

Underwater wireless communication (UWC) technology has attracted widespread attention in the past few years. Compared with conventional acoustic underwater wireless communication technology, underwater optical wireless communication (UOWC) technology has promising potential to provide high data rate wireless connections due to the large license-free bandwidth. Building a high-performance and reliable UOWC system has become the target of researchers and various advanced and innovative technologies have been proposed and investigated. Among them, better hardware such as transmitters and receivers, as well as more advanced modulation and signal processing techniques, are key factors in improving UOWC system performance. In this paper, we review the recent development in UOWC systems. In particular, we provide a brief introduction to different types of UOWC systems based on channel configuration, and we focus on various recent studies on advanced signal processing methods in UOWC systems, including both traditional non-machine learning (NML) equalizers and machine learning (ML) schemes based on neural networks. In addition, we also discuss the key challenges in UOWC systems for future applications.

Multiband and high gain meandered metamaterial THz MIMO antenna for highspeed wireless communication applications

Multiband and high gain meandered metamaterial THz MIMO antenna for highspeed wireless communication applications

High-Speed and Long-Distance Photonics-Aided Terahertz Wireless Communication

Terahertz (THz) photonics technique can break through the bandwidth limitation of electronic mixing method and be seamless integrated with optical access networks, which has bright prospects in future 6G broadband communication. However, due to the bottleneck of photoelectric conversion efficiency of uni-travelling photodiode (UTC-PD), the power of the generated THz-wave signal is usually only in the microwatt level, and the THz-wave wireless transmission distance is short. In this paper, we summarize the key techniques we use to extend the wireless range for photonics-aided THz-wave communication, which includes THz-wave amplifiers and antennas, heterodyne detection, probabilistic shaping (PS) technique as well as advanced digital signal processing (DSP). Meanwhile, we report our recent research including 104\200\400-m photonics-aided THz-wave wireless transmission records.

Integration of Optical and Free Space Optics Network Architecture for High-Speed Communication in Adverse Weather using suitable Optical Bands

Free Space Optics (FSO) is a highly viable solution for high-speed wireless communication and is widely preferred over radio frequency communication systems because of its faster data transmission, no regulatory requirements and highly secure long-range operations. However, the capacity and availability of FSO optical bands are a significant concern in varying atmospheric conditions. Our objective is to enhance network flexibility and expand wireless network coverage in adverse weather conditions by combining optical and FSO links using optical bands C, S, and O. The study analyzed the performance of a hybrid 4 channels FSO-WDM system with a 100GHz or 0.8 nm channel spacing under different conditions, including adverse weather and varying data rates. An attenuation of 0.25 dB/km was fixed, and the system's performance was analyzed up to 3 km. The results showed that as the data rate increased, the system's performance declined, and the O band was the best performer up to 25 Gbit/s. BER values were analyzed at different weather conditions using the Kim model, and the O band consistently outperformed the S and C bands. Eye diagrams were used to evaluate the signal quality, and the O band was shown to perform better than the other two bands, even in adverse weather conditions. Overall, the study suggests that FSO is a viable solution for high-speed wireless communication, particularly when using the O band.

Transformer-Based Detection for Highly Mobile Coded OFDM Systems.

This paper is concerned with mobile coded orthogonal frequency division multiplexing (OFDM) systems. In the high-speed railway wireless communication system, an equalizer or detector should be used to mitigate the intercarrier interference (ICI) and deliver the soft message to the decoder with the soft demapper. In this paper, a Transformer-based detector/demapper is proposed to improve the error performance of the mobile coded OFDM system. The soft modulated symbol probabilities are computed by the Transformer network, and are then used to calculate the mutual information to allocate the code rate. Then, the network computes the codeword soft bit probabilities, which are delivered to the classical belief propagation (BP) decoder. For comparison, a deep neural network (DNN)-based system is also presented. Numerical results show that the Transformer-based coded OFDM system outperforms both the DNN-based and the conventional system.

A miniaturized and low-energy subcutaneous optical telemetry module for neurotechnology

Objective. This study presents a proof-of-concept optical telemetry module that leverages a single light-emitting diode (LED) to transmit data at a high bit rate while consuming low power and occupying a small area. Our experiments showed that we could achieve 108 Mbit s−1 and 54 Mbit s−1 back telemetry data rates for tissue thicknesses of 3 mm and 8 mm, respectively. Approach. The proposed module is designed to be powered by near-field coupling and achieve bidirectional communication by low-speed downlink from near-field communication. It aims to minimize the size of the implant while providing reliable transmission that meets the requirements of high-speed wireless communication from a multi-electrode array neurotechnology implant outside the body. Results. The power consumption of the module is 1.57 mW, including the power consumption of related circuits, resulting in an efficiency of 14.5 pJ bit−1, at a tissue thickness of 3 mm and a data rate of 108 Mbit. The use of an optical lens, combined with tissue scattering effect and optimized emission angle, makes the module robust to misalignments of up to ±5 mm and ±15° between the implantable and external units. The LED in the implantable unit is only 0.98 × 0.98 × 0.6 mm3, and the testing module is composed of discrete components and laboratory instruments. Significance. This work aims to show how it is possible to strike a balance between a small, reliable, and high-bit-rate data uplink between a neural implant and its proximal, wirelessly connected external unit. This optical telemetry module has the potential to be integrated into a significantly miniaturized system through an application-specific integrated circuit and can support up to 1000 channels of neural recordings, each sampled at 9 kSps with a 12-bit readout resolution.

Millimeter-Wave Dual-Band MIMO Channel Capacity Analysis Based on Climate Data: A Samsun Province Case Study

The analysis of multiple-input multiple-output (MIMO) channel capacity is important for developing and optimizing high-speed wireless communication systems that can meet the growing demand for data-intensive applications. This study aims to analyze the 4 × 4 MIMO channel capacity of outdoor urban and rural environments using the NYUSIM simulator. The channel models are designed for 28 GHz and 39 GHz frequencies for both line-of-sight (LOS) and non-line-of-sight (NLOS) conditions. Realistic channel models are simulated using annual climate data collected in Samsun province, Turkey in three different environments: urban microcell (UMi), urban macrocell (UMa), and rural macrocell (RMa) areas. According to the annual average channel capacity analysis, it is observed that there is a very small capacity difference between UMi and UMa areas at 28 GHz and 39 GHz frequencies in the LOS region, while the RMa area is found to have a very low capacity compared to the UMi and UMa areas. The channel capacity for RMa is found to be approximately eight times smaller than UMi and UMa. In the NLOS region, channel capacities decrease significantly (between 312 and 3953 times) compared to the LOS region, with the UMa area having the greatest capacity and the UMi area having the lowest capacity. Compared to the UMi channel capacity, the RMa channel capacity is 1.36 times higher for 28 GHz and 1.28 times higher for 39 GHz. When the monthly changes in channel capacity are examined, it is discovered that the amount of precipitation has the greatest impact on channel capacity, and the capacity decreases as the rain rate increases. The highest correlation between channel capacity and rain rate was −0.97 for RMa, with a 28 GHz frequency and LOS conditions. Additionally, it becomes clear that channel capacities increase in the summer months as the temperature rises and humidity and pressure fall.

Spectrum Situation Awareness for Future Railway IoT: Challenges, Opportunities and Key Technologies

The heterogeneous network environment in railway Internet of Things networking increases the complexity of network hierarchy "macro-small-micro" multilayer fusion of spectrum resources, and the fast mobility condition in the high-speed railway wireless communication exacerbates the correlation and dynamics of "time-space-frequency" multi-domain coupling of spectrum resources. This article fully considers the impact of high-speed mobile conditions and heterogeneous network environments, and reveals the underlying cause of the poor performance of wireless spectrum opportunistic access of high-speed railways caused by the lack of capabilities in the electromagnetic spectrum space cognition, and proposes our multi-domain / multi-granularity / high dynamic electromagnetic spectrum space cognitive theory based on spectrum situation suitable for future high-speed railways. The article specifies the feasibility, operability and effectiveness of of the spectral situation awareness theory in high-speed heterogeneous environments.

Image and Text Transmission using Li-Fi Technology

This research paper focuses on the use of LiFi (Light Fidelity) technology for the transmission of image and text data. LiFi technology is an emerging technology that uses visible light communication (VLC) for data transmission, providing a high-speed and secure wireless communication system. In this project, a LiFi system is developed using an LED (Light Emitting Diode) bulb and a photodiode receiver to transmit and receive data. The system is tested for its ability to transmit image and text data at a high speed and with minimal interference. The results show that LiFi technology can provide a viable alternative to traditional wireless communication systems for certain applications, such as indoor communication and data transfer, where security and high-speed data transfer are essential. Overall, this research demonstrates the potential of LiFi technology as a reliable and secure means of wireless data transmission

Highly Efficient and Multiband Metamaterial Microstrip-Based Radiating Structure Design Showing High Gain Performance for Wireless Communication Devices

High-speed wireless communication devices need antennas to operate at multiple frequencies with high gain. The need for such antennas is increasing day by day. The proposed metamaterial superstrate antenna gives a high gain and multiband performance, which is required in high-speed wireless communication devices. The designed antenna is also applicable for C- and X-band communication devices. The structure consists of a simple patch and multiple split-ring resonator metamaterials on the superstrate region. The performance optimization is achieved by adjusting the feed position, varying the height of the superstrate layer and changing the thickness of metamaterial rings. The proposed design is analyzed for 4 GHz to 12 GHz. The performance analysis regarding the reflection coefficient, directivity, gain and electric field is observed. FR4 is used as a dielectric material that makes the design low-cost. The proposed design represents a minimum reflection coefficient response of −49 dB, a bandwidth of 490 MHz, a maximum electric field of 1.29 × 104 v/m, good directivity and a broader radiation pattern. The comparison between the simulated and the measured results is incorporated in the manuscript. A comparison of the presented design with other articles is included to check the novelty of the design. The proposed method helps to target applications such as WiFi, Earth observation and microwave links.

RIS-Assisted Scheduling for High-Speed Railway Secure Communications

With the rapid development of high-speed railway systems and railway wireless communication, the application of ultra-wideband millimeter wave band is an inevitable trend. However, the millimeter wave channel has large propagation loss and is easy to be blocked. Moreover, there are many problems such as eavesdropping between the base station (BS) and the train. As an emerging technology, reconfigurable intelligent surface (RIS) can achieve the effect of passive beamforming by controlling the propagation of the incident electromagnetic wave in the desired direction. We propose a RIS-assisted scheduling scheme for scheduling interrupt flows and improving quality of service (QoS). In the propsed scheme, an RIS is deployed between the BS and multiple mobile relays (MRs). By jointly optimizing the beamforming vector and the discrete phase shift of the RIS, the constructive interference between direct link signals and reflected link signals can be achieved, and the channel capacity of eavesdroppers is guaranteed to be within a controllable range. Finally, the purpose of maximizing the number of successfully scheduled flows and satisfying their QoS requirements can be practically realized. Extensive simulations demonstrate that the proposed scheme has superior performance regarding the number of completed flows and the system secrecy capacity over four baseline schemes in literature.

A Compact High-Isolation Four-Element MIMO Antenna with Asymptote-Shaped Structure

The demand for high-speed wireless communication systems has led to the development of ultrawide-band (UWB) antennas with a compact size and high performance. In this paper, we propose a novel four-port multiple-input multiple-output (MIMO) antenna with an asymptote-shaped structure that overcomes the limitations of existing designs for UWB applications. The antenna elements are placed orthogonally to each other for polarization diversity, and each element features a stepped rectangular patch with a tapered microstrip feedline. The unique structure of the antenna significantly reduces its dimensions to 42 × 42 mm2 (0.43λ×0.43λ@ 3.09GHz), making it highly desirable for use in small wireless devices. To further enhance the antenna's performance, we use two parasitic tapes on the ground plane at the back as decoupling structures between adjacent elements. The tapes are designed in a windmill shape and a rotating extended cross shape, respectively, to further improve the isolation. We fabricated and measured the proposed antenna design on a single-layer substrate (FR4) with a dielectric constant of 4.4 and a thickness of 1 mm. The measured results show that the impedance bandwidth of the antenna is 3.09-12 GHz, with an isolation of -16.4 dB, an envelope correlation coefficient (ECC) of 0.02, a diversity gain (DG) of 9.991 dB, an average total effective reflection coefficient (TARC) of -20 dB, an overall group delay value less than 1.4 ns, and a peak gain of 5.1 dBi. Although there may be some antennas that have better performance in one or two specific aspects, our proposed antenna has an excellent trade-off among all the antenna characteristics including bandwidth, size, and isolation. The proposed antenna also exhibits good quasi-omnidirectional radiation properties, making it well-suited for a range of emerging UWB-MIMO communication systems, particularly in small wireless devices. In summary, the compact size and ultrawide-band capabilities of the proposed MIMO antenna design, coupled with its improved performance compared to other recent UWB-MIMO designs, make it a promising candidate for 5G and next-generation wireless communication systems.

Persistent Homology Approach for Human Presence Detection from 60 GHz OTFS Transmissions.

Orthogonal Time Frequency Space (OTFS) is a new, promising modulation waveform candidate for the next-generation integrated sensing and communication (ISaC) systems, providing environment-awareness capabilities together with high-speed wireless data communications. This paper presents the original results of OTFS-based person monitoring measurements in the 60 GHz millimeter-wave frequency band under realistic conditions, without the assumption of an integer ratio between the actual delays and Doppler shifts of the reflected components and the corresponding resolution of the OTFS grid. As the main contribution of the paper, we propose the use of the persistent homology technique as a method for processing gathered delay-Doppler responses. We highlight the advantages of the persistent homology approach over the standard constant false alarm rate target detector for selected scenarios.

Evolution of Short-Range Optical Wireless Communications

The optical wireless communication (OWC) technology explores the broad unregulated optical spectrum to provide high-speed wireless communications, and the visible, ultraviolet and near-infrared wavelength ranges all have been investigated. Compared with the conventional radio frequency (RF) band, the spectrum in OWC systems is much less congested and the interference is much lower. The OWC technology also provides enhanced physical layer security due to the natural confinement of optical beams that makes it difficult to intercept the transmitted signal. Hence, the OWC technology has been widely studied and considered as a promising candidate in future beyond-5G communications. The OWC technology has been considered for both long-range and short-range applications, and in this paper we will introduce the fundamentals and recent developments of short-range OWC systems. In particular, we will focus on the key short-range OWC applications in indoor personal or local area communications, underwater wireless communications, wireless data center networks, and vehicular communications. We will also introduce some recent widely studied advanced techniques to boost the performance of short-range OWC systems, including the spatial domain diversity, multiplexing and modulation principles to improve the system robustness and data rate, and the machine learning algorithms and hardware accelerators to suppress both linear and nonlinear effects to improve OWC signal quality and bit-error-rate performance.

Multi-Input Physical Layer Network Coding in Two-Dimensional Wireless Multihop Networks

This paper proposes multi-input physical layer network coding (multi-input PLNC) for high speed wireless communication in two-dimensional wireless multihop networks. In the proposed PLNC, all the terminals send their packets simultaneously for the neighboring relays to maximize the network throughput in the first slot, and all the relays also do the same to the neighboring terminals in the second slot. Those simultaneous signal transmissions cause multiple signals to be received at the relays and the terminals. Signal reception in the multi-input PLNC uses multichannel filtering to mitigate the difficulties caused by the multiple signal reception, which enables the two-input PLNC to be applied. In addition, a non-linear precoding is proposed to reduce the computational complexity of the signal detection at the relays and the terminals. The proposed multi-input PLNC makes all the terminals exchange their packets with the neighboring terminals in only two time slots. The performance of the proposed multi-input PLNC is confirmed by computer simulation. The proposed multi-input physical layer network coding achieves much higher network throughput than conventional techniques in a two-dimensional multihop wireless network with 7 terminals. The proposed multi-input physical layer network coding attains superior transmission performance in wireless hexagonal multihop networks, as long as more than 6 antennas are placed on the terminals and the relays.

Design of an axial mode helical antenna with buffer layer for underwater applications

<span lang="EN-US">Recently, there is an increasing demand for high-speed wireless communication network for short-range underwater communication. From previous research, most underwater antennas produced omnidirectional radiation pattern which has lower antenna gain. There are a few considerations that need to be taken if the antenna is designed to operate in water environment. This paper discusses the electromagnetic properties which affect the underwater antenna design. Physical properties such as electrical permittivity and conductivity of water contribute significant effect to the size of the antenna as it influences the behavior of electromagnetic signal that propagates in water. In this study, an axial mode helical antenna with waterproof container is presented which operates at 433 MHz. The axial mode helical antenna has circular polarization and is suitable to support wireless application which is surrounded by some obstruction. The proposed antenna produces a bidirectional radiation pattern by placing it into a waterproof casing. Good agreement between the simulation and measurement results validates the concept. However, a little discrepancy between the simulated and measured results may be attributed to the noise originated from the equipment and the environment.</span>

Liquid Crystal-Tuned Planar Optics in Terahertz Range

Recently, terahertz waves of higher frequencies compared to microwave and radio frequency have shown great potential in radar detection and high-speed wireless communication. To spatially control the wavefront of terahertz beams, various novel components, such as terahertz filters, polarization converters and lenses, have been investigated. Metamaterials and metasurfaces have become the most promising technique for the free manipulation of terahertz waves. Metadevices integrated with liquid crystals have been widely used in active terahertz devices. In this review, the birefringence of liquid crystals in the terahertz band and terahertz devices based on liquid crystals are summarized. By integrating liquid crystals with plasmonic metamaterials, the functions become dynamically adjustable and are reconstructed. Utilizing liquid crystals to change the resonance of metamaterials, tunable filters, absorbers, and programmable metasurfaces are realized. To solve the problem of low efficiency, terahertz wavefront shaping devices based on dielectric metasurfaces and liquid crystals, such as a variable deflection angle grating and zoom metalenses, are presented. Finally, we discuss and anticipate the future developments of liquid-crystal-integrated meta-devices, which will inspire broad applications in terahertz communication and imaging.

Fully-Integrated SPAD-Based Receiver With Nanosecond Dead Time for Optical Wireless Communication

This paper presents the design and characterization of a fully-integrated receiver based on single-photon avalanche diodes (SPADs) with nanosecond dead time for high-speed high-sensitivity optical wireless communication (OWC). The receiver consists of a 4x4 SPAD array that is based on a p-well/deep n-well (DNW) structure, and each SPAD is integrated with a tunable front-end circuit to perform quench and reset. In addition, an OR tree is designed to combine the 16 channels of output from the front-end circuits to generate a single data stream for signal processing, and an output buffer is implemented as the interface to drive 50-Ω loading for testing purpose. Fabricated in a standard 180 nm CMOS process, the receiver achieves a minimum dead time of about 2.5 ns. Bit error rate (BER) measurement of the implemented receiver indicates a sensitivity of −31.6 dBm at 100 Mb/s for a BER of 2 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> and a wavelength of 520 nm, where on-off keying (OOK) modulation and a 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> -1 pseudorandom binary sequence (PRBS-15) are employed. To recover the transmitted data stream from the received signal, a signal processing flow specific for SPAD-based receivers is proposed and implemented.