Search

Wireless communication in the sub-terahertz and terahertz (THz) bands (broadly from 100 GHz to 10 THz) is a critical building block of the future generations of telecommunication and networking due to the large available bandwidth at these frequencies and the opportunities it brings for ultra-broadband communication and sensing systems. Alongside the high data rates offered by this band, the huge bandwidth can be shared more generously across multiple users with hopes of reducing network congestion. With the recent improvements being made on the electronics side such as high-speed data converters and high-frequency oscillators, several testing platforms for experimental THz communication have been recently developed. However, these are mostly device technology demonstrators, channel sounders, or physical-layer testbeds, which do not support real-time digital signal processing (DSP). Such platforms have supported the large body of THz research focused on studying the channel or developing physical layer solutions. However, the lack of real-time DSP capabilities prevents the testing of upper networking protocols, on which the research community is only now starting to focus. While real-time networking platforms, namely, software-defined radio (SDR) platforms, developed for lower frequency systems could be utilized, their very low bandwidth misses the point of moving to the sub-THz and THz bands. To fill the gap, in this paper, we design an SDR platform able to process multi-GHz of baseband bandwidth in real-time by leveraging the state of the art in radio-frequency systems on chip (RFSoC), a custom frequency-multiplexing analog network and a multi-phase implementation of an orthogonal frequency-division modulation (OFDM) physical layer. As an instantiation of the platform, we demonstrate a real-time link at 135 GHz with 8 GHz of bandwidth supporting a bit-rate of 33 Gbps when frequency-multiplexing four 2-GHz-wide channels, each with 64-sub-carrier OFDM. Finally, we identify immediate next steps and cross-layer challenges foreseen when implementing wireless communication and sensing systems at frequencies above 100 GHz.

The choice of modulation techniques for next-generation communications in the sub-terahertz and terahertz bands remains largely unresolved. A variety of traditional and new schemes show promise, but the question remains open on the illustrative comparison process for realistic terahertz systems. While there are some preliminary studies in this area, we emphasize that the peculiarities of terahertz hardware necessitate a scheme that (i) is resistant to system-wide phase noise (PN) and (ii) has a low peak-to-average power ratio (PAPR). Therefore, in this article, we present a comprehensive methodology to carefully model and jointly study the impacts of PN and PAPR on the performance of candidate modulations for terahertz links. We first deliver a mathematical model for sub-terahertz/terahertz phase noise impairments at 130 GHz, 225 GHz, and 1.02 THz based on measurements from actual terahertz hardware. We then introduce the PAPR penalty – an approach for fair comparison of bit error rate (BER) and spectral efficiency (SE) of modulation schemes with different PAPRs. We finally combine these two effects to comprehensively study the characteristics of single and multi-carrier modulation schemes for terahertz communications. Our study reveals that analyzing PAPR and PN jointly is paramount: accounting for only one leads to major deviations in the numerical results and misleading conclusions on best modulation choice(s). The delivered framework and evaluation should facilitate further studies, leading to a well-motivated selection of the most suitable modulation scheme(s) for prospective sub-terahertz and terahertz radio systems.

Graphene-based Field-Effect Transistors (FETs) integrated with microstrip patch antennas offer a promising approach for terahertz signal radiation. In this study, a dual-stage simulation methodology is employed to comprehensively investigate the device’s performance. The initial stage, executed in MATLAB, delves into charge transport dynamics within a FET under asymmetric boundary conditions, employing hydrodynamic equations for electron transport in the graphene channel. Electromagnetic field interactions are modeled via Finite-Difference Time-Domain (FDTD) techniques. The second stage, conducted in COMSOL Multiphysics, focuses on the microstrip patch antenna’s radiative characteristics. Notably, analysis of the S11 curve reveals minimal reflections at the FET’s resonant frequency of 1.34672 THz, indicating efficient impedance matching. Examination of the radiation pattern demonstrates the antenna’s favorable directional properties. This research underscores the potential of graphene-based FETs for terahertz applications, offering tunable impedance matching and high radiation efficiency for future terahertz devices.

The miniaturization of transceivers and antennas is enabling the development of Wireless Networks-on-Chip (WNoC), in which chip-scale communication is utilized to increase the computing performance of multi-core/multi-chip architectures. Although the potential benefits of the WNoC paradigm have been studied in depth, its practicality remains unclear due to the lack of a proper characterization of the wireless channel at the chip scale and across the spectrum, among others. In this paper, the state of the art in wave propagation and channel modeling for chip-scale communication is surveyed. First, the peculiarities of WNoC, including the design drivers, architecture, environment, and on-chip electromagnetics are reviewed. After a brief description of the different methods to characterize wave propagation at chip-scales, a comprehensive discussion covering the different works at millimeter-wave (mmWave), Terahertz (THz) and optical frequencies is provided. Finally, the major challenges in the characterization of the WNoC channel and potential solutions to address them are discussed, providing a roadmap for the foundations of practical WNoCs.

In this paper, metallic plasmonic nano-antennas are modeled and analyzed for wireless optical communication. More specifically, a unified mathematical framework is developed to investigate the performance in transmission and reception of metallic nano-dipole antennas. This framework takes into account the metal properties, i.e., its dynamic complex conductivity and permittivity; the propagation properties of surface plasmon polariton waves on the nano-antenna, i.e., their confinement factor and propagation length; and the antenna geometry, i.e., length and radius. The generated plasmonic current in reception and the total radiated power and efficiency in transmission are analytically derived by utilizing the framework. In addition to numerical results, the analytical models are validated by means of simulations with COMSOL Multi-physics. The developed framework will guide the design and development of novel nano-antennas suited for wireless optical communication.

Nanotechnology is enabling the development of devices on a scale ranging from one to a few hundred nanometers. At this scale, novel nanomaterials and nanoparticles show new properties and behaviors not observed at the microscopic level. In the future, networks of nano-devices will be a key component of almost every field of our society, with applications in biomedicine, environmental protection, entertainment, homeland security, and beyond. In order to enable nano-devices to communicate with each other, many fundamental challenges need to be addressed. As the functional devices shrink into nano-scale, design, fabrication and control of the systems impose novel design principles which greatly differ from that of the macro. Electromagnetic (EM) communication in the Terahertz (THz) band (0.1–10 THz) enabled by graphene-based plasmonic nano-transceivers and nano-antennas has been suggested as one of the possible approaches for communication among these devices. This Special Section in IEEE Access is dedicated to all aspects of nanoscale communications including transceiver and antenna design in addition to communication and networking solutions, as well as novel paradigm, e.g., Hybrid Molecular/EM communication systems.

Nanonetworks consist of nano-sized communicating devices which are able to perform simple tasks at the nanoscale. Nanonetworks are the enabling technology for unique applications, including intra-body health-monitoring and drug delivery systems. In this paper, metallic plasmonic nano-antennas for wireless optical communication in intra-body nanonetworks are modeled and analyzed. More specifically, a unified mathematical framework is developed to investigate the performance in reception of gold-based nano-dipole antennas. This framework takes into account the metal properties, i.e., its dynamic complex conductivity and permittivity; the propagation properties of Surface Plasmon Polariton waves on the nano-antenna, i.e., their confinement factor and propagation length; the antenna geometry, i.e., length and radius, and the antenna fundamental resonance frequency, and it can be utilized to obtain the plasmonic currents on the nano-antenna generated by an incident EM filed. In addition to numerical results, the analytical models are validated by means of simulations with COMSOL Multi-physics. The developed framework will guide the design and development of novel nano-antennas suited for wireless optical communication in intra-body nanonetworks.

Nano-communication-based devices have the potential to play a vital role in future healthcare technologies by improving the quality of human life. Its application in medical diagnostics and treatment has a great potential, because of its ability to access small and delicate body sites noninvasively, where conventional medical devices fall short. In this paper, the state of the art in this field is presented to provide a comprehensive understanding of current models, considering various communication paradigms, antenna design issues, radio channel models based on numerical and experimental analysis and network, and system models for such networks. Finally, open research areas are identified for the future directions within the field.