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Advancement in miniaturization of electronics devices and nano sensors has led to sophistication of Internet of things (IoT) devices. The improved fabrication technology of recent time makes it feasible for nano sensors to be positioned within the human body, and the terahertz (THz) band is seen as compatible frequency band for in vivo applications within millimeter scale. This paper presents the investigative analysis for nano communication operating at the terahertz frequency band. Link quality and capacity of in vivo comm has been examined using pathloss model where the losses due to absorption and spreading are generalized along with additional permittivity for a considered human model, precisely for skin, water, plasma, RBCs, and whole blood in wireless body area network (WBAN). The variations in link quality matrices such as bit error rate (BER), signal to noise ratio (SNR) and channel capacity have been obtained as these parameters are affected by change in path loss. For the considered scenario, maximum path loss has been observed in plasma with least in the skin. This change in pathloss affects the other link parameters in similar manner. Therefore, the complete analysis of different body components to obtain SNR, BER, and channel capacity relaying on absorption loss plus spreading loss has been realized. The channel capacity is observed least in plasma, increasing of 2.5% in whole blood, 6.5% in water, 6.7% in RBCs, and maximum of 12.5% in skin. Similarly, the SNR is least in plasma, and maximum in skin. Whereas the BER has been noticed maximum in plasma, and least in skin. [ABSTRACT FROM AUTHOR]

This article presents a compact, planar, and circularly polarized array antenna operating in the W-band (84.5–110 GHz), with all its prototypes fabricated using a low-cost, traditional, microwave printed circuit board composed of Rogers RT/duroid 5880 (εr = 2.2, tanδ = 0.009). The final design that was fabricated and measured was a 4 × 4 array antenna having an overall size of 9 mm × 20 mm × 0.254 mm that used series feeding to reduce its sidelobes. Measurements of the 4 × 4 patch antenna array showed approximately 6.9% 3-dB axial ratio bandwidth along with 15.2 dBi maximum right-hand circularly polarized (RHCP) antenna gain at 100 GHz. The array antenna yielded RHCP radiation characterized by a low profile, low cross-polarization levels (<−25 dB), low sidelobe levels (≤−10 dB), and high radiation efficiency (>91%). Additionally, a two-port MIMO antenna system was investigated by considering side-by-side and front-tofront configurations, both of which achieved good isolation and considerable envelope correlation coefficient and diversity gain values. Therefore, the proposed series array and MIMO antennas can be reasonable candidates for 6G applications of the sub-THz band (100– 110 GHz) in ultra-high-speed wireless and satellite communication systems. [ABSTRACT FROM AUTHOR]

In a wireless communication system, a microstrip patch antenna is gaining importance as a most powerful technology trend and it is applicable for the development of low-cost, minimal-weight, low-profile and high-performance antenna. This paper presents the design and the analysis of 1 × 2, 1 × 4 and 2 × 8 rectangular microstrip patch antenna (RMPA) arrays based on the photonic crystals for improved gain performance and high radiation characteristics compared to ones that are designed based on the homogeneous substrate in the frequency range of 0.25 - 0.55 THz. The design of the proposed antenna arrays based on the photonic band gap (PBG) and the homogeneous substrate structures is made by using the designed single-element RMPA as the basic building element, and then, they were fed by the parallel feeding structure. The designed antenna arrays were simulated using CST Microwave Studio software and validated with the aid of Ansoft HFSS simulator. For high radiation characteristics, the proposed antenna arrays resonated around 0.35 THz which is a low loss frequency window in the terahertz band. The main results showed that the designed antenna arrays based on the PBG substrate structure outperform the antenna arrays based on the homogeneous substrate in terms of return loss, bandwidth, gain and directivity. The best directivity was achieved by the 2 × 8 RMPA array of 17.40 dBi, whereas the 1 × 4, 1 × 2 RMPA arrays and single-element RMPA achieved the directivity of 13.54 dBi, 9.87dBi and 7.76 dBi, respectively. Hence, the designed antenna arrays can be used for medical imaging, threat detection and wireless surveillance communication. [ABSTRACT FROM AUTHOR]

Terahertz (THz) metasurfaces have emerged as powerful tools to modulate the wavefronts of THz radiation fully. Smart designs and fabrication are essential for enhancing the flexibility and encryption security of THz metasurfaces. In addition to digital coding metasurfaces and microelectromechanical systems, one method to realize dynamic THz metasurfaces is to utilize an active material. In this paper, a dynamic THz metasurface, which is combined with the phase‐change material VO2 and can be thermally controlled to achieve optical encryption, is proposed. Based on the electromagnetically induced transparency effect and by arranging the antennas in advance according to a specific hologram, a secret image can be encoded into the metasurface. At room temperature, the transmitted light field is an irregular light spot with no useful information. If the temperature increases above the phase‐change temperature, the encrypted hologram can be reconstructed. Moreover, owing to the distinct characteristics of VO2, the phase‐change temperature required during decryption is not very high, and the entire process is reversible. It is expected that, in combination with updated processing technology, such metasurfaces can be practically applied to the next generation of optical encryption or optical anticounterfeiting in the future. [ABSTRACT FROM AUTHOR]

Channel state information in millimeter wave (mmWave) and terahertz (THz) communications systems is vital for various tasks ranging from planning the optimal locations of BSs to efficient beam tracking mechanisms to handover design. Due to the use of large-scale phased antenna arrays and high sensitivity to environmental geometry and materials, precise propagation models for these bands are obtained via ray-tracing modeling. However, the propagation conditions in mmWave/THz systems may theoretically change at very small distances, that is, 1 mm–1 μ m, which requires extreme computational effort for modeling. In this paper, we first will assess the effective correlation distances in mmWave/THz systems for different outdoor scenarios, user mobility patterns, and line-of-sight (LoS) and non-LoS (nLoS) conditions. As the metrics of interest, we utilize the angle of arrival/departure (AoA/AoD) and path loss of the first few strongest rays. Then, to reduce the computational efforts required for the ray-tracing procedure, we propose a methodology for the extrapolation and interpolation of these metrics based on the convolutional long short-term memory (ConvLSTM) model. The proposed methodology is based on a special representation of the channel state information in a form suitable for state-of-the-art video enhancement machine learning (ML) techniques, which allows for the use of their powerful prediction capabilities. To assess the prediction performance of the ConvLSTM model, we utilize precision and recall as the main metrics of interest. Our numerical results demonstrate that the channel state correlation in AoA/AoD parameters is preserved up until approximately 0.3–0.6 m, which is 300–600 times larger than the wavelength at 300 GHz. The use of a ConvLSTM model allows us to accurately predict AoA and AoD angles up to the 0.6 m distance with AoA being characterized by a higher mean squared error (MSE). Our results can be utilized to speed up ray-tracing simulations by selecting the grid step size, resulting in the desired trade-off between modeling accuracy and computational time. Additionally, it can also be utilized to improve beam tracking in mmWave/THz systems via a selection of the time step between beam realignment procedures. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Signal Processing is the property of Journal of Signal Processing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Due to their low energetic photons and lack of ionization damage, terahertz (THz) waves are recognized as suitable for various wireless innovative applications with high-speed data rates. This paper proposes the design and analysis of a microstrip patch antenna based on a dual-ply hexagonal split ring resonator (HSRR). The suggested antenna resonates at 1.9 THz and is suitable for recent advancements in wireless communication. Furthermore, the HSRR structure has been investigated for various spacing Rs values between the rings, and the optimized HSRR structure performance is compared with conventional antennae. The computer simulation technology studio suite was used to model the planned HSRR and to study the antenna properties. The optimized HSRR structure produces − 47.09 dB return loss with a voltage standing wave ratio of 1.008. The structure exhibits a gain of 8.649 dB and a directivity of 8.696 dB at 1.992 THz. THz light's capability to react differently with innocuous and threatening materials as a function of the THz band provides a highly flexible base for spectroscopic THz scanning and security checks. This suggested HSRR antenna is appropriate for all THz applications with high-speed data rates, such as wireless satellite communication, the biomedical detection of malignant tissue, THz imaging, and spectrometers. [ABSTRACT FROM AUTHOR]

Terahertz band gap is the range of frequency lying between the microwave band and the optical band, its range spectrum starts from 0.1 THz to 10 THz. This band provides unallocated wide bandwidth as well as very high-speed communication in the futuristic applications. This article presents a broadband microstrip 1 x 2 array antenna powered by hybrid coupler in terahertz band (around 2.45 THz). To reach this Broadband antenna, at first, a wideband 3 dB hybrid coupler is designed and optimized. After that, two basic elements of square shaped with slots are fed by the two output ports of the coupler. The results obtained reports that the suggested antenna offers – 10 dB wide bandwidth equals to 846 GHz (from 1.91 to 2.77 THz) with good impedance matching, maximum directivity equals to 8.86 dBi at the operating frequency 2.45 THz. Additionally, it offers the capability of beam steering which can be obtained by switching of the input ports of the coupler. Thus, the antenna can produce two beams at ±30°. The structure and simulation results of the proposed antenna have been done on Rogers RT/duroid 5880 substrate. The total size of the proposed microstrip array antenna is 110 x 112 x 1.56 μm³. Due to its capability of beam steering and broadband characteristic, the proposed antenna is a potential candidate for Terahertz band applications such as materials characterization in the THz band, medical imaging and future high-speed wireless communication. [ABSTRACT FROM AUTHOR]

Sixth generation (6G) wireless networks require very low latency and an ultra-high data rate, which have become the main challenges for future wireless communications. To effectively balance the requirements of 6G and the extreme shortage of capacity within the existing wireless networks, sensing-assisted communications in the terahertz (THz) band with unmanned aerial vehicles (UAVs) is proposed. In this scenario, the THz-UAV acts as an aerial base station to provide information on users and sensing signals and detect the THz channel to assist UAV communication. However, communication and sensing signals that use the same resources can cause interference with each other. Therefore, we research a cooperative method of co-existence between sensing and communication signals in the same frequency and time allocation to reduce the interference. We then formulate an optimization problem to minimize the total delay by jointly optimizing the UAV trajectory, frequency association, and transmission power of each user. The resulting problem is a non-convex and mixed integer optimization problem, which is challenging to solve. By resorting to the Lagrange multiplier and proximal policy optimization (PPO) method, we propose an overall alternating optimization algorithm to solve this problem in an iterative way. Specifically, given the UAV location and frequency, the sub-problem of the sensing and communication transmission powers is transformed into a convex problem, which is solved by the Lagrange multiplier method. Second, in each iteration, for given sensing and communication transmission powers, we relax the discrete variable to a continuous variable and use the PPO algorithm to tackle the sub-problem of joint optimization of the UAV location and frequency. The results show that the proposed algorithm reduces the delay and improves the transmission rate when compared with the conventional greedy algorithm. [ABSTRACT FROM AUTHOR]

Two promising technologies cosidered for the Beyond 5G networks are the terahertz and nano-technologies. Besides other possible application areas they hold the commitment to numerous new nano-scale solutions in the biomedical field. Nano-technology, as the name implies, examines the construction and design of nano-sized materials. These two interconnected emerging technologies have the potential to find application in quite many areas, one of the most importan being healthcare. This overview paper discusses the specifics of these technologies, their most important characteristics and introduces some of the trends for their application in the healthcare sector. In the first section terahertz frequency radio waves and their specific properties depending on the surrounding environment are discussed, followed by an introduction to nano-scale communications. Terahertz waves mandate the use of nano-scale antennas, which in turn brings us to the concept of nano-scale nodes. Nano-scale nodes are units that can perform the most basic functions of nano-machines and inter-nano-machine communications, which allow distributed nano-machines to perform more complex functions. Beyond 5G the development of these nano-communications is expected to lead to the emergence of new complex network systems. In the second part of this paper the paradigms of the Internet of Nano Things, molecular commnications and the Internet of Bio-Nano Things are discussed followed by details on their integration in healthcare related applications. The main goal of the article is to provide an introduction to these intriguing issues discussing advanced nano-technology enablers for Beyond 5G networks such as terahertz and molecular communications, nano-communications between nano-machines and the Internet of Bio-Nano-Things in light of health related applications. [ABSTRACT FROM AUTHOR]

In this paper, the authors have emphasized on the perspectives of the Terahertz channel modeling in Internet of multimedia nano things (IoMNT) networks. A modulation technique targeting body-centric network is discussed. An analogy of a real Terahertz antenna is developed within a terahertz multi-layer modelling channel for a human skin tissue. As a result, the investigation of how signals at THz frequency band interact and transmit within the skin biomaterial. The human skin model used to collect data was selected to have four layers: epidermis, dermis, blood, and hypodermis, with the depth of the layers varying between normal human body values. It is revealed from the literature that the frequency and content have a substantial impact on path failure. The estimated path loss could thus differ considerably, but for a human skin model with depths of 0.21 mm, 1.23 mm, 1.38 mm, and 3.76 mm, the frequencies of 0.5-1.5 THz at the end distance resulted in a path loss estimated about 250-350 dB. [ABSTRACT FROM AUTHOR]

A novel methodology to perform mode conversion from rectangular fundamental TE10 mode to circular TE $_{n1}$ ($n $ = 2, 3, $4, \ldots $)/TE $_{0p}$ ($p $ = 1, 2, $3, \ldots $)/TE $_{1q} (q $ = 2, 3, $4, \ldots $) modes with similar topologies is presented in this article. The mode converter consists of two sections: a novel H-plane T-junction-based rectangular TE $_{m0}$ ($m $ = 2, 3, $4, \ldots $) mode launcher and a rectangular TE $_{m0}$ -circular TE $_{n1}$ /TE $_{0p}$ /TE $_{1q}$ mode converter. This kind of mode converter possesses good comprehensive performance and is highlighted by three primary advantages: 1) it is flexible to produce various circular TE modes and rectangular TE $_{m\mathrm {0}}$ modes; 2) the mode converter has a relatively simple and easy-to-fabricate geometry, making it especially suitable for the terahertz-band operation; and 3) it possesses a high mode conversion efficiency over a wide bandwidth, which is adequate to satisfy most of the application requirements. The analysis of mode conversion principle, numerical simulations, microfabrication, and experimental measurement of two H-band (220–325 GHz) prototypes are described. Back-to-back measurement results exhibited good agreement with simulation predictions having considered the conductor loss. A 3-dB transmission bandwidth of 56.7 GHz (231.4–288.1 GHz)/42.1 GHz (244.0–286.1 GHz) was experimentally obtained for the ${\mathrm {TE}}^{\square}_{10}-{\mathrm {TE}}_{01}^{\circ}/{\mathrm {TE}}_{31}^{\circ}$ mode converter. [ABSTRACT FROM AUTHOR]

This article presents the design, microfab- rication, and measurement of a terahertz band ${\mathrm {TE}}^{\Box }_{20}$ mode input–output coupling structure for dual-sheet-beam traveling-wave tubes (TWTs). The proposed coupling structure is based on an $E$ -plane Riblet slot coupler with one shorted port and a ${\mathrm {TE}}^{\Box }_{10}$ – ${\mathrm {TE}}^{\Box }_{20}$ mode converter. Compared to the previously reported high-order mode (HOM) coupling structures, the proposed structure possesses superior electrical and mechanical performance, including better reflection/transmission properties and relatively easy-to-fabricate configuration with features insensitive to fabrication tolerances. For verification, two $H$ -band (220–325 GHz) identical ${\mathrm {TE}}^{\Box }_{20}$ mode coupling structures joined back-to-back were manufactured and measured. Good agreement between the experimental results and the simulated responses is observed. The fabricated prototype of the coupling structure exhibits good electromagnetic (EM) performance over a bandwidth of 52.1 GHz (243.2–295.3 GHz) with a transmission coefficient better than −1.5 dB and a port reflection lower than −15.0 dB. [ABSTRACT FROM AUTHOR]

Terahertz (THz)-band communications have been envisioned as a key technology to support ultra-high-data-rate applications in 5G-beyond (or 6G) wireless networks. Compared to the microwave and mmWave bands, the main challenges with the THz band are in its i) large path loss hence limited network coverage and ii) visible-light-like propagation characteristics hence poor support of mobility in blockage-rich environments. This paper studies quantitatively the applicability of THz-band communications in blockage-rich mobile environments, focusing on a new network scenario called FlyTera. In FlyTera, a set of hotspots mounted on flying drones collaboratively provide data streaming services to ground users, in the microwave, mmWave and THz bands. We first provide a mathematical formulation of the FlyTera control problem, where the objective is to maximize the network spectral efficiency by jointly controlling the flight of the drone hotspots, their association to the ground users, and the spectrum bands used by the users. To solve the resulting problem, which is shown to be a mixed integer nonlinear nonconvex programming (MINLP) problem, we design distributed solution algorithms based on a combination of echo state learning and reinforcement learning. An extensive simulation campaign is then conducted with SimBAG, a newly developed Simulator of Broadband Aerial-Ground wireless networks. It is shown that no single spectrum band can meet the requirements of high data rate and wide coverage simultaneously. Moreover, from the network-level point of view, THz-band communications can significantly benefit from the mobility of the flying drones, and on average $4 - 6$ times higher (rather than lower) throughput can be achieved in mobile than in static environments. [ABSTRACT FROM AUTHOR]

The emerging Wireless Body Area Network (WBAN) has a great potential to strengthen health care sector, as it paves ways for the development of new services and applications. In making WBAN technically feasible, high Signal to Noise ratio (SNR) and low outage probability plays a vital role. In vivo communication is one where communication between living beings can be carried out wirelessly. It utilizes data gathered in real time for quick and accurate responses in emergency situations. To fully benefit from and further explore the potentiality of WBANs for realistic applications, it is critical to analyze the performance of in vivo WBAN communication over different frequency bands. Over the past many years, Medical Implant Communication System (MICS) band has extensively been used for implant medical applications and Terahertz (THz) band shows promising link capability to support increased data rates. In the proposed work, performance of an in vivo WBAN system, at MICS and Terahertz frequencies based upon IEEE 802.15.6 channel models (CM), CM1 and CM2 has been assessed. The effect of incorporating cooperative communication for in vivo WBAN is then presented to see how it enhances the network performance at both the bands. The impact on the system's SNR and outage probability is investigated for number of relays. The outage behavior of amplify and forward cooperative communication with multiple relays is investigated over a Rayleigh fading channel. Results show considerable increase in the system SNR and decrease in outage probability with increase in number of relays, which strongly indicates the possibility of incorporating cooperative communication to elevate the performance of in vivo WBAN at both MICS and terahertz frequencies. Further, nature inspired optimization is done to reduce the outage probability. Results show that the projected technique surpasses the non-optimized technique and ensures favorable results. The results achieved at THz band have also been compared to that obtained at MICS band and it is demonstrated that better performance can be achieved at THz band by incorporating cooperative communication in the network. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents reconfigurable frequency and polarization FSS-based with photoconductive switches in a single and dual-band operation for antenna applications at the terahertz band. The single band FSS unit-cell element exhibits frequency reconfigurability between 0.62 and 0.7 THz. It also converts the LP waves into CP over a frequency band ranging from 0.59 to 0.8 THz (30% 3-dB BW). The dual-band FSS unit-cell element exhibits frequency reconfigurability between (0.42 and 1.03 THz) when the switches are turned ON and (0.51 THz and 0.865 THz) when the switches are turned OFF. Moreover, it exhibits polarization conversion over two bands from 0.46 to 0.56 THz (20% 3-dB B.W) and from 0.82 to 0.91 THz (12% 3-dB B.W). The dual-band FSS unit-cell element is arranged in a 7 × 7 array and used as a reflector for two dipole antennas (A and B) operating at 0.82 THz and 0.5 THz, respectively. The same dual-band FSS-based surface enhances their gain to about 8.4 dBi and converts their polarization from LP to CP at 0.82 THz and 0.5 THz, respectively. [ABSTRACT FROM AUTHOR]

We propose and analyze a novel type of graphene-based device by using an improved anisotropic wave concept iterative process (WCIP) algorithm, this device can operate as a tunable electronic and magnetic sensor for Basal Cell Carcinoma (BCC) detection at the terahertz band. The proposed sensor consists of a planar filter, and a sample holder is located in the middle of it, to hold the normal skin and BCC samples. Through the proposed modeling approach of the biological samples, we can integrate the healthy and BCC tissues into this algorithm by redefining their boundary condition in terms of waves, this procedure was done without involving any volumetric discretization. At the beginning, we validate the effectiveness of the proposed anisotropic WCIP algorithm, an excellent agreement has been obtained, which demonstrate a high precision of the proposed algorithm. Finally, the numerical simulations demonstrate that the sensor has the ability to discover the healthy tissue with a high sensitivity of $6.9~\textit {THz/RIU}$ and Basal Cell Carcinoma with $11.2~\textit {THz/RIU}$. [ABSTRACT FROM AUTHOR]

A time‐varying multi‐ray channel model suitable for inter‐satellite link simulation and performance evaluation is proposed aiming at the characteristics of the space communication environment. This model analyzes the propagation process and multi‐dimensional characteristics of the terahertz (THz) waves between the satellite and the space station. The receiving environment of the space station is constantly changing due to the rotation of the station's solar panels with the sun and the relative motion between the station and the satellite. To predict critical multipath events for a specific communication configuration, the method of ray tracing, which is combined with the consistent orbiting theory and geometric orbital theory, is used to analyze the channel characteristics of different inter‐satellite links at the THz band (220 GHz). The research content includes the path loss model, the multipath statistics, the small scale fading and some other related channel characteristics. The space THz multi‐dimensional time domain, space domain, and frequency domain characteristics are obtained by studying the structural characteristics of the space station and space environment, the law of position change between the space station and the satellite, and the relative motion between the satellite and the space station. The study on the characteristics of the THz time‐varying channel provides a reference for the prediction and planning of THz wave propagation in future inter‐satellite links. Key Points: A time‐varying multi‐ray channel model is used to describe the multipath propagation and channel impulse response of the terahertz (THz) channelThe link scenario between the satellite and the space station is modeled and analyzedAccording to the simulation results, the key parameters of the space THz channel are analyzed, and the space‐time‐frequency characteristics of the channel are characterized [ABSTRACT FROM AUTHOR]

In this article, we investigate the wireless power transfer and energy-efficiency (EE) optimization problem for nano-empowered vehicular networks operating over the terahertz band. The nano-sensors in air can harvest energy from a power station and then can transmit the trace information to the micro-device under reconnaissance vehicular scenarios. Hence, by considering the properties of the terahertz band, we develop a long-term EE optimization problem. Furthermore, with the help of the equivalent transformation method, we converted the EE optimization problem into a series of energy-efficient resource allocation problems over the time slots. Each reformulated optimization problem becomes a mixed integer nonlinear programming (MINLP) over a time slot. Hence, to obtain the sub-optimal solution of the reformulated optimization problem, we developed a Quantum-behaved Particle swarm-based EE Optimization (QPEEO) algorithm. Furthermore, by exploiting the special structure of the reformulated problem, we propose an Improved Discrete Particle swarm-based EE Optimization (IDPEEO) algorithm. The proposed IDPEEO algorithm handles the problem’s constraints effectively, and greatly reduces the search space and the convergence time. Our simulation results validate the theoretical analysis of the proposed scheme. [ABSTRACT FROM AUTHOR]

This article presents a modeling and analysis of a tunable graphene-based sensor for breast tumor detection operating in the terahertz frequency range using the wave concept iterative process (WCIP) method. Through the novel implementation approach of the biological tissues in the WCIP method, we can integrate the normal and tumor of human breast tissues into this algorithm. At the beginning, the details of the algorithms of human breast tissue and graphene modeling in the WCIP method are presented. In order to verify the results obtained by the WCIP algorithm, we presented a comparative study with the CST simulator. Then, using the WCIP method, the numerical simulation results demonstrate the capability of the proposed sensor to detect the normal breast tissue with good sensitivity of 7.11 (THz/RIU) and breast tumor with a high sensitivity of 8.21 THz/RIU and large figure of merits of 17.51 and 20.23 RIU−1, respectively. Finally, the simplicity, efficiency and tunability are the benefits of the proposed sensor, which makes it suitable for breast tumor detection in the THz band. [ABSTRACT FROM AUTHOR]

In this paper, a metamaterial absorber based on graphene is proposed, designed and simulated numerically using multilayer structures. Before describing our work, the performance response of a three-layer structure is studied concerning one cylinder as a unit cell. Then, by varying the chemical potential of graphene (Fermi level of graphene) by applying external potential, the center frequency of this absorber can be adjusted. We will prove that by increasing the number of cylinders as fundamental elements in the unit cell, the bandwidth is also adjustable. Also, the center frequency can be affected by changing the dimensions of fundamental elements. Considering the above-mentioned items, the structure is investigated through increasing the graphene layers in which the absorber's frequency response is wider respected to previous structures and the center frequency is adjustable as a result of variations in the chemical potential of graphene layers. It is shown that the proposed perfect absorber's central frequency shift through graphene's voltage variation is about 0.15 THz which can be increased to 0.3 THz by changing radius. In some of the introduced absorbers, the maximum value of the absorption has reached over 95%. The most important advantage of the proposed structure, which is the main purpose of designing terahertz metamaterial absorbers, is its adjustable bandwidth and center frequency, and simple fabrication. [ABSTRACT FROM AUTHOR]

Two factors affecting the bandwidth of a reflectarray, the element phase error and the non-constant path delay phase error, have been investigated. A new solution is proposed to reduce the effect of the second factor. Using this method, without adding any particular complexity to the structure, the gain bandwidth of an array rises from 17 to 24%. This array is designed at the center frequency of 1.2 THz which can be used as a lens in the terahertz range. Since the dimensions of an array for such an application would be very large compared to the wavelength, the near-field to far-field transformation is used to accelerate the simulation time. [ABSTRACT FROM AUTHOR]

We design and simulate a tunable dual-band perfect absorber. This absorber is composed of a circular graphene layer with an ellipse cut out in the centre, separated by a dielectric layer in the middle and a gold mirror at the bottom. Results reveal that there exist two perfect absorption peaks in the terahertz band. The position of the absorption peak can be changed by adjusting the Fermi level and geometric parameters of the graphene pattern. Furthermore, the absorber is insensitive to the polarized incident light with a wide incident angle. Functionalities are achieved based on a simple and symmetrical single-layer graphene pattern, which can greatly reduce the manufacturing costs. The proposed absorber can be applied in the field of graphene-based photonic devices, such as detectors, sensors, and filters. [ABSTRACT FROM AUTHOR]

Over the last decade, short-range communications in the THz (Terahertz) band have been extensively studied as a technology-enabler for dense and ultra-dense wireless networks. The increasing demand for high data rates for wireless communication systems will inevitably lead to the extension of operation frequencies with larger bandwidths. THz range enables bandwidths on the order or hundreds of GHz. Thus, THz Band communication will alleviate the capacity limitations and spectrum scarcity of current wireless systems, and enable new classical networks and novel nanoscale networks applications. The main aim of this paper is to provide design guidelines for close proximity links with transmission capacity beyond 100 Gbit/s. We present the path loss, absorption loss, signal to noise ratio (SNR) and capacity of propagating electromagnetic waves at THz Band in different air medium types. The channel capacity and SNR properties are calculated according to transmit power estimation. In this paper, five air medium types are investigated which are average latitude—summer, high latitude—summer, average latitude—winter, high latitude—winter and tropics. [ABSTRACT FROM AUTHOR]

In this paper, we present an improved wave concept iterative process (WCIP) algorithm for the analysis of anisotropic graphene. Then, we use it to investigate a novel type of terahertz microstrip circulator based on graphene. In this algorithm, we propose a new technique for modeling of magnetized graphene layers, which consists of redefining the boundary conditions of graphene in terms of waves and integrating the surface conductivity without involving volumetric discretization. Numerical examples are presented to verify the efficiency of the proposed algorithm. The numerical simulations demonstrate that the performances of the circulator can be adjusted by applying an electric or magnetic field bias. [ABSTRACT FROM AUTHOR]

The scarcity of radio spectrum led regulators to consider new frequency bands including Terahertz frequencies between 0.275 and 1 THz, which is previously reserved only for passive services such as satellite telemetry and radio astronomy. One of the major advantages of Terahertz bands is the available bandwidth. For example, future generation cellular networks would be able support extreme throughputs via Terahertz backhaul links. But the medium that the electromagnetic waves propagate need to be analyzed by this way theoretical results will turn to practical and commercially attractive results. This work will give the channel characteristics of detailed analyzes of CO2, H2O, O2, USA model (high latitude, winter)—USA model (tropics) between 0.275 and 10 THz range. The developed model in this paper evaluates the total absorption loss, path loss, SNR and capacity properties. The water vapor–H2O (which is the biggest enemy of high frequencies) with all isotopes is analyzed in this paper. This paper also presents the theoretical estimations of absorption properties of CO2, H2O, O2, USA model (high latitude, winter)—USA model (tropics) at the THz frequency band from 0.275 to 10 THz. [ABSTRACT FROM AUTHOR]

Terahertz (THz) communications are envisioned as a key technology for 6G wireless systems, owing to an unprecedented promised multi-GHz bandwidth. While THz band suffers from huge propagation losses, large arrays of sub-millimeter wavelength antennas can be realized in ultra-massive multiple-input multiple-output (UM-MIMO) systems to enhance the received power and overcome the distance limitation. In this paper, a dynamic array-of-subarrays (DAoSA) hybrid precoding architecture is proposed to reduce the power consumption while meeting the data rate requirement in THz UM-MIMO systems. The connections between RF chains and subarrays are intelligently adjusted through a network of switches. First, to solve the intractable DAoSA hybrid precoding problem, element-by-element (EBE) and vectorization-based (VEC) algorithms are derived. Moreover, to determine the connections of the switches, near-optimal progressive stage-by-stage (PSBS), low-complexity alternating-selection (AS) and block-diagonal-search (BDS) algorithms are developed. Extensive simulation results show that both the EBE and VEC algorithms have higher spectral efficiency than existing hybrid precoding algorithms. Furthermore, the power consumption of the DAoSA architecture is substantially lessened, with PSBS, AS and BDS algorithms, respectively. The developed DAoSA architecture associated with proposed hybrid precoding and switch network design algorithms demonstrates a superior capability on balancing the spectral efficiency and power consumption. [ABSTRACT FROM AUTHOR]

This article presents an improved anisotropic wave concept iterative process (WCIP) algorithm for the analysis of a novel type of tunable graphene-based coupler at the terahertz band for different physical graphene parameters. Through the novel technique of implementation of the anisotropic boundary conditions in the WCIP method, we can integrate the anisotropic surface conductivity matrix into this algorithm without implying a volumetric discretization. Numerical examples are presented to verify the efficiency of the proposed algorithm. The numerical simulation results demonstrate that the performance of the coupler can be controlled by varying the chemical potential and the magnetic field, and a little change was obtained with the variation of the relaxation time and the temperature of graphene. [ABSTRACT FROM AUTHOR]

In this paper, an electromagnetic nano random communication system (EM-nRCS) has been proposed which ensures covert communication in the terahertz (THz) band. In the proposed system, the skewed alpha-stable noise shift keying method has been used to transmit random noise signals (RNSs) from the nano-transmitter (NT) by utilizing single-walled/carbon nanotubes-based true random number generator (SWCNTs-TRNG) and a graphene-based nano-antenna. A line-of-sight THz transparency window between 0.1 THz and 0.5 THz in the THz channel with spreading loss, molecular absorption loss and molecular absorption noise has been considered. Due to the broadband nature of the RNSs, the proposed EM-nRCS provides efficient transmission by overcoming the high path loss and intense channel noise arising from random fluctuations in the THz band. Non-coherent nano-receiver (NR) consisting of the modified extreme value method (MEVM) estimator has been proposed to extract the hidden binary information in the received RNSs. The bit error rate performance shows that the proposed EM-nRCS ensures high performance and covertness for future EM nanoscale communication devices. [ABSTRACT FROM AUTHOR]

A novel methodology of the power coupling from rectangular TE10 mode to TE20 mode for high-order overmoded multiple sheet electron beam devices is presented in this letter. The mode conversion was realized by an H-plane T-junction based mode converter with E-plane symmetric matching steps and the beam wave convergence/separation was realized by an overmoded Y-shaped coupler with a Bragg reflector. To verify the idea, two identical H-band (220-325 GHz) power coupling structures joined back-to-back were designed and manufactured by nano computer numerical control machining. The measured transmission and reflection coefficients were respectively ~ −2.0 dB and ~ −10.0 dB in the frequency range of 250.0-294.0 GHz. [ABSTRACT FROM AUTHOR]

The technique of mode conversion between rectangular TE10 and TEn0 (n = 2, 3, . . .) modes is studied in this article. The mode conversion was mainly realized by coupling apertures. To compensate for the junction discontinuity and, thus, enhance the performances, rectangular septa were introduced in the mode converters. Rectangular recesses were added to suppress the potential competing modes. As two examples, the design of rectangular TE20 and TE50 mode converters operating in the terahertz band is presented in this article. To verify the design, two identical rectangular TE20 mode converters joined back-to-back were manufactured by nanocomputer numerical control (CNC) machining and the performances of the converters were characterized by using a vector network analyzer. The measured transmission coefficients were in good agreement with the simulated ones and showed a good flatness response with a 3-dB bandwidth of ~70.7 GHz (220.0–290.7 GHz). The average measured value of S21 was about −2.0 dB and the in-band port reflection S11 was around −10.0 dB. [ABSTRACT FROM AUTHOR]

A novel frequency scanning-based direction-of-arrival (DOA) estimation scheme is proposed at terahertz (THz) band. The diffraction enhancement mechanism, focusing the superposition of the diffracted beam radiated from each element in one unit cell, is expanded to the 0.3 THz band. The frequency scanning reflector antenna (FSRA) operating at 235–330 GHz is proposed with high diffraction efficiency. Angular super-resolution algorithm is proposed based on the FSRA. Maximum likelihood (ML) method, traditionally used in array signal processing, is extended to the novel frequency scanning system based on the FSRA. The model of FSRA manifold vector is constructed. A FSRA operating on 0.3 THz frequency band was experimented, based on which the DOA estimation system is constructed. The resolution of the frequency scanning ML algorithm can be obtained on the level of half of the 3 dB beamwidth by the proof-of-principle experiments in 0.3 THz band. [ABSTRACT FROM AUTHOR]

Communication in Terahertz (THz) band is envisioned as a promising technology to meet the ever-growing data rate demand, and to enable new applications in both nano-scale and macro-scale wireless paradigms. In this study, we propose the first system-level design that is suitable for THz communication in macro-scale range with 100+ Gbps data rate. The design is based on the proposed terahertz pulse-level beam-switching with energy control (TRPLE), and motivated by the rise in Graphene-based electronics, which include not only compact generator and detector for pulse communication, but also the capability of beam scanning aided with nano-antenna-arrays. The very high path loss seen in THz wireless channel requires the use of narrow beam to reach longer transmission ranges. On the other hand, impulse radio that emits femtosecond-long pulses allows the beam direction to steer at pulse-level, rather than at packet-level. For TRPLE, we mathematically analyze the data rate for an arbitrary wireless link under the THz channel characteristics and the energy modulation scheme. Then, a novel optimization model is formulated to solve the parameters of the inter-pulse separation and the inter-symbol separation, in order to maximize the data rate while meeting the interference requirement. With the optimization, the data rate of 167 Gbps is shown achievable for most users in 20-m range. A MAC protocol framework is then presented to harness the benefits of the pulse separation optimization. [ABSTRACT FROM AUTHOR]

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It is commonly believed that weak light–matter interactions in low-mobility graphene dramatically limits tunability of graphene-based optoelectronic devices, such as tunable absorbers or switches. In this paper, we use a simple circuit model to understand absorption in graphene sheets. In particular, we show that light interacts weakly also with very high-mobility graphene sheets and propose systematic design means to overcome these problems. The results have allowed us to demonstrate in the terahertz band that perfect absorption with excellent electrical tunability can be achieved within a wide span of mobility values (from 200 to 20000 cm2V−1s−1) which almost covers the whole range of ever reported room-temperature mobilities. Remarkably, concentrating on the most practical low-mobility graphene devices, we exemplify our theory with two cases: frequency-tunable and switchable absorbers with near 100% modulation efficiencies. Our work provides systematic and instructive insights into the design of highly tunable absorbers, without restrictions on graphene mobility. The design strategy and the developed analytical model can, in principle, be generalized to other wavelength regions from microwave to mid-infrared range, and other 2-D materials such as transition metal dichalcogenides and black phosphorus. [ABSTRACT FROM AUTHOR]

In vivowireless nanosensor networks (iWNSNs) are paving the way toward transformative healthcare solutions. These networks are expected to enable a plethora of applications, including drug-delivery, bio-sensing, and health monitoring. With the development of miniature plasmonic signal sources, antennas, and detectors, wireless communications among intrabody nanodevices will expectedly be enabled in the terahertz (THz) frequency band (0.1–10 THz). Several propagation models were recently developed to analyze and assess the feasibility of intra-body electromagnetic (EM) nanoscale communication. The emphasis of these works has mainly been on understanding the propagation of EM signals through biological media, with limited focus on the intra-body noise sources and their impact on the system performance. In this paper, a stochastic noise model for iWNSNs is presented in which the individual noise sources that impact intra-body systems operating in the THz frequency band are analyzed. The overall noise contributions are composed of three distinctive constituents, namely, Johnson–Nyquist noise, black-body noise, and Doppler-shift-induced noise. The probability distribution of each noise component is derived, and a comprehensive analytical approach is developed to obtain the total noise power-spectral density. The model is further validated via 2-D particle simulations as the active transport motion of particles is conveyed in the presented framework. The developed models serve as the starting point for a rigorous end-to-end channel model that enables the proper estimation of data rate, channel capacity, and other key parameters, which are all factors of the noise environment. [ABSTRACT FROM AUTHOR]

Graphene plasmonic antennas possess two significant features that render them appealing for short-range wireless communications, notably, inherent tunability and miniaturization due to the unique frequency dispersion of graphene and its support for surface plasmon waves in the terahertz band. In this letter, dipole-like antennas using few-layer graphene are proposed to achieve a better trade-off between miniaturization and radiation efficiency than current monolayer graphene antennas. The characteristics of few-layer graphene antennas are evaluated and then compared with those of antennas based on monolayer graphene and graphene stacks, which could also provide such improvements. To this end, first, the propagation properties of one-dimensional and two-dimensional plasmonic waveguides based on the aforementioned graphene structures are obtained by transfer matrix theory and finite-element simulation, respectively. Second, the antennas are investigated as three-dimensional structures using a full-wave solver. Results show that the highest radiation efficiency among the compared designs is achieved with the few-layer graphene, while the highest miniaturization is obtained with the even mode of the graphene stack antenna. [ABSTRACT FROM AUTHOR]

Terahertz (THz) band communication is envisioned as a key technology to satisfy the increasing demand for ultrabroadband wireless systems, thanks to its ultrabroad bandwidth. Tailored for the unique properties of pulse-based communications in the THz band, two timing acquisition algorithms are proposed and analyzed thoroughly in this paper. First, a low-sampling-rate (LSR) synchronization algorithm is proposed, by extending the theory of sampling signals with finite rate of innovation in the communication context and exploiting the properties of the annihilating filter. The simulation results show that the timing accuracy at an order of ten picoseconds is achievable. In particular, the LSR algorithm has high performance with uniform sampling at $1/20$ of the Nyquist rate when the signal-to-noise ratio (SNR) is high (i.e., greater than 18 dB). Complementary to this, a maximum likelihood (ML) approach for timing acquisition is developed, which searches for the timing offsets by adopting a two-step acquisition procedure based on the ML criterion. The simulation results show that the ML-based algorithm is well suitable in the low SNR case with a half-reduced search space. For further evaluation, the error performance and the resulting bit-error-rate sensitivity to the timing errors in the LSR and the ML algorithms are both analytically and numerically studied. This paper provides very different and promising angles to efficiently and reliably solve the timing acquisition problem for pulse-based THz band wireless systems. [ABSTRACT FROM PUBLISHER]

The fifth generation wireless systems are expected to rely on a large number of small cells to massively offload traffic from the cellular and even from the wireless local area networks. To enable this functionality, mm-wave (EHF) and Terahertz (THF) bands are being actively explored. These bands are characterized by unique propagation properties compared with microwave systems. As a result, the interference structure in these systems could be principally different to what we observed so far at lower frequencies. In this paper, using the tools of stochastic geometry, we study the systems operating in the EHF/THF bands by explicitly capturing three phenomena inherent for these frequencies: 1) high directivity of the transmit and receive antennas; 2) molecular absorption; and 3) blocking of high-frequency radiation. We also define and compare two different antenna radiation pattern models. The metrics of interest are the mean interference and the signal-to-interference-plus-noise (SINR) ratio at the receiver. Our results reveal that: 1) for the same total emitted energy by a Poisson field of interferers, both the interference and SINR significantly increase when simultaneously both transmit and receive antennas are directive and 2) blocking has a profound impact on the interference and SINR creating much more favorable conditions for communications compared with no blocking case. [ABSTRACT FROM PUBLISHER]

A simply designed broadband meta-absorber (MA) that works in terahertz (THz) band is proposed and investigated. The reflector substrate of the MA is composed of nickel. The middle layer of this structure is made of dielectric Al2O3, which serves as a dielectric layer between the nickel and the metasurface layer. The metasurface layer comprises a graphene ring with a disk-like Au in the center. The wideband absorption mechanism benefits from the hybridized surface plasmonic modes caused by the coupling between the Au disk and the graphene ring. Besides, with the adhesion of the top Au metal disk, Fabry-Perot cavities formed by the top Au and the bottom metal produce the continuous cavity resonant modes also to enhance surface hybridization plasmons. Because the proposed broadband MA is symmetrical, it is insensitive to polarization and has a good bearing angle of 0 deg to 70 deg. The results of our study may inspire specific applications of wave modulation, including THz imaging, detecting, modulation, and sensing. [ABSTRACT FROM AUTHOR]

Nanotechnology is an emerging scientific area whose advances, among many others, have a positive direct impact on the miniaturization of electronics. This unique technology enables the possibility to design and build electronic components as well as complete devices (called nanomachines or nanodevices) at the nano scale. A nanodevice is expected to be an essential element able to operate in a nanonetwork, where a huge number of them would coordinate to acquire data, process the information gathered, and wirelessly transmit those data to end-points providing innovative services in many key scenarios, such as the human body or the environment. This paper is aimed at studying the feasibility of this type of device by carefully examining their main component parts, namely the nanoprocessor, nanomemory, nanoantenna, and nanogenerator. To this end, a thorough state-of-the-art review is conveyed to discuss, substantiate, and select the most suitable current technology (commercial or pre-commercial) for each component. Then, we further contribute by developing a complete conceptual nanodevice layout taking into consideration its ultra-small size (similar to a blood cell) and its very restricted capabilities (e.g., processing, memory storage, telecommunication, and energy management). The required resources as well as the power consumption are realistically estimated. [ABSTRACT FROM AUTHOR]

Nanonetworks consist of nano-sized communicating devices which are able to perform simple tasks at the nanoscale. The limited capabilities of individual nanomachines and the Terahertz (THz) band channel behavior lead to error-prone wireless links. In this paper, a cross-layer analysis of error-control strategies for nanonetworks in the THz band is presented. A mathematical framework is developed and used to analyze the tradeoffs between Bit Error Rate, Packet Error Rate, energy consumption and latency, for five different error-control strategies, namely, Automatic Repeat reQuest (ARQ), Forward Error Correction (FEC), two types of Error Prevention Codes (EPC) and a hybrid EPC. The cross-layer effects between the physical and the link layers as well as the impact of the nanomachine capabilities in both layers are taken into account. At the physical layer, nanomachines are considered to communicate by following a time-spread on-off keying modulation based on the transmission of femtosecond-long pulses. At the link layer, nanomachines are considered to access the channel in an uncoordinated fashion, by leveraging the possibility to interleave pulse-based transmissions from different nodes. Throughout the analysis, accurate path loss, noise and multi-user interference models, validated by means of electromagnetic simulation, are utilized. In addition, the energy consumption and latency introduced by a hardware implementation of each error control technique, as well as, the additional constraints imposed by the use of energy-harvesting mechanisms to power the nanomachines, are taken into account. The results show that, despite their simplicity, EPCs outperform traditional ARQ and FEC schemes, in terms of error correcting capabilities, which results in further energy savings and reduced latency. [ABSTRACT FROM AUTHOR]

Terahertz band communication is envisioned as a key technology to satisfy the increasing demand for ultra-high-speed wireless links. In this paper, a multi-wideband waveform design for the THz band is proposed, by exploiting the channel peculiarities including the distance-varying spectral windows, the delay spread and the temporal broadening effects. This scheme allows the dynamical variation of the rate and the transmit power on each sub-window and improves the distance. Moreover, the closed-form expressions of the signal-to-interference-plus-the-noise and bit-error-rate for the multi-wideband waveform are derived, by considering the inter-symbol and inter-band interferences. Then, an optimization framework is formulated to solve for the multi-wideband waveform design parameters of the transmit power and the number of frames, with the aim to maximize the communication distance while satisfying the rate and the transmit power constraints. Four sub-optimal solutions are proposed and compared. The results show that the SINR increases with the transmit power and the number of frames, at the cost of the power consumption and the rate decrease. With the transmit power of 10 dBm, the largest distance to support 10 Gbps for the multi-path propagation is 4 m, which is realized via the power allocation scheme to minimize the power/bit on each sub-window and is 10% improvement over the fixed scheme. However, for the directional transmission, this scheme under-exploits the transmit power severely. Instead, the allocation scheme that minimizes the number of frames outperforms the other three schemes. In terms of the maximum distance that achieves 30 Gbps, this scheme reaches 22.5 m. [ABSTRACT FROM AUTHOR]

Graphene-based plasmonic antennas could enable ultrabroadband communication among nanodevices in the Terahertz band (0.1-10 THz). Despite significant progress in graphene synthesis, the fabrication, manipulation, and placement of precisely formed graphene-based nanostructures still pose many practical challenges. In this letter, by comparing analytical solutions with numerical simulations, we show that lithographically defined graphene antennas, circumscribed by a focused ion beam (FIB), should behave as though they were electromagnetically isolated provided the width of the surrounding cut is comparable to the plasmonic wavelength. This result opens the door to practical and more advanced antenna designs. [ABSTRACT FROM PUBLISHER]

The radar cross‐section (RCS) measurements for cylinders with different surface roughness have performed in the terahertz bands. The terahertz radar system has 220 and 440 GHz carrier frequencies. It is a solid‐state system whose base band signal is generated by a phasor network analyser. The original recorded data are calibrated by the results of the smooth surface cylinder. These calibrated RCS results are compared with calculated results. The experiments suggested that targets with the rough surface will provide complicated scattering in terahertz. The results of this experiment can prove that the surface roughness of the target has a certain impact on RCS measurement results in the terahertz band. [ABSTRACT FROM AUTHOR]

Terahertz (0.06–10 THz) Band communication is envisioned as a key technology for satisfying the increasing demand for ultra-high-speed wireless links. In this paper, first, a unified multi-ray channel model in the THz Band is developed based on ray tracing techniques, which incorporates the propagation models for the line-of-sight, reflected, scattered, and diffracted paths. The developed theoretical model is validated with the experimental measurements (0.06–1 THz) from the literature. Then, using the developed propagation models, an in-depth analysis on the THz channel characteristics is carried out. In particular, the distance-varying and frequency-selective nature of the Terahertz channel is analyzed. Moreover, the coherence bandwidth and the significance of the delay spread are studied. Furthermore, the wideband channel capacity using flat and water-filling power allocation strategies is characterized. Additionally, the temporal broadening effects of the Terahertz channel are studied. Finally, distance-adaptive and multi-carrier transmissions are suggested to best benefit from the unique relationship between distance and bandwidth. The provided analysis lays out the foundation for reliable and efficient ultra-high-speed wireless communications in the (0.06–10) THz Band. [ABSTRACT FROM PUBLISHER]

Wireless NanoSensor Networks (WNSNs) will allow novel intelligent nanomaterial-based sensors, or nanosensors, to detect new types of events at the nanoscale in a distributed fashion over extended areas. Two main characteristics are expected to guide the design of WNSNs architectures and protocols, namely, their Terahertz Band wireless communication and their nanoscale energy harvesting process. In this paper, a routing framework for WNSNs is proposed to optimize the use of the harvested energy to guarantee the perpetual operation of the WNSN while, at the same time, increasing the overall network throughput. The proposed routing framework, which is based on a previously proposed medium access control protocol for the joint throughput and lifetime optimization in WNSNs, uses a hierarchical cluster-based architecture that offloads the network operation complexity from the individual nanosensors towards the cluster heads, or nano-controllers. This framework is based on the evaluation of the probability of saving energy through a multi-hop transmission, the tuning of the transmission power of each nanosensor for throughput and hop distance optimization, and the selection of the next hop nanosensor on the basis of their available energy and current load. The performance of this framework is also numerically evaluated in terms of energy, capacity, and delay, and compared to that of the single-hop communication for the same WNSN scenario. The results show how the energy per bit consumption and the achievable throughput can be jointly maximized by exploiting the peculiarities of this networking paradigm. [ABSTRACT FROM AUTHOR]