Nano Communication Networks最新文献

This paper proposes a graphene patch antenna for dual-band operation while maintaining a low profile. The antenna consists of the metasurface-based 4 x 4 AMC configuration and the square graphene patch driven through the aperture coupling. The fundamental TM₁₀ mode of graphene patch excites the first resonance frequency, while the TM₁₀ and antiphase TM₂₀ modes of metasurface simultaneously excite the second wide frequency band. The first resonance frequency excited by the graphene patch can be reconfigured by varying the external DC bias voltage on the graphene patch. An equivalent circuit of antenna using lumped elements has also been proposed using a vector fitting algorithm. The proposed antenna with a profile height of $0.12{\lambda }_0$ (where ${\lambda }_0$ is free space wavelength) at a center frequency of 1.14 THz achieves the gain from 7.06 dB to 10.4 dB in the first band and an average gain of 10 dB in the second band.

This paper presents a graphene-based frequency tunable isolation enhancement mechanism for terahertz (THz) MIMO antenna. The presented simple and compact decoupling method could also be employed for any THz device. An isolation enhancement of about 30.41 dB has been achieved at the frequency of operation. The decoupling structure has the ability to suppress mutual coupling caused by any radiation mode of the MIMO element. The change of 0.2 eV (i.e., from 0.5 to 0.7 eV) in chemical potential (${\mu }_c$) provides a frequency tunability of about one THz in the transmission coefficient of the decoupling structure. The proposed decoupling technique is applied to the slot ring-based dual-polarized MIMO/diversity antenna. The diversity antenna provides a bandwidth (BW) of 0.83 THz (5.68–6.51 THz) with isolation of 47.56 dB at resonant frequency (6 THz). The gain and efficiency of the proposed diversity antenna at 6 THz are better than 3.99 dBi and 90.17%, respectively. The envelope correlation coefficient (ECC) calculated from far-field and diversity gain (DG) are 4.818 × 10 ${}^{-7}$ and 10, respectively. Total active reflection coefficient (TARC) is found to be less than -10 dB for different values of input feeding phase $\theta$ and the mean effective gain ratio (${\text{MEG}}_i$/${\text{MEG}}_j$) is close to one, which confirms the antenna’s applicability for diversity application in multipath rich wireless channels.

Molecular communication (MC) is a recent novel communication paradigm, which could enable revolutionary applications in the fields of medicine, military, and environment. Inspired by nature, MC uses molecules as information carriers to transmit and receive data. Concentration-encoded molecular communication (CEMC) is an information encoding approach, where the information is encoded in the concentration of the transmitted molecules. In this paper, we propose a machine learning (ML)-based CEMC system. In particular, we propose a modulation scheme named concentration position-shift keying (CPSK), which encodes information as the position of the transmitted molecular concentration. After passing through a diffusion-based channel, the molecules are captured via a ligand–receptor binding process (LRBP) at the nanoreceiver. Then, a ML-based approach is employed to decode the data bits. From numerical simulations, it has been shown that increasing the transmission time and using 4-ary CPSK would enhance the communication performance of the proposed ML-based CEMC system. In addition, we found that the ML receiver mitigates the bias effect and reduces inter-symbol interference (ISI) of the diffusion-based molecular channel. As a result, the proposed ML-based receiver shows better performance than the conventional maximum-likelihood (MLE) receiver.

The ever-increasing capacity demand (up to Tbps in the foreseeable future) in wireless connectivity can supposed be satisfied by terahertz communications in the band from 100 GHz to 10 THz. This has been studied over short channel distances in laboratories using higher order modulation formats (QPSK, QAM). However, only very few reports on the THz channel performance in outdoor adverse weathers conditions are available due to the involved experimental difficulties. In this article, we report the performance of terahertz channels in emulated rain by utilizing a broadband pulse source and a 16-QAM modulated data stream. We observe that, a not precisely known of raindrop size distribution can be a major source of uncertainty for theoretical precipitation of power attenuation and bit error rate (BER). We also find that the channel degradation in rain is mainly due to power attenuation.

Today, communication links and networks are essential in transmitting data and information. Moreover, information sharing in communication devices and networks has become necessary, routine, and unavoidable. Consequently, designing and manufacturing high-speed nano-scale devices with ultra-low power consumption is very important. Among the emerging paradigms in nanotechnologies, quantum-dot cellular automata (QCA) is very popular in communication sciences. In the present study, we optimize the design and implementation of a QCA crossbar switch and use it in transmitter and receiver circuits. Subsequently, a circuit-switched network in QCA technology is implemented using these devices. All the designed circuits are coplanar with the minimum number of cells, optimal area and latency, and low power consumptions, which employ standard QCA design rules and show superiority and advantages compared to the previous designs.

Quantum-dot cellular automata (QCA) is a new technology to replace CMOS technology in digital circuits. This replacement is necessary since further miniaturization of CMOS devices has posed serious challenges. In this paper, an optimized 1:2 demultiplexer (1:2 DEMUX) as a tree network switch is proposed. The tree network is examined, and the switches, which are the main components of the network, are used for routing. The proposed 1:2 DEMUX uses a rotated majority gate (RMG) based on QCA technology. According to the evaluation of the proposed 1:2 DEMUX circuit, 16 QCA cells are used with a total area and latency of 0.$02\mu m$² and 0.25 clock cycles, respectively. A comparison with the best reported similar designs shows 15.78% improvement in the complexity, cell area, and area usage of the proposed 1:2 DEMUX. Another parameter that plays a very important role in QCA circuits is energy consumption, which can be measured with QCAPro software. In the proposed DEMUX circuit, the values of energy dissipation for 0.5, 1, and 1.5 E${}_k$ are 16.75, 24.84, and 34.6 meV respectively. The proposed router is the first of its kind that uses QCA-based DEMUX. This router has 146 cells, and its total area and latency are equal to 0.$25\mu m$² and 0.75 clock cycles, respectively.

A tunable terahertz (THz) slotted monopole antenna is implemented with self-diplexing capability. The radiating arms of antenna are filled with the graphene strips. The variation in electrical parameters of graphene alters the surface current distribution in the radiating arms which results in tuning the antenna response through individual input ports. Antenna operates in frequency range 4.75–5.34 $THz$ and 5.57–6.76 $THz$ with the application of input at port-1 and 2, respectively which can further be tuned with the reported biasing schemes. The antenna structure utilizes the orthogonal radiating slots which provides high isolation more than 150 dB between the ports in compact antenna geometry. An electrical equivalent circuit is prepared to verify the antenna operation. In addition, antenna offers the peak gain 3.83 dBi at port-1 and 6.06 dBi at port-2 in the operating passband along with the efficiency of more than 80%. Antenna provides the compact geometry with tunable self-diplexing capability and can be suitable for future wireless applications requiring the simultaneous transmit and receive systems.

Quantum-dot cellular automata (QCA) is a domain coupling nano-technology that has drawn significant attention for less power consumption, area, and design overhead. It is able to achieve a high speed over the CMOS technology. Recently, the tendency to design reversible circuits has been expanding because of the reduction in energy dissipation. Hence, the QCA is a crucial candidate for reversible circuits in nano-technology. On the other hand, the addition operator is also considered one of the primary operations in digital and analog circuits due to its wide applications in digital signal processing and computer arithmetic operations. Accordingly, full-adders have become popular and extensively solve mathematical problems more efficiently and faster. They are one of the essential fundamental circuits in most digital processing circuits. Therefore, this article first suggests a novel reversible block called the RF-adder block. Then, an effective reversible adder design is proposed using the recommended reversible RF-adder block. The QCAPro and QCADesigner 2.0.3 tools were employed to assess the effectiveness of the suggested reversible full-adder. The outcomes of energy dissipation for the proposed circuit compared to the best previous structure at three different tunneling energy levels indicate a reduction in the power consumption by 45.55%, 38.82%, and 34.62%, respectively.

As the potential of molecular communication via diffusion (MCvD) systems at nano-scale communication increases, designing molecular schemes robust to the inevitable effects of molecular interference has become of vital importance. There are numerous molecular approaches in literature aiming to mitigate the effects of interference, namely inter-symbol interference. Moreover, for molecular multiple-input–multiple-output systems, interference among antennas, namely inter-link interference, becomes of significance. Inspired by the state-of-the-art performances of machine learning algorithms on making decisions, we propose a novel approach of a convolutional neural network (CNN)-based architecture. The proposed approach is for a uniquely-designed molecular multiple-input–single-output topology in order to alleviate the damaging effects of molecular interference. In this study, we compare the performance of the proposed network with that of an index modulation approach and a symbol-by-symbol maximum likelihood estimation and show that the proposed method yields better performance.