A method to determine the inductive and capacitive components of the series impedance and shunt admittance for configuring the equivalent circuit of a composite right/left-handed (CRLH) transmission line is proposed. This method uses Z matrices with multiple frequencies obtained via full-wave analysis of an actual CRLH transmission line unit cell structure. Results are presented for the application of the proposed approach to a CRLH microstrip line.
In this paper, a compact and broadband printed monopole antenna for circular polarization is proposed. The miniaturization is achieved by inserting a triangle notch to the rectangular patch. Moreover, the broadband circular polarization is achieved by designing the antenna asymmetrically to the microstrip line. The simulated and measured bandwidth of the 10 dB-return loss with a 3 dB-axial ratio is 33.3% (2.50 GHz–3.50 GHz) and 37.8% (2.55 GHz–3.74 GHz). The size of the antenna is 0.147λc2 (λc is a wavelength in free space at the center frequency).
The composite right/left-handed (CRLH) coaxial line (CL) is applied to the broadband choke structure. Because the choke structure uses an electromagnetic bandgap (EBG), broadband operation is realized. To obtain the wide bandwidth of the EBG, the CRLH CL is redesigned and applied to the choke structure. The proposed choke structure is attached to the coaxially fed monopole antenna, whose characteristics are simulated. The simulated results show that the proposed choke structure operates in broadband.
We propose a four-wave mixing (FWM) compensation scheme using artificial-neural-network (ANN)-based digital signal processing. A phase-locked multicarrier source was employed to assure the deterministic phase relation between the carriers. The ANN successfully compensated for not only self-phase modulation (SPM) and cross-phase modulation (XPM) but also the nonlinear waveform distortion caused by FWM in the phase-locked condition. We investigated the compensation performance using a transmission system involving 5-ch wavelength-division multiplexing (WDM) of 16QAM-signals by numerical simulations. The performance in terms of the error vector magnitude (EVM) was improved by more than 19% using the proposed compensation method.
In this paper, we propose traceroute-based target link flooding attack (TLFA) detection scheme by analyzing hop count to the destination. Since the destinations of the attacker’s traceroutes tend to be concentrated around a target link, classifying traceroutes by hop count can highlight attacker’s traceroute. Thus, the proposed scheme can detect the attack even if an attacker slowly executes traceroutes and the ratio of legitimate user’s traceroutes is high. By computer simulations, we show our scheme has more robustness compared with the conventional scheme.
The knowledge of characteristics of the influence of packet loss is important to design controllers and observers which can reduce this influence on wireless feedback control systems. This paper clarifies the characteristics of the influence of packet loss as a disturbance that causes a difference between transmitted information and used information at the received side. Through the analyses of the influence of packet loss on both controller and controlled object sides, we clarify the power spectrum density of the influence on the controller side is not constant. Numerical results show an well-known approach - H∞ controller, which can reduce the influence of white disturbances, can not reduce the influence of packet loss. Our analyses will be useful for good modeling of the influence of packet loss to design controllers and observers.
A coordinated radio-resource scheduler with an FPGA-based hardware accelerator is a key component for 5G mobile systems in NFV environments. This paper analyses the scheduling process and addresses ways to reduce the overhead of memory copy operation between a central unit and the accelerator. The experimental results show that the overhead is reduced to approximately 14% when the accelerator is connected with a central unit via PCIe with high-bandwidth memory copy technique. Moreover, they indicate that the accelerator tightly coupled with central units via the Ethernet is also a possible approach for coordinated scheduling among multiple central units. This will be advantageous in implementing future NFV-based mobile communications systems.
We investigated the effect of the size of an artificial neural network (ANN) on the performance when compensating for linear and nonlinear waveform distortion caused by chromatic dispersion (CD) and self-phase modulation (SPM). The results revealed that larger nonlinear waveform distortion requires more hidden-layer neurons, whereas the required number of input-layer neurons is decided by the amount of CD. The compensation performance of the ANN was evaluated by numerical simulation of 50-km standard single-mode fiber (SSMF) transmission of 16-ary quadrature amplitude modulation (16QAM) signals.
A high-gain three-dimensional (3D) printed W-band reflector Fresnel lens antenna based on acrylonitrile butadiene styrene (ABS) is proposed for practical solution to achieve a low-cost and a high-gain antenna for a millimeter-wave radar system. Firstly, a 250-mm-diameter thin reflector Fresnel lens antenna are designed at center frequency of 76.5 GHz, based on a thick conventional reflector lens antenna. Then, assuming fabrication using high dielectric-loss materials, such as ABS plastics, the antenna characteristics difference of the two types of antennas are discussed using finite-difference time-domain (FDTD) analysis. Finally, a reflector Fresnel lens antenna is fabricated using commercially available 3D printer with a low-cost ABS filament. The measured gain and the azimuth half-power beamwidth are 36.0 dBi and 1.1°, respectively. These results agree well with the FDTD analysis result of 37.2 dBi.