With the spread of smartphones, connections to the same access point have increased, but the method of evaluating the throughput characteristics of smartphones has not been established. Therefore, in this paper, we propose a method for evaluating the throughput characteristics of smartphones in an actual environment and evaluation index. Furthermore, as an example using the proposed method, we analyzed the throughput characteristics during single device and two devices competitive transmission and confirmed the effectiveness of the proposed method.
We succeeded in receiving the scattered signal of the GPS from point other than the specular reflection point using beam antenna. Characteristic echoes with Doppler frequency shift dependent on range were derived from the observed data with integration period of 40 seconds.
In order to explore possible asymmetry of nonlinear degradation near zero dispersion, nonlinear propagation of single-channel 10 Gbps signal at and near zero dispersion wavelength of dispersion-shifted optical fiber (DSF) is comprehensively investigated in terms of signal power and wavelength as well as transmission distance. Inherent nonlinear degradation near zero dispersion appears to be symmetric in terms of wavelength despite that Modulation Instability (MI) gain should vanish in normal dispersion with deviation from zero dispersion.
This paper proposes a compact backfire circular patch antenna (BCPA). The BCPA is fed from radiation aperture (patch side) by a coaxial cable, which acts as a support structure for a primary radiator of reflector antenna. A balun is used to improve the tilted radiation pattern produced by an unbalanced current on the feeding coaxial cable. We show that antenna characteristics of the BCPA is stable by using balun in both the simulation and measurement. The proposed BCPA is compact and easy to fabricate.
An electrically small metamaterial antenna is presented for ultra wide band applications. The proposed design provides a tunable frequency band with maximum efficiency and a bandwidth of approximately 7.7 GHz. Due to its compact size and simple structure, it can be employed in numerous wireless communication devices. The geometry of the antenna consists of a monopole ellipse radiator and a uniquely modified Electric LC (ELC) structure based on the concept of magnetic imaging at the boundary and provides dual frequency bands of 2.56∼3.68 GHz and 4.92∼6.82 GHz. The antenna is then fused with an Electromagnetic Band Gap (EBG) structure to increase impedance matching and provide an ultra wide band of 2.72 GHz to 10.46 GHz.
CAPTCHA is a kind of challenge response test, which is used to distinguish human users from malicious computer program such as bots. However, the attack technique called relay attack as a method to avoid the CAPTCHA has been devised. This attack relays the CAPTCHA challenges to remote human-solvers, let them to decode CAPTCHA challenges. We used delay time that is caused by communications needed in relay attack. Our new CAPTCHA uses this delay time between communications to prevent relay attacks. We constructed an experimental environment in which relay attack can be simulated, made a series of experiments in order to evaluate the performance of the proposed method.
In this letter, a wideband printed inverted-F antenna is proposed. A rectangular element is loaded at the feeding line perpendicularly. A new additional resonance is produced by the loaded rectangular element. Also, the wideband impedance matching and the stable gain can be achieved. The simulated and measured impedance bandwidths with the 10 dB-return loss of the proposed inverted-F antenna are approximately 96.1% (2.33 GHz–6.64 GHz) and 100.5% (2.39 GHz–7.22 GHz), respectively. The dimension of the fabricated antenna is 0.31λL × 0.20λL (λL is a wavelength at the lowest frequency in the frequency range with the 10 dB-return loss). The proposed antenna is small in size.
A reliable vehicle-to-vehicle (V2V) communication is essential for safe and highly automated driving system. The use of roadside relay stations (RSs) has been studied to assist the V2V communication and improve its reliability. However, its improvement is limited by possible packet congestion at RSs. In order to mitigate the packet congestion at RSs, in this letter, we propose a network coding based payload concatenation forwarding with a payload sorting and selection algorithm. Large-scale computer simulations confirm that the proposed scheme remarkably improves the reliability of V2V communications.