Pump phase-locking to fiber-transmitted quadrature phase-shift keying-phase-conjugated twin waves (QPSK-PCTWs) is experimentally demonstrated for the first time. First, we demonstrate pump phase-locking to 80-km fiber-transmitted 20-Gbit/s QPSK-PCTWs using a non-degenerate phase-sensitive optical amplifier (ND-PSA) repeater. Optical phase-locked loops assisted by sum-frequency and second-harmonic generation (SS-OPLL) enable pump phase-locking because optical parametric interaction between a signal and its phase-conjugated wave is observed at the ND-PSA output when the SS-OPLL is working. Then, the influence of optical noise on the SS-OPLL is investigated. The SS-OPLL is relatively robust for optical noise because the difference in the ND-PSA output signal quality was negligible for the cases of optical signal-to-noise ratios of 15 dB and 25 dB.
Physical-network-resource deployment to meet future traffic growth is a significant issue for network operators because it is related to the ground design of next generation networks. In this paper, we propose an effective heuristic decomposition method of physical-network-resource deployment considering the balance between the amount of additional network resources Q and operation-risk. We focus on decreasing the number of physical links with additional capacity Nu to reduce operation-risk. Numerical evaluations indicate that, with our method, pareto-optimal solutions between Q and Nu can be designed with a smaller Nu, more than 50% smaller, compared with a benchmark method that minimizes Q.
A novel lossy-forward (LF) cooperative communication scheme based on the decode-and-forward (DF) protocol allowing source-relay link errors is proposed recently. The LF relaying scheme always allows the relay to forward the decoded information to the destination even though it may contain errors. The knowledge of the correlation between received information sequences is exploited in the decoding process at the destination to improve the system performance. In this paper, we derive exact expressions of the outage probability upper bound for a two-way LF relay system over Rician fading channels with random K-factor. The K-factor follows empirical distributions derived from measurement data. It is found that the two-way relaying with LF is superior to that with DF scheme in terms of the outage performance.
This report investigates noise current distribution in the switching operation of a silicon carbide (SiC) power module for optimization of the layout and packaging design. The noise current distribution is measured via the intensity of the near-field magnetic field, and the measurement methodology visualizes the noise current distribution on a wiring plane in the power module. The effect of a direct-current-link (DC-link) snubber capacitor on suppressing the voltage overshoot and ringing oscillation is evaluated using the proposed noise current identification method.
In orthogonal frequency division multiplexing (OFDM) systems, the pilot signal is inserted to obtain the channel state information (CSI). The time frequency interferometry (TFI) method reduces the number of pilot signals by using the real and null signals and obtains the accurate CSI by averaging the two time windows. On the other hand, many averaging operations are necessary to obtain more accurate CSI. Before now, we have proposed the pilot signal based on the imaginary and null signals. By using these characteristics, in this letter, we propose the real and imaginary TFI pilot signals to obtain the CSI from the four time windows averaging for OFDM systems.
A new method of identifying a user’s mobile phone for user authentication is proposed. When the authentication server receives packets from the mobile phone, it is identified by the packet arrival time. The authentication in the server is based on the change in packet arrival time when the mobile phone receives a call to the user’s telephone number registered with the server. This paper describes how the transmission delay characteristics yield the identification data; the viability of the proposed method is verified for a wide variety of mobile phone wireless environments in which mobile phones are used.
We recently clarified that an isolated head as model does not approximate a whole body for numerically estimating the specific absorption rate (SAR) in the human eye exposed to E-polarized plane wave, even at high frequencies above 0.6 GHz. This letter describes the case of the human eye close to metallic spectacles. As a result, we find that the average SAR is more affected by the body than that of the model without the spectacles.
An active phased array antenna is capable of controlling not only the phase of each element but also the amplitude, and can therefore form a highly accurate beam. When an amplitude distribution range is wide, there occurs the problem of the power efficiency of an amplifier connected to each element decreasing. To operate the amplifier with high efficiency, it is necessary to limit an amplitude control range. This paper proposes a new pattern synthesis algorithm adapted to optimize the excitation amplitudes and phases of an APAA within a predetermined amplitude control range. The proposed method enables designing within the predetermined amplitude control range by introducing a mapping function representing the amplitude of a driven element, although the values of independent variables to be optimized using a conjugate gradient method are not limited. In addition, the proposed method does not require iterative calculation, and makes it possible to obtain the optimum excitation amplitudes and phases by only performing optimization design once. The proposed algorithm will be described while taking null formation by a linear array antenna as an example, and effectiveness will be examined by simulation.