In wideband localization systems based on time of arrival (ToA), RF nonideality, such as carrier phase noise, IQ imbalance, phase and frequency offset, plays an important role for ToA estimation accuracy. In this work, Cramer-Rao lower bound (CRB) for ToA estimation in the presence of RF nonideality is first proposed as criterion for ToA estimator performance in practical ToA localization system. Evaluation of CRB with and without phase noise has been performed, especially closed form of CRB without phase noise has been derived. Theoretical and numerical results show that the ToA accuracy presents floor phenomenon in the presence of RF nonideality, and phase noise plays the dominant role. The effect of record length has also been evaluated.

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Asymmetry in a differential transmission line bend generates a large common mode, which leads to signal integrity issues. Herein two methods are proposed to improve the symmetry and reduce the common-mode at the line bend on a printed circuit board. Placing a guard trace near a narrowed inner signal line at the line bend results in a 15-dB reduction of the common mode. Alternatively, employing a stub connected to the inner signal at the bend section results in a more than 20-dB reduction.

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This paper discusses an optical signal noise ratio (OSNR) in passive optical network (PON) using a distributed Raman amplifier (DRA). We focus on asymmetric OSNR properties for up/downstream signals in 10-Gbps PON systems and study the dependency of OSNR on Raman pump power, splitting loss, and optical cable loss, theoretically. These calculations clarify the asymmetric OSNR properties mainly depend on the splitting loss. Calculated results are partly confirmed experimentally.

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DNS is one of important infrastructures on the Internet. If widely-known domain names are forged by DNS spoofing, a number of users have the potential to be forged and lead to phishing sites. In order to protect users, DNSSEC is an important technology. However, DNSSEC is not widely deployed now because the deployment has side effects in operator’s point of view. It is anxious for DNS operators to enable DNSSEC without creditable estimations of its impacts. In this paper, we propose DNSSEC simulator which can estimate the impacts. Our DNSSEC simulator can estimate and simulate the impacts using actual DNS queries, DNS topology, and actual DNS implementations. Moreover, there is no need of knowledge of DNS simulation. The simulator estimates the impacts easily by just providing DNS query log. The software can contribute the deployment of DNSSEC and achieving safe DNS world.

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Implementation of active queue management (AQM) at routers can prevent serious congestion of transmission control protocol (TCP) flows. We previously proposed a disturbance observer (DOB)-based AQM controller to cope with modeling errors of network systems. However, the robustness of the controller against parameter fluctuations, e.g., the number of TCP connections and round-trip time (RTT) delay between terminal devices, has not been investigated sufficiently. This letter evaluates the robustness of the DOB-based AQM controller when the number of TCP connections and the RTT delay vary. Simulation results show that the DOB-based proportional-derivative (PD) controller provides better robustness than a classical proportional-integral-derivative (PID) controller.

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In this letter, the phase compensation method is proposed to remove the phase error in Pi-SAR-X2 POLSAR data. In August and October 2013, Pi-SAR-X2 observations were carried out. In a part of VH and VV observation data, the undesired phase pattern appeared. This phase error was caused by the mismatch between the flight navigation data and polarimetric raw data. The compensation method based on the reciprocity principle is considered. The experimental results show the usefulness of the proposed method and it is shown that the undesired phase pattern is clearly removed in the compensated data.

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