Cloud Profiling Radars (CPRs) play a crucial role in examining various properties of clouds and precipitation. However, the CPR measurements can be influenced by Doppler velocity errors, noise, clutter, and other contaminations, which may lead to inaccurate estimates of cloud parameters. Doppler velocity is a critical parameter for improving the accuracy of cloud microphysical property retrievals from CPR observations. Velocity folding is a common issue that is caused by finite pulse repetition frequency in CPR systems. Therefore, accurate velocity unfolding is essential for reliable cloud microphysics and dynamics analysis. This paper presents a novel velocity unfolding technique for the 94-GHz high-sensitivity super-polarimetric ice crystal detection and explication radar (HG-SPIDER) in Japan. The technique utilizes the relationship between reflectivity (Z) and Doppler velocity (Vd), their gradients and trends, to identify folded velocity pixels. Then, the folded velocity pixels are corrected based on the Nyquist velocity. The proposed method demonstrates better performance compared to the conventional fixed velocity threshold approach in terms of accuracy, with higher correlation against lidar observations (proposed vs. conventional: R = 0.81 vs. 0.70 in precipitation; R = 0.99 vs. 0.95 in clear-air) and improved one-year statistical metrics (R = 0.86 vs. 0.76). Furthermore, the proposed method was tested on a real-time EarthCARE CPR case study, demonstrating its potential for future integration into JAXA’s Level-2 processing algorithm.

Coherent Doppler lidar (CDL) for measuring wind by transmitting frequency-modulated pulse or continuous wave was proposed and demonstrated. A theoretical study showed that, while typical CDL uses single-frequency short-duration pulse by which distance and velocity resolutions are in a trade-off relationship, the new CDL allows us to specify the two resolutions independently. By using a prototype which can work as both typical and new CDLs, observations to clear or cloudy sky were carried out. Analyses of the observed data revealed that the independency was realized. Specifically, about five times finer velocity resolution than typical CDL was confirmed with no sacrifice of distance resolution.

Global three-dimensional wind measurement is important for weather prediction' climate studies' and various meteorological studies. Current space-based passive sensors can make wind measurements with a large coverage area and high temporal and horizontal resolutions but has a low vertical resolution. The World Meteorological Organization (WMO) wants to develop space-based wind profiling systems. A space-based Doppler Wind Lidar (DWL) is one of useful and promising remote sensing techniques to fill the gap of current observations. The National Institute of Information and Communications Technology (NICT) is developing a single-frequency high-energy Tm,Ho:YLF laser, 1-μm key technology and instrument for a future space-based coherent DWL. In the paper' we will describe recent progress and results of development of 1-μm key technology.

Streaming services such as voice and video based on IP technologies have been deployed widely throughout the world. The Asymmetric Digital Subscriber Line (ADSL) is one of broadband access technologies used to offer these services. Network operators and/or integrators must estimate ADSL link rates from the Network Operation Centers (NOC) which are far away from the customer's site. They must also use a simple measuring scheme so that existing network node facilities are not unduly burdened. Unfortunately, there is no practical scheme that can satisfy these requirements. This letter proposes a practical scheme that can estimate ADSL link rates. The proposed scheme allows us to estimate ADSL link rates from measurements made at the NOC using existing communications protocols and network node facilities; it imposes no heavy traffic overhead. The proposed scheme consists of two major steps. The first step is to collect measured data of round trip times (RTT) for both long and short packets to find their minimum values of RTTs, i.e. those do not include queuing delays. The RTT measurements are simply conducted by sending Internet Control Message Protocol (ICMP) echo request messages. The second step is to estimate the ADSL down- and up-link rates by using the difference in RTT between long and short packets and the experimentally-obtained correlated relationships between ADSL down- and up-link rates. RTTs are experimentally measured for an IP network, and it is shown that the down- and up-link rates can be obtained in a simple manner.

One-Way Delay Variation (OWDV) has become increasingly of interest to evaluate network state and service quality, especially for real-time and streaming services such as VoIP and video. Measurement of these parameters needs to be performed with the layout infrastructure. Many schemes for OWD measurements require clock synchronization at the source and destination through Global-Positioning System (GPS) or the Network Time Protocol (NTP). In clock-synchronized approaches, the accuracy of the measurement of OWDV depends on the achieved accuracy of clock synchronization. GPS provides high-accuracy clock synchronization. However, the deployment of GPS on legacy network equipment might be slow and costly. This paper proposes a method for measuring OWDV without recurring to clock synchronization. However, clock skew may affect the measurement of OWDV. The proposed approach is based on the measurement of Inter-Packet Delay (IPD) and Accumulated OWDV (AOWDV). This paper shows the performance of the proposed scheme via simulation and through experimentation in a VoIP network. The presented simulation and experimental results indicate that clock skew can be efficiently measured and removed and that OWDV can be measured without requiring clock synchronization.

High-speed packet switching (HPS) systems can Provide flexible, economical, high-quaiity services for integrated voice, video, and data communications. To realize such HPS systems, methods have been developed to bring about high-speed protocol processing as well as a system architecture for facilitating high-throughput switching. Adopting the parallel processing algorithm into protocol processing allows us to achieve high-speed packet protocol processing of about 100 times faster than conventional processing. Furthermore, a fully distributed system architecture in addition to hierarchical interconnection networks can achieve high-capacity packet switching systems. The proposed HPS system is thus capable of accommodating lines of up to 10-50 Mbits/s, of providing high-throughput switching capability of 1 000 000 packets/s, and of having an average delay of less than 2 ms. Furthermore, an evaluation of network delay performances of video conferencing and voice communications indicate that HPS systems are quite suitable for handling such multimedia communications.