The WEP (Wired Equivalent Privacy) is a part of IEEE 802.11 standard designed for protecting over-the- . While almost all of the WLAN (Wireless LAN) cards and the APs (Access Points) support WEP, a serious key recovery attack (aka FMS attack) was identified by Fluhrer et al. The FMS attack can basically be prevented by skipping IVs (Initial Values) used in the attack, but naive skip methods reveal information on the WEP key since most of them depend on the WEP key and the patterns of the skipped IV reveal it. In order to skip IVs safely, the skip patterns must be chosen carefully. In this paper, we review the attack conditions (6) and (7), whose success probability is the highest, 0.05, amongst all known conditions to guess one key-byte from one packet. Then we identify their safe skip patterns.

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There are many protocols proposed for protecting Radio Frequency Identification (RFID) system privacy and security. A number of these protocols are designed for protecting long-term security of RFID system using symmetric key or public key cryptosystem. Others are designed for protecting user anonymity and privacy. In practice, the use of RFID technology often has a short lifespan, such as commodity check out, supply chain management and so on. Furthermore, we know that designing a long-term security architecture to protect the security and privacy of RFID tags information requires a thorough consideration from many different aspects. However, any security enhancement on RFID technology will jack up its cost which may be detrimental to its widespread deployment. Due to the severe constraints of RFID tag resources (e. g., power source, computing power, communication bandwidth) and open nature of RFID usage, it is a great challenge to secure a typical RFID system. For example, computational heavy public key and symmetric key cryptography algorithms (e. g., RSA and AES) may not be suitable or over-killed to protect RFID security or privacy. These factors motivate us to research an efficient and cost effective solution for RFID security and privacy protection. In this paper, we propose a new effective generic binary tree based key agreement protocol (called BKAP) and its variations, and show how it can be applied to secure the low cost and resource constraint RFID system. This BKAP is not a general purpose key agreement protocol rather it is a special purpose protocol to protect privacy, un-traceability and anonymity in a single RFID closed system domain.

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In this paper, the world's first experimental evaluation of the Wi-SUN Japan Utility Telemetering Association (JUTA) profile-compliant feathery receiver-initiated transmission (JUTA F-RIT) protocol is conducted. Firstly, the transmission success rate in an interference environment is evaluated by theoretical analysis and computer simulations. The analysis is derived from the interference model focusing on the carrier sense. The analysis and simulation results agree as regards the transmission success rate of the JUTA F-RIT protocol. Secondly, we develop the dongle-type prototype that hosts the JUTA F-RIT protocol. Measurement results in a cochannel interference environment show that the transmission success rate at the lower MAC layer is around 94% when the number of terminals is 20. When the waiting time for the establishment of the communication link can be extended to exceed 10 s, the JUTA F-RIT protocol can achieve the transmission success rate of over 90% without the re-establishment of the communication link and re-transmission of data frames. Moreover, the experimental results are examined from two viewpoints of the performance of the frame transmissions and the timeout incident, and the feature of the JUTA F-RIT protocol are discussed.

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Air Traffic Control (ATC) communication suffers from issues such as high electromagnetic interference, fast speech rate, and low intelligibility, which pose challenges for downstream tasks like Automatic Speech Recognition (ASR). This article aims to research how to enhance the audio quality and intelligibility of civil aviation speech through speech enhancement methods, thereby improving the accuracy of speech recognition and providing support for the digitalization of civil aviation. We propose a speech enhancement model called DIUnet_V (DenseNet & Inception & U-Net & Volume) that combines both time-frequency and time-domain methods to effectively handle the specific characteristics of civil aviation speech, such as predominant electromagnetic interference and fast speech rate. For model evaluation, we assess the denoising and enhancement effects using three metrics: Signal-to-Noise Ratio (SNR), Mean Opinion Score (MOS), and speech recognition error rate. On a simulated ATC training recording dataset, DIUnet_Volume10 achieved an SNR value of 7.3861, showing a 4.5663 improvement compared to the original U-net model. To address the challenge of the absence of clean speech in the ATC working environment, which makes it difficult to accurately calculate SNR, we propose evaluating the denoising effects indirectly based on the recognition performance of an ATC speech recognition system. On a real ATC speech dataset, the average word error rate decreased by 1.79% absolute and the average sentence error rate decreased by 3% absolute for DIUnet_V processed speech compared to the unprocessed speech in the built speech recognition system.

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A novel solid electrolyte type ammonia (NH₃) gas sensor was fabricated by the combination of the trivalent aluminum cation conducting solid electrolyte (Al_0.2Zr_0.8)_20/19Nb(PO₄)₃ with La₂O₂SO₄–(NH₄)₂HPO₄ as an auxiliary sensing electrode. Since the present sensor exhibited such a superior sensing performance of theoretical response, which obeys the Nernst relationship between the sensor EMF output and the logarithm of the NH₃ gas concentration along with the stable, continuous, and reproducible response even under humidified condition, it is greatly expected to be applied to a practical NH₃ gas sensing device.

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Organized hematoma, which exhibits a net-like appearance on imaging studies, is one of the predisposing factors for the recurrence of chronic subdural hematoma. Patients who are positive for the net-like appearance are often treated with only burr hole surgery. We investigated the relationship between postoperative structural changes in the net-like appearance and the recurrence rate of chronic subdural hematoma. Of the 949 patients with chronic subdural hematoma treated with primary burr hole surgery between January 2010 and April 2021 at our hospital, 268 who were considered positive for the net-like appearance on T2- and T2 star-weighted magnetic resonance images were extracted. We followed the structural changes in the net-like appearance postoperatively and subsequently classified the patients into three groups: decreasing type, shifting type, and no change and deterioration type. The relationship between each structural change and the recurrence rate in the three groups was investigated. Postoperative recurrence requiring surgery occurred in 3.5% of the subjects with decreasing type, 0% with shifting type, and 100% with deterioration type of the net-like appearance (P < 0.05), indicating differences in the recurrence rates according to postoperative structural changes in the magnetic resonance images (MRI) features of chronic subdural hematoma. Our results indicate that the risk of postoperative chronic subdural hematoma recurrence can be predicted by focusing on the structural changes in the postoperative net-like appearance on MRI.

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Safety is our first mission. To insure the safety railway operation, we have to keep in touch between the on board crews and dispatchers. The train radio is the key technology to tie between them. The radio we have been operated for 20 years, which is used sound technology and not ready for data communication, and the voice distinction is worse than the modern digital radio. We have some reasons to convert to the digital radio. The first, the voice will be clearer than ever. The second, we can realize the data communication. The third, the bandwidth is narrower than the current system and we can divide from one communication channel to 2 channels. But before we step forward to digital radio system, we have to make strategy to convert to digital, because the current analog radio stations both fixed and mobiles-are huge numbers and change to digital system gradually. If we can change analog to digital easily, it will be the easiest way to convert to newer system. At that point of view, we noticed that software defined radio can change the radio type by changing the software on the common hardware platform. In this paper we describe about newly developed train radio using software defined radio (SDR) technology, synchronized between radios via the Ethernet, encryption method for data communication and resolution IP address from train number.

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パルス間隔・幅変調方式の応用として, 画像1チャンネルの標本値でパルス幅を, また, 他の画像1チャンネルの標本値でパルス間隔を変調し伝送する画像2チャンネル多重伝送システムを提案し, 実験によりその有用性を確認した.本方式では多重度は2チャンネルに限られるが, 極めて簡単な回路構成によりシステムが実現できる.このため, 機器の簡易小形化, 低消費電力化をはかることができ, 簡易形の画像伝送システムのみならず, 移動・臨時回線および各種モニター回線などの短距離システムにも応用し得ると考えられる.また, 光ファイバーや光空間伝送回線を通しての光通信システムにも応用され得る可能性を持つ.

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This paper aims to provide a description about the performance of Indonesian domestic flight punctuality for the year 2008 with a sample of the Jakarta-Surabaya route (CGK-SUB). The method of data analysis using descriptive developmental formula based on the total performance score obtained from the formula of periodic OTP. The overall results show performance of punctuality and the high number of departure delays. Of the 16 companies having scheduled flight studied, there were eight airlines serving the route CGK-SUB in full during the year 2008. The eight airlines are GIA, MNA, LNI, BTV, MDL, AWQ, SJY, and AFE.In total weighting, there are five airlines considered relaitively good with a score of 2.50 to 3.70. All the five have a relatively small percentage of delays, especially for the delay in the third category, namely the delay of more than 60 minutes.

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In this paper, we propose a framework of connectivity analysis for aviation ad hoc networks on flight paths. First, a general analytical connectivity model for the common one-dimensional ad hoc network is newly developed. Then it is applied for modeling the connectivity of ad hoc networks among aircraft along flight paths where aircraft arrival process follows a Poisson distribution. Connectivity is expressed in terms of connectedness probability of two nodes in the network, connected distance, and network coverage extension factor. An exact closed form derivation of connectedness probability is proposed. The radical effect of mobility on the network connectedness of aircraft over a single flight path is analyzed. The network connectedness probability depends on node density and node distribution, which are derived from node arrival rate and node velocity. Based on these results, the proposed model is extended to the practical case of paths with multi-velocity air traffic classes. Using this model, the critical values of system parameters for the network of aircraft with certain connectivity requirements can be derived. It helps to evaluate network extension capability under the constraints of various system parameters.

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In wireless links between ground stations and UAVs (Unmanned Aerial Vehicles), wireless signals may be attenuated by obstructions such as buildings. A three-dimensional RSS (Received Signal Strength) map (3D-RSS map), which represents a set of RSSs at various reception points in a three-dimensional area, is a promising geographical database that can be used to design reliable ground-to-air wireless links. The construction of a 3D-RSS map requires higher computational complexity, especially for a large 3D area. In order to sequentially estimate a 3D-RSS map from partial observations of RSS values in the 3D area, we propose a graph Laplacian-based sequential smooth estimator. In the proposed estimator, the 3D area is divided into voxels, and a UAV observes the RSS values at the voxels along a predetermined path. By considering the voxels as vertices in an undirected graph, a measurement graph is dynamically constructed using vertices from which recent observations were obtained and their neighboring vertices, and the 3D-RSS map is sequentially estimated by performing graph Laplacian regularized least square estimation.

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A city-level digital twin is a critical enabling technology to construct a smart city that helps improve citizens' living conditions and quality of life. Currently, research and development regarding the digital replica city are pursued worldwide. However, many research projects only focus on creating the 3D city model. A mechanism to involve key players, such as data providers, service providers, and application developers, is essential for constructing the digital replica city and producing various city applications. Based on this motivation, the authors of this paper are pursuing a research project, namely Decentralized Digital Twin EcoSystem (D2EcoSys), to create an ecosystem to advance (and self-grow) the digital replica city regarding time and space directions, city services, and values. This paper introduces an overview of the D2EcoSys project: vision, problem statement, and approach. In addition, the paper discusses the recent research results regarding networking technologies and demonstrates an early testbed built in the Kashiwa-no-ha smart city.

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テレビジョンのゴースト障害の対策として, 都市内で発生しているような複雑なゴースト障害の発生源を, 受信アンテナを移動することなく1ヵ所で探知することが望まれていた.ゴースト波源探知システムは, このために開発したもので, アンテナを1回転させながら遅延時間によりゴースト波を分離して, 各ゴースト波の受信パターンを求めることで到来方向を測定し, さらに遅延時間の値とともに計算して, ゴースト波の発生源の位置を探知する装置である.試作装置は, 制御と演算にコンピューターを用いて構成したもので, 短時間に高精度でゴースト波源を探知でき, 野外実験の結果からも, 充分な実用性を有することが確認できた.

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AeroMACS (Aeronautical Mobile Airport Communications System) is one of the next-generation aeronautical communication standards aimed at aircraft on the airport surface. The advantages of AeroMACS, namely high-speed and large-capacity communication, will enable the TBO (Trajectory Based Operation) concept to be achieved in the future, which will realize safer and more efficient aircraft operation. In our previous research, the basic functions of AeroMACS were confirmed with developed prototypes of an AeroMACS transceiver. This study aims to enhance the AeroMACS technology in two respects: expansion of the communication coverage area, and demonstration of application. This paper reports that the developed handover technology solves the communication blind zone in airports, and the communication coverage reached the aircraft flying vicinity of the airport through tracking with high-gain antennas. Also, the potential of the AeroMACS is made clear through application to the communication media of SWIM (System Wide Information Management) data sharing, and implementation of QoS (Quality of Service) functions for practical aeronautical communication.

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