The erasure demodulation is possible to reduce a block error rate (BLER) and extend the communication range of a wireless system. In the erasure demodulation a demodulator regards a decoded bit as an erasure bit if its corresponding likelihood at the output of the decoder is smaller than a threshold. The demodulator outputs both “0“ and “1“ for the erasure bit and CRC error detection following the erasure demodulation checks which output is correct. As one of those outputs must be a correct bit, BLER performance improves. On the other hand, as the number of erasure bits increases, the number of CRC decoding operations grows exponentially. Thus, in this paper, a trade-off between computational complexity and performance improvement is investigated Packets are treated as an erasure overflow state if the number of erasure bits in each packet exceeds a threshold. They are counted as the packets with date recovery errors (DREs). Numerical results obtained through computer simulation show that the proposed scheme improves the DRE probability.

IP anycast is widely used for root and TLD DNS servers to reduce latency. DNS operators need to perform measurements to understand and improve their service quality. Although it is vital to measure the effect of IP anycast, the measurement requires enough worldwide measurement points to send queries. In this paper, we try a more manageable approach, i.e., analyzing the existing capture data to reveal the response delays between resolvers and authoritative DNS servers. There are two packet capture datasets, the DITL and JP datasets. The DITL dataset is collected by Root server operators and maintained by DNS-OARC. The JP dataset is collected for JP TLD operations. Specifically, we extracted communication delay information from TCP session data in these datasets.Our analysis that uses multiple datasets, i.e., DITL and JP datasets, reveals: 1) Approximately 30% of IPv4 addresses seen at the M-Root & JP DNS server have RTT information and come from over 200 countries. 2) JP DNS servers offer RTT of less than 20ms for 80% of queries from Japan, and RTT of less than 100ms for 80% of queries from outside of Japan. 3) The newly installed M-root Brisbane node offers shorter RTTs in Australia.

Although the domain name system (DNS) is a critical infrastructure of the Internet, accurate DNS configuration is difficult. An inaccurate DNS configuration in the name servers causes failures in name resolution and even unnecessary traffic. Recently, DNS service providers have been gaining attention because they can achieve stable DNS operation without struggling with their DNS configurations. This trend is expected to be strong because using DNS service providers not only involves ease of operation but is also effective in avoiding inaccurate DNS configurations. In this study, we evaluate the current use of DNS service providers and their effectiveness in avoiding inaccurate DNS configurations.

Abuse of the Internet (e.g., spam mailing, phishing, and other antisocial behaviors) is increasing. Blocking such abuses with blacklists is used as a typical countermeasure. A blacklist contains malicious hosts on the Internet reputed to send spam mail, employ phishing, and engage in other antisocial behaviors. By retrieving the blacklists each time when users receive emails, users can reject spam mails. However, it is difficult to keep up with the new malicious hosts created every day, so research is required to maintain the blacklist. In this study, we propose a classification method whose recall rate (97.3%) is higher than that of the best single public blacklist (48.9%). Cardinality analysis, which identifies the access pattern of multiple clients to various domain names, is the main technique of the proposed method. We explain the method together with the results of experiments use 26M domain name system query-response data.

We have proposed and demonstrate Manzai robots that automatically generate Manzai scenarios. Manzai is a Japanese traditional comedy consisting of two comedians with funny dialogues like stand up comedy. Our Manzai robots are a huge system, but it is not easy for users to watch Manzai every day using our Manzai robots. As described herein, we propose a mobile style of presenting our automatically generated Manzai anytime and anywhere using a web application. We designate the application as a Chat-type Manzai Application. The Chat-type Manzai Application is intended to make people healthier by laughing as they relax and watch the Manzai. However, the Chat-type Manzai Application loses direction. Therefore, we propose a new dialogue component: the Name list component. We used experiments of three types to measure the benefits of our proposed application and component.

In 2020, the COVID-19 pandemic is causing significant problems for our society. Although contact tracing is an essential countermeasure for minimizing exposure, its applications are not widely used in Japan. We have developed a Wi-fi based contact tracing system for use in our campus network to protect students and staff. Although the area covered by Wi-fi technology is too wide to accurately analyze contacts, it can still be used for comparative analysis. We conducted preliminary experiments as an example to compare the effects of countermeasures. Our results show that by making 30% of classrooms safe, we can reduce the number of potential exposures by over 90%. This paper summarizes 1) the system design to acquire necessary information while maintaining the privacy of students, and 2) the results of preliminary experiments that compare the effect of countermeasures.

Content Delivery Networks (CDN) are regarded as important internet infrastructure that supports business on the Internet. Network latency has been identified as an important metric to improve the quality of service (QoS) of CDNs. Given the limitations to response times because of the geographic distance between servers and end-users, CDN providers have developed architectures such as Global Server Load Balancing (GSLB) and IP Anycast to realize fast responses. This study investigates how GSLB and IP Anycast contribute towards improving QoS from the users' perspective. User traffic in the campus network was analyzed and it was found that: 1) 88% of the traffic reaps the benefits of well operated internet services, i.e., they have a Round-Trip Time (RTT) of less than 100 milliseconds. 2) Although GSLB is still the primary architecture for realizing fast responses, IP Anycast supports 5.8% of the traffic.

The Domain Name System (DNS) is a key part of the infrastructure of the Internet. Recent discussions have centered on the removal of the shared DNS resolver and the use of a local full-service resolver instead. From the viewpoint of the cache mechanism, these discussions involve removing the shared DNS cache from the Internet. Although the removal of unnecessary parts from a total system tends to simplify the system, such a large configuration change in the system would need to be be carefully analyzed before its actual deployment. This paper presents our analysis of the effect of a shared DNS resolver based on the campus network traffic. Our findings were as follows: 1) this removal can be expected to amplify the DNS traffic by about 3.3 times, 2) the amplification ratio on the root DNS is much higher (about 10.9 times), and 3) removal of all caching systems from the Internet is likely to amplify the DNS traffic by approximately 12.1 times. Thus, the above-mentioned shared DNS resolver removal should not be considered. Our data analysis also revealed: 4) an increase in the number of clients that do not have a local DNS cache and generate repeated queries at short intervals (less than 1 min). 5) Since the amount of traffic from such clients is not small (about 95.0% of total DNS traffic), the deployment of a local cache itself is feasible.

To resist the growth of abnormal traffic such as P2P, DDoS and Internet worms, this paper discusses a circuit design to realize real-time abnormal traffic detection from broadband networks. Real-time counting of cardinality is the key of the circuit. Although our previous study showed the effectiveness of cardinality counting to detect various abnormal traffic, the slowness of DRAM access prevented us from actually deploying the cardinality counting into backbone network. This paper shows that the use of self-timed pipeline circuit can realize a cardinality counting circuit that can handle up-to 100 Gbps networks by hiding the DRAM access latency.

Centralized social networking services (SNSs) or online social networks (OSNs) inherently have privacy concerns. Ciphertext-policy attribute-based encryption (CP-ABE) is an effective and promising tool for protecting privacy in centralized and distributed systems. However, a large effort is required to develop new practical social applications using CP-ABE. Furthermore, such applications often have performance problems because of the substantial computation time needed for ABE. This paper describes the design and implementation of the ABnews system, a Usenet-like social messaging system using ABE and untrusted storage. ABnews is fast because it eliminates the heavy computation of ABE from the interactive access to messages. ABnews inherits application programs from Usenet, and allows Usenet's rich newsreaders to be utilized without any modification. Furthermore, ABnews provides overlay social applications, including a private blogging service, a presence service, and one-to-one direct messaging, on top of bulletin board systems. The ABnews system has been implemented using the cpabe toolkit and Google Drive, which holds encrypted messages. Experimental results show that the overhead of CP-ABE is negligible when implementing such a messaging system on a current cloud storage service.

As centralized social networking services (SNSs) or online social networks (OSNs) have inherent privacy concerns, researchers are working on decentralized SNSs as alternatives for addressing these problems. However, it is very difficult to decentralize all the functions of centralized SNSs. This paper describes a decentralized SNS using social virtual private networks (VPNs) that work together with centralized SNSs. In this decentralized SNS, members can share private information with friends through the social VPNs while hiding the information from centralized SNSs. SNS members run applications and servers on their PCs, allow friends to access the contents of these servers, and have complete control of their own data. Community leader members called hub users run VPN servers and maintain group member lists. Other regular members manipulate the VPN clients easily using Web browsers. The proposed decentralized SNS federates the user authentication of the VPN servers with that of centralized SNSs. Furthermore, the SNS provides a zero sign-on feature for social Web applications running on a closed VPN. For realizing such a social VPN, the authors have extended SoftEther VPN, their fast, open-source VPN software. Experimental results show that applications including file sharing, a text chat, a Wiki program, an interactive game, and Usenet-like messaging performed well using the social VPN over a current fast Internet access line.

Modern authentication mechanisms, including Shibboleth and OAuth, provide user attributes such as affiliations and e-mail addresses. Conventional collaborative methods have problems using such attributes in egress access control for the Web. This paper proposes a new collaborative method using W

Heart disease has the second high mortality rate behind cancer in Japan, and requires quick treatment. To take a part in emerging mHealth, we developed a wearable heart disease monitoring and alerting system “Dentan”. Dentan continuously monitors patient's ECG in his/her daily activities and issues an alert to the patient as well as surrounding people if it detects abnormal heart behavior. Dentan consists of a wireless ECG sensor and a smartphone to achieve light-weighted, low-cost system that does not degrade the patient's Quality of Life. In parallel, we developed ECG analysis algorithm to detect R-wave as well as arrhythmia and performed demonstration experiments to validate its effectiveness. We implemented these algorithms in wireless ECG sensor rather than in smartphone to save power consumption of ECG sensor caused by radio communication.

Most existing collaborative applications on the Web require centralized servers for storing shared data and relaying communication messages among browsers. This paper proposes building a distributed Web browser as a platform for Web-based collaborative applications to address these problems wit

This paper describes how users can collaborate through sharing personal protected Web resources. Personal protected Web resources are Web pages and services that are typically password-protected. One example is a personal page on an auction site. This paper introduces capability-based access control

This paper proposes an anti-spam scheme that uses capability-based access control. In this scheme, rights to bypass spam filters are represented as capabilities, and an email message containing a valid capability bypasses the spam filter and goes straight to the receiver's inbox. As a result, the false positive problem inherent in existing spam filters is eliminated. This scheme allows a user to delegate rights to another person and is compatible with existing email systems and applications. It was implemented in an email client, Mozilla Thunderbird, along with a tool, capability basket, that provides an API for email clients and a graphical user interface (GUI) for users. This tool makes it easy for users to browse and distribute their capabilities. Capabilities are safely distributed by using an overlay network by the instant messenger Skype.

Recently, we have been able to create multimedia contents easily without individual recourse to each medium. Often one needs to select data to match one's impressions from a medium with which one is unfamiliar. We propose a retrieval method for music using "impression" words. The characteristic of the proposed method is the use of the "affective value" of the musical piece based on results of psychological research on music. In order to develop the affective value, we examine the relationship between the affective value and musical structure by applying machine learning. We present the results of this examination and discuss a method for producing affective values.