Teruyuki Hasegawa

Rapid Channel Zapping for IPTV Broadcasting with Additional Multicast Stream

This paper proposes a novel approach for improving channel zapping delay on IPTV broadcasting services. Channel zapping delay is a crucial issue for digital TV broadcasting, which entails audio/video data buffering before reproduction. Such delay could be mitigated in an IP environment if a receiver accelerated this buffering using additional burst transmissions from dedicated servers when a channel zap occurs. However, most conventional solutions are based on the unicast burst, which may cause an impulsive server/network load because channel zaps tend to happen simultaneously when programs are finished or suspended by commercial messages. To reduce this load, we propose a new multicast-based solution that takes into consideration the timing variation in channel zap on each receiver. We have confirmed a maximum 1-second reduction in the zapping delay using commercial multicast streams.

IP-based HDTV broadcasting system architecture with non-stop service availability

This paper presents an architectural concept for IP-based TV broadcasting infrastructure on ISPs multicast network. As broadcasting grows into an indispensable service menu for ISP, its service availability and independency of content format are crucial issues for smooth business deployment. Hence we newly propose some practical solutions to realize a non-stop IP broadcasting service with simple and content format free server implementation. We also implemented a prototype as an HDTV broadcasting system. The verification results show that our system can compensate about 27,500 packet losses and archive non-stop HDTV broadcasting, even in the event of network layer trouble, without any changes in router implementation.

Development of REBCO Coated Conductors by TFA-MOD Method With High Characteristic in Magnetic Field

Y_xGd_{(1 - x)}Ba₂Cu₃ O_y coated conductors (CCs) with artificial pinning centers (APCs) were fabricated by the trifluoroacetates-metal organic deposition method using a batch heat-treatment process. This process has been industrially applied to fabricate long superconducting tapes that have high critical current (<i>I</i>_c). From the viewpoint of applications, the characteristics in magnetic fields become further important, and one solution has been shown previously as introduction of APCs such as BaZrO₃. We applied the technique to our CCs fabrication process. The heat-treatment conditions, specifically total gas pressure, oxygen concentration, and crystallization temperature, were optimized for the batch heat-treatment process. As a consequence, fabricated CC showed extremely high characteristic <i>Jc</i> value of 3.5 MA/cm² in self field, and 0.3 MA/cm² at 3 T in liquid N₂. Moreover, by cross-sectional transmission electron microscopy observation, it was confirmed that the APC was distributed uniformly. Furthermore, the anisotropy of the pinning center is also examined based on the evaluation result of the angular dependence of <i>Jc</i> in 3T.

A mechanism for TCP performance enhancement over asymmetrical environment

This paper describes a novel mechanism for achieving sufficient TCP performance over some asymmetrical environment without any modification in customer premises. In todays Internet, several types of access media have an asymmetrical bandwidth characteristic, where the downstream link bandwidth is larger than the upstream. However, such asymmetrical environment may cause TCP performance degradation due to upstream link congestion. In order to solve this problem, we propose a PEP (performance enhancement proxy) based approach to improve TCP downloading throughput by reducing upstream traffic using our compulsory IP fragmentation technique. The results of our performance evaluation show that our experimental proxy implementation is capable of accelerating TCP throughput above three times faster comparing to the case without the proxy.

TCP Throughput Estimation by Lightweight Variable Packet Size Probing in CDMA2000 1x EV-DO Network

TCP throughput is one of the major communication quality metrics. In order to grasp this metric by active measurement while imposing a lower load, various estimation techniques have been proposed. These techniques are categorized as either equation-based or history-based; here we focus on the latter. Conventional history-based estimation techniques target a wired environment and estimate temporally. By contrast, we target a wireless environment and estimate spatially. For TCP throughput estimation using lightweight probing, we propose a new modeling whereby TCP throughput is determined by capacity and delay fluctuation. We evaluate our proposed modeling by conducting experiments in a commercial CDMA2000 1x EV-DO network. This evaluation empirically verified the validity of our model to estimate TCP throughput in a wireless environment with lightweight probing.

Implementation and evaluation of video transfer system over Internet with congestion control based on two level rate control

Recently, video data transfer is one of the major types of traffic over the Internet. However, it is impossible for the current Internet to guarantee the quality of service (QoS) for video transfer and an influx of a large amount of video data into the Internet may cause serious network congestion. To resolve these problems, we previously proposed a protocol using congestion control based on rate control of the video coding level and data transfer level, and evaluated this protocol using software simulation. However, in order to apply this protocol to real video communication, our previous protocol had some problems, mainly with regard to efficiency. In this paper we present an improved specification of a video transfer protocol with two level rate control. This paper also describes the results of implementation and evaluation of an actual video transfer system using our improved protocol, and a commercial video tool with H.261 encoding. The results show our protocol can transfer video data effectively and fairly through a congested network.

NEXT-FIT: Available Bandwidth Measurement over 4G/LTE Networks -- A Curve-Fitting Approach

Available bandwidth (ABW) estimation in wireless networks is a critical issue for quality-of-service (QoS) provisioning. Nowadays, a network path often contains at least one wireless link e.g., mobile users having wireless connection to the Internet through laptop PCs or smartphones. Most of the existing tools for measuring ABW have been developed and evaluated in wired networks. Since the characteristics of wired links and wireless links differ in many respects, such as fluctuations incapacity and stability due to the shared and unreliable nature of the wireless links, ABW estimation tools also need to be evaluated for network paths containing at least one wireless link. In this paper, we have extended our previous work, New Enhanced Available Bandwidth Estimation Technique (NEXT) by introducing a parameter-independent curve-fitting technique to detect the ABW from a one-way queuing delay signature and conducted a real test over a radio interface in a 4G/LTE mobile communication network. For the experiments, a commercial 4G/LTE mobile network of a Japanese mobile operator was used. Extensive simulations over an IEEE 802.11 network were also performed. Simulation results as well as real-world experimental results demonstrate that it is feasible to achieve reliable estimates under certain circumstances. Our extended approach, which we call NEXT -- FIT, has very good ABW estimation results under conditions of different packet sizes, dynamic wireless link rates, and channel noises.

Multi-dimensional sensor data aggregator for adaptive network management in M2M communications

This paper proposes a method of aggregating tempo-spatial data generated by sensors deployed in buildings or houses. The size of each sensor data such as temperature is usually small, but it often involves many additional data to represent its attribute values like time, location, data type and data precision. This would often increase the traffic volume between sensor gateway at building/home side and service providers at server side. In our method, such sensor data are packed into multidimensional matrices indexed by those attribute values for more compact representation, and the compressed sensing technique is adaptively applied to further reduce the data size. The method was applied to a field trial with KDDI corporation to collect data from 29 community facilities, and the traffic volume was reduced to 50% with reasonable precision of data restoration.

NEXT: New enhanced available bandwidth measurement technique, algorithm and evaluation

This paper presents a unique probing scheme and a rate adjustment algorithm that can be used for estimating the available bandwidth (ABW) of an end-to-end network path more accurately and non-intrusively. The proposed algorithm is based on the well-known concept of self-induced congestion and it features a unique probing train structure in which there is a region where packets are sampled more frequently than in other region. This high-density region enables our algorithm to find the turning point more accurately. When the dynamic ABW is outside of this region, we readjust the lower rate and upper rate of the packet stream to fit the dynamic ABW into that region. We appropriately adjust the range between the lower rate and the upper rate using spread factors, which enable us to keep the number of packets few and thus we measured the ABW non-intrusively. Simulation results show that our algorithm outperforms PathChirp, a state of the art measurement algorithm, estimating the ABW with greater accuracy and stability in presence of different cross traffic sources.

Minimum Disclosure Routing for network virtualization

Although virtual collocation of Service Providers (SPs) on top of Infrastructure Providers (InPs) via network virtualization brings various benefits, we posit that operational confidentiality has not been considered in this network model. We extend and apply the Secure Multiparty Computation (SMC) protocol to solving Minimum Disclosure Routing (MDR), that is, enabling an SP to route packets without disclosing routing information to InPs. Our study reveals that MDR can be achieved securely with marginal latency overhead with regard to the convergence time in well-engineered routing algorithms. Our study sheds light on the path for network virtualization to be used to resolve the challenges for ISPs of today.