The routing efficiency of structured overlay networks depends on the consistency of pointers between nodes, where a pointer maps a node identifier to the corresponding address. This consistency can, however, break temporarily when some overlay nodes fail, since it takes time to repair the broken pointers in a distributed manner. Conventional solutions utilize “backpointers” to quickly discover any failure among the pointing nodes, which allow them to fix the pointers in a short time. Overlay nodes are, however, required to maintain backpointers for every pointing node, which incurs significant memory and consistency check overhead. This paper proposes a novel light-weight protocol; an overlay node gives a “living will” containing its acquaintances (backpointers) only to its successor, thus other nodes are freed from the need to maintain it. Our carefully-designed protocol guarantees that all acquaintances are registered via the living will, even in the presence of churn, and the successor notifies the acquaintances for the deceased. Even if the successor passes away and the living will is lost, the successor to the successor can identify the acquaintances with a high success ratio. Simulations show that our protocol greatly reduces memory overhead as well as the detection time for node failure with the cost being a slight increase in messaging load.

Appropriate turn-taking is important in spoken dialogue systems as well as generating correct responses. Especially if the dialogue features quick responses, a user utterance is often incorrectly segmented due to short pauses within it by voice activity detection (VAD). Incorrectly segmented utterances cause problems both in the automatic speech recognition (ASR) results and turn-taking: i.e., an incorrect VAD result leads to ASR errors and causes the system to start responding though the user is still speaking. We develop a method that performs a posteriori restoration for incorrectly segmented utterances and implement it as a plug-in for the MMDAgent open-source software. A crucial part of the method is to classify whether the restoration is required or not. We cast it as a binary classification problem of detecting originally single utterances from pairs of utterance fragments. Various features are used representing timing, prosody, and ASR result information. Experiments show that the proposed method outperformed a baseline with manually-selected features by 4.8% and 3.9% in cross-domain evaluations with two domains. More detailed analysis revealed that the dominant and domain-independent features were utterance intervals and results from the Gaussian mixture model (GMM).

A key issue in Peer-to-Peer (P2P) live streaming systems is that several participant peers tend to leave within a short time period. For example, such a phenomenon is common at the half time of football games and at the end of the performance of famous artists. Such selfish behavior of the participants causes several problems in P2P networks such as the disconnection of the overlay, the departure of backup peers and the occurrence of cyclic reference to backup peers. In this paper, we propose several techniques for tree-structured P2P live streaming systems to enhance their resilience to the simultaneous departure of some participants. As the baseline of the discussion, we will focus on mTreebone which is a typical churn-resilient P2P live streaming system based on the notion of peer stability. The performance of the proposed techniques is evaluated by simulation. The simulation result indicates that even under high churn rates, the proposed techniques significantly reduce the number of attempts needed to connect to backup peers and the recovery time after a fail.

Recently, a malicious user attacks a web browser through a malicious page that exploits the vulnerability of the browser and that executes malicious code. To prevent this attack, some methods have been devised such as DEP (Data Execution Prevention) that prevents data in stack frame or heap region from being executed. However, to evade these defense techniques, return-oriented programming (ROP) is introduced. ROP executes arbitrary code indirectly using gadget, which is group of instructions including ret instruction in a module that doesn't apply ASLR (Address Space Layout Randomization). In this paper, we propose a static approach to detect ROP payload in a network irrespective of the environment of the system under attack. Most studies have tried to detect ROP attacks using dynamic analysis, because ROP has various addresses of gadgets according to loaded modules. These methods have a limitation that must consider the environment of system to operate ROP, such as the version of OS and modules including gadgets. To overcome this limitation, our method detects ROP payload using static analysis without preliminary knowledge about the environment. We extract five characteristics of ROP and then propose a novel algorithm, STROP, to detect ROP in payload without execution. Our idea is as follows: STROP makes stack frame using input payload statically. It extracts addresses suspected as indicating gadgets and makes groups using the addresses. And then, STROP determine whether the payload includes ROP based on static characteristics. We implement a prototype using snort (network-based intrusion system) and evaluate it. Experiments show that our technique can detect ROP payload with a low number of false alarms. False positive (FP) is 1.3% for 2,239 benign files and 0.05-0.51% for 1GB packet dump file. Among 68 ROP payloads, STROP detects 51 payloads. This research can be applied to existing systems that collect malicious codes, such as Honeypot.

We consider an improved control method based on the Stability Transformation Method. Stability Transformation Method detects unknown and unstable periodic orbits of chaotic dynamical systems. Based on the approach to realize the Stability Transformation Method in real systems, we have proposed a control method which can stabilize unknown and unstable periodic orbits embedded in chaotic attractors. However, setting of the control parameters of the control system has remained as unsolved issue. When the dynamics of a target system are unknown, the control parameters have to be set by trial and error. In this paper, we improve the control method with the automatic adjustment function of the control parameters. We show an example of stabilizing unstable periodic orbits of the 3-dimensional hysteresis chaos generator by using the proposed control method. Some results are confirmed by laboratory measurements. The results imply that any unknown and unstable periodic orbits can be stabilized by using the proposed method, if the target chaos system is reduced to 1-dimensional return map.

Recently, return-oriented programming (ROP) attacks have been rapidly increasing. In this letter, we introduce a fast and space-efficient defense technique, called zero-sum defender, that can respond against general ROP attacks. Our technique generates additional codes, at compile time, just before return instructions to check whether the execution has been abused by ROP attacks. We achieve very low runtime overhead with very small increase in file size. In our experimental results, performance overhead is 1.7%, and file size overhead is 4.5%.

This paper describes a very accurate method of estimating the return-path-capacitance and validates the estimation based on low-error measurements for electric-field intrabody communication. The return-path capacitance, Cg, of a mobile transceiver is estimated in two ways. One uses the attenuation factor in transmission and capacitance, Cb, between a human body and the earth ground. The other uses the attenuation factor in reception. To avoid the influence of the lead wire in the estimation of Cb, Cb is estimated from the attenuation factor measured with an amplifier with a low input capacitance. The attenuation factor in reception is derived by using the applied-voltage dependence of the reception rate. This way avoids the influence of any additional instruments on the return-path capacitance and allows that capacitance to be estimated under the same condition as actual intrabody communication. The estimates obtained by the two methods agree well with each other, which means that the estimation of Cb is valid. The results demonstrate the usefulness of the methods.

The dynamic competition between two bounded rational mobile virtual network operators (MVNOs) in a duopoly spectrum market is investigated. A two stage game is employed to model the interaction of the MVNOs and the quality of service of the secondary users is taken into account. The evolutionary game theory is introduced to model the dynamic strategy selections of MVNOs. Using replicated dynamics, the proposed evolutionary game algorithm can converge to a unique evolutionary stable strategy. Simulation results verify that the proposed algorithm can make the MVNOs adaptively adjust the strategies to approximate optimal solution.

Product return is a critical but controversial issue. To deal with such a vague return problem, businesses must improve their information transparency in order to administrate the product return behaviour of their end users. This study proposes an intelligent return administration expert system (iRAES) to provide product return forecasting and decision support for returned product administration. The iRAES consists of two intelligent agents that adopt a hybrid data mining algorithm. The return diagnosis agent generates different alarms for certain types of product return, based on forecasts of the return possibility. The return recommender agent is implemented on the basis of case-based reasoning, and provides the return centre clerk with a recommendation for returned product administration. We present a 3C-iShop scenario to demonstrate the feasibility and efficiency of the iRAES architecture. Our experiments identify a particularly interesting return, for which iRAES generates a recommendation for returned product administration. On average, iRAES decreases the effort required to generate a recommendation by 70% compared to previous return administration systems, and improves performance via return decision support by 37%. iRAES is designed to accelerate product return administration, and improve the performance of product return knowledge management.

This paper clarifies the bifurcation structure of the chaotic attractor in an interrupted circuit with switching delay from theoretical and experimental view points. First, we introduce the circuit model and its dynamics. Next, we define the return map in order to investigate the bifurcation structure of the chaotic attractor. Finally, we discuss the dynamical effect of switching delay in the existence region of the chaotic attractor compared with that of a circuit with ideal switching.

This paper investigates the effects of n-type doping in the emitter-base heterojunction vicinity on the DC and high-frequency characteristics of InP/InGaAs heterojunction bipolar transistors (HBTs). The n-type doping is shown to be very effective for enhancing the tunneling-injection current from the emitter and thus for reducing the collector-current turn-on voltage. However, it is also revealed that an unnecessary increase in the doping level only degrades the current gain, especially in the low-current region. A higher doping level also increases the emitter junction capacitance. The optimized HBT structures with a 0.5-µm-wide emitter exhibit turn-on voltage as low as 0.78 V and current gain of around 80 at JC = 1 mA/µm2. They also provide a current-gain cutoff frequency, ft, of 280 GHz and a maximum oscillation frequency, fmax, of 385 GHz at VCE = 1 V and JC = 3 mA/µm2. These results indicate that the proposed HBTs are very useful for high-speed and low-power IC applications.

In DC/DC converters with low output voltage and high output current, the technique of synchronous rectification is widely used for improving the output efficiency. However, SR buck converters can experience the abnormal phenomenon called “self turn-on” which will occur in the low-side switch under some circuit conditions. “Self turn-on” is a malfunction of the low-side switch, basically caused by the resonance of the parasitic inductance and the parasitic capacitance. It results in noticeable power dissipation. In this paper, the phenomenon will be clearly described and investigated. With the theoretical analysis and the experimental verification, strategies that can suppress this phenomenon are proposed.

Hayabusa returned to Earth on June 13, 2010, becoming the world's first explorer to complete a round-trip voyage to an asteroid. After being released from the spacecraft, the sample return capsule landed in the Woomera Prohibited Area in the desert of South Australia. The capsule recovery team from JAXA found the capsule within 1 h of its landing. The beacon tracking system that was developed by JAXA played an important role in the tracking and discovery of the sample return capsule. The system has flexibility regarding the landing position of the capsule, because it does not rely on primary radar. In this paper, we describe the beacon tracking system and evaluate the system by discussing the results of preliminary examination and of operation on the day of re-entry.

Distributed systems desire to construct a random overlay graph for robustness, efficient information dissemination and load balancing. A random walk-based overlay construction is a promising alternative to generate an ideal random scale free overlay in distributed systems. However, a simple random walk-based overlay construction can be affected by node churn. Especially, the number of edges increases and the degree distribution is skewed. This inappropriate distortion can be exploited by malicious nodes. In this paper, we propose a modified random walk-based overlay construction supported by a logistic/trial based decision function to compensate the impact of node churn. Through event-driven simulations, we show that the decision function helps an overlay maintain the proper degree distribution, low diameter and low clustering coefficient with shorter random walks.

The processor-sharing (PS) rule arises as a natural paradigm in a variety of practical situations, including time-shared computer systems. Although there has been much work on Poisson-input queueing analysis for the PS rule, there have been few results for renewal-input GI/G/1 (PS) systems. We consider the GI/G/1 (PS) system to provide develop a two-moment approximation for the mean performance measures. We derive the relationship between the mean unfinished work and the conditional mean sojourn time for the GI/G/1 (PS) system. Using this relationship, we derive approximate formulas for the mean conditional sojourn time, mean sojourn time, and the mean number of customers in the GI/G/1 (PS) system. Numerical examples are presented to compare the approximation with exact and simulated results. We show that the proposed approximate formulas have good accuracy.

Let G=(V,E) be a graph of order n. A Hamiltonian cycle of G is a cycle that contains every vertex in G. Two Hamiltonian cycles C1= and C2= of G are independent if u1=v1 and ui ≠ vi for 2 ≤ i ≤ n. A set of Hamiltonian cycles {C1, C2, , Ck} of G is mutually independent if its elements are pairwise independent. The mutually independent hamiltonicity IHC(G) of a graph G is the maximum integer k such that for any vertex u of G there are k mutually independent Hamiltonian cycles of G starting at u. For the n-dimensional burnt pancake graph Bn, this paper proved that IHC(B2)=1 and IHC(Bn)=n for n ≥ 3.

Different from distributed baluns, active baluns have group delay variations in the lower bands related to inherent internal capacitances and resistance in transistors. A negative group delay (NGD) circuit is employed as a compensator of group delay variation for an ultra-wideband (UWB) active balun. First, three-cell NGD circuit is inserted into a simple active balun circuit for realizing both group delay compensation and return loss improvement. The simulated results show a group delay variation of 4.8 ps and an input return loss of above 11.5 dB in the UWB band (3.1-10.6 GHz). Then, a pair of one-cell NGD circuits is added to reduce the remaining group delay variation (3.4 ps in simulation). The circuit with the NGD circuits was fabricated on an InGaP/GaAs HBT MMIC substrate. The measured results achieved a group delay variation of 7.7 ps, a gain variation of 0.5 dB, an input return loss of greater than 10 dB, and an output return loss of larger than 8.1 dB in the UWB band.

The Network-on-Chip (NoC) is limited by the reliability constraint, which impels us to exploit the fault-tolerant routing. Generally, there are two main design objectives: tolerating more faults and achieving high network performance. To this end, we propose a new multiple-round dimension-order routing (NMR-DOR). Unlike existing solutions, besides the intermediate nodes inter virtual channels (VCs), some turn-legally intermediate nodes inside each VC are also utilized. Hence, more faults are tolerated by those new introduced intermediate nodes without adding extra VCs. Furthermore, unlike the previous solutions where some VCs are prioritized, the NMR-DOR provides a more flexible manner to evenly distribute packets among different VCs. With extensive simulations, we prove that the NMR-DOR maximally saves more than 90% unreachable node pairs blocked by faults in previous solutions, and significantly reduces the packet latency compared with existing solutions.

An immense number of LAN switches are currently in use worldwide. Therefore, methods that can reduce the energy consumption of these devices are of great practical interest. A simple way to save power in LAN switches is to switch the interfaces to sleep mode when no packets are buffered and to keep the interfaces in active mode while there are packets to be transmitted. Although this would appear to be the most effective energy saving scheme, mode switching gives rise to in-rush current, which can cause electrical damage to devices. This problem arises from excessive mode switching, which should be avoided. Thus, the main objective is to develop a method by which to reduce the number of mode switchings that result in short-duration sleep modes because these switchings do not contribute greatly to energy efficiency but can damage the device. To this end, a method is adopted whereby the interface is kept in active mode for an "extra" period of time after all packets have been flushed from the buffer. This period is the "extra active period (EAP)" and this scheme protects the device at the expense of energy saving efficiency. In this paper, this scheme is evaluated analytically in terms of its power reduction ratio and frequency of mode changes by modifying the M/M/1 and IPP/M/1 queuing models. The numerical results show how the duration of the extra active period degrades the energy saving performance while reducing the number of mode changes. We analytically show an exact trade-off between the power reduction ratio and the average number of turn-ons in the EAP model with Poisson packet arrival. Furthermore, we extend the scheme to determine the EAP dynamically and adaptively depending on the short-term utilization of the interface and demonstrate the effectiveness of the extended scheme by simulation. The newly developed scheme will enable LAN switches to be designed with energy savings in mind without exceeding the constraints of the device.

To deal with the increasing number of mobile devices accessing the Internet and the increasing demands of mobility management, IETF has proposed Mobile IPv6 and its fast handover protocol FMIPv6. In FMIPv6, the possibility of Care-of Address (CoA) collision and the time for Return Routability (RR) procedure result in long handover delay, which makes it unsuitable for real-time applications. In this paper, we propose an improved handover scheme for FMIPv6, which reduces the handover delay by using proactive CoA acquisition, configuration and test method. In our proposal, collision-free CoA is proactively prepared, and the time for RR procedure does not contribute to the handover delay. Furthermore, we analyze our proposal's benefits and overhead tradeoff. The numerical results demonstrate that it outperforms the current schemes, such as FMIPv6 and enhanced FMIPv6, on the aspect of handover delay and packet transmission delay.