EZ-AG: Structure-free data aggregation in MANETs using push-assisted self-repelling random walks

This paper describes EZ-AG, a structure-free protocol for duplicate insensitive data aggregation in MANETs. The key idea in EZ-AG is to introduce a token that performs a self-repelling random walk in the network and aggregates information from nodes when they are visited for the first time. A self-repelling random walk of a token on a graph is one in which at each step, the token moves to a neighbor that has been visited least often. While self-repelling random walks visit all nodes in the network much faster than plain random walks, they tend to slow down when most of the nodes are already visited. In this paper, we show that a single step push phase at each node can significantly speed up the aggregation and eliminate this slow down. By doing so, EZ-AG achieves aggregation in only O(N) time and messages. In terms of overhead, EZ-AG outperforms existing structure-free data aggregation by a factor of at least log(N) and achieves the lower bound for aggregation message overhead. We demonstrate the scalability and robustness of EZ-AG using ns-3 simulations in networks ranging from 100 to 4000 nodes under different mobility models and node speeds. We also describe a hierarchical extension for EZ-AG that can produce multi-resolution aggregates at each node using only O(NlogN) messages, which is a poly-logarithmic factor improvement over existing techniques

Exploiting random walks for robust, scalable, structure-free data aggregation and routing in mobile ad-hoc networks (MANETs)

The focus of this thesis is on the design of scalable data aggregation protocols for Mobile Ad-hoc Networks (MANETs). Data aggregation Protocols that rely on network structures such as trees or backbones are not well suited for MANETs because the underlying topology of MANETs is constantly changing. On the other hand, unstructured techniques such as flooding and gossiping have a high messaging overhead and take a long time to finish. Therefore, in this thesis, we explore the use of random walks as a structure-free alternative for data aggregation in MANETs.;The basic idea is to introduce one or more tokens that successively visit each node in a MANET by executing a random walk and compute the aggregate state. While random walks are simple, robust and overhead-free, plain random walks tend to be slow in visiting all nodes because the token can get stuck in regions of already visited nodes. Therefore, we first introduce self-repelling random walks (SRRW) in which at each step, the token chooses a neighbor that has been visited the least number of times. While SRRW significantly speeds up random walks in the initial stages, towards the end a slowdown is observed when a significant fraction of nodes are already visited. To address this shortcoming, we then develop two complementary strategies that speed up data aggregation.;First, we introduce gradient biased random walks (a pull-based strategy) where short temporary multi-hop gradients are used to pull the tokens toward unvisited node. We prove that gradient biased random walks achieve a cover time of O(N) and message overhead of O(NlogN) where N is the number of nodes in the network. Next, we introduce a push-based strategy in which self-repelling random walks are complemented by a single step push phase before the random walk phase, in which each node broadcasts its information to its neighbors. We show that this small push goes a long way in speeding up data aggregation. Push based random walks finish data aggregation in O(N) message and time. Finally, we describe hierarchical extension of the push-based protocol which can produce multi-resolution aggregates at each node using only O(NlogN) messages.;All our results are validated using simulations in ns-3 in networks ranging from 100 to 4000 nodes under different network densities, node speed and mobility models

Roles of Exogenous Technologies in Vehicle Innovation: Cases from a Japan’s Automotive Parts Manufacturing Firm

This paper explores the roles of technological innovations in the growth of Japan’s motor vehicle industry, mainly from technology spillover perspective from the early 2000s to today. An empirical analysis focusing on business performances, R&D investments, and patent applications taking a noteworthy unique case in Japan was attempted. Empirical analyses on the productivity of patent to technology stock, use of exogenous technologies for their own technological innovation on its Automotive Business Unit elucidated that innovation capabilities, incorporation of exogenous technologies, and profit generation makes a virtuous cycle of continuous technological innovation. Furthermore, we found that the range of technology spillovers is not only expanding along with the development of information communication technology but also superposing itself intricately between organizational (industry– firm–business unit) layers

Acoustic echo and noise canceller for personal hands-free video IP phone

This paper presents implementation and evaluation of a proposed acoustic echo and noise canceller (AENC) for videotelephony-enabled personal hands-free Internet protocol (IP) phones. This canceller has the following features: noise-robust performance, low processing delay, and low computational complexity. The AENC employs an adaptive digital filter (ADF) and noise reduction (NR) methods that can effectively eliminate undesired acoustic echo and background noise included in a microphone signal even in a noisy environment. The ADF method uses the step-size control approach according to the level of disturbance such as background noise; it can minimize the effect of disturbance in a noisy environment. The NR method estimates the noise level under an assumption that the noise amplitude spectrum is constant in a short period, which cannot be applied to the amplitude spectrum of speech. In addition, this paper presents the method for decreasing the computational complexity of the ADF process without increasing the processing delay to make the processing suitable for real-time implementation. The experimental results demonstrate that the proposed AENC suppresses echo and noise sufficiently in a noisy environment; thus, resulting in natural-sounding speech

FUNDAMENTAL EXPERIMENT FOR CONSTRUCTING IT-TOW

The purpose of this study was to collect some baseline data which may be used for developing an IT-tow system by using a load cell. The pulling forces were measured in 3 tests, hold1 phase, hold2 phase, and drive phase. The pulling force decreased in drive phase defined as the phase the pullers are driven by opponent. This is because the pulling force in this study was defined as tension of the rope, and then pulling force measured in this phase is not produced by subject but produced by examiners side. If the IT-TOW is made by using the load cell, 2 machines have to exchange and reproduce the pulling force of each other. In case the load cell received 2 different pulling forces, pulling force produced by one side may not be measured with accuracy. To put IT-TOW into practice, the pulling force data must be exchanged and not be measured by a load cell, but defined by another system

Sulfur isotope ratios of some Roseki deposits in the Inner Zone of Southwest Japan

Sulfur isotope ratios of pyrite and alunite from 5 Roseki deposits in the Inner Zone of Southwest Japan were determined. The δ34S values of all pyrite samples were in the range from -13.2 to +2.3%, the variation range for each deposit being within 8%. In each deposit δ34S values of alunite were always higher than those of pyrite, which may be interpreted as that alunite was precipirated under more oxidizing conditions than pyrite. Sulfur isotope rations of the Roseki pyrite showed a distribution similar to that of ore sulfur from skarn and vein deposits in the same Zone. This suggests that the origin of sulfur of the Roseki deposits is also host igneous rocks

GROUPING AND NUMERIC CONVERTION AS WAY TO BOOST PERFORMANCE

The purpose of this study was to suggest that the way to boost physical education performance in elementary school by “grouping” and “numeric conversion” on physical education. In this study, 40m-hurdles and running long jump were selected as educational materials. 15 elementary school students were divided into 3 groups. Baselines were determined for each individual. Students practice in a group, with the measurement records being carried out in the P.E. class and compared against those for other groups. This way shows their goal and growth as relative numerical values. By keeping score collaboratively, students acquired new perspective when observing others. In addition, they took know-how or facture of movement into their hearts