We have developed a novel railway signal control system that operates as a distributed system. It consists of a central control unit (called LC) and terminal devices (called FC) that are distributed at the railroad wayside and operate signal devices. The Internet technologies and optical LAN technologies have been used as communication methods between the LC and the FCs. While handling enormous amount of electric cables may cause human errors, the system is expected to reduce troubles of the current signal system at construction works thanks to the Internet technologies. The FC is a distributed terminal device that has its own processor and placed at the railroad wayside to control the field signal devices. The LC is a centralized computer device that has software arranged by the function of the field devices. An optical network system and multiple communication paths between the LC and the FCs realize durable transmissions. Moreover, the assure performance of controls and transmissions have been investigated, and the autonomous distributed signal control system is also discussed as the next steps of the system.

During recent years, there has been a rapid growth in deployment of gossip-based protocol in many multicast applications. In a typical gossip-based protocol, each node acts as dual roles of receiver and sender, independently exchanging data with its neighbors to facilitate scalability and resilience. However, most of previous work in this literature seldom considered cheating issue of end users, which is also very important in face of the fact that the mutual cooperation inherently determines overall system performance. In this paper, we investigate the dishonest behaviors in decentralized gossip-based protocol through extensive experimental study. Our original contributions come in two-fold: In the first part of cheating study, we analytically discuss two typical cheating strategies, that is, intentionally increasing subscription requests and untruthfully calculating forwarding probability, and further evaluate their negative impacts. The results indicate that more attention should be paid to defending cheating behaviors in gossip-based protocol. In the second part of anti-cheating study, we propose a receiver-driven measurement mechanism, which evaluates individual forwarding traffic from the perspective of receivers and thus identifies cheating nodes with high incoming/outgoing ratio. Furthermore, we extend our mechanism by introducing reliable factor to further improve its accuracy. The experiments under various conditions show that it performs quite well in case of serious cheating and achieves considerable performance in other cases.

We have previously proposed a diffusion-type flow control mechanism as a solution for severely time-sensitive flow control required for high-speed networks. In this mechanism, each node in a network manages its local traffic flow using the basis of only the local information directly available to it, by using predetermined rules. In addition, the implementation of decision-making at each node can lead to optimal performance for the whole network. Our previous studies show that our flow control mechanism with certain parameter settings works well in high-speed networks. However, to apply this mechanism to actual networks, it is necessary to clarify how to design a parameter in our control mechanism. In this paper, we investigate the range of the parameter and derive its optimal value enabling the diffusion-type flow control to work effectively.

We introduce (1-γ)-cyclic code and cyclic codes over the finite chain ring R. We prove that the Gray image of a linear (1-γ)-cyclic code over R of length n is a distance invariant quasi-cyclic code over Fpk. We also prove that if (n,p)=1, then every code over Fpk which is the Gray image of a cyclic code over R of length n is equivalent to a quasi-cyclic code.

The passive and sparse reduced-order modeling of a RLC network is presented, where eigenvalues and eigenvectors of the original network are used, and thus the obtained macromodel is more accurate than that provided by the Krylov subspace methods or TBR procedures for a class of circuits. Furthermore, the proposed method is applied to low pass filtering of a reduced-order model produced by these methods without breaking the passivity condition. Therefore, the proposed eigenspace method is not only a reduced-order macromodeling method, but also is embedded in other methods enhancing their performances.

In deep-submicron technologies, process variations can significantly affect the performance and yield of VLSI chips. As a countermeasure to the variations, post-silicon tuning has been proposed. Deskew, where the clock timing of flip-flops (FFs) is tuned by inserted programmable delay elements (PDEs) into the clock tree, is classified into this method. We propose a novel deskew method that decides the delay values of the elements by measuring a small amount of FFs' clock timing and presuming the rest of FFs' clock timings based on a statistical model. In addition, our proposed method can determine the discrete PDE delay value because the rewriting constraint satisfies the condition of total unimodularity.

Autonomous Decentralized Community System (ADCS) makes its basis on offering customized and dynamic services to group of end-users having common preferences at specified time and location. Owing to extreme dynamism in the system caused by rapidly varying user's demands, and severe mobility of users, it is quite difficult to assure timely service provision to all community members. This paper presents autonomous decentralized community system construction by autonomous division and integration technologies to procure service assurance under dynamic situations, without involving significant communication overhead. By adopting the concept of size threshold, the proposed technique continuously maintains the appropriate size of community in constantly and rapidly changing operating environment, to deliver optimal quality of service in terms of response time. The effectiveness of proposed technology has been shown through simulation, which reveals remarkable improvement (up to 29%) in response time.

A (k,2)-track layout of a graph G consists of a 2-track assignment of G and an edge k-coloring of G with no monochromatic X-crossing. This paper studies the problem of (k,2)-track layout of bipartite graph subdivisions. Recently V. Dujmovi and D.R. Wood showed that for every integer d ≥ 2, every graph G with n vertices has a (d+1,2)-track layout of a subdivision of G with 4 log d qn(G) +3 division vertices per edge, where qn(G) is the queue number of G. This paper improves their result for the case of bipartite graphs, and shows that for every integer d ≥ 2, every bipartite graph Gm,n has a (d+1,2)-track layout of a subdivision of Gm,n with 2 log d n -1 division vertices per edge, where m and n are numbers of vertices of the partite sets of Gm,n with m ≥ n.

Based on the expectation-maximization (EM) algorithm, an iterative time-domain channel estimation approach capable of using a priori information is proposed for orthogonal frequency division multiplexing (OFDM) systems in this letter: it outperforms its noniterative counterpart in terms of estimation accuracy as well as bit error rate (BER) performance. Numerical simulations demonstrate that an SNR gain of 1 dB at BER=10-4 with only one iteration and estimation mean square error (MSE) which nearly coincides with the Cramer-Rao bound (CRB) in the low SNR region can be obtained, thanks to the efficient use of a priori information.

In this paper we investigate designing optimal linear transmit/receive processing filters for multiuser MIMO downlinks with imperfect channel state information (CSI) and spatial fading correlation between antenna array at BS. A robust scheme is proposed to obtain the optimal linear transmit/receive filters in the sense of minimizing the average sum mean square error (SMSE) conditional on noisy channel estimates under a per-user transmit power constraint. Using an iterative procedure, the proposed scheme extends the existing optimization algorithm for uncorrelated single-user MIMO systems with perfect CSI to solve the problem of minimizing SMSE in spatially correlated MIMO downlinks with imperfect CSI. Comparing with non-robust scheme, we show that robust scheme efficiently mitigates the BER loss induced by imperfect CSI. In addition, the impact of fading correlation at BS on the performance of the proposed robust scheme is analyzed.

We propose a CMOS image sensor that realizes wide dynamic range imaging and nonlinear representation of I/O characteristics. The proposed image sensor controls the integration time for each pixel based on the brightness distribution of objects. The histogram at the end of the integration is estimated from the early intermediate photodiode values that are read out to an external circuit. Using the estimated histogram, the imaging parameters, which control the integration time pixel-by-pixel, are optimized in the external circuit. According to the imaging parameters, the intermediate photodiode value is compared with the threshold and reset to the starting value depending on the comparison result. These processes repeat several times. At the end of the integration, the photodiode value is reconstructed by using the imaging parameters. Then, wide dynamic range images with adapted I/O characteristics are obtained. We have fabricated a prototype with a size of 6464 pixels using a 0.35-µm 2-poly 4-metal CMOS process. In this paper, we explain the principle of the proposed sensor and discuss the system architecture and its operation. The experimental results obtained using the prototype are also presented, and we verify its effectiveness.

In inter-vehicle networks, it is required that collision warning messages be distributed over multiple hops with significantly short delay. Cut-through packet forwarding is known to be an effective method to reduce forwarding latency. However, it suffers from the reliability issue, which is especially severe in highly mobile scenario, due to multi-path fading. This paper tries to establish a reliable cut-through forwarding scheme by applying diversity combining method to collision warning messages. By exploiting the nature of the multi-hop forwarding of a broadcast packet in CDMA wireless networks, the diversity combining scheme does not incur any additional communication overhead or delay. The simulation results show that diversity combining schemes, especially Maximal Ratio Combining (MRC), can effectively reduce BER by orders of magnitude.

The system level performance of a superposition coded broadcast/unicast service overlay system is considered. Cellular network for unicast service only is considered as interference limited system, where increasing the transmission power does not help improve the network throughput especially when the frequency reuse factor is close to 1. In such cases, the amount of power that does not contribute to improving the throughput can be considered as "unused." This situation motivates us to use the unused power for broadcast services, which can be efficiently provided in OFDM based single frequency networks as in digital multimedia broadcast systems. In this paper, we investigate the performance of such a broadcast/unicast overlay system in which a single frequency broadcast service is superimposed over a unicast cellular service. Alternative service multiplexing using FDM/TDM is also considered for comparison.

We propose and demonstrate a scheme enhancing the performance of optical access networks with Manchester coded downstream and re-modulated NRZ coded upstream. It is achieved by threshold level control of a limiting amplifier at a receiver, and the minimum sensitivity of upstream is significantly improved for the re-modulation scheme with 5 Gb/s Manchester coded downstream and 2.488 Gb/s NRZ upstream data rates.

The control and diagnosis networks in Maglev Train are the most important parts. In the paper, the control and diagnosis network structures are discussed, and the disadvantages of them are described and analyzed. In virtue of role automation decentralized system (RoADS), some basic ideas of RoADS are applied in new network. The structure, component parts and application of new network are proposed, designed and discussed in detail. The comparison results show that new network not only embodies some RoADS' ideas but also better meets the demands of control and diagnosis networks in Maglev Train.

A differential LC-VCO that adopts a transformer with asymmetric turns-ratio has been proposed. The asymmetric turns-ratio of the transformer leads to the suppression of the AM to FM conversion which is caused by the 1/f noise of the current source transistor. The analysis of the proposed scheme and the improvement in phase noise compare to conventional CMOS LC-VCOs are described. The transformer used in proposed VCO occupies about 430430 µm2 of silicon area while the inductor in compared conventional VCO does 390390 µm2.

Using query-by-sketch we propose an application to efficiently create collages with some user interaction. Using rough color strokes that represent the target collage, images are automatically retrieved and segmented to create a seamless collage. The database is indexed using simple geometrical and color features for each region, and histograms that represent these features for each image. The image collection is then queried by means of a simple paint tool. The individual segments retrieved are added to the collage using Poisson image editing or alpha matting. The user is able to modify the default segmentations interactively, as well as the position, scale, and blending options for each object. The resulting collage can then be used as an input query to find other relevant images from the database.

Finite impulse response (FIR) filtering is the most computationally intensive operation in the channelizer of a wireless communication receiver. Higher order FIR channel filters are needed in the channelizer to meet the stringent adjacent channel attenuation specifications of wireless communications standards. The computational cost of FIR filters is dominated by the complexity of the coefficient multipliers. Even though many methods for reducing the complexity of filter multipliers have been proposed in literature, these works focused on lower order filters. This paper presents a coefficient-partitioning-based binary subexpression elimination method for realizing low power FIR filters. We show that the FIR filters implemented using proposed method consume less power and achieve speed improvement compared to existing filter implementations. Design examples of the channel filters employed in the Digital Advanced Mobile Phone System (D-AMPS) and Personal Digital Cellular (PDC) receivers show that the proposed method achieved 23% average reductions of full adder and power consumption and 23.3% reduction of delay over the best existing method. Synthesis results show that the proposed method offers average area reduction of 8% and power reduction of 22% over the best known method in literature.

The deep submicron semiconductor technologies will make the worst-case design impossible, since they can not provide design margins that it requires. We are investigating a typical-case design methodology, which we call the Constructive Timing Violation (CTV). This paper extends the CTV concept to collapse dependent instructions, resulting in performance improvement. Based on detailed simulations, we find the proposed mechanism effectively collapses dependent instructions.

Clustering is indispensable to obtain a general view of series data from a number of data such as gene expression profiles. We propose a novel metric for clustering. The proposed metric automatically normalizes data to minimize a logarithmic scale distance between the data series.