Being different from other networks, the load and direction of data traffic for wireless sensor networks are rather predictable. The relationships between nodes are cooperative rather than competitive. These features allow the design approach of a protocol stack to be able to use the cross-layer interactive way instead of a hierarchical structure. The proposed cross-layer protocol CLWSN optimizes the channel allocation in the MAC layer using the information from the routing tables, reduces the conflicting set, and improves the throughput. Simulations revealed that it outperforms SMAC and MINA in terms of delay and energy consumption.

Wireless LAN access is now being offered by small personal terminals in addition to laptops. Since these terminals have very limited battery capacity, wireless LAN interfaces that offer some form of power saving are essential. IEEE802.11. specifies PSM (Power save management); it reduces power consumption by suspending some communications functions. However, since Multicasting and Broadcasting are invariably received by all terminals regardless of PSM, the terminals unnecessarily consume electric power, even if the terminal is not multicast subscriber. This paper clarifies this problem, and proposes a scheme for reducing power consumption. The results of an experiment confirm its excellent performance.

Analysis of waiting time to deliver a message M from a source S to a destination D is deeply related to connectivity analysis, which is an important issue in fundamental studies of mobile multi-hop networks. In [1], we compared the mean waiting times of two methods to deliver M with the mean value of the minimum waiting time. The mean minimum waiting time was obtained by computer simulation because theoretical analysis of this mean is not easy, although another two methods were analyzed theoretically. In this paper, we propose an approximate method to theoretically analyze the mean minimum waiting time in a one-dimensional street network, and show that this method gives a good approximation of the mean minimum waiting time. Also, we consider shadowing and change of directions of mobile nodes at intersections as negative factors arising in two-dimensional street networks. We extend the above method to compute the mean minimum waiting time considering these factors, and discuss how the mean minimum waiting time is affected by these factors.

We propose a novel 50 Mb/s optical transmitter fabricated in a 0.6 µm BiCMOS technology for automotive applications. The proposed VCSEL driver chip was designed to operate with a single supply voltage ranging from 3.0 V to 5.25 V. A fully integrated feedforward current control circuit is presented to stabilize the optical output power without any external components. The experimental results show that the optical output power can be stable within a 1.1 dB range and the extinction ratio greater than 14 dB over the automotive environmental temperature range of -40 to 105.

In this paper, a low power current protection circuit implemented in a low dropout regulator (LDO) is presented. The proposed circuit, designed in a 0.35 µm CMOS process, provides a precise limiting current as well as holding current with low dependency on both supply voltage and regulator output voltage. The experimental results showed that the proposed circuit is operable in the regulator output voltage range from VOUT=1.2 V to VOUT=3.6 V and supply voltage range from VDD=VOUT+0.5 V to VDD=5.6 V. Since the proposed circuit is composed of few simple basic circuits such as a comparator and a Schmitt Trigger, it has a low current consumption of less than ISS=0.82 µA at a load current of ILOAD=200 mA. This makes the circuit suitable for low power and low voltage LDO design.

GaAs MMICs (Monolithic Microwave Integrated Circuits) reliability is a critical part of the overall reliability of the thermal solution in semiconductor devices. With MMICs reliability improved, GaAs MMICs failure rates will reach levels which are impractical to measure with conventional methods in the near future. This letter proposes a methodology to predict the GaAs MMICs reliability by combining empirical and statistical methods based on zero-failure GaAs MMICs life testing data. Besides, we investigate the effect of accelerated factors on MMICs degradation and make a comparison between the Weibull and lognormal distributions. The method has been used in the reliability evaluation of GaAs MMICs successfully.

The importance of redundant technologies for improving dependability and delay fault testability are growing. This paper presents properties of a class of redundant technologies, namely two-rail logic, and analyzes testability of path delay faults occurring on two-rail logic circuits. The paper reveals the following characteristics of two-rail logic circuits: While the number of paths in two-rail logic circuits is twice that in ordinary single-rail logic circuits, the number of robust testable path delay faults in two-rail logic circuits is twice or more that in the single-rail logic circuits. This suggests two-rail logic circuits are more testable than ordinary single-rail logic circuits. On two-rail logic circuits, there may be some robust testable path delay faults that are functional un-sensitizable for any input vectors consisting of codewords of two-rail codes, i.e. for any input vectors that can occur during fault-free operation. Even if such faults occur, the circuits are still strongly fault secure for unidirectional stuck-at faults as well as they work correctly.

The paper introduces both high-speed transmission and quality of system to offer the Internet services on a HFC (Hybrid Fiber Coaxial) network. This utilizes modulating the phase and the amplitude to the signal of the IPMS (Internet Protocol Multicasting Service). An IP-cable transmitter, IP-cable modem, and IP-cable management servers that support 30-Mbps IPMS on the HFC were developed. The system provides a 21 Mbps HDTV transporting stream on a cable TV network. It can sustain a clear screen for a long time.

We propose a Multiple Zones-based (M-Zone) routing protocol to discover node-disjoint multiplath routing efficiently and effectively in large-scale MANETs. Compared with single path routing, multipath routing can improve robustness, load balancing and throughput of a network. However, it is very difficult to achieve node-disjoint multipath routing in large-scale MANETs. To ensure finding node-disjoint multiple paths, the M-Zone protocol divides the region between a source and a destination into multiple zones based on geographical location and each path is mapped to a distinct zone. Performance analysis shows that M-Zone has good stability, and the control complexity and storage complexity of M-Zone are lower than those of the well-known AODVM protocol. Simulation studies show that the average end-to-end delay of M-Zone is lower than that of AODVM and the routing overhead of M-Zone is less than that of AODVM.

We investigate numerically the applicability of photonic crystal fiber (PCF) with a uniform air hole structure as a wide-band transmission medium. We show that accumulated dispersion over the PCF can be reduced effectively by optimizing the index profile of dispersion compensating fiber (DCF). We also show that a bandwidth of more than 300 nm will be available for 40 Gbit/s NRZ transmission by using the PCF as a transmission medium instead of conventional 1.3 µm zero-dispersion single-mode fiber (SMF).

This letter presents beam tilting characteristics of a slot antenna element with reactance loading. It is found that the beam tilt is obtained by controlling aperture electric field distributions with a loaded reactance on the slot. A large beam tilt angle is obtained when an inductive reactance element is loaded.

Due to the recent increase in electronic devices mounted on automobiles, a large number of connectors, especially low-cost tin plated connectors are being used. As a result, their contact reliability has become problematic. Furthermore, for the connectors which are subjected to fretting wear caused by heat cycle and vibrations, the contact resistance increases because of wear of tin and deposition of oxides, which generates problems of poor contact. This study is intended to analyze the change in contact resistance of tin plated connectors from the start of fretting wear to the end of their lifetime from the viewpoint of practical reliability, and to observe the trace and the characteristics of fretting wear microscopically. This study found that wear and oxidation of tin plated connectors start immediately with fretting wear, and thus accumulation of abrasion powder on fretting areas causes connectors to reach to the end of their useful lifetime quickly. Especially, it was demonstrated that amplitude of fretting has a considerable influence on a connector's lifetime. It is made clear that air-tightness, so-called "gas-tight" of tin in a fretting area influences fretting wear considerably.

Ad-Hoc networks are collections of mobile nodes communicating using wireless media without any fixed infrastructure. Minimal configuration and quick deployment make Ad-Hoc networks suitable for emergency situations like natural disasters or military conflicts. The current Ad-Hoc networks can only support either high mobility or high transmission rate at a time because they employ static approaches in their routing schemes. However, due to the continuous expansion of the Ad-Hoc network size, node-mobility and transmission rate, the development of new adaptive and dynamic routing schemes has become crucial. In this paper we propose a new routing scheme to support high transmission rates and high node-mobility simultaneously in a big Ad-Hoc network, by combining a new proposed packet-pheromone-based approach with the Hint Based Probabilistic Protocol (HBPP) for congestion avoidance with dynamic path selection in packet forwarding process. Because of using the available feedback information, the proposed algorithm does not introduce any additional overhead. The extensive simulation-based analysis conducted in this paper indicates that the proposed algorithm offers small packet-latency and achieves a significantly higher delivery probability in comparison with the available Hint-Based Probabilistic Protocol (HBPP).

We propose a novel technique for estimating the number of people in a video sequence; it has the advantages of being stable even in crowded situations and needing no ground-truth data. By analyzing the geometrical relationships between image pixels and their intersection volumes in the real world quantitatively, a foreground image directly indicates the number of people. Because foreground detection is possible even in crowded situations, the proposed method can be applied in such situations. Moreover, it can estimate the number of people in an a priori manner, so it needs no ground-truth data unlike existing feature-based estimation techniques. Experiments show the validity of the proposed method.

Electrical contacts are the most important parts of electrical circuits, and many reliability problems of the circuits are related to contact failure. The contact resistance is one of the important factors for assessing connector reliability, and thus the prediction of contact resistance is essential to designing electrical terminals. In this study, embossments, each 1 mm to 3 mm in radius, were brought into contact with flat planes to simulate the point of contact on a terminal, and the contact resistance was measured using a four-probe method under a load up to 40 N. Copper alloy samples, each plated with tin or silver and having an embossment of 1 mm to 3 mm in radius, were used and the visually clear indentations resulting from the embossment to plane contact were measured to determine their areas. Since the contact resistance is dependent on the contact area, an FEM analysis must be carried out to determine the contact areas correctly. In this paper, an elasto-plastic FEM analysis was performed taking the plating layers into account, and a method was established to make precise determination of the contact areas for different shapes of contacts and loads. The resultant contact areas were used to calculate the contact resistance, which showed a good agreement with experimental results. It was established that the load-resistance curves can be predicted on the basis of the shapes of the contacts as well as plating.

In this letter we give a lower bound on the worst-case time complexity of Dijkstra's three-state mutual exclusion algorithm by specifying a concrete behavior of the algorithm. We also show that our result is more accurate than the known best bound.

This paper presents a fuzzy-based path selection method for improving the security level, in which each cluster chooses paths based on the detection power of false data and energy efficiency.

Using the transient current switch circuit in parallel with the energizing contacts, the slow decay of the contact current due to thermal fusion of metal was observed just after the contact voltage exceeded the melting contact voltage Um. At that time, the contact voltage was higher than the boiling contact voltage Ub. These results contradict Holm's θ theory. A new melting model of breaking mechanical contact is proposed. The area surrounding a cluster of contacting a-spots melts, the melt metal diffuses, and the contact spot thermally shrinks. Including the metal phase transition from solid to liquid, the increase of contact resistance is introduced to the electric circuit analysis. The numerical analysis agrees qualitatively with measured V-I characteristics.

Basic features of fretting and factors affecting its deleterious effects on the performance of electrical/electronic connection were reviewed. It was shown that although the fretting cannot be eliminated completely, its deleterious effects can be substantially reduced by lubrication and also connection design.

The line-based method has been one of the most commonly-used methods of hardware implementation of two-dimensional (2D) discrete wavelet transform (DWT). However, data buffer is required between the row DWT processor and the column DWT processor to solve the data flow mismatch, which increases the on-chip memory size and the output latency. Since the incompatible data flow is induced from the intrinsic property of adopted lifting-based algorithm, a decomposed lifting algorithm (DLA) is presented by rearranging the data path of lifting steps to ensure that image data is processed in raster scan manner in row processor and column processor. Theoretical analysis indicates that the precision issue of DLA outperforms other lifting-based algorithms in terms of round-off noise and internal word-length. A memory-efficient and high-performance line-based architecture is proposed based on DLA without the implementation of data buffer. For an N M image, only 2N internal memory is required for 5/3 filter and 4N of that is required for 9/7 filter to perform 2D DWT, where N and M indicate the width and height of an image. Compared with related 2D DWT architectures, the size of on-chip memory is reduced significantly under the same arithmetic cost, memory bandwidth and timing constraint. This design was implemented in SMIC 0.18 µm CMOS logic fabrication with 32 kbits dual-port RAM and 20 K equivalent 2-input NAND gates in a 1.00 mm 1.00 mm die, which can process 512 512 image under 100 MHz.