The issue of importance of multiuser detection for CDMA-based mobile ad hoc networks is addressed in this paper. For conventional scheme, each terminal in the network uses matched filter to receive packets, so the performance (e.g., throughput) of the network suffers from multi-access interference (MAI). Different from above scheme, in this paper, each terminal of the ad hoc network is equipped with an adaptive blind linear multiuser detector, so the ability of MAI-resistance is gained. Employing slotted-ALOHA protocol in MAC layer and using fully-connected network model, the throughput of ad hoc network is studied. Theoretic analysis and simulation results show that multiuser detection can remarkably improve throughput performance of ad hoc networks.

In this paper, we propose new low-hardware-cost motion estimation with a large search range for VLSI multimedia processors. It reduces the hardware amount required for pixel comparison by reducing both the spatial-resolution and bit-resolution of pixel values. Low-hardware-cost block-matching criterion is also employed. To avoid performance degradation from low resolution, we introduce an "outlier" pixel with large overload quantization error in the search window, and a search position is excluded from the motion estimation if its corresponding search window block contains one or more outliers. The proposed motion estimation is easy to implement in VLSI multimedia processors, and it significantly reduces the hardware amount when the search range is larger than 6464. In MPEG2 MP@ML video compression with 128128 search range, it reduces the hardware cost to 1/144 that of the full search algorithm, while its degradation of peak signal-to-noise ratio is 0.32 dB.

Unwanted electromagnetic emission occurs due to the common-mode current on the cables entering a PC's metal enclosure and can be treated as wire antennas passing through the apertures of the enclosure. To reduce the emission, a stack of metal rings is suggested to be placed around the cable and external to the aperture, adopting the concept of a Coaxial Band-Stop Filter, for the first time. The influence of this novel structure on the common-mode current is examined in the FDTD-method frame work.

A side-coupled microstrip open-loop resonator is presented for design of harmonic-suppressed bandpass filters with compact size. In geometry, the open-ended microstrip feed line is put in close proximity to the loop resonator at the opposite side of an opened-gap. In design, its length is properly lengthened to establish the orthogonal even- and odd-symmetrical current distributions along the two coupled strip conductors. It thus results in cancellation the 1st parasitic resonance. The two-stage open-loop filter is first constructed and its performance is studied under varied feed line lengths. Furthermore, a four-stage filter block is optimally designed at 2.52 GHz and its circuit sample is fabricated with the overall length less than 60% of one guided wavelength. The measured insertion loss at the 1st harmonic is higher than 30 dB, the stopband covers the range from 2.8 GHz to 7.0 GHz, and the dominant pass bandwidth is about 9.0%.

Although data compression is popularly used, compressed data have a problem that they are very sensitive to errors. This paper proposes a single burst error recovery method for Huffman coding by using the bidirectionally decodable Huffman coding. Computer simulation shows that the proposed method can recover 2.5lburst bits burst error with high probability, where lburst is the maximum length of burst errors which the proposed method is expected to be able to recover.

This paper presents a low-complexity equalization for M-ary biorthogonal keying based direct sequence ultra wideband (MBOK DS-UWB) systems. We focus on a Viterbi equalizer, which is based on maximum likelihood sequence estimation (MLSE). To reduce the computational complexity of MLSE-based equalizer, we use two strategies. One is the use of delayed-decision feedback sequence estimation (DDFSE), which is a hybrid estimation between MLSE and decision feedback estimation (DFE). And the other is the truncation of state transition in MLSE by considering MBOK pulse mapping. The reduced complexity sequence estimation is named as reduced state (RS)-DDFSE. By the use of RS-DDFSE, the complexity of Viterbi equalizer for MBOK DS-UWB is significantly reduced, by comparison with that of MLSE. The performance of RS-DDFSE based equalizer is evaluated on multipath fading channel models provided by IEEE802.15.3a. An analysis on trellis diagram of RS-DDFSE and simulation results show that the impact on error rate performance generated by the complexity lower is slight.

In this paper we present a network layer based admission control and simple class based service differentiation model to support QoS in mobile ad hoc network. Our distributed admission control procedure works along with the route finding phase of reactive routing protocols for mobile ad hoc network (AODV, DSR etc). We also propose a simple class based distributed service differentiation system to support QoS once a traffic is admitted by our admission control mechanism. The proposed service differentiation is based on DiffServ model and includes modifications like configuration of each node with edge and core functionality, dynamic selection of edge/core functionality, use of minimal and simple classes. Simulation results show that our system allows seven times more real time traffic in the network than the proposed QoS for AODV model while satisfying the demanded end-to-end delay and providing low jitter.

In this paper, we propose an agent architecture for a combination of speculative computation and abduction. Speculative computation is a tentative computation when complete information for performing computation is not obtained. We use a default value to complement such incomplete information. Unlike usual default reasoning, the real value for the information can be obtained during the computation and the computation can be revised on the fly. In the previous work, we applied this technique to handling distributed problem solving under incomplete communication environments in the context of multi-agent systems and proposed correct procedures in abductive logic programming in terms of perfect model semantics. In the previous work, however, we regarded assumptions as defaults and used these assumptions for speculative computation. Thus, we could not perform hypothetical reasoning, that is, the original usage of abduction. In this paper, we extend our framework so that speculative computation and abduction can be both performed. As a result, our procedure becomes an extension of the abductive procedure developed by Kakas and Mancarella augmented by dynamic belief revision mechanism about outside world.

The process of evaluating and selecting Commercial Off-The-Shelf (COTS) products is complicated because of conflicting priorities of the stakeholders, complex interdependences among the evaluation criteria, multiple evaluation objectives, changing system requirements, and a large number of similar COTS products with extreme capability differences. Numerous COTS evaluation and selection methods have been proposed to address the complexity of the process. Some of these methods have been successfully applied in industry. However, negotiation to resolve stakeholder conflicts is still an ad hoc process. In this paper, we present a systematic model that assists the COTS selection stakeholders in identifying conflicts, as well as in determining and evaluating conflict resolution options. Our model is facilitated by an agent-based decision support system, which has user agents that assist the stakeholders in the COTS evaluation and negotiation process. The agents utilize a hybrid of analytic and artificial intelligence techniques to identify conflicts and the corresponding agreement options. Moreover, each user agent analyzes the agreement options in detail before advising its client about which goals to optimize, and which goals to compromise in order to reach agreement with the other stakeholders. Finally, the community of agents facilitates information sharing among stakeholders in a bid to improve the quality of their COTS selection decisions.

This paper presents two novel blind set-theoretic adaptive filtering algorithms for suppressing "Multiple Access Interference (MAI)," which is one of the central burdens in DS/CDMA systems. We naturally formulate the problem of MAI suppression as an asymptotic minimization of a sequence of cost functions under some linear constraint defined by the desired user's signature. The proposed algorithms embed the constraint into the direction of update, and thus the adaptive filter moves toward the optimal filter without stepping away from the constraint set. In addition, using parallel processors, the proposed algorithms attain excellent performance with linear computational complexity. Geometric interpretation clarifies an advantage of the proposed methods over existing methods. Simulation results demonstrate that the proposed algorithms achieve (i) much higher speed of convergence with rather better bit error rate performance than other blind methods and (ii) much higher speed of convergence than the non-blind NLMS algorithm (indeed, the speed of convergence of the proposed algorithms is comparable to the non-blind RLS algorithm).

Recently, DOAS (differential optical absorption spectroscopy) has been used for nondestructive air monitoring, in which the LS (least squares) method is used to calculate trace gas concentrations due to its computational simplicity. This paper applies the ICA (independent component analysis) method to the DOAS system of air monitoring, since the LS method is insufficient to recover the desired spectra perfectly due to sparsity characteristic. If the sparsity of reference spectra in the DOAS system imposes the assumption of independence, the ICA algorithm can be used. The proposed method is used to regress the observed spectrum on the estimates of the reference spectra. The ICA algorithm can be seen as a preprocessing method where the ICs of the references are used as the input in the regression. The performance of the proposed method is evaluated in simulation studies using synthetic data.

Question answering (QA) is the task of retrieving an answer in response to a question by analyzing documents. Although most of the efforts in developing QA systems are devoted to dealing with electronic text, we consider it is also necessary to develop systems for document images. In this paper, we propose a method of document image retrieval for such QA systems. Since the task is not to retrieve all relevant documents but to find the answer somewhere in documents, retrieval should be precision oriented. The main contribution of this paper is to propose a method of improving precision of document image retrieval by taking into account the co-occurrence of successive terms in a question. The indexing scheme is based on two-dimensional distributions of terms and the weight of co-occurrence is measured by calculating the density distributions of terms. The proposed method was tested by using 1253 pages of documents about the major league baseball with 20 questions and found that it is superior to the baseline method proposed by the authors.

A novel application of fuzzy-neuro approach to protection of double circuit transmission line is demonstrated in this paper. Different system faults on a protected transmission line should be detected and classified rapidly and correctly. Using the proposed approach, fault detection, classification and faulted phase selection could be achieved within a quarter of cycle. Results of performance studies show that the proposed fuzzy-neuro-based module can improve the performance of conventional fault selection algorithms.

This paper presents the results of an investigation on the effect of a thin low-dielectric material (phantom shell) on measuring the Specific Absorption Rate (SAR) in the frequency range of 3 to 6 GHz. The International Electrotechnical Commission (IEC) has started to develop a SAR measurement procedure in order to cover such frequencies. In the procedure, the SAR is measured in a liquid phantom, which is a shell filled with tissue-equivalent liquid. Although the shell is thin and has low-dielectric properties, the influence of the phantom shell is thought to increase at higher frequencies. Therefore, an investigation using the transmission line model and the Finite-Difference Time-Domain (FD-TD) method was conducted. To verify the FD-TD results, measurements were also carried out. The calculation results using the FD-TD method agree well with the measurement results. If the frequency is higher, the SAR is affected by the shell even though the shell is thinner and has much lower dielectric properties than those of the tissue-equivalent liquid. Specifically, the SAR with the shell is approximately 1.3 times higher than without the shell at 5.2 GHz for the maximum case. The deviations in the loss and the thickness for the shell do not affect the SAR more than the relative permittivity.

The emergence of intelligent and sophisticated attack techniques makes web services more vulnerable than ever which are becoming an important business tool in e-commerce. Many techniques have been proposed to remove the security vulnerabilities, yet have limitations. This paper proposes an adaptive mechanism for a web-server intrusion-tolerant system (WITS) to prevent unknown patterns of attacks by adapting known attack patterns. SYN flooding attacks and their adaptive defense mechanisms are simulated as a case study to evaluate the performance of the proposed adaptation mechanism.

In recent years, there has been an increased focus on the mechanics of information transmission in spiking neural networks. Especially the Noise Shaping properties of these networks and their similarity to Delta-Sigma Modulators has received a lot of attention. However, very little of the research done in this area has focused on the effect the weights in these networks have on the Noise Shaping properties and on post-processing of the network output signal. This paper concerns itself with the various modes of network operation and beneficial as well as detrimental effects which the systematic generation of network weights can effect. Also, a method for post-processing of the spiking output signal is introduced, bringing the output signal more in line with conventional Delta-Sigma Modulators. Relevancy of this research to industrial application of neural nets as building blocks of oversampled A/D converters is shown. Also, further points of contention are listed, which must be thoroughly researched to add to the above mentioned applicability of spiking neural nets.

In this paper, crosstalk between multiconductor transmission lines of finite length in arbitrary directions on a printed circuit board is studied by using a circuit-concept approach. The circuit-concept approach of (2+1) finite-length lines is expanded for the crosstalk calculation of (n+1) lines where n>2.2n-port network expression is derived from the modified telegrapher equations. The effect of via currents flowing through the vertical short line sections at the line terminals is also investigated. Due to this expansion the derived equations for (n+1) lines are expected to be easily applied for crosstalk analysis of a variety of complex structures such as via fences and guard traces, etc.

Animation video is becoming very popular with the availability of low cost computing resources. The cell animation is a popular method, used for producing animation video. In order to efficiently encode these videos, conventional video codecs, such as AutoDesk Animation Pro FLC, Intel Indeo 5, and MPEG-4 can be used to achieve high compression. However, when cell animation videos are compressed at very low bit rate by these traditional codecs, objectionable artifacts, e.g., false color, blurred contours, and blocking artifact, are severely occurred. In this paper, we propose an efficient compression method for cell animation images. The proposed method employs hybrid coding scheme which includes intraframe and interframe coding modes. The intraframe mode consists of color quantization, adaptive differential pulse code modulation, forward classification, and Golomb-Rice coding. The interframe coding consists of block-based techniques and exploits the characteristics of motion. Simulation results show that the proposed method provides superior performance over AutoDesk Animation Pro FLC, MPEG-1, Intel Indeo 5, and MPEG-4 standards.

The performance of asynchronous fast frequency hopping-multiple access (AFFH-MA) systems with multiple hops per bit is investigated with a linear-combining receiver in Rayleigh fading. We present an accurate approximation method for evaluating the error probability by using the characteristic function, Taylor series, and Gauss-Chebyshev quadrature rule. We will show that the proposed method provides an accurate approximation, compared with a simple Gaussian approximation. The validity of proposed analytic works is verified through Monte Carlo simulations.

In this paper, a balance-unbalance conversion factor (TCTL: Transverse Conversion Transfer Loss, TCL: Transverse Conversion Loss) and a radiated emission for differential type microstrip lines with a partial unbalance on a PCB (Printed Circuit Board) are investigated. As the result, after inserting an unbalance element, it can be seen that a radiated emission increased according to the deterioration of TCL. The calculated results of the TCTL and TCL by using 4-terminal pair network chain matrix agreed with the measured results very well. In order to calculate radiated emission from the differential type microstrip lines, a common mode current on differential type microstrip lines with a partial unbalance was calculated by using 4-terminal pair network chain matrix. The calculated results of the radiated emission also agreed with the measured results.