2-Factor covering designs, a type of combinatorial designs, have recently received attention since they have industrial applications including software testing. For these applications, even a small reduction on the size of a design is significant, because it directly leads to the reduction of testing cost. In this letter, we report ten new designs that we constructed, which improve on the previously best known results.

This paper evaluates the bit error rate (BER) performance of high rate data transmission such as at 64 and 384 kbits/s (kbps) with high quality (average BER is below 10-6) using turbo/convolutional coding associated with Rake time diversity, antenna diversity, and fast transmission power control (TPC) in multipath fading channels for W-CDMA mobile communications. Laboratory experiments using multipath fading simulators elucidate the superiority of turbo coding over convolutional coding when the channel interleaving length is 40 msec. The required average transmission power for the average BER of 10-6 using turbo coding is decreased by approximately 1.1-1.5 dB and 1.5-1.6 dB for 64 and 384 kbps data transmissions, respectively, compared to that using convolutional coding for a two-path Rayleigh fading channel with the fading maximum Doppler frequency of fD = 5-200 Hz. Furthermore, field experimental results elucidate that the required transmission power for the average BER of 10-6 employing turbo coding is decreased by approximately 0.6 dB and 2.0 dB compared to convolutional coding for 64 and 384 kbps data transmissions, respectively, without antenna diversity reception, while that with antenna diversity reception exhibits only an approximate 0.3-0.5 dB decrease. This decrease in improvement with antenna diversity reception indicates that in an actual fading channel in the field experiments, the impact of the error in path search for Rake combining and SIR measurement for fast TPC diminishes the performance improvement of the turbo coding due to a very low received signal power.

In this paper, we propose a packet-scheduling algorithm, called the Class-level Service Lagging (CSL) algorithm, that guarantees multiple delay bounds for multi-class traffic in packet networks. We derive the associated schedulability test conditions, which are used to determine call admission. We first introduce a novel implementation of priority control, which has a conventional and simple form. We show how the efforts to confirm the logical validity of that implementation are managed to reach the definition of the CSL algorithm. The priority control is realized by imposing class-level unfairness in service provisioning, while the underlying service mechanism is carried out using the notion of fair queueing. The adoption of fair queueing allows the capability to maintain the service quality of the well-behaving traffic even in the presence of misbehaving traffic. We call this the firewall property. Simulation results demonstrate the superiority of the CSL algorithm in both priority control and firewall functionality. We also describe how the CSL algorithm is implementable with a computational complexity of O(1). Those features as well as the enhanced scalability, which results from the class-level approach, confirm the adequacy of the CSL algorithm for the fast packet networks.

The network duplicating can achieve significant improvements of the Local Area Network (LAN)'s performance, availability, and security. For LAN duplicating, a Dual-Path Ethernet Module (DPEM) is developed. Since a DPEM is simply located at the front end of any network device as a transparent add-on type independent hardware machine, it does not require sophisticated server reconfiguration. We examine the desirable properties and the characteristics on the Dual-LAN structure. Our evaluation results show that the developed scheme is more efficient than the conventional Single-LAN structures in various aspects.

In this paper, an online SNR estimator is proposed for parallel combinatorial SS (PC/SS) systems in Nakagami fading channels. The PC/SS systems are called as partial-code-parallel multicode DS/SS systems, which have the higher-speed data transmission capability comparing with conventional multicode DS/SS systems referred to as all-code-parallel systems. We propose an SNR estimator based on a statistical ratio of correlator outputs at the receiver. The SNR at the correlator output is estimated through a simple polynomial from the statistical ratio. We investigate the SNR estimation accuracy in Nakagami fading channels through computer simulations. In addition, we apply it to the convolutional coded PC/SS systems with iterative demodulation and decoding to evaluate the estimation performance from the viewpoint of error rate. Numerical results show that the PC/SS systems with the proposed SNR estimator have superior estimation performance to conventional DS/SS systems. It is also shown that the bit error rate performance using our SNR estimation method is close to the performance with perfect knowledge of channel state information in Nakagami fading channels and correlated Rayleigh fading channels.

This paper presents the theoretical analysis of subband adaptive array combining cyclic prefix transmission scheme (SBAA-CP) in multipath fading environment. The exact expressions for optimal weights, array outputs and the output signal to interference plus noise ratio (SINR) are derived. The analysis shows that use of the cyclic prefix data transmission scheme can significantly improve the performance of subband adaptive array (SBAA). An example of implementing SBAA-CP as a software antenna is also presented.

In-situ position-controlled lateral deposition of nanometer-size Zn and Al dots on a sapphire substrate was accomplished by dissociating diethylzinc and trimethylaluminum using an optical near field on a sharpened optical fiber probe tip. The minimum diameters of the Zn and Al dots deposited were 37 and 25 nm, respectively, comparable with the apex diameter of the fiber probe. By changing the reactant molecules during deposition, nanometric Zn and Al dots were successively deposited on the same sapphire substrate with high precision. The distance between these dots was as short as 100 nm.

We demonstrated apertureless scanning near-field optical microscopy using a small protrusion (a simple 500-nm-diameter polystyrene particle) on a flat glass substrate as a probe. We designed a small sample stage to operate with the particle probe. It is a 40-µm-diameter circular stage, fabricated from an optical fiber by Hydrofluoric acid (HF) etching. In this paper, we present the first atomic force microscope and scanning near-field optical microscope images obtained with such a probe. We also discuss schemes for probe-sample distance control in this novel form of apertureless scanning near-field optical microscopy.

In OFDM-CDMA down link (base-to-mobile) transmissions, each user's transmit data symbol is spread over a number of orthogonal sub-carriers using an orthogonal spreading sequence defined in the frequency-domain. The radio propagation channel is characterized by a frequency- and time-selective multipath fading channel (which is called a doubly selective multipath fading channel in this paper). Frequency-domain equalization is necessary at the receiver to restore orthogonality among different users. This requires accurate estimation of the time varying transfer function of the multipath channel. Furthermore, the noise enhancement due to orthogonality restoration degrades transmission performance. In this paper, pilot-aided threshold detection combining (TDC) is presented that can effectively suppress the noise enhancement. If the estimated channel gain is smaller than the detection threshold, it is replaced with the detection threshold in the frequency equalization. There exists an optimal threshold that can minimize the bit error rate (BER) for a given received Eb/N0. The average BER performance of OFDM-CDMA down link transmissions using the TDC is evaluated by computer simulations. It is found that TDC using optimum detection threshold can significantly reduce the BER floor and outperforms DS-CDMA with ideal rake combining.

A postprocessing algorithm is presented for blocking artifact reduction in block-coded images using the adaptive filters along the pattern of neighborhood blocks. Blocking artifacts appear as irregular high-frequency components at block boundaries, thereby reducing the noncorrelation between blocks due to the independent quantization process of each block. Accordingly, block-adaptive filtering is proposed to remove such components and enable similar frequency distributions within two neighborhood blocks and a high correlation between blocks. This type of filtering consists of inter-block filtering to remove blocking artifacts at the block boundaries and intra-block filtering to remove ringing noises within a block. First, each block is classified into one of seven classes based on the characteristics of the DCT coefficient and MV (motion vector) received in the decoder. Thereafter, adaptive intra-block filters, approximated to the normalized frequency distributions of each class, are applied adaptively according to the various patterns and frequency distributions of each block as well as the filtering directions in order to reduce the blocking artifacts. Finally, intra-block filtering is performed on those blocks classified as complex to reduce any ringing noise without blurring the edges. Experimental tests confirmed the effectiveness of the proposed algorithm.

Deep submicron technology calls for new design techniques, in which wire and gate delays are accounted to have equal or nearly equal effect on circuit behavior. Asynchronous speed-independent (SI) circuits, whose behavior is only robust to gate delay variations, may be too optimistic. On the other hand, building circuits totally delay-insensitive (DI), for both gates and wires, is impractical because of the lack of effective synthesis methods. The paper presents a new approach for synthesis of globally DI and locally SI circuits. The method, working in two possible design scenarios, either starts from a behavioral specification called Signal Transition Graph (STG) or from the SI implementation of the STG specification. The method locally modifies the initial model in such a way that the resultant behavior of the system does not depend on delays in the input wires. This guarantees delay-insensitivity of the system-environment interface. The suggested approach was successfully tested on a set of benchmarks. Experimental results show that DI interfacing is realized with a relatively moderate cost in area and speed (costs about 40% area penalty and 20% speed penalty).

This paper describes an automatic interface insertion scheme for in-system verification of algorithm models. To insert the interface, an algorithm model described in C is translated into another source code that includes the communication with hardware components in the target system to be validated with the algorithm model. The communication between the algorithm model and hardware components is achieved using transactors that perform transformation between access operations and bus cycle transactions. I/O terminal is introduced as an interface model to relate the transactions to access operations during the execution of the algorithm model, i.e., accesses to I/O terminals invoke bus cycle transactions in hardware and vice versa. An automatic interface insertion tool is developed using the source-to-source translation to identify the I/O terminals and insert interface function calls in the source code. The proposed automatic interface insertion scheme is validated by emulating several multimedia algorithms written in C on real target systems.

This paper presents efficient file management of a hard disk drive embedded digital satellite receiver. The digital broadcasting technology enables multimedia access via broadcasting systems. The amount of digital data to be processed is increased remarkably as compared to the previous analog broadcasting environments. The efficient digital data storage and management technology are discussed in this paper to cope with these changes. The DSR uses a new file system that is designed by considering disk cluster sizes and limited memories in the system, which is more appropriate than that of general Personal Computers. The proposed system enables us to watch broadcasting and to manage multimedia data efficiently.

DS/CDMA systems employing long-period PN sequences are becoming a widespread standard of wireless communication systems. However, fast acquisition of long-period PN sequences at a low hardware cost is conventionally a difficult problem. This paper proposes a new fast acquisition algorithm for a class of PN sequences, which includes m- and GMW sequences as special cases, and shows that the mean (correct) acquisition time can be considerably reduced under input SNR values well below those used in modern DS/CDMA systems. Its fast acquisition capability is based on a decomposition of long PN sequences into a number of short ones and achieves a significantly reduced code phase uncertainty of acquisition at relatively small hardware cost. It can be applied as a (part of) acquisition system of a DS/CDMA system instead of a slow sliding correlator or a costly matched filter.

Finding corresponding edges is considered being the most difficult part of edge-based stereo matching algorithms. Usually, correspondence for a feature point in the first image is obtained by searching in a predefined region of the second image, based on epipolar line and maximum disparity. Reduction of search region can increase performances of the matching process, in the context of execution time and accuracy. Traditionally, hierarchical multiresolution techniques, as the fastest methods are used to decrease the search space and therefore increase the processing speed. Considering maximum of directional derivative of disparity in real scenes, we formulated some relations between maximum search space in the second images with respect to relative displacement of connected edges (as the feature points), in successive scan lines of the first images. Then we proposed a new matching strategy to reduce the search space for edge-based stereo matching algorithms. Afterward, we developed some fast stereo matching algorithms based on the proposed matching strategy and the hierarchical multiresolution techniques. The proposed algorithms have two stages: feature extraction and feature matching. We applied these new algorithms on some stereo images and compared their results with those of some hierarchical multiresolution ones. The execution times of our proposed methods are decreased between 30% to 55%, in the feature matching stage. Moreover, the execution time of the overall algorithms (including the feature extraction and the feature matching) is decreased between 15% to 40% in real scenes. Meanwhile in some cases, the accuracy is increased too. Theoretical investigation and experimental results show that our algorithms have a very good performance with real complex scenes, therefore these new algorithms are very suitable for fast edge-based stereo applications in real scenes like robotic applications.

Adaptive prediction iterative channel estimation is presented for combined antenna diversity and coherent rake reception of direct sequence spread spectrum (DSSS) signals. Its first stage uses pilot-aided adaptive prediction channel estimation, while the succeeding iteration stages use decision feedback and moving average filtering for channel re-estimation. The bit error rate (BER) performance of DSSS signal computer simulations evaluate transmission in a frequency selective Rayleigh fading channel. It is found that the adaptive prediction iterative channel estimation is superior to the non adaptive iterative channel estimation using the conventional weighted multi-slot averaging (WMSA) filtering at the first iteration stage, particularly in a fast fading channel.

Performance evaluation criterion is one of the most important issues for design of network traffic control mechanisms and algorithms. Due to multiple performance objectives of network traffic control, performance evaluation criteria must include multiple performance metrics executed simultaneously, which is called integrated performance evaluation criteria. In this paper, we analyze various performance metrics of network traffic control, and propose three integrated performance evaluation criteria. One is the improvement on original Power formula; our new Power formula is based on the multi-service-class model. Another is about the fairness of user's QoS (Quality of Service) requirements (queuing delay and loss rate); especially the detailed discussion on Proportional Fairness Principle is given. And the third one is the integration of preceding two, in which the throughput, queuing delay, packet loss rate, and the fairness are considered simultaneously.

When M-ary QAM (MQAM) signals experience the Rician fading channels, diversity schemes can minimize the effects of these fadings since deep fades seldom occur simultaneously during the same time intervals on two or more paths. The symbol error probability of MQAM systems using L-branch maximum ratio combining (MRC) diversity reception is derived theoretically over frequency-nonselective slow Rician fading channels with an additive white Gaussian noise (AWGN). This derived evaluation is expressed as the infinite series composed of hypergeometric and gamma functions. These performance evaluations allow designers to determine M-ary modulation methods for Rician fading environments.

Model checking is a technique that can make a verification for finite state systems absolutely automatic. We propose a method for automatic verification of fault-tolerant concurrent systems using this technique. Unlike other related work, which is tailored to specific systems, we are aimed at providing an approach that can be used to verify various kinds of systems against fault tolerance. The main obstacle in model checking is state explosion. To avoid the problem, we design this method so that it can use a symbolic model checking tool called SMV (Symbolic Model Verifier). Symbolic model checking can overcome the problem by expressing the state space and the transition relation by Boolean functions. Assuming that a system to be verified is modeled as a guarded command program, we design a modeling language and propose a translation method from the modeling language to the input language of SMV. We show the results of applying the proposed method to various examples to demonstrate the feasibility of the method.

Autonomous distributed manufacturing systems (ADMS) consist of multiple intelligent components with each component acting according to its own judgments. The ADMS objective is to realize more agile and adaptive manufacturing systems. This paper presents the introduction of context-dependent agents (CDAs) in ADMS that switch strategies depending on system conditions to achieve better performance than can be realized by agents that use the same strategies under all system conditions. For the real-time job scheduling problem, the paper presents a basic CDA architecture and the results of an extensive empirical evaluation of its performance relative to other rule-based schemes based on several common indices for real-time dispatch.