The instruction set architecture of MBP-light, a dedicated processor for the DSM (Distributed Shared Memory) management of JUMP-1 is analyzed with a real prototype. The Buffer-Register Architecture proposed for MBP-core improves performance with 5.64% in the home cluster and 6.27% in a remote cluster. Only a special instruction for hashing cluster address is efficient and improves the performance with 2.80%, but other special instructions are almost useless. It appears that the dominant operations in the DSM management program were handling packet queues assigned into the local cluster. Thus, common RISC instructions, especially load/store instructions, are frequently used. Separating instruction and data memory improves performance with 33%. The results suggest that another alternative which provides separate on-chip cache and instructions dedicated for packet queue management is advantageous.

We demonstrated the uniformity and stability as well as the high breakdown voltage of 0.1-µm-gate InP HEMTs with a double recess structure. To overcome the drawbacks regarding the uniformity and stability in the double recess structure, an InP passivation layer that functions as an etch-stopper and a surface passivator was successfully applied to the structure. It was confirmed that there was no degradation in the uniformity and stability of device performance for the double recess HEMTs that had the breakdown voltages in the on-state and off-state improved by a factor of 1.6.

Knudsen et al. proposed an efficient method based on a tree-search algorithm with recursive process for reconstructing the internal state of RC4 stream cipher. However, the method becomes infeasible for word size n > 5 because its time complexity to reconstruct the internal state is too large. This letter proposes a more efficient method than theirs. Our method can reconstruct the internal state by using the pre-known internal-state entries, which are fewer than their method.

Suica is our contact-less IC card's nickname: Super Urban Intelligent CArd. There are two types of IC Card: One for Suica IO (SF) Card and the other for Suica Commuter Pass, which has a function of stored fare card and commuter pass. There are 6.54 million Suica holders (about 3.33 million Suica Season Pass holders and 3.21 million Suica IO Card holders) as of 16, June 2003.

This study investigate the rectangular microstrip patch antenna on anisotropy substrates with superstrate and air gap, based on rigorous full-wave analysis and Galerkin's moment method. Results show that radiation patterns with varying air gap, permittivity of the superstrate and substrate, and thickness of the superstrate can be determined and analyzed.

The general public is expected to demand in not too distant future instituting more stringent certification procedures for computing parts of traditional and new-generation safety-critical application systems. Such quality-of-service (QoS) certification processes will not and can not rely solely on the testing approach. Design-time guaranteeing of timely service capabilities of various subsystems is an inevitable part of such processes. Although some promising developments in this area have been occurring in recent years, the technological challenges yet to be overcome are enormous. This paper is a summary of the author's perspective on the remaining challenges and promising directions for tackling them.

Multipath is a big problem for TCP traffic in traffic engineering. To solve it, hash functions such as CRC-16 are usually applied over source and destination address segments in packet headers. Through simulations and performance comparison of several multipath algorithms, it is found out that high network utilization achieved by using hash functions is at the expense of low fairness among coexisting TCP flows. It is also illustrated that packet size has significant influence on performance.

Security, flexibility, and scalability are critical to the success of wireless communications. Wireless networks with movable base stations combine the advantages of mobile ad hoc networks and wireless LAN to achieve these goals. Hierarchical mobile wireless network (HMWN) is proposed for supporting movable base stations. In such a system, mobile hosts are organized into hierarchical groups. The group agents serve as a distributed trust entity. A secure packet forwarding algorithm and an authentication and key exchange protocol are developed to protect the network infrastructure. A roaming support mechanism and the associated mutual authentication protocol are proposed to secure the foreign group and the mobile host when it roams within the network. The computation overhead of secure packet forwarding and roaming support algorithms is studied via experiments. The results demonstrate that these two security mechanisms only require, respectively, less than 2% and 0.2% to 5% CPU time in a low-end 700 MHz PC.

A Time Hopping Pulse Spacing Modulation (TH-PSM) system, which combines the pulse position modulation system with code shift keying, is proposed. The following performances are analyzed; (1) data transmission rate, (2) error rate in a single-user case, (3) error rate in a multi-user case, and (4) spectral efficiency. Consequently, the data transmission rate of the proposed system is higher than that of the conventional Spread Spectrum Pulse Position Modulation (SS-PPM) system. The proposed system can improve the probability of block error by increasing the number of information bits per spreading code. Moreover, the spectral efficiency of the proposed system is higher than that of the conventional system. The proposed system is more attractive than the conventional SS-PPM system for optical communications, power-line communications, and UWB communications.

Nishiara and Morita defined an i.i.d. word-valued source which is defined as a pair of an i.i.d. source with a countable alphabet and a function which transforms each symbol into a word over finite alphabet. They showed the asymptotic equipartition property (AEP) of the i.i.d. word-valued source and discussed the relation with source coding algorithm based on a string parsing approach. However, their model is restricted in the i.i.d. case and any universal code for a class of word-valued sources isn't discussed. In this paper, we generalize the i.i.d. word-valued source to the ergodic word-valued source which is defined by an ergodic source with a countable alphabet and a function from each symbol to a word. We show existence of entropy rate of the ergodic word-valued source and its formula. Moreover, we show the recurrence time theorem for the ergodic word-valued source with a finite alphabet. This result clarifies that Ziv-Lempel code (ZL77 code) is universal for the ergodic word-valued source.

This paper presents two different algorithms for random number generation. One algorithm generates a random sequence with an arbitrary distribution from a sequence of pure random numbers, i.e. a sequence with uniform distribution. The other algorithm generates a sequence of pure random numbers from a sequence of a given i.i.d. source. Both algorithms can be regarded as an implementation of the interval algorithm by using the integer arithmetic with limited precision. We analyze the approximation error measured by the variational distance between probability distributions of the desired random sequence and the output sequence generated by the algorithms. Further, we give bounds on the expected length of input sequence per one output symbol, and compare it with that of the original interval algorithm.

Relative time-stamping schemes prove the chronological sequence of digital documents and their integrity. Since the chronological sequence is verified by tracing the link between two timestamps, it is desirable that the length of the verification path is short. Buldas, Laud, Lipmaa, and Villemson have proposed the relative time-stamping scheme based on the binary link. In this paper, we extend the binary link to the ternary link, and apply it to the relative time-stamping scheme. We show that the maximum length of the verification path of the proposed scheme is shorter than that of the previous scheme. Moreover, we show that the average length of the proposed scheme is shorter than that of the previous scheme. Thus, the proposed time-stamping schemes is more efficient than the previous scheme.

This report describes face image recognition by 2-dimensional discrete Walsh transform and multi-layer neural networks. Neural network (NN) is one of the powerful tools for pattern recognition. In the previous researches of face image recognition by NN, the gray levels on each pixel of the face image have been used for input data to NN. However, because the face image has usually too many pixels, a variety of approaches have been required to reduce the number of the input data. In this research, 2-dimensional discrete Walsh transform is used for reduction of input data and the recognition is done by multi-layer neural networks. Finally, the validity of our method is varified.

Automatic image inspector inspects the quality of printed circuit boards using image-processing technology. In this study, we change an automatic inspection problem into a problem for detecting the signal singularities. Based on the wavelet theory that the wavelet transform can focus on localized signal structures with a zooming procedure, a novel singularity detection and measurement algorithm is proposed. Singularity positions are detected with the local wavelet transform modulus maximum (WTMM) line, and the Lipschitz exponent is estimated at each singularity from the decay of the wavelet transform amplitude along the WTMM line. According to the theoretical analysis and computer simulation results, the proposed algorithm is shown to be successful for solving the automatic inspection problem and calculating the Lipschitz exponents of signals. These Lipschitz exponents successfully characterize singular behavior of signals at singularities.

This paper assesses the media synchronization quality of recovery control schemes from asynchrony, which are referred to as reactive control schemes here, in terms of objective and subjective measures. We deal with four reactive control techniques: skipping, discarding, shortening and extension of output duration, and virtual-time contraction and expansion. We have carried out subjective and objective assessment of the media synchronization quality of nine schemes which consist of combinations of the four techniques. The paper makes a comparison of media synchronization quality among the schemes. It also clarifies the relations between the two kinds of quality measures.

Ranking fuzzy numbers is one of very important research topics in fuzzy set theory because it is a base of decision-making in applications. However, fuzzy numbers may not be easily ordered into one sequence according to their magnitudes because they represent uncertain values. When two fuzzy numbers overlap with each other, a fuzzy number may not be considered absolutely larger than the other. That is, even when a fuzzy number may be considered larger than the other, it may also be considered smaller than the other. It means that for a given set of fuzzy numbers, several ranking sequences possibly exist. However, most of the existing ranking methods produce only one ranking sequence. They ignore other possible sequences due to the overlap between fuzzy numbers. We propose a ranking method which generates possible ranking sequences of given fuzzy numbers. Our method takes a viewpoint from users, and uses it for evaluation of fuzzy numbers. Fuzzy numbers will be ranked based on the evaluations and a fuzzy set of sequences of fuzzy numbers will be produced as a ranking results. Numeric examples and comparisons with other methods are also presented.

Broadcast disks are suited for disseminating information to a large number of clients in mobile computing environments. In broadcast disks, the server continuously and repeatedly broadcasts all data items in the database to clients without specific requests. The clients monitor the broadcast channel and read data items as they arrive on the broadcast channel. The broadcast channel then becomes a disk from which clients can read data items. In this paper, we propose a cache conscious concurrency control (C4) algorithm to preserve the consistency of read-only client transactions, when the values of broadcast data items are updated at the server. The C4 algorithm is novel in the sense that it can reduce the response time of client transactions with minimal control information to be broadcast from the server. This is achieved by the judicious caching strategy of the client and by adjusting the currency of data items read by the client.

Space-time transmit diversity (STTD) and space-time block coding (STBC) are attractive techniques for high bit-rate and high capacity transmission. The concatenation scheme of turbo codes and STBC (Turbo-STBC) was proposed and it has been shown that the Turbo-STBC can achieve the good error rate performance. Recently, low-density parity-check (LDPC) codes have attracted much attention as the good error correcting codes achieving the near Shannon limit performance like turbo codes. The decoding algorithm of LDPC codes has less complexity than that of turbo codes. Furthermore, when the block length is large, the error rate performance of the LDPC codes is better than that of the turbo codes with almost identical code rate and block length. In this letter, we propose a concatenation scheme of LDPC codes and STBC. We refer to it as the LDPC-STBC. We evaluate the error rate performance of the LDPC-STBC by the computer simulation and show that the error rate performance of the LDPC-STBC is almost identical to or better than that of the Turbo-STBC in a flat Rayleigh fading channel.

In this paper, a new Hierarchical Sum of Double Difference metric, HSDD, is introduced. It is shown, as opposed to conventional Sum of Absolute Difference (SAD) metric, how this zerotree coding aware metric can jointly constrain the motion vector searching for both temporal and spatial (quad-tree) directions under multiresolution motion estimation framework. The reward from the temporal-spatial co-optimization concept of HSDD is that fewer bits are spent later for describing the isolated zeros. The embedded wavelet video coder using HSDD metric was tested with a set of video sequences and the compression performance seems to be promising.

Measuring the duration of flow of a TCP connection in an end-to-end path is important in the management of network performance, and when this is done, an administrator can manage the quality of the networks using the α percentile of the distribution. We propose a method of estimating the distribution of flow duration in an end-to-end path through active measurement using a small degree of traffic. This method of estimation is based on traffic characteristics that are observed in measuring traffic in actual networks. It imposes little additional load on networks and the time in computation required to estimate the distribution is also short. The distribution to be estimated is assumed as a log-normal distribution, and the mean and variance of the distribution of a target file size is estimated by using results of active measurements. Means and variances in various file sizes are estimated through the linear relationships between these values (or their logarithms) and file size. We also provide numerical examples using actual traffic data.