Since any suggestion to regional services are not described in Kerberos, authentication between regions can be performed via PKINIT (Public Key Cryptography for Initial Authentication) presented by IETF (Internet Engineering Task Force) CAT working group. In this paper, an efficient Kerberos authentication mechanism associated with X.509 and Domain Name system (DNS) is presented by employing the two distinct key management systems - asymmetric and symmetric methods. A new protocol is better than the authentication mechanism proposed by IETF CAT Working group in terms of communication complexity.

It is widely known that the family of projection filters includes the generalized inverse filter, and that the family of parametric projection filters includes parametric generalized projection filters. However, relations between the family of parametric projection filters and constrained least squares filters are not sufficiently clarified. In this paper, we consider relations between parameter estimation and image restoration by these families. As a result, we show that the restored image by the family of parametric projection filters is a maximum penalized likelihood estimator, and that it agrees with the restored image by constrained least squares filter under some suitable conditions.

A new modified maximum likelihood (ML) algorithm for frame synchronization in discrete multitone VDSL transmission system is presented. Computer simulation results are included to show its improvement in Et/N0 of each tone in the received data. This algorithm estimates the frame boundary at the initial transition edge rather than at the middle peak of a shortened twisted-pair channel response. The timing margin degradation caused by precursor intersymbol interference (ISI) can be reduced significantly, especially at the sub-channel loaded with more bits.

This paper presents a child verb learning model mainly based on syntactic bootstrapping. The model automatically learns 4-5-year-old children's linguistic knowledge of verbs, including subcategorization frames and thematic roles, using a text in dialogue format. Subcategorization frame acquisition of verbs is guided by the assumption of the existence of nine verb prototypes. These verb prototypes are extracted based on syntactic bootstrapping and some psycholinguistic studies. Thematic roles are assigned by syntactic bootstrapping and other psycholinguistic hypotheses. The experiments are performed on the data from the CHILDES database. The results show that the learning model successfully acquires linguistic knowledge of verbs and also suggest that psycholinguistic studies of child verb learning may provide important hints for linguistic knowledge acquisition in natural language processing (NLP).

The current paper proposes a new method for reducing the computational overhead of fine-to-coarse multi-resolution motion estimation (MRME) on the finest resolution level based on limiting the search region used to consider the motion vectors from the coarsest resolution subband. Half-pel accuracy motion estimation (HPAME) is used in the baseband to achieve an exact motion vector, which has a significant influence on the reconstructed image. However, since this method involves a high computational overhead, the use of selective interpolation is suggested to reduce the computational overhead. The proposed method uses HPAME to estimate exact motion vectors in the baseband, then based on the characteristics of these motion vectors, the motion vectors in the higher frequency subbands are selectively estimated. That is, motion vectors in the higher frequency subbands are only estimated for those blocks with half-pixel accuracy motion vectors in the baseband. Experimental results show that the proposed algorithm can produce better image quality results than the conventional algorithms.

Sports scheduling concerns how to construct a schedule of a sports competition mathematically. Many sports competitions are held as round-robin tournaments. In this paper, we consider a particular class of round-robin tournaments. We report some properties of round-robin tournaments and enumerate home-away tables satisfying some practical requirements by computer search.

The advances in services using the present Internet mean that there will be increasing demand for Video on Demand (VoD) on the Internet in the near future. However, because of the best-effort characteristics of the Internet, it is important to suppress the degradation of communication quality caused by packet dropping when Internet traffic is congested. This paper focuses on MPEG transmission over the Internet, and suitable control mechanisms are established for an acceptable Quality of Service (QoS) improvement through detailed evaluation. Packets are classified using a frame-based scheme. The server applies the proposed End-to-End control scheme and shuffles the order of packets to avoid burst dropping, and may omit selected packets belonging to certain frames prior to forwarding. At the intermediate routers, transferred packets are transmitted according to Round Robin (RR) or Weighted Round Robin (WRR) scheduling, and are dropped statistically using selective Random Early Detection (RED) corresponding to frame attributes when there is congestion. We evaluate the proposed performance of transmission method using both computer simulations and empirical measurements of picture quality. The results show that when the traffic volume cannot be estimated in the intermediate routers, the combined use of RR, shuffling and conditional RED is effective, and when the traffic volume can be estimated, the combination of WRR, rate control and RED is effective.

This paper presents effective methods to calculate dual frame of the short-time Fourier expansion (STFE) in l2(Z). Based on a relationship between the prototype window used for generating a frame and the dual prototype window used for generating a dual frame in the STFE, two useful numerical methods with a finite frame operator are proposed to obtain finite support dual frames in time domain formulation. The methods can be used to construct the multiple STFE (MSTFE) suitable for a time-frequency analysis, synthesis and coding of discrete-time nonstationary signals. Numerical simulation results are given to verify the effectiveness of the calculation of dual frame.

In this paper, a new family of interconnection networks which we call the Incrementally Extensible Twisted Cube (IETQ) is proposed. The topology of this network is a novel generalization of the twisted cube. It inherits all the merits but without the limitations owned by a twisted cube. First, this proposed IETQ is incrementally extensible and can be adapted for use in any number of nodes; therefore, this network is particularly well suited for the design of a distributed communication network with an arbitrary number of nodes. Second, the vertex connectivity of IETQ is n. Measured by this vertex connectivity, we demonstrate that this network is optimally fault-tolerant . And it is almost regular, because the difference between the maximum and minimum degree of any node in an IETQ is at most one. A shortestpath routing algorithm for IETQ is proposed to generate path for any given pair of vertices in the network. Third, comparing with most of the other competitors, the diameter of this IETQ network is only half in size. This low diameter helps to reduce the internode communication delay. Moreover, IETQ also possesses the property of a pancyclic network. This attractive property would enable us to map rings of any length into the proposed network.

Practical image restoration filters usually include a parameter that controls regularizability, trade-off between fidelity of a restored image and smoothness of it, and so on. Many criteria for choosing such a parameter have been proposed. However, the relation between these criteria and the squared error of a restored image, which is usually used to evaluate the restoration performance, has not been theoretically substantiated. Sugiyama and Ogawa proposed the subspace information criterion (SIC) for model selection of supervised learning problems and showed that the SIC is an unbiased estimator of the expected squared error between the unknown model function and an estimated one. They also applied it to restoration of images. However, we need an unbiased estimator of the unknown original image to construct the criterion, so it can not be used for general situations. In this paper, we present a modified version of the SIC as a new criterion for choosing a parameter of image restoration filters. Some numerical examples are also shown to verify the efficacy of the proposed criterion.

In reuse of the VLSI layout design when technology migration takes place, the information to be abstracted from the original design and the data structure to store the information shall be specified. In this paper, they are assumed as the seg-based 4-direction and the parametric BSG, respectively. The parametric BSG is a BSG whose segs are generalized to take any number of units of length. The seg-based 4-direction is the right-of, left-of, above, and below relations between two rooms in accordance with the segs between them. An elegant procedure is given to map the floorplan of the model into a parametric BSG of the minimum size, keeping the abstracted seg-based 4-direction. Merits of the PBSG are discussed and a way of reuse is suggested by illustrative instances. Finally, a superior potential of the parametric BSG as the data structure is discussed empirically.

Implementation of Multi-Input Multi-Output (MIMO) channel sounder is considered, taking hardware cost and realtime measurement into account. A remarkable difference between MIMO and conventional Single-Input Multi-Output (SIMO) channel sounding is that the MIMO sounder needs some kind of multiplexing to distinguish transmitting antennas. We compared three types of multiplexing TDM, FDM, and CDM for the sounding purpose, then we chose FDM based technique to achieve cost effectiveness and realtime measurement. In the framework of FDM, we have proposed an algorithm to estimate MIMO channel parameters. Furthermore the proposed algorithm was implemented into the hardware, and the validity of the proposed algorithm was evaluated through measurements in an anechoic chamber.

We have studied an image acquisition system for a real-time image- based rendering (IBR) system. In this area, most conventional systems sacrifice spatial or temporal resolution for a large number of input images. However, only a portion of the image data is needed for rendering, and the portion required is determined by the position of the imaginary viewpoint. In this paper, we propose an acquisition system for a real-time image-based rendering system that uses pixel-based random-access image sensors to eliminate the main bottleneck in conventional systems. We have developed a prototype CMOS image sensor, which has 128 128 pixels. We verified the prototype chip's selective readout function. We also verified the sample & hold feature.

We have designed the Half Adder (HA) circuit and the Carry Save Serial Adder (CSSA) circuit based on pipeline architecture. Our HA has the structure of a two-stage pipeline and consists of 160 Josephson Junctions (JJs). Our CSSA has the structure of a four-stage pipeline with a feedback loop and consists of 360 JJs. These circuits were fabricated by the NEC standard process. There are two issues which should be considered in the design. One is parameter spreads generated by the fabrication process and the other is leakage currents between the gates. We have introduced a parameter optimization method to deal with the parameter spreads. We have also inserted three stages of JTLs to reduce leakage currents. We have experimentally confirmed the correct operations of these circuits. The obtained bias margins were 33.1% for the HA and 24.6% for the CSSA.

Suppose that there are players in two hierarchical groups and a computationally unlimited eavesdropper. Using a random deal of cards, a player in the higher group wishes to send a one-bit message information-theoretically securely either to all the players in her group or to all the players in the two groups. This can be done by the so-called 2-level key set protocol. In this paper we give a necessary and sufficient condition for the 2-level key set protocol to succeed.

A method of learning for multi-layer artificial neural networks is proposed. The learning model is designed to provide an effective means of escape from the Backpropagation local minima. The system is shown to escape from the Backpropagation local minima and be of much faster convergence than simulated annealing techniques by simulations on the exclusive-or problem and the Arabic numerals recognition problem.

Several gateway-based congestion control mechanisms have been proposed to support an end-to-end congestion control mechanism of TCP (Transmission Control Protocol). One of promising gateway-based congestion control mechanisms is a RED (Random Early Detection) gateway. Although effectiveness of the RED gateway is fully dependent on a choice of control parameters, it has not been fully investigated how to configure its control parameters. In this paper, we analyze the steady state behavior of the RED gateway by explicitly modeling the congestion control mechanism of TCP. We first derive the equilibrium values of the TCP window size and the buffer occupancy of the RED gateway. Also derived are the stability condition and the transient performance index of the network using a control theoretic approach. Numerical examples as well as simulation results are presented to clearly show relations between control parameters and the steady state behavior.

We present the new 128-bit block cipher called Camellia. Camellia supports 128-bit block size and 128-, 192-, and 256-bit key lengths, i.e. the same interface specifications as the Advanced Encryption Standard (AES). Camellia was carefully designed to withstand all known cryptanalytic attacks and even to have a sufficiently large security leeway. It was also designed to suit both software and hardware implementations and to cover all possible encryption applications that range from low-cost smart cards to high-speed network systems. Compared to the AES finalists, Camellia offers at least comparable encryption speed in software and hardware. An optimized implementation of Camellia in assembly language can encrypt on a Pentium III (1.13 GHz) at the rate of 471 Mbits per second. In addition, a distinguishing feature is its small hardware design. A hardware implementation, which includes encryption, decryption, and the key schedule for 128-bit keys, occupies only 9.66 K gates using a 0.35 µm CMOS ASIC library. This is in the smallest class among all existing 128-bit block ciphers. It perfectly meets the current market requirements in wireless cards, for instance, where low power consumption is essential.

Grouping multiple voice frames into a single IP packet ("frame grouping") is a commonly mentioned approach to saving bandwidth in IP telephony. But little is known as to when, how, and how much frame grouping should be done in Internet environment. This paper explores the feasibility and the methods of frame grouping based on Internet delay measurement. Specifically, we propose an adaptive frame grouping method that minimizes the delay violation while reducing the bandwidth usage by as much as a factor of two under real Internet delay fluctuations. The performance of the method is evaluated as it is used against a single voice stream and then against multiple voice streams.

In order to assess the possible impacts of meteors with spacecraft, which is among major hazard in the space environment, it is essential to establish an accurate statistics of their mass and velocity. We developed a radar-optical combined system for detecting faint meteors consisting of a powerful VHF Doppler radar and an ICCD video camera. The Doppler pulse compression scheme is used to enhance the S/N ratio of the radar echoes with very large Doppler shifts, as well as to determine their range with a resolution of 200 m. A very high sensitivity of more than 14 magnitude and 9 magnitude for radar and optical sensors, respectively, has been obtained. Instantaneous direction of meteor body observed by the radar is determined with the interferometry technique. We examined the optimum way of the receiving antenna arrangements, and also of the signal processing. Its absolute accuracy was confirmed by the optical observations with background stars as a reference. By combining the impinging velocity of meteor bodies derived by the radar with the absolute visual magnitude determined by the video camera simultaneously, the mass of each meteor body was estimated. The developed observation system will be used to create a valuable data base of the mass and velocity information of faint meteors, on which very little is known so far. The data base is expected to play a vital role in our understanding of the space environment needed for designing large space structures.