Shuichi Itoh

A wavelet transform-based ECG compression method guaranteeing desired signal quality

This paper presents a new electrocardiogram (ECG) compression method based on orthonormal wavelet transform and an adaptive quantization strategy, by which a predetermined percent root mean square difference (PRD) can be guaranteed with high compression ratio and low implementation complexity.

Irregular sampling theorems for wavelet subspaces

From the Paley-Wiener 1/4-theorem, the finite energy signal f(t) can be reconstructed from its irregularly sampled values f(k+/spl delta//sub /spl kappa//) if f(t) is band-limited and sup/sub /spl kappa//|/spl delta//sub /spl kappa//|<1/4. We consider the signals in wavelet subspaces and wish to recover the signals from its irregular samples by using scaling functions. Then the method of estimating the upper bound of sup/sub /spl kappa//|/spl delta//sub /spl kappa//| such that the irregularly sampled signals can be recovered is very important. Following the work done by Liu and Walter (see J. Fourier Anal. Appl., vol.2, no.2, p.181-9, 1995), we present an algorithm which can estimate a proper upper bound of sup/sub /spl kappa//|/spl delta//sub /spl kappa//|. Compared to Paley-Wiener 1/4-theorem, this theorem can relax the upper bound for sampling in some wavelet subspaces.

On sampling in shift invariant spaces

A necessary and sufficient condition for sampling in the general framework of shift invariant spaces is derived. Then this result is applied, respectively, to the regular sampling and the perturbation of regular sampling in shift invariant spaces. A simple necessary and sufficient condition for regular sampling in shift invariant spaces is attained. Furthermore, an improved estimate for the perturbation is derived for the perturbation of regular sampling in shift invariant spaces. The derived estimate is easy to calculate, and shown to be optimal in some shift invariant spaces. The algorithm to calculate the reconstruction frame is also presented.

A hierarchical group key management scheme for secure multicast increasing efficiency of key distribution in leave operation

This paper proposes an efficient protocol and associate algorithm for group key management in secure multicast. This protocol is based on a hierarchy approach in which the group is logically divided into subgroups. The group key is organized using member secrets assigned to each member and server secrets assigned to each subgroup, and the inverse value of the member secrets are also used to manage the group key when a member leaves. In this case, each member in a single subgroup needs to store the inverse values of the other members in that subgroup with the exception of its own. When a member joins the group, after updating the previous group key in the server, the new key is sent to all existing group members, and the inverse value of the new member is sent to subgroup members (where there is a join), by exploiting IP multicast. Most importantly, the server just sends the inverse value of the leaving member to the subgroups when a member leaves. Then, the group key is updated by each remaining member in the subgroups by using that inverse value. Consequently, the benefits are two-fold. First, only one key needs to be generated by the server at each event. Second, not only the computational overhead is reduced but also new key information can be multicast to all members simultaneously. This paper describes the details of our novel protocol and the related algorithm.

A coded convolutional spreading CDMA system with turbo equalization for downlink transmission over a frequency selective fading channel

In this paper, a coded convolutional spreading codedivision multiaccess with cyclic prefix (CS-CDMA/CP) system in conjunction with iterative receivers is proposed for synchronous downlink transmission over frequency selective fading channels and its performance is compared with the uncoded CS-CDMA/CP employing maximum-likelihood sequence estimation (MLSE) receiver as well as with the conventional coded direct sequence CDMA (DS-CDMA) employing (maximal ratio combining-) MRC-RAKE. Contrary to the uncoded CSCDMA/ CP system which suffers from performance degradation at low signal-to-noise power ratios (SNRs), it is demonstrated that the proposed scheme can attain almost the full path diversity gain over all SNRs with single-user complexity. Compared with the coded DS-CDMA system with single-user receivers, the proposed system is free from multiuser interference (MUI) whenever the multipath delay of the channel does not exceed the designed maximum delay. It is also demonstrated, moreover, that the proposed system shows a robust performance even if the channel length exceed the designed maximum delay slightly. Because of the subblock structure of CS-CDMA/CP, the proposed system can utilize time-diversity effects, when the channel subjects fast fading, and this greatly improves the resultant performance. Finally, it is shown that the receiver complexity of the proposed system is compared quite favorably with the iterative multiuser receivers for coded DS-CDMA systems of comparable performance.

WAVELET SAMPLING THEOREMS FOR IRREGULARLY SAMPLED SIGNALS

SUMMARY A formula for recovering the original signal from itsirregularly sampled values using wavelets, which extendsthe Walter sampling theorem to the irregular sampling caseand generalizes the PaleyŒWiener 1/4-Theorem by remov-ing the symmetricity constraint for sampling, is pre-sented.a 1999 Scripta Technica, Electron Comm Jpn Pt 3,82(5): 65Œ71, 1999Key words: Wavelet; sampling theorem; scalingfunction; orthogonality; biorthogonality. 1. Introduction In digital signal and image processing, digital com-munications, and so forth, a continuous signal is usuallyrepresented and processed by using its discrete samples.How, then, are we to reconstruct the original signal from itsdiscrete samples? The classical Shannon sampling theoremgives the following formula for band-limited finite energysignals.For a finite energy s-band continuous signalf( t), 2t ˛ R , that is, supp f^(w) I [- s , s] and f ˛ L (R), it canbe recovered by the formulawhere f^ is the Fourier transform of f(t) defined byIf we let s =

A Dense Mode Ad hoc Multicast Routing Protocol Constructing Shortest Path Trees with Low Control Overhead

In recent years, an ad hoc network is paid to attention widely, and many routing protocols are studied actively not only for unicasting but also for multicasting. Ad hoc multicast communication can be applied to a many-to-many conference among vehicles. Here, it is required to reduce the number of hops in the multicast data delivery and reduce the control message overhead, in order to save wireless channel bandwidth. From this requirement, it is considered that the dense mode multicast routing with low control overhead is appropriate for ad hoc many-to-many conference application. In this paper, we propose a new ad hoc multicast routing protocol, which constructs the shortest path tree efficiently and guarantees the operation of dense mode such as the broadcast & prune. This paper describes the result of designing our multicast routing protocol and that of performance evaluation in terms of control message overhead

An algorithm for designing a pattern classifier by using MDL criterion

The algorithm for designing a pattern classifier, which uses MDL criterion and a binary data structure, is proposed. The algorithm gives a partitioning of the space of the K-dimensional attribute and gives an estimated probability model for this partitioning. The volume of bins in this partitioning is asymptotically upper bounded by /spl Oscr/((log N/N)/sup K/(K+2/)/sup )/ for large N in probability, where N is the length of training sequence. The redundancy of the code length and the divergence of the estimated model are asymptotically upper bounded by /spl Oscr/(K(log N/N)/sup 2/(K+2/)/sup )/. The classification error is asymptotically upper bounded by /spl Oscr/(K/sup 1/2/(log N/N)/sup 1/(K+2/)/sup )/.

Method of predicting number of on-demand video requests using time series data for video cache system

We propose a method of predicting the number of requests for video titles in an on-demand video delivery system considering their time dependency. To handle many heterogeneous video requests in a video streaming delivery network system using video servers, it is effective to introduce video caching systems in the network system. For the cache system design in video delivery network systems, an effective cache algorithm for predicting how many requests will occur in the future is needed. Since almost all such proposed algorithms are for WWW systems, they do not consider the time dependency of the number of requests, so they are not applicable to a video system with time-dependent requests because a customer in the system watches one video title just one time. In our method, the number of requests is represented by a function of time by considering how a customer obtains information about a video and requests it and by considering that a customer requests each video only once. We have developed a method of calculating the coefficients of the function from the series of the number of requests and for estimating the number of requests in the future. We evaluated the convergence and calculation time. The results show that the calculations converge and the calculation time is 31 ms. They also show that the calculation cost is acceptable for a general video delivery system.

Wavelet transform based ECG data compression with desired reconstruction signal quality

This paper proposes a new coding strategy by which the desired quality of reproduced signal can be guaranteed with the minimum cost of coding rate. The idea was successfully introduced to the DOWT-based coding system for the ECG compression application.