An LSI has been fabricated and measured to demonstrate feasibility of VDD-hopping scheme in an embedded system level by executing MPEG4 CODEC. In the VDD-hopping, supply voltage of a processor is dynamically controlled by a hardware-software cooperative mechanism depending on workload of the processor. When the workload is about a half, the VDD-hopping is shown to reduce power to less than a quarter compared to the conventional fixed-VDD scheme. The power saving is achieved without degrading real-time features of MPEG4 CODEC.

In order to design oscillators and switches phase noise characteristic is the key to obtain high quality frequency spectrums. Since the phase noise is directly affected by the 1/f noise of transistors in the circuit, 1/f noise measurement and modeling are important. This paper describes 1/f noise measurement, frequency and bias dependent flicker noise model, and noise parameter extraction method of MOSFET's. Also, for MOSFET's geometry dependencies of drain current 1/f noise are analyzed and modeled. The model has been verified by measuring the noise current spectral density of MOSFET's in two different process devices.

In this paper, a new multi-engine architecture for the baseband modem LSI of W-CDMA systems is proposed. The developed test chip with this architecture is also presented. In the multi-engine architecture, processors and wired logic are combined to obtain both flexibility and low power dissipation. Multiple processors are used in the LSI to lower its operating frequency by distributed processing. A customized processor is used to lower the overhead of multiple processors in terms of LSI scale. The test chip was fabricated with a 0.25-µm process. Its measured power dissipation for simultaneous 384 kbit/s downlink reception and 64 kbit/s uplink transmission was 160 mW.

The jitter characteristics of synchronous residual time stamp (SRTS) method used in ATM adaptation layer type 1 (AAL1) are analyzed. In this letter, the root mean square amplitude of filtered SRTS jitter is calculated and the computer simulation has been carried out to show jitter of SRTS method considering also the phase time error of network clocks.

We introduce PC Linux cluster computing techniques to an Evolutionary Graph Generation (EGG) system, and successfully implement the parallel version of the EGG system, called PEGG. Our survey satisfactorily shows that the parallel evolutionary approach meets our expectation that the final solutions obtained from PEGG will be as good as or better than those obtained from EGG, and that PEGG can ultimately improve the speed of evolution.

With increased size and issue-width, instruction issue queue becomes one of the most energy consuming units in today's superscalar microprocessors. This paper presents a novel architectural technique to reduce energy dissipation of adaptive issue queue, whose functionality is dynamically adjusted at runtime to match the changing computational demands of instruction stream. In contrast to existing schemes, the technique exploits a new freedom in queue design, namely the voltage per access. Since loading capacitance operated in the adaptive queue varies in time, the clock cycle budget becomes inefficiently exploited. We propose to trade-off the unused cycle time with supply voltage, lowering the voltage level when the queue functionality is reduced and increasing it with the activation of resources in the queue. Experiments show that the approach can save up to 39% of the issue queue energy without large performance and area overhead.

A new approach on designing a finite field multiplier architecture is proposed. The proposed architecture trades reduction in the number of clock cycles with resources. This architecture features high performance, simple structure, scalability and independence on the choice of the finite field, and can be used in high security cryptographic applications such as elliptic curve crypto-systems in large prime Galois Fields (GF(2m)).

We have demonstrated active mode hopping suppression in external-cavity semiconductor lasers including a diffraction grating as a wavelength-selecting device. The feedback control nullifies the difference between the oscillation wavelength and selected wavelength based on observed changes in diffraction angle. The control has suppressed mode hopping over a 7.5 times wider span than without control. And when combined with conventional mode hopping suppression techniques, mode-hop-free oscillation is achieved over 130 nm. Our approach can be used for most Littman-type external-cavity semiconductor lasers with simple attachments; it will be useful for continuous wavelength sweeping and for long-term wavelength stabilization.

A tunable external-cavity InGaAs/AlGaAs quantum-well laser using a grating coupler monolithically integrated in a selectively disordered waveguide is demonstrated. The laser consists of an amplifier with a narrow channel for lateral single-mode guiding and a tapered section, a grating coupler for output beam collimation and wavelength dispersion, and an external half mirror. Selective quantum-well disordering technique using SiO2 caps of different thicknesses and rapid thermal annealing was employed to reduce the passive waveguide loss in the grating coupler region. Loss reduction from 40 cm-1 to 3 cm-1 was accomplished. Resultant increase of the grating coupler efficiency and expansion of the effective aperture length led to significant improvement of the laser performances. The maximum output power of 105 mW and wide tuning range of 21.1 nm centered at 997 nm were obtained. The well collimated output beam of full diffraction angles at half maximum of 0.16 0.18 was obtained.

Spatial dynamic pattern formations or trails by organisms attract us, which remind us chaos and fractal. They seem to show the emergence of co-operation, job separation, or division of territories when genetic programming controls the reproduction, mutation, crossing over of the organisms. Recent research in social insect behavior suggests that swarm intelligence comes from pheromone or chemical trails, and models based on self-organization can help explain how colony-level behavior emerges out of interactions among individual insects. We try to explain the co-operative behaviors of social insect by means of density of organisms and their interaction with environment in simple simulations. We also study that MDL-based fitness evaluation is effective for improvement of generalization of genetic programming. At last, interspecific and intraspecific mathematical models are examined to expand our research into interspecific evolution.

In this paper we addresses the problem of finding feasible solutions for the Group Multicast Routing Problem (GMRP). This problem is a generalization of the multicast routing problem whereby every member of the group is allowed to multicast messages to other members from the same group. The routing problem involves the construction of a set of low cost multicast trees with bandwidth requirements for all the group members in the network. We first prove that the problem of finding feasible solutions to GMRP is NP-complete. Following that we propose a new heuristic algorithm for constructing feasible solutions for GMRP. Simulation results show that our proposed algorithm is able to achieve good performance in terms of its ability of finding feasible solutions whenever one exist.

This paper describes the recent progress made in developing wavelength tunable semiconductor light sources for WDM applications. Wide and quasi-continuous wavelength tunings were investigated for a wavelength-selectable laser and a wavelength tunable distributed Bragg reflector (DBR) laser having a super structure grating (SSG). A wavelength-selectable laser consisting of a DFB laser array, a multi-mode interferometer (MMI), and a semiconductor optical amplifier (SOA) demonstrated a quasi-continuous tuning range of 46.9 nm by using temperature control. A wavelength-tunable DBR laser with SSG exhibited a quasi-continuous tuning range of 62.4 nm by using three tuning current controls. Wavelength stabilization was also demonstrated under the temperature variations of 5.

Generalized Pulse Spectrum Technique (GPST) is a method to solve the inverse problems of wave-propagation and diffusion-dominated phenomena, and therefore has been popularly applied in image reconstruction of time-resolved diffuse optical tomography. With a standard GPST for simultaneous reconstruction of absorption and scattering coefficients, the products of the gradients of the Green's function and the photon-density flux, based on the photon-diffusion equation, are required to calculate the diffusion-related Jacobian matrix. The adversities are of two-folds: time-consuming and singular in the field near the source. The latter causes a severe insensitivity of the algorithm to the scattering changes deep inside tissue. To cope with the above difficulties, we propose in this paper a modified GPST algorithm that only involves the Green's function and the photon-density flux themselves in the scattering-related matrix. Our simulated and experimental reconstructions show that the modified algorithm can significantly improve the quality of scattering image and accelerate the reconstruction process, without an evident degradation in absorption image.

Besides single byte errors which are caused by single chip failures, semiconductor memories used in some applications, such as satellite memory systems, are highly vulnerable to random double bit errors. It is therefore necessary to design Double bit Error Correcting--Single b-bit byte Error Correcting (DEC-SbEC) codes which correct both random double bit errors and single b-bit byte errors. This correspondence proposes a class of generic DEC-SbEC codes that are applicable to computer memory systems using recent high density DRAM chips with wide I/O data, such as, 8, 16 or 32 bits per chip. The proposed DEC-S8EC codes are suitable for memory systems using DRAM chips with 8-bit I/O data, and require 24 check bits for practical information lengths such as 64 and 128 bits.

In this paper, a design method of neural-net based PID controllers is proposed for multivariable nonlinear systems with mutual interactions. The proposed method adopt both a static pre-compensator and some multi-layered neural networks. The former is used for roughly decoupling the controlled object, and the latter is used in order to improve decoupling and to linearize the approximately decoupled controlled object. Also the design scheme based on the relationship between PID law and the generalized minimum variance control (GMVC) law is adopted. The effectivenes of the proposed control scheme is evaluated on a simulation example.

In this paper, we propose a new digital signature scheme based on a third order linear feedback shift register for signing documents. This signature scheme is different from most of the signature schemes that are based on discrete logarithm problem, elliptic curves discrete logarithm problem, RSA or quadratic residues. An efficient algorithm for computing kth term of a sequence is also presented. The advantage of this scheme is that the computation is efficient than Schnorr scheme. We also show that the security of the proposed signature scheme is equivalent to that of Schnorr signature scheme.

We describe a scheme of secret communication over the Internet utilizing the potentiality of the TCP/IP protocol suite in a non-standard way. Except for the sender and the receiver of the secret communication it does not need any entities installed with special software. Moreover it does not require them to share any key beforehand. Such features of the scheme stem from the use of IP datagrams with spoofed source addresses and their related error messages for the Internet Control Message Protocol (ICMP) induced by artificial faults. Countermeasures against IP spoofing are deployed in various places since it is often used together with attacks such as distributed denial of service (DDoS) and SPAM mailing. Thus we examine the environment where the scheme works as an intention and also clarify the conditions to obsolete the scheme. Furthermore we estimate the amount of secretly communicated data by the scheme and storage requirements for the receivers and those for the observers who monitor the traffic to detect the very existence of such a secret communication. We also discuss various issues including the sender anonymity achieved by the scheme.

In the previous work, Lampson et al. proposed an IP lookup algorithm which performs binary search on prefixes (BSP). The algorithm is attractive, even for IPv6, because of its bounded worst-case memory requirement. To achieve fast forwarding, it may need to slow down the insertion speed. Although this can be justified, the routing-table reconstruction in BSP is too time-consuming to handle the frequent route updates. In this work, we propose a fast forwarding-table construction algorithm which can accomplish more than 4,000 route updates per second. Moreover, it is simple enough to fulfill the need of fast packet forwarding. With the enhanced multiway search tree, we further reduced the depth of the tree and eliminated the pointer storage; this reduces the forwarding table size and shortens the lookup time.

Recently, as multimedia and high-speed traffic become more popular on the Internet, the various traffic requiring different qualities of service (QoS) will co-exist. In addition, classified service based on Diff-Serv (Differentiated Service), MPLS (Multi-Protocol Label Switching),etc., have come into wide use. Today's Internet environment requires routers to perform control mechanisms in order to guarantee various QoSs. In this paper, we propose a buffer management scheme for the Internet router that uses class-based priority control. This paper focuses on per-flow queueing, and evaluates the performance of the proposed buffer management scheme. Realization of differentiated services and dissolution of buffer occupation by specific flow is expected by the proposed control.

Image processing in transform domain has many advantages but it could be suffered from local effects such as a blocking artifact. In this paper, an image processing is performed by weighting coefficients in the compressed domain, i.e., filtering coefficients are appropriately selected according to the processing. Since we find the appropriate factors according to global image enhancement, blocking artifacts are reduced between inter-blocks. Experimental results show that the proposed technique has the advantages of simple computation and easy implementation.