This paper studies effect of packet scheduling algorithms at routers on media synchronization quality in live audio and video transmission by experiment. In the experiment, we deal with four packet scheduling algorithms: First-In First-Out, Priority Queueing, Class-Based Queueing and Weighted Fair Queueing. We assess the synchronization quality of both intra-stream and inter-stream with and without media synchronization control. The paper clarifies the features of each algorithm from a media synchronization point of view. A comparison of the experimental results shows that Weighted Fair Queueing is the most efficient packet scheduling algorithm for continuous media among the four.

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.

Recent activities on ultrafast photonic device technology development in the Femtosecond Technology Project sponsored by NEDO are introduced. Topics include management and control of the higher order dispersions of optical fibers, ultrafast mode-locked semiconductor laser, symmetric Mach-Zehnder type all-optical switch, ultrafast serial-to-parallel signal converter and sub-picosecond wavelength switch. Challenges towards novel ultrafast switching material systems are also described.

We will discuss a novel non-contact removal technique of optical fiber coating in continuous and uninterrupted manner with hot air stream. We observed little degradation of the tensile strength of the optical fiber after removing the protective polymer coating and the mean breaking tensile strength of the stripped optical fiber using non-contact removal method was 5.1 GPa.

We review recent progresses in our studies on the fiber-optic soliton compression and related subjects with special emphasis on dispersion-flattened fibers (DFFs). As for the ultimately short pulse generation, it has been demonstrated to compress 5 ps laser diode pulses down to 20 fs with a 15.1 m-long single-stage step-like dispersion profiled fiber employed. The compression was brought about through a series of the higher order soliton processes in conjunction with a single and ordinary erbium-doped fiber preamplifier, and DFFs contained at its end played a major role. We have performed intensive investigations on the DFF compression mechanisms in the 100-20 fs range. A fairly reliable model was developed for the higher order soliton propagation along a DFF in the temporal range from 100 down to 30 fs by taking into consideration the higher order nonlinear and dispersion effects as well as incident pulse shape dependence. Through the simulation, parametric spectrum generation originating from the modulation instability gain was pointed out at frequencies apart from the pump wave frequency, which agrees with the experimental observation. Its possible application is also discussed.

We propose a frequency stabilization system for laser diodes (LD's), in which the major parameters in the stabilization process can be controlled in respond to the monitored frequency noise characteristics in real-time basis. The performance of this system was also tested through stabilizing a 35 mW visible LD. The center frequency of the LD has been stabilized by negative electrical feedback based on Pound-Drever-Hall technique. The linewidth of the LD has been reduced by adapting optical feedback from resonant confocal Fabry-Perot (CFP) cavity. The controlling parameters, especially gain levels and frequency responses of the negative electrical feedback loop can be manipulated to remove the instantaneous frequency noise by monitoring power spectral density (PSD) of the frequency error signals in the real-time basis. The achieved PSD of frequency noise of a sample LD stabilized by the present system was less than 1105 Hz2/Hz for the Fourier frequency < 10 MHz. The reduced linewidth was estimated to be narrower than 400 kHz. The achieved minimum square root of the Allan variance was 3.910-11 at τ = 0.1 msec.

The methods for the transverse mode control and temperature characteristics improvement in 850 nm oxide confined vertical cavity surface emitting lasers (VCSELs) were investigated. For transverse mode control, dielectric aperture was demonstrated to suppress higher order modes. Substitution of AlAs for Al0.9Ga0.1As in partial bottom DBR was demonstrated to reduce thermal resistance of the devices and to enable operation in high temperature of 85.

We have developed optical encoding devices for processing femtosecond pulses. These devices are based on spectral separation devices and light modulators with fiber gratings. Experiments were made to encode a light pulse in the spectral domain. These experiments utilize the characteristics that a femtosecond light pulse has a very broad spectrum. An input femtosecond light pulse is decomposed into a series of wavelength components. Each wavelength component with narrow spectra <1 nm width is successfully extracted into a single mode fiber. Light modulators corresponding to wavelength components are assigned to the 1st bit, the 2nd bit, the 3rd bit, , the nth bit, respectively. All of the encoded wavelength components are again recombined into a single time-varying signal and transmitted through an optical fiber. Decoding at receiving site is made by the reverse operation. Encoding and decoding for 2-bit and 4-bit signals were demonstrated for 200 fs input light pulse with about 40 nm spectral width.

The thermal response of a tunable laser is analyzed by using a mode density method based on a Fourier-Laplace analysis. This method introduces a mode density function for mode distribution of the Fourier-Laplace transform and gives temperature time-dependency in an integral form instead of an infinite weighted summation. When symmetric structures are assumed, the mode density method gives the transient thermal response in a simple form: error functions (spherical-symmetry case) and exponential integral functions (cylindrical-symmetry case). The cylindrical-symmetry analysis was extended to the noncylindrical-symmetry model and the thermal response of the tunable laser was calculated by the mode density method. The result shows good agreement with a Fourier-Laplace analysis (deviation 2%) and experimental results. As a rough estimation, the thermal response of the laser is in proportion to the logarithm of time in some range that depends on the chip and tuning-section size of the laser.

A new objective speech quality measure, Bark Coherence Function is presented. The Coherence Function was used for evaluating the non-linear distortion of low-to-medium rate speech coders. However, it is not well suited for quality estimation in modern speech transmission, especially, CDMA mobile communication system. In the proposed method, Coherence Function is newly defined in psycho-acoustic domain as the cognition module of perceptual speech quality measure and evaluates the perceptual non-linear distortion of mobile system. The experimental results showed that the proposed method has good performance over CDMA PCS and digital cellular system.

In this paper, a hardware-oriented Genetic Algorithm (GA) was proposed in order to save the hardware resources and to reduce the execution time of GAP. Based on steady-state model among continuous generation model, the proposed GA used modified tournament selection, as well as special survival condition, with replaced whenever the offspring's fitness is better than worse-fit parent's. The proposed algorithm shows more than 30% in convergence speed over the conventional algorithm. Finally, by employing the efficient pipeline parallelization and handshaking protocol in proposed GAP, above 30% of the computation speed-up can be achieved over survival-based GA which runs one million crossovers per second (1 MHz), when device speed and size of application are taken into account on prototype. It would be used for high speed processing such of central processor of evolvable hardware, robot control and many optimization problems.

We propose new lossless medical image compression method based on hierarchical sorting technique. Hierarchical sorting is a technique to achieve high compression ratio by detecting the regions where image pattern varies abruptly and sorting pixel order by its value to increase predictability. In this method, we can control sorting accuracy along with size and complexity. As the result, we can reduce the sizes of the permutation-tables and reuse the tables to other image regions. Comparison using experimental implementation of this method shows better performance for medical image set measured by X-ray CT and MRI instruments where similar sub-block patterns appear frequently. This technique applies quad-tree division method to divide an image to blocks in order to support progressive decoding and fast preview of large images.

It is shown that the effective secret-key size of TOYOCRYPT-HS1 stream cipher is only 96 bits, although the secret key consists of 128 bits. This characteristic opens a door for developing an algorithm for cryptanalysis based on the time-memory-data trade-off with the overall complexity significantly smaller than the exhaustive search over the effective key space.

The explosive growth of World Wide Web usage is causing a number of performance problems, including slow response times, network congestion, and denial of service. Web site that has a huge number of accesses and requires high quality of services, such as a site offering hosting services, or content delivery services, usually uses a cache server to reduce the load on the original server offering the original content. To increase the throughput of the caching process and to improve service availability, multiple cache servers are often positioned in front of the original server. This requires a switch to direct incoming requests to one of the multiple cache servers. In this paper, we propose a routing algorithm for such a switch in front of clustered multiple cache servers and evaluate its performance by simulation. The results show that our routing algorithm is effective when content has request locality and a short period of validity, for example, news, map data, road traffic data, or weather information. We also identify points to consider when the proposed algorithm is applied to a real system.

We propose a call admission control (CAC) scheme for the reverse link of direct sequence-code division multiple access (DS-CDMA) systems with multi-class traffic, in which the admissibility of the set of requested channels is decided by checking the outage probability of the total composite power at a cell-site receiver. The reverse link capacities under various traffic conditions are evaluated. From numerical results, we see that the proposed scheme can utilize a given radio resource more effectively as compared with the existing scheme using constraints on the individual power levels.

We have developed a 200-channel imaging system that enables measurement of changes in oxygenation and blood volume and that covers a wider area (45 cm 15 cm) than that covered by conventional systems. This system consisted of 40 probes of five channels, a light-emitting diode (LED) driver, multiplexers and a personal computer. Each probe was cross-shaped and consisted of an LED, five photo diodes, and a current-to-voltage (I-V) converter. Lighting of the LEDs and acquisition of 200-channel data were time-multiplexed. The minimum data acquisition time for 200 channels, including the time required for calculation of oxygenation and monitoring of a few traces of oxygenation on a computer display, was about 0.2 s. We carried out exercise tests and measured the changes in oxy- and deoxy-hemoglobin concentrations in the thigh. Working muscles in exercises could be clearly imaged, and spatio-temporal changes in muscle oxygenation during exercise and recovery were also shown. These results demonstrated that the 200-channel imaging system enables observation of the distribution of muscle metabolism and localization of muscle function.

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.

The backward direction Soft Output Viterbi Algorithm (a backward SOVA) is compared with the conventional SOVA (a forward SOVA) in turbo code decoding. We find noticeable performance improvement for the backward SOVA when it is not terminated, which turns out to be due to a smaller reliability value, indicating that the termination conditions of the turbo encoder strongly affect the performance of the backward SOVA decoder. We also propose a hardware efficient serially mixed SOVA decoder composed of a forward SOVA decoder and a backward SOVA decoder. Simulation results show that the proposed serially mixed SOVA decoder has a 0.2 dB coding gain at 2.0 dB Eb/No over the forward SOVA for a typical turbo code example.

The vertical-cavity surface-emitting laser (VCSEL) is becoming a key device in high-speed optical local-area networks (LANs) and even wide-area networks (WANs). This device is also enabling ultra parallel data transfer in equipment and computer systems. In this paper, we will review its physics and the progress of technology covering the spectral band from infrared to ultraviolet by featuring materials, fabrication technology, and performances such as threshold, output power, polarization, modulation and reliability. Lastly, we will touch on its future prospects.

In this paper, a new image synthesis model based on a set of wavelet bases is proposed. In the proposed model, images are approximated by the sum of synthesis functions that are translated to image edge positions. By applying the proposed model to sketch-based image coding, no iterative image recovery procedure is required for image decoding. In the design of the synthesis functions, we define the synthesis functions as a linear combination of wavelet bases. The coefficients for wavelet bases are obtained from an iterative procedure. The vector quantization is applied to the vectors of the coefficients to limit the number of the synthesis functions. We apply the proposed synthesis model to the sketch-based image coding. Image coding experiments by eight synthesis functions and a comparison with the orthogonal transform methods are also given.