Thanks to rapid progress in computer technology and VLSI technology, we are approaching the stage where ordinary PCs will be able to handle real-time video signals as easily as they handle text data. First, features and applications of the video compression standard MPEG2 are surveyed as a typical video processing. It is clarified that real-time capability becomes more important as applications of MPEG2 widely spread. The trends of video coding in LSIs are summarized. And it is shown that the most advanced encoder/decoder LSI has an improved price-performance ratio that allows it to be adopted in consumer equipment. Finally, future directions of parallel architecture in video processing are surveyed in terms of special-purpose and general-purpose processing. The special approach has always taken the lead in video processing using sophisticated hardware-oriented parallel architectures. The general-purpose architecture method has gradually evolved in accordance with a software-oriented architecture. Both approaches will continue to evolve into a new stage by selecting possible parallel architectures such as multimedia instruction sets and process-level parallelism, and applying them in compound use. The so-called super processor architecture will emerge in the near future and it will be an ideal method that can manage rapid increase in requirements of capability and applicability in video processing.

The tera-bit order capacity of ultrahigh-speed and wide-band networks will become necessary to provide highly advanced multimedia services. In conventional networks, electronic circuits limit the speed capability of the networks. Consequently, all-optical networks are essential to realize ultrahigh-speed and wide-band communications. In this paper, we propose the configuration of an all-optical code division multiplexing (CDM) switching network based on self-routing principles and the structure of a nonlinear all-optical switching device as one of the key components for the network. We show that the required performances of the optical devices used in the CDM switching fabric are lower than those used in the TDM and illustrate the basic transmission characteristics of the switching device utilizing FD-BPM. To evaluate the multiplexing performance, we demonstrate the maximum number of channels under an error-free condition and the BER characteristics when the Gold sequence is applied as one of the CDM code sets, and show that the network of the sub-tera-bit order capacity is realizable by adopting TDM, WDM and CDM technologies. We also illustrate the packet assembly method suitable for self-routing transmissions and one of network architectures where the proposed switching fabric can be exploited.

Wavelength division multiplex (WDM) photonic networks are expected as the key for the global communication infrastructure. Recent increase of communication demands require large-scale highly-dense WDM systems, which results in severe requirements for optical cross-connect systems, such as cross-talk specification. In this paper, we propose a new optical path cross-connect system (OPXC) using matrix-WDM scheme, which makes it possible to reduce cross-talk requirements of WDM filters and to construct OPXC in modular structures. The matrix-WDM scheme is a concept of two-layered optical paths, which provides wavelength group managements in the fiber dispersion equalization and EDFA gain equalization.

We propose a real-time low-rate video compression algorithm using fixed-rate multi-stage hierarchical vector quantization. Vector quantization is suitable for mobile computing, since it demands small computation on decoding. The proposed algorithm enables transmission of 10 QCIF frames per second over a low-rate 29.2 kbps mobile channel. A frame is hierarchically divided by sub-blocks. A frame of images is compressed in a fixed rate at any video activity. For active frames, large sub-blocks for low resolution are mainly transmitted. For inactive frames, smaller sub-blocks for high resolution can be transmitted successively after a motion-compensated frame. We develop a compression system which consists of a host computer and a memory-based processor for the nearest neighbor search on VQ. Our algorithm guarantees real-time decoding on a poor CPU.

By adopting a network architecture in which not only a calling but also a called terminal can select a wavelength, a novel WDM network becomes possible. This we call Wavelength Assignment Photonic Network (WAPN). In this network wavelengths are a kind of network resources and according to requests from terminals, wavelengths are allocated or assigned to calls. In the system a wavelength used for a call is to be used for another call after the call is terminated. By supplying wavelengths to the home, a bitrate-free, protocol free or even transmission method free network can be realized. In this paper, from a viewpoint of S/N or Q factor, WAPN is evaluated with special focus on the node architecture--i. e. , from the viewpoint of node size, number of switching stages, crosstalk level,and losses, because the allowable node size is the crucial issue to decide the whole network capacity. After brief explanations of this proposed system, the model for system evaluations will be established and a node system is to be evaluated for some practical parameter values considering especially traffic characteristics of a node. As a result of this study a node system with capacity more than 100 thousands erl (about 20 Tbps throughput) can be constructed using present available technologies, which will enable us to construct large WAPN network with radius of 2,000 km and subscribers of about 50 millions.

The hybrid electrical/optical multi-chip integration technique for optical modules for optical network system has been developed. Employing the technique, a 44 broadcast-and-select type optical matrix switch module has been realized. The module consists of four sets of silica waveguide 1 : 4 splitters/4 : 1 combiners, four 4-channel arrays of polarization insensitive semiconductor optical amplifiers with spot-size converters as optical gates, printed wiring chips for electrical wiring and single mode fibers for optical signal interface on planar waveguide platform fabricated by atmospheric pressure chemical vapor deposition. All the gates and the wiring chips were mounted precisely onto the platform at once in flip-chip manner by self-align technique using AuSn solder bumps. Coupling loss between the waveguide and the SOA gate was estimated to be 4.5 dB. Averaged fiber-to-fiber signal gain, on-off ratio and polarization dependent loss for each of the signal paths was 7 dB 2 dB, more than 40 dB and 0.5 dB, respectively. High speed 10 Gb/s photonic cell switching as short as 2 nsec has been successfully achieved.

A 116 arrayed waveguide grating multiplexer operating around 1550 nm has been realized using newly synthesized fluorinated poly(arylene ethers). The channel spacing is 0.8 nm (100 GHz). The insertion loss of the multiplexer is 17-20 dB and the cross talk is less than -15 dB. The propagation loss of a rib waveguide is less than 0.5 dB/cm at 1550 nm.

Noise greatly degrades the image quality and performance of image compression algorithms. This paper presents an approach for the representation and compression of noisy synthetic images. A new concept region-based prediction (RBP) model is first introduced, and then the RBP model is utilized on noisy images. In the conventional predictive coding techniques, the context for prediction is always composed of individual pixels surrounding the pixel to be processed. The RBP model uses regions instead of individual pixels as the context for prediction. An algorithm for the implementation of RBP is proposed and applied to noisy synthetic images in our experiments. Using RBP to find the residual data and encoding them, we achieve a bit rate of 1.10 bits/pixel for the noisy synthetic image. The decompressed image achieves a peak SNR of 42.59 dB. Compared with a peak SNR of 41.01 dB for the noisy synthetic image, the quality of the decompressed synthetic image is improved by 1.58 dB in the MSE sense. In contrast to our proposed compression algorithm with its improvement in image quality, conventional coding methods can compress image data only at the expense of lower image quality. At the same bit rate, the image compression standard JPEG provides a peak SNR of 33.17 dB for the noisy synthetic image, and the conventional median filter with a 33 window provides a peak SNR of 25.89 dB.

To enhance the extinction ratio (ER) of NRZ-to-inverted-RZ converter based on cross-gain compression of a semiconductor optical amplifier (SOA), a modified terahertz optical asymmetric demultiplexer (TOAD) is cascaded. ER is improved from 1.6-6.7 dB to 5.4-14.5 dB, depending on the intensity of input optical NRZ signal. The proposed NRZ-to-inverted-RZ converter enhances and regulates ER to a high value (14.5 dB) for very wide optical NRZ signal intensity range.

Spot-size-converter integrated semiconductor optical amplifiers have been developed as gate elements for optical switch matrices. An S-shape waveguide has been introduced to prevent re-coupling of unguided light to the output fiber. An angled-facet structure effectively suppressed light reflection at the end facets. Consequently, a high extinction ratio of 70 dB and a high fiber-to-fiber gain of 20 dB were achieved. Sufficient optical coupling characteristics to a flat-ended single-mode fiber with a coupling loss of 3.5 dB were also demonstrated.

This paper proposes a fast synchronization scheme with a short preamble signal for high data rate wireless LAN systems using orthogonal frequency division multiplexing (OFDM). The proposed OFDM burst format for fast synchronization and the demodulator for the proposed OFDM burst format are described. The demodulator, which offers automatic frequency control and symbol timing detection, enables us to shorten the preamble length to one quarter that of a conventional one. Computer simulation results show that the degradation in required Eb/N0 due to the synchronization scheme is less than 1 dB in a selective Rayleigh fading channel.

The tera-bit order capacity of ultrahigh-speed and wide-band networks will become necessary to provide highly advanced multimedia services. In conventional networks, electronic circuits limit the speed capability of the networks. Consequently, all-optical networks are essential to realize ultrahigh-speed and wide-band communications. In this paper, we propose the configuration of an all-optical code division multiplexing (CDM) switching network based on self-routing principles and the structure of a nonlinear all-optical switching device as one of the key components for the network. We show that the required performances of the optical devices used in the CDM switching fabric are lower than those used in the TDM and illustrate the basic transmission characteristics of the switching device utilizing FD-BPM. To evaluate the multiplexing performance, we demonstrate the maximum number of channels under an error-free condition and the BER characteristics when the Gold sequence is applied as one of the CDM code sets, and show that the network of the sub-tera-bit order capacity is realizable by adopting TDM, WDM and CDM technologies. We also illustrate the packet assembly method suitable for self-routing transmissions and one of network architectures where the proposed switching fabric can be exploited.

The application of photonic technologies to packet switching offers the potential of very large switch capacity in the terabit per second range. The merging of packet switching with photonic technologies opens up the possibility of packet switching in transparent photonic media, in which packets remain in optical form without undergoing optoelectronic conversion. This paper reviews recent work on photonic packet switching. Different approaches to photonic packet switching and key design issues are discussed.

A problem of obtaining an optimal file transfer on a file transmission net N is to consider how to distribute, with a minimum total cost, copies of a certain file of information from some vertices to others on N by the respective vertices' copy demand numbers. This paper proves such a problem to be NP-hard in general.

A new low voltage high-speed CMOS composite transistor is presented. It lowers supply voltage down to |Vt|+2 Vds,sat and considerably extends input voltage operating range and achieves high speed operation. As an application example, it is used in the design of a high-speed four quadrant analog multiplier. Simulations results using MOSIS 2µm N-well process with a 3 V supply are given.

In this paper, the computational issue in the problem of learning Bayesian belief networks (BBNs) based on the minimum description length (MDL) principle is addressed. Based on an asymptotic formula of description length, we apply the branch and bound technique to finding true network structures. The resulting algorithm searches considerably saves the computation yet successfully searches the network structure with the minimum value of the formula. Thus far, there has been no search algorithm that finds the optimal solution for examples of practical size and a set of network structures in the sense of the maximum posterior probability, and heuristic searches such as K2 and K3 trap in local optima due to the greedy nature even when the sample size is large. The proposed algorithm, since it minimizes the description length, eventually selects the true network structure as the sample size goes to infinity.

A pipelined architecture is proposed for the normalized least mean square (NLMS) adaptive digital filter (ADF). Pipelined implementation of the NLMS has not yet been proposed. The proposed architecture is the first attempt to implement the NLMS ADF in the pipelined fashion. The architecture is based on an equivalent expression of the NLMS derived in this study. It is shown that the proposed architecture achieves a constant and a short critical path without producing output latency. In addition, it retains the advantage of the NLMS, i. e. , that the step size that assures the convergence is determined automatically. Computer simulation results that confirm that the proposed architecture achieves convergence characteristics identical to those of the NLMS.

The hybrid electrical/optical multi-chip integration technique for optical modules for optical network system has been developed. Employing the technique, a 44 broadcast-and-select type optical matrix switch module has been realized. The module consists of four sets of silica waveguide 1 : 4 splitters/4 : 1 combiners, four 4-channel arrays of polarization insensitive semiconductor optical amplifiers with spot-size converters as optical gates, printed wiring chips for electrical wiring and single mode fibers for optical signal interface on planar waveguide platform fabricated by atmospheric pressure chemical vapor deposition. All the gates and the wiring chips were mounted precisely onto the platform at once in flip-chip manner by self-align technique using AuSn solder bumps. Coupling loss between the waveguide and the SOA gate was estimated to be 4.5 dB. Averaged fiber-to-fiber signal gain, on-off ratio and polarization dependent loss for each of the signal paths was 7 dB 2 dB, more than 40 dB and 0.5 dB, respectively. High speed 10 Gb/s photonic cell switching as short as 2 nsec has been successfully achieved.

We apply two acceleration techniques for the backpropagation algorithm to an iterative gradient descent algorithm called the network inversion algorithm. Experimental results show that these techniques are also quite effective to decrease the number of iterations required for the detection of input vectors on the classification boundary of a multilayer perceptron.

A 116 arrayed waveguide grating multiplexer operating around 1550 nm has been realized using newly synthesized fluorinated poly(arylene ethers). The channel spacing is 0.8 nm (100 GHz). The insertion loss of the multiplexer is 17-20 dB and the cross talk is less than -15 dB. The propagation loss of a rib waveguide is less than 0.5 dB/cm at 1550 nm.