This paper proposes an agent communication system, in which many communication system's elements, such as communication services, charging and network operation functions, are expressed as agents and multimedia communication services are offered that multi-agents negotiate with each other. The agent communication system is the third communication system. The first communication model is circuit communication model for telephone services, and the second model is the packet communication model for data communication services. The agent communication model is based on the concept of distributed cooperative agent-oriented networking. The agent-oriented software architecture is introduced for supporting multimedia communication services in wide-area networks. Multimedia services are expressed as agents. The paper proposes an agent request broker for multimedia communication services in an agent communication wide-area network. The agent request broker, which is the platform for multi-agents, is based on the concept of agent-oriented software. Furthermore, a five-layer agent communication networking architecture is proposed. Finally, personal communication telephone services, video-mail services and video-on-demand services are presented by using the agent communication system's experimental setup of IP-over-ATM.

High definition television (HDTV) is expected to be one of the major services offered in future broadband integrated services digital networks (B-ISDN). Transmitting HDTV signals over digital networks requires sophisticated compression techniques to limit bit-rate requirements and to provide high-quality, reliable services to customers. To transmit image signals within a studio and between studios or broadcasting stations, multiple encoding and decoding of signals without visible degradation is required. The authors describe a high-quality HDTV codec that can encode original 1.2 Gb/s HDTV signals at 600 Mb/s. A subband DPCM (differential pulse-code modulation) coding algorithm capable of distortion-free encoding is used. Input signals are decomposed into four bands in the horizontal and vertical directions. A new architecture of perfect reconstructive short-kernel subband filters that reduces subband signal entropy has been adopted. Three bands are coded with adaptive DPCM and one band is coded with PCM. The performance of the codec is evaluated using true video signals. Experimental results show that a very high percentage of samples of component signals can be transmitted distortion free. A signal-to-noise ratio (SNR) of over 45 dB is obtained with signals transmitted after the quantization process. Degradation after nine encoding and decoding processes is only 2 dB in terms of SNR.>

A dynamic load balancing method is proposed that uses a multistage switching network to solve the problem of load concentration on certain processors for video coding in multiprocessor digital signal processors. (DSPs) This method balances the processing load by distributing the total load among the processor elements having smaller loads. The load distribution is performed by the multistage switching network, which transmits the load quantity information within the network. A scheduling method for a motion picture coding algorithm using multiprocessor DSPs is also proposed. This scheduling method takes full advantage of the multistage switching network functions when distributing the processing load and sorting the processed results. By using computer simulation, multiprocessor DSP performance with the proposed method is shown to be double that of a conventional multiprocessor DSP when an initially unbalanced load is allocated to the processors, as in picture coding for TV conferences.>

The authors present a subband coding scheme which has the possibility of distortion-free encoding. The coding scheme, which divides input signals into frequency bands, lends itself to parallel implementation. Computer simulation is conducted using high-quality HDTV component signals. Quadrature mirror filters (QMFs) and short-kernel subband filters are compared in terms of entropy (bit-per-pel) and signal-to-noise ratio. Simulation results show that the short-kernel filters can reduce the entropy while maintaining the original picture quality. The number of subband-signal levels was found to be increased. Reduction of the number of signal levels by transformation during the filtering process is studied. From this study, new architectures for short-kernel filters are developed which can reduce the entropy of subband signals better than conventional two-tap filters.>

An adaptive subband coder design for high-quality high-definition television (HDTV) signal transmission through single or multistage coding is presented. In the coder, quadrature mirror filters (QMFs) decompose the input signal into four bands. An adaptive discrete cosine transform is adopted for horizontal-low and vertical-low signal coding. One-dimensional differential pulse-code modulation (DPCM) coding is applied to the signals on the same horizontal line of the horizontal-low and vertical-high band. The other band signals are coded by PCM having a dead zone. Computer simulation results are presented in terms of bit per pel and the quality of the reconstructed picture. The causes of quantization-noise accumulation in tandem connections are also investigated. A coder configuration that reduces noise accumulation is presented.>

A 2*2 optical self-routing switch using integrated laser diode optical switches is proposed. The switch is composed of a Benes network, which can perform large-scale switching functions using less hardware than a crossbar switch. The path each data stream takes through the interconnection network is determined by the binary bits of its destination address, and self-routing is accomplished by monitoring terminal voltage changes in gain guides induced by input optical signals which are injected into a p-n junction. Concentrated control is not necessary, and large optical multistage switches can be easily constructed because complicated electrode patterns are not necessary.>

A fiber-optic high-definition television (HDTV) distribution system is discussed, which economically distributes HDTV signals to customers at a bit rate of about 100 Mb/s. The subscriber network is formed in a star topology to facilitate bidirectional connection. The distribution system uses digital video transmission at 1.3 mu m wavelength using single-mode fiber. The video channel selection is made by an optical video selector. The optical selector consists of laser diode optical switch modules, which have a gain in the 'ON' state and two-input, two-output 3 dB couplers. The authors describe the bit error rate characteristics of a signal-mode fiber digital distribution system using a four-input, one-output optical selector.>

A multiservice fiber-optic subscriber system using wavelength division multiplexing technology has been developed by Nippon Telegraph and Telephone Corporation to provide both 64 kbits/s and broad-band communication services on a single multimode fiber. The subscriber network is formed in a star topology to facilitate bidirectional connection. The system was put in service in March, 1985, as part of the information network system (INS) model system. This paper describes the configuration and characteristics of the video distribution system of this fiber-optic subscriber system. The distribution system uses analog baseband video transmission at a 0.89μm wavelength. The video channel selection is made by an FDM video tuner installed in a central office. The overall performance successfully met design objectives.

Theoretical and experimental results are described for a new optical coupler which consists of two laser diodes, two GRIN spherical rod lenses, a polarizing filter, and a single-mode fiber, and which employs laser diode polarization characteristics for an optical submarine transmission laser redundancy system. This optical coupler has two channels at 1.3 μm wavelength. Optical coupler loss values, which include coupling loss, polarization loss, and assembly loss, are 4.9 dB for one laser diode and 5.2 dB for another laser diode. Such loss values are almost the same as the conventional laser diode module loss for a single-mode fiber. This paper describes in detail a laser redundancy system in an optical submarine transmission system, structure and characteristics of an optical coupler, and experimental results on a high bit rate long-haul transmission system using the proposed optical coupler.