When wireless multi-media information such as voice, video, data and so on are transmitted, the difference required quality of Service (QoS) including required Bit Error Rate (BER), required information bit rate, message's delay constraints as well as traffic performance should be taken into account. A wireless multi-media system should achieve a flexible balance of these differences. In this letter, an Adaptive Chip/Bit Control Method is proposed for Wireless Multi-media CDMA System. The proposed method controls both chip and bit rate of each medium according to the offered traffic condition and the quality measurement of each medium. In the proposed method, measurement are carried out in the base station. Simulation results show that the proposed method not only maintain the required BER of each medium, but achieve a higher total throughput even in high traffic condition. Thus we see that the proposed method possesses higher flexible ability than conventional methods.

In this paper, the bit error rate (BER) performance of the Spread Spectrum communication with Constrained Spreading Code system is studied under the synchronous CDMA system. Particularly, BER considering the tracking error is derived by theoretical analysis. The synchronizing spreading sequence is employed to track the signals in the receiver. As the result, the BER performance is degraded by increasing the number of users. However, the BER performance can be improved by canceling the co-channel interference and by suppressing the cross-correlation value between the information spreading sequence and the synchronizing spreading sequence.

This paper proposes a novel asynchronous direct sequence/code division multiple access (DS/CDMA) communication system using analog pseudo noise (PN) sequences that have an orthogonal relation for all active users. Analog PN sequences are produced by an adaptive filter called a "code-orthogonalizing filter" (COF). In a base station receiver, the tap coefficients of the COF can be adaptively controlled "to orthogonalize" or "to approach to orthogonalize" various received PN sequences. The elements of the analog PN sequences consist of the tap coefficients of the COF. The analog PN sequence produced is assigned to the transmitter of each user in order. As a result, multiple access interference (MAI) caused by other users can be reduced considerably, and multiple access capacity increased by the proposed system compared with matched filter (MF) reception and COF reception.

In pursuing its vision that digital signals will come to dominate not only voice communications but also various services on an integrated basis in future telecommunications, NTT has successfully completed a major part of telephone network preparations by digitizing all of its networks by the end of 1997. Accompanying digitization, it has also started providing various new services including the initiation of best-effort services through OCN. At the same time, the steady progress in Internet diffusion, the globalization of enterprise networks and inter-company electronic transactions are leading to the full scale usage of IP network communications. Because IP networks are still faced with pressing demand and unresolved issues, NTT believes it is also necessary to structure and provide computer-compatible networks suitable for IP communications by shifting from telephone-focused architecture in order to respond better to these growing needs. This paper overviews the digital network assets including ISDN that NTT has accumulated as a carrier as well as the IP networks such as the Internet that have spread throughout our societies. It also outlines new access services and network offerings based on optical and other technologies and the ATM networks that serve as the infrastructure for highly reliable and economical IP networks, and presents our thinking behind how such networks will be organically combined.

Parallel multiple context-free grammar (PMCFG) and multiple context-free grammar (MCFG) were introduced to denote the syntax of natural languages. By the known fastest algorithm, the recognition problem for multiple context-free language (MCFL) and parallel multiple context-free language (PMCFL) can be solved in O(ne) time and O(ne+1) time, respectively, where e is a constant which depends only on a given MCFG or PMCFG. In this paper, we propose the following two algorithms. (1) An algorithm which reduces the recognition problem for MCFL to the boolean matrices multiplication problem. (2) An algorithm which reduces the recognition problem for PMCFL to the recognition problem for MCFL. The time complexity of these algorithms is O(ne-3i+1 M(ni)) where e and i are constants which depend only on a given MCFG or PMCFG, and M(k) is the time needed for multiplying two k k boolean matrices. The proposed algorithms are faster than the known fastest algorithms unless e=e, i=1 for MCFG, and e=e, i=0 for PMCFG.

In ATM Network, the VBR (Variable Bit Rate) service category is used to accommodate TCP/IP traffic. In an international ATM network with large propagation delay, higher TCP throughput can be obtained by use of window scale option. In order to accommodate TCP traffic with window scale option effectively, it is required to select appropriate values of VBR parameters, i. e. SCR (Sustainable Cell Rate) and MBS (Maximum Burst Size), and to evaluate the impact of UPC (Usage Parameter Control) function on TCP throughput. We have studied those technical issues for the conventional TCP, but the results cannot be applied to TCP traffic with the window scale option due to the TCP terminal performance and the large window size. In this paper, we proposed VBR parameter determination method for TCP with the window scale option and evaluated the values in each condition. These results show that the determined MBS is much smaller than the burst length of TCP segments especially using low performance TCP terminals. Furthermore, we also discuss some experimental results of TCP throughput degradation due to UPC function. It shows that the throughput of TCP with large window size is degraded when the SCR and MBS values used in ATM switch are smaller than the determined values.

This paper proposes local lightwave networks with grouping property which are based on a wavelength division multiplexing (WDM). The proposed network is partitioned into several groups according to traffic volume between stations so that traffic is more likely to be within groups. The stations within a group are connected to a broadcast-and-select WDM network with star topology. For inter-group communication, a WDM network of each group is connected to another star-topology WDM network through a special station called a router. In the proposed network, intra-group communication is achieved by one hop and inter-group communication goes through multiple hops. We analyze the average hop number, the maximum throughput, and the mean packet delay of the proposed network and investigate its performance characteristics. Since the proposed network has the better performance as its grouping property strengthens, it is fit for local lightwave networks with the locality of traffic.

This paper investigates an ATM multiplexer with a resume level, which uses a selective cell discarding strategy as a priority control, and a Markov-modulated deterministic process (MMDP) as the burst input traffic. Assuming that a system is loaded with a superposition of several independent and homogeneous On-Off bursty sources with two priority classes, we obtain the cell loss probability of each priority class of an ATM multiplexer with a resume level. The performance analysis derived here includes as special cases one without priority and one with a threshold level. From the numerical results, we compare the cell loss probability, the mean queue length, the mean queuing delay, the level crossing rate, and the queue length distribution at the embedded points for the case of a threshold level with those for the case of a resume level. By selecting an appropriate resume level, we can reduce the sensitive state change around the threshold level.

Telecommunication technologies are making relentless progress. In this circumstance, network cost must be evaluated to assess the effectiveness of emerging technologies. To do such an evaluation efficiently, it is necessary to develop a software tool that can calculate the network cost independent of the employed technologies. This paper describes computational techniques used in developing such a software tool. First, the functional requirements are identified to establish a flexible tool that is applicable to a wide range of technologies. One of the required functions is the function that computes the resource amount and the network cost from the given conditions such as traffic demands, a cable duct network, multiplex hierarchy and the specifications of network elements employed. As this computing function, the paper proposes an appropriate path classification scheme that enables us to evaluate the resource amount correctly when a service protection technique is applied to the target network. Namely, the proposed scheme yields evaluations that isolate the primary path route from the backup path route. This isolation is not always provided without classification. In addition, a classification of network elements is also derived for valid estimation of the necessary interface board number, which is a basis of estimating the required network element amount. This classification allows us to identify the exact points of path cross-connection and termination, which affects the number of interface boards. This paper presents the computing procedures that realize path grouping and an estimation of network elements using these classification schemes. Finally, the paper describes a prototype of the tool to confirm the feasibility and effectiveness of the proposed schemes.

In this paper, a novel pass-transistor logic with an efficient level restoration circuit, named Power Saved Pass-transistor Logic (PSPL), is proposed. It is shown how, through the use of regenerative feedback with pMOS switches, we reduce the power consumption and propagation delay compared to conventional pass-transistor logic. To demonstrate the performance of PSPL, a 5454-bit multiplier is designed. For speed and power optimization, the multiplier uses high compression-rate compressors without Booth Encoding, and a 108-bit conditional sum adder with separated carry generation block. The measured multiplication time was 13. 5 ns in a 0. 6 µm single-poly triple-metal 3. 3 V CMOS process. Furthermore, a sequential circuit of a low power 7-bit serial counter is designed and fabricated in a 0. 6 µm single-poly triple-metal 3. 3 V CMOS process. The measured operating speed was 250 MHz.

We propose and demonstrate a simple polarization-independent construction of a local node for optical WDM ring networks using a centralized multiwavelength light source (MWLS). The node is simply composed of a 4-port optical circulator, an add/drop multiplexing (ADM) filter, a reflective modulator, and a drop fiber Bragg grating (FBG). A Faraday rotator mirror (FRM) is used to enable an LiNbO3 intensity modulator to operate in the polarization-independent mode. We examine three ADM filters, an interference filter, a fiber Fabry-Perot (FP) filter, and a set of FBG's. An optical WDM system experiment is performed to demonstrate the feasibility of the proposed node construction.

QoS of a multimedia interactive satellite communications system, which uses a satellite circuit for downlinks and a terrestrial network for uplinks, has been measured and evaluated under inferior satellite circuit conditions. Our attention in this paper is focused on TCP throughput as the most significant QoS, and experiments and analysis on TCP throughput were performed. The measured results are in good agreement with theoretical values calculated by taking congestion avoidance algorithms of TCP into consideration. As a result, we were able to verify that the TCP throughput declines radically when the low signal quality of a satellite circuit causes packet retransmission to occur. In this case, congestion avoidance works to reduce network congestion. The congestion avoidance increases the value of a retransmission timer and decreases the window size even if the network is not congested. Assuming that throughput deterioration is caused by rain fade, the total time when the throughput declines is less than 4 hours a year in Tokyo, and the results show the system can be put to practical use.

Resonant properties of resistively shunted tunnel junctions dominate the high-frequency performance of Josephson array oscillators. To improve the operating frequency, we have developed resistively shunted Nb/AlOx/Nb tunnel junctions with a small parasitic inductance. The inductance was minimized by reducing the inductive length between the tunnel junction and the contact hole to be about 1µm. By fitting the measured I-V characteristics of the shunted tunnel junction to the simulated characteristics, we estimated the inductance to be about 105 fH. The analysis of resonant properties showed that the shunted tunnel junctions with the small parasitic inductance have a high-frequency performance up to the Nb gap frequency. Josephson array oscillators using 11 such junctions were designed and fabricated to operate at 650 GHz and 1 THz. Shapiro steps induced by Josephson oscillation were clearly observed up to 1 THz. By fitting the step heights to the simulated results, we estimated the output power of the Josephson oscillator delivered to the load resistor to be about 10 µW at 625 GHz and 50 nW at 1 THz.

This paper describes IDDQ testability for bridging faults in a variety of flip-flops. The flip-flop is a basic element of the sequential circuit and there are various structures even for the same type. In this paper, we use five kinds of master-slave D-type flip-flops as the circuit under test. Target faults are two-line resistive bridging faults extracted from a circuit layout. A flip-flop with a deliberately introduced bridging fault is simulated by the SPICE simulator. Simulation results show that IDDQ testing cannot detect faults existing at specific points in some flip-flops, and this problem depends on the flip-flop structure. However, IDDQ testing has high fault coverage ( 98%) compared with traditional logic testing. We also examine performances of fully IDDQ testable flip-flops.

This paper proposes and performs the primary feasibility evaluation on Flow Attribute Notification Protocol (FANP), which is a protocol between neighbor CSR (Cell Switch Router) nodes for the management of cut-through packet forwarding, in order to apply label switching paradigm. In cut-through packet forwarding with label switching, a router doesn't have to perform conventional IP packet processing for the received packets. FANP indicates the mapping information between a data-link connection and a packet flow to the neighbor node. FANP defines two key procedures, i. e. , one is the VCID Notification Procedure, and the other is the Flow-ID Notification Procedure. The VCID Notification Procedure lets the label switching paradigm over the label swapped data-link, such as ATM link, though the other label switch architecture can not work over the label swapped data-link. The primary evaluation of FANP has been performed using the prototype system and with the actual packet statistics. The result shows that, with a corporate backbone level, the label switch router system with FANP would work well.

We report the state of the art of superconducting network switching circuits and system technology. Mainly, we describe our switching core circuits and challenges to demonstrate superconducting prototype systems. And also, we review other approach to perform the superconducting digital communication briefly. In our switching core circuits, a ring-pipeline architecture has been proposed and the component circuits of the prototype chips have been fabricated and tested successfully. It is very important to demonstrate the prototype system in order to estimate the total performance of the system with superconducting devices. We have designed a multi-processor system with a superconducting network as a prototype system to demonstrate an interprocessor network system.

The stability of slotted ALOHA systems with various types of capture phenomena and multiple packet reception capability is discussed in conjunction with the cusp catastrophe. The slotted ALOHA systems considered are classified into; 1) single packet reception with geometric capture, 2) independent multiple packet reception with geometric capture, 3) single packet reception with M-out-of-N capture (M N), 4) multiple packet reception with M-out-of-N capture, and 5) single packet reception with perfect capture. First, general expressions for the cusp points and the bifurcation sets are derived. Then, we present explicit formula for the stability of slotted ALOHA systems for the five types of capture and multi-packet reception capability and demonstrate how the bistable behavior is mitigated due to capture effect and multi-packet reception capability.

In the commonsense reasoning, priorities among rules are often required to be found out in order to derive the desired conclusion as a theorem of the reasoning. In this paper, first we present the bottom-up and top-down abduction procedures to compute skeptical explanations and secondly show that priorities of circumscription to infer a desired theorem can be abduced as a skeptical explanation in abduction. In our approach, the required priorities can be computed based on the procedure to compute skeptical explanations provided in this paper as well as Wakaki and Satoh's method of compiling circumscription into extended logic programs. The method, for example, enables us to automatically find the adequate priority w. r. t. the Yale Shooting Problem to express a human natural reasoning in the framework of circumscription.

We propose a method of reducing laser-clipping-induced distortion in a subcarrier multiplexed (SCM) optical-cable TV system. This scheme reduces amplitude peaks of the SCM signal by controlling the phases of video carriers to prevent the clipping which occurs when these peaks fall below the threshold of a laser-diode. It is experimentally shown that using this method reduces the bit error rate in an AM-VSB / QAM hybrid optical-transmission system.

For the realization of the very high-speed data transmission over wide area network, the HIPPI-ATM conversion for connecting two remote HIPPI end systems is specified by ANSI. Since the credit scheme is adopted for the flow control on the ATM part in the specification, the propagation delay influences the remarkable transfer throughput degradation with the longer distance between end systems. In this paper, two priority types of HIPPI bursts are proposed, which include the flag indicating the priority, high priority or low priority. We propose the hybrid scheme that the credit scheme is adopted only for sending the high priority HIPPI bursts and the source can send low priority HIPPI bursts without reserving buffers in the receiver. In order to confirm the effectiveness of the proposed scheme, we show the characteristics of transfer performance and low priority bursts loss ratio v. s. transmission distance by simulation. Furthermore, we introduce the implemental example of the proposed scheme in the MPEG video transmission application, and show it's good performance.