This paper investigates the error rate performance of parallel combinatorial spread spectrum (PC/SS) communicaion systems that use coherent and differential multiphase modulation: multiphase parallel combinatorial spread spectrum (MPC/SS) communication systems. The PC/SS systems are multicode SS systems based on orthogonal pseudo-noise (PN) sequences. Data is transmitted by delivering a combination of multiple PN sequences among a set of pre-assigned PN sequences. In the MPC/SS systems, every PN sequence on transmission is modulated by q-ary coherent or differential phase shift keying (PSK). Symbol error rate (SER) and average bit error rate (BER) in coherent and differential MPC/SS systems are investigated. The BER comparison between the MPC/SS systems and simple multicode SS systems with q-ary coherent and differential PSK is also presented. Numerical results show that the MPC/SS systems are superior to the conventional q-ary PSK systems, if they have equal spectral efficiency.

New functional surface tunnel transistors (STTs) with multiple interband-tunnel-junctions in a symmetric source-to-drain structure are proposed to reduce the number of fabrication steps and to increase functionality. These devices have p+/n+ interband tunnel junctions in series between a p+ source and a p+ drain through n+ channels. We successfully fabricated GaAs-based multiple-junction STTs (MJ-STTs) using molecular-beam epitaxy regrowth. This fabrication method eliminates the need for two of the photo-masks in the conventional process for asymmetric planar STTs. In the preliminary experiments using multiple-junction p+/n+ diodes, we found that the peak-voltage increment in negative-differential-resistance (NDR) characteristics due to the reverse-biased tunnel junction in negligible, while the first-peak voltage is roughly proportional to the number of forward-biased tunnel junctions. Moreover, the number of NDR characteristics are completely determined by the number of tunnel junctions. The fabricated STTs with multiple junctions, up to eight junctions, exhibited clear transistor operation with multiple NDR characteristics, which were symmetric with the drain bias. These results indicate that any number of gate-controlled NDR characteristics can be realized in MJ-STTs by using an appropriate number of tunnel junctions in series. In addition, as an example of a functional circuit using MJ-STTs, we implemented a tri-stable circuit with a four-junction STT and a load resistor connected in series. The tri-stable operation was confirmed by applying a combination of a reset pulse and a set pulse for each stable point.

Fiber optic subcarrier transmission system using coherence multiplexing techniques for broad-band distribution networks is proposed. This system makes it possible to improve the laser linewidth requirement and also to eliminate the effect of intermodulation distortion (IMD) which is serious problem in subcarrier multiplexed (SCM) system. In the proposed system, the frequency difference, fo, between the reference light and the signal light makes it possible to generate the broadand FM signal after photodetecting. Thus, an increase in the modulation index provides a corresponding increase in receiver sensitivity. We analyze the fundamental performance of the proposed system and derive the signal-to-noise ratio (SNR) at the output of FM demodulator by taking the threshold effect and spike noise into account. The proposed system can achieve the total capacity in excess of 10 GHz, and thus it is attractive for multichannel broad-band distribution networks.

This paper provides an architectural study of optical multiple-ring trunk-transmission networks using high-speed Time Division Multiplexing (TDM), and proposes two algorithms for distributed control environments. We propose a path-setup algorithm that uses Token protocol over Section Overhead (SOH) bytes, by which network-nodes communicate with each other to reserve bandwidth. A classified path restoration algorithm is also proposed that offers 3 path classes in terms of restoration performance. Class A paths, the most reliable, never lose any bit even against unpredictable disasters. They are realized by path-duplication at the source node, route diversity,and hitless switching at the destination node. Class B paths are restored by re-routing, where the original path-setup algorithm is reused. Class C paths are the most economical because a failed path is restored by maintenance action.

This work presents a further development of the approach to modelling thermal (i.e. carrier-velocity-fluctuation) noise in semiconductor devices proposed in papers by the present authors. The basic idea of the approach is to apply classical theory of Ito's stochastic differential equations (SDEs) and stochastic diffusion processes to describe noise in devices and circuits. This innovative combination enables to form consistent mathematical basis of the noise research and involve a great variety of results and methods of the well-known mathematical theory in device/circuit design. The above combination also makes our approach completely different, on the one hand, from standard engineering formulae which are not associated with any consistent mathematical modelling and, on the other hand, from the treatments in theoretical physics which are not aimed at device/circuit models and design. (Both these directions are discussed in more detail in Sect. 1). The present work considers the bipolar transistor compact model derived in Ref. [2] according to theory of Ito's SDEs and stochastic diffusion processes (including celebrated Kolmogorov's equations). It is shown that the compact model is transformed into the Ito SDE system. An iterative method to determine noisy currents as entries of the stationary stochastic process corresponding to the above Ito system is proposed.

A pipelined adaptive digital filter (ADF) architecture based on a two-dimensional least mean square algorithm is proposed. This architecture enables the ADF to be operated at a high clock rate and reduction of the required amount of hardware. To achieve this reduction we introduce a new building unit, called a block, and propose implementing the pipelined ADF using the block, Since the number of blocks in a cell is adjustable, we derive a condition for satisfying given specifications. We show the smallest number of blocks and the corresponding delay can be determined by using the proposed method.

We discuss a new decoder for the multiple-valued signed-digit number, using a current-mode CMOS transistor-oriented circuit structure. In this paper, a new decoding method with the selective summation of a redundantly represented addend "O = [-1 r]" is proposed, where r is the radix and the addend is applied to each digit with a negative value and any consecutively higher digit takes which has a value of O. A newly designed literal linear circuit is realized, which has a current-switch function that makes independently the short path when each digit has a value of O. Through the parallel connections of these current swiches, the same addend signal at the lower digit is transmitted in a higher speed, The decoder circuit is tested by using the general circuit simulation software SPICE and the circuit characteristics of the selective summation of a redundantly represented O addend and the output results of the SD decoding operation were simulated. We also evaluated the decoder circuit in terms of the processing speed and the circuit size.

This paper describes the effectiveness of stream-oriented data-driven scheme for achieving autonomous fault management of hyper-distributed systems such as networks based on the Telecommunications Information Networking Architecture (TINA). TINA, whose specifications are in the finalizing phase within TINA-Consortium, is aiming at achieving interoperability and reusability of telecom applications software and independent of underlying technologies. However, to actually implement TINA network, it is essential to consider the technology constraints. Especially autonomous fault management at run-time is crucial for distributed network environment because centralized control using global information is very difficult. So far many works have been done on so-called off-line management but runtime management of service failure seems immature. This paper proposes introduction of stream-oriented data-driven processors to the autonomous fault management at runtime in TINA based distributed network environment. It examines the features of distributed network applications and technology requirements to achieve fault management of those distributed applications such as effective multiprocessing of surveillance, testing, reconfiguration in addition to ordinary processing.

The technique of common-multiplicand multiplication, CMM, is modified and the similar approach is utilized to enhance the performance of a recently proposed fast exponentiation algorithm by exponent decomposition. On average, the improved exponentiation, its original version, and the traditional right to left binary exponentiation algorithm take 1.292m+11,1.375m+3, and 1.5m multiplications, respectively where m is the bit length of the exponent. Finally, it is shown how to improve the overall performance of an exponentiation by employing the improved exponentiation algorithm, the improved CMM algorithm , and any general purpose fast multiplication algorithm.

As the Asynchronous Transfer Mode (ATM) technology comes to be used widely, the Telecommunications Management Network (TMN) over ATM networks becomes an important issue. Since TMN uses the OSI protocols including the Common Management Information Protocol (CMIP), it is required to implement CMIP communication over ATM networks. In order to realize OSI over ATM, ITU-T SG13 has standardized the Service Specific Coordination Function for Connection Oriented Network Service (SSCF-CONS), Service Specific Connection Oriented Protcol (SSCOP), and the Synchronization and Coordination Function (SCF). We have developed the CMIP software over ATM networks adopting these protocols. The CMIP software is designed so that it achieves both high throughput for large data transfer and short response time for small message exchange. The software adopts the implementation mechanisms commonly applied for protocol modules to reduce the overheads for controlling OSI protocol modules, and some protocol specific mechanisms especially for protocols with heavy processing overheads, i.e. SSCOP and CMIP. The performance evaluation shows that the developed CMIP software achieves more than 200 message exchanges per second for messages whose length is 64 Byte long, and achieves about 36 Mbps throughput for transferring data whose length is more than 100 KByte.

Private networks are becoming globalized and more complicated through LAN-WAN interconnection. While WANs are managed by CMIP, LANs are managed by SNMP. To achieve end-to-end management, the integration of CMIP-based and SNMP-based management is important. We have developed an MI (Management Integration) platform for CMIP-based and SNMP-based management. It provides OSI SMF (Systems Management Function)-based unified basic management services to upper level applications regardless of the differences between CMIP-based and SNMP-based management. It achieves this with two modules: a management information transfer integration module that mainly covers protocol and data format differences between them, and a basic management module that covers functional differences. The translation of management information in the former module can be changed flexibly because the translation is based on an external script file. The latter module has additional SMF-like functions for the management of SNMP agents in addition to SMF manager role functions, etc. Prototype evaluation has demonstrated the feasibility of the MI platform.

We have developed a management agent that adapts the delegation concept to achieve efficient network management. In conventional delegation architecture, a network management operator details management operations in an operation-script that describes management operation flow and such network management functions as event management and path tracing. The operator sends this script to agents to execute. In our delegation architecture, the operator sends only a script skeleton describing management operation flow alone; management functions are built into the agents in the form of fuction objects. This helps keep management traffic low. Each function object is designed by utilizing three operational objects: enhanced, primitive, and communication. Each enhanced operational object (EOO) provides a script skeleton with an individual network management function. A primitive operational object (POO) provides an EOO with managed object (MO) access functions. A communication operational object (COO) provides an EOO with a mechanism for accessing the functions of other remote EOOs. We have tested our design by applying it to a path tracing application, and we have measured the total data transfer size between a manager and an agent and the amount of memory usage in our agent's running environment. Evaluation of our implementation suggests that our design can be applied such network management functions as connection establishment and release, fault isolation, and service provisioning.

An advanced intelligent network (IN) provides service management along with telecommunication services, and has a two-layer architecture, i.e., a transmission layer and an intelligent layer. An advanced IN's programmability is achieved by a service-independent platform of nodes in the intelligent layer, and service-dependent software called logic programs. In contrast to telecommunication services, models for service management have not yet been established. This paper presents both execution and specification models for service management. The execution model is composed of three hierarchies that apply to various kinds of management operation. The specification model has the capability to define the details of data items. The specification language for service management is also proposed. Simulation on dynamic SQL based DBMS solved that; (1) Logic programs for service management can be made small size on the model, and (2) To provide efficient database operation, programmability must be enhanced if service management includes table with variable number of field operation.

We present a high performance AlGaAs/GaAs power HBT with very low thermal resistance for digital cellular phones. Device structure with emitter air-bridge is utilized and device layout is optimized to reduce thermal resistance based on three-dimensional thermal flow analysis, and in spite of a rather thick substrate (100 µm), which achieved a low thermal resistance of 23/W for a multi-finger (440 µm240 fingers) HBT. This 40 finger HBT achieved power added efficiency (PAE) of over 53%, 29.1 dBm output power (Pout) and high associated gain (Ga) of 13.5 dB with 50 kHz adjacent channel leakage power (Padj) of less than -48 dBc under a 948 MHz π/4-shifted QPSK modulation with 3.4 V emitter-collector voltage. We also investigated the difference of RF performance between two bias modes (constant base voltage and current), and found which mode is adequate for each stage in several stage power amplifier for the first time.

In this paper, we propose an efficient task scheduling scheme, called CTS (Class-based Task Scheduling), to obtain high performance in terms of high system utilization and low waiting times for tasks. While a better submesh allocation scheme can improve system performance, an allocation policy alone cannot improve performance significantly. This is due to the fact that the FCFS task scheduling policy leads to large external fragmentation. The CTS strategy maintains four separate queues, one for each incoming task class. This avoids the blacking property incurred in the FCFS scheduling. To reduce the external fragmentation, a job tends to wait for an occupied submesh of the same size instead of using a new submesh in the CTS strategy. Simulation results indicate that the proposed scheduling strategy improves the performance compared to the FCFS scheduling policy by reducing the average waiting delay significantly.

Cross talk in mode-division multiplexing system is studied. The mode patterns when the fiber is bent are observed in the experiment.

This paper describes the relation between the structure and the capability on mesh-connected computers with orthogonal broadcasting. It is shown that algorithms of maximum finding for the two-way communication model can be performed on the one-way communication model without increasing the time complexity.

This paper focuses on recovering from processor transient faults in pipelined multiprocessor systems. A pipelined machine may employ out of order execution and branch prediction techniques to increase performance, thus a precise computation state would not be available. We propose an efficient scheme to maintain the precise computation state in a pipelined machine. The goal of this paper is to implement checkpointing and rollback recovery utilizing the technique of precise interrupt in a pipelined system. Detailed analysis is included to demonstrate the effectiveness of this method.

This paper optimizes a hierarchical image transmission system based on the hierarchical modulation scheme in a band-limited Rayleigh fading channel. Authors analyze relations between hierarchical parameters and the image quality, and show that the existence of optimum hierarchical parameter that maximizes the received image quality.

Silica-based planar lightwave circuits (PLCs) are reviewed in terms of WDM applications. Four types of basic multiplexer are described and compared. Some topical applications of these multiplexers are introduced with their WDM systems. We conclude that because of these various applications, silica-based PLCs will play an important role in future WDM systems.