In an iterative decoding algorithm, such as Chase Type-II decoding algorithm and its improvements, candidate codewords for a received vector are generated for test based on a bounded-distance decoder and a set of test error patterns. It is desirable to remove useless test error patterns in these decoding algorithms. This paper presents a sufficient condition for ruling out some useless test error patterns. If this condition holds for a test error patterns e, then e can not produce a candidate codeword with a correlation metric larger than those of the candidate codewords generated already and hence e is useless. This significantly reduces the decoding operations in Chase type-II decoding algorithm or decoding iterations in its improvements.

The symbol basis side information generated by Viterbi's ratio threshold test technique is proposed to improve the performance of the asynchronous slow-frequency-hopped multiple access system with BFSK signaling in the frequency non-selective fading channel. By properly setting the ratio threshold to produce erasure decisions for the received symbols, the system performances are optimized. The relationship among the hit symbols in a hop duration is exploited by this symbol basis side information to greatly reduce the packet error probability. This packet error rate improvement can be as large as two order of magnitude, compared with perfect hop basis side information systems.

In [1] a generalized concatenated code was used to construct the t-fold unidirectional b-bit-byte error-correcting/d(dt)-fold unidirectional b-bit-byte error-detecting (t-UbEC/d(t)-UbED) codes. The concatenated code is to choose an inner code satisfying some disjoint sets and each set is a binary b-tuples unordered code. However, [1] gave five methods including trial and error to construct the optimal inner codes. Here, we present a systematic method for constructing the inner codes. It is shown that we can improve the coding efficiency for t-UbEC/d(t)-UbED) codes in some cases by using our inner codes.

In this paper, we propose a new multicast address scheme based on bit map address (BA) and vertex isolation address (VIA) schemes. The proposed scheme can be utilized by the self-routing switch in a speed manner, while preserving the multicast capability. We analyze the processing delay of the proposed scheme and show the efficiency.

This paper describes short pulse generation at over 40 GHz using monolithic mode-locked lasers integrated with electroabsorption modulators. The electroabsorption modulator using strained-InGaAsP multiquantum wells provides a pulse shortening gate at a high-repetition frequency. Pulse generation around 4 ps has been realized at a repetition frequency of 43. 5 GHz. Pulse compression using a 1. 3 µm single mode fiber is performed and a 0. 87 ps pulse is obtained.

This paper analyzes pulse characteristics of actively mode-locked fiber lasers by including the group-velocity dispersion and the Kerr nonlinearity of the fiber, both of which have not been taken into account in the conventional theory of mode locking. We show that chirped sech pulses are generated from nonlinear and dispersive fiber lasers. By considering the stability of the laser, we also derive design rules for the generation of ultra-short pulses.

We examine effects of higher order dispersion and optical non-linearity, including linear attenuation on intense short pulses propagating along solid and Noble-gas-filled wave-guides. In order to simulate realistic pulse and spectral shapes, we have taken into account quadratic and cubic dispersion as well as Raman (solid wave-guide) and shock nonlinear terms in the generalized Schrodinger equation of propagation. The phonon oscillation corresponding to 13. 3 THz in SiO2 gets superimposed on to the exit pulse in the normal dispersion regime of solid fiber for lengths exceeding 6LDLNL. The super continuum spectrum from hollow Noble-gas-filled fibers shows remarkably deep modulations.

This paper discusses an ATM based access system for a broadband access network that provides flexible and cost effective multimedia services for mass consumption including households. The access system proposed herein uses ATM-PDS subscriber transmission technologies, thus enabling multiple users to share a single fiber resource while transmitting or receiving multimedia information within the broadband network. The system also has virtual channel concentration function by using the bearer connection control protocol being studied for VB5. 2 interface in the ITU-T. We show that the virtual channel concentration function reduces the access cost per user. We also discuss multiple QoS control methods in the system to provide multiple services efficiently. This paper evaluates two methods to handle ABR class and UBR class traffic: shared bandwidth with preferred ABR method, and guaranteed bandwidth with overriding method. The result indicates that when using the shared bandwidth with preferred ABR method for the access system, ABR throughput and UBR throughput per VC depend on the proportion of the number of ABR-VC connections to the total active VCs and on the each buffer size in the access system. And it is difficult to control ABR-VC and UBR-VC throughputs in the access network by using the shared bandwidth with preferred ABR method, which simple mechanism. With the guaranteed bandwidth with overriding method, while ABR-VC throughput and UBR-VC throughput also depend on the proportion of ABR-VCs to the total VCs and on the buffer size, it can offer the minimum guaranteed throughput to the UBR traffic. The result shows the method is effective for easy service provisioning.

In this paper, we develop a novel method for tuning parameters known as the sensitivity parameters of membership functions used in a fuzzy classifier. The proposed method performs tuning by solving a set of inequalities. Each inequality represents a range of the ratio of the sensitivity parameters between the corresponding pair of classes. The range ensures the maximum classification rate for data of the two corresponding classes used for tuning. First, we discuss how such a set of inequalities is derived. We then propose an algorithm to solve the derived set of inequalities. We demonstrate the effectiveness of the proposed tuning method using two classification problems, namely, classification of commonly used iris data, and recognition of vehicle licence plates. The results are compared with those obtained by using the existing tuning method and with those by neural networks.

This paper deals with an orthogonal functional expansion of a non-linear stochastic functional of a stationary binary sequence taking 1 with unequal probability. Several mathematical formulas, such as multivariate orthogonal polynomials, recurrence formula and generating function, are given in explicit form. A formula of an orthogonal functional expansion for a stochastic functional is presented; the completeness of expansion is discussed in Appendix.

The aim of this study is to offer additional experimental evaluation on learning algorithms for artificial neural networks by testing and comparing the normalized backpropagation algorithm (NBP), previously proposed by the authors, and six other alternatives based on a particular application to financial forecasting. The algorithms are the original backpropagation (OBP), the NBP, backpropagation with momentum (two versions), the delta-bar-delta, the superSAB, the rprop and the quickprop algorithm.

We present a finite-difference time-domain (FD-TD) method with the perfectly matched layers (PMLs) absorbing boundary condition (ABC) based on the multidimensional wave digital filters (MD-WDFs) for discrete-time modelling of Maxwell's equations and show its effectiveness. First we propose modified forms of the Maxwell's equations in the PMLs and its MD-WDFs' representation by using the current-controlled voltage sources. In order to estimate the lower bound of numerical errors which come from the discretization of the Maxwell's equations, we examine the numerical dispersion relation and show the advantage of the FD-TD method based on the MD-WDFs over the Yee algorithm. Simultaneously, we estimate numerical errors in practical problems as a function of grid cell size and show that the MD-WDFs can obtain highly accurate numerical solutions in comparison with the Yee algorithm. Then we analyze several typical dielectric optical waveguide problems such as the tapered waveguide and the grating filter, and confirm that the FD-TD method based on the MD-WDFs can also treat radiation and reflection phenomena, which commonly done using the Yee algorithm.

We present a collection of new network control protocols for high-speed networks that are geared to overcome some of the important drawbacks of existing protocols, namely (a) the inefficiencies of existing wait-for-reservation type of protocols for multigigabit wide area networks, (b) the implementation difficulties of credit-based flow control schemes, and (c) the packet resequencing problem of deflection-based schemes. Two of the protocols that will be outlined here were designed in the context of the DARPA sponsored Thunder and Lightning project, at the University of California, Santa Barbara, which is a continuing research effort to design and build a virtual-circuit switched, ATM-based, fiber optic network operating at link speeds of up to 40 Gb/s (see, for instance). The third protocol was designed in the context of MOST project, which is a project on (almost) all-optical switching supported by DARPA. All protocols achieve lossless transmission, efficient utilization of the capacity, and minimum pre-transmission delay for delay-sensitive traffic.

Fundamental nonlinear filters including M-filters and order statistic filters are formulated generally by the maximum a-posteriori (MAP) estimation and some filters are derived with the aid of the Bayes formula. This MAP-filters reduces to M-filters if a-priori probability distribution is uniform, while the rank filters are derived when a-priori bias exists in the MAP estimation. This MAP-filters are implemented with an analog electronic circuit and the log-likelihood is shown to be a Liapunov function for the dynamics of this circuit.

Optimization of InGaAs/InAlAs multiple quantum well structures for high-speed and low-driving modulation, as well as polarization insensitivity and low chirp, was investigated as a function of well thickness and strain magnitude. As a result, very short optical pulses with 4-6 ps was obtained using a low driving-voltage (<2. 0 Vpp) electroabsorption modulator module operating at a 40-GHz large signal modulation. Small chirp operation for low insertion loss (<8 dB from fiber-to-fiber) with prebias was also demonstrated and the product of the pulse width and the spectral width was estimated to be 0. 39 for a 5 ps pulse width that is nearly transform-limited.

Electroabsorption modulators are high speed devices that are rapidly being commercialised and finding applications in a number of areas, particularly in telecommunications. A CW laser diode modulated by an electroabsorption modulator constitutes an extremely stable, robust and simple source of high quality, high repetition rate ultrashort optical pulses. In this paper we describe the capabilities and limitations of such pulse sources, and present nonlinear pulse compression and manipulation techniques that allow one to overcome these limitations. We also present the design of a new class of comb-like dispersion-profiled fibre compressor. Such a compressor is easily fabricated from commercially available fibres and represents a simple yet powerful way of extending the range of pulse durations available. As the electroabsorption modulator is essentially a high speed switch it is also applicable to optical processing problems, and we report the application of such a device to demultiplexing.

The address-based queues are widely used in shared buffer ATM switches to guarantee the order of the cell delivery. In this paper, we propose an address-based queue mechanism to achieve an efficient use of the shared memory under a multicast service. In the switch, both cells and the address queues share the common memory. Each queue length changes flexibly according to the number of the stored cells. Our approach significantly reduces the cell loss probability as compared with the previously proposed approaches.

The Non-stop Service-Enhanceable Software (NOSES) platform was developed as part of our overall plan to establish a communications software platform that can be customized for use by various communications systems, such as STM, ATM and IN. The developed NOSES techniques are call-recovery restart, system file update, and on-line partial file modification, so called "Plug-in"; they were achieved by using dynamic program modification. A system-file update inevitably affects calls in service, despite efforts to save in-service calls by copying the call data from the old file to the new one. We therefore developed a different approach: Plug-in modification. This paper evaluates the applicability of the plug-in mechanism of the NOSES platform. Plug-in is a dynamic partial-file modification technique that does not affect calls in service in a communication switching system. In order to apply plug-in program modification widely, the static and dynamic properties of the modified software must be considered. Therefore, an applicability judgement matrix is introduced. The evaluated applicability of plug-in based on case studies and field data was about 60% for service feature additions and modifications. Thus, plug-in is effective for file maintenance of switching systems from the viewpoint of quick provisioning of new service features and bug fixes.

The Optimal Packet Length (OPL) in packet-switched communication systems has been studied in the literature from various aspects. In this paper, we consider the trade-off between packet length and data transmission delay in a high-speed communication system. To simplify the analysis of the mean data transmission delay, the model is limited to a point-to-point communication system, in which each node complies with the OSI reference model. In order to study the relationship between the OPL and the number of modules performing each protocol, two model communication systems are discussed. In one each node contains two layered protocol modules, and in the other three. Moreover, for both models, the mean data transmission delay is analyzed for two cases depending on whether or not the DLC layer or the network layer performs retransmissions. After studying the OPL which minimizes the mean data transmission delay in each case, we discuss the relationships between the OPLs and the various protocol parameters.

Since an orthogonal multi-carrier signal has large peak power, intermodulation distortion occurs due to the non-linearity of the power amplifier. This distortion severely deteriorates the performance of the multi-carrier system. Especially when carriers are modulated by information bits which produce the same phase shift or the alternative phase shift, the modulated signal has maximum peak power at the input of the amplifier. In order to avoid these phase shifts (code sequences), we propose a code reversal technique which suppresses the maximum peak power of multi-carrier signals for intermodulation compensation. This method utilizes the reversal codes which are added to the original information bits. We also show the effectiveness of the code reversal technique combined with error correction coding and examine the optimum operating point of the amplifier.