In the data path circuits of asynchronous systems, logical faults may first manifest as undetectable, transient wrong codewords, in spite of encoding the inputs and the outputs and proper organization which enables the faults to be propagated to the primary outputs in the form of non-codewords. Due to this, the conventional methods of concurrent error detection (CED) using the logic (voltage) monitoring is not effective. In this paper, we suggest a mixed-signal approach to achieve CED for a class of asynchronous circuits, known as self-timed circuits. First, we show that it is impossible to guarantee the CED using logic monitoring of the primary outputs in spite of proper encoding and organization of self-timed circuits. Then, we discuss different manifestations of single stuck-at faults occurring during normal operation in these circuits. Finally, we present the feasibility of achieving CED using a built-in current sensor (BICS) along with encoding techniques.

A wireless tag system has been designed and developed for maintaining and managing outdoor communication facilities. This system employs an infrared (IR) beam and an electromagnetic wave with a radio frequency (RF), and is constructed using IR-RF tags, an IR commander, and an RF receiver. The IR command radiation with strong directivity enables a maintenance operator to recognize a target facility, and the RF response without directivity enables a management system to obtain data from within a large circular area. Solar and secondary batteries are also adopted as the power module in the tag to allow easy maintenance at long intervals. IR signal communication is possible up to a distance of 9 m, and RF signal communication is possible within a circle with a radius of 9 m.

A connection admission control (CAC) that guarantees a negotiated cell-loss ratio for all cell-streams passing through the usage parameter control (UPC) in ATM networks is proposed. In particular, the cases in which a jumping-window, sliding-window, or continuous-leaky-bucket scheme are used for peak-cell-rate policing are discussued, and the upper bound for cell-loss ratio of the cell-streams passing through each type of UPC is derived. The CACs based on the derived cell-loss-ratio upper bounds ensure the quality of service in all cases by combining the relevant UPCs. There are three possible combinations of CAC and UPC, depending on the UPC mechanism used. The impact of the choice of CAC and UPC combination on bandwidth utilization is discussed using several numerical examples.

In the conventional sound field reproduction system with control of the transfer functions from the source to both ears of a listener, a slight shift of the ears caused by movement of the listener inevitably results in sound localization being different from that expected. In this paper, a method for reproducing a sound field by controlling the transfer function from the source to multiple points (called the "method of multiple-points control" hereafter) is applied to a sound reproduction system with the aim of expanding the area which can be controlled. The system is controlled so that the transfer functions from the input of the system to the multiple points adjacent to the original receiving points have the same desired transfer function. By placing the control points at appropriate intervals, a "zone of equalization" is formed. Based on a computer simulation, the intervals between control points is discussed. The configuration of the loundspeakers for sound reproduction is also discussed.

In this paper, in order to achieve the low power consumption of programmable divider in a PLL frequency synthesizer, we propose a new prescaler method for low power consumption. A fixed prescaler is inserted in front of the (N +1/2) programmable divider which is designed based on the new principle. The divider ratio in the loop does not vary at all even if such a prescaler is utilized. Then the permissible delay periods of a programmable divider can be extended to two times as long as the conventional method, and the low power consumption and low cost in a PLL frequency synthesizer have been achieved.

Genetic algorithms have been shown to be very useful in a variety of search and optimization problems. In this paper we present a genetic algorithm for maximum independent set problem. We adopt a permutation encoding with a greedy decoding to solve the problem. The DIMACS benchmark graphs are used to test our algorithm. For most graphs solutions found by our algorithm are optimal, and there are also a few exceptions that solutions found by the algorithm are almost as large as maximum clique sizes. We also compare our algorithm with a hybrid genetic algorithm, called GMCA, and one of the best existing maximum clique algorithms, called CBH. The exiperimental results show that our algorithm outperformed two of the best approaches by GMCA and CBH in final solutions.

A 2.7-V Si-bipolar quadrature modulator with a 90 phase shifter consisting of a frequency doubler and a master-slave flip-flop is described. The modulator operates over a wide bandwidth (0.95 to 1.88 GHz) without any tuning or adjustments. It is implemented using 20-GHz Si-bipolar technology and dissipates 97 mW at 2.7 V. An image ratio of less than -40 dBc is obtained between 1.1 and 1.8 GHz. Moreover, third-order harmonic products are less than -40 dBc and carrier leakage is less than -30 dBc.

We propose a method to make new sequence number (SN*) for AAL 3/4 in ATM networks. This method observes the segment type (ST) and length indicator (LI) fields with sequence number (SN) to make the SN*. Our proposal also includes an example of the method.

We have designed a new current-mode low-voltage, low-power, high-frequency CMOS VCO circuit. The main purpose of this new circuit is to obtain operational capabilities with more than 1 GHz oscillation frequency from one battery cell. The current-mode approach was adopted throughout the circuit design to achieve this. New differential-type delay cells in the current-mode operation enable extremely low supply voltage operation and superior linearity between the oscillation frequency and control voltage of a ring oscillator. A design which combines the transitions of each delay cell output enables the VCO's high-frequency operation. To obtain a sufficient current level at output, a current amplifier with a small amount of positive feedback is used. The unnecessary generation of spectral components caused by mismatched time delay of delay cells in a ring-oscillator, which is an inherent problem of the VCO in a ring-oscillator form, is 0also analyzed. The characteristics of the designed VCO were examined by the SPICE circuit simulation using standard CMOS 0.6µm devices. Operation with a 1 V power supply, 1 GHz oscillation frequency, and 5.7 mW power dissipation was verified.

A new GSM data protocol called high speed circuit switched data (HSCSD) have been developed by European Telecommunications Standards Institute (ETSI) for high speed file transfer and mobile video applications. HSCSD increases data rate by using multiple TDMA time slots (up to 8) instead of one time slot in the current GSM implementation. The problem of multiple time slot assignment is that blocking rate of the system will increase. This problem can be solved by flexible resource assignment where the service specifies the maximum and the minimum capacity. Based on the current available capacity of a base station, a user will be assigned any rate between the maximum and the minimum capacities. This article describes HSCSD protocol and presents four radio resource allocation strategies for HSCSD: always allocates maximum, always allocates minimum, allocates maximum unless available resources are not enough, and allocates resources according to the current blocking statistics of the base station. A simulation model is proposed to investigate the performance of these algorithms. The blocking probability, the call completion probability, and the quality of service are used to evaluate the effects of algorithms in different system behaviors.

A method is proposed for forming hillock-free aluminum-based alloy bus lines for active-matrix liquid-crystal displays (LCDs). Aluminum (Al)-based alloy films are deposited using an Al target containing boron (B) or nickel (Ni) in a sputtering ambient containing nitrogen. The Al-Ni films deposited using an Al target containing Ni showed excellent hillock resistance: virtually no hillock formation after thermal treatment at around 400 and no significant increase in resistivity. These films also showed good patternability with a simple wet etching: a smooth line edge and a gently tapered profile. These films are thus suitable for the bus lines of active matrices.

A low power dual modulus prescaler for frequency synthesizers has been designed in a standard 1.2 µm digital CMOS process using enhancement source coupled logic (ESCL). Being a differential low amplitude current mode logic, ESCL has two interesting characteristics for this design besides low power consumption: the low noise performance, that allows this circuit to be on the same chip with sensitive analog circuitry, and the ability to run with a 200 mV sinusoidal signal as generated from an LC oscillator without the need of a clock amplifier. At 195 MHz and 3 V supply, the current consumption of the prescaler is as low as 289 µA, while maximum operating frequencies of 910 MHz at 5 V and 650 MHz at 3 V are achieved.

A novel adder-free architecture for realizing a small-size π/4-shift QPSK signal generator IC is presented. In order to realize an adder function, analog current-mode addition is utilized instead of digital adders. Impulse responses of a roll-off filter are stored in a ROM as a Δ-Σ modulated one-bit data stream. This can greatly reduce the die size to 0.8mm 0.8mm while maintaining high modulation accuracy. The test chip was fabricated by using the standard 0.8µm CMOS technology, and the chip achieved 1.8% vector modulation error with a 2.7V power supply.

A sequence of nonnegative integers s=(S1, s2, , sn) is a score sequence of an r-tournament if, for some positive integer r, ther is a directed graph with vertices v1, v2, , vn such that deg+(vj)=sj and deg-(vj)=r(n-1) -sj for each j=1, 2, , n. The score sequence problem of an r-tournament is: Given some positive integer r and a sequence of nonnegative integers, determine whether it is a score sequence of an r-tournament or not. In this paper, we consider several variations of the score sequence problem of an r-tournament, and give efficient algorithms.

In this paper, we evaluated performance of mobile exchange control network. Queueing network model is used for modeling of mobile exchange control network. We developed a call control processing and location registration scenario that has a message exchange function between processors in mobile exchange control network. The network symbols are used the simulation models that are composed of the initialization module, message generation module, message routing module, message processing module, message generation module, HIPC network processing module, output analysis module. As a result of computer simulation, we obtain the processor utilization, the mean queue length, the mean waiting time of control network based on call processing and location registration capacity. The call processing and location registration capacity are referred by the number of call attempts in the mobile exchange and must be satisfied with the quality of service (delay time).

The emerging, ATM network will support permanent, semi-permanent and switched virtual channel connections (SVCC). A number of simulation studies have been carried out to study the performance of SVCCs using empirical data. The absence of an analytical model has prevented the study of SVCCs under known traffic distributions. In this paper, we develop a new delayed vacation model to facilitate the performance study of SVCCs with configurable inactivity timer in the ATM network interface card (NIC). Comparison with simulation results indicates that the proposed model is very accurate and can be effectively used to optimise the performance of SVCCs by selecting an appropriate inactivity timer.

This paper presents a novel approach to a soft-output equalizer, which makes a symbol-by-symbol soft-decision based on a posteriori probabilities (APP's) criterion in the presence of intersymbol interference. The authors propose a soft-output Viterbi equalizer (SOVE) employing expanded memory length in a trellis of the Viterbi algorithm with small arithmetic complexity. The proposed equalizer gives suboptimum soft-decision closer to that of a equalizer with the maximum a posteriori probabilities (MAP) algorithm than the conventional SOVE.

Verification of timed bisimulation equivalence is generally difficult because of the state explosion caused by concrete time values. In this paper, we propose a verification method to verify timed bisimulation equivalence of two timed processes using a symbolic technique similar to [1]. We first propose a new model of timed processes, Alternating Timed Symbolic Labelled Transition System (A-TSLTS). In an A-TSLTS, each state has some parameter variables, whose values determine its behaviour. Each transition in an A-TSLTS has a quard predicate. The transition is executable if and only if its guard predicate is true underspecified parameter values. In the proposed method, we can obtain the weakest condition for a state-pair in a finite A-TSLTS, which the parameter values in the weakest condition must satisfy to make the state-pair be timed bisimulation equivalent.

A new structure for adaptive AR spectral estimation based on multi-band decomposition of the linear prediction error is introduced and the mathematical background for the soulution of the related adaptive filtering problem is derived. The presented structure gives rise to AR spectral estimates that represent the true underlying spectrum with better fidelity than conventional LS methods by allowing an arbitrary trade-off between variance of spectral estimates and tracking ability of the estimator along the frequency spectrum. The linear prediction error is decomposed through a filter bank and components of each band are analyzed by different window lengths, allowing long windows to track slowly varying signals and short windows to observe fastly varying components. The correlation matrix of the input signal is shown to satisfy both time-update and order-update properties for rectangular windowing functions, and an RLS algorithm based on each property is presented. Adaptive forward and backward relations are used to derive a mathematical framework that serves as a basis for the design of fast RLS alogorithms. Also, computer experiments comparing the performance of conventional and the proposed multi-band methods are depicted and discussed.

In this letter, a theoretical estimation of pick-up characteristics of the fiber probe of Photon Scanning Tunneling Microscopy based on the Wiener-Hopf technique taken account of the weakly guiding approximation are reported. As a result, it is found that diffracted waves by the extremity of the fiber probe mainly act on the mode excitation rather than transmitted waves, then the pick-up characteristics are well accordance with typical experiments quality and quantity.