Rotating machines such as motors, generate noise at the fundamental frequency and its harmonics. The narrowband active noise control (NANC) algorithm is widely used to cancel such noise. Traditional feedforward NANC systems use non-acoustic sensors to measure rotation speeds, and then a bank of signal generators produce synchronized tonal signals as the reference signals according to the fundamental frequency of the undesired noise. However, the non-acoustic sensors such as encoders usually cost a lot and are not reliable. This study proposes using the feedback ANC structure and incorporates with several adaptive line enhancers (ALEs) to generate the reference signals. Without using non-acoustic sensors, the proposed system only updates the center frequency of the first ALE to track the fundamental frequency change, which greatly reduces complexity of the proposed ANC system. The frequency mismatch (FM) problem is overcome by properly setting the bandwidths of the ALE. Performance were verified by using both simulations and real-time experiments.

The filtered-U recursive least mean square (FURLMS) algorithm for active noise control (ANC) system is derived according to the output-error (OE) model based adaptive infinite impulse response (IIR) filter. This paper develops the ANC system by using the equation-error (EE) model based adaptive IIR filter. Since the weighting vectors in the mean square error (MSE) of the EE model baesd filter is a quadratic function, the EE model is guaranteed to reach the global minimum of MSE by properly choosing the step size. This paper also derives the proposed EE model based ANC system is identical to the hybrid ANC system. Simulation results show the effectiveness of the proposed algorithm.

This study implements mobile-phone camera text-recognition technology into a game-based assessment design. This game is created as an alternative assessment in vocabulary instruction for learning Indonesian as a Foreign Language classroom, to explore the effectiveness and the improvement of students' vocabulary, and to increase students' motivation in conducting assessment. This game is web-based. The web-server stores questions and score. There are two client interfaces. First, the classroom interface randomly downloads questions according to the vocabulary categories chosen by the teacher. Through camera and text-recognition technology, students search for answers, which are projected on the wall. Second, the teacher interface is used to access the score. We expect this system to be an application for the alternative assessment in a vocabulary instruction for learning Indonesian as a Foreign Language.

In this paper, a novel code-shifting technique, which can be added atop asynchronous incoherent optical code-division multiple-access systems without complex modifications, is proposed and studied. The new technique divides the time-slot (or chips), in which the optical pulses of codewords are located, into g equal-width sub-chips; every pulse is randomly and independently shifted to start at one of the g sub-chips of its own chip, where g > 1 is a positive integer. The effects of this random g-shift to the cross-correlation property and performance of asynchronous optical codes (of periodic cross-correlation functions of at most one) are formulated. Although it is found that the periodic crosscorrelation functions are worsened to 3 - 2/g, our theoretical and computer-simulation results show an unconventional finding that code performance improves as g increases.

In this paper, two new families of "synchronous" optical codes, called 1-D and 2-D synchronous multilevel prime codes (SMPCs), are constructed and analyzed for incoherent optical code-division multiple access (O-CDMA). With the benefit of synchronous transmission, the new algebraic codes have expanded cardinality and substantially increase the number of possible subscribers, thus potentially supporting rapid code switching and obscure-nature (privacy and military) communications. In addition, the SMPCs can be partitioned into a tree structure of multiple levels of subsets of codewords. Different cross-correlation functions are obtained from codewords coming from different subsets; code orthogonality is achieved among the codewords within each subset of the lowest level. As code performance is a strong function of the cross-correlation function, the performance of the codewords in use can be adjusted by choosing the subsets from which the codewords originate. The performances of the SMPCs are formulated and also verified by computer simulation. Our analysis shows that code performance can be optimized by applying an "in-order" subset-by-subset code-assignment method to simultaneous users. Besides supporting time-spreading and wavelength-time O-CDMA schemes, the new codes also find applications in passive optical networks and in spectral-amplitude-coding schemes.

A bank of adaptive filters is updated via a parallel or direct/parallel narrowband active noise control (ANC) system uses an error signal. This work presents a delayless filter bank to separate the frequency components of the error signal based on the sinusoidal frequencies of input signals to update the corresponding adaptive filters in a direct/parallel structure. A cost function is also proposed to develop an adaptive algorithm in order to reduce noise and increase convergence speed for this complete direct/parallel narrowband ANC system. Theoretical analysis results demonstrate the increased convergence speed. Moreover, the analysis results and increased noise reduction are verified based on simulation results.

Conventional parallel-form narrowband active noise control (ANC) systems use multiple adaptive filters that are updated by the same error signal. This paper performs theoretical analysis to show that the convergence rate of every adaptive filter will be degraded by the residual error components from other adaptive filters. We develop and analyze a complete parallel narrowband ANC system that uses delayless bandpass filterbank to split the measured error signal, and uses individual error signals to update the corresponding adaptive filters. The foreground bandpass filters are updated by the background adaptive algorithm to tracks frequency change of the primary noise without introducing extra delay in the secondary path. A modified cost function is used to derive algorithm for the complete parallel narrowband ANC. The theoretical analysis and improved performance are verified by computer simulations using measured transfer functions from an experimental setup.

Due to power restriction of some laser sources, the use of same power (per bit duration) in optical codes in incoherent optical code-division multiple-access multimedia networks with variable quality-of-services was previously studied. In those studies, the performance of double-weight codes with the maximum cross-correlation function λc= 1 was exactly analyzed, but an approximation was only applied to the codes with λc> 1 due to mathematical complexity. In this paper, an exact analytical model of double-weight codes with an arbitrary λc≥ 1 is formulated and validated with computer simulation. This general, more accurate performance model is also useful for power-sensitive applications, such as in-service monitoring and fiber-fault surveillance in optical networks and sensor-identification in fiber-sensor systems using optical codes for address or user identification.

Coded modulation with Reed-Solomon (RS) codes has recently been proposed to use atop of frequency-hopping code-division multiple access (FH-CDMA) in order to increase data transfer rate. In this paper, a new method on implementing the modulation and demodulation processes of the RS codes in RS/FH-CDMA is proposed. With the use of our specially "pruned" trellis and the Viterbi algorithm, both processes are simplified and so are their computational complexities. The performance and computational complexities of this RS/FH-CDMA system are analyzed and verified with computer simulation.

To provide differential quality-of-service in optical code-division multiple access, variable-weight codes were proposed and analyzed under a conventional assumption of identical power in every optical pulses (i.e., same chip power). To account for power limit of some laser sources, we assume the use of same optical power in each bit duration (i.e., same bit power) in this paper. For illustration, we focus our study on double-weight codes under both same-chip-power and same-bit-power assumptions. A new and better approximate performance-analytical model for double-weight codes is developed and validated with computer simulation. We show that heavy-weight codes do not always perform better than light-weight codes under the same-bit-power assumption, contrary to previous findings under the same-chip-power assumption.

Two-dimensional (2D) wavelength-time coding schemes have recently been studied for optical code-division multiple access. In this paper, we propose a new family of 2D codes, which use "synchronized" quadratic congruence sequences for wavelength hopping and (n, w, 2, 2) optical orthogonal codes for time spreading. The new 2D codes provide larger (asymptotically optimal) code cardinality than other 2D codes by relaxing the maximum cross-correlation function from one to two. Our study shows that the heavier code weight supported by our 2D codes results in better code performance than some of previously proposed 2D codes (of the maximum cross-correlation functions of one and two). The new codes potentially support more subscribers and heavier bursty asynchronous traffic with gradual performance degradation as traffic load increases.

In this paper, we propose a "two-level" frequency-hopping code-division multiple-access (FH-CDMA) scheme for wireless communication systems. The new scheme provides flexibility in the selection of modulation codes and FH patterns. By partitioning the modulation codes, our two-level scheme can be modified to support more possible users without increasing the number of FH patterns. The performance and spectral efficiency (SE) of the scheme are analyzed. Our results show that the partitioned two-level FH-CDMA scheme supports higher data rate and greater SE than Goodman's frequency-shift-keying FH-CDMA scheme under some conditions.

In this paper, a two-level frequency-hopping code-division multiple-access (FH-CDMA) scheme, which is flexible in the selection of modulation codes and FH patterns, is studied. This two-level FH-CDMA scheme can be modified by the partition of the modulation codes in order to support more subscribers without increasing the number of FH patterns. The performance and spectral efficiency (SE) analyses show that our scheme supports higher data rate and SE than Goodman's frequency-shift-keying FH-CDMA scheme, making the former more attractive for wireless communication systems.

In this paper, a new family of "multilevel" wavelength-time codes with expanded code cardinality, flexible code length, zero autocorrelation sidelobes, and the maximum cross-correlation function of any arbitrary positive integer n is constructed and analyzed. Besides having asymptotically optimal cardinality, the new codes can be partitioned into n levels, such that the cross-correlation function between any two code matrices in level l is at most l, where 1 ¿ l ¿ n. The hardlimiting performance of these multilevel codes is analyzed algebraically. Our results show that the unique partitioning property of these multilevel codes supports a trade-off between code cardinality and performance for meeting different system requirements, such as user capacity and throughput.

This paper proposes an adaptive evolutionary system for active noise control (ANC). The conventional ANC system often utilized filtered-X LMS (FXLMS) algorithm to update the coefficients of the linear finite impulse response (FIR) filter for its simplicity; while the FXLMS algorithm may converge to local minima. This paper uses evolutionary idea, substituting FXLMS algorithm, to prevent the local minima problem. In addition, it does not require identifying the secondary path for the ANC by using the proposed method; therefore, there is no plant information is necessary for designing an ANC system. Computer simulations results show that the proposed method can control the nonlinear noise under several situations very well, without identifying secondary path effectively.

This paper presents an intelligent filter design method with a fixed-point digital signal processor (DSP) and illustrates its performance on the application of active noise cancellation (ANC) system. The proposed designing method uses magnitude and phase compensation techniques to eliminate the errors associated with the nonlinear distortion of analog devices in the application, and hence, to improve the ANC performance. The quantization and rounding errors associated with the fixed-point DSP are also compensated for. Several experiments verify the enhancement.

In this paper, we study a new class of two-dimensional codes, here called multi-level prime codes, with expanded code cardinality by relaxing the maximum cross-correlation function to any arbitrary positive integer n. Besides having asymptotically optimal cardinality and zero autocorrelation sidelobes, these multi-level prime codes can be partitioned into n levels, such that the cross-correlation function between any two code matrices in level l is at most l, where lisin[1, n]. The performance of the new codes in an optical code-division multiple-access system with hard-limiting detection is analyzed. Our results show that the unique partition property of the multilevel prime codes allows the trade-off between code cardinality and performance for meeting different system requirements, such as capacity and throughput.

In this paper, a new family of two-dimensional (2D) wavelength-time codes, which uses one-dimensional (1D) optical orthogonal codes (OOCs) with the maximum cross-correlation value of two as the time-spreading codes is proposed and analyzed. By relaxing the cross-correlation functions to at most two, the new 2D codes can provide larger code cardinality to accommodate more subscribers. They also have better performance than 1D optical codes because they can support heavier code weight, for a given code length. Moreover, our numerical examples show that the heavier code weight supported by our new 2D codes results in better performance than some of our previously proposed 2D codes, which have the maximum cross- correlation value of one.

In this paper, we study a new family of carrier-hopping prime codes (CHPCs), so-called quadratic- congruence CHPC (QC-CHPC), with expanded code cardinality by relaxing the maximum cross-correlation function to two (i.e., lambdac= 2). An application of the new code is for multicode keying in wavelength-time optical code-division multiple access (O-CDMA), in which each user is assigned M = 2mcode matrices to represent m data bits per symbol. The advantages are that 1) a lower baud multicode-keying O-CDMA system can support a higher bit rate and 2) user's code obscurity is enhanced, as compared to the transmission of one code matrix (per user) for each data bit one in conventional "on-off keying" O-CDMA systems. Our performance analysis shows that there is a trade-off between the code performance and hardware complexity/speed related to the choice of M, for a given bit rate.

Quadratic-congruence carrier-hopping prime codes (QC-CHPCs) with zero autocorrelation sidelobes, cross-correlation values of at most two, and expanded cardinality were recently constructed for wavelength-time "multicode-keying" optical code division multiple access (O-CDMA) for improved data throughput and code obscurity. To support multimedia services with different discrete bit-rate requirements, "multiple-length" QC-CHPCs are constructed algebraically in this paper. In contrary to conventional single-length codes, our analysis shows that the performance of these multiple-length codes improves as the code length decreases, thus supporting services prioritization in O-CDMA. Moreover, the relationship of the normalized spectral efficiency (NSE) and code lengths of the multiple-length QC-CHPCs is studied. Our results show that the NSE improves as the number of simultaneous users with short code matrices increases, which, however, decreases the total number of simultaneous users in the system. The choice of which code-length distribution to use depends on whether system efficiency or total number of simultaneous users is more important.

To support multimedia services with different discrete bit-rate requirements, families of multilength optical codes, such as the carrier-hopping prime code (CHPC), extended CHPC, and multiwavelength optical orthogonal code, were recently constructed for wavelength-time optical code-division multiple-access (O-CDMA). In this paper, the performance of these multilength optical codes in a multimedia O-CDMA system with a variable-weight operation are analyzed. Our study shows that short-length codes generate stronger interference than long-length codes. This supports services prioritization in O-CDMA. Our study also shows that code weight is a more important factor than code length in determining code performance (i.e., quality of service).

To support multimedia services with different discrete bit-rate requirements, families of multilength optical codes, such as the carrier-hopping prime code (CHPC), extended CHPC, and multiwavelength optical orthogonal code, were recently constructed for wavelength-time optical code-division multiple-access (O-CDMA). In this paper, the performances of these multilength optical codes in a multimedia O-CDMA system with a variable-weight operation are analyzed. Our study shows that short-length codes generate stronger interference than long-length codes. This supports services prioritization in O-CDMA. Our study also shows that code weight is a more important factor than code length in determining code performance.

In this paper, we propose the use of Reed-Solomon (RS) code sequences for modulation on top of a frequency-hopping code-division multiple access (FH-CDMA). Our analysis shows that this RS/FH-CDMA scheme supports higher data rate but worse performance than the conventional -ary frequency-shift-keying FH-CDMA scheme. These two schemes provide a tradeoff between the data rate and the performance.

Overhead cranes are common industrial structures that are used in many factories and harbors. They are usually operated manually or by some conventional control methods, such as the optimal and PLC-based methods. The theme of this paper is to provide an effective all-purpose adaptive fuzzy controller for the crane. This proposed method does not need the complex dynamic model of the crane system, but it uses trolley position and swing angle information instead to design the fuzzy controller. An adaptive algorithm is provided to tune the free parameters in the crane control system. The ways to speed the transportation and reduce the computational efforts are also given. Therefore, the designing procedure of the proposed controller will be very easy. External disturbance, such as the wind and the hit, which always deteriorates the control performance, is also discussed in this paper to verify the robustness of the proposed adaptive fuzzy algorithm. At last, several experimental results with different wire length and payload weight compare the feasibility and effectiveness of the proposed scheme with conventional methods

An enhanced adaptive sliding mode fuzzy approach is applied to control the position and load swing of a 3D overhead crane system. The merits of this method include the robustness and model free properties of the sliding mode and fuzzy logic controllers, respectively. An adaptable slope of sliding surface is presented and the chattering phenomenon of sliding mode control is also discussed to enhance the control performance. Furthermore, this paper provides a compensating algorithm to the control deadzone of overhead crane system. At last, several simulation results demonstrate the effectiveness.

In this paper, we propose a new fast frequency-hopping code-division multiple-access (FH-CDMA) scheme, in which prime sequences are used for modulation on top of FH-CDMA. The new prime/FH-CDMA scheme supports higher data rate than the conventional M-ary frequency-shift-keying FH-CDMA (MFSK/FH-CDMA) scheme, at the expense of worsening cross-correlation values. The performance and normalized spectral efficiency of both schemes are analyzed and compared. Our results show that the prime/FH-CDMA scheme, in general, utilizes similar system efficiency as the MFSK/FH-CDMA scheme and that both schemes provide a trade-off between data rate and performance.

We propose a modified bipolar-bipolar code for wavelength-time optical code-division multiple access. The new code uses Gold sequences for time spreading, in place of Barker sequences in our previously proposed bipolar-bipolar code. The new code has a cardinality of N+1 times greater than the original code, because there exist N+2 Gold sequences, but only one Barker sequence, for a given code length N. Since the new code is modified from the original code, there is no increase in hardware complexity. The average performance of the new code is analyzed and found very close to that of the original code. In other words, the new code can support greater cardinality without worsening average performance or increasing hardware complexity.

This paper first reviews an extended family of carrier-hopping prime codes (CHPC) with expanded (asymptotically optimal) cardinality and ideal correlation properties. They are designed for wavelength-time optical code-division multiple-access (O-CDMA) applications with broadband lasers, in which there are extra numbers of available wavelengths. The performance of the extended CHPC is analyzed and compared to a wavelength-grouping scheme using the original CHPC. Furthermore, the traditional pessimistic chip-synchronous assumption used in performance analysis of 2D codes with cross-correlation functions of at most one is removed for a more realistic error probability. In addition to the Gaussian approximation, we introduce in this paper a more accurate combinatorial method, especially when the number of simultaneous users is small.

In this paper, a new class of carrier-hopping codes for frequency-hopping wireless and wavelength-hopping fiber optic code-division multiple-access (CDMA) is constructed by modifying the original carrier-hopping prime codes. The new carrier-hopping prime codes possess expanded and asymptotically optimal cardinality, zero autocorrelation side-lobes, and cross-correlation functions. The performance analysis of the new codes will be given and compared to the carrier-grouping scheme. Under the best scenario that a central controller is used to uniformly distribute all simultaneous users over groups of carriers in the grouping scheme, the results show that the new codes perform as good as the grouping scheme if the traffic load is heavy

In this paper, a new family of wavelength-time codes, called multiple-wavelength optical orthogonal codes (MWOOCs), is constructed. The new codes use prime sequences for wavelength permutations on top of a time-spreading OOC. The advantage is that the code cardinality is a quadratic function of the number of wavelengths. This property is particularly useful in high bit-rate optical CDMA applications, in which the number of time slots is very restricted. This limitation can be compensated and even improved in our MWOOCs by increasing the number of available wavelengths, through the use of lasers with broadened supercontinuum spectrum