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This article presents information about the journal "IEEE Transactions on Circuits and Systems," as of December 2003. From January 2002 to October 2003, the journal received about 1200 research papers. The number of papers per working day has increased continuously. The rejection ratio for the papers arriving after January 2002 , with the review completed, was about 70%. In spite of significant improvement and the efforts of more than 40 associate editors, 9% of the papers received were without the first review after 145 days. The author says that new areas introduced by the journal have not attracted too many papers. Therefore, those subject areas have been more precisely defined in the journal. Computer and computing aspects are influencing everyday work, including design and manufacturing.

The papers appearing in this special issue of the "IEEE Transactions on Software Engineering" periodical are based on papers that originally appeared in the proceedings of the First International Conference on Data Engineering which was held in Los Angeles, California, on April 25-27, 1984. The paper by Braegger, Dudler, Rebsamen and Zehnder was selected as the best paper at the conference by the awards committee, and concerns a database tool called Gambit. This design tool is based on an extended relational/entity relationship model and assists the designer with a wide variety of subtools. The paper by Farmer, King, and Myers is also about a design tool which is called the Semantic Database Constructor (Sedaco). It is based on a semantic data model which buffers the designer from most low level data structuring issues.

This paper introduces a space-time decision feedback equalizer whose coefficients are recursively renewed on the basis of the modified affine projection algorithm (APA). Despite its effectiveness against a rank-deficiency problem, the complexity of the conventional APA utilizing the sample matrix inversion is considerable. Furthermore, the shift invariance property could not be exploited in the case of a space-time decision-directed equalizer (STDE) application. To overcome such challenges, this paper introduces an APA employing a hyperplane projection scheme to reduce computational complexity without any degradation in its convergence characteristic and tracking capability. The performance of the proposed equalization methodology is verified by showing its superior bit error rate behaviors, fast convergence property, and reduced computational complexity by performing adaptive STDE under the single-input-multiple-output wireless multipath fading channel. [ABSTRACT FROM AUTHOR]

This paper proposes a spatio-temporal technique for estimating the noise variance in noisy video signals, where the noise is assumed to be additive white Gaussian noise. The proposed technique utilizes domain-wise (spatial, temporal, and spatio-temporal) video information independently for improved reliability. It divides the video signal into cubes and measures their homogeneity using Laplacian of Gaussian based operators. Then, the variances of homogeneous cubes are selected to estimate the noise variance. A least median of squares robust estimator is used to reject outliers and produce domain-wise noise variance estimates which are adaptively integrated to obtain the final frame-wise estimate. The proposed technique estimates the noise variance reliably in video sequences with both low and high video activities (e.g., fast motion or high spatial structure) and it produces a maximum estimation error of 1.7-dB peak signal-to-noise ratio. The proposed method is fast when compared to referenced methods. [ABSTRACT FROM AUTHOR]

Data broadcasting is an efficient way of delivering data to mobile clients having a high degree of commonality in their demand patterns. This paper proposes the use of multiple directional antennas to increase the performance of an adaptive wireless push system in environments that are characterized by the locality of client demands. Simulation results reveal that using up to three antennas suffices for a significant performance increase over the single-antenna adaptive wireless push system. [ABSTRACT FROM AUTHOR]

In this paper, we study the effect of channel estimation error at the receiver on the mutual information of a multiple-input-multiple-output (MIMO) channel obeying correlated Rayleigh fading. We assume that perfect knowledge of the channel correlation is available at the receiver and find upper and lower bounds on the mutual information for Gaussian input signals. We prove that for a generic input covariance matrix, the gap between these two bounds at high transmit powers does not exceed a certain value, which depends on the number of nonzero eigenvalues of the receive correlation matrix. We also show that in a system with uncorrelated transmit antennas and correlated receive antennas and with uniform power distribution over the transmit antennas, these bounds are asymptotically tight for a large number of transmit antennas. We show that when the correlation information is available at the transmitter, the transmitting strategy that maximizes the mutual information lower bound is to transmit toward the directions of the eigenvectors of the transmit correlation matrix. We further derive upper and lower bounds on the mutual information of a MIMO multiple-access channel with imperfect channel estimation at the receiver. We also prove that when the input power at each user is uniformly distributed over its transmit antennas, the bounds on the mutual information are asymptotically tight for Gaussian input signals, and this tightness increases when the number of users increases. Numerical simulations are conducted to corroborate theoretical results. [ABSTRACT FROM AUTHOR]

This paper addresses the problem on blindly estimating the channel impulse response (CIR) and the carrier frequency offset (CFO) in the uplink transmissions of multiuser code division multiple access system. Two blind subspace-based CIR and CFO estimation methods, namely, the exact determinant minimization method and the approximate determinant minimization method, are proposed. The performance of the proposed methods is compared with the available solution based on the generalized eigenvalue problem method (GEVPM). The computational complexity of the proposed methods is compared with that of GEVPM and the estimator proposed by Li and Liu. Simulation results are given to show that the proposed methods give better performance than the GEVPM and have a wide CFO acquisition range. [ABSTRACT FROM AUTHOR]

With the advance of integration technology, it has become feasible to implement a microprocessor, a vector unit, and a multimegabyte bank-interleaved L2 cache on a single die. Parallel access to strided vectors on the L2 cache is a major performance issue on such vector microprocessors. A major difficulty for such a parallel access is that one would like to interleave the cache on a block size basis in order to benefit from spatial locality and to maintain a low tag volume, while strided vector accesses naturally work on a word granularity. In this paper, we address this issue. Considering a parallel vector unit with 2n independent lanes, a 2n bank interleaved cache, and a cache line size of 2k words, we show that any slice of 2n+k consecutive elements of any strided vector with stride 2r R with R odd and r ≤ k can be accessed in the L2 cache and routed back to the lanes in 2k subslices of 2n elements. [ABSTRACT FROM AUTHOR]

In the past few years, exception support for memory functions such as virtual memory, informing memory operations, software assist for shared memory protocols, or interactions with processors in memory has been advocated in various research papers. These memory traps may occur on a miss in the cache hierarchy or on a local or remote memory access. However, contemporary, dynamically scheduled processors only support memory exceptions detected in the TLB associated with the first-level cache. They do not support memory exceptions taken deep in the memory hierarchy. In this case, memory traps may be late, in the sense that the exception condition may still be undecided when a long-latency memory instruction reaches the retirement stage. In this paper we evaluate through simulation the overhead of memory traps in dynamically scheduled processors, focusing on the added overhead incurred when a memory trap is late. We also propose some simple mechanisms to reduce this added overhead while preserving the memory consistency model. With more aggressive memory access mechanisms in the processor we observe that the overhead of all memory traps--either early or late--is increased while the lateness of a trap becomes largely tolerated so that the performance gap between early and late memory traps is greatly reduced. Additionally, because of caching effects in the memory hierarchy, the frequency of memory traps usually decreases as they are taken deeper in the memory hierarchy and their overall impact on execution times becomes negligible. We conclude that support for memory traps taken throughout the memory hierarchy could be added to dynamically scheduled processors at low hardware cost and little performance degradation. [ABSTRACT FROM AUTHOR]

In this paper, we perform a comparative study of both the achievable performance and the associated computational complexity of two major time-domain prediction strategies proposed for employment in wireless mobile communication systems. Specifically, we investigate the intrinsic design tradeoffs of the so-called stationary robust predictor and the adaptive Recursive-Least-Squares (RLS) predictor. We demonstrate that the RLS predictor outperforms its robust counterpart at a cost of slightly higher computational complexity, and hence, the RLS predictor constitutes a better alternative for employment in wireless transceivers. [ABSTRACT FROM AUTHOR]

Queue length oscillation at a congested link causes many undesirable properties such as large delay jitter, underutilization of the link and packet drops in burst. The main reason of this oscillation is that most queue management schemes determine the drop probability based on the current traffic without consideration on the impact of that drop probability on the future traffic. In this paper, we propose a new active queue (AQM) scheme to reduce queue oscillation and realize stable queue length. The proposed scheme measures the current arrival and drop rates, and uses them to estimate the next arrival rate. Based on this estimation, the scheme calculates the drop probability which is expected to realize stable queue length. We present extensive simulation with various topologies and offered traffic to evaluate performance of the proposed scheme. The results show that the proposed scheme remarkably reduces queue length oscillation compared to other well-known AQMs. It is also shown that the proposed scheme improves fairness among TCP flows due to the stable drop probability, and maintains high utilization with small queue length. [ABSTRACT FROM AUTHOR]

In this paper, we propose a systematic approach that approximates a target dictionary to reduce the complexity of a matching pursuit encoder. We combine calculation of the inner products and maximum atom extraction of a matching pursuit video coding scheme based on eigendictionary approximation and tree-based vector quantization. The approach makes the codec design and optimization cleaner and more systematic than previous dictionary approximation methods. We vary the quality of approximation to demonstrate the tradeoff between computational complexity and coding efficiency. The experiment results show that our codec achieves speed-up factors of up to 100 with a performance loss of less than 0.1 dB. We use double-stimulus impairment scale scores to evaluate the perceptual quality of our approach for different levels of complexity. [ABSTRACT FROM AUTHOR]

In this paper, we present a new concurrent error-detection scheme by hybrid signature to the online detection of program memory and control flow errors caused by transient and intermittent faults. The proposed hybrid signature-monitoring technique combines the vertical signature with the horizontal signature schemes. We first develop a new vertical signature based on linear additive code whose signature length could be easily adjusted. The attribute of adjustable length in vertical signature offers the feasibility to integrate the vertical signature, horizontal signature, and length of block into a single signature word. The horizontal signature mechanism can compensate for the coverage degradation due to the reduction of vertical signature length and significantly decrease the error-detection latency as well. The extensive block-based bit-error simulation and hardware-based simulated fault injection experiment are conducted to validate the effectiveness of the proposed technique. Compared to the continuous signature monitoring (CSM) scheme, there are several notable enhancements accomplished in our work. One is the fault model used in our work is more realistic than the model employed in CSM. Another is the hardware-based experiments are performed so as to measure the design parameters more accurately. The final one is our scheme does not require being equipped with SEC-DED code in program memory in order to achieve the horizontal signatures if instruction bit correction is not an essential demand; as a result, our scheme is more flexible than CSM. [ABSTRACT FROM AUTHOR]

Denormalized numbers are the most difficult type of numbers to implement in floating-point units. They are so complex that certain designs have elected to handle them in software rather than in hardware. Traps to software can result in long execution times, which renders denormalized numbers useless to programmers. This does not have to happen. With a small amount of additional hardware, denormalized numbers and underflows can be handled close to the speed of normalized numbers. This paper will summarize the little known techniques for handling denormalized numbers. Most of the techniques described here only appear in tiled or pending patent applications. [ABSTRACT FROM AUTHOR]

Processor fault diagnosis takes an important role in fault-tolerant computing on multiprocessor systems. There are two classical diagnosis strategies-the precise strategy and the pessimistic strategy, both of which are based on the well-known PMC diagnostic model. Nevertheless, the degree of diagnosability of the system is limited under these two strategies. A better method, called the t/k-diagnosis strategy, is proposed by Somani and Peleg, in which the identified fault-set is allowed to contain at most k fault-free processors. Using this diagnosis strategy, the degree of diagnosability of the hypercube increases greatly as the number of the fault-free processors in the fault-set increases. In this paper, we study the t/k-diagnosability of so-called BC graphs that include hypercubes crossed cubes, Mäbius cubes, and twisted cubes, etc. We show that any n-dimensional BC graph is t(n, k)/k-diagnosable when n ≥ 4 and 0 ≤ k ≥ it, where t(n, k) = (k + 1)n -½ (k + 1)(k +2) + 1. Therefore, the crossed cube, the Mäbius cube, and the twisted cube all have the same t/k-diagnosability as the hypercube. As a result, the algorithms developed for diagnosis on the hypercube may also be used to diagnose multiprocessor systems whose network topologies are based on BC graphs. [ABSTRACT FROM AUTHOR]

We investigate the dominant frequency-dependent systematic-error. signals (SESs) in the ac Josephson voltage standard. We describe our error measurement technique and a num- ber of methods to reduce the errors. Most importantly, we found that a small change in on-chip wiring significantly reduces the SES, improves SES measurement stability, and enables a suitable bias correction method. We show that direct analog-to-digital converter measurements of the SES of two on-chip Josephson arrays are in very good agreement with errors inferred from ac-dc transfer standard measurements. Finally, we demonstrate that the reduction of the SES using these techniques greatly improves the agreement between the ac-dc differences of the two arrays as well as the absolute ac voltage accuracy. [ABSTRACT FROM AUTHOR]

Most statistical background subtraction techniques are based on the analysis of temporal color/intensity distribution. However, learning statistics on a series of time frames can be problematic, especially when no frame absent of moving objects is available or when the available memory is not sufficient to store the series of frames needed for learning. In this letter, we propose a spatial variation to the traditional temporal framework. The proposed framework allows statistical motion detection with methods trained on one background frame instead of a series of frames as is usually the case. Our framework includes two spatial background subtraction approaches suitable for different applications. The first approach is meant for scenes having a nonstatic background due to noise, camera jitter or animation in the scene (e.g., waving trees, fluttering leaves). This approach models each pixel with two PDFs: one unimodal PDF and one multimodal PDF, both trained on one background frame. In this way, the method can handle backgrounds with static and nonstatic areas. The second spatial approach is designed to use as little processing time and memory as possible. Based on the assumption that neighboring pixels often share similar temporal distribution, this second approach models the background with one global mixture of M Gaussians. [ABSTRACT FROM AUTHOR]

Image sequence prediction is widely used in image compression and transmission schemes such as differential pulse code modulation. In traditional predictive coding, linear predictors are usually adopted for simplicity. The nonlinear Volterra predictor can be employed as an alternative to linear predictors to compensate for the nonstationary and non-Gaussian nature of image sequences. Although the Volterra predictor avoids the smoothing effects introduced by linear predictors, it generally amplifies noise contamination present in the images. In this letter, we propose a nonlinear polynomial weighted median (PWM) predictor for image sequence. The proposed PWM predictor is more robust to noise, while still retaining the information of higher order statistics of pixel values. Experimental results illustrate that the PWM predictor yields good results in both high and low motion video. It is especially suitable for high motion sequence in noisy case. The proposed scheme can be incorporated in new predictive coding systems. [ABSTRACT FROM AUTHOR]

In this letter, we investigate the error resilience properties of JPEG2000. We identify the dependencies among coding passes of a codeblock codestream, and determine the sections of the codestream that can be salvaged in the presence of errors. In our analysis, we consider the effects of mode variations provided by the standard. The proposed methods are derived using the existing dependency structure of coding passes and do not require a substantial increase in computational complexity of the decoder. Experimental results indicate that the proposed methods can improve the error resilience performance substantially. [ABSTRACT FROM AUTHOR]

The problem of fault diagnosis has been discussed widely and the diagnosability of many well-known networks has been explored. Under the PMC model, we introduce a new measure of diagnosability, called local diagnosability, and derive some structures for determining whether a vertex of a system is locally t-diagnosable. For a hypercube, we prove that the local diagnosability of each vertex is equal to its degree under the PMC model. Then, we propose a concept for system diagnosis, called the strong local diagnosability property. A system G(V, E) is said to have a strong local diagnosability property if the local diagnosability of each vertex is equal to its degree. We show that an n-dimensional hypercube Qn has this strong property, n ≥ 3. Next, we study the local diagnosability of a faulty hypercube. We prove that Qn keeps this strong property even if it has up to n - 2 faulty edges. Assuming that each vertex of a faulty hypercube Qn, is incident with at least two fault-free edges, we prove Qn keeps this strong property even if it has up to 3(n - 2) - 1 faulty edges. Furthermore, we prove that Qn, keeps this strong property no matter how many edges are faulty, provided that each vertex of a faulty hypercube Qn, is incident with at least three fault-free edges. Our bounds on the number of faulty edges are all tight. [ABSTRACT FROM AUTHOR]

Traditionally, computer security education falls into two distinct classes. The first is training, marked by an emphasis on particular systems, situations, or environments rather than broad principles. The second is scholarly (or scholarship), marked by an emphasis on underlying principles, concepts, and their application. The paper discusses a training course on Unix security, a scholarly course on computer security and the role of research in training education and scholarly education [ABSTRACT FROM PUBLISHER]