In this paper, we propose a new software reliability growth model which is the mixture of two exponential reliability growth models, one of which has the reliability growth and the other one does not have the reliability growth after the software is released upon completion of testing phase. The mixture of two such models is characterized by a weighted factor p, which is the proportion of reliability growth part within the model. Firstly, this paper discusses an optimal software release problem with regard to the expected total software cost incurred during the warranty period under the proposed software reliability growth model, which generalizes Kimura, Toyota and Yamada's (1999) model with consideration of the weighted factor. The second main purpose of this paper is to apply the Bayesian approach to the optimal software release policy by assuming the prior distributions for the unknown parameters contained in the proposed software reliability growth model. Some numerical examples are presented for the purpose of comparing the optimal software release policies depending on the choice of parameters by the non-Bayesian and Bayesian methods.

In this paper, we propose an efficient rate and power allocation scheme for multiuser OFDM systems to minimize the total transmit power under the given QoS requirements. We deduce the optimal solution of transmit power minimization problem and develop a suboptimal algorithm with low complexity based on the theoretical analysis. Because of the avoidance of iterative procedure, it is less complex than the existing schemes. The simulation results show that our proposal outperforms the existing schemes and it is very close to the optimal solution.

The IEEE 802.11 distributed coordination function (DCF) provides a contention-based distribution channel access mechanism for stations to share the wireless medium. However, performance of the DCF drops dramatically in terms of throughput, delay and jitter as the number of active stations becomes large. In this paper, we propose a simple and effective scheme, called distributed coordination function with virtual group (DCF/VG), for improving the performance of the IEEE 802.11 DCF mechanism. In this scheme, each station independently decides a virtual group cycle taking into account the current contention level. The virtual group cycle consists of one or more virtual groups and a virtual group includes an idle and a busy period. Each station chooses one virtual group and operates only in the chosen group of the cycle. In other words, each station decreases its backoff counter and tries to transmit its packet during the period of the chosen virtual group like in the IEEE 802.11 DCF. Performance of the proposed scheme is investigated by numerical analysis and simulation. Our results show that the proposed scheme is very effective and has high throughput and low delay and jitter behaviors under a wide range of contention levels.

This paper proposes a new non-destructive methodology to estimate physical parameters for LSIs. In order to resolve the estimation accuracy degradation issue for low-k dielectric films, we employ a parallel-plate capacitance measurement and a wire resistance measurement in our non-destructive method. Due to (1) the response surface functions corresponding to the parallel-plate capacitance measurement and the wire resistance measurement and (2) the searching of the physical parameter values using our cost function and simulated annealing, the proposed method attains higher precision than that of the existing method. We demonstrate the effectiveness of our method by application to our 90 nm SoC process using low-k materials.

In the move toward higher clock rates and advanced process technologies, designers of the latest electronic products are finding increasing silicon failure with respect to noise. On the other hand, the minimum dimension of patterns on LSIs is much smaller than the wavelength of exposure, making it difficult for LSI manufacturers to obtain high yield. In this paper, we present a solution to reduce power-supply noise in LSI microchips. The proposed design methodology also considers design for manufacturability (DFM) at the same time as power integrity. The method was successfully applied to the design of a system-on-chip (SOC), achieving a 13.1-13.2% noise reduction in power-supply voltage and uniformity of pattern density for chemical mechanical polishing (CMP).

In this paper, a methodology based on a mix-mode interconnection architecture is proposed for constructing an application specific network on chip to minimize the total communication time. The proposed architecture uses a globally asynchronous communication network and a locally synchronous bus (or cross-bar or multistage interconnection network MIN). First, a local bus is given for a group of IP cores so that the communications within this local bus can be arranged to be exclusive in time. If the communications of some IP cores should be required to be completed within a given amount of time, then a non-blocking MIN or a crossbar switch should be made for those IP cores instead of a bus. Then, a communication ratio (CR) for each pair of local buses is provided by users, and based on the Huffman coding philosophy, a process is applied to construct a binary tree (BT) with switches on the internal nodes and buses on the leaves. Since the binary tree system is deadlock free (no cycle exists in any path), the router is just a relatively simple and cheap switch. Simulation results show that the proposed methodology and architecture of NOC is better on switching circuit cost and performance than the SPIN and the mesh architecture using our developed deadlock-free router.

This paper proposes a block-based video encoder employing variable frame skipping (VFS) to improve the video quality in low bit rate channel. The basic idea of VFS mechanism is to decide and skip a suitable, non-fixed number of frames in temporal domain to reduce bit usage. The saved bits can be allocated to enhance the spatial quality of video. In literature, several methods of frame skipping decision have been proposed, but most of them only consider the similarities between neighboring coded frames as the decision criteria. Our proposed method takes into account the reconstruction of the skipped frames using motion-compensated frame interpolation at decoder. The proposed VFS models the reconstructed objective quality of the skipped frame and, therefore, can provide a fast estimate to the frame skipping at encoder. The proposed VFS can determine the suitable frame skipping in real time and provide the encoded video with better spatial-temporal bit allocation.

Simple closed-form expressions for efficiently calculating on-chip interconnect capacitances are presented. The formulas are expressed with second-order polynomial functions which do not include exponential functions. The runtime of the proposed formulas is about 2-10 times faster than those of existing formulas. The root mean square (RMS) errors of the proposed formulas are within 1.5%, 1.3%, 3.1%, and 4.6% of the results obtained by a field solver for structures with one line above a ground plane, one line between ground planes, three lines above a ground plane, and three lines between ground planes, respectively. The proposed formulas are also superior in accuracy to existing formulas.

This paper presents a processor architecture for high-speed and reliable stereo matching based on adaptive window-size control of SAD (Sum of Absolute Differences) computation. To reduce its computational complexity, SADs are computed using images divided into non-overlapping regions, and the matching result is iteratively refined by reducing a window size. Window-parallel-and-pixel-parallel architecture is also proposed to achieve to fully exploit the potential parallelism of the algorithm. The architecture also reduces the complexity of an interconnection network between memory and functional units based on the regularity of reference pixels. The stereo matching processor is implemented on an FPGA. Its performance is 80 times higher than that of a microprocessor (Pentium4@2 GHz), and is enough to generate a 3-D depth image at the video rate of 33 MHz.

A systematic method is introduced to the computational synthesis of CMOS voltage followers (VFs). The method is divided in three steps: generation of the small-signal circuitry by selection of nullators to model the behavior of a VF, and addition of norators to form nullator-norator joined-pairs; generation of the bias circuitry by addition of ideal biases according to the properties of nullators and norators; and synthesis of the joined-pairs by MOSFETs, and of the current-biases by CMOS current mirrors. It is shown that the proposed synthesis method has the capability to generate already known and new CMOS VF topologies.

This paper discusses clock skew due to manufacturing variability and environmental change. In clock tree design, transition time constraint is an important design parameter that controls clock skew and power dissipation. In this paper, we evaluate clock skew under several variability models, and demonstrate relationship among clock skew, transition time constraint and power dissipation. Experimental results show that constraint of small transition time reduces clock skew under manufacturing and supply voltage variabilities, whereas there is an optimum constraint value for temperature gradient. Our experiments in a 0.18 µm technology indicate that clock skew is minimized when clock buffer is sized such that the ratio of output and input capacitance is four.

In this Letter, linear least squares (LLS) techniques for phase estimation of real sinusoidal signals with known or unknown amplitudes are studied. It is proved that the asymptotic performance of the LLS approach attains Cramér-Rao lower bound. For the case of a single tone, a novel LLS algorithm with unit-norm constraint is derived. Simulation results are also included for algorithm evaluation.

In pure peer-to-peer (P2P) file sharing applications and protocols using a flooding-based query algorithm, a large number of control packets (query packets) are transmitted on the network to search for target files. This clearly leads to a degradation of communication quality on the network and terminals as the number of users of the application increases. To solve such problems, this paper proposes: (1) a unified framework to describe a wide variety of query algorithms for pure P2P and (2) a new query algorithm based on this framework. Our framework determines the number of destinations for query packets based on the hop value recorded in received query packets. Simulation results revealed that the proposed query algorithm can reduce the overhead in the flooding-based query algorithm and k-random walks without decreasing the success rate of retrieval regardless of the density of target files in the network.

We propose a multiple dwell serial search (MDSS) code acquisition for optical code-division multiple-access (O-CDMA) systems and theoretically analyze its performance. The search/lock strategy (SLS) is used as verification scheme for the multiple dwell detector. The operation of SLS is modeled by finite Markov chain to analyze the performance of the proposed system. Effect of system parameters, such as number of users, threshold and mean photon count per chip, on the performance of the proposed system is investigated. The theoretical result shows that the performance of the proposed system is less sensitive to parameter settings than the conventional single dwell serial search (SDSS) code acquisition system is. In addition, the proposed MDSS code acquisition system offers shorter mean acquisition time than that of conventional SDSS system.

Coalition formation in multi-agent systems (MAS) is becoming increasingly important as it increases the ability of agents to execute tasks and maximize their payoffs. Dependence relations are regarded as the foundation of coalition formation. This paper proposes a novel dependence theory namely transitive dependence theory for dynamic coalition formation in multi-agent systems. Transitive dependence is an extension of direct dependence that supports an agent's reasoning about other social members during coalition formation. Based on the proposed transitive dependence theory, a dynamic coalition formation framework has been worked out which includes information gathering, transitive dependence based reasoning for coalition partners search and coalition resolution. The nested coalitions and how to deal with incomplete knowledge while forming coalitions are also discussed in the paper.

The partial projection filter (PTPF) for a given observation operator provides an optimal signal restoration in the presence of both the signal space and observation space noises. However, restoration error by the filter still depends on the observation operator which consists of measurement and sampling processes. In this paper, we determine a sampling operator which minimizes the restoration error by the PTPF. We see that under some assumptions about noise statistics, the restoration error by the PTPF is divided into two terms corresponding to the error arising from the signal space noise and that from the observation space noise. It has been found that although the restoration error due to the signal space noise is independent of the sampling operator, the restoration error arising from the observation space noise can arbitrarily be decreased by increasing the number of sample points in the proposed sampling operator. An illustrative example of optimal sampling in the trigonometric polynomial space is also given.

Ubiquitous computing (ubicomp) is a computing para-digm which utilizes human-centric systems and applications. With the widespread use of information appliances, robots and sensors, the ubicomp paradigm is expected to become a reality in the near future. Because close interaction between a person and the computing environment is required for ubicomp, autonomous decentralized control will play an important role. In this paper, we discuss autonomous decentralized control in ubicomp from the viewpoint of typical ubicomp applications, smart environments and context-awareness.

An efficient void filling (VF) algorithm is proposed for wavelength division multiplexing (WDM) optical packet switches (OPSes) handling variable-packet-length self-similar traffic. The computation complexity of the proposed algorithm is extremely low. We further compare the switching performance of the proposed algorithm with that of the conventional one. We demonstrate that the proposed algorithm offers significantly lower computation complexity with adequate performance.

We propose an adaptive plastic-landmine visualizing radar system employing a complex-valued self-organizing map (CSOM) dealing with a feature vector that focuses on variance of spatial- and frequency-domain inner products (V-CSOM) in combination with aperture synthesis. The dimension of the new feature vector is greatly reduced in comparison with that of our previous texture feature-vector CSOM (T-CSOM). In experiments, we first examine the effect of aperture synthesis on the complex-amplitude texture in space and frequency domains. We also compare the calculation cost and the visualization performance of V- and T-CSOMs. Then we discuss merits and drawbacks of the two types of CSOMs with/without the aperture synthesis in the adaptive plastic-landmine visualization task. The V-CSOM with aperture synthesis is found promising to realize a useful plastic-landmine detection system.

The Modified edge representation (MER) is the concept to be used in the line integral approximation for computing the surface radiation integrals of diffraction. The MER as applied to the physical optics (PO-MER), has remarkable accuracy in the surface-to-line integral reduction even for the curved surfaces and for sources very close to the scatterer. In the discussion of the mathematical foundation for this accuracy, the evaluation of the singularities in the integrand of the PO-MER line integration was left for further study.