We propose a cooperative compressed spectrum sensing scheme for correlated signals in wideband cognitive radio networks. In order to design a reconstruction algorithm which accurately recover the wideband signals from the compressed samples in low SNR (Signal-to-Noise Ratio) environments, we consider the multiple measurement vector model exploiting a sequence of input signals and propose a cooperative sparse Bayesian learning algorithm which models the temporal correlation of the input signals. Simulation results show that the proposed scheme outperforms existing compressed sensing algorithms for low SNRs.

One of the most important problems in web services application is the integration of different existing services into a new composite service. Existing work has the following disadvantages: (i) developers are often required to provide a composite service model first and perform formal verifications to check whether the model is correct. This makes the synthesis process of composite services semi-automatic, complex and inefficient; (ii) there is no assurance that composite services synthesized by using the fully-automatic approaches are correct; (iii) some approaches only handle simple composition problems where existing services are atomic. To address these problems, we propose a correct assurance approach for automatically synthesizing composite services based on finite state machine model. The syntax and semantics of the requirement model specifying composition requirements is also proposed. Given a set of abstract BPEL descriptions of existing services, and a composition requirement, our approach automatically generate the BPEL implementation of the composite service. Compared with existing approaches, the composite service generated by utilizing our proposed approach is guaranteed to be correct and does not require any formal verification. The correctness of our approach is proved. Moreover, the case analysis indicates that our approach is feasible and effective.

Extremely low voltage operation near or below threshold voltage is a key circuit technology to improve the energy efficiency of information systems and to realize ultra-low power sensor nodes. However, it is difficult to operate conventional analog circuits based on amplifier at low voltage. Furthermore, PVT (Process, Voltage and Temperature) variation and random Vth variation degrade the minimum operation voltage and the energy efficiency in both digital and analog circuits. In this paper, extremely low power analog circuits based on comparator and switched capacitor as well as extremely low power digital circuits are presented. Many kinds of circuit technologies are applied to cope with the variation problem. Finally, image processing SoC that integrates digital and analog circuits is presented, where improvement of total performance by a cooperation of analog circuits and digital circuits is demonstrated.

Four calculation techniques for the Q-factor determination of resonant structures are compared on the basis of the influence of the VNA measurement uncertainty. The influence is evaluated using Monte Carlo calculations. On the basis of the deviation, the dispersion, and the effect of nearby resonances, the circle fitting method is the most appropriate technique. Although the 3dB method is the most popular technique, the Q-factors calculated by this method exhibit deviations, and the sign and amount of the deviation depend on the measurement setup. Comparisons using measurement data demonstrate that the uncertainty of the dielectric loss tangent calculated by the circle fitting method is less than a third of those calculated by the other three techniques.

The success of any project can be affected by requirements changes. Requirements elicitation is a series of activities of adding, deleting, and modifying requirements. We refer to the completion of requirements elicitation of a software component as requirements maturation. When the requirements of each component have reached the 100% maturation point, no requirement will come to the component. This does not mean that a requirements analyst (RA) will reject the addition of requirements, but simply, that the additional requirements will not come to the project. Our motivation is to provide measurements by which an RA can estimate one of the maturation periods: the early, middle, or late period of the project. We will proceed by introducing the requirements maturation efficiency (RME). The RME of the requirements represents how quickly the requirements of a component reach 100% maturation. Then, we will estimate the requirements maturation period for every component by applying the RME. We assume that the RME is derived from its accessibility from an RA to the requirements source and the stability of the requirements. We model accessibility as the number of information flows from the source of the requirements to the RA, and further, model stability with the requirements maturation index (RMI). According to the multiple regression analysis of a case, we are able to get an equation on RME derived from these two factors with a significant level of 5%. We evaluated the result by comparing it to another case, and then discuss the effectiveness of the measurements.

There have been many researches about construction and application of ontology in reality, notably the usage of ontology to support requirements engineering. The effect of ontology-based requirements engineering depends on quality of ontology. With the increasing size of ontology, it is difficult to verify the correctness of information stored in ontology. This paper will propose a method of using rules for verification the correctness of requirements ontology. We provide a rule description language to specify properties that requirements ontology should satisfy. Then, by checking whether the rules are consistent with requirements ontology, we verify the correctness of the ontology. We have developed a verification tool to support the method and evaluated the tool through experiments.

This paper introduces an ontology-based method for checking requirements specification. Requirements ontology is a knowledge structure that contains functional requirements (FR), attributes of FR and relations among FR. Requirements specification is compared with functional nodes in the requirements ontology, then rules are used to find errors in requirements. On the basis of the results, requirements team can ask questions to customers and correctly and efficiently revise requirements. To support this method, an ontology-based checking tool for verification of requirements has been developed. Finally, the requirements checking method is evaluated through an experiment.

Available bandwidth, along with latency and packet loss rate, is an essential metric for the efficient operation of overlay network applications. However, the measurement of available bandwidth creates a larger traffic overhead than other metrics. Measurement conflicts on route-overlapping paths can also seriously degrade measurement accuracy and cause a non-negligible increase in the network load. In this paper, we propose a distributed method for measuring the available bandwidth in overlay networks that can reduce measurement conflicts while maintaining high measurement accuracy at low cost. Our main idea is that neighboring overlay nodes exchange route information to detect overlapping paths and share the measurement results of overlapping paths to configure parameter settings for available bandwidth measurements. Our simulation results show that the relative errors in the measurement results of our method are approximately only 65% of those of the existing method. The measurement accuracy of our method remains better than that of the existing method when the total measurement traffic loads of both methods are equal.

The Internet real-time applications are growing rapidly, and available bandwidth estimation is required. Available bandwidth estimation methods by end host have been studied e.g. Pathload and pathChirp. These methods parameterize probe packet volume and observe the delay variation to estimate available bandwidth. In these methods, the probe packets impose heavy overhead loads on the network. In this paper, we propose a new available bandwidth estimation method based on the frequency of minimum RTT of probe packets in multi hop links. This method estimates bandwidth utilization and available bandwidth of a bottleneck link without significantly increasing network overhead. Estimation accuracies are evaluated for available bandwidth by implementing the proposed method. The proposed method shows better performance than pathChirp or Pathload, requiring fewer probe packets and less estimation time simultaneously.

With the ever-growing prevalence of web 2.0, users can access information and resources easily and ubiquitously. It becomes increasingly important to understand the characteristics of user's complex behavior for efficient network management and security monitoring. In this paper, we develop a novel method to visualize and measure user's web-communication-behavior character in large-scale networks. First, we employ the active and passive monitoring methods to collect more than 20,000 IP addresses providing web services, which are divided into 12 types according to the content they provide, e.g. News, music, movie and etc, and then the IP address library is established with elements as (servicetype, IPaddress). User's behaviors are complex as they stay in multiple service types during any specific time period, we propose the behavior spectrum to model this kind of behavior characteristics in an easily understandable way. Secondly, two kinds of user's behavior characters are analyzed: the character at particular time instants and the dynamic changing characters among continuous time points. We then employ Renyi cross entropy to classify the users into different groups with the expectation that users in the same groups have similar behavior profiles. Finally, we demonstrated the application of behavior spectrum in profiling network traffic patterns and finding illegal users. The efficiency and correctness of the proposed methods are verified by the experimental results using the actual traffic traces collected from the Northwest Regional Center of China Education and Research Network (CERNET).

An efficient beamforming algorithm for large-scale phased arrays with lossy digital phase shifters is presented. This problem, which arises in microwave power transmission from solar power satellites, is to maximize the array gain in a desired direction with the gain loss of the phase shifters taken into account. In this paper the problem is first formulated as a discrete optimization problem, which is then decomposed into element-wise subproblems by the real rotation theorem. Based on this approach, a polynomial-time algorithm to solve the problem numerically is constructed and its effectiveness is verified by numerical simulations.

Presented is a new measuring and reconstruction framework of Compressed Sensing (CS), aiming at reducing the measurements required to ensure faithful reconstruction. A sparse vector is segmented into sparser vectors. These new ones are then randomly sensed. For recovery, we reconstruct these vectors individually and assemble them to obtain the original signal. We show that the proposed scheme, referred to as SegOMP, yields higher probability of exact recovery in theory. It is finished with much smaller number of measurements to achieve a same reconstruction quality when compared to the canonical greedy algorithms. Extensive experiments verify the validity of the SegOMP and demonstrate its potentials.

In recent VLSIs, small-delay defects, which are hard to detect by traditional delay fault testing, can bring about serious issues such as short lifetime. To detect small-delay defects, on-chip delay measurement which measures the delay time of paths in the circuit under test (CUT) was proposed. However, this approach incurs high test cost because it uses scan design, which brings about long test application time due to scan shift operation. Our solution is a test application time reduction method for testing using the on-chip path delay measurement. The testing with on-chip path delay measurement does not require capture operations, unlike the conventional delay testing. Specifically, FFs keep the transition pattern of the test pattern pair sensitizing a path under measurement (PUM) (denoted as p) even after the measurement of p. The proposed method uses this characteristic. The proposed method reduces scan shift time and test data volume using test pattern merging. Evaluation results on ISCAS89 benchmark circuits indicate that the proposed method reduces the test application time by 6.89∼62.67% and test data volume by 46.39∼74.86%.

In this paper, we propose a bitstream-level noise cancellation method for playback applications of damaged video. Most analog video data such as movies, news and historical research videos are now stored in a digital format after a series of conversion processes that include analog-to-digital conversion and compression. In many cases, noise such as blotches and line scratching remaining in analog media are not removed during the conversion process. On the other hand, noise is propagated in the compression stage because most media compression technologies use predictive coding. Therefore, it is imperative to efficiently remove or reduce the artifacts caused by noise as much as possible. In some cases, the video data with historical values are to be preserved without correcting the noise in order not to lose any important information resulting from the noise removal process. However, playback applications of such video data still need to undergo a noise reduction process to ensure picture quality for public viewing. The proposed algorithm identifies the candidate noise blocks at the bitstream-level to directly provide a noise reduction process while decoding the bitstream. Throughout the experimental results, we confirm the efficiency of the proposed method by showing RR and PR values of around 70 percent.

This paper presents an experimental evaluation of an ocean wave remote sensing system that uses bistatic GPS signal reflection to estimate wave characteristics. In our previous paper, a bistatic ocean wave remote sensing system by GPS was proposed to estimate the characteristics of sea swell near a harbor, and was also evaluated by numerical simulations. In the next phase, a prototype system has been developed and some basic experiments have been carried out in a coastal area in order to evaluate the system experimentally. In this paper, we will outline the prototype system. The system mainly consists of an array antenna, a front-end, and an estimator for ocean wave characteristics. Next, we explain that the estimator for ocean wave characteristics can identify each signal reflected from the ocean waves. Finally, the experiments show that the prototype system can receive the reflected signals from the sea-surface near the coast, and estimate the wave period and wavelength in the direction of the array antenna.

Cognitive Radio (CR) is aimed at increasing the efficiency of spectrum utilization by allowing unlicensed users to access, in an opportunistic and non-interfering manner, some licensed bands temporarily and/or spatially unoccupied by the licensed users. The analysis of CR systems usually requires the spectral activity of the licensed system to be represented and characterized in a simple and tractable, yet accurate manner, which is accomplished by means of spectrum models. In order to guarantee the realism and accuracy of such models, the use of empirical spectrum occupancy data is essential. In this context, this paper explains the complete process of spectrum modeling, from the realization of field measurements to the obtainment of the final validated model, and highlights the main relevant aspects to be taken into account when developing spectrum usage models for their application in the context of the CR technology.

We present the concept of an on-line electric vehicle (OLEV) and its wireless power transfer mechanism and analyze the electromagnetic compatibility characteristics. As magnetic fields transfer 100kW of power to the vehicle, reduction of electromagnetic field (EMF) noise is a critical issue for protection of the human body. Also, with respect to electromagnetic interference (EMI) noise, a proper measurement method has not yet been established for this low frequency high power system. In this paper, low frequency magnetic field shielding methods and application of the shields to the OLEV system are presented. Furthermore, a standard low frequency magnetic field measurement is suggested as an EMI test.

Some key challenges remain to be overcome before spectrum sensing can be widely used to identify spectrum opportunities in the TV bands. To fulfill the strict sensing requirement specified by FCC, a comprehensive sensing algorithm, which produces high SNR gain and maintains sensing robustness under complex noise conditions, needs to be implemented. In addition, carefully designed physical features and improvement on cost performance ratio are also essential if a prototype is to be commercialized. To the best of our knowledge, no success has ever been announced in developing a sensing prototype that fulfills both FCC sensing requirement and the above mentioned features. In this paper, we introduce a recently developed sensing prototype for Japanese digital TV signals of ISDB-T. The prototype operates in the Japanese UHF TV band of 470-770MHz and can reliably identify presence/absence of an ISDB-T signal at the level of -114dBm in a 6MHz channel. Moreover, it has constrained size and weight, and is capable of accurately measuring power of an ISDB-T signal at an extremely low level. Efforts on reducing cost have also been made by avoiding the use of electronic components/devices of high price. Both laboratory and field tests are performed to evaluate its sensing performance and power measurement capability. In the laboratory test, sensing performance under conditions of adjacent channel interference and frequency offset, and power measurement accuracy, are checked. In field tests, the prototype is attached in a vehicle and is checked for its capability to identify the presence of purposely broadcasted ISDB-T signals at some fixed locations and also during movement of the vehicle.

Prediction of cross-talk is an important facet of multicore fiber (MCF) design. Several approaches for estimating cross-talk in MCF have been proposed but none are faultless, especially when applied to MCF with heterogeneous cores. We propose a new calculation approach that attempts to solve this problem. In our approach, cross-talk in multicore fibers is estimated by coupled power theory. The coefficients in the coupled power equation are theoretically calculated by the central limit theorem and by quantum mechanical time-dependent perturbations. The results from our calculations agree with those of Monte Carlo simulations of heterogeneous MCFs.

In this paper, the measurement of capacitance variation, of an on-chip power distribution network (PDN) due to the change of internal states of a CMOS logic circuit, is studied. A state-dependent PDN-capacitance model that explains measurement results will be also proposed. The model is composed of capacitance elements related to MOS transistors, signal and power supply wires, and substrate. Reflecting the changes of electrode potentials, the capacitance elements become state-dependent. The capacitive elements are then all connected in parallel between power supply and ground to form the proposed model. By using the proposed model, state-dependence of PDN-capacitances for different logic circuits are studied in detail. The change of PDN-capacitance exceeds 12% of its total capacitance in some cases, which corresponds to 6% shift of anti-resonance frequency. Consideration of the state-dependence is important for modeling the PDN-capacitance.