In the scenario of finite sample size, the performance of the generalized sidelobe canceller (GSC) is still affected by the desired signal even if all signal sources are independent with each other. Firstly, the novel expression of weight vector of the auxiliary array is derived under the circumstances of finite sample size. Utilizing this new weight vector and considering the correlative interferences, the general expression for the interference cancellation ratio (CR) is developed. Then, the impacts of the CR performance are further analyzed for the parameters including the input signal-to-noise ratio (SNR), the auxiliary array size, the correlation coefficient between the desired signal and interference as well as the snapshots of the sample data, respectively. Some guidelines can thus be given for the practical application. Numerical simulations demonstrate the agreement between the simulation results and the analytical results.

This paper proposes an iterative cancellation technique for adjacent channel interference (ACI), induced by amplifier nonlinearity in millimeter wave (mmW) communication systems. In mmW communications, a large spectrum leak is expected because of the amplifier nonlinearity, and such a spectrum leak disturbs multichannel utilization. In order to mitigate the ACI, iterative interference cancellation in the receiver side is designed in this paper. Typically, iterative interference cancellation is conducted by generating a soft replica of interference from the feedback of the decoder, and subtracting the replica from the received signals. In this case, the canceller must know the amplifier nonlinearity in order to regenerate a soft replica of ACI. In this paper, amplifier nonlinearity is estimated by subjecting the received pilot signals to polynomial regression. We reveal that using only pilot signals in estimating amplifier nonlinearity is insufficient for guaranteeing replica accuracy. To address this issue, the proposed scheme exploits the detected data sequence in the regression analysis. We demonstrate that the proposed ACI cancellation technique can effectively mitigate ACI in multichannel utilization.

A 42×42-way one-body 2-D beam-switching Butler matrix with waveguide short-slot 2-plane couplers is designed and fabricated in the 22GHz band. The one-body configuration using the commutativity and the overlapping of units allows reducing the size and loss in comparison with a cascade of matrices beam-switching for the horizontal and the vertical planes. It is achieved by replacing 2×2-way 1-plane couplers in the conventional block configuration for a Butler matrix with 22×22-way 2-plane couplers. The measured bandwidth is approximately 2% restricted by the frequency characteristics of the 2-plane couplers. In the radiation from the aperture array antenna of the 42 output ports, the 3.9dB-down coverage of 3-D solid angle by the sixteen beams is around 1.72 steradian which is same as 27.4% of hemisphere at the design frequency for the aperture spacing of 0.73×0.73 wavelength.

The analysis and design of a full 360 degrees hybrid coupler phase shifter with integrated distributed elements low pass filters is presented. Pi-section filter is incorporated into hybrid coupler phase shifter for harmonic suppression. The physical size of the proposed structure is close to that of the conventional hybrid coupler phase shifter. The maximum phase shift range is bounded by the port impedance ratio of the hybrid coupler phase shifter. Furthermore, the phase shift range is reduced if series inductance in the reflective load deviates from the optimum value. Numerical and parametric analyses are used to find the equivalent circuit of the pi-section filter for consistent relative phase shift. To validate our analysis, the proposed phase shifter operates at 8.6GHz was fabricated and measured. Over the frequency range of interest, the fabricated phase shifter suppresses second harmonic and achieves analog phase shift of 0 to 360 degrees at the passband, agreeing with the theoretical and simulation results.

As a next-generation CAN (Controller Area Network), CAN FD (CAN with flexible data rate) has attracted much attention recently. However, how to use the improved bus bandwidth efficiently in CAN FD is still an issue. Contrasting with existing methods using greedy approximate algorithms, this paper proposes a genetic algorithm for CAN FD frame packing. It tries to minimize the bandwidth utilization by considering the different periods of signals when packing them in the same frame. Moreover, it also checks the schedulability of packed frames to guarantee the real-time constraints of each frame and proposed a merging algorithm to improve the schedulability for signal set with high bus load. Experimental results validate that the proposed algorithm can achieve significantly less bandwidth utilization and improved schedulability than existing methods for a given set of signals.

Range resolution is one of the metrics of radar performance. Synthetic bandwidth radar has been proposed for high-range-resolution. The transmitted frequency and down-conversion frequency of this type of radar are shifted by fixed amounts from pulse to pulse. Received signals are synthesized by taking IFFT for high-range-resolution. However, this type of radar has a problem with second-time-around echoes since multiple pulses are utilized. Moreover, a range shift occurs due to Doppler velocity. Thus second-time-around echo suppression and Doppler velocity compensation are required for accurate target range measurement. We show in this paper a Doppler velocity measurement method with second-time-around echo suppression for synthetic bandwidth radars. Our proposed method interleaves the transmission of ascending and descending frequency sequences. The Doppler velocity is measured by using a Fourier transform of the multiplication of the signals received using both sequences. The transmitted frequency difference of the adjacent pulses is wider than the bandwidth of the matched filter, so the second-time-around echoes are down-converted to the outside band of the matched filter and suppressed. We verify the principle of the proposed method using numerical simulations and experiments. The results show that second-time-around echoes were suppressed by 7.8dB, the Doppler velocity could be obtained and the range shift due to Doppler velocity was reduced by 7.37 times compared to the conventional SBR.

Smart education environment, that is a learning environment utilizing the Information Communication Technology (ICT), has attracted a great deal of attention. In order to expand this environment, we need a system that can establish the learning environment armed cloud systems to reduce a significant strain on teaching staff. The important issue for such system is extensibility because the system should be adapted to many kinds of original digital learning material with minimum modification. Therefore, this paper proposes “An Application Framework for Smart Education System: SES Framework”. In this Smart Education System, multi-aspect information concerning to a technical term embedded in the original digital learning material can be retrieved from different social media automatically. They can be also displayed on multi-screen devices according to user's operation. It is implemented based on “Transforming Model” which enables the migration of the original digital learning material to the smart education environment. It also has an easy operation flow for trainees named “three-step selection flow”. SES Framework derived from Model-View-Controller (MVC) pattern is based on the system architecture that enables triple mashup against the original digital learning material, external social media, and screen devices in front of users. All these functionalities have been implemented on cloud systems. We show SES Framework through the implementation example. We also demonstrate the effectiveness of SES Framework by indicating the system modification case study.

Delay Tolerant Networks (DTN) protocols based on the store-and-carry principle offer useful functions such as forwarding, utility value, social networks, and network coding. Although many DTN protocol proposals have been offered, work continues to improve performance. In order to implement DTN functions, each protocol introduces multiple parameters; their performance is largely dependent on how the parameter values are set. In this paper, we focus on improving spray and wait (S&W) by proposing a communication protocol named a Spray and AHP-GRA-based Forwarding (S&AGF) and Spray and Fuzzy based Forwarding (S&FF) scheme for DTN. The proposed protocols include a new forwarding scheme intended to extend network lifetime as well as maintain acceptable delivery ratio by addressing a deficiency in existing schemes that do not take energy into consideration. We choose the most suitable relay node by taking the energy, mobility, measured parameters of nodes into account. The simulation-based comparison demonstrates that the proposed S&AGF and S&FF schemes show better balanced performance level in terms of both delivery ratio and network lifetime than original S&W and its variants.

Several kinds of techniques for excellent multi-user interference (MUI) cancellation have been proposed for direct-detection synchronous optical code division multiple access (OCDMA) systems. All these techniques utilize modified prime sequence codes (MPSCs) as signature codes and can remove MUI errors efficiently. In this paper, the features of three typical MUI cancellers are studied and compared in detail. The authors defined the parameter “decision distance” to show the feature of MUI cancellers. The bit error rate performance of each canceller is investigated by computer simulation and compared with that of the basic on-off keying (OOK) scheme without cancellation. Then, we investigate the relationship between the decision distance and the bit error rate performance. It is shown that every canceller has a better bit error rate performance than the basic OOK scheme. Especially, the equal weight orthogonal (EWO) scheme, whose decision distance is the largest, has the best error resistance property of the three MUI cancellers. The results show that the decision distance is a useful index to evaluate the error resistance property of MUI cancellation schemes.

The Euler number of a binary image is an important topological property for pattern recognition, image analysis, and computer vision. A famous method for computing the Euler number of a binary image is by counting certain patterns of bit-quads in the image, which has been improved by scanning three rows once to process two bit-quads simultaneously. This paper studies the bit-quad-based Euler number computing problem. We show that for a bit-quad-based Euler number computing algorithm, with the increase of the number of bit-quads being processed simultaneously, on the one hand, the average number of pixels to be checked for processing a bit-quad will decrease in theory, and on the other hand, the length of the codes for implementing the algorithm will increase, which will make the algorithm less efficient in practice. Experimental results on various types of images demonstrated that scanning five rows once and processing four bit-quads simultaneously is the optimal tradeoff, and that the optimal bit-quad-based Euler number computing algorithm is more efficient than other Euler number computing algorithms.

With the huge influx of various data nowadays, extracting knowledge from them has become an interesting but tedious task among data scientists, particularly when the data come in heterogeneous form and have missing information. Many data completion techniques had been introduced, especially in the advent of kernel methods — a way in which one can represent heterogeneous data sets into a single form: as kernel matrices. However, among the many data completion techniques available in the literature, studies about mutually completing several incomplete kernel matrices have not been given much attention yet. In this paper, we present a new method, called Mutual Kernel Matrix Completion (MKMC) algorithm, that tackles this problem of mutually inferring the missing entries of multiple kernel matrices by combining the notions of data fusion and kernel matrix completion, applied on biological data sets to be used for classification task. We first introduced an objective function that will be minimized by exploiting the EM algorithm, which in turn results to an estimate of the missing entries of the kernel matrices involved. The completed kernel matrices are then combined to produce a model matrix that can be used to further improve the obtained estimates. An interesting result of our study is that the E-step and the M-step are given in closed form, which makes our algorithm efficient in terms of time and memory. After completion, the (completed) kernel matrices are then used to train an SVM classifier to test how well the relationships among the entries are preserved. Our empirical results show that the proposed algorithm bested the traditional completion techniques in preserving the relationships among the data points, and in accurately recovering the missing kernel matrix entries. By far, MKMC offers a promising solution to the problem of mutual estimation of a number of relevant incomplete kernel matrices.

The widespread usage of computers and communication networks affects people's social activities effectively in terms of intercommunication and the communication generally begins with domain name resolutions which are mainly provided by DNS (Domain Name System). Meanwhile, continuous cyber threats to DNS such as cache poisoning also affects computer networks critically. DNSSEC (DNS Security Extensions) is designed to provide secure name resolution between authoritative zone servers and DNS full resolvers. However high workload of DNSSEC validation on DNS full resolvers and complex key management on authoritative zone servers hinder its wide deployment. Moreover, querying clients use the name resolution results validated on DNS full resolvers, therefore they only get errors when DNSSEC validation fails or times out. In addition, name resolution failure can occur on querying clients due to technical and operational issues of DNSSEC. In this paper, we propose a client based DNSSEC validation system with adaptive alert mechanism considering minimal querying client timeout. The proposed system notifies the user of alert messages with answers even when the DNSSEC validation on the client fails or timeout so that the user can determine how to handle the received answers. We also implemented a prototype system and evaluated the features on a local experimental network as well as in the Internet. The contribution of this article is that the proposed system not only can mitigate the workload of DNS full resolvers but also can cover querying clients with secure name resolution, and by solving the existing operation issues in DNSSEC, it also can promote DNSSEC deployment.

Recently, much progress has been made in the study of belief propagation (BP) based signal detection with large-scale factor graphs. When we apply the BP algorithm to equalization in a SISO multipath channel, the corresponding factor graph has many short loops and patterns in an edge connection/strength. Thus, proper convergence may not be achieved. In general, the log-likelihood ratio (LLR) oscillates in ill-converged cases. Therefore, LLR oscillation avoidance is important for BP-based equalization. In this paper, we propose applying node selection (NS) to prevent the LLR from oscillating. The NS extends the loop length virtually by a serial LLR update. Thus, some performance improvement is expected. Simulation results show that the error floor is significantly reduced by NS in the uncoded case and that the NS works very well in the coded case.

As the most compelling candidate for 5G, millimeter-wave communication has drawn considerable interest, despite the absence of systematic research on its performance. Therefore, this study investigates millimeter-wave cellular networks and their use of existing frequency reuse schemes and scheduling methods. To evaluate the performance of these networks, we configure a system-level simulator that reflects the eNodeB architecture and frame structure designed to overcome the millimeter-wave frequency characteristics of the Giga Korea Project. Simulations conducted using various combinations of frequency reuse schemes and scheduling methods are described. We found that the best performing radio resource management scheme changes according to the number of user equipment accessing the eNodeB. The results of this study will contribute to performance estimations of the capacity and fairness of cellular-based millimeter-wave communication systems before they are deployed.

This letter presents a test suite CF3 designed to find bugs in arithmetic optimizers of C compilers. It consists of 13,720 test programs containing all the expression patterns covering all the permutations of 3 operators from 14 operators. CF3 detected more than 70 errors in GCC 4.2-4.5 within 2 hours.

We study the problem of determining the minimum number of open-edge guards which guard the interior of a given orthogonal polygon with holes. Here, an open-edge guard is a guard which is allowed to be placed along open edges of a polygon, that is, the endpoints of the edge are not taken into account for visibility purpose. It is shown that finding the minimum number of open-edge guards for a given orthogonal polygon with holes is NP-hard.

This letter proposes a heuristic algorithm to select check variables, which are points of comparison for error detection, for soft-error tolerant datapaths. Our soft-error tolerance scheme is based on check-and-retry computation and an efficient resource management named speculative resource sharing (SRS). Starting with the smallest set of check variables, the proposed algorithm repeats to add new check variable one by one incrementally and find the minimum latency solution among the series of generated solutions. During the process, each new check variable is selected so that the opportunity of SRS is enlarged. Experimental results show that improvements in latency are achieved compared with the choice of the smallest set of check variables.

The massive multiple input multiple output (MIMO) system with large-scale antenna array at base station (BS) simultaneously communicates with many mobile stations (MSs) ensuring high reliability using the pre-coding. But, in mobile communication, the performance of the pre-coding is degraded by fast fading. For improving the performance of the pre-coding, this letter proposes the power control scheme of the new approach that has the variable step size using the statistical characteristic of fast fading and Doppler frequency. From the simulation results, it is shown that the proposed scheme improves signal-to-interference-plus-noise ratio (SINR) performance.

Sorting is an extremely important computation kernel that has been accelerated in a lot of fields such as databases, image processing, and genome analysis. Given that advent of Internet of Things (IoT) era due to mobile technology progressions, the future needs a sorting method that is available on any environment, such as not only high performance systems like servers but also low computational performance machines like embedded systems. In this paper, we present an FPGA-based sorting accelerator combining Sorting Network and Merge Sorter Tree, which is customizable by means of tuning design parameters. The proposed FPGA accelerator sorts data sent from a host PC via the PCIe bus, and sends back the fully sorted data sequence to it. We also present a detailed analytical model that accurately estimates the sorting performance. Due to these characteristics, designers can know how fast a developed sorting hardware is in advance and can implement the best one to fulfill the cost and performance constraints. Our experiments show that the proposed hardware achieves up to 19.5x sorting performance, compared with Intel Core i7-3770K operating at 3.50GHz, when sorting 256M 32-bits integer elements. However, this result is limited because of insufficient memory bandwidth. To overcome this problem, we propose a data compression mechanism and the experimental result shows that the sorting hardware with it achieves almost 90% of the estimated performance, while the hardware without it does about 60%. In order to allow every designer to easily and freely use this accelerator, the RTL source code is released as open-source hardware.

This paper proposes an effective continuous super-resolution (CSR) algorithm for the multipath channel estimation. By designing a preamble including up-chirp and down-chirp symbols, the Doppler shift and multipath delay are estimated jointly by using convex programming. Simulation results show that the proposed CSR can achieve better detection probability of the number of multipaths than the eigenvalue based methods. Moreover, compared with conventional super-resolution techniques, such as MUSIC and ESPRIT methods, the proposed CSR algorithm demonstrates its advantage in root mean square error of the Doppler shift and multipath delay, especially for the closely located paths within low SNR.