This paper proposes a retargetable framework for rapid evaluation of processor architecture, which represents abstraction levels of architecture in a hierarchical manner. The basis for such framework is a hierarchical architecture description language, called XR2, which describes architecture at three abstraction levels: instruction set architecture, pipeline architecture and micro-architecture. In addition, a token-level computational model for fast pipeline simulation is proposed, which considers the minimal information required for the given performance measurement of the pipeline. Experimental result shows that token-level simulation is faster than the traditional cycle-accurate one by 50% to 80% in pipeline architecture evaluation.

This letter deals with coding and multiplexing strategies for DL/UL MAP transmission in IEEE 802.16m. Separate coding gives a better choice against the joint coding due to the individual users' link adaptation gain. As a multiplexing option, frequency-domain multiplexing outperforms time-domain one in the system-level performance thanks to its flexible power sharing capability between overhead channels and user traffic channels. Overall system-wide performance results are presented with the system level simulation for the various options.

In this paper, a 60 nm-thick ferroelectric film of poly(vinylidene fluoride–trifluoroethylene) on a flexible substrate of aluminum foil was fabricated and characterized. Compared to pristine silicon wafer, Al-foil has very large root-mean-square (RMS) roughness, thus presenting challenges for the fabrication of flat and uniform electronic devices on such a rough substrate. In particular, RMS roughness affects the leakage current of dielectrics, the uniformity of devices, and the switching time in ferroelectrics. To avoid these kinds of problems, a new thin film fabrication method adopting a detach-and-transfer technique has been developed. Here, 'detach' means that the ferroelectric film is detached from a flat substrate (sacrificial substrate), and 'transfer' refers to the process of the detached film being moved onto the rough substrate (main substrate). To characterize the dielectric property of the transferred film, polarization and voltage relationships were measured, and the results showed that a hysteresis loop could be obtained with low leakage current.

Infrastructure-as-a-Service (IaaS) cloud computing is emerging as a viable alternative to the acquisition and management of physical resources. The new main feature of IaaS cloud computing is the virtual machine (VM) technology which improves the flexibility of resource management. VMs use virtual machine images that are preconfigured and ready to run. Typically, VM image management uses local file copy and distribution via a network file system (NFS). This potentially means that a more efficient method can be used for VM image distribution. For efficient VM image management, we have designed and implemented a BitTorrent-based network block device (namely, BitNBD) for provisioning VM images in IaaS clouds. The BitNBD mainly provides a 'split read/write mechanism' to deal with concurrent VM instances where the same pieces of a VM are shared. With respect to the legacy BitTorrent protocol, the BitNBD enhances the piece picker policy and energy-saving mode. It is very effective in minimizing VM startup delays and providing a hibernating capability.

We investigated the truncated convolutional code with the characteristics of a block code for block-based communication systems. Three truncation methods (direct truncation, tail-terminating, and tail-biting method) were introduced by other researchers. Each of the three methods has a weakness: the direct truncation method decreases the minimum distance, the tail-terminating method uses tail bits, and the tail-biting method can only be applied by using a complicated decoder. Although the tail-biting method gives a better BER performance than the other two methods, we cannot apply the tail-biting method in all situations. Occasionally, the tail-biting convolutional code does not exist. Wang et al. presented two necessary conditions for the existence of the tail-biting convolutional code of the rate-1/2 recursive systematic convolutional code. In this paper, we analyze the encoder of the convolutional code as a linear time invariant system, and present two theorems and six corollaries on the existence of the tail-biting convolutional code. These existence conditions are adaptable to all convolutional codes. In the communication system using the truncated convolutional code, these results are applicable to determining the truncation method.

This paper presents a prediction model based on historical data to achieve optimal values of pipelining, concurrency and parallelism (PCP) in GridFTP data transfers in Cloud systems. Setting the correct values for these three parameters is crucial in achieving high throughput in end-to-end data movement. However, predicting and setting the optimal values for these parameters is a challenging task, especially in shared and non-predictive network conditions. Several factors can affect the optimal values for these parameters such as the background network traffic, available bandwidth, Round-Trip Time (RTT), TCP buffer size, and file size. Existing models either fail to provide accurate predictions or come with very high prediction overheads. The author shows that new model based on historical data can achieve high accuracy with low overhead.

In this study, a computationally efficient ranging scheme exploiting a minimum mean square error (MMSE) and a matrix-pencil (MP) technique is proposed for the IEEE 802.15.4a chirp spread spectrum (CSS) system. Based on the characteristics of the CSS signal, a practical methodology for the MMSE process is devised and the appropriate values of parameters, which are cutoff bandwidth, number of samples and sampling duration in frequency domain, are investigated and numerically determined to enhance the performance. The performance of proposed scheme is analyzed in terms of the computational complexity and the ranging estimation errors. Simulation results demonstrate that the proposed scheme performs as well as the conventional scheme at remarkably reduced computational costs.

This paper proposes the design and implementation of a real-time image compressor using 2-Dimensional Discrete Wavelet Transform (2DDWT), which targets an FPGA as its platform. The image compressor uses Daubechies' bi-orthogonal DWT filters (9, 7) and 16-bit fixed-point data formats for wavelet coefficients in the internal calculation. The target image is NTSC 640240 pixels per field whose color format is Y:Cb:Cr = 4:2:2. We developed for the 2DDWT a new structure with four Multipliers and Accumulators (MACs) for real-time operations. We designed and used a linear fixed scalar quantizer, which includes the exceptional treatment of the coefficients whose absolute values are larger than the quantization region. Only a Huffman entropy encoder was included due to the hardware overhead. The quantizer and Huffman encoder merged into a single functional module. Due to the insufficient memory space of an FPGA, we utilized external memory (SDRAM) as the working and memory storage space. The proposed image compressor maps into an APEX20KC EP20K600CB652-7 from Altera and uses 45% of the Logic Array Block (LAB) and 9% of the Embedded System Block (ESB). With a 33 MHz clock frequency, the proposed image compressor shows a speed of 67 fields per second (33 frames per second), which is more than real-time operation. The resulting image quality from reconstruction is approximately 28 dB in PSNR and its compression ratio is 29:1. Consequently, the proposed image compressor is expected to be used in a dedicated system requiring an image-processing unit.

Many object-oriented database systems have used the notion of implicit authorization to avoid the overhead caused by explicitly storing all authorizations for each object. In implicit authorization, it is very important to detect efficiently conflicts between existing authorizations and new authorizations to be added. In this article we propose a conflict detection mechanism in the OODBMSs using implicit authorization with the notion of intention type authorization. When we grant an authorization on a node n in the database granularity hierarchy, the existing method is inefficient in determining the conflicts since it needs to examine all authorizations on the descendants of the node n. In contrast, our mechanism has the advantage of detecting the conflicts at the node n where an explicit authorization is to be granted without examining any authorizations below the node n. Thus, the proposed mechanism can detect a conflict with the average time complexity of O(d), which is smaller than O(md) of existing methods, where m is the number of children nodes at an arbitrary level and d is the difference of levels between the node with an existing explicit authorization and the higher node where an explicit authorization is to be granted. We also show that the additional storage overhead of storing all authorizations is negligible when compared with the total number of all explicit authorizations.

In this letter, we study an interference scenario under a smart interferer which observes color channels and interferes with a visible light communication (VLC) network. We formulate the smart interference problem based on a Stackelberg game and propose an optimal response algorithm to overcome the interference by optimizing transmit power and sub-color channel allocation. The proposed optimization algorithm is composed with Lagrangian dual decomposition and non-linear fractional programming to have stability to get optimum points. Numerical results show that the utility by the proposed algorithm is increased over that of the algorithm based on the Nash game and the baseline schemes.

A chirp spread spectrum (CSS) system uses a chirp signal which changes the instantaneous frequency according to time for spreading a transmission bandwidth. In the CSS system, the transmission performance can be simply improved by increasing the time-bandwidth product which is known as the processing gain. However, increasing the transmission bandwidth is limited because of the spectrum regulation. In this letter, we propose a correlation-based chirp rate allocation method to improve the transmission performance by analyzing the cross-correlation coefficient in the same time-bandwidth product. In order to analyze the transmission performance of the proposed method, we analytically derive the cross-correlation coefficient according to the time-bandwidth separation product and simulate the transmission performance. The simulation results show that the proposed method can analytically allocate the optimal chirp rate and improve the transmission performance.

Many applications of wireless sensor networks (WSNs) require secure communication. The tree-based key management scheme, which is a symmetric key scheme, provides backward and forward secrecy. The sensor nodes in the communication group share a secret key for encrypting messages. When the sensor nodes are added to or evicted from the group, the group key has to be updated by sending rekeying messages. In this paper, we propose a method of key tree structure (KTS) generation by considering the addition and eviction ratio of sensor nodes to reduce the number of rekeying messages, which is influenced by the structure of the tree. For this, we define an extension of an existing tree structure such as a binary or ternary tree and generate KTS using an A* algorithm. To reduce the energy consumed by the message transmission, we also exploit genetic algorithm (GA) to build a secure communication group by considering the KTS. In the paper, we show the effectiveness of the proposed method compared with the existing structure via the simulation in terms of memory usage, the number of rekeying messages and energy consumption.

In this letter, the diversity-multiplexing tradeoff (DMT) function for a special half-duplex dynamic decode and forward (DDF) relay protocol using two source-antennas, two destination-antennas, and more than two relay-antennas is derived. It is shown that the performance of the DDF relay protocol can be substantially improved by increasing the relay-antenna number, but only for low multiplexing gains.

This paper proposes a radiation-hardened phase-locked loop (RH-PLL) with a switchable dual modular redundancy (DMR) structure. After radiation strikes, unhardened PLLs suffer clock perturbations. Conventional RH-PLLs have been proposed to reduce recovery time after perturbation. However, this recovery still requires tens of clock cycles. Our proposal involves ‘detecting’ and ‘switching’, rather than ‘recovering’ from clock perturbation. Detection speed is crucial for robust perturbation-immunity. We identify types of clock perturbation and then propose a set of detectors to detect each type. With this method, the detectors guarantee high-speed detection that leads to perturbation-immune switching from a radiated clock to an undistorted clock. The proposed RH-PLL was fabricated and then verified with a radiation test on real silicon.

Feedforward neural networks have been successfully developed and applied in many areas because of their universal approximation capability. However, there still remains the problem of determining a suitable network structure for the given task. In this paper, we propose a novel self-organizing neural network which automatically adjusts its structure according to the task. Utilizing both the constructive and the pruning procedures, the proposed algorithm finds a near-optimal network which is compact and shows good generalization performance. One of its important features is reliability, which means the randomness of neural networks is effectively reduced. The resultant networks can have suitable numbers of hidden neurons and hidden layers according to the complexity of the given task. The simulation results for the well-known function regression problems show that our method successfully organizes near-optimal networks.

We exploit a structural knowledge representation scheme called System Entity Structure (SES) methodology to represent and manage wafer failure patterns which can make a significant influence to FABs in the semiconductor industry. It is important for the engineers to simulate various system verification processes by using predefined system entities (e.g., decomposition, taxonomy, and coupling relationships of a system) contained in the SES. For better computational performance, given a certain failure pattern, a Pruned SES (PES) can be extracted by selecting the only relevant system entities from the SES. Therefore, the SES-based simulation system allows the engineers to efficiently evaluate and monitor semiconductor data by i) analyzing failures to find out the corresponding causes and ii) managing historical data related to such failures.

Image labeling is a process of recognizing each segmented region properly exploiting the properties of the regions and the spatial relationsships between regions. In some sense, image labeling is an optimization process of indexing regions using the constraints as to the scene knowledge. In this paper, we further investigate a method of efficiently labeling images using the Markov Random Field (MRF). MRF model is defined on the region adjacency graph and the labeling is then optimally determined using the simulated annealing. To endow the adaptability to the MRF-based image labeling, we have proposed a parameter estimation technique based on error backpropagation. We analyze the proposed method through experiments using the real natural scene images.

In an internet of things (IoT) system using an energy harvesting device and a secondary (2nd) battery, regardless of the age of the 2nd battery, the power management shortens the lifespan of the entire system. In this paper, we propose a scheme that extends the lifetime of the energy harvesting-based IoT system equipped with a Lithium 2nd battery. The proposed scheme includes several policies of using a supercapacitor as a primary energy storage, limiting the charging level according to the predicted harvesting energy, swinging the energy level around the minimum stress state of charge (SOC) level, and delaying the charge start time. Experiments with natural solar energy measurements based on a battery aging approximation model show that the proposed method can extend the operation lifetime of an existing IoT system from less than one and a half year to more than four years.

WBANs provide communication services in the vicinity of the human body. Since WBANs utilize both MICS frequency band for implant medical applications and ISM frequency band for medical and consumer electronics (CE) applications, MAC protocols in WBAN should be designed considering flexibility between medical and CE applications. In this letter, we identify the requirements of WBAN MAC protocols and propose a WBAN MAC protocol which satisfies the requirements. In order to provide transmission flexibility for various applications, we present the dynamic CFP allocation and opportunity period. Extensive simulation results show that the proposed protocol achieves improved throughput and latency in WBAN environment compared with IEEE 802.15.4.

In this paper we propose a mobile positioning method based on a recursive least squares (RLS) algorithm for suppressing the non-line of sight (NLOS) effects in cellular systems. The proposed method finds the position of a mobile station from TOAs measured by three BSs. Simulation results show that the proposed method has a fast convergence time and greatly reduces the positioning error especially in NLOS situations. Thus it is expected that the proposed method can be effectively used in a dense urban environment.