Channel errors may exist in Radio Frequency IDentification (RFID) systems due to low power backscattering of tags. These errors prevent the rapid identification of tags, and reducing this deterioration is an important issue. This paper presents performance analysis of various tag anti-collision algorithms and shows that the performances of RFID systems can be improved by applying a proposed robust algorithm in error-prone environments.

In this paper, a soft-error-tolerant BILBO (Built-In Logic Block Observer) FF (flip-flop) is presented. The proposed FF works as a soft-error-tolerant FF in system operations and as a BILBO FF in manufacturing testing. The construction of the proposed FF is based on that of an existing soft-error-tolerant FF, namely a BISER (Built-In Soft Error Resilience) FF. The proposed FF contains a reconfigurable C-element with XNOR calculation capability, which works as a C-element for soft-error-tolerance during system operations and as an XNOR gate employed in linear feedback shift registers (LFSRs) during manufacturing testing. The evaluation results shown in this paper indicate that the area of the proposed FF is 8.5% smaller than that of a simple combination of the existing BISER and BILBO FFs. In addition, the sum of CLK-Q delay and D-CLK setup times on system operations for the proposed FF is 19.7% shorter than that for the combination.

In this letter, we derive a probability density function (PDF) for a modulus of product of two complex-valued Gaussian random variables. The PDF is expressed using Modified Bessel Functions, and the probability distribution is named Gaussian Product Modulus Distribution. Some examples of expectation calculation are provided.

In this paper, two constructions of mutually orthogonal zero correlation zone polyphase sequence sets are presented. The first one is based on DFT matrices and interleaving iteration. After each recursive step, the period of sequence and the length of zero-correlation zone are two times larger than that in the last step. The second method, based on DFT matrices and orthogonal matrices, can generate numbers of mutually orthogonal optimal ZCZ sequence sets whose parameters reach the theoretical bounds by using interleaving and shifting techniques. As a result, the algorithms proposed can provide more sequences for the QS-CDMA (quasi-synchronous CDMA) systems.

In multi-hop wireless networks, the transmitted signal is generally forwarded over several relay terminals. So, the quality of communications is degraded due to these re-transmissions over fading channels in relay terminals. Basically, the conventional cooperative relaying scheme based on cyclic delay diversity (CDD) reduces this degradation because this scheme could have numerous relay terminals which simultaneously transmit the signals. However, we cannot obtain the maximum diversity gain because of the re-transmission without considering relay channel environments. In this letter, to overcome the decreased performance, we propose an adaptive decode-and-forward (DF) relaying scheme based on CDD which uses cyclic redundancy check (CRC) code. Simulation results show that the proposed scheme provides more improvement in error performance than the conventional schemes in multi-hop networks.

The long-standing problem of predicting circuit performance variations without a huge number of statistical investigations is demonstrated to be solvable by a surface-potential-based MOSFET model. Direct connection of model parameters to physical device parameters reflecting process variations and the reduced number of model parameters are the enabling key model properties. It has been proven that the surface-potential-based model HiSIM2 is capable of reproducing measured I-V and its derivatives' variations with those of device/process related model parameters. When used to predict 51-stage ring oscillator frequency variation including both inter- and intra-chip variation, it reproduces measurements with shortened simulation time.

The increasing demand of low power Direct Digital Frequency Synthesizer (DDFS) leads to the requirement of efficient compression methods to reduce ROM size for storing sine function values. This paper presents a technique to achieve very high compression ratio by using the optimized four-segment linear difference method. The proposed technique results in the ROM compression ratio of about 117.3:1 and the word size reduction of 6 bits for the design of a DDFS with 11-bit sine amplitude output. This high compression ratio result is very promising to meet the requirement of low power consumption and low hardware complexity in digital VLSI technology.

Due to the difficulty of test pattern generation for sequential circuits, several design-for-testability (DFT) approaches have been proposed. An improvement to these current approaches is needed to cater to the requirements of today's more complicated chips. This paper introduces a new DFT method applicable to high-level description of circuits, which optimally utilizes existing functional elements and paths for test. This technique, called F-scan, effectively reduces the hardware overhead due to test without compromising fault coverage. Test application time is also kept at the minimum. The comparison of F-scan with the performance of gate-level full scan design is shown through the experimental results.

In the localized Discrete Fourier Transform-Spread-Orthogonal Frequency Division Multiplexing (DFT-S-OFDM) uplink cooperative system, multiple carrier frequency offsets (MCFO), arising from the nodes' separate oscillators and Doppler spreads, drastically degrade the performance of the receiver. To solve the problem, this letter proposes an efficient MCFO compensation method which fully exploits the diversity gain of space frequency block coded (SFBC) and the characteristic of inter-carrier interference (ICI). Moreover, the bit error ratio (BER) lower bound of the proposed algorithm is theoretically derived. Simulation results validate the theoretical analysis and demonstrate that the proposed MCFO compensation method can achieve robust BER performance in a wide range of MCFO in the multipath Rayleigh fading channel.

In this paper, the performance of the soft-decision-and-forward (SDF) protocol in the cooperative communication network with one source, one relay, and one destination, where each node has two transmit and receive antennas, is analyzed in terms of the bit error rate (BER) obtained from the pairwise error probability (PEP). Using the moment generating function and Q-function approximation, the PEP of SDF protocol is calculated and we confirm that the SDF with two antennas achieves the full diversity order. For the slow-varying Rayleigh fading channel, the optimal power allocation ratio can be determined so as to minimize the average PEP (or BER). Due to the difficulty of deriving the optimal value analytically, an alternative strategy of maximizing the product signal-to-noise ratio (SNR) of direct and relay links, which we call the suboptimal power allocation, is considered. Through a numerical analysis, we show that the performance gap between the suboptimal and optimal power allocation strategies is negligible in the high SNR region.

In wireless OFDM systems, the system performance is suffered from frequency offset and symbol timing offset due to the Doppler effect. Using the discrete Fourier transform (DFT) and inverse discrete Fourier transform (IDFT) for traditional signal transformation from the time-domain into frequency-domain, and vice versa, the system performance may be severely degraded. To make the OFDM system that can tolerate the above problems, we have considered that the harmonic transform can be applicable to the traditional signal transformation, thereby improving the system performance. In this paper, we combine the good characteristics of harmonic transform and instantaneous frequency to be a novel transformation for wireless OFDM systems. We propose a modified discrete harmonic transform (MDHT) which can be performed adaptively. Our proposed scheme called the modified discrete harmonic transform OFDM (MDHT-OFDM scheme). We derive the equations of the novel discrete harmonic transform which are suitable for wireless OFDM systems and the novel channel estimation cooperated with the novel transformation. The proposed channel estimation is performed in both time-domain and frequency-domain. The performance of a MDHT-OFDM scheme is evaluated by means of a simulation. We compare the performance of a MDHT-OFDM scheme with one of the conventional DFT-OFDM scheme in the term of symbol error rate (SER). MDHT-OFDM scheme can achieve better performance than that of the conventional DFT-OFDM scheme in mitigating the Doppler spread.

The increase in the time required for data processing, mask drawing, and inspection of photomask, has led to substantial increase in mask manufacturing cost. This has become one of the major challenges in the semiconductor industry. We have developed a data flow process for mask manufacturing in which we refer to design intent information in order to reduce TAT of mask manufacturing processes. We convert design level information "Design Intent (DI)" into priority information of mask manufacturing data known as "Mask Data Rank (MDR)" so that we can identify and sort out the importance of mask patterns from the view point of the design side. As a result, we can reduce mask writing time and mask inspection time. Our objective is to build efficient data flow conversion system from DI to MDR. In this paper we introduce the idea of MDR and the software system that we built for DI extraction. Then we show the experimental results with actual chip data. Lastly we will discuss related issues and their solutions.

Multi-pattern matching is a key technique for implementing network security applications such as Network Intrusion Detection/Protection Systems (NIDS/NIPSes) where every packet is inspected against tens of thousands of predefined attack signatures written in regular expressions (regexes). To this end, Deterministic Finite Automaton (DFA) is widely used for multi-regex matching, but existing DFA-based researches have claimed high throughput at an expense of extremely high memory cost, so fail to be employed in devices such as high-speed routers and embedded systems where the available memory is quite limited. In this paper, we propose a parallel architecture of DFA called Parallel DFA (PDFA) taking advantage of the large amount of concurrent flows to increase the throughput with nearly no extra memory cost. The basic idea is to selectively store the underlying DFA in memory modules that can be accessed in parallel. To explore its potential parallelism we intensively study DFA-split schemes from both state and transition points in this paper. The performance of our approach in both the average cases and the worst cases is analyzed, optimized and evaluated by numerical results. The evaluation shows that we obtain an average speedup of 100 times compared with traditional DFA-based matching approach.

In an embedded control system, control performances of each job depend on its latency and a control algorithm implemented in it. In order to adapt a job set to optimize control performances subject to schedulability, we design several types of control software for each job, which will be called versions, and select one version from them when the job is released. A real-time system where each job has several versions is called a multiversion real-time system. A benefit and a CPU utilization of a job depend on the versions. So, it is an important problem to select a version of each job so as to maximize the total benefit of the system subject to a schedulability condition. Such a problem will be called an optimal configuration problem. In this paper, we assume that each version is specified by the relative deadline, the execution time, and the benefit. We show that the optimal configuration problem is transformed to a maximum path length problem. We propose an optimal algorithm based on the forward dynamic programming. Moreover, we propose sub-optimal algorithms to reduce computation times. The efficiencies of the proposed algorithms are illustrated by simulations.

Recently, broadcast services are introduced in cellular networks and macro diversity is an effective way to combat fading. In this paper, we propose a kind of distributed space-time block codes (STBCs) for macro diversity which is constructed from the total antennas of multiple cooperating base stations, and all the antennas form an equivalent multiple input multiple output (MIMO) system. This code is termed High-Dimension-Full-Rate-Quasi-Orthogonal STBC (HDFR-QOSTBC) which can be characterized as: (1) It can be applied with any number of transmit antennas especially when the number of transmit antennas is large; (2) The code is with full transmit rate of one; (3) The Maximum Likelihood (ML) decoding complexity of this code is controllable and limited to Nt/2-symbol-decodable for total Nt transmit antennas. Then, we completely analyze the structure of the equivalent channel for the kind of codes and reveal a property that the eigenvectors of the equivalent channel are constant and independent from the channel realization, and this characteristic can be exploited for a new transmission structure with single-symbol linear decoder. Furthermore, we analyze different macro diversity schemes and give a performance comparison. The simulation results show that the proposed scheme is practical for the broadcast systems with significant performance improvement comparing with soft-combination and cyclic delay diversity (CDD) methods.

This paper describes the design methodology of a low dropout regulator (LDO). It was used to develop a power management sub-system IC for CDMA handsets which is also described in this paper. This IC contains 11 LDOs, bandgap reference, battery charger, control logic and some other peripheral circuits. For CDMA applications, very small ground current in the order of µA in standby mode is required for LDOs. An LDO architecture to meet this requirement and achieve stable operation over the process variation was developed. The on-chip logic efficiently controls all LDOs and battery charger to reduce the power dissipation as much as possible. This mixed signal subsystem has been implemented in the in-house 0.6-µm BCDMOS process. The very low LDO ground current down to 3 µA has been achieved with stable operation.

A band diagram is fundamental for investigating the electromagnetic properties of periodic structures such as photonic and/or electromagnetic crystals and electromagnetic bandgap structures. In this paper, computer resources and the accuracy of the Finite Difference Frequency Domain and the Finite Difference Time Domain methods are studied. The periodic structure treated here consists of two-dimensional dielectric cylinders.

Switch and stay combining (SSC) is an attractive diversity technique due to its low complexity and compatibility to resource-constrained wireless networks. This letter proposes a distributed SSC for partial relay selection networks in order to achieve spatial diversity as well as to improve spectral efficiency. Simulation results show that the performance loss (in terms of bit error probability) of the proposed networks relative to partial relay selection networks with selection combining is not substantial.

A linear model for feedforward ring oscillators (FROs) is developed and oscillator characteristics are analyzed using the model. The model allows prediction of multiple oscillation modes as well as the oscillation frequency of each mode. The prediction agrees well with SPICE simulation results.

This paper demonstrates an efficient modelling method for artificial materials using digital filtering (DF) techniques. To demonstrate the efficiency of the DF technique it is applied to an electromagnetic bandgap (EBG) structure and a capacitively-loaded loop the so-called, CLL-based metamaterial. Firstly, this paper describes fine mesh simulations, in which a very small cell size (0.10.10.1 mm3) is used to model the details of an element of the structures to calculate the scattering parameters. Secondly, the scattering parameters are approximated with Padé forms and then factorised. Finally the factorised Padé forms are converted from the frequency domain to the time domain. As a result, the initial features in the fine meshes are effectively embedded into a numerical simulation with the DF boundary, in which the use of a coarse mesh is feasible (1,000 times larger in the EBG structure simulation and 680 times larger in the metamaterial simulation in terms of the volumes). By employing the coarse mesh and removal of the dielectric material calculations, the heavy computational burden required for the fine mesh simulations is mitigated and a fast, efficient and accurate modelling method for the artificial materials is achieved. In the case of the EBG structure the calculation time is reduced from 3 hours to less than 1 minute. In addition, this paper describes an antenna simulation as a specific application example of the DF techniques in electromagnetic compatibility field. In this simulation, an electric field radiated from a dipole antenna is enhanced by the DF boundary which models an artificial magnetic conductor derived from the CLL-based metamaterial. As is shown in the antenna simulation, the DF techniques model efficiently and accurately large-scale configurations.