The rapid hybrid acquisition of PN sequences is proposed for DS/CDMA systems. The system introduces the excision CFAR method into the background power estimation. A mathematical analysis is done for the single path and multipath environments. The detection performance of the proposed scheme is compared with that of other acquisition schemes. Results show that the proposed method has better detection performance if the excision coefficient is properly selected.

A VCO for multi-standard transceiver should operate in wide-tuning range, while providing low-phase noise quadrature outputs with low power consumption. In this paper, a multi-standard CMOS LC QVCO is designed utilizing reconfigurable LC tank and low power low phase noise quadrature generation method. Designed in 0.18 µm CMOS technology, the VCO achieved very wide tuning characteristics in two separate bands with low power consumption.

A LC oscillator based upon the quadrature magnetic coupling to generate a mutual negative resistance (mu-R) is introduced. The topology offers enhanced optimum phase noise at low supply voltages by enabling extended circuit operation in the current-limited regime through the control of its mutual inductors' coupling factor, k. The principal operation of the mu-R oscillator is described and its comparison with the popular cross-coupled topology is discussed. The capability of the technique is demonstrated via design examples of 1.8 GHz oscillators. Simulations show that, by employing inductors with a self-inductance of 2 nH, a quality factor of about 7.5 and a coupling k=0.52, the mu-R oscillator exhibits the minimum phase noise of -142 dBc/Hz at 3 MHz-offset with 18 mA bias current and 2 V supply. This is 3-dB more than the minimum achievable phase noise in the cross-coupled oscillator with identical component parameters and supply voltage level.

We observe the inter-carrier interference (ICI) caused by channel variation of the fading in time domain in orthogonal frequency division multiplexing (OFDM) systems. This observation allows us to propose simple two-stage equalizer to minimize the ICI. Simulation results show that the bit error rate (BER) performance of the proposed equalizer with much reduced complexity is comparable with that of the classical frequency domain linear minimum mean squared error (MMSE) equalizer.

In this paper, we present a Korean to Chinese/English/Japanese multilingual Machine Translation (MT) system of closed captions for Digital Television (DTV). Preliminary experiments of our closed caption translation with existing base MT systems had shown unsatisfactory result. In order to achieve more accurate translation with the base MT systems, we adopted live resources of multilingual Named Entities and their translingual equivalences from the Web. We also utilize the program information, which the terrestrial broadcasters offer through DTV transport stream, in order to use program specific dictionaries, including the names of characters, locations and organizations. Two more components are adopted for reducing the ambiguities of parsing and word sense disambiguation; sentence simplification for long sentence segmentation and dynamic domain identification for automatic domain dictionary stacking. With these integrated approaches, we could raise the Mean Opinion Score (MOS) of translation accuracy by 0.40 higher than the base MT systems.

Feedback-type Adaptive Array Antenna has been proposed for frequency division duplexed (FDD) system, where the mobile station (MS) measures channel characteristics and sends those back to the base station (BS). Using a higher number of feed-back bits provides better performance. However it wastes channel capacity of the up-link. On the other hand, error in feedback signals transmission causes significant performance degradation. To solve these problems, this paper proposes a method that the MS sends back the difference between the optimum weights calculated at the MS and weights which are currently used at the BS. Bit error rate performance of the system is shown under a realistic propagation condition.

Vertical handoff is required to achieve anywhere and anytime internet access in the fourth generation (4G) network providing interoperability between universal mobile telecommunications system (UMTS) and wireless LAN (WLAN). However, video data can be lost due to latency caused by vertical handoff. To solve this problem, in this paper, we propose a video streaming technique supporting error concealment (EC) for video on demand (VOD) services that provides seamless playout at the client in vertical handoff. In the proposed method, the streaming server first predicts the client buffer status (CBS). Using the predicted CBS and the channel rate, the streaming server selects a proper video transmission method for vertical handoff between frame selective pre (FSP)-transmission and re-transmission. Performance evaluations are presented to demonstrate the effectiveness of the proposed method.

This paper studies the problem of the relations between existence conditions of common quadratic and those of common infinity-norm Lyapunov functions for sets of discrete-time linear time-invariant (LTI) systems. Based on the equivalence between the robust stability of a class of time-varying systems and the existence of a common infinity-norm Lyapunov function for the corresponding set of LTI systems, the relations are determined. It turns out that although the relation is an equivalent one for single stable systems, the existence condition of common infinity-norm type is strictly implied by that of common quadratic type for the set of systems. Several existence conditions of a common infinity-norm Lyapunov functions are also presented for the purpose of easy checking.

This paper proposes a multiple-input multiple-output (MIMO) eigenmode transmission technique which transmits different data streams on eigenmodes of different multi-path components while suppressing intra and inter-eigenmode interferences by means of a turbo equalization technique. This paper also evaluates the effectiveness of the proposed system in frequency selective fading conditions. Computer simulation results confirms the proposed technique is effective even in high spatial correlation cases.

Reduction of the intensity noise in semiconductor lasers is important subject to extend application range of the device. Blue-violet InGaN laser reveals high quantum noise when the laser is operated with low output power. The authors proposed a new scheme of noise reduction both for the optical feedback noise and the quantum noise by applying electric feedback which is positive type at a high frequency and negative type for lower frequency range. Noise reduction effect down to a level lower than the quantum noise was experimentally confirmed even under the optical feedback.

This paper presents a new built-in current sensor (BICS) that detects defects using the current testing technique in CMOS integrated circuits. The proposed circuit is a negligible impact on the performance of the circuit under test (CUT). In addition, no extra power dissipation and high-speed fault detection are achieved. It can be applicable in deep sub-micron process. The area overhead of the BICS versus the entire chip is about 9.2%. The chip was fabricated with Hynix 0.35 µm standard CMOS technology.

Our investigation is presented into analysis of the co-channel interference (CCI) statistic in orthogonal frequency-division multiple access (OFDMA) uplink systems. The derived statistic is then used to analyze the performance of reuse partitioning (RP)-based dynamic channel allocation (DCA). Analysis and simulation results show that the performance of DCA in multi-cell environments is noticeably dependent on the CCI. Finally, the results of the analysis yield the optimum RP area for achieving the maximum spectral efficiency.

The delay characteristics of the MPsLS, a data forwarding scheme used for a core area of the integrated data service network, are discussed and analyzed. MPsLS has the capability of guaranteeing QoS on the per-flow level for time-sensitive applications and simultaneously maintaining the high utilization of network resources. In the MPsLS core area, the forwarding process is implemented with a fine-grain slot synchronization model, and at the ingress edge nodes, the forwarding process is carried with a coarse-grain frame synchronization model. The delay analyses are done according to three service models: the exact synchronization model, the less strict synchronization model for the appointed channels, and an asynchronous model for the filler channels. The authors give estimation equations of mean delay between edge-to-edge nodes in an MPsLS network, and introduce an effective method to determine the reserved bandwidth for given application flows based on numerical calculations from those theory analysis and simple simulation results.

We report a specially designed encoding technique for sign language video sequences supposing that the technique is for sign telecommunication such as that using mobile videophones with a low bitrate. The technique is composed of three methods: gradient coding, precedence macroblock coding, and not-coded coding. These methods are based on the idea to distribute a certain number of bits for each macroblock according to the evaluation of importance of parts of the picture. They were implemented on a computer and encoded data of a short clip of sign language dialogue was evaluated by deaf subjects. As a result, the efficiency of the technique was confirmed.

Electrical capacitance tomography (ECT) is used to obtain information about the distribution of a mixture of dielectric materials inside a vessel or pipe. ECT has several advantages over other reconstruction algorithms and has found many applications in the industrial fields. However, there are some difficulties with image reconstruction in ECT: The relationship between the permittivity distribution and measured capacitance is nonlinear. And inverse problem is ill-posed so that the inverse solution is sensitive to measurement error. To cope with these difficulties iterative image reconstruction algorithms have been developed. In general, the iterative reconstruction algorithms in ECT have comparatively good-quality in reconstructed images but result in intensive computational burden. This paper presents the iterative image reconstruction algorithm for ECT that can enhance the speed of image reconstruction without degradation in the quality of reconstructed image. The main contribution of the proposed algorithm is new weighting matrices, which are obtained by the interpolation of the grouped electrical field centre lines (EFCLs). Extensive simulation results have demonstrated that proposed algorithm provides improved reconstruction performance in terms of computational time and image quality.

In this paper, we propose the construction of a web-based Question Answering (QA) system for restricted domain, which combines three resource information databases for the retrieval mechanism, including a Question&Answer database, a special domain documents database and the web resource retrieved by Google search engine. We describe a new retrieval technique of integrating a probabilistic technique based on OkapiBM25 and a semantic analysis which based on the ontology of HowNet knowledge base and a special domain HowNet created for the restricted domain. Furthermore, we provide a method of question expansion by computing word semantic similarity. The system is first developed for a middle-size domain of sightseeing information. The experiments proved the efficiency of our method for restricted domain and it is feasible to transfer to other domains expediently using the proposed method.

The number of bipolar orthogonal codes such as Walsh-Hadamard (WH) is limited due to implementation complexity which is proportional to the number of generated codes. Therefore, the data rate of multi-code systems [1] is restricted too. This paper presents a design of novel multi-level quasi-orthogonal codes (MLQOCs) using advanced orthogonal code group (AOCG) [2] derived from WH matrix to provide more spreading codes while retaining the chip-rate and length of the original WH codes. Moreover, we propose a multi-code multi-carrier CDMA (Mc-MC CDMA) system using MLQOCs to obtain high and variable transmission speed.

The superconducting quantum interference device (SQUID) is a transducer that converts magnetic flux into voltage. Its range of linear conversion, however, is very restricted. To overcome its narrow dynamic range, a flux-locked loop (FLL) is used to feedback the output field to cancel the input field. This prevents the operating point of the SQUID from moving far away from the null point. In this paper, an emulator for the SQUID sensor and the feedback coil has been proposed. Magnetic coupling between the original field and the generated field by the feedback coil was emulated by electronic circuits. By using the emulator, FLL circuits can be analyzed and optimized without use of SQUID sensors. This is a useful feature, especially in the early stage of development of the MCG system when a magnetically shielded room or real SQUID sensors may not yet be available. The emulator may also be used as a test signal generator for multi-channel gain calibration and for system maintenance.

In this letter two noise-predictive equalization schemes, which are based on zero-forcing (ZF) and minimum mean square error (MMSE) criteria, are presented for unique-word (UW) based single-carrier systems. The correlation properties of the noises in the outputs of the frequency domain equalizer are exploited to predict and cancel the noise contained in the estimation of data. Theoretical analyses show that both of the proposed techniques perform better than the conventional frequency domain equalizers. Simulation results have confirmed the significant performance improvement they could achieve.

A new Gray map between codes over F2+uF2+u2F2 and codes over F2 is defined. We prove that the Gray image of a linear (1-u2)-cyclic code over F2+uF2+u2F2 of length n is a binary distance invariant linear quasi-cyclic code. We also prove that, if n is odd, then every binary code which is the Gray image of a linear cyclic code over F2+uF2+u2F2 of length n is equivalent to a quasi-cyclic code.