In this paper, the performance of narrow band interference (NBI) rejection scheme for direct sequence spread spectrum (DS/SS) is analyzed. A single-tapped complex FIR filter is used for filtering a chip code to suppress NBI. In this system, the spectrum of transmitted signal has a null at an arbitrary frequency. By choosing filter coefficients, we place this null at NBI center frequency to mitigate the effect of NBI. The performance of this scheme is theoretically analyzed and validated by simulation. We also compare the effectiveness against BPSK interference between the chip code filtering and received signal filtering. The results indicate the chip code filtering is effective against single-tone and BPSK interference, and gains better performance than the received signal filtering at certain level of SNR.

This paper presents an overview of research, development, standardization and regulation activities on ultra wideband (UWB) technologies in National Institute of Information and Communications Technology (NICT). NICT started a project on UWB technologies since 2002, and organized UWB consortium in cooperation with more than 20 companies and 7 universities in Japan. Up to now, we have been conducting numerous UWB R&D including the following main works: i) key technology development such as MMIC chips, antennas and other devices, ii) measurement and channel modeling for UWB signal propagation, iii) standardization in international activities of IEEE 802.15, ITU-R TG1/8 as well as in a national regulatory committee of Ministry of Internal Affair and Communications (MIC). The UWB systems we have studied occupy frequency bands range from microwave band (3-5 GHz) to quasi-millimeter wave band (24-29 GHz). Various prototype UWB systems including multi-functional terminals have been developed. The output of NICT has been succeeded by industrial parties with with national and international standardization and regulation.

This letter proposes a novel geographic channel assignment (GCA) framework for dynamic channel allocation (DCA) in broadband wireless access networks (BWANs). The proposed GCA scheme is based on the characteristics of radio propagation, which focuses on the relationship between transmission distances and communication parameters, e.g., signal-to-noise ratio (SNR) etc., and uses a signal-aware distance estimation scheme to determinate an appropriate channel for communication. This method significantly increases the capacity of the BWA system. Simulation results show that the GCA framework can yield approximate two times throughput of the IEEE 802.16 standard specifications as well as obtain significantly lower call blocking probability compared with classical channel assignment methods.

It is well known that the diversity gain attained by DCA (Dynamic Channel Allocation) is generally very high over OFDM (Orthogonal Frequency Division Multiplexing)-based broadband networks. This paper introduces a numerical approach for measuring the performance gain afforded by DCA. In the mathematical analysis, the property of order statistics is adopted to derive the upper bound of the expected throughput via the use of DCA. In the simulation, it was possible to achieve a gain of 5 dB by exploiting multi-user and spectral diversities when the number of users is 16 and the total number of subcarriers is 256.

We propose a hybrid voice conversion method which employs a combination of techniques using HMM-based unit selection and spectrum generation. In the proposed method, the HMM-based unit selection selects the most likely unit for the required phoneme context from the target speaker's corpus when candidates of the target unit exist in the corpus. Unit selection is performed based on the sequence of the spectral probability distribution obtained from the adapted HMMs. On the other hand, when a target unit does not exist in a corpus, a target waveform is generated from the adapted HMM sequence by maximizing the spectral likelihood. The proposed method also employs the HMM in which the spectral probability distribution is adjusted to the target prosody using the weight defined by the prosodic probability of each distribution. To show the effectiveness of the proposed method, sound quality and speaker individuality tests were conducted. The results revealed that the proposed method could produce high-quality speech and individuality of the synthesized sound was more similar to the target speaker compared to conventional methods.

We have developed a spread-spectrum Phase-Locked Loop (PLL) for serial Advanced Technology Attachment (ATA) applications. We investigated the relation between the output jitter of PLLs in serial ATA applications and ΣΔ modulators in PLLs. On the basis of this study, we developed a spread-spectrum PLL for serial ATA applications and achieved a combination of small jitter and large electromagnetic interference (EMI) peak power reduction. This was achieved using two key components: multi-bit ΣΔ-controlled PLL and voltage-controlled oscillation with cross-coupled load delay cells. Using a 0.15-µm complementary metal-oxide semiconductor process, we fabricated a complete serial ATA transceiver featuring a spread-spectrum clock generator (SSCG). We achieved a spread-spectrum PLL with 10-dB EMI reduction and 8.1 ps random jitter for use in serial ATA applications. All other measured results for SSCG performance were very good and showed that the spread-spectrum generator more than satisfies serial ATA specifications.

In this paper, we propose a new projector-based display which can perform the color simulator for print industry. The proposed color simulator can change the color of print by projecting the image onto the print. A color of print can be matched to the desired color by projecting the image which is calculated to minimize the color difference between the colors of target print and current print. This current print is measured by digital camera or digital scanner. Ideally, spectral camera or scanner is expected to be used for accurate color simulation on the current print, but it costs a lot for practical application. Therefore, in this paper, we compared two methods for color matching, one is the tristimulus-based method with XYZ tristimulus values and the other is the spectral-based method with spectral values. As the result of computer simulation, the average color difference ΔE *94 was 0.27 by the spectral-based method between the reflected radiance from the color of target print and the color of current print with projector, and the average color difference ΔE *94 was 2.09 by the tristimulus-based method. The efficiency of the proposed system is verified by the subjective evaluation between the target and current print with appropriate image projection.

In current IP-based networks, the application of window-based end-to-end flow control, including TCP, to ensure reliable flows is an essential factor. However, since such a flow control is provided by the end hosts, end-to-end control cannot be applied to decision-making in a time-scale shorter than the round-trip delay. We have previously proposed a diffusion-type flow control mechanism to realize the extremely time sensitive flow control that is required for high-speed networks. In this mechanism, each network node manages its own traffic only on the basis of the local information directly available to it, by using predetermined rules. The implementation of decision-making at each node can lead to optimal performance for the whole network. Our previous studies showed that the mechanism works well, by itself, in high-speed networks. However, to apply this mechanism to actual networks, it needs to be able to coexist with other existing protocols. In this paper, we investigate the performance of diffusion-type flow control coexisting with TCP. We show that diffusion-type flow control can coexist with TCP and the two can be complementary. Then, we show that a combination of both controls achieves higher network performance than TCP alone in high-speed networks.

Frequency-modulated clock signals are widely used in personal computers to reduce the amplitude of the clock harmonic noise, as measured using an electromagnetic interference (EMI) test receiver. However, the power of the clock harmonics is not decreased with this technique called spread spectrum clocking (SSC). Hence, the impact of the harmonics of a frequency-modulated clock on the bit error rate (BER) and packet error rate (PER) of a Bluetooth system is theoretically analyzed. In addition, theoretical analysis covers the effectiveness of a frequency hopping spread spectrum (FH-SS) scheme and forward error correction (FEC) in mitigating the degradation in the BER and PER caused by clock harmonic interference. The results indicate that the BER and PER strongly depend on the modulating frequency and maximum frequency deviation of the clock harmonic. They also indicate that radiated clock harmonics may considerably degrade the BER and PER when a Bluetooth receiver is very close to a personal computer. Frequency modulating the clock harmonics slightly reduces the BER while it negligibly reduces the PER.

A 1-Gb AG-AND flash memory has been fabricated using 0.13-µm CMOS technology, resulting in a cell area of 0.104 µm2 and a chip area of 95.2 mm2. By applying constant-charge-injection programming and source-line-select programming, a fast page programming time of 600 µs is achieved. The four-bank operation attains a fast programming throughput of 10 MB/s in multilevel flash memories. The compact SRAM write buffers reduce the chip area penalty. A rewrite throughput of 8.3 MB/s is achieved by means of the RAM-write operation during the erase mode.

In this paper, a high-speed logic circuitry using bootstrapped and low-temperature polysilicon (LTPS) technologies for TFT-LCD panels is proposed. The new circuitry realizes high-speed operation owing to the application of a logic-swing voltage that is wider than the power-supply voltage using bootstrapped technology. As a result, the new logic circuitry can be operated at an operational frequency around 3-10 times higher than that of the conventional circuitry under the conditions of a 0.5 pF load capacitor at the output of a noninverting buffer and +10 V power-supply voltages. The new circuit is named "BST-TFT logic circuitry."

If the signal is not Gaussian, then the power spectral density (PSD) approach is insufficient to analyze signals and we resort to estimate the higher order spectra of the signal. However, estimation of the higher order spectra is even more time consuming, for example, the complexity of trispectrum is O(N 4). This problem becomes even more serious when short time Fourier transform (STFT) is computed - computation of the trispectrum is required after every shift of the window. In this paper, a method to recursively compute trispectrum has been presented and it is shown that the computational complexity, for a window size of N, is reduced to be O(N 3) and is the same as the space complexity.

A high-speed drive technique is introduced in which addressing is done by eliminating, instead of accumulating, the wall charges. In the proposed scheme, wall charges are accumulated in all the cells in advance, and then the address discharges take place in selected cells to eliminate the wall charges. Sustain discharges are generated in these cells. In order to realize the proposed address scheme, re-designing of a setup waveforms was necessary. The data pulse of 1.33 µs wide and 84 V was realized in a Ne+10%Xe PDP. A contrast of 3,600:1 was obtained by providing one setup period in a TV field.

This paper proposes a wideband speech coder in which a G.711 bitstream is embedded. This coder has an advantage over conventional coders in that it has a high interoperability with existing terminals so costly transcoding involving decoding and re-encoding can be avoided. We also propose a partial mixing method that effectively reduces the mixing complexity in multiple-point remote conferences. To reduce the complexity, we take advantage of the scalable structure of the bitstream and mix only the lower band of the signal. For the higher band, the main speaker location is selected among remote locations and is redistributed with the mixed lower-band signal. By subjective evaluations, we show that the speech quality can be maintained even when the speech signals are partially mixed.

This study presents an N-gram adaptation technique when additional text data for the adaptation do not exist. We use a language modeling approach to the information retrieval (IR) technique to collect the appropriate adaptation corpus from baseline text data. We propose to use a dynamic interpolation coefficient to merge the N-gram, where the interpolation coefficient is estimated from the word hypotheses obtained by segmenting the input speech. Experimental results show that the proposed adapted N-gram always has better performance than the background N-gram.

In this paper, a parallel combinatory spread spectrum (PC/SS) system using a constant amplitude signaling scheme is proposed. The amplitude of the transmitted signal from multicode transmission systems such as PC/SS systems have a large dynamic range which requires that amplifiers have a wide linearity in the transmitter. From a view point of power efficiency, however, it is reasonable to use non-linear amplifiers rather than linear ones. In that case, the bit error rate performance must degrade because of non-linear distortion. The proposed system can avoid influence of the non-linear amplifiers by making the transmitted signal have a constant amplitude. The bit error rate performance and the data transmission rate performance are investigated. They prove that the proposed system is an attractive candidate among the constant amplitude signaling systems.

We extend the sliding block code in symbolic dynamics to transform J (≥2) sequences of Markov chains with time delays. Under the assumption that the chains are irreducible and aperiodic, we prove the central limit theorem (CLT) for the normalized sums of extended sliding block codes from J sequences of Markov chains. We apply the theorem to the system analysis of asynchronous spread spectrum multiple access (SSMA) communication systems using spreading sequences of Markov chains. We find that the standard Gaussian approximation (SGA) for estimations of bit error probabilities in such systems is the 0-th order approximation of the evaluation based on the CLT. We also provide a simple theoretical evaluation of bit error probabilities in such systems, which agrees properly with the experimental results even for the systems with small number of users and low length of spreading sequences.

A rigorous and simple method is proposed for analyzing guided modes of metallic electromagnetic crystal waveguides. The method is a combination of generalized reflection and transmission matrices and the mode-matching technique. Fast convergence, low computer cost, and high calculating precision are main advantages of the proposed method. This method can easily avoid the relative convergence phenomena than a classical mode-matching method, and the proposed formulation is very suitable to analyzing multilayered problems with very low computer cost. The existence of H-polarized modes in metallic electromagnetic crystal waveguides has been verified.

Combined input and output queuing (CIOQ) switches are being considered as high-performance switch architectures due to their ability to achieve 100% throughput and perfectly emulate output queuing (OQ) switch performance with a small speedup factor S. To realize a speedup factor S, a conventional CIOQ switch requires the switching fabric and memories to operate S times faster than the line rate. In this paper, we propose to use a CIOQ switch with space-division multiplexing expansion and grouped input/output ports (SDMG CIOQ switch for short) to realize speedup while only requiring the switching fabric and memories to operate at the line rate. The cell scheduling problem for the SDMG CIOQ switch is abstracted as a bipartite k-matching problem. Using fluid model techniques, we prove that any maximal size k-matching algorithm on an SDMG CIOQ switch with an expansion factor 2 can achieve 100% throughput assuming input line arrivals satisfy the strong law of large numbers (SLLN) and no input/output line is oversubscribed. We further propose an efficient and starvation-free maximal size k-matching scheduling algorithm, kFRR, for the SDMG CIOQ switch. Simulation results show that kFRR achieves 100% throughput for SDMG CIOQ switches with an expansion factor 2 under two SLLN traffic models, uniform traffic and polarized traffic, confirming our analysis.

The convergence speed of the conventional adaptive LMS algorithms for time delay estimation (TDE) is highly dependent on the spectral distribution of the desired random source signals of interest, thus the performance of TDE might be degraded, dramatically. To solve this problem, in this letter, a DCT-transform domain constrained adaptive normalized-LMS filtering scheme, referred to as the adaptive constrained DCT-LMS algorithm, is devised for TDE. Computer simulation results verify that the proposed scheme can be used to achieve desired performance, for input random signals with different spectral distributions; it outperforms the unconstrained DCT-LMS and time-domain constrained adaptive LMS algorithms.