This paper introduces the design procedure of the contrived network TV broadcasting transcoder/encoder system, especially develops a new variable bit-rate (VBR) coding bit allocation strategy with a constraint channel bandwidth and consistent picture quality for multiple parallel video sequences broadcasting, which accommodates the complicated video sources with different frame rates and GOP structures, and combines the buffer control and the optimized macroblock (MB) coding mode selection. The proposed strategy absorbs several reasonable metrics in a hierarchical structure, and provides flexibility and promotion for resource allocation in multi-access scenario. Experimental results demonstrate the effect of the proposed scheme.

Direct parameter extraction is believed to be the most accurate method for equivalent-circuits modeling of heterojunction bipolar transistors (HBT's). Using this method, the parasitic elements, followed by the intrinsic elements, are determined analytically. Therefore, the quality of the extrinsic elements extraction plays an important role in the accuracy and robustness of the entire extraction algorithm. This study proposes a novel extraction method for the extrinsic elements, which have been proven to be strongly correlated with the intrinsic elements. By utilizing the specific correlation, the equivalent circuit modeling is reduced to an optimization problem of determining six specific extrinsic elements. Converting the intrinsic equivalent circuit into its common-collector configuration, all intrinsic circuit elements are extracted using exact closed-form equations for both the hybrid-π and the T-topology equivalent circuits. Additionally, a general explicit equation on the total extrinsic elements is derived, subsequently reducing the number of optimization variables. The modeling results are presented, showing that the proposed method can yield a good fit between the measured and calculated S parameters.

A structure of a track-and-hold (T/H) circuit based on a pair of complementary floating-gate (FG) MOS transistors is introduced. Its main features include low complexity, low operating supply voltage and gain insensitivity to device mismatches, leading to efficient realization of numerous baseband functions in modern communication systems. The detailed operation and performance analysis of the FG T/H circuit are given. Functional verification of the circuit is provided through a breadboard experiment. The effectiveness of the circuit is verified via simulations where the single T/H cell operating at 10 MHz clock frequency exhibits gain variation less than 0.13% and a dynamic range over 71 dB with the coupling capacitance of 300 fF at 1.5 V supply and 12.75 µW power consumption. As a demonstration on its practical viability, the designed FG T/H cell was also utilized to realize a 10 MS/s 7-tap analog correlator for possible use in modern communication applications.

Mainly, a uniform linear array (ULA) has been used for DOA estimation of coherent signals because we can apply the spatial smoothing preprocessing (SSP) technique. However, estimation by a ULA has ambiguity due to the symmetry, and the estimation accuracy depends on the DOA. Although these problems can be solved by using a uniform circular array (UCA), we cannot estimate the DOA of coherent signals because the SSP technique cannot be applied directly to the UCA. In this paper, we propose to estimate 2-dimensional DOA (polar angles and azimuth angles) estimation of coherent signals using a cylindrical array which is composed of stacked UCAs.

In this letter, we propose a recursive space time decoding method for orthogonal frequency division multiplexing (OFDM) systems exploiting multiple transmit antenna diversity when the channels are fast fading. We first develop a computationally efficient space-time decoding method involving a matrix inversion to mitigate the channel variation effect. We then further reduce the computational complexity of the matrix inversion decoding method via a recursive formulation. Computer simulation results show that the proposed recursive decoding has much better BER performance than Alamouti decoding, requiring much less computation than the matrix inversion decoding. Moreover, the relative advantage in BER performance of the proposed scheme over Alamouti decoding stands out as the Doppler frequency increases.

Intelligent robot control systems based on multiprocessors, sensors, and actuators require a flexible network for communicating various types of real-time data (e.g. sensing data, interrupt signals). Furthermore, serial data transfer implemented using a few wiring lines is also required. Therefore, a CDMA serial communication interface with a new two-step synchronization technique is proposed to counter these problems. The transmitter and receiver fabricated by 0.25 µm digital CMOS technology achieve 2.7 Gcps (gigachips per second) and can multiplex 7 communication channels.

Recently, Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing (MIMO-OFDM) has attracted much attention as a technology achieving high-speed wireless transmission with a limited bandwidth. However, since bit loading and adaptive modulation per sub-carrier should be employed according to the transmission quality of each sub-carrier in MIMO-OFDM, it is very important to understand the frequency correlation characteristics in broadband MIMO channels. This paper investigates the frequency correlation characteristics based on the antenna configuration for actual indoor MIMO channels. The results show that the frequency correlation of the channel capacity for the array antenna configured in the horizontal plane is significantly different compared to that configured in the vertical plane. Moreover, we propose a new cluster model that considers the antenna configuration in both the horizontal and vertical planes to estimate the frequency correlation in broadband MIMO channels.

Call admission control of multiservice hierarchical wireless networks supporting soft handoff is studied, where users with different average call holding times are assigned to different layers, i.e., microcells in the lower layer are used to carry users with shorter call holding time, whereas macrocells in the upper layer are for users with longer call holding time. Further, to give handoff calls priority over new calls, handoff queues are provided for handoff calls that can not obtain the required channel immediately. According to whether handoff queues are provided in microcells and/or macrocells, four different call admission control schemes are proposed and studied. We derive the mathematical model of the considered system with multi- dimensional Markov process, and find the steady state probability distribution iteratively and thus the performance measures of interest: new call blocking probability, forced termination probability, and mean waiting time in handoff queue. Analytical results show that providing handoff queues in both microcells and macrocells can achieve the best blocking performance at the expense of mean waiting time in handoff queue.

A novel image enhancement algorithm that can efficiently detect a small target of panoramic infrared (IR) imagery is proposed. Image enhancement is the first step for detecting and recognizing a small target in the IR imagery. The essence of the proposed algorithm is to utilize the independent histogram equalization (HE) separately over two sub-images obtained by decomposing the given image through the statistical hypothesis testing (SHT). Experimental results show that the proposed algorithm has better discrimination and lower false alarm rate than the conventional algorithms.

This paper proposes a quantization-based image-quality guaranteed watermarking (IQGW) method using a nonorthogonal discrete wavelet transformation. An IQGW method generates watermarked images of a desired image quality for any image, neither with trial and error nor with image-dependent parameters. To guarantee the image-quality, the proposed method adjusts the energy of the watermark sequence to be embedded based on the relationship between a nonorthogonally transformed domain and the spatial domain for the signal energy. This proposed method extracts the embedded watermark by quantization of watermarked coefficients, no reference image, thus, is required. In addition, it is capable of controlling the objective and subjective image-quality of a watermarked image independently. With features mentioned above, the proposed method is suitable for real-time embedding of Motion JPEG 2000 videos. Moreover, it is able to fuse quantization- and correlation-based watermarking.

A speaker identification system based on wavelet transform (WT) derived from codebook design using fuzzy c-mean algorithm (FCM) is proposed. We have combined FCM and the vector quantization (VQ) algorithm to avoid typical local minima for speaker data compression. Identification accuracies of 94% were achieved for 100 Mandarin speakers.

A 3-bit flash analog-to-digital converter (ADC) for electronic dispersion compensation (EDC) was developed using InP HBTs. Nyquist operation was confirmed up to 24 Gsps, which enables oversampling acquisition for 10 Gbit/s non-return-to-zero (NRZ) signals. The ADC can also be operated at up to 37 Gsps for low input frequencies. To reduce aperture jitter and achieve a wide band of over 7 GHz, an analog input signal for all pre-amplifiers and a clock signal for all latched comparators are provided as traveling waves through coplanar transmission lines. EDC was demonstrated by capturing a 10-Gbit/s pseudo-random bit stream (PRBS) with the waveform degraded by polarization-mode dispersion (PMD). By using the captured data, we confirmed that a calculation of a transversal filter mitigates PMD.

This paper presents a technique for reducing spurious output of balanced modulators used in transmitters and arbitrary waveform generators. Two-step upconversion is a convenient way to produce a desired single-sideband (SSB) radio-frequency (RF) signal--baseband quadrature I and Q signals (which are analog outputs of direct digital frequency synthesizers) are upconverted by mixers and local oscillators (LOs)--but mismatches between the DACs in I and Q paths cause spurious output. We propose a method of dynamically matching the I and Q paths by multiplexing two DACs between I and Q paths in a pseudo-random manner. MATLAB simulation shows that multiplexing the two DACs spreads the spurious output, caused by mismatches between the two DACs, in the frequency domain, and reduces the peak level of spurious signals.

In this paper, the throughput performance of the CSK/SSMA ALOHA system with nonorthogonal sequences which combines the ALOHA system with Code Shift Keying using nonorthogonal sequences is analyzed. In this system, the nonorthogonal sequences are constructed by concatenating Mcon orthogonal sequences. The throughput performance of the CSK/SSMA ALOHA system with nonorthogonal sequences is analyzed in consideration that the number of packets changes at intervals of one orthogonal sequence. Moreover, the throughput performance of our system with Channel Load Sensing Protocol (CLSP) is also analyzed. We also examine the influence of unreachable control signal of CLSP. Consequently, it is found that the throughput performance of our system decreases significantly by this analysis. It is also found that the throughput performance of our system improves greatly by using CLSP. However, the unreachable control signal affects the throughput performance of this system, seriously.

This paper presents analysis results on finite-impulse response (FIR) channel estimation used for the equalization in Advanced Television Systems Committee digital television receivers. While channel estimation results have been effectively used for the equalization, the conditions of sufficient order and high signal-to-noise ratio (SNR) were assumed in most cases. To compensate for these unrealistic assumptions, we consider diverse probable conditions for channel estimation, such as reduced order and low SNRs, and then theoretically analyze each estimation case. The analysis shows that the adaptive FIR channel estimator provides an unbiased estimation and matches well its corresponding channel coefficients irrespective of the number of taps of the estimator and the non-causality of the unknown channel. Simulation results verify our analysis on the estimation of terrestrial DTV channels.

Frequency domain blind source separation has the great advantage that the complicated convolution in time domain becomes multiple efficient multiplications in frequency domain. However, the inherent ambiguity of permutation of ICA becomes an important problem that the separated signals at different frequencies may be permuted in order. Mapping the separated signal at each frequency to a target source remains to be a difficult problem. In this paper, we first discuss the inter-frequency correlation based method, and propose a new method using the continuity in power between adjacent frequency components of same source. The proposed method also implicitly utilizes the information of inter-frequency correlation, as such has better performance than the previous method.

This paper proposes a genetic programming method to synthesize passive filter circuits. This method allows both the circuit topology and the component values to be evolved simultaneously. Experiments show that this method is fast and capable of generating circuits which are more economical than those generated by traditional design approaches. In addition, we take into account practical design considerations at high-frequency applications, where the component values are frequency-dependent and restricted to some discrete values. Experimental results show that our method can effectively generate not only compliant but also economical circuits for practical design tasks.

In this paper, we propose a circuit configuration for the low-frequency second-order active RC BPF (band pass filter) which has stable high Q. This proposed circuit is a high Q low-frequency one with a small capacitance, which is realized by applying an output capacitance multiplier to the circuit. Then a detailed circuit analysis is performed for the proposed circuit. From the simulation results of fo and Q for various combinations of circuit element values, we can confirm that the circuit realization of a center frequency of several Hz is possible by employing chip condensers of dozens of nF. The bread-board circuit of this configuration is confirmed to have small temperature dependences of fo and Q by the experiment. It is also clarified from detailed noise analysis and noise measurement that the circuit noise is sufficiently maintained at a low level.

Packet-recognition/code-acquisition (PR/CA) is one of the most important issues in packet communication systems. In a CDMA Unslotted ALOHA system, Multiple Access Interference (MAI) may bring about errors in PR/CA. The MAI mainly stems from already recognized packets and newly arriving packets under the execution of PR/CA. This characteristic of asynchronous transmission in CDMA U-ALOHA systems implies that only one or a few packets arrive at the receiver within a short interval of a execution. Furthermore, newly arriving packets are recognized and code-acquired by using a short preamble part. Consequently, the MAI from the packets under the execution of the PR/CA will be small. Focusing on that point, this paper proposes applying the IC scheme in order to suppress the MAI from the already recognized and code-acquired packets. A performance evaluation demonstrates that such an application is valid due to the small amount of MAI from the packets under the execution of PR/CA. In addition, we demonstrates that the scheme reduces false recognition rather than mis-recognition. Such a scheme improves the performance of not only PR/CA, but also the throughput.

This letter proposes a modified orthogonal frequency division multiplexing (OFDM) signal with low peak-to-average power ratio (PAPR). As the case of previous works, OFDM system exploits a frequency diversity by using a simple symbol repetition. From the presented results, we can see that three modified OFDM signals using one transmit antenna can be implemented with low PAPR, still maintaining the same diversity gain at the receiver as in [9],[10].