In this paper, a 3 V 8-bit 200MSPS CMOS folding/interpolation Analog-to-Digital Converter is proposed. It employs an efficient architecture whose FR (Folding Rate) is 8, NFB (Number of Folding Block) is 4, and IR (Interpolating Rate) is 8. For the purpose of improving SNR, distributed track and hold circuits are included at the front end of input stage. In order to obtain a high speed and low power operation, an improved dynamic analog latch is proposed. Further, a digital encoder based on a novel thermometer algorithm and a delay error correction algorithm is proposed. The chip has been fabricated with a 0.35 µm 2-poly 3-metal n-well CMOS technology. The effective chip area is 1200 µm 800 µm and it dissipates about 210 mW at 3 V power supply. The INL is within 1 LSB and DNL is within 1 LSB, respectively. The SNR is about 43 dB, when the input frequency is 10 MHz at 200 MHz clock frequency.

A digital calibration technique, which corrects errors due to capacitor mismatch in pipelined ADC and directly measures the error coefficients using the ADC INL plot, is described. The proposed technique can be applied for various types of pipelined ADC architectures. Test results using an implemented 10-bit pipelined ADC show that the ADC achieves a peak signal-to-noise-and-distortion ratio of 56.5 dB, a peak integral non-linearity of 0.3 LSB, and a peak differential non-linearity of 0.3 LSB using the digital calibration.

Adaptive optimization of the notch bandwidth of a lattice-based adaptive infinite impulse response (IIR) notch filter is presented in this paper. The filter is used to improve the performance of a direct sequence spread spectrum (DSSS) binary phase shift keying (BPSK) communication system by suppressing a narrow-band interference at the receiver. A least mean square (LMS) algorithm used to adapt the notch bandwidth coefficient to its optimum value which corresponds to the maximum signal to noise ratio (SNR) improvement factor is derived. Bit error rate (BER) improvement gained by the DSSS communication system using the filter with the optimized notch bandwidth is also shown. Computer simulation results are compared with those obtained analytically to demonstrate the validity of theoretical predictions for various received signal parameters.

Detection loss due to phase error in a carrier tracking loop is analyzed and simulated for a code division multiple access system with BPSK and QPSK modulations in a Rayleigh fading channel. For a specific BER, the detection loss due to phase error is defined as an increase of required SNR to maintain the same BER without phase error. A nonlinear Fokker-Planck method is employed to analyze first-order PLL (phase locked loop) performance. From the simulation results, it is confirmed that the phase noise induces significant detection loss, which eventually leads to degradation of the BER performance.

In this paper, a Turbo codec with reduced number of iterations is proposed. By inserting an even parity-check bit every six information bit, the coder can increase the minimum distance of the codewords and the number of iterations is reduced. Furthermore, this codec accommodates automatic repeat request (ARQ) scheme easily.

The technique of the digital watermarking is one of the ways to resolve copyright ownership and verify originality of digital contents (e.g. text documents, audio, still images, video, etc.). In this paper, we obtained global robustness and minimal error through using frame based watermarking and including DC and AC coefficients of DCT transform, which extended conventional watermarking method having local robustness and error through using block based and/or AC coefficients only. As a result, the high robustness and quality of our method were proved by several attacks such as lossy image compression, linear filtering, additive noise, scaling, cropping and so on. Watermarks embedded by our method are survived most of JPEG compressions.

This paper describes a new approach to the digital watermarking of motion pictures dedicatedly for the MPEG-4 video coding, which intends to enhance the error detection ability. The conventional method lacks not only the detection ability but also the compatibility with video decoders widely used today. Thus in this approach the digital watermarks are to be embedded into the quantized DCT (Discrete Cosine Transform) coefficients for the error detection, where the prevention of the picture quality degradation is also attempted. Experimental results are shown to demonstrate that the error detection ability of the proposed approach is significantly improved, as compared with that of the conventional method, and that the degradation of the picture quality by the watermarking is extremely small.

It has been shown that the performances of single-receiver ARQ schemes are largely dependent on the packet-error process, i.e., for dependent packet-error environment, they are under- or over- estimated by analyzing them under the assumption that packet-errors occur at random. While, multi-receiver ARQ's have not been analyzed and evaluated for dependent packet-error process. In this paper, we analyze the throughput efficiency of the fundamental multi-receiver Go-back-N ARQ scheme, which can be implemented very simply, over an unreliable channel modeled by the two-state Markov process. Any receiver erroneously receives a packet with probability inherent to each state. From numerical results, we show that the throughput efficiency of the fundamental multi-receiver Go-Back-N ARQ scheme depends on the number of receivers, round-trip-delay, and the characteristic of the Markov process. Also we show that the throughput efficiency of the fundamental multi-receiver Go-Back-N ARQ scheme for larger decay factor and larger difference between packet error probability at each state is considerably better than that for the random error pattern.

This letter presents a code which corrects single bit errors in any location of the word as well as l-bit burst errors occurred in an important part of the word. The proposed code is designed by product of the parity check matrix of the l-bit burst error correcting codes and the matrix which converts input unequal errors into equal errors. This letter also demonstrates the evaluation of the code, and presents the extended codes with two-level burst error correcting capabilities by interleaving.

Practical image restoration filters usually include a parameter that controls regularizability, trade-off between fidelity of a restored image and smoothness of it, and so on. Many criteria for choosing such a parameter have been proposed. However, the relation between these criteria and the squared error of a restored image, which is usually used to evaluate the restoration performance, has not been theoretically substantiated. Sugiyama and Ogawa proposed the subspace information criterion (SIC) for model selection of supervised learning problems and showed that the SIC is an unbiased estimator of the expected squared error between the unknown model function and an estimated one. They also applied it to restoration of images. However, we need an unbiased estimator of the unknown original image to construct the criterion, so it can not be used for general situations. In this paper, we present a modified version of the SIC as a new criterion for choosing a parameter of image restoration filters. Some numerical examples are also shown to verify the efficacy of the proposed criterion.

We propose a subchannel power control scheme in the OFDM system, which transmits data with a variable power level for each subchannel based on the received SNR. The OFDM system, employing the D-QPSK modulation and the proposed subchannel power control with a grouping coefficient equal to 3, gives about 2.3 dB gain in Eb/N0 comparing with the conventional OFDM system, under the two-ray multipath channel with the mean value of the second-ray's attenuation coefficient equal to 0.25, for the required BER equal to 10-5.

In positioning systems NLOS (Non-Line of Sight) errors always cause remarkable positive bias and directly increase range measurement errors. In this paper, a new method is proposed to calibrate NLOS errors in positioning systems by using the relationship between mean excess delay and delay spread measured at a mobile station. The computer simulations showed that the proposed calibration technique effectively reduces the positioning error caused by urban NLOS environment.

Soft bit speech decoding, as a new approach of error concealment, is applied to the mixed excitation linear prediction (MELP) algorithm. Average residual redundancies of the quantized parameters are exploited in the error concealment process as an a priori knowledge of the source. Results show a significant SNR improvement for parameters decoded using the error concealment scheme.

The circular decoding algorithm for tail-biting convolutional codes is executed using a fixed number of computations and is suitable for DSP/ASIC implementations. This letter presents the performance and complexity trade-off in the circular decoding algorithm using an analytic bound on the error probability. An incremental performance improvement is shown as the complexity increases from O(L) to O(L+10K) where L is the length of the decoding trellis and K is the constraint length. The decoding complexity required to produce the maximum-likelihood performance is presented, which is applicable to many codes of practical interest.

Adaptive Fourier analysis of sinusoidal signals in noise is of essential importance in many engineering fields. So far, many adaptive algorithms have been developed. In particular, a filter bank based algorithm called constrained notch Fourier transform (CNFT) is very attractive in terms of its cost-efficiency and easily controllable performance. However, its performance becomes poor when the signal frequencies are non-uniformly spaced (or spaced with unequal intervals) in the frequency domain. This is because the estimates of the discrete Fourier coefficients (DFCs) in the CNFT are inevitably corrupted by sinusoidal disturbances in such a case. This paper proposes, at first, a modified CNFT (MCNFT), to compensate the performance of the CNFT for noisy sinusoidal signals with known and non-uniformly spaced signal frequencies. Next, performance analysis of the MCNFT is conducted in detail. Closed form expression for the steady-state mean square error (MSE) of every DFC estimate is derived. This expression indicates that the MSE is proportional to the variance of the additive noise and is a complex function of both the frequency of each frequency component and the pole radius of the bandpass filter used in the filter bank. Extensive simulations are presented to demonstrate the improved performance of the MCNFT and the validity of the analytical results.

This letter presents the empirical error performance of combining method of a binary numerical code and a single error correcting code on Gaussian channel by belief propagation (BP) decoding algorithm. The numerical codes mentioned here are constructed with any symbol value and have the parity check matrices in reduced-echelon form whose elements are binary (0 and 1). The simulation results show that the method yields good decoding error performance for medium code lengths.

A new method of error concealment for MPEG videos, in which motion vectors are hidden in an MPEG bitstream as a watermark, is proposed in this paper. Several conventional methods conceal error regions by using motion vectors, which are re-estimated in a decoding process. These methods, however, have two problems: (1) The accuracy of a re-estimated motion vector is lower than that of an estimated motion vector in an encoding process. (2) A large amount of calculation is required to re-estimate motion vectors. The proposed method overcomes these problems by using hidden accurate motion vectors. That is, it hides several bits in each 88 DCT block of all frames and, simultaneously, inhibits the image degradation caused by hiding motion vectors. In addition, it has upward compatibility with a standard MPEG decoder and can be combined with conventional methods. Simulation results show that the accuracy of error concealment by the new method is higher than that of the conventional methods.

Eigenstructure-based beamformers suffer form performance degradation due to pointing errors when the number of the incident signals is incorrectly detected or when the desired signal is much stronger than the interferences. We present a robust beamformer with the self-correction of look direction errors, based on the Newton method. Even though there are errors in the detection of the incident signal number as well as in the presumed look direction, it can achieve optimum performance with no errors.

Transmitter diversity is a powerful technique to improve the transmission quality of downlink in microcellular mobile communications systems. Under cochannel interference (CCI) at the base station (BS), the transmitter diversity is not necessarily effective, because the desired-plus-interference signal power used as a criterion of downlink branch selection is not always relative to the downlink propagation condition. This paper proposes the theoretical derivation of bit error rate (BER) performance in the transmitter diversity under CCI occurring at BS, as parameters of average SIR at BS, normalized Doppler frequency, and so on. It is confirmed from the correspondence of theoretical results with simulation results that the proposed theoretical approach is applicable to the CCI environments at BS.

An advanced center biased search algorithm for block motion estimation is proposed in this letter. It adopts an innovative center biased search strategy to get correct motion vector. The computational complexity is reduced by strict application of the unimodal error surface assumption and half stop technique. Experimental results show that proposed algorithm has improved performance as compared to the conventional block matching algorithms.