A second order charge pump (SOCP) scheme is proposed in this letter. Compared with the conventional single charge pump, the second order charge pump does not suffer phase errors caused by the output voltage dependent current mismatches. Also, the second order charge pump can be implemented in a mixed-mode type, enabling the fast lock and the various operation modes simultaneously. The proposed SOCP has been adopted into the duty cycle corrector (DCC) loops of DDR2 DRAM, and shows a much widened correction range owing to the removal of the parasitic effects.

This paper considers the optimal generator matrices of a given binary cyclic code over a binary symmetric channel with crossover probability p→0 when the goal is to minimize the probability of an information bit error. A given code has many encoder realizations and the information bit error probability is a function of this realization. Our goal here is to seek the optimal realization of encoding functions by taking advantage of the structure of the codes, and to derive the probability of information bit error when possible. We derive some sufficient conditions for a binary cyclic code to have systematic optimal generator matrices under bounded distance decoding and determine many cyclic codes with such properties. We also present some binary cyclic codes whose optimal generator matrices are non-systematic under complete decoding.

This paper discusses the influence of the nonlinearity of analog-to-digital converters (ADCs) on the performance of orthogonal frequency division multiplexing (OFDM) receivers. We evaluate signal constellations and bit error rate performances while considering quantization errors and clippings. The optimum range for an ADC input amplitude is found as a result of the trade-off between quantization error and the effects of clipping. In addition, it is shown that the peak-to-average power ratio (PAPR) of the signal is not a good measure of the bit error rate (BER) performance, since the largest peaks occur only with very low probabilities. The relationship between the location of a subcarrier and its performance is studied. As a result, it is shown that the influence of the quantization error is identical for all subcarriers, while the effects of clipping depend on the subcarrier frequency. When clipping occurs, the BER performance of a subcarrier near the center frequency is worse than that near the edges.

In this article, we considered the asymptotic expectations of the prediction error and the fitting error of a regression model, in which the component functions are chosen from a finite set of orthogonal functions. Under the least squares estimation, we showed that the asymptotic bias in estimating the prediction error based on the fitting error includes the true number of components, which is essentially unknown in practical applications. On the other hand, under a suitable shrinkage method, we showed that an asymptotically unbiased estimate of the prediction error is given by the fitting error plus a known term except the noise variance.

This letter presents an iterative decision feedback channel estimation scheme for burst mode COFDM transmission. The feature of the proposed scheme is that the channel estimation using metrics comparison is applied to the initial stage of the iterative mechanism, which makes it possible to provide a reliable data stream at the initial stage. Computer simulation results show that the proposed approach provides better BER than the traditional iterative decision feedback channel estimation scheme irrespective of the number of iterations.

We derived explicit formulas for evaluating the error vector magnitude (EVM) from the amplitude distortion (AM-AM) and phase distortion (AM-PM) of power amplifiers (PAs) in orthogonal frequency-division multiplexing (OFDM) systems, such as the IEEE 802.11a/g wireless local area networks (WLANs) standards. We demonstrated that the developed formulas allowed EVM simulation of a memoryless PA using only a single-tone response (i.e. without OFDM modulation and demodulation), thus enabling us to easily simulate the EVM using a harmonic-balance (HB) simulator. This HB simulation technique reduced the processing time required to simulate the EVM of a PA for the IEEE 802.11a standard by a factor of ten compared to a system-level (SL) simulation. We also demonstrated that the measured EVM of a PA module for the IEEE 802.11g could accurately be predicted by applying the measured static AM-AM and AM-PM characteristics to the derived formulas.

The selection of motion vectors plays an important role in the error propagation process between inter-frames. In this letter, an end-to-end prediction error calculation method is proposed and is used for the rate-distortion optimized selection of motion vectors. Simulation results show that the robustness of encoded video streams under error-prone environment is improved.

The I/Q unbalance which is generated by a non-ideal component is an inevitable physical phenomenon and leads to performance degradation when we implement a practical two-dimensional (2-D) modulation system. In this paper, we provide an exact and general expression involving the 2-D Gaussian Q-function for the SER/BER of arbitrary 2-D signaling with I/Q amplitude and phase unbalances over an additive white Gaussian noise (AWGN) channel by using the coordinate rotation and shifting technique. Through Monte Carlo simulations we verify our expression provided here for 16-star Quadrature Amplitude Modulation (QAM).

This paper investigates the impact of chip duty factor (DF) in DS-UWB system with Rake receiver over AWGN and UWB indoor multipath environment corresponding to system parameters such as spreading bandwidth and chip length. Manipulating DF in DS-UWB system offers several advantages over multipath channel and thus, capable of improving system performance for better quality of communication. Although employing lower DF generally improves performance, in some exceptional cases on the other hand, degradation can be observed despite decreasing DF. Therefore, the objective of this paper is to clarify the relationship between DF and DS-UWB system performance. We discovered that with constant processing gain and spreading bandwidth, performance improvement can be observed at DF lower than 0.17. Additionally, with spreading bandwidth as tradeoff parameter, significant performance improvement can only be observed below DF of 0.85.

The computational error of the multilevel fast multipole algorithm is studied. The error convergence rate, achievable minimum error, and error bound are investigated for various element distributions. We will discuss the boundary between the large and small buffer cases in terms of machine precision. The needed buffer size to reach double precision accuracy will be clarified.

This letter proposed a linear precoding scheme for the V-BLAST system that requires only knowledge of the statistical CSI; the transmitter does not need the instantaneous CSI. Power allocation on the eigenmodes of the transmit correlation matrix is one way to minimize bit error rate (BER). Simulation results show that the proposed precoding V-BLAST system provides a significant reduction in the BER compared with the conventional V-BLAST systems.

This letter presents an extended Pawula F-function for computing the error rate of generalized M-ary phase shift keying (MPSK) system in the presence of phase error, quadrature error, and I-Q gain mismatch over additive white Gaussian noise (AWGN) and fading channels. The extended Pawula F-function conditioned on an instantaneous fading carrier-to-noise ratio (CNR) is derived in the form of the Craig representation.

In this paper, we evaluate the performance of asymmetric Time Division Duplex (TDD) system that employs Adaptive Modulation and Coding (AMC) and Hybrid ARQ, with consideration of the effect of control delays in TDD. Channel reciprocity characteristic in TDD allows utilization of open loop channel estimation to choose appropriate modulation and coding scheme (MCS) level for AMC. However, control delay in AMC and HARQ depends on TDD time slot allocation formats. Large control delay in AMC will result in false MCS selection due to the poor channel correlation between measured channel state from the received signals and instantaneous channel state of actual transmission with the MCS selected based on the measured channel state. We present an analytical approach to calculate the probability of MCS level selection error in different channel conditions for different asymmetric time slot allocations. From the theoretical and simulation results, it is shown that the instantaneous throughput per slot depends not only on maximum Doppler frequency but also on asymmetric slot allocations. Average delay time that yields error free packet reception in the downlink increases as the number of continuous downlink slots increases.

This paper describes a novel TCAM architecture designed for enhancing the soft-error immunity. An associated embedded DRAM and ECC circuits are placed next to TCAM macro to implement a unique methodology of recovering upset bits due to soft errors. The proposed configuration allows an improvement of soft-error immunity by 6 orders of magnitude compared with the conventional TCAM. We also propose a novel testing methodology of the soft-error rate with a fast parallel multi-bit test. In addition, the proposed architecture resolves the critical problem of the look-up table maintenance of TCAM. The design techniques reported in this paper are especially attractive for realizing soft-error immune, high-performance TCAM chips.

This letter considers an iterative decoding algorithm for non-binary linear block codes in which erasure and error decoding is performed for input words given by the sums of a hard-decision received sequence and given test patterns. We have proposed a new selection method of test patterns for the iterative decoding algorithm. Simulation results have shown that the decoding algorithm with test patterns by the proposed selection method provides better error performance than a conventional iterative decoding algorithm with the same number of the error and erasure decoding iterations over an additive white Gaussian noise channel using binary phase-shift keying modulation.

In this paper, we present a new low-cost concurrent error detection (CED) S-Box architecture for the Advanced Encryption Standard (AES). Because the complexity and the nonlinearity, it is difficult to develop error detection algorithms for the S-Box. Conventionally, a parity checked S-Box is implemented with ROM (read only memory). In some applications, for example, smart cards, both chip size and fault detection are demanded seriously. ROM-based parity checking cannot meet the demands. We propose our CED S-Box (CEDSB) architecture for two reasons. The first is to design a S-Box without ROM. The second is to obtain a compact S-Box with real time error detection. Based on the composite field, we develop the CEDSB architecture to implement the fault detection for the S-Box. The overhead of the CED for the S-Boxes in GF((24)2) and in GF(((22)2)2) are 152 and 132 NAND gates respectively. The amount of extra gates used for the CEDSB is nearly equal to that of the ROM-based CED S-Box (131 NAND gates). The chip area of the ROM-based CED S-Box, the CEDSBs in GF((24)2), and in GF(((22)2)2) are 2996, 558, and 492 NAND gates separately. The chip area of the CEDSB is more compact than a ROM-based CED S-Box.

In this letter, we propose a novel signal detection method for spatially multiplexed multiple input multiple output (MIMO) systems, based on the idea of ordered successive interference cancellation (OSIC). In the proposed method, we try every possible value as the first detected symbol instead of making a decision. Although the proposed method requires slightly increased complexity compared to the conventional OSIC, the proposed method eliminates the error propagation from the first detected symbol, so it offers significantly better error performance compared to the conventional OSIC. We compare the proposed method with previous ML, ML-DFE, QRD-M, MMSE, MMSE-OSIC detection methods in terms of the error performance and the computational complexity, and show that the proposed method offers a good performance-complexity trade-off.

For fitting an ellipse to a point sequence, ML (maximum likelihood) has been regarded as having the highest accuracy. In this paper, we demonstrate the existence of a "hyperaccurate" method which outperforms ML. This is made possible by error analysis of ML followed by subtraction of high-order bias terms. Since ML nearly achieves the theoretical accuracy bound (the KCR lower bound), the resulting improvement is very small. Nevertheless, our analysis has theoretical significance, illuminating the relationship between ML and the KCR lower bound.

We have researched high dimensional parity-check (HDPC) codes that give good performance over a channel that has a very high error rate. HDPC code has a little coding overhead because of its simple structure. It has hard-in, maximum detected bit flipping (MDBF) decoding that has reasonable decoding performance and computational cost. In this paper, we propose a modified algorithm for MDBF decoding and compare the proposed MDBF decoding with conventional hard-in decoding.

A 3 dimensional (3D) error diffusion method based on edge detection for flat panel display (FPD) is presented. The new method diffuses errors to the neighbor pixels in current frame and the neighbor pixel in the next frame. And the weights of error filters are dynamically adjusted based on the results of edge detection in each pixel's processing, which makes the weights coincide with the local edge feathers of input image. The proposed method can reduce worm artifacts and improve reproduction precision of image details.