Data selection can be used in conjunction with adaptive filtering algorithms to avoid unnecessary weight updating and thereby reduce computational overhead. This paper presents a novel correntropy-based data selection method as an alternative to conventional data selection mechanisms based on squared error values. We developed a variable correntropy sensing algorithm to maximize the instantaneous correntropy function for the Gaussian kernel function to mitigate the impact of impulse noise and other forms of noise that can be disregarded in data selection. The proposed data selection mechanism can be implemented with any adaptive filtering algorithm. In simulations, the proposed method (implemented with the least mean squared algorithm) outperformed comparable error-based data selection schemes in terms of hit rate and miss rate, and the resulting weight updating ratio was close to the expected weight updating ratio.

Impulse noise (IN) can seriously degrade the performance of conventional active noise control (ANC) algorithms. Here, we present a novel feedforward ANC algorithm based on an information-theoretic learning framework with the data-reuse scheme of affine-projection-based algorithms. Inspired by the maximum correntropy criterion (MCC), the proposed algorithm is referred to as the modified filtered-x affine-projection-like MCC (MFxAPLMCC). Furthermore, we developed an objective function to maximize the correntropy between the system's desired vectors and the secondary path's output vectors to enhance robustness. Moreover, linear approximation reduces computational complexity, and the optimal step size is derived mathematically to accelerate convergence and increase the noise reduction ratio. The MFxAPLMCC algorithm was thoroughly evaluated in terms of stability and computational complexity; numerical simulations were used to confirm the effectiveness in terms of average noise reduction. The efficiency of our method was verified using three types of input: (1) symmetric alpha-stable (S$\alpha$S) IN, (2) a mixture of sinusoidal and IN, and (3) in-vehicle engine acceleration noise. We also verified the tracking capability of the adaptive algorithm for a case in which the primary path changes abruptly. Furthermore, the real measured acoustic path for ANC in-ear headphone development was used to validate the proposed method in real environments. The proposed algorithm significantly outperformed comparative ANC algorithms in convergence rate and noise reduction ratio. We also confirmed that the theoretical bound for stable step size coincides with the numerical results. The parameter sensitivity of the MFxAPLMCC was analyzed as well.

Loop interference (LI) is the main performance-limiting factor in full-duplex (FD) relaying systems. In this paper, we propose using improper Gaussian signaling (IGS) in joint source and relay transmission to achieve a better LI resistance and, as a result, a better end-to-end system throughput in energy harvesting (EH) enabled FD relaying systems. An alternating optimization (AO) algorithm is proposed to solve the challenging design problem of finding the optimal transmission with IGS at both the source and relay, as well as the optimal power-splitting (PS) factor at the EH-enabled relay. The relationship between the PS factor and the optimal pseudo-variances is derived in closed form. Numerical results demonstrate the superior throughput performance yielded by IGS at the same LI level, and suggest the possibility of employing IGS as a replacement of a sophisticated LI canceller in practical FD relaying systems.

A 10-Gb/s on-chip 1-D eye-opening monitor (EOM) for receiver front-end equalizer boost gain adaptations is presented. The proposed EOM circuits report in real-time horizontal eye-openings using equalizer output by calculating the probability density of the waveform in the central row of pixels of the eye diagram. In addition, a novel multi-phase generator circuit with a delay gain calibration is also demonstrated. It is suitable for EOM circuits to generate a multi-phase sampling clock. The proposed 1-D-EOM circuit is included in a 10-Gb/s receiver design to verify its adaptation functions, and the circuit is implemented using the 65-nm CMOS technology. The sampling phase resolution is 1.5625 ps (where the time for one bit is 100 ps, with a total of 64 phases), and the response time is 64 μs. The total power consumption of the EOM circuit is 1.5 mW with a 1-V supply voltage, and the circuit occupies a layout area of 60 μm × 450 μm. The results show that the reported horizontal eye-opening value is proportional to the value from a real eye diagram monitor from the test buffer.

For rate optimization in interference limited networks, improper Gaussian signaling has shown its ability to outperform conventional proper Gaussian signaling. In this paper, we study a weighted sum-rate maximization problem with improper Gaussian signaling for the multiple-input multiple-output interference broadcast channel. To solve this nonconvex and NP-hard problem, we propose an effective separate covariance and pseudo-covariance matrices optimization algorithm. In the covariance optimization, a weighted minimum mean square error algorithm is adopted, and in the pseudo-covariance optimization, an alternating optimization (AO) algorithm is proposed, which guarantees convergence to a stationary solution and ensures a sum-rate improvement over proper Gaussian signaling. An alternating direction method of multipliers-based multi-agent distributed algorithm is proposed to solve an AO subproblem with the globally optimal solution in a parallel and scalable fashion. The proposed scheme exhibits favorable convergence, optimality, and complexity properties for future large-scale networks. The simulation results demonstrate the superior sum-rate performance of the proposed algorithm as compared with the existing schemes with proper as well as improper Gaussian signaling under various network configurations.

Frequency-domain adaptive echo cancellers are a conventional approach for cancelling the line echoes in wire-line full-duplex data transmission. However, abrupt changes in sampling instant at the receiver side can cause significant signal-to-noise ratio (SNR) degradation since the equivalent echo path is changed simultaneously. This paper proposes a digital compensation method to mitigate such SNR degradation by predicting the coefficients of echo cancellers (EC) while sampling instants are being changed. We mathematically derive the proposed prediction algorithm and numerically verify that our method is insensitive to the nonlinearity of the phase interpolator in the timing recovery loop. As an example, in a 10GBASE-T system, the simulation results show that our method could reduce SNR degradation by up to 2.25 dB. Without compensation, the adaptive EC would require about 2.4 × 105symbol times to recover such degradation.

For rate optimization in interference limited network, improper Gaussian signaling has shown its capability to outperform the conventional proper Gaussian signaling. In this work, we study a weighted sum rate maximization problem with improper Gaussian signaling for the multiple-input multiple-output interference broadcast channel (MIMO-IBC). To solve this nonconvex and NP-hard problem, we propose an effective two-stage algorithm. In the first stage, a weighted mean square error (MSE) minimization algorithm is adopted to compute the transmit covariance matrices, and in the second stage, an alternating direction method of multipliers (ADMM)-based distributed multi-agent algorithm is proposed to obtain the globally optimal pseudo-covariance matrices in a parallel and scalable fashion. Finally, simulation results are presented to demonstrate the superior performance of our algorithm under different signal-to-noise ratio (SNR) and various network scenarios.

Since mobile network operators not only need to satisfy user needs but also have to reduce operating cost (mainly electricity cost) to maintain long-term profitability under strict market competition, energy efficiency (EE), defined as capacity per energy cost, becomes a popular metric for designing mobile networks. For user-centric services, however, the metric of quality of experience (QoE) is more suitable than the metric of capacity or data rate. Therefore, in this paper, we consider a novel network design metric quality-energy efficiency (QEE), defined as the quality of experience achieved per energy consumed. By using QEE as the performance objective, we propose a framework to design user-centric green cloud-based radio access network (CRAN). In particular, the issues of fairness and fronthaul power consumption in C-RAN are taken into account. An efficient approach to solving the non-convex max-min optimization problem for the design of user-centric green C-RAN is proposed. Simulation results validate the near-optimal performance of the proposed algorithm and demonstrate the value of the proposed QEE metric for the design of energy-efficient user-centric CRAN.

In this paper, a novel high-speed, high-accuracy voltage-to-time-difference converter (VTC) is presented. The proposed VTC addresses a load tuning scheme in order to fine tune the delay time of the symmetrical delay cell. This allows further improvement in its linearity. The load tuning circuit also provides a process sensing circuit which dynamically shifts the control voltage of the delay cell to mitigate overloading the following TDCs circuit. The VTC circuit is designed using a 0.18 μm CMOS process and simulation results show that the accuracy is 7 to 8 bits. The bandwidth can be up to 250 MHz. The VTC can be used in a high speed time based data converter with a sampling frequency up to 500 MHz.

In recent years, the research on multiple-input multiple-output (MIMO) wireless communications has attracted much interest. This study investigates precoding techniques for multi-user MIMO communications. By applying QR decomposition to augmented channel matrix based on minimum mean squared error (MMSE) approach plus Tomlinson-Harashima precoding (THP) and equal-rate power allocation, we show that the proposed equal-rate QR-MMSE-THP precoder has better performance than the one based on zero-forcing (ZF) channel matrix, called equal-rate QR-ZF-THP precoder, and the conventional MMSE precoder. In addition, sorting strategies can be adopted to enhance performance with more freedom for QR decomposition compared to block diagonalized decompositions such as block diagonalized-geometric mean decomposition (BD-GMD) and BD-GMD-MMSE schemes while complexity can still be kept practical. Also, the sorting strategies such as full sorting (FS), per-layer sorting (PLS) and per-user sorting (PUS) are discussed and compared in this paper. Simulation results show that for large MIMO systems, the proposed equal-rate QR-MMSE-THP with PLS strategy outperforms the equal-rate BD-GMD-MMSE-THP precoder with PUS.

In this paper, a fast-locking all-digital deskew buffer with duty cycle correction is proposed and implemented. A cyclic time-to-digital converter is introduced to decrease the locking time in conventional register-controlled delay-locked loop to only two input clock cycles in coarse tuning. With the aid of the three half delay lines technique, the mismatch between half delay lines causing the duty cycle distortion can be alleviated by interpolation. A balanced edge combiner to achieve a precise 50% output clock is also presented. A test chip is fabricated in 0.18-μm technology to demonstrate the feasibility of the proposed architecture. The circuit can accept the input clock rates from 250 to 625 MHz with the duty cycle variation within 30% and 70% to generate 50% output clocks. It preserves the capability of closed-loop control with a small area and power consumption.

In this paper, we propose an interference detectable adaptive notch filter (ANF) for GPS receivers. The proposed ANF can estimate the existence of continuous wave interference (CWI) and its power, by exploiting the statistic value within an adaptive second-order infinite impulse response (IIR) filter. Moreover, our ANF is modulized, which allows more modules can be included to deal with multiple CWIs. We also design an adaptation algorithm for each ANF module and prove that the ANF module can adaptively notch the strongest CWI at its input, and this merit enables us to notch the primary CWIs with a limited number of ANF modules. Simulation results show that the adaption of the ANF modules converges in four iterations, and the signal to interference plus noise ratio (SINR) improvements can reach 21 dB.

This paper describes a novel sigma-delta fractional-N synthesizer architecture with fractional spur and quantization noise cancellation which eliminates loop bandwidth limit in traditional fractional-N synthesizers. The proposed synthesizer utilizes a delay line after the reference signal to compensate phase errors and achieves at least 19dB fractional spur and quantization noise improvement if a delay line with 32ps delay resolution is employed in the phase-locked loop with 180kHz loop bandwidth at 3.5GHz synthesized frequency. The improvement can be further enhanced with advanced process with the improved delay resolution.

Timing recovery loops with low loop delay are desirable. This paper presents receiver architectures with asynchronous equalization to reduce the loop delay. We propose a new asynchronous delayed least-mean-square (AD-LMS) adaptation algorithm together with an interaction-free loop to eliminate interaction between timing and equalization loops. In addition, a timing recovery scheme to reduce the timing jitter is developed. The proposed architecture can apply to 10GBASE-T systems. Simulation results show that the conventional approach suffers from the loop-interaction and the proposed method can eliminate this issue. Moreover, our approach has high phase margin, low gain peaking, and low jitter properties.

For 10GBASE-T systems, variation in a multiple-input-multiple-output (MIMO) channel degrades the decision-point signal-to-noise ratio (DP-SNR) owing to imperfect pre-equalisation in the Tomlinson–Harashima precoding (THP) at the transmitter sides and catastrophic error propagation in far-end crosstalk (FEXT) cancellation at the receiver sides. Moreover, by using fixed THP coefficients during data transmission, as specified in the 10GBASE-T standard, and the non-linearity of THP pose challenges in the design of adaptive receivers. The authors propose an adaptive two-stage equalisation and FEXT cancellation (TS-EFC) architecture without updating the THP coefficients to combat channel variation at both the transmitter and receiver sides. In the first stage, we propose a new non-decision-directed FEXT canceller at the transmitter side using a joint training architecture to avoid error propagation. In the second stage, we devise an adaptive MIMO equaliser together with a novel pre-processing unit at the receiver side to combat channel variation. The pre-processing unit can eliminate the non-linearity issue by estimating both effective data sequences and precoded channel inputs. In addition, we develop a block least mean square algorithm that exploits the properties of two-dimensional modulated symbols for updating coefficients of the adaptive MIMO equaliser. Simulation results show that our TS-EFC architecture is robust against channel variation and significantly improves the DP-SNR. It eliminates the error propagation and also achieves faster convergence rates during the adaptation process.

Extraction of correct timing error information is very important for high-speed digital transmission systems. In this letter, a novel effective-data-sequence-based timing error detector (EDS-TED) is presented for a baseband transmission system using nonlinear Tomlinson-Harashima precoding (THP), such as 10GBASE-T. The key idea of our TED is to minimize the mean square error between the received and desired EDS, rather than between the transmitted data signals. This formulation can exploit the autocorrelation between the EDS signals and extract the timing information embedded in the received signal. Moreover, the proposed architecture can lead to a simple and feasible circuit implementation. Simulation results show that a timing loop based on the proposed EDS-TED achieves a superior performance over traditional TED in terms of the peak-to-peak jitter and the TED gain.

Linear amplification with nonlinear components (LINC) technique is a linearization technique for power amplifier designs. By using LINC, the nonlinear power amplifier with high power efficiency can be used to amplify the input signal in a transmitter system with high linearity performance. In this paper, we propose a DSP engine design for LINC wireless transmitter under the WCDMA specification. New algorithms and architectures are proposed, and they can reduce the hardware cost efficiently. We also utilize Agilent ADS to perform mixed-mode system simulation to verify our design. The DSP engine is implemented by Verilog and synthesized with UMC 0.18 /spl mu/m process. The DSP engine area is 0.155 mm/sup 2/ and the maximum clock frequency is 117 MHz. Finally, we use a FPGA to verify our design.

Acquisition is the first step in the signal processing section of a Global Position System (GPS) receiver. It detects the presence of a GPS signal received by antenna and provides estimates of code phase and Doppler frequency to the tracking loops. Three acquisition methods in frequency-domain processing are compared, i.e., namely radix-2 FFT, split-radix-2/4 FFT and. The expectancy of the split-radix algorithm is increasing the acquisition efficiency. It is shown that the split-radix-2/8 FFT can save 25% of data loads and stores compared with split-radix-2/4 FFT. In order to simulate the overall system in an efficient way, the acquisition functions are developed in software architecture running on PC.

GPS is the system combined CDMA technique and trilateration to obtain precision position information. The main goal of this paper is design of high-sensitivity receiver on acquisition of weak GPS signals. A new peak-finding algorithm is developed to search the C/A code phase in the FFT-based correlation domain. This method can estimate the peak location accurately and provides a faster performance in the software-based signal acquisition. The integration time deciding algorithm is also utilized to enhance the capability of waveform search under indoor environments. Simulation results demonstrate that our proposed scheme can acquire the GPS signal efficiently under the power level of-155 dBm in frequency domain processing.

In the last decades, Internet becomes more and more popular. Considering the ownership right of digital image, content provides want to devise and effective way to protect their intelligent property right. Digital watermarking, which protects legal copy and distribution of digital products, has been the hotspot of international academia. In this paper, we propose a dual pyramid watermarking method to protect the ownership right of JPEG-2000 image. Dual pyramid watermarking includes a robust pyramid watermark and a fragile pyramid watermark. The robust pyramid watermark is embedded into the host image by changing the wavelet coefficients according to the characteristics of DWT, ROI, and EBCOT to protect copyrights. The fragile pyramid watermark records the characteristics of the coefficients in the high-high band to detect slight changes and authenticate the owner of the images. This scheme integrates the watermarking process with the JPEG-2000 compression procedures. We are able to anticipate which of the transformed coefficients will be discarded by the compression scheme. Experimental results show that the proposed technique successfully survives JPEG-2000 compression and can detect modification of the host image.

Fast carrier recovery loops are essential in high-dynamic global positioning system receivers. A new digital phase-locked loop (DPLL) system incorporating a fuzzy bandwidth controller (FBC) is presented in this letter. The FBC provides a time-varying bandwidth and adjusts the loop filter coefficients to improve DPLL tracking capability. When the phase error or phase difference error becomes large in the presence of significant accelerations, the loop bandwidth increases adaptively and performs rapid locking. Simulation results show that our receiver does achieve a superior performance over conventional tracking loops in terms of shorter settling time and wider frequency ramp range, while preventing the occurrence of cycle slipping.

A detailed analysis of optical coherent phase diversity single-filtered and dual-filtered frequency-shift keying (FSK) receivers corrupted by shot and phase noise is presented. With delay and cross-product detection, the effect of various parameters, including bandwidths of filters, delay time, frequency deviation and noises, are investigated. The tolerance of phase noise is quite large, when small time delay in the demodulator and appropriately large frequency deviation is selected. It is also shown that there exists an optimal bandwidth for the first filter in the dual-filtered FSK receiver. For a total linewidth equal to half of the bit rate, the power penalty incurred (at BER=10/sup -9/) is 1.92 dB when the modulation index is 4, provided that an optimal filter bandwidth and a frequency deviation-delay product of 0.25 are used.>