Rshdee Alhakim

A Novel Fine Synchronization Method for Dirty Template UWB Timing Acquisition

Timing acquisition constitutes a major challenge in carrying out highly efficient ultra-wideband (UWB) communications. The timing with dirty template (TDT) approach is a promising candidate, which is low-complexity high-performance timing acquisition. In this paper, we describe the dirty template (DT) technique, in order to develop and test timing algorithms in both data aided (DA) and non-data aided (NDA) modes. Then we propose a new method based on Time-Hoping TH codes to improve the performance estimation of the original dirty template algorithms. Simulation shows the estimation error results of the modified method in the DA and NDA modes. It confirms the high performance and fast timing of DA mode, compared to NDA mode, but with less bandwidth efficiency.

Design of tracking loop with dirty templates for UWB communication systems

Maintaining satisfactory synchronization between transmitter and receiver is one of the major challenges in carrying out highly efficient ultra-wideband (UWB) communications. For tracking purposes, the delay-locked loop (DLL) concept is applied. The DLL could be considered as a fundamental tracking technique for UWB devices. In this paper, the reference signal is generated at the receiver based on an approach called timing with dirty template. This approach promises to improve tracking performance while reducing receiver structure complexity. After the reference template is generated, we derive first-order and second-order DLL designs for UWB systems. Furthermore, we utilize the benefits of time-hopping codes to enhance noise handling ability of the DLL. Finally, the parameters of the proposed DLL will be selected to optimize tracking behavior in the presence of the ambient noise and Doppler effects. Simulation results show tracking performance across various DLL parameter values.

Cramer–Rao lower bounds and maximum likelihood timing synchronization for dirty template UWB communications

Timing acquisition constitutes a major challenge in realizing ultra-wideband communications. In this paper, we propose the timing with dirty template (TDT) approach as a promising candidate for achieving rapid, accurate and low-complexity acquisition. We describe the dirty template (DT) technique, in order to develop and test timing algorithms in both modes: data-aided (DA) and non-data- aided (NDA) modes. First, we derive the Cramer–Rao lower bound, which is used as a fundamental performance limit for any timing estimator. Next, the TDT acquisition estimator is achieved by using the Maximum Likelihood concept. Then we propose a new method, based on Time-Hoping codes, to improve the performance estimation of the original dirty template algorithms. Simulation shows the estimation error results of the modified method in the DA and NDA modes. It confirms the high performance and fast timing acquisition of DA mode, compared with NDA mode, but with less bandwidth efficiency.

Data-aided timing estimation in UWB communication systems using dirty templates

Timing acquisition represents a major challenge in carrying out highly efficient ultra-wideband (UWB) communications. The timing with dirty template (TDT) approach is a promising candidate, which is low-complexity high-performance timing acquisition. In this paper, we describe the dirty template (DT) technique, in order to develop and test timing algorithms in Data Aided (DA) mode. In addition, we derive the Cramer-Rao low bound, which is used as fundamental performance limit for any timing estimator. Next, the TDT acquisition estimator is achieved by using Maximum Likelihood (ML) concept. Simulation results confirm that the timing estimation performance is improved with either the signal-to-noise ratio (SNR) or the training sequence number increases.

Internal model control for a self-tuning Delay-Locked Loop in UWB communication systems

Timing synchronization represents a major challenge in carrying out highly efficient ultra-wideband (UWB) communications. The Delay-Locked Loop (DLL) method is widely proposed to maintain the satisfactory synchronization and reduce timing error. In this paper, we modify the structure of DLL, using a novel control strategy in the communication systems, called Internal Model Control (IMC), which is composed of an inverse model (control model) connected in series with the DLL system and a forward model (system model) connected in parallel with the DLL system, this structure has a good performance of overcoming disturbance and deviations of model parameters. Next, we apply the Least-Squares (LS) estimation algorithm method in order to determine the optimal coefficients for the system and control models. Simulation results confirm that the timing estimation performance is improved by using the proposed DLL scheme.

Image quality assessment using nonlinear learning methods

Objective image quality assessment plays an important role in various image processing applications, where the goal of this process is to automatically evaluate the image quality in agreement with human visual perception. In this paper, we propose three different nonlinear learning approaches in order to design image quality assessment models, which serve to predict the perceived image quality. The nonlinear learning approaches used for the aforementioned purpose are nonlinear regression, artificial neural network and regression tree. The largest publicly available image quality database TID2013 is used to benchmark and evaluate the prediction models. The image quality metrics, provided by this TID2013, are not independent and have the redundant information of image quality. This issue might have a negative impact on the training performance and cause overfitting. To avoid this problem and to simplify the model structure, we select the most significant image quality metrics, based on Pearsons correlation measure and principal component analysis. Simulation results confirm that the three nonlinear learning models have high efficiency in predicting image quality. In addition, the regression tree model has low complexity and easy implementation, comparing to the two other prediction models.

Detection of UWB signal using dirty template approach

This paper handles the problem of detecting ultra-wideband signals in the presence of dense multipath channel and ambient noise. To design a low-complexity high-performance signal detection process, the dirty template approach is proposed. We first explain the dirty template technique and its implementation in UWB communication systems. Then, the Neyman–Pearson theorem is applied to derive the UWB signal detector and select the suitable detection threshold values. Finally, the performance of the proposed dirty template detector is evaluated in terms of the detection and false alarm probabilities for different threshold values, signal-to-noise ratio and number of data-aided symbols.

Efficient tracking design in UWB communication systems

Synchronization process is considered as a major challenge for ultra-wideband (UWB) communication systems. Delay-Locked Loop (DLL) method is widely used to maintain the satisfactory timing synchronization and reduce timing offset error between the received and reference signals. In this paper, we propose a novel strategy to design DLL structure, based on Internal Model Control (IMC) concept. Primary simulation results confirm that the proposed DLL tracking works efficiently in the absence of Doppler Effect. However, the loss of tracking may arise with Doppler Effect. To solve this problem, we suggest two different approaches to develop the IMC-DLL structure: The first approach is based on Model-shifter concept, while the second is based on adaptive filter algorithms. The simulation results compare the performance of these proposed approaches with the classical DLL.

Fast-tracking delay-locked loop for UWB communication systems

Maintaining the synchronization between receiver and transmitter in the presence of Doppler effect is considered as a major challenge for ultra-wideband (UWB) communication systems. Delay-Locked Loop (DLL) method is widely proposed to keep the satisfactory synchronization. In this paper, we modify the structure of DLL, using Internal Model Control (IMC). Unfortunately, primary simulation results confirm that the IMC-DLL has a high opportunity to lose tracking in the presence of Doppler effect. In order to solve this problem, we develop the IMC tracking structure by adding an adaptive filter block, which has a simple structure: one addition and one division operators. The simulation results confirm that the proposed IMC-DLL has better transient response, compared with the classical DLL.

Novel design of tracking process for UWB communication systems

Timing synchronization and tracking process is considered as a major challenge for ultra-wideband (UWB) communication systems. Delay-Locked Loop (DLL) method is widely proposed to maintain the satisfactory synchronization and reduce timing offset error between the received and reference signals. In this paper, we modify the structure of DLL, using a novel control strategy in the communication systems, called Internal Model Control (IMC). Primary simulation results confirm that the proposed DLL is able to achieve satisfactory and accurate tracking in the absence of Doppler Effect. However, the loss of tracking may arise in the presence of Doppler Effect. To solve this problem, we develop the proposed IMC-DLL structure by adding two blocks: model-shifter unit and average filter. The simulation results confirm that the proposed DLL has better transient response, compared with the classical DLL.