Survey on Different Architectures of DLMS Adaptive Filter

ABSTRACT: The LMS Adaptive filter has wide range of applications but it cannot support pipelined operations because of its recursive behaviour. An efficient architecture of Delayed LMS algorithm thus has been proposed that supports pipelining. The paper discuses about the DLMS algorithm and different architectures of DLMS adaptive filter in brief. These architectures concentrates on increasing usable frequency, minimize the adaption delay and area. The comparison between these various architectures based on critical path, hardware elements required is discussed. KEYWORDS: Adaptive Filter, LMS algorithm, DLMS Algorithm, Critical Path, Pipelining. I.INTRODUCTION The adaptive filter itself can adjust its transfer function according to an optimizing algorithm and object can be achieved by the modification of its characteristics. They provide flexibility and accuracy in the field of communication and control. The LMS (Least Mean Square) algorithm is widely used because of its easy calculations and better convergence performance. LMS adaptive filter has wide range of applications in communication and DSP (Digital Signal Processing) such as predictor, system identification, noise cancellation, equalization. However the direct implementation of LMS algorithm has long critical path which is due to the complex inner product computations to obtain the filter outpu

REAL-TIME ADAPTIVE PULSE COMPRESSION ON RECONFIGURABLE, SYSTEM-ON-CHIP (SOC) PLATFORMS

New radar applications need to perform complex algorithms and process a large quantity of data to generate useful information for the users. This situation has motivated the search for better processing solutions that include low-power high-performance processors, efficient algorithms, and high-speed interfaces. In this work, hardware implementation of adaptive pulse compression algorithms for real-time transceiver optimization is presented, and is based on a System-on-Chip architecture for reconfigurable hardware devices. This study also evaluates the performance of dedicated coprocessors as hardware accelerator units to speed up and improve the computation of computing-intensive tasks such matrix multiplication and matrix inversion, which are essential units to solve the covariance matrix. The tradeoffs between latency and hardware utilization are also presented. Moreover, the system architecture takes advantage of the embedded processor, which is interconnected with the logic resources through high-performance buses, to perform floating-point operations, control the processing blocks, and communicate with an external PC through a customized software interface. The overall system functionality is demonstrated and tested for real-time operations using a Ku-band testbed together with a low-cost channel emulator for different types of waveforms

FPGA-based Signal Processor for Detection and Interpretationof Pulsed Laser Radiation

A novel design technique for detection and interpretation of pulsed laser radiationimplemented on Xilinx Spartan-III field programmable gate arrays (FPGA) is presented. The designarchitecture is modular with high performance and unparalleled flexibility that simplifies designchanges. The design gives superior accuracy and scalability and is applicable to a range ofFPGA technologies

Implementação em EPGA de técnicas de equalização adaptativa utilizando o algoritmo Cordic

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Elétrica.Esta dissertação apresenta uma implementação em uma FPGA (Arranjo de Portas Programáveis em Campo - em inglês, Field Programmable Gate Array de um equalizador adaptativo que utiliza o algoritmo LMS trigonométrico. Este algoritmo utiliza variáveis trigonométricas, que são relacionadas monotonicamente aos coeficientes do equalizador. O algoritmo LMS trigonométrico é especialmente apropriado para uma realização utilizando processadores CORDIC (Computador Digital de Rotação de Coordenadas - em inglês, Coordinate Rotation Digital Computer, já que estes calculam simultaneamente as funções trigonométricas necessárias às operações de filtragem e adaptação dos coeficientes. A utilização deste algoritmo impõe a necessidade da definição de um hipercubo, no qual deve estar contido o ponto de mínimo da função objetivo (potência do erro entre o sinal desejado e a saída do equalizador). A literatura disponível não é clara quanto à definição deste hipercubo. Esta dissertação propõe a adoção do procedimento multisplit para facilitar a definição desse hipercubo. Simulações realizadas indicam que a utilização do procedimento multisplit permite que o algoritmo LMS trigonométrico alcance a convergência em uma variedade de canais sem a necessidade de uma busca exaustiva dos valores das coordenadas do hipercubo

Development of a Real-time Ultra-wideband See Through Wall Imaging Radar System

Ultra-Wideband (UWB) See-Through-Wall (STW) technology has emerged as a musthave enabling technology by both the military and commercial sectors. As a pioneer in this area, we have led the research in addressing many of the fundamental STW questions. This dissertation is to investigate and resolve a few hurdles in advancing this technology, and produce a realizable high performance STW platform system, which will aid the STW community to find the ultimate answer through experimental and theoretical work. The architectures of a realizable STW imaging system are thoroughly examined and studied. We present both a conceptual system based on RF instruments and a standalone real-time system based on custom design, which utilize reconfigurable design architecture and allows scaling down/up to a desired UWB operating frequency with little difficulty. The systems will serve as a high performance platform for STW study and other related UWB applications. Along the way to a complete STW system, we have developed a simplified transmission line model for wall characteristic prediction; we have developed a scalable synthetic aperture array including both the RF part and the switch control/synchronization part; we have proposed a cost-effective and efficient UWB data acquisition method for real-time STW application based on equivalent-time sampling method. The measurement results reported here include static image formation and tracking moveable targets behind the wall. Even though digital signal processing to generate radar images is not the focus of this research, simple methods for image formation have been implemented and results are very encouraging

Complex-valued Adaptive Digital Signal Enhancement For Applications In Wireless Communication Systems

In recent decades, the wireless communication industry has attracted a great deal of research efforts to satisfy rigorous performance requirements and preserve high spectral efficiency. Along with this trend, I/Q modulation is frequently applied in modern wireless communications to develop high performance and high data rate systems. This has necessitated the need for applying efficient complex-valued signal processing techniques to highly-integrated, multi-standard receiver devices. In this dissertation, novel techniques for complex-valued digital signal enhancement are presented and analyzed for various applications in wireless communications. The first technique is a unified block processing approach to generate the complex-valued conjugate gradient Least Mean Square (LMS) techniques with optimal adaptations. The proposed algorithms exploit the concept of the complex conjugate gradients to find the orthogonal directions for updating the adaptive filter coefficients at each iteration. Along each orthogonal direction, the presented algorithms employ the complex Taylor series expansion to calculate time-varying convergence factors tailored for the adaptive filter coefficients. The performance of the developed technique is tested in the applications of channel estimation, channel equalization, and adaptive array beamforming. Comparing with the state of the art methods, the proposed techniques demonstrate improved performance and exhibit desirable characteristics for practical use. The second complex-valued signal processing technique is a novel Optimal Block Adaptive algorithm based on Circularity, OBA-C. The proposed OBA-C method compensates for a complex imbalanced signal by restoring its circularity. In addition, by utilizing the complex iv Taylor series expansion, the OBA-C method optimally updates the adaptive filter coefficients at each iteration. This algorithm can be applied to mitigate the frequency-dependent I/Q mismatch effects in analog front-end. Simulation results indicate that comparing with the existing methods, OBA-C exhibits superior convergence speed while maintaining excellent accuracy. The third technique is regarding interference rejection in communication systems. The research on both LMS and Independent Component Analysis (ICA) based techniques continues to receive significant attention in the area of interference cancellation. The performance of the LMS and ICA based approaches is studied for signals with different probabilistic distributions. Our research indicates that the ICA-based approach works better for super-Gaussian signals, while the LMS-based method is preferable for sub-Gaussian signals. Therefore, an appropriate choice of interference suppression algorithms can be made to satisfy the ever-increasing demand for better performance in modern receiver design

MIMO Systems

In recent years, it was realized that the MIMO communication systems seems to be inevitable in accelerated evolution of high data rates applications due to their potential to dramatically increase the spectral efficiency and simultaneously sending individual information to the corresponding users in wireless systems. This book, intends to provide highlights of the current research topics in the field of MIMO system, to offer a snapshot of the recent advances and major issues faced today by the researchers in the MIMO related areas. The book is written by specialists working in universities and research centers all over the world to cover the fundamental principles and main advanced topics on high data rates wireless communications systems over MIMO channels. Moreover, the book has the advantage of providing a collection of applications that are completely independent and self-contained; thus, the interested reader can choose any chapter and skip to another without losing continuity