Digital Signal Processing Algorithms for Communication Receivers: Synchronization, Equalization and Channel Estimation

• Main Authors: Kun-Chien Hung, 洪崑健
• Other Authors: David W. Lin
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/92166435186379345554

博士 === 國立交通大學 === 電子工程系所 === 97 === The communication receiver can be divided into the signal processing unit and the data processing unit. The signal processing unit is mainly used to solve problems of the signal synchronization, the channel equalization and the channel estimation. The topic of this thesis is design of the signal processing algorithms and discusses various issues in synchronization, equalization and channel estimations. According to the application of the systems, this work is divided into three parts. Part I is the receiver design in wired single carrier (SC) system; Part II is the receiver design of multi-carrier orthogonal frequency-division multiplexing (OFDM) systems over a wireless channel; Part III is the transceiver design of the wide-band MIMO systems. In Part I, the topics of the receiver design in SC systems, we address the carrier recovery and the blind decision-feedback equalization (DFE). In carrier recovery issue, we discuss two techniques: the carrier frequency estimation and the carrier recovery loop. For the carrier frequency estimation, we study the frequency estimator using the delay correlation, derive the performance of the Fitz’s algorithm, propose a low-complexity and high-accuracy multi-resolution algorithm, and then apply the proposed algorithm for the frequency estimation in QAM system. For the carrier recovery loop, we propose a series of the blind phase detections (PDs) according to the reduced-constellation concept, which can enhance the acquisition range of the carrier frequency offset. In addition, when considering the acquisition speed and the tracking stability, we furthermore derive a hybrid PD, which combines the decision-directed PD and the reduced-constellation PD, and the mechanism of the dynamic control of the loop bandwidth. In the design topic of blind DFE, we focus on the improvement of the convergence speed of the blind adaptive algorithm and propose a variable stepsize (VSS) algorithm, which is applicable to blind algorithms. In addition, we suggest the soft-switching concept of the adaptive mode and present a hybrid adaptive algorithm, which combines the blind algorithm and the DD-LMS algorithm, to speed up the operation mode switch of the adaptive algorithm. At final of this part, we discuss several operation strategies of the joint carrier recovery and the DFE. In Part II, the topics of the receiver design in multi-carrier systems, we discuss the issues of the channel estimation and the joint estimation of the Cell-ID and integral CFO in WiMAX system. First, for the synchronization issue in joint estimation of the cell-ID and integral CFO, we derive an optimal detection algorithm according to theoretical derivation. Moreover, from the simplification of the optimal detection algorithm, we suggest the concept of the frequency domain filtering and propose several simple detection algorithms according to the concept. In the topic of the channel estimation, we propose two kinds of the channel estimation algorithms. First, we study the optimization of the estimate mean-square error of the polynomial interpolation. We introduce a window shift concept, derive the optimal window shift, and propose the estimation method of the value under a given interpolation order. Besides, we apply the approximate minimal mean-square error (MMSE) estimator to the channel estimation. In this topic, in order to derive the approximate cross-correlation function in frequency domain, we propose the simple estimation of the root-mean-square delay spread and the mean delay of the channel. We apply the estimators in the channel estimation of the comb-type OFDM and WiMAX systems. In part III, the topic of the transceiver design in wide-band MIMO systems, we address the design of the optimal transmitter and the corresponding receiver. For the coded MIMO OFDM transmission, we insert a space-frequency transform (SFT) to maximize the diversity gain and the coding gain. The transform is realized in a two-step process: the orthogonal transform and then the space-frequency interleaving (SFI). At the receiver, for the design of the channel equalization and demodulation, we adopt the turbo-DFE as the iterative decoding process. In the algorithm realization, we use the frequency domain equalization to reduce the receiver implementation cost and propose the separable SFI design. By this way, the SFI can be moved outside the turbo-DFE loop. In addition, we propose the algorithm of joint channel estimation and the data detection to reduce the utilization of the pilot symbols.