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Iterative timing recovery for magnetic recording channels with low signal-to-noise ratio.

机译：具有低信噪比的磁记录通道的迭代定时恢复。

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摘要

Digital communication systems invariably employ an underlying analog communication channel. At the transmitter, data is modulated to obtain an analog waveform which is input to the channel. At the receiver, the output of the channel needs to be mapped back into the discrete domain. To this effect, the continuous-time received waveform is sampled at instants chosen by the timing recovery block. Therefore, timing recovery is an essential component of digital communication systems.; A widely used timing recovery method is based on a phase-locked loop (PLL), which updates its timing estimates based on a decision-directed device. Timing recovery performance is a strong function of the reliability of decisions, and hence, of the channel signal-to-noise ratio (SNR). Iteratively decodable error-control codes (ECCs) like turbo codes and LDPC codes allow operation at SNRs lower than ever before, thus exacerbating timing recovery.; We propose iterative timing recovery, where the timing recovery block, the equalizer and the ECC decoder exchange information, giving the timing recovery block access to decisions that are much more reliable than the instantaneous ones. This provides significant SNR gains at a marginal complexity penalty over a conventional turbo equalizer where the equalizer and the ECC decoder exchange information. We also derive the Cramer-Rao bound, which is a lower bound on the estimation error variance of any timing estimator, and propose timing recovery methods that outperform the conventional PLL and achieve the CramEr-Rao bound in some cases.; At low SNR, timing recovery suffers from cycle slips, where the receiver drops or adds one or more symbols, and consequently, almost always the ECC decoder fails to decode. Iterative timing recovery has the ability to corrects cycle slips. To reduce the number of iterations, we propose cycle slip detection and correction methods. With iterative timing recovery, the PLL with cycle slip detection and correction recovers most of the SNR loss of the conventional receiver that separates timing recovery and turbo equalization.
机译：数字通信系统始终采用底层的模拟通信通道。在发射机处，数据被调制以获得输入到通道的模拟波形。在接收器上，通道的输出需要映射回离散域。为此，在定时恢复模块选择的瞬间对连续时间接收的波形进行采样。因此，定时恢复是数字通信系统的重要组成部分。广泛使用的时序恢复方法基于锁相环（PLL），该锁相环基于决策导向的设备更新其时序估计。定时恢复性能是决策可靠性的重要函数，因此也是信道信噪比（SNR）的重要函数。像Turbo码和LDPC码这样的可迭代解码的错误控制码（ECC）允许以比以往更低的SNR操作，从而加剧了时序恢复。我们提出了迭代定时恢复，其中定时恢复块，均衡器和ECC解码器交换信息，使定时恢复块可以访问比瞬时决策更可靠的决策。与传统的turbo均衡器（均衡器和ECC解码器交换信息）相比，这在边际复杂性代价上提供了显着的SNR增益。我们还推导了Cramer-Rao界，这是任何时序估计器的估计误差方差的下限，并提出了在某些情况下优于传统PLL并达到CramEr-Rao界的时序恢复方法。在低SNR的情况下，时序恢复会遭受周期滑移的影响，在周期滑移中，接收机会丢弃或添加一个或多个符号，因此，几乎总是ECC解码器无法解码。迭代定时恢复具有纠正周期转差的能力。为了减少迭代次数，我们提出了循环转差检测和校正方法。通过迭代定时恢复，具有周期滑动检测和校正功能的PLL可以恢复传统接收机的大部分SNR损耗，而传统的接收机将定时恢复和Turbo均衡分开。

著录项

  • 作者

    Nayak, Aravind R.;

  • 作者单位

    Georgia Institute of Technology.;

  • 授予单位 Georgia Institute of Technology.;
  • 学科 Engineering Electronics and Electrical.
  • 学位 Ph.D.
  • 年度 2004
  • 页码 179 p.
  • 总页数 179
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 无线电电子学、电信技术;
  • 关键词

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