共查询到20条相似文献,搜索用时 15 毫秒
1.
A novel symbol-timing recovery scheme is presented that is insensitive to carrier-phase error and is not susceptible to hangup at large values of timing error as is the case for the conventional two-point non-data aided (2p-NDA) scheme. The new scheme is applicable for symbol-timing recovery for M-ary PSK modulation formats.<> 相似文献
2.
Yik-Chung Wu Tung-Sang Ng 《Communications Letters, IEEE》2001,5(5):221-223
A new all-digital symbol timing estimator for GMSK signals is proposed. It is based on the squaring algorithm and has a feedforward structure. Performance in AWGN channel is assessed by computer simulation, and is compared with the modified Cramer-Rao bound and other existing algorithms. The performance of the proposed estimator is shown to be close to that of the ML algorithm 相似文献
3.
This paper provides a framework for analyzing and comparing timing recovery schemes for higher order partial response (PR) channels. Several classes of timing recovery schemes are analyzed. Timing recovery loops employing timing gradients or phase detectors derived from the minimum mean-square error (MMSE) criterion, the maximum likelihood (ML) criterion, and the timing function approach of Mueller and Muller (1976) (MRI) are analyzed and compared. The paper formulates and analyzes MMSE timing recovery in the context of a slope look-up table (SLT), which is amenable for an efficient implementation. The properties and performance of the SLT-based timing loop are compared with the ML and MM loops. Analysis and time step simulations for a practical 16-state PR magnetic recording channel show that the output noise jitter of the ML phase detector is worse than that of the SLT-based phase detector. This is primarily due to the presence of self-noise in the ML detector. Consequently, the SLT-based phase detector is to be preferred. In comparing the SLT and MM based timing loops, it is found that both schemes have similar jitter performance 相似文献
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5.
《Communications, IEEE Transactions on》1993,41(4):544-549
A general analysis is presented for the jitter performance of a common symbol timing recovery (STR) system used in a digital subscriber loop (DSL) transceiver that uses adaptive echo cancellation for high-speed digital communications. Exact analytical expressions for the mean and variance of the timing wave and for the RMS phase jitter are derived as a function of the bandwidth of the postfilter for a given set of input parameters representing a particular digital subscriber loop and its noise environment, including such effects as residual echo and crosstalk. Numerical results show that the presence of these disturbing signals can substantially degrade the STR performance. The effect of the excess bandwidth factor of the prefilter on this degradation is investigated 相似文献
6.
Symbol timing estimation with CPM modulation 总被引:1,自引:0,他引:1
Symbol timing in continuous phase modulated signals is investigated making use of maximum likelihood estimation methods. Nondata-aided algorithms are proposed with a feedforward structure. They are suitable for digital implementation and can be employed with either full or partial response signaling. Multilevel symbol alphabets are allowed and the modulation index may be arbitrary. The performance is assessed by analysis and simulation. It turns out that full response schemes are comparatively easier to synchronize. Difficulties arise with partial response signaling especially with long frequency pulses 相似文献
7.
Barry J.R. Kavcic A. LcLaughlin S.W. Nayak A. Wei Zeng 《Signal Processing Magazine, IEEE》2004,21(1):89-102
The last decade has seen the development of iteratively decodable error-control codes of unprecedented power, whose large coding gains enable reliable communication at very low signal-to-noise ratio (SNR). A by-product of this trend is that timing recovery must be performed at an SNR lower than ever before. Conventional timing recovery ignores the presence or error-control coding and thus doomed to fail when the SNR is low enough. This article describes the iterative timing recovery, a method for implementing timing recovery in cooperation with iterative error-control decoding so as to approximate a more complicated receiver that jointly solves the timing recovery and decoding problems. 相似文献
8.
Digital filter and square timing recovery 总被引:4,自引:0,他引:4
The digital realization of timing recovery circuits for digital data transmission is considered. A digital algorithm is proposed that can be implemented very efficiently even at high data rates. The resulting timing jitter has been computed and verified by simulations. In contrast to other known algorithms, the one presented here allows free-running sampling oscillators and a novel planar filtering method that prevents synchronization hangups 相似文献
9.
The effects of hangup in digital asynchronous timing recovery loops are investigated. It is demonstrated that delay quantisation in the interpolation filter exacerbates the problem of hangup. It is also noted that the effects of hangup are worse for the non-data aided (NDA) loops than they are for the decision-directed (DD) loops. This may preclude the use of the former in TDMA applications.<> 相似文献
10.
IEEE 802.11n无线局域网标准为了避免不必要的波束成型采用了循环移位机制,该机制对符号同步造成障碍,使得符号同步产生所谓的假多径问题。针对这个问题,本文提出了一种采用移位叠加的本地训练序列互相关的同步方法。通过对IEEE 802.11n无线局域网系统进行建模仿真,对新提出的方法和前人所提出的方法进行比较。最终验证该同步方法具有实用性,能够大幅度的提升同步的精度,使得符号同步的定位误差控制在2个采样点之内。 相似文献
11.
We describe a simple, new timing recovery technique in which an antiparallel diode pair is used to detect the phase difference between a data stream and a locally generated timing wave. Our 274 Mbit/s demonstration circuit provides dependable synchronisation even when the input signal/noise ratio is only 6 dB. 相似文献
12.
Trellis coded multi-h CPM schemes have been shown in the literature to have attractive power-bandwidth performance at the expense of increased receiver complexity. In this Letter, a combined trellis coding with self-synchronous multi-h CPM technique is described which eliminates the need for the multi-h synchronisation overhead and maximises the minimum distance. In this method, the multi-h pattern is made to be associated with the encoder state transitions and repeated rather than cyclically changed in time for successive symbol intervals, resulting in a simpler receiver with better performance 相似文献
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Dengwei Fu Willson A.N. Jr. 《IEEE transactions on circuits and systems. I, Regular papers》2005,52(2):338-349
In an all-digital timing-adjustment system for digital modems, interpolation can be employed to recover samples that are synchronous with the data symbols. In this paper, a novel interpolation method is described for such systems. Instead of approximating a continuous-time signal with a conventional (algebraic) polynomial and computing the synchronized samples using a Farrow structure, a trigonometric polynomial is employed. It is demonstrated that this approach produces a particularly simple implementation structure, reduces computational delay and, for practical signals, can improve the interpolation performance. Moreover, to recover a synchronized sample from existing samples, given a timing offset, it is shown that the method can be optimized such that a recovered sample's interpolation error is minimized for that specific timing offset value. The input signal's spectrum is also taken into account. Simulation results indicate that the method can achieve the best performance among all state-of-the-art methods tested. In addition, the optimal interpolator can be implemented without increased hardware requirements. 相似文献
15.
In this paper we revisit the early-late timing recovery scheme developed for filter bank based multicarrier transmission. A substantial improvement is proposed for the case where the receiver contains a decision-feedback equalizer. We show how the timing error detector has to be modified to account for the high level of self-noise and how this self-noise can be mitigated thanks to the introduction of a correction term. We investigate the tracking performance of this new synchronizer for high bit rate transmission over copper wires. 相似文献
16.
Bergmans J.W.M. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1995,41(5):1397-1408
This paper assesses the tracking capabilities of data-aided timing recovery schemes in terms of an efficiency that characterizes, coarsely speaking, the amount of timing information that the scheme manages to extract from the incoming signal per unit of time and signal-to-noise ratio. Efficiencies of maximum-likelihood and various baud-rate timing recovery schemes are determined as a function of the data and channel parameters, and are optimized with respect to design freedoms of the schemes. These results are illustrated for partial-response channels and idealized digital recording channels 相似文献
17.
Two novel trellis-coding techniques, called nonlinear multi-h signaling and nonlinear asymmetrical multi-h signaling, which achieve higher constraint length than ordinary multi-h signals, are introduced with CPFSK signals. In contrast to ordinary multi-h signaling where the modulation index is changed at the end of every symbol interval, nonlinear multi-h signals are constructed by changing the modulation index based on the previous symbol, and the current symbol interval. A class of nonlinear asymmetrical multi-h signals, which change the modulation index based on the current symbol too, is then constructed by extending nonlinear multi-h signals and combining them with asymmetrical multi-h signals. Binary full-response nonlinear multi-h and nonlinear asymmetrical multi-h CPFSK signals are constructed and analyzed. Minimum Euclidean distances and spectral properties of these signals are calculated at different phase states and various selected modulation index patterns. Numerical results indicate that nonlinear multi-h and nonlinear asymmetrical multi-h signals achieve significantly higher distance than other existing multi-h formats reported in the literature 相似文献
18.
Joint phase and timing recovery for MSK-type signals 总被引:1,自引:0,他引:1
Novel nondata-aided algorithms are proposed for joint estimation of timing and carrier phase in minimum-shift keying (MSK)-type modulations. The performance with MSK and Gaussian MSK is assessed by computer simulations and compared with that of other existing estimation schemes 相似文献
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We investigate a novel nondata-aided method for jointly estimating timing and carrier frequency offset in MSK-type modulation. The algorithm has a feedforward structure and lends itself to a simple digital implementation. Its estimation accuracy depends on a design parameter that may be varied to trade performance for computational complexity. Setting the parameter to unity yields a synchronization scheme already known in the literature. Computer simulations are used to assess the synchronizer performance on AWGN Rayleigh fading channels with MSK and Gaussian MSK modulation 相似文献