Performance Of Timing Recovery Research Articles

Performance Analysis of Code-Aided Symbol Timing Recovery on AWGN Channels

We analyze the performance of a code-aided (CA) decision-directed (DD) timing synchronizer, which can exploit the dependence structure across coded symbols to improve the timing recovery accuracy. Due to the inherent coupling between timing recovery and decoding, most existing studies rely on extensive simulation rather than on analytical methods to evaluate performance of timing recovery for coded systems. We propose analytical methods in this paper towards this end. A first key step is to approximate timing-offset-induced inter-symbol interference (ISI) as an additive Gaussian noise, since in the low signal-to-noise ratio (SNR) regime the background noise is large enough to mask the ISI. Then, we derive semi-analytical expressions for the mean and variance of extrinsic information as functions of timing offset, building on which we characterize both open-loop and closed-loop performance of decision-directed timing synchronizers. Monte Carlo simulation results corroborate that the proposed method accurately characterizes the performance of CA DD timing recovery, for systems with a wide range of channel bandwidth and different channel codes.

Timing recovery in data storage systems: framework and approach of Kalman filtering

Recent error correction coding is able to work with low Signal-to-Noise Ratios (SNR), thus increasing the recording densities in data storage systems. With low SNR, conventional timing recovery is likely to lose stability and entire blocks of data may be lost. Reliable timing recovery is required in low SNR to reduce the loss of lock rate. In this paper, we introduce the framework of current timing recovery system, challenges of timing recovery in low SNR, and application of Kalman filtering to timing recovery. With Kalman filtering, timing recovery performance is improved in acquisition, tracking, and dropout compensation, and loss of lock rate is reduced.

TMTR Codes for Partial Response Channels

A TMTR code is specified as (k evne 1 = 2, k odd 1 = 3, k) constraint. In this work, an approach for constructing (k even 1 = 2, k odd 1 = 3, k) codes is presented. Based on this construction, a rate 8/9 code with k=7 is found. This code can achieve better timing recovery performance compared to the proposed previously TMTR code with k= 11. An enumerating encoder and decoder exist for constructed (k even 1 = 2, k odd 1 = 3, k) codes. A look-up table for the encoder/decoder is not required. Simulation results on an E 2 PRIV recording channel reveal that the TMTR code provides 2.2 dB gain over an uncoded case.

Blind equalization for short burst wireless communications

In this paper, we propose a dual mode blind equalizer based on the constant modulus algorithm (CMA). The blind equalizer is devised for short burst transmission formats used in many current wireless TDMA systems as well as future wireless packet data systems. Blind equalization is useful for such short burst formats, since the overhead associated with training can be significant when only a small number of bits are transmitted at a time. The proposed equalizer overcomes the common problems associated with classic blind algorithms, i.e., slow convergence and ill-convergence, which are detrimental to applying blind equalization to short burst formats. Thus, it can eliminate the overhead associated with training sequences. Also, the blind equalizer is extended to a two branch diversity combining blind equalizer. A new initialization for fractionally spaced CMA equalizers is introduced. This greatly improves the symbol timing recovery performance of fractionally spaced CMA equalizers with or without diversity, when applied to short bursts. Through simulations with quasi-static or time-varying frequency selective wireless channels, the performance of the proposed equalizer is compared to selection diversity and conventional equalizers with training sequences. The results indicate that its performance is far superior to that of selection diversity alone and comparable to the performance of equalizers with short training sequences. Thus, training overhead can be removed with no performance degradation for fast time-varying channels, and with slight performance degradation for static channels.

Measurements on the timing recovery performance of partial-response class-4 signalling

The timing recovery performance of partial-response class-4 signalling is experimentally determined as a function of transmit filter bandwidth, transmit filter rolloff and tuned circuit misalignment in the timing recovery circuit of a baseband transmission system operating at the ISDN basic access rate. The implications for echo cancellation are briefly discussed and some general properties of partial-response class 4 signalling are presented.