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Timing recovery by symbol spaced and fractionally spaced equalizers
| Content Provider | Semantic Scholar |
|---|---|
| Author | Rosicky, Martin Maris, J. Vernalde, Serge |
| Copyright Year | 1997 |
| Abstract | This paper presents a study of the digital timing recovery fo high speed QAM receivers based on the symbol spaced and fractionally spaced equalizers (FSE). Th e aim of the investigation is to fix the intersymbol interference (ISI) caused by the clock phase error an d frequency error between the transmitter and the receiver by the complex adaptive equalizer, hereby e liminating the interpolator and the timing error detector (TED). By this approach it is intended to improv e the performance and the cost-effectiveness of the VDSL receiver chip. Both the blind equalization and the adaptation with the use o f the training sequences are discussed. The model of the introduced phase error is described. The infl ue ce of the phase error on the signal to be detected is studied in the time and the frequency domain. During the investigation of the equalizers’ behaviour two b asic operation conditions of the receiver are considered. First, the received signal is corrupted by the constant phas e error. This condition approximates the situation at the beginning of the data transmission. The abilit y of the self recovering algorithms Sato and CMA to set the equalizer’s coefficients such that the decisio n d rected adaptation algorithm (LMS) could be used is studied. The maximal range of the phase error in whi ch t e LMS algorithm is still able to converge, is discussed. The importance of the decimation of the received signal at the correct sample is highlighted and the criterion which optimizes the decimati on is searched for. The optimal length of the equalizer with respect to the other parts of the communication system is discussed. The second state of the operation of the receiver is the track ing mode. In this case the equalizer is considered to be synchronized to the received signal and slow chang es of the phase error are compensated by the LMS algorithm. The evaluation of the equalizer’s coeffic ients during the data transmission is compared with the desired values obtained from the theory. The r easons of the departure from the optimal values are explained. Since the frequency error can cause the growing of the phase e rror out of the range which is acceptable for the LMS algorithm the decimation must be controlled. The algorithm for the regulation of the decimation is the subject of further investigation. All simulations were done in Matlab. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://imecgate.imec.be/vsdm/domains/dbate/1997/rosicky_cwas97.ps |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
