Method and apparatus for iterative timing and carrier recovery

Abstract

Method and apparatus for iterative timing recovery for FTN signaling are provided. The iterative timing recovery method and apparatus uses a feedback timing error signal from a forward error correction block with an additional equalizer prior to a maximum a posteriori (MAP) decoder which matches the equalized FTN signal to a truncated inter-symbol interference (ISI) target. A timing error is then generated using a modified M&M timing error detector.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application Ser. No. 61 / 217,333, entitled “SYSTEM AND METHODS FOR SATELLITE SYSTEMS,” filed May 29, 2009 which is incorporated by reference herein in its entirety.FIELD OF THE INVENTION[0002]The present principles relate to iterative timing recovery in receivers systems.BACKGROUND OF THE INVENTION[0003]Carrier recovery schemes can be classified into two structures: feed-forward structure and feedback structure.[0004]The feedback carrier recovery uses a digital Phase Locked Loop (PLL) to track out the carrier phase and frequency offset. However, it relies on a decision directed or non-data-aided approach to estimate the phase error at each time instant. In decision-directed approach, the decision errors will cause additional self noise while the non-data-aided approach can only apply to a limited number of multiple phase shift keying (MPSK) formats. Further, the feedback carrier recov...

AI Technical Summary

Benefits of technology

A description will now be given of the many attendant advantages and features of the present principles, some of which have been mentioned above. For example, one advantage is a method for iterative timing recovery comprising performing adaptive equalization and maximum likelihood sequence estimation in order to recover symbol timing. Another advantage is an apparatus for iterative timing recovery comprising an comprising adaptive equalizer for performing adaptive equalization and a symbol detector for performing maximum likelihood sequence estimation in order to recover symbol timing. Another advantage is a method for iterative timing recovery comprising filtering an interpolated first error signal using a matched filter, equalizing the filtered interpolated first error signal, detecting a timing error with an M&M timing error detector to produce a second error signal, and using said second error signal to recover the timing of a signal that uses faster-than-Nyquist signaling. Yet another advantage is an apparatus for iterative timing recovery comprising a matched filter for filtering an interpolated first error signal using a matched filter, an equalizer for equalizing the filtered interpolated first error signal, a timing error detector for detecting a timing error with an M&M timing error detector to produce a second error signal, and a recovery circuit for using said second error signal to recover the timing of a signal that uses faster-than-Nyquist signaling.

Problems solved by technology

However, it relies on a decision directed or non-data-aided approach to estimate the phase error at each time instant.

In decision-directed approach, the decision errors will cause additional self noise while the non-data-aided approach can only apply to a limited number of multiple phase shift keying (MPSK) formats.

Further, the feedback carrier recovery scheme could be disturbed by cycle slips which may cause a large number of errors due to phase ambiguity.

This reduces the bandwidth efficiency since no data is transmitted during a pilot or sync interval.

The second disadvantage of the feed-forward carrier recovery is the inability to recover large frequency offsets or phase variations due to phase noise between the measurement blocks.

Timing recovery in FTN signaling becomes a huge challenge due to strong ISI effects when the symbols period is squeezed to get higher bandwidth efficiency.

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