Invention Grant
- Patent Title: Symbol synchronization for downhole OFDM telemetry
- Patent Title (中): 井下OFDM遥测的符号同步
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Application No.: US12193525Application Date: 2008-08-18
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Publication No.: US08749400B2Publication Date: 2014-06-10
- Inventor: Carl A. Robbins
- Applicant: Carl A. Robbins
- Applicant Address: US TX Houston
- Assignee: Halliburton Energy Services, Inc.
- Current Assignee: Halliburton Energy Services, Inc.
- Current Assignee Address: US TX Houston
- Agency: Krueger Iselin LLP
- Agent Bradley A. Misley
- Main IPC: H04L27/28
- IPC: H04L27/28

Abstract:
Enhanced symbol synchronization methods suitable for use in narrowband orthogonal frequency division multiplexed (OFDM) telemetry systems. In at least some embodiments, a logging while drilling (LWD) tool assembly communicates with the surface using low frequency electromagnetic (EM) signals. The telemetry transmitter employs OFDM modulation to fully exploit the narrow range of available bandwidth, resulting in signals that have relatively long frames. At the surface a receiver digitizes the receive signal and applies an enhanced symbol synchronization technique to identify frame boundaries before demodulation is attempted. The enhanced symbol synchronization technique employs a pulse train filter to clean up a cyclic prefix correlation signal that otherwise behaves badly in the narrowband regime. The improved timing information from the enhanced symbol synchronization significantly reduces the error rate in the demodulated signal.
Public/Granted literature
- US20100039286A1 Symbol Synchronization for Downhole OFDM Telemetry Public/Granted day:2010-02-18
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