Analysis of OFDM modulation method and experiment for acoustic transmission system along drill strings

WANG Qiang1， LI Cheng2， DING Tian-huai1
（1. Department of Precision Instruments and Mechanology， Tsinghua University， Beijing 100084 ，China;
2. School of Instrumentation Science and Opto-Electronics Engineering， Beihang University， Beijing 100191， China）

Abstract：In order to improve the data transfer rate of logging while drilling（LWD），an acoustic transmission scheme based on orthogonal frequency division multiplexing （OFDM） multi-carrier modulation was proposed，at the angle of data communication，with considering the time dispersions and multiple echoes because of the periodic channel boundaries. The platform of acoustic transmission along the drill pipe was designed and built under the PC processing with interface of an FPGA breadboard and a data acquisition card. Experimental results show that the acoustic transmission scheme along the short drill pipe based on OFDM modulation technology has a reliable transmission of 160 bit/s transfer rate. Moreover，it provides a reasonable guidance for follow-up design and experiment research of acoustic transmission.
Key words： logging while drilling（LWD）；orthogonal frequency division multiplexing （OFDM） modulation；digital equalization; timing and frequency synchronization；acoustic transmission；drill string