随钻数据声波传输系统利用声波沿钻柱信道传播，实现井下和地面信息准确高效的实时通信。钻柱信道由钻杆和接箍周期性构成，通过理论分析和建模仿真，得到通阻带交替存在的梳状频谱特性，并采用FIR滤波器逼近，建立信道仿真平台。矢量正交频分复用技术(V-OFDM)可以将多径衰落信道分解为多个矢量子信道，通过加入适量的循环前缀，在消除符号间干扰(ISI)的同时，利用分集增益，可以减小由于信道频谱零点造成的误码，增加系统的鲁棒性。仿真和实测结果表明，该方法在满足低误码率的同时，能降低数据冗余，提高传输效率。%Data transmission system of logging while drilling achieves real-time communication between ground and under well accurately and effectively by acoustic wave transmitting along the drillstring. A drillstring channel is periodically constructed by pipes and joints. By theoretical analysis and modeling simulation, the spectrum of drillstring channel is a comb-filtering-like transfer function composed of alternating passed bands and stop bands. A finite impulse response (FIR) filter is used to approximate the spectrum and to build a simulation platform of the channel. Vector orthogonal frequency division multiplexing technology (V-OFDM) can convert the multipath fading channel into a number of vector sub-channels. The number of error bits which are leaded by channel spectral nulls can be reduced and the robustness can be increased by diversity gain when eliminating symbol interference by adding right amount of cyclic prefix. Simulation and test results show that this technology can reduce data redundancy and increase transmission efficiency extremely when meeting the need of low bit error rate.
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