TITLE:
OFDM Wireless Downhole Transmission Systems and Proposed SLM Method for PAPR Reduction
AUTHORS:
Renze Luo, Yupu Dang, Rui Li, Jiao Yang
KEYWORDS:
Orthogonal Frequency Division Multiplexing Wireless Downhole Transmission Systems; Orthogonal Frequency Division Multiplexing (OFDM); Logging While Drilling (LWD); Peak-to-Average Power Ratio (PAPR); Selected Mapping (SLM)
JOURNAL NAME:
Communications and Network,
Vol.6 No.1,
January
26,
2014
ABSTRACT: At present, mud pulse
transmission systems are widely used in downhole data transmission. But the
systems are very low in transmission efficiency, only 5-10 bits/s, with very
large anti-inter-symbol-interference (ISI). It cannot meet high requirements
for high-speed transmission of modern logging system. The development of
communication technology has laid some foundation for this requirement. For
this purpose, the Orthogonal Frequency Division Multiplexing (OFDM) Wireless
Downhole Transmission Systems are proposed for the first time because of their
high transmission rate, anti-inter-symbol-interference (ISI), and high spectral
efficiency, etc. Due to non-linear power amplifier (PA) of logging systems with limited
dynamic range, the drawbacks of high peak-average power ratio (PAPR) may
outweigh all the potential benefits of OFDM wireless downhole transmission
systems. Selective mapping (SLM) method can reduce the PAPR of OFDM logging signals without distortion. But at the
receiver, the conventional SLM method needs exact bits of side information (SI)
to recover the data signal. The probability of erroneous SI detection has a
significant influence on the error performance of the system. And individual
transmissions of SI result in the reduction of bandwidth efficiency. To restore
the exact data signal, our scheme codes the SI bits by linear block codes
(LBC), and is easily decoded by syndrome decoding. And then the coding SI bits
are superimposed onto the logging signals to omit SI bits transmission. The
theory and simulation results show that the proposed method has better
performance than the conventional one. Accordingly, the OFDM wireless downhole
transmission systems can tackle the high PAPR problem, and highten the
transmission rate of logging signals.