Efficient Encoding Method for Combined Codes in the MWD Telemetry System

Abstract

MPPM (Multipulse Position Modulation) is a pulse code technology that is widely used in optical communication and deep space communication due to its high energy efficiency. Combination code is a variation of MPPM and is widely used in MWD (Measurement While Drilling) telemetry systems. However, whether it is MPPM or combination code, it is difficult to establish a simple mapping relationship between bit symbols and pulse symbols. Therefore, an encoding table is usually used to realize the mapping between bit symbols and pulse symbols. With an increase in bit width, the storage complexity of the encoding table increases exponentially. This is unacceptable for underground transmitters working in harsh environments. This paper maps the code symbols of MPPM to a hyper-triangular region of a high-dimensional tensor and establishes a simple lookup table and lookup algorithm to achieve low-complexity mapping from bit symbols to MPPM code symbols. At the same time, this paper also provides a method for extending from MPPM code symbols to commonly used combination code symbols in MWD, thereby providing an efficient implementation path for large bit width combination code encoding at the underground end of MWD.