New PPM Coding with Protection Time Slots for Optimizing the Drilling Fluid Pulse Signal for High Energy Efficiency
In order to improve the transmission rate of downhole data and increase battery life and the frequency of drilling fluid pulser action, it is necessary to study and select the drilling fluid pulse signal coding method with high coding efficiency and energy saving efficiency. The coding efficiency and energy saving efficiency of multi-pulse position modulation(MPPM)and differential pulse position modulation(DPPM) with different number of protection time slot are calculated by high efficient pulse position modulation coding(PPM) methods. By comparing the calculation results of MPPM and DPPM, it is found that the coding efficiency of MPPM increases with the number of information and DPPM has the fixed information digits number to implement combinatorial coding. In the case that the number of bits of information to be encoded is small, DPPM has fewer bits of information to be encoded, and its encoding and decoding algorithms are easier to implement. Further, it has higher encoding and power saving efficiency. When the number of protection time slot is 2, the coding efficiency of DPPM can reach 46. 2% and the energy saving efficiency can reach 84. 6%. The research results show that DPPM coding with a protection time slot has high coding and energy saving efficiency, as its coding mapping method is simpler. It is an efficient coding method suitable for applying to the drilling fluid pulse signal.
AAPG Datapages/Search and Discovery Article #130005© Petroleum Drilling Techniques, Issue 6, 2018