Design Of Multi_core Cable Modem Based On OMAP-L137

With the development of modern industry, the demand for oil is growing. As a non-renewable resource on the planet, the efficiency of oil extraction is getting more attention. As a means for obtaining the physical characteristics of subterranean formation, and thereby inferring the status of oil and gas, the logging technology becomes more mature in petroleum exploration. The logging transmission system, using specific communication method, interacts the ground command data and underground rock data with some signal format. Accurate picture of the underground oil and gas situation, oilfield can be mined in the most reasonable way to maximize oil benefits and improve the efficiency of development.There are several kinds of transmission medium for logging transmission system, such as cable logging transmission, mud logging transmission, drill pipe logging transmission, wireless logging transmission, and optical fiber logging transmission. Due to the long transmission distance, good stability, the cable remains the main means of logging transmission. As the developing of computer technology and Internet technology, network logging technology, advanced hardware and embedded systems technology, and efficient software development technology, have been applied to logging transmission systems. Thus the performance of the system is improved, the complexity is reduced, and system development and testing process become more humane.In this thesis, the multi-core cable logging system is a computerized logging system for the downhole high-temperature environments. The logging system is based on broadband multi-carrier OFDM modulation technique to achieve high-speed transmission. The modem unit in downhole telemetry system, is implemented on the DSP chip OMAP-L137 to meet the high-temperature requirements. The following studies were based around the chip OMAP-L137 in the high-temperature logging system.1. The replacement of modem unit’s implementation platform in downhole logging system. The high-temperature of 175℃ in doenhole limited the use of many device, we chose chip temperature OMAP-L137 to achieve the project targets. We completed the DSP platform replacement, software migration, and system link debugging under existing system architecture.2. The optimization of downhole modem module. The internal resources in OMAP-L137 are not rich, we need to do a lot of work to optimize the chip. The thesis describes the method of the constellation mapping in QAM modulation, and the algorithm optimization of AGC module.3. The optimization of cable system. The thesis uses the algorithm of water filling to improve the transmission rate further, and the total number of bits is increased 9.13%. Thesis optimized the established pattern of system communication to solve the practical problems encountered during logging. In order to reduce the impact of rapidly changing channel on system performance in the course of the actual cable logging, we use a decision feedback equalizer processing the receiving data in Matlab, to lower the bit error rate of the logging system.