At present,the MWD systems continuous wave mud pulse telemetry transmit is not faster than 1or 2bits/s from deep wells containing highly attenuative mud,because positive pulsers create strong signals but large axial f...At present,the MWD systems continuous wave mud pulse telemetry transmit is not faster than 1or 2bits/s from deep wells containing highly attenuative mud,because positive pulsers create strong signals but large axial flow forces impede fast reciprocation while mud sirens provide high data rates without higher signal strength.A high-data-rate system providing 10bits/s and operable up to30 000 ft is described,which creates strong source signals by using downhole constructive wave interference in two novel ways.Telemetry schemes,frequencies and pulser locations in the MWD drill collar are selected for positive wave phasing,and sirens-in-series are used to create additive signals——both without incurring power and erosion penalties.The positions normally occupied by pulsers and turbines are reversed to minimize times required for constructive interference and modulation.A system design approach is undertaken,e.g.,strong source signals are augmented with new multiple-transducer surface signal processing methods to remove mudpump noise and signal reflections at both pump and desurger,and mud,bottomhole assembly and drill pipe properties,to the extent possible in practice,are controlled to reduce signal attenuation.The results of detailed acoustic modeling in realistic drilling telemetry channels are described,and short and long wind tunnels for signal strength,torque,erosion and jamming testing,and telemetry and signal processing evaluation,respectively,are introduced.Special scaling methods are developed to extrapolate cost-effective wind tunnel test results to real muds flowing at any downhole speed.New siren concept prototype hardware and also typical acoustic test results are also given.展开更多
It has been demonstrated that either Channel Allocation （CA） or Relay Selection （RS） can improve the performance in relaying networks separately. However, there is little work concerning their combination in multi...It has been demonstrated that either Channel Allocation （CA） or Relay Selection （RS） can improve the performance in relaying networks separately. However, there is little work concerning their combination in multi-cell uplink scenarios. In this paper, we investigate the issue which considers the CA and RS to optimize the system transmission rate in an uplink scenario, while maintaining the resource distribution fairness among users. This is first formulated as an optimization problem for a linear cellular system, where the same frequency channels can be reused in different cells. Based on the link and co-channel interference conditions, two low-complexity CA and RS schemes are then proposed with different decomposition se quences. Finally, numerical results are con ducted to verify the effectiveness of the pro posed CA and RS methods. Simulations re suits show that the proposed methods can yield significant improvements in system per formance in terms of average sum rate.展开更多
文摘At present,the MWD systems continuous wave mud pulse telemetry transmit is not faster than 1or 2bits/s from deep wells containing highly attenuative mud,because positive pulsers create strong signals but large axial flow forces impede fast reciprocation while mud sirens provide high data rates without higher signal strength.A high-data-rate system providing 10bits/s and operable up to30 000 ft is described,which creates strong source signals by using downhole constructive wave interference in two novel ways.Telemetry schemes,frequencies and pulser locations in the MWD drill collar are selected for positive wave phasing,and sirens-in-series are used to create additive signals——both without incurring power and erosion penalties.The positions normally occupied by pulsers and turbines are reversed to minimize times required for constructive interference and modulation.A system design approach is undertaken,e.g.,strong source signals are augmented with new multiple-transducer surface signal processing methods to remove mudpump noise and signal reflections at both pump and desurger,and mud,bottomhole assembly and drill pipe properties,to the extent possible in practice,are controlled to reduce signal attenuation.The results of detailed acoustic modeling in realistic drilling telemetry channels are described,and short and long wind tunnels for signal strength,torque,erosion and jamming testing,and telemetry and signal processing evaluation,respectively,are introduced.Special scaling methods are developed to extrapolate cost-effective wind tunnel test results to real muds flowing at any downhole speed.New siren concept prototype hardware and also typical acoustic test results are also given.
基金supported by the Key Project of State Key Laboratory of Rail Traffic and Control under Grant No.RCS2012ZZ004the Fundamental Research Funds for the Central Universities under Grant No. 2013YJS025
文摘It has been demonstrated that either Channel Allocation （CA） or Relay Selection （RS） can improve the performance in relaying networks separately. However, there is little work concerning their combination in multi-cell uplink scenarios. In this paper, we investigate the issue which considers the CA and RS to optimize the system transmission rate in an uplink scenario, while maintaining the resource distribution fairness among users. This is first formulated as an optimization problem for a linear cellular system, where the same frequency channels can be reused in different cells. Based on the link and co-channel interference conditions, two low-complexity CA and RS schemes are then proposed with different decomposition se quences. Finally, numerical results are con ducted to verify the effectiveness of the pro posed CA and RS methods. Simulations re suits show that the proposed methods can yield significant improvements in system per formance in terms of average sum rate.
