EP3594445A1 - Bohrlochkabelkommunikation - Google Patents

Bohrlochkabelkommunikation Download PDF

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Publication number
EP3594445A1
EP3594445A1 EP18183529.9A EP18183529A EP3594445A1 EP 3594445 A1 EP3594445 A1 EP 3594445A1 EP 18183529 A EP18183529 A EP 18183529A EP 3594445 A1 EP3594445 A1 EP 3594445A1
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EP
European Patent Office
Prior art keywords
wireline
characterisation
signal
single tone
bitrate
Prior art date
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Withdrawn
Application number
EP18183529.9A
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English (en)
French (fr)
Inventor
Carsten NESGAARD
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Welltec AS
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Welltec AS
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Publication date
Application filed by Welltec AS filed Critical Welltec AS
Priority to EP18183529.9A priority Critical patent/EP3594445A1/de
Priority to US16/510,001 priority patent/US20200018155A1/en
Priority to PCT/EP2019/068825 priority patent/WO2020011979A1/en
Publication of EP3594445A1 publication Critical patent/EP3594445A1/de
Withdrawn legal-status Critical Current

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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00—Survey of boreholes or wells
    • E21B47/12—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00—Survey of boreholes or wells
    • E21B47/01—Devices for supporting measuring instruments on drill bits, pipes, rods or wirelines; Protecting measuring instruments in boreholes against heat, shock, pressure or the like

Definitions

  • the present invention relates to a downhole wireline communication system in general and in particular to a high reliability downhole wireline communication system for high speed communication with downhole equipment, sensors and devices.
  • Downhole operations normally require tools to be inserted in the downhole environment, which tools are typically controlled from the surface.
  • a wired control interface is used, i.e. wireline communication.
  • This interface is used for sending and receiving control commands and also to receive sensor data keeping track of the changing conditions downhole.
  • the distance from an uphole command center to a downhole tool can be measured in kilometres which means that an extremely long wire needs to be used for the interface.
  • the ever changing environment downhole makes it essential to have full control of the downhole tool.
  • the communication between the uphole command center and the downhole tool has to be reliable and bit-errors and lost data packets must be kept at a minimum.
  • the downhole tool may be equipped with high resolution thermal imaging and high bitrates will be necessary in order to transfer these images or streams of images to the uphole command center.
  • An object of the present invention is to provide a new type of method for downhole data communication which is improved over prior art and which eliminates or at least mitigates some of the drawbacks discussed above. More specifically, an object of the invention is to provide a wireline data communication system that is capable of optimising data transfer and to automatically adjust the bitrate.
  • a method for downhole data communication in a downhole communication system performed by a communication equipment configured to be arranged to transmit and receive signals via an associated wireline at a bitrate comprises the steps of determining, at one or more frequencies, one or more characteristics of the wireline associated with each of the one or more frequencies, and adjusting the bitrate based on the determined one or more characteristics.
  • One advantage of this method is that is allows for the bitrate to be adjusted to the characteristics of the wireline and consequently adapt the performance of the communication system to a desired level of speed and reliability.
  • the method further comprises the step of estimating, from the one or more characteristics, a wireline frequency response function associated with each of the one or more frequencies.
  • the step of adjusting the bitrate is further based on the estimated wireline frequency response function.
  • the step of adjusting comprises comparing the estimated wireline frequency response function with a first threshold and a second threshold. If the estimated wireline frequency response function is above the first threshold, increase the bitrate, and if it is below the second threshold, decrease the bitrate.
  • One benefit of having these limits is that the bitrate may be controlled in any number of steps.
  • the step of adjusting comprises comparing each of the values of the estimated wireline frequency response function with a third threshold. For each value below the third threshold, bar the frequencies being associated with such values from use. This has the advantage that it is possible to avoid using bad frequencies that may reduce the system performance.
  • the one or more characteristics of the wireline comprise a loss of characteristic. This has at least the benefit of allowing the adjustment of the bitrate as a function of the loss of the wireline.
  • One embodiment of the method comprises the step of determining transmitting and/or receiving at least one single tone characterisation signal. In doing this, it is possible to dynamically evaluate the characteristics of the wireline.
  • each single tone characterisation signal having different frequency and/or amplitude.
  • Using more than one single tone characterisation signal enables the characterisation of the wireline across a number of different frequencies and/or amplitudes.
  • the method is in one embodiment presented with the step of determining comprising receiving one or more single tone characterisation signal(s).
  • the step of estimating comprises comparing the one or more received single tone characterisation signals to a reference characterisation signal. Using more than one single tone characterisation signal enables the characterisation of the wireline across a number of different frequencies and/or amplitudes and the comparison to a reference enables evaluation of wireline effect on the single tone characterisation signal.
  • the one or more single tone characterisation signals are more than one single tone characterisation signal.
  • the single tone characterisation signal spaced in frequency between 1Hz and 10Mhz, preferably between 10Hz and 1MHz.
  • One embodiment presents the method as comprising, after the step of estimating, a step of shaping the signal.
  • the step of shaping comprises calculating and applying one or more shaping parameters.
  • One benefit of shaping the signal is that a received shaped signal will have substantially the same behaviour as the signal sent before it was shaped for the shaped parameters.
  • the method is initiated by the detection a characterisation trigger.
  • a characterisation trigger One benefit is that this enables the restarting and rerunning of the process responsively to the characterisation trigger.
  • the characterisation trigger comprises the detection of start up of the wireline transceiver.
  • One benefit of this embodiment is that it ensures a characterised wireline and desired bitrate at each start up.
  • the characterisation trigger comprises detecting a change in one or more environmental parameters. This is beneficial since it allows automatic rerunning of the method on changes in environmental parameters.
  • the one or more environmental parameters comprise(s) any or all of temperature, acidic concentration, air pressure, humidity and cable changes. This enables adaptive and automatic adjustment of the bitrate as the environmental conditions change.
  • a downhole data communication system comprising at least one communication equipment configured to perform the method according to any embodiment of the method.
  • a communication equipment configured to be arranged to perform the method according to any embodiments of the method is presented.
  • the word symbol is used to describe any communications symbol comprising one or more bits.
  • a system using BPSK or 2-GFSK modulation one symbol would equal one bit.
  • a system using QPSK one symbol equals two bits and so on. This means that symbol and bit may be used interchangeably with associated terms such as symbol-rate and bitrate.
  • Fig. 1 shows a downhole system 100 comprising a downhole tool 110 being inserted into a well tubular structure 120.
  • the well tubular structure 120 is arranged for producing hydrocarbon-containing fluid from a reservoir 130.
  • the downhole system 100 comprises one or more sensors 140 that may be placed both outside the well tubular structure 120, or be comprised in the downhole tool 110.
  • the downhole tool 110 is attached to a wireline 150 that comprises cables for communication, power cables, fastening cables etc.
  • the downhole tool 110 is provided with a wireline communication equipment 210 to form part of a downhole communications system 200, as will be explained in the following description.
  • Fig. 1b reveals, schematically (and not to scale), a downhole operation system for operating the downhole tool 110.
  • the wireline 150 is attached to the downhole tool 110 and runs to a lowering means 170 located on a rig or vessel 160.
  • the wireline 150 is arranged such that it enables communication and control between a surface data acquisition system 180 and the downhole tool 110.
  • the wireline 150 will be provided from a spool and will unspool as the downhole tool 110 is lowered into the well tubular structure 120 and re-spooled as it is raised.
  • a downhole communication system 200 comprises at least one wireline communication equipment 210 in communication over a wireline 150.
  • the downhole communication system 200 comprises at least one wireline communication equipment 210 in communication over a wireline 150.
  • wireline communication equipment 210 For clarification, normal use would entail at least two wireline communication equipment 210, one comprised in or at the downhole tool 110, and the other comprised in e.g. the surface data acquisition system 180.
  • the system 200 may run with only one wireline communication equipment 210, this will be further elaborated in the following sections.
  • the wireline 150 is not ideal and will consequently distort a data signal f(t) sent over the wireline 150. Distortion may occur e.g.
  • the wireline 150 is typically provided on a spool making it equivalent of a large coil. This means that the inductive effects, i.e. high frequency loss, will be most significant when the cable is spooled. This is considered the worst case, from an inductance standpoint, since the wireline 150 only gets better as it is unspooled.
  • FIG. 3 a schematic view of one example of a wireline communication equipment 210 for downhole wireline communication is shown.
  • the wireline communication equipment 210 comprises a wireline transceiver 320 and a controller 310.
  • the wireline communication equipment 210 is connected to the at least part of the wireline 150.
  • the controller 310 is adapted to be arranged to control the transceiver 320 such that the wireline communication equipment 210 may send and receive data packets across the wireline 150.
  • the skilled person is well aware that the schematic view presented in Fig. 3 does not fully convey a working wireline communication equipment 210. Details such as power supply, memory, various interfaces etc. are left uncommented as they are well known in the art.
  • the wireline 150 is not ideal but will affect the data signals f(t) transmitted through the wireline 150. This affect can be described with a wireline transfer function h(t) that describes how the wireline affect the data signal f(t).
  • Fig. 4a shows an example of a data signal f(t) transmitted by the wireline communication equipment 210.
  • the signal f(t) is subjected to the transfer function h(t), i.e. transmitted through the wireline 150, and a distorted signal h(f(t)) is received by another wireline communication equipment 210.
  • the distortion i.e. the transfer function h(t) of the wireline 150
  • the distortion is manifested as low pass filtering and attenuation.
  • Fig. 4b wherein the distorted signal h(f(t)) is manifested with an oscillating amplitude indicative of a LC load in the wireline 150.
  • Fig. 4c another example of a distorted signal h(f(t)) is shown, visualising a rise time T R , a fall time T F and a time per symbol T S . From Fig 4c , it can be seen that if the rise time T R or the fall time T F becomes a significant part of the time per symbol T S , the amplitude of the distorted signal h(f(t)) will drop rapidly to a point where it will not be possible to decode the distorted signal h(f(t)). The possibility to decode the distorted signal is also dependent on noise in the system, typically Additive White Gaussian Noise, AWGN.
  • noise in the system typically Additive White Gaussian Noise
  • BER Bit Error Rate
  • the BER is a function of noise and Energy per Symbol E S .
  • the energy of the distorted signal h(f(t)) is integrated function h(f(t)) over the time per symbol T S , i.e. the area of the distorted signal h(f(t)).
  • the data signal f(t) is shown in the same diagram as the distorted signal h(f(t)). From the data given in Fig. 5 , it would be possible to generate a compensation as the difference between the data signal f(t) and the known received distorted signal h(f(t)). However, doing these compensations in the time domain is very costly in terms of processing power and a better approach is to do compensation in the frequency domain. Also, using a chirp function or even a step function, as illustrated by the data signal f(t) in Fig. 5 , would require rather heavy computational resources and a more cost effective and robust, although slightly more time consuming, method is to send single tone characterisation signals 610.
  • the single tone characterisation signal 610 is a signal of only one frequency.
  • Fig 6a depicts a single tone characterisation signal 610 transmitted at a first reference frequency f 0 with a transmit power P Tx .
  • the wireline transfer function h(t) can be Fouirer transformed into a wireline frequency response function H(f).
  • H(f) the frequency response function of the wireline 150
  • it will change the amplitude, which means that the attenuation of the wireline 150 at the first frequency f 0 may be described according to Eqn. 1.
  • a 0 H F f 0 ⁇ P Tx
  • single tone characterisation signals 610 are transmitted at the frequencies f 0 to f n-1 .
  • the frequency response may be different at each of the frequencies as shown on the right side of Fig. 6b , where the single tone characterisation signals 610 are shown after being subjected to the wireline 150 frequency response function H(f).
  • the attenuation A j at each of the transmitted frequencies f 0 to f n-1 may be calculated according to Eqn. 2.
  • a i i ⁇ n n ⁇ 1 H F f i ⁇ P Tx
  • a gain curve associated with the wireline frequency response function H(f) shown in Fig. 6b
  • the attenuation A j at each of the single tone characterisation signals 610 can be calculated.
  • a gain function G(f) can be estimated.
  • Such a gain function G(f) is shown in Fig. 7b .
  • This gain function can be implemented as a digital filter and the filter can be applied to the single tone characterisation signals 610 in Fig. 7a . This will result in the signal of Fig. 7c .
  • Fig. 7d Passing the single tone characterisation signals 610 to the frequency response function H(f) that was the basis for the gain function G(f) will result in a substantially level response at a power of P Rx , as shown in Fig. 7d .
  • the gain in Fig. 7b is marked with a peak at 0dB, this is of course just an example to simplify the explanation.
  • the gain may be any number, positive or negative and the skilled person will know how to dimension the gain to optimise transmitter linearity and minimise noise.
  • the transmission loss L T of a wireline may be characterised as the transmitted power P Tx minus the received power P Rx .
  • the transmission loss L T may, as has been explained together with the single tone characterisation signals 610, be used frequency dependent.
  • the wireline transceivers 320 used in the downhole communications system 200 typically have a limited dynamic range.
  • the dynamic range is characterised by the minimum received power P Rx:min necessary to, with sufficiently low BER, receive, demodulate and decode data, this is called the sensitivity.
  • the transmit part of the transceiver has a maximum output power P Tx:max at which it, with e.g. sufficient linearity and spectral efficiency, transmits data.
  • the specified power may be different depending on what modulation and modulation speed is used. For instance, the minimum received power P Rx:min necessary for successful decoding is lower for e.g. GFSK than for 16QAM. As has been explained in previous sections, a lower symbol-rate will increase the energy per symbol E S and reduce the minimum received power P Rx:min .
  • the maximum dynamic range of the downhole communication system 200 is calculated as P Tx:max - P Rx:min .
  • the transmitting wireline transceiver 320 of the downhole communication system 200 is naturally aware of what modulation and bitrate (and consequently symbol-rate) to use. Further to this, the dynamic range of the system is known and from this, the maximum allowable compensation or shaping of the transmitted signal can be estimated. If the frequency response function H(f) requires a compensation outside of the dynamic range of the downhole communication system, the bitrate may be decreased and/or the modulation changed.
  • a method 800 performed by a wireline communication equipment 210 in a downhole communication system 200 will be explained.
  • the method comprises the steps of determining 810 the characteristics of a wireline 150. Based on these characteristics, a wireline frequency response function H(f) is estimated and this, and/or the characteristics of the wireline 150, is used to adjust 830 the bitrate such that the highest speed is achieved with required reliability.
  • the step of determining 810 may be done in many different ways and the following section will give an overview of how the step may be performed. The order in which things are done, and which device is configured to do what may be varied and the skilled person understands that such modifications of the description are well within the scope of the disclosure.
  • the step of determining 810 comprises transmitting at least one single tone characterisation signal 610 with a transmit power PTx configured such that it is possible for a receiving wireline communication equipment 210 to estimate e.g. the attenuation of the wireline 150 and/or other wireline 150 characteristics from the received single tone characterisation signal 610.
  • the receiving and the transmitting wireline communication equipment 210 may be one and the same. This may be done by having the wireline 150 comprise different signals paths for transmit data and receive data and connect these paths together in one end of the wireline 150 and connect the other end to the wireline communication equipment 210.
  • the transceiver 320 of the wireline communication equipment 210 simultaneously transmitting and receiving the single tone characterisation signal 610, it is possible to determine characteristics of the wireline 150 with one single wireline communication equipment 210. These characteristics may comprise e.g. loss and phase shift of the wireline 150. The phase shift may be determined by comparing the phase of the received single tone characterisation signal 610 with the transmitted single tone characterisation signal 610.
  • phase shift along a wireline 150 may occur both directly as a function of the electrical length of the wireline, i.e. the length as a factor of the wavelength ⁇ at the frequency of the single tone characterisation signal, and also due to parasitic effects and resonances occurring along the wireline 150.
  • the wireline 150 in the single wireline communication equipment 210, is arranged such that the total phase shift of the signal round trip is more than 360° it will not be possible to differentiate e.g. 380° phase shift from 20° phase shift which would result in different phase shift characteristics of 190° and 10° respectively, i.e. a possibly erroneous phase shift of 180°.
  • This phase shift error is not relevant for most types of communication but there are modulations where it is important to have all signals in phase e.g. adjacent subcarriers in OFDM where, if high bandwidth channels are used, there may phase shifts on certain channels that needs to be accurately determined.
  • This potential problem may be solved by transmitting the single tone characterisation signal 610 at low frequencies stepping the frequency of the single tone characterisation signal 610 while keeping track of the accumulation of the phase shift to determine when a full 360° occurs and compensate accordingly.
  • a similar solution is presented below when dual wireline communication equipment 210 is used to determine the wireline characteristics.
  • the receiving wireline communication equipment 210 will know the reference power used to transmit the single tone characterisation signal 610 and will thus be able to determine the loss characteristics of the wireline 150 at the frequency of the single tone characterisation signal 610.
  • the phase shift may be determined in a number of ways, one way to determine the relative frequency shift across a frequency range is to sweep the frequency of the single tone characterisation signal 610 at a defined pace and measure the frequency and phase of the received signal to. Any difference in phase, once the pace of the frequency sweep has been compensated for, is due to phase shift in the wireline 150.
  • a dual path wireline 150 i.e.
  • a wireline 150 comprising separate transmit and receive paths
  • the determining of wireline 150 characteristics may be done simultaneously in both transmit and receive. If a wireline with a single path is used, it may be possible to only characterise the communication in one direction and share the wireline 150 characteristics with the other wireline communication equipment 210. It may also, in any scenario, be possible to only have one wireline communication equipment 210 knowing the wireline 150 characteristics; this may be the case if, e.g. data in one direction is comparably slow and neither speed nor reliability is a factor in that direction.
  • Sending a series of single tone characterisation signals 610 on different frequencies will make it possible to determine the characteristics of the wireline on multiple frequencies. If a multi-carrier communications protocol, such as e.g. OFDM or any FDM system for that matter, is used it may be beneficial to characterise the wireline on the frequencies of all, or at least a subset of the carriers to be used.
  • a multi-carrier communications protocol such as e.g. OFDM or any FDM system for that matter
  • the step of determining 810 comprises sending at least two single tone characterisation signals 610 at at least two different frequencies.
  • the downhole communication system is a channelised system comprising at least two carriers at at least two different frequencies, and the step of determining 810 comprises sending a single tone characterisation signal 610 on at least two of the at least two different frequencies.
  • the characteristics will not only comprise the wireline 150 but also the associated path of the wireline transceiver 320 used when determining the wireline 150 characteristics.
  • it may be considered to use different power levels as well as different frequencies for the single tone characterisation signals 610. Such a configuration with different power levels will enable further shaping of the transmitted signal such that non-linarites of the signal chain are compensated for.
  • the step of determining 810 comprises determining one or more wireline characterisation parameters. In a further embodiment, the step of determining 810 further comprises sending at least two single tone characterisation signals 610 with at least two different power levels.
  • the method 800 may be initiated for several reasons, and depending on arrangement and configuration a characterisation trigger of the method may be different.
  • the method 800 is initiated at the installation of a wireline 150 to a downhole tool 110, e.g. when presence of a wireline is detected by the wireline communication equipment 210.
  • the determining step 810 associated with one single wireline communication equipment 210 may be initiated.
  • the determining step 810 associated with dual wireline communication equipment 210 may be attempted by a first wireline communication equipment 210 detecting the presence of the wireline, if no suitable acknowledgement is received from a second wireline communication equipment 210 it is likely that only the first wireline communication equipment 210 is connected and the determining step 810 has to wait until the second wireline communication equipment 210 is connected. Once the second wireline communication equipment 210 detects the presence of the wireline 150, it may attempt the determining step 810 and the first wireline communication equipment 210 will acknowledge in a suitable manner.
  • the determining step 810 is initiated at the start-up of the wireline communication equipment 210.
  • the determining step 810 is initiated upon detection of a change in one or more environmental parameters.
  • environmental parameters may be any measurable parameter e.g. acidic concentration, air pressure, humidity, temperature etc. It may be that many of these parameters are not directly correlated to the frequency response H(f) of the wireline 150, but they may very well affect the performance of the wireline transceiver 320. Take temperature as an example, where a temperature shift of 20° has little or no effect on passive cabling but may greatly impact e.g. the linearity and noise of the wireline transceiver 320.
  • the determining step 810 may be initiated by the detection of an increase in bit error rate of the received signal and/or a decrease of the signal strength of the received signal.
  • the determining step 810 may be started at configurable time intervals and/or manually by control commands communicated to the wireline communication equipment 210.
  • the wireline transfer function H(f) may be estimated 820.
  • the wireline characteristics may comprise one or more attenuations A j and/or one or more phase shifts each associated with one or more frequencies and/or transmit amplitude P Tx .
  • the wireline transfer function H(f) may, in any embodiment, be one single, or a series of discrete characteristics rather than a continuous function.
  • an inverse transfer function H -1 (f) may be estimated simply by e.g. changing positive wireline 150 characteristic values to negative values and/or calculating the inverse wireline 150 characteristic factors. Note that the estimated wireline characteristics may be separate for both e.g.
  • Each of the different series or value of characteristic of the wireline 150 may be stored and accessed as the appropriate situation arises. For instance, if wireline characteristics are estimated for a number of environmental situations, a change in environmental conditions may not have to trigger a restart of the method 800 but could simply result in the applicable wireline characterisation being retrieved from storage.
  • the estimate step 820 comprises estimating one or more wireline 150 attenuation values. In another embodiment, estimating 820 comprises estimating one or more wireline 150 phase shift values and in yet another embodiment the step of estimating 820 comprises estimating both phase shift and attenuation values of the wireline 150. In a further embodiment, the step of estimating is done for different power levels of the single tone characterisation signal 610.
  • the step of adjusting 830 comprises changing, if necessary, the bitrate/symbol-rate of transmissions.
  • the wireline characteristics are known from the step of determining 820 and these are used to find a suitable bitrate. If the wireline characteristics comprise loss characteristics, the loss may be used together with the known system factors such as the sensitivity and maximum transmit power of the wireline transceiver 320 at different modulation parameters, e.g. type, speed etc. If the loss characteristics is higher than the link budget allows, i.e. the sensitivity subtracted from the maximum transmit power, the bitrate may be reduced. At the reduced bitrate, the receiver will have a lower sensitivity (lower sensitivity means more sensitive, i.e.
  • each of the supported bitrates and modulations has a first threshold for the estimated wireline transfer function H(f) such that if the estimated wireline transfer function is above the first threshold, the bitrate may be increased. Further to this, each of the supported bitrates and modulations may have a second threshold for the estimated wireline transfer function H(f) such that if the estimated wireline transfer function is below the second threshold, the bitrate may be decreased.
  • FDM systems or any system utilising carriers on different frequencies, where wireline characterisation has revealed one or more carriers and/or channels to be too poor to use, these carriers may be omitted or barred from communication.
  • the decision to remove a frequency may be based on a third threshold that is below or the same as the second threshold as introduced above. It may be that there are transmissions of different bitrates at different channels depending on the estimated wireline transfer function H(f), i.e. all channels do not necessarily have to have the same bitrate and/or modulation.
  • the carrier exhibiting the worst bitrate may be used to set the bitrate for all carriers or, the worst channel may be removed (omitted or barred) as mentioned above, and the bitrate of the other carriers may be raised.
  • limits and their relation to change of bitrate is of exemplary nature. There may be any number of limits, thresholds or intervals with or without hysteresis relating to the estimated wireline frequency response function (H(f)). Each interval may be associated with a particular bitrate and/or modulation. There may be different sets of limits or intervals associated e.g. with different environmental conditions or power levels. All mentioned limits, thresholds and intervals may be configurable limits, thresholds or intervals. It is of course possible to make each limit, threshold or interval individually configurable, i.e. one threshold may be configurable and another threshold may be fixed.
  • the adjusting 830 step comprises comparing the estimated wireline frequency response function (H(f)) to a first limit and a second limit and if the estimated wireline frequency response function (H(f)) is above the first limit, increasing the bitrate and if it is below the second limit, decreasing the bitrate. In further embodiments, if any value of the estimated wireline frequency response function (H(f)) generates a response that is below a third limit, bar the frequencies being associated with such values from use
  • the inverse transfer function H -1 (f) may be used as a shaping function and the corresponding discrete values may be used as shaping parameters.
  • An optional shaping step 840 may be comprised in the method 800 of Fig. 8b .
  • the shaping step 840 is performed after the step of estimating 820 and may be done either before or after the step of adjusting 830.
  • An example using amplitude shaping will be used to explain this step and the skilled reader understands that a similar approach can be used when applying phase pre-distortion.
  • the estimated wireline frequency response function (H(f)) comprises, in this example, losses at frequencies.
  • the frequency resulting in the highest loss from the estimated wireline frequency response function (H(f)) is identified.
  • This frequency will be the baseline, the 0dB, and the losses at the other frequencies are relative to this frequency. These losses will all be below the baseline since the baseline was the maximum.
  • the relative losses calculated are used to attenuate all the channels prior to transmission thus enabling a, power wise, substantially flat transmission across all frequencies.
  • Shaping is very beneficial on e.g. communication system using sub-carriers where one burst comprises several sub-carriers. In many of these applications, there is a limit as to how much the power is allowed to vary across the burst.
  • shaping may be used within the same channel to have a linear power response all the way to saturation. This is beneficial in systems with an amplitude component in the modulation.
  • the method comprises the step of applying shaping 840 after the step of estimating 820.
  • bitrate adaptation described above may very well be used with in combination with other signalling protocols where for instance low speed control channels are utilised. These control channels may be used to e.g. communicate the start of a determining step 810, changes in environment, characterisation data of the wireline 150, bitrates at different channels/frequencies etc.
  • single tone characterisation signals 610 may be broadband signals of a certain bandwidth and that single tone does not necessarily mean one absolute tone as noise by e.g. oscillators and phase locked loops will increase the bandwidth of the signal.
  • the single tone characterisation signal 610 may be understood to mean any suitable characterisation signal and in many cases a single tone is the most cost effective solution.

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EP18183529.9A 2018-07-13 2018-07-13 Bohrlochkabelkommunikation Withdrawn EP3594445A1 (de)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP18183529.9A EP3594445A1 (de) 2018-07-13 2018-07-13 Bohrlochkabelkommunikation
US16/510,001 US20200018155A1 (en) 2018-07-13 2019-07-12 Downhole wireline communication
PCT/EP2019/068825 WO2020011979A1 (en) 2018-07-13 2019-07-12 Downhole wireline communication

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EP18183529.9A EP3594445A1 (de) 2018-07-13 2018-07-13 Bohrlochkabelkommunikation

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