此应用程序的某些内容目前无法使用。
如果这种情况持续存在,请联系我们反馈与联系
1. (WO2019050536) SYSTEM AND METHOD FOR RATE ADAPTIVE BIT LOADING UTILIZING NOISE FACTORS
注:相关文本通过自动光符识别流程生成。凡涉及法律问题,请以 PDF 版本为准

SYSTEM AND METHOD FOR RATE ADAPTIVE BIT LOADING UTILIZING NOISE

FACTORS

BACKGROUND

[0001] In communication systems, data packets are transmitted from one location to another location. As the data packet is transmitted, interference, or noise, in the signal can degrade the received signal which can result in a loss of fidelity or a complete loss of the data itself. Interference can be sourced from the transmission signal itself, the power applied to a signal, the connection wire and connectors used (for wireline connections), and other internal sources. Interference also can be sourced from outside the signal, such as other active transmissions, material surrounding the communication equipment, both natural and manmade, and other external sources. Communication schemes have been developed to overcome these interferences, for example, to provide error correction to the signal, to utilize varying modulation schemes, to provide cyclic prefix information to the signal, to adjust the amount of data inserted into a signal, to adjust the amount of power given to a signal, and to provide multiple subchannels for the signal.

BRIEF DESCRIPTION

[0002] Reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:

[0003] FIG. 1 illustrates a flow diagram of an example of a method to determine a bit allocation;

[0004] FIG. 2, illustrates a flow diagram of an example of a method to iteratively compute a bit allocation;

[0005] FIG. 3 illustrates a chart demonstrating a bit allocation method disclosed herein compared against previous allocation methods and a targeted bit error rate tolerance level;

[0006] FIG. 4 illustrates a block diagram of an example of a communication system having a modem incorporating a bit allocation scheme as disclosed herein;

[0007] FIG. 5 illustrates a diagram of an example communication system having two modems;

[0008] FIG. 6 illustrates a diagram of an example logging while drilling (LWD) or measure while drilling (MWD) system configured to perform formation drilling;

[0009] FIG. 7 illustrates a diagram of an example wireline well system configured to perform formation testing and sampling; and

[0010] FIG. 8 illustrates a diagram of an example of a permanent completion well system demonstrating an implementation of an acoustic communication system.

DETAILED DESCRIPTION

[0011] Data communications between two locations is a widespread need. When data is sent from one location to another there can be problems encountered. For example, data could be lost among noise in the transmission or degraded by interference from other sources. As power to the data signal is increased to overcome noise, the overall power consumption increases which can increase the necessary system power requirements, impacting efficiency and raising costs.

[0012] The ratio of the signal power to the noise level is typically expressed as the signal-to-noise ratio (SNR). Different materials used at either the transmitting or receiving ends, as well as the medium used to transmit the signal can affect the SNR. For example, if a physical connection is being utilized, the type of conductive material used in the cable, wire, or fiber can affect the SNR. In addition to the SNR, there also can be noise or interference generated from outside the communication system. This is commonly expressed as the signal-to-noise-plus-interference ratio (SINR). For example, there can be an interfering source between the transmitter and receiver that causes interference in the signal, such as a transmitter from another system's equipment or a wireline connection running through a subterranean iron-nickel, pyrrhotite, or maghemite deposit, where these minerals create a magnetic field that can interfere with the electrical signal.

[0013] To overcome these issues in the signal transmission, various techniques can be employed to decrease power consumption, increase the data density of the data packet, and decrease the data error or loss rates. Multicarrier modulation systems have been utilized as a data packet transmission scheme. Subcarriers, a sideband of a radio frequency carrier wave which is modulated to send additional information, also can be utilized as part of the scheme. In typical multicarrier modulation, for example, an orthogonal frequency-division multiplexing (OFDM) system, all sub-channels utilize the same constellation which may lead to an increased bit error rate (BER) in the sub-channels with low SNR and suboptimal utilization in other sub-channels with high SNR. This is common in wireline communication systems when a channel has a non-flat frequency response. When the channel response is known or can be acquired through training, discrete multi-tone (DMT) modulation provides the flexibility to adjust sub-channel utilization, depending on the channel statistics, so as to fully exploit the channel capacity. Different loading of bits or bit allocations can be used to boost the data packet throughput while maintaining a low error rate.

[0014] Existing bit loading algorithms typically focus on BER values, power consumption, and total throughput optimization assuming, however, that the only channel impairment that causes the degradation of transmission performance is the additive white- Gaussian noise (AWGN). When the channel is no longer AWGN, the DMT modulation relies on a cyclic prefix (CP) transmission to eliminate an inter-symbol interference (ISI) and an inter-channel interference (ICI) at the receiver. A CP provides information regarding signal coding and includes the

prefixing of a symbol with a repetition of the end, where a symbol is a unit of data encoding. As the size of the symbol increases, generally the BER also increases. An inter-symbol interference occurs when one symbol interferes with subsequent symbols. An inter-channel interference occurs when a transmission signal from one sub-channel interferes with another sub-channel. Both of these interference types have a similar effect on the transmitted signal, namely, as noise.

[0015] When the channel impulse response time is longer than the allocated CP length, the bit allocation scheme loses efficiency. Channel impulse response is a time period determined based on an output of a system when presented with a brief input signal, expressed as a function of time. While increasing the CP contributes to the increase in communication overhead, other industry solutions for loading bits may not be efficient in reaching a target BER tolerance level value in the presence of ISI and ICI parameters.

[0016] The disclosure presents a bit allocation scheme that employs a rate-adaptive bit loading algorithm with consideration of the presence of ISI and ICI parameters due to, for example, an insufficient CP. The disclosure is based on an estimation of sub-channel SINR value to reduce bit error probability (BEP) value. The bit allocation scheme can be implemented using a variety of equipment and can be used in a wireline communication system or a wireless communication system that, for example, does not vary rapidly, i.e., remains unchanged for a considerable amount of time.

[0017] The disclosed bit allocation method and system can be used with various types of modulation schemes. Discrete multi-toned (DMT) modulation is one modulation scheme used in the disclosure as an example. With DMT, the frequency band can be divided into discrete subchannels, where every sub-channel can be modulated by a different modulation scheme, for example, quadrature amplitude modulation (QAM), phase-shift keying (PSK), and frequency-

shift keying (FSK). These modulation schemes can be further qualified, for example, QAM can be denoted as M-ary QAM (M-QAM) to show that it comprises 8-QAM, 16-QAM, 32-QAM, 64-QAM, 128-QAM, and other schemes. PSK and FSK can similarly be represented by M-PSK and M-FSK respectively, for example, if M=2, the denotation BPSK can be used and if M=4, the denotation QPSK can be used. The channel impulse response time can be determined by the receiver through data-assisted channel estimation, and sent to the transmitter as feedback. To compensate for an increased BER value due to, for example, insufficient CP, the disclosed method estimates the interference power of a bit allocation and incorporates that in the calculation of a BEP value.

[0018] When integrated in a modem, the disclosed method can determine a loading of a data packet to the signal sub-channels under the limitation of a wireless or wireline cable, fiber, or wire propagation, as well as adjusting the BER value to satisfy a targeted tolerance level. The method is applicable to an AWGN environment and can also be applicable in an ISI and ICI interference environment.

[0019] Methods are described herein to estimate the sub-channel SNR, SINR, and BER values and to determine a bit allocation based on these values. The SINR and BER values can be determined in an iterative process, so that the mean BER value is below a targeted BER threshold level, which can be used to iteratively update the bit allocation.

[0020] In the above described methods, the SINR value can be estimated using initial setup information and then the SINR value can be re-evaluated as new informational parameters are known. The equation to estimate the SINR value is shown below:

S SNR SINR ~ N + 1 ~ 1 + SNR /SIR

where 5 represents the power of a signal, N represents power of the noise, and J represents power of the interference. SIR represents a signal-to-interference power ratio. The SNR values can be determined through various data-assisted channel estimation schemes, for example, but not limited to, minimum mean square error (MMSE) or least square (LS) schemes.

[0021] As noted above, a situation can occur where the channel impulse response time is longer than the CP for the signal. Interference can be generated in this circumstance and is generally identified as ISI and ICI interference types. It is known in the industry that ICI and ISI power are approximately the same. From this, it can be derived that the interference can be determined from:

Zkjci = Yk ~ Xk

where Z¾ is the interference at the kth sub-channel for the ICI (or ISI) interference, and Xk and Yk are the sent and received constellation points respectively at the kth sub-channel. A constellation is a representation of a signal modulated by a digital modulation scheme and displays the signal as an X-Y plane scatter diagram at sampling instants. This equation can also be represented more completely as


- N∑^ hi e -j2nkl/N

where


k sub-channel index

[0022] The interference amplitude in one particular sub-channel is a function of the tail channel response outside the guard interval, as well as the information bits sent and QAM order in all sub-channels. The sub-channel SIR value is therefore computed by


where SIRk is the signal interference ratio at a A: sub-channel, Xk is the sent constellation point at a kth sub-channel, and Z is the interference at a kth sub-channel. E is the expectation operator, i.e., the weighted average of a variable.

[0023] Once the SNR / SINR values are determined, the process can now determine the bit error probability value as shown here in three different formulas, based on the modulation scheme being used:


where Ρ denotes the symbol error probability (SEP) value at the k sub-channel, M is the subchannel constellation order selected from a set, for example {4, 8, 16, 32, 64, etc. ], for the kth

sub-channel, y is the sub-channel SNR/SINR value from above, for the kth sub-channel. Q is a

standard statistical function to determine the tail probability of the standard normal distribution.

[0024] Normally, the SNR and SINR values are assumed to be high and the sub-channel BEP value, denoted as Pb,k, can be approximated by PS k / log2Mk for M-QAM (which can be gray coded, i.e. reflected binary coded, if appropriate) and PS k/ 2 for QPSK. In situations where the sub-channel SNR/SINR value is low, it is recommended to calculate the BEP value accurately so that the overall mean BER value is close to the estimated BEP value. When the targeted BER tolerance level is not very small, continued processing of channel coding can further reduce the BEP value. The actual ratio of the SEP value to the BEP value can be viewed as a function of the SEP value and the modulation order, and this ratio can be approximated through training. The function of the SEP value can be represented by a polynomial function, one for each modulation order, where the SEP value is an input and the BEP value is an output. The coefficients can be determined by a best fit line, i.e. by fitting a curve to the observed raw data. The function of the SEP value, in some circumstances, may not be deterministic. With an accurate ratio, denoted as /¾, the estimated BEP value can be calculated from the SEP formula as Pb,k ~ Ps.k / TTk- The SEP / BEP ratio can be iteratively evaluated as new interference information is determined and the ratio can be adjusted for the sub-channels and modulation orders being utilized.

[0025] In one implementation of the bit allocation, the function can be represented as follows:


where bk is the number of bits used in sub-channel k, N is the number of sub-channels, Pk is the BER of sub-channel k, P is the overall BER, and PTis the targeted BER tolerance level.

[0026] This function determines a maximum allowed sub-channel BER value. The maximum BER can be further adjusted so that the mean BER value will not exceed the targeted BER tolerance level. A look-up table of the corresponding BER value under different QAM modulations for every sub-channel SNR and SINR value can be generated and used in the bit allocation. This table can be iteratively updated as the interference level (SNR and SINR) varies with different bit allocations. Since the SNR/SINR look-up table is generated iteratively, the disclosed method also allows for excess BER error margin saved in a sub-channel to be distributed to another sub-channel since the method relies on both a mean BER value and a peak BER value constraint. Therefore, excess transmission capacity from one sub-channel can be utilized in a different sub-channel.

[0027] To reduce the computational load on simulating the interference levels, a bit loading algorithm based on AWGN channels, without consideration of additional interference, can be executed during the initialization of the method. The AWGN bit allocation can be adopted from a conventional algorithm. The initial peak BER value can be recorded as well. This initial function and evaluation provides an initial bit allocation that can be approximate to the final bit allocation.

[0028] The disclosed method can be used for bit allocation under full, partial, or no CP condition with minimum modification. This can provide a bit allocation under various interference conditions, including no interference. In addition, one copy of the data packet is utilized and interleaving of data within the data packet is not utilized, therefore data bandwidth and method complexity can be reduced.

[0029] The method closes the difference between a maximum symbol size value and a minimum symbol size value with a minimum number of iterations. The value of a maximum allowed subchannel BER value can be adjusted within each iteration by a bisection method until the mean BER value is equal to or less than the target BER tolerance level, while a look-up table, populated with a BER value corresponding to a modulation scheme, is updated with the SNR or SINR value result from the last allocation. There is a potential that the change in symbol size within the first two iterations can be significant, which can lead to inaccurate estimations using the look-up table built from these first two iterations. Thus, the first two iterations of the algorithm can have the recordation in the look-up table step skipped. As the bit allocation results converge, where the minimum and maximum symbol sizes approach the same value, the look-up table data also converges, and therefore, the estimation error on interference level can be reduced. The maximum allowed sub-channel BER value can be adjusted by a determined delta factor when the new allocation is not between the maximum and minimum symbol size. The initial value of the determined delta factor can be initialized to be proportional to the average SNR/SINR value across all sub-channels or it can be set to a value determined during the initialization phase of the bit allocation method.

[0030] In one implementation, the method can be implemented within a computer program which processes with, or separately from, other equipment or systems. For example, the computer program can operate in a modem located separately from other equipment or embedded within equipment used for other purposes.

[0031] In another implementation, the method can be implemented in a modem, which itself is part of a larger communication system where one modem is communicating with at least one additional modem. The modem described herein can be located in one of many locations, for example, in a separate room, building, or continent, or one modem can be located in a wellbore while another modem is located with a well system surface equipment. In this example scenario, a modem can be part of or associated with downhole equipment, such as sensors and tools, of a wellbore system and a second modem can be located with surface equipment of a well system so that data packets of the wellbore tools can be transmitted to the surface equipment through the surface modem and commands can be transmitted to the downhole modem which in turn can communicate with the wellbore tools. The wellbore can be of a variety of well system types, for example, a MWD, a LWD, a wired drill pipe, a coiled tubing (wired and unwired), wireline, slickline, and downhole tractor well systems.

[0032] Turning now to the Figures, FIG. 1 illustrates a flow diagram of an example of a method 100 to determine a bit allocation. The bit allocation method 100 is part of a communication system that can determine how a data set, within an electronic signal, is packed and prepared for transmission. The method 100 is an overview of the method details and can be utilized to generate a bit allocation with varying degrees of noise and interference of the transmission signal. The transmission signal can utilize a variety of modulation schemes and can use part, all, or none of a cyclic prefix. The method 100 begins in a step 101.

[0033] In a step 110, initial values for interference and other noise factors are estimated or computed. These factors can be identified as IS I, ICI, and other types of interference as well as SNR and SINR interference. In a step 120, an initial bit allocation is determined based, in part, on the values determined in step 110. In a step 130, the error rates and error probabilities are calculated for the bits and symbols as derived after completing the step 120 computation.

[0034] In a decision step 140, method 100 determines whether the error rates and error probabilities are within the targeted tolerance level. Generally, if the BER is less than or equal to the targeted BER tolerance level, then the current bit allocation loading scheme is accepted. If the decision step 140 resultant is "Yes", then the method 100 proceeds to a step 190 where data is communicated by the communication system using the current bit allocation. The data can be data packets transmitted from a downhole tool to surface equipment, such as a well system controller. The data can also be operating commands transmitted from the surface equipment to the downhole tool. After communicating using the current bit allocation, the method 100 ends in a step 195.

[0035] If the decision step 140 resultant is "No", then the method proceeds to a step 150. In the step 150, the bit error factor, i.e. the maximum BER value, and offset delta value are adjusted so as to attempt to bring the BER at or under the targeted BER tolerance level. In a step 160, new data packet symbol sizes are determined based, in part, on the adjusted error factors as determined in step 150. In a step 170, new interference and noise level values are estimated or computed based, in part, on the new symbol sizes determined in step 160. In a step 180, a new bit allocation is computed based on the factors determined in steps 150, 160, and 170. The method 100 returns to step 130 for iterative processing until an acceptable bit allocation is determined.

[0036] FIG. 2 illustrates a flow diagram of an example of a method 200 to iteratively compute a bit allocation. The method 200 expands on the method 100, providing additional computations and determinations made within the method. Any of the modems disclosed in Figures 4, 5, 6, 7, and 8 can be configured to perform the method 100 and the method 200. The method 200 begins in a step 201.

[0037] In a step 203, a bit allocation is computed for data packets to be transmitted. To reduce computational loading on simulating the interference level, the initial bit allocation can be determined based on AWGN channels without considerations of interference. The initial peak BER P is also recorded which allows the method 200 to start from a bit allocation that could be close to the final allocation. Within step 203, an approximate delta factor δ, which is a factor used to adjust the maximum allowed sub-channel BER value P, is determined. The delta factor δ is recorded as an initial delta factor 5i, and is used in subsequent steps of the method 200. [0038] In a decision step 205, a determination is made whether the bit allocation is the first computation thereof for the data packets. If the decision step 205 resultant is "Yes", then the method 200 proceeds to step 230.

[0039] In step 230, interference under the current bit allocation scheme and a sub-channel SINR value are determined. Additionally, Pt is generated, where Pt is a look-up table comprising the expected BER values for every subcarrier under the calculated sub-channel SINR values for each modulation order. Initial interference values have to be determined prior to generating a look-up table for the BER value. After step 230, the method 200 proceeds to step 233.

[0040] Returning to decision step 205, if the resultant is "No", then the method 200 proceeds to step 210 where a bit allocation is computed utilizing the predetermined look up table Pt and the maximum allowed BER value P. The method 200 proceeds to decision step 215 where a determination is made whether the information written to a buffer M, i.e. the mean BER value and the maximum allowed BER value, has been sorted (see step 240 for further details on the buffer contents). If buffer M is empty, the decision step 205 will consider buffer M as unsorted. If the decision step 215 resultant is "No" then the method 200 proceeds to step 230. If the resultant is "Yes", then the method 200 proceeds to decision step 220 where a determination is made whether the comparison of the current symbol size value Snew is greater than or equal to a maximum symbol size value SH (SH is determined in step 240). If the resultant of the decision step 220 comparison is "Yes" then the method 200 proceeds to step 222 where the maximum allowed BER value P is recalculated by dividing P by one plus the initial delta factor [P = P (1 + δι)] . The method 200 then proceeds to decision step 228.

[0041] Returning now to decision step 220, if the resultant is "No", then the method 200 proceeds to decision step 225 where a determination is made whether the comparison of the

current symbol size value SNEW is less than or equal to a minimum symbol size value SL (SL is determined in step 240). If the resultant of the decision step 225 comparison is "Yes" then the method 200 proceeds to step 227 the maximum allowed BER value P is recalculated by multiplying P by one plus the initial delta factor [P = P(l + 50]. The method 200 then proceeds to decision step 228. If the resultant of the decision step 225 is "No", then the method 200 proceeds to step 230.

[0042] In decision step 228, a determination is made if the newly calculated maximum allowed BER value P from the current iteration is equal to the maximum allowed BER value P from the previous iteration. If the resultant is "Yes", then the method 200 proceeds to step 229 where the initial delta value 5i is recalculated by dividing it by two [¾ = 5i / 2] . The method 200 then proceeds to step 210. If the resultant is "No" with respect to step 228, the method 200 also proceeds to step 210.

[0043] Returning now to step 233, the current overall BER value P is computed. The method 200 then proceeds to decision step 235 where a determination is made whether this is the first iteration (n=l) of the method 200. If this is not the first iteration, then the method 200 proceeds to decision step 237 where a determination is made whether this is a second iteration. If this is the second iteration, then the method 200 proceeds to decision step 270; otherwise decision step 238. In decision step 238, a determination is made whether the M buffer is empty. If the M buffer is empty then the method 200 proceeds to step 250. In step 250, the current bit allocation with the determined overall BER value P and the maximum allowed BER value P are loaded to buffer M. The method 200 then continues to decision step 270.

[0044] Decision step 270 determines if the overall BER value P is greater than the targeted BER tolerance level PT . If the overall BER value P is greater than the targeted BER tolerance level P then the method 200 proceeds to step 275 where the maximum allowed BER value P is recalculated by dividing that value by one point one plus the delta value [P = P I ( 1.1+ δ)]. The method 200 then proceeds to step 210. At decision step 270, if the overall BER value P is less than or equal to the targeted BER tolerance level PT then the method 200 proceeds to step 273. In step 273, the delta value δ is reset by dividing the delta value δ by two [δ = δ / 2] and the maximum allowed BER value P is reset by multiplying that value by one point one plus the delta value [P = P (1. 1 + δ)]. The method 200 then proceeds to step 210.

[0045] Returning to step 235, if this is the first iteration, then the method 200 proceeds to decision step 260 where a determination is made if the overall BER value P is greater than the targeted BER tolerance level PT . If the overall BER value P is greater than the targeted BER tolerance level PT then the delta value δ is recalculated in a step 265 by multiplying the delta value δ by the ratio of one plus two times the overall BER value divided by the targeted tolerance level [δ = δ (1 + 2 P/PT)] . Additionally, in step 265 the maximum allowed BER value P is recalculated by dividing that value by one plus the delta value [P = P / (1+ δ)]. The method 200 then continues to step 210.

[0046] Returning to step 260, if the overall BER value P is less than or equal to the targeted BER tolerance level PT then the method 200 proceeds to step 290 where the currently determined bit allocation is used for transmitting the data packets. The method 200 then ends in a step 291.

[0047] Returning to step 238, if the M buffer is not empty, then the method 200 proceeds to step 240. In step 240, the maximum symbol size SH and the minimum symbol size SL are recorded. This can be performed by adding the current bit allocation, the overall BER value P, and the maximum allowed BER value P to the buffer M. The buffer M can then be sorted by the overall

BER value P. The maximum symbol size value SH can then be assigned to the smallest symbol size where the overall BER value P is greater than the targeted BER tolerance level PT and the minimum symbol size variable SL can be assigned to the largest symbol size where the overall BER value P is less than the targeted BER tolerance level PT . The method 200 then continues to decision step 242 where a determination is made whether the maximum symbol size SH and the minimum symbol size SL have valid values, i.e. values were found that match the criteria described in step 240. If one or both SH and SL are not valid, then the method 200 proceeds to step 243.

[0048] Step 243 executes the first function to double the size of the delta value [δ = 2δ]. The second function can execute one of two possible equations. If the maximum symbol size variable SH is not valid then step 243 will calculate the maximum allowed BER value P as the maximum allowed BER value P for SL multiplied by one point one plus the delta value [P = P(SL)(1 - 1 + δ)] . If the minimum symbol size variable SL is not valid, then step 243 will calculate the maximum allowed BER value P as the maximum allowed BER value P for SH divided by one point one plus the delta value [P = P(SH)/(1 - 1 + δ)] . The method 200 proceeds to step 210.

[0049] Returning to step 242, if both SH and SL are valid then the method 200 proceeds to decision step 245 where a determination is made based on the difference between the maximum symbol size value SH and the minimum symbol size value SL- If the resultant of the calculation is equal to or less than a targeted range (in this example, the targeted range amount is set to equal one), meaning that the values have sufficiently converged, then the method 200 proceeds to step 246 where the bit allocation associated with the minimum symbol size value SL is used for transmitting the data packets. The method 200 then ends in step 291. If the resultant is an other value than the targeted range at step 245, then the method 200 proceeds to step 249.

[0050] At step 249, the maximum allowed BER value P is recalculated to the average of the maximum allowed BER values for the minimum and maximum symbol size variables [P = (P(SL) + P(SH)) / 2] . The method 200 then proceeds to step 210.

[0051] FIG. 3 illustrates an example of a graph 300 showing a measured bit error rate as compared to a target bit error rate for identified signal-to-noise ratios. The x-axis 310 describes the power to noise ratio, i.e. a SNR or SINR value in decibels (dB), and this data is plotted against the resulting observed bit error rate on the y-axis 315. A BER value is also dependent on the quality of a transmission medium such as a wireline, whether there is ISI or ICI present, the distance the transmitted signal needs to travel, whether CP data is included, as well as other factors. For this graph 300, these factors are held constant to illustrate how different bit allocations compare when implementing the same parameters.

[0052] The three line plots on graph 300 demonstrate how different bit allocations can be measured for effectiveness. For example, a target tolerance level 320 has been defined as 1.00E-03 (10"J) bit errors, i.e. 1.0 bit errors per 1,000 bits transmitted. Previous methods used in the industry are plotted as an example as line 340. The method disclosed herein is plotted as line 330. The graph 300 shows that the disclosed bit allocation, represented by line 330, is effective at achieving a minimal bit error rate. In this graph 300, the method disclosed herein represented by line 330 meets the targeted BER tolerance level 320 and is better than the targeted level at several points during the evaluation.

[0053] FIG. 4 illustrates a block diagram of an example of a communications system 400 constructed according to the principles of the disclosure. In this example, the communications system 400 includes a modem 401 which interacts with other system equipment 470 and 480 of the communications system 400. The modem 401 can be configured to execute the bit allocation

methods described herein. The disclosed methods can also be implemented in a separate physical unit, embedded within another unit, part of an embedded computer circuit, or in other types of implementations. The communication system 400 demonstrates just one possible implementation.

[0054] Modem 401 is a rate adaptive modem that is configured to communicate (transmit and receive) data over a wireless or wired medium. Modem 401 can be a DMT modem. Modem 401 includes several components identified as a processor 405, a generator 410, a bit loader 420, a modulator 430, a transmitter 440, a receiver 450, and an evaluator 460. The components can be implemented as hardware, software, or a combination thereof. Other modem implementations can include some, all, or additional components typically included in a modem that are not listed above.

[0055] Processor 405 is configured to estimate a SNR, SINR, and BER values of the communication medium. Generator 410 can be configured to create a BER value look-up table iteratively based on SNR and SINR input values. Bit loader 420 is configured to execute a bit loading algorithm without interleaving data in the data packet utilizing SNR, SINR, and BER values. Modulator 430 is configured to modulate a signal generated from the output of the bit loading algorithm utilizing one or more types of modulation techniques, for example, M-QAM, M-PSK, and M-FSK. Transmitter 440 can be configured to transmit the modulated signal to another device. Receiver 450 can be configured to receive a modulated signal from another device, demodulating the signal, and passing the resultant data packets to other components of the modem 401 or external systems. Evaluator 460 can be configured to determine a SEP and a BEP value based on the transmission parameters determined by the modem 401 and then

iteratively outputting the SEP and BEP values as input for the respective work of the other components of the modem 401.

[0056] The communication system 400 shows external system equipment 470 sending and receiving data packets 475 with the modem 401. In addition, the modem 401 can send and receive data packets 485 to external system equipment 480. System equipment 470 and 480 can be the same system equipment or separate system equipment, and they can be located various distances from one another. In one example the system equipment 470 and 480 are computers and the modem 401 communicates data packets 475 and 485 thereto. In another example, the system equipment 470 is a downhole wellbore logging tool and the system equipment 480 is surface well equipment such as a well system controller . In this example the downhole wellbore logging tool (i.e., 470) includes or communicates with the modem 401, which in turn sends and receives data packets, through a signal carried on, for example, a wireline cable, to a second modem located at the surface which is communicating with or included in the surface well equipment (i.e., 480).

[0057] FIG. 5 illustrates a diagram demonstrating an example of a communication system 500, with internal and external interference shown. The communication system 500 includes two modems 501 and 510 communicating using a signal 505. Signal 505 can be transmitted, for example, using acoustics or radio frequencies (RF). Some implementations can use acoustic through tubing, acoustic through fluid, or another medium type. Wireless or wired communications, for example, over a wireline, cable, or fiber, can also be used for communicating. The communication medium can be a multicarrier medium with a limited number of subcarriers, for example, a monocable telemetry system used for data acquisition in oilfield operations. SNR interference is represented by dashed lines 515. SNR interference can be due to physical connectors or physical transmission line, noise generated from within the modems, or from other sources, including ISI and ICI types. Dashed lines 516 represent outside interference on the transmitted signal. Modems 501 and 510 can include sufficient computer processing power, including the necessary circuitry and stored operating instructions to implement and execute the methods disclosed herein such as method 100 and method 200.

[0058] FIG. 6 illustrates a diagram of a LWD/MWD well system 600 including a communications system constructed according to the principles disclosed herein. The well system 600 demonstrates a system in which the methods disclosed herein can be employed. Well system 600 includes well surface equipment 601, a well system controller 602, a surface modem 603, wellbore 604 located below the well surface equipment 601, a drill string 610 inserted through wellbore 604, and downhole well tool 611 with downhole modem 612 at a lower point in the wellbore 604 than the well surface equipment 601. Modem 603 and modem 612 can communicate through various mediums, for example, acoustically through the drill string 610, through a wired connection (not shown), or through a wireless transmission. Modem 603 can communicate with the well controller 602 through conventional methods and modem 612 can communicate with the downhole well tool 611 through conventional methods typically employed downhole.

[0059] For example, modem 612 can receive tool logging data packets from the downhole well tool 611. Modem 612 can execute methods disclosed herein and transmit the modulated signal through the selected transmission method to surface modem 603. In the process of sending that signal, there can be identified interference noise, shown as dashed line 630, (e.g., SNR and SINR), for example, on drill string 610 or the wired transmission line (not shown). The modem 612, after receiving a response from modem 603, can iteratively update its information to perform the bit allocation with a lower BER value for the next data packet transmission.

[0060] In addition to the interference noise 630, there can exist external interference sources denoted as dashed lines 625. This interference can be caused by many factors, such as nearby wellbores, other equipment operating nearby, or certain natural or man-made subterranean features. In this example, subterranean minerals 620 surrounding part of the wellbore can cause interference (SINR) in the transmission signal, for example, if such minerals had a strong natural magnetic field. The methods disclosed herein can account for the SNR and SINR interferences to generate a bit allocation that achieves at least the target BER tolerance level.

[0061] FIG. 7 illustrates a diagram of a wireline well system 700 including a communications system constructed according to the principles disclosed herein. The well system 700 demonstrates a similar implementation, as to well system 600, of the methods disclosed herein. Well system 700 includes surface well equipment 701, a well system controller 702, a surface modem 703, wellbore 704 located below the surface well equipment 701, wellbore casing 705, a cable line or cable 710, shown as a solid line below casing 705 and a dashed line in casing 705, inserted through wellbore 704, and downhole well tool 711 with downhole modem 712 at a lower point in the wellbore 704 than the surface well equipment 701. The cable 710 can be a conventional type of cable used in wellbores, for example, a monocable used in a monocable telemetry system. The downhole well tool 711 can be a conventional type of tool used within a wellbore, for example, a sonde, probe, measuring device, or nuclear magnetic resonance device. In this illustrated example, modem 703 and modem 712 can communicate through transmissions sent through cable 710. Modem 703 can communicate with the well controller 702 through

conventional methods made available and modem 712 can communicate with the downhole well tool 711 through conventional methods.

[0062] For example, modem 712 can receive data packets from the downhole well tool 711 and execute the methods disclosed herein, such as method 100 or 200, to allocate bits for transmitting the data packets through cable 710 to surface modem 703. In the process of sending a modulated signal via cable 710, there can be identified interference noise, shown as dotted line 730 (e.g., SNR and SINR) on the cable 710. The modem 712, after receiving a response from modem 703, can iteratively update its information to perform bit allocation with a lower BER value for the next data packet transmission.

[0063] In addition to the interference noise 730, there can exist external interference sources denoted as dashed lines 725. This interference can be caused by many factors, such as nearby wellbores, other equipment operating nearby, or certain natural or man-made subterranean features. In this example, subterranean minerals 720 surrounding part of the wellbore can cause interference (SINR) in the transmission signal, for example, if such minerals have a strong natural magnetic field. The modems 703 and 712 can account for the SNR and SINR interferences to generate a bit allocation that achieves at least the target BER tolerance level.

[0064] FIG. 8 illustrates a diagram of a cross-sectional view of a permanent completion well system 800. The well system 800 demonstrates a similar implementation of a communication system as in well systems 600 and 700, of the methods disclosed herein. Well system 800 includes surface well equipment 801, a well system controller 802, a surface modem 803, wellbore 804 located below the surface well system equipment 801, wellbore casing 805, completion string 810, inserted through wellbore 804, packer 806, downhole well tool 811 with downhole modem 812 at a lower point in the wellbore 804 than the surface well equipment 801, and an end of well cap 807. Packer 806 provides a seal between the point where wellbore casing 805 ends and the continuation of the remaining uncased wellbore 804.

[0065] In this example, there is no wireline, cable or other direct connection between surface modem 803 and downhole modem 812. These two modems can be communicatively coupled using an acoustic technology, for example, an acoustic through tubing method, though any wired, wireless, or acoustic transmission method can be used. The downhole well tool 811 can be a completion tool used within a wellbore. Modem 803 can communicate with the well controller 802 through conventional methods and modem 812 can communicate with the downhole well tool 811 through conventional methods used in completed wells.

[0066] For example, modem 812 can receive data packets from the downhole well tool 811 and execute the methods disclosed herein, such as method 100 or 200, to allocate bits for transmitting the data packets through an acoustic method to surface modem 703. In the process of sending a modulated signal, there can be identified interference noise, shown as dotted line 830 (e.g., SNR and SINR) on the completion string 810. The modem 812, after receiving a response from modem 803, can iteratively update its information to perform the bit allocation with a lower BER value for the next data packet transmission.

[0067] In addition to the interference noise 830, there can exist external interference sources denoted as dashed lines 825. This interference can be caused by many factors, such as nearby wellbores, other equipment operating nearby, or certain natural or man-made subterranean features. In this example, subterranean minerals 820 surrounding part of the wellbore can cause interference (SINR) in the transmission signal, for example, if such minerals have a strong natural magnetic field. The method disclosed can account for the SNR and SINR interferences to generate a bit allocation that achieves at least the target BER tolerance level. While the well systems 600, 700 and 800 are shown on land, the communication systems implemented therein can also be used in near shore or offshore well systems.

[0068] In interpreting the disclosure, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms "comprises" and "comprising" should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.

[0069] Those skilled in the art to which this application relates will appreciate that other and further additions, deletions, substitutions and modifications may be made to the described implementations. It is also to be understood that the terminology used herein is for the purpose of describing particular implementations only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the claims.

[0070] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, a limited number of the exemplary methods and materials are described herein.

[0071] It is noted that as used herein and in the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

[0072] The above-described systems and methods or at least a portion thereof may be embodied in or performed by various processors, such as digital data processors or computers, wherein the computers are programmed or store executable programs or sequences of software instructions to perform one or more of the steps of the methods. The software instructions of such programs

may represent algorithms and be encoded in machine-executable form on non-transitory digital data storage media, e.g. , magnetic or optical disks, random-access memory (RAM), magnetic hard disks, flash memories, and/or read-only memory (ROM), to enable various types of digital data processors or computers to perform one, multiple, or all of the steps of one or more of the above-described methods or functions of the system described herein.

[0073] Certain embodiments disclosed herein may further relate to computer storage products with a non-transitory computer-readable medium that have program code thereon for performing various computer-implemented operations that embody at least part of the apparatuses, the systems, or carry out or direct at least some of the steps of the methods set forth herein. Non-transitory medium used herein refers to all computer-readable media except for transitory, propagating signals. Examples of non-transitory computer-readable medium include, but are not limited to: magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD-ROM disks; magneto-optical media such as floptical disks; and hardware devices that are specially configured to store and execute program code, such as ROM and RAM devices. Examples of program code include both machine code, such as produced by a compiler, and files containing higher level code that may be executed by the computer using an interpreter.

[0074] Embodiments disclosed herein include:

A. A method of bit allocation for transmitting a data packet over a multicarrier transmission system without interleaving the data packet and wherein a single copy of the data packet is loaded for the transmitting, the method comprising estimating a signal-to-noise-plus-interference ratio (SINR) value, a symbol error probability (SEP) value, and a bit error probability (BEP) value of a sub-channel associated with the multicarrier transmission system, computing the bit allocation utilizing the estimated SINR, SEP, and BEP values; calculating a ratio of the SEP value to the BEP value based on a function of the SEP value and a selected modulation order, determining a bit error rate (BER) value based on the ratio, and re-computing the bit allocation based on a comparison of the BER value to a target BER tolerance level value.

B. A communication system operable to transmit a digital signal comprising one or more data packets, comprising a processor operable to measure at least one of a signal-to-noise ratio (SNR) value, signal-to-noise-plus-interference ratio (SINR) value, and bit error rate (BER) value, a generator operable to create a BER value look-up table iteratively based on the SNR value and the SINR value input, and a bit loader operable to execute a bit loading algorithm with non-interleaving data packet data, utilizing one copy of the data packet, and utilizing at least one of the SNR, SINR, and BER values.

C. A computer program product including a series of operating instructions stored on a non-transitory computer readable medium that, when executed, directs a modem to perform a bit allocation for transmitting a data packet without interleaving the data packet, the bit allocation comprising estimating a signal-to-noise-plus-interference ratio (SINR) value, a symbol error probability (SEP) value, and a bit error probability value (BEP) value, computing the bit allocation utilizing the estimated SINR, SEP, and BEP values utilizing one copy of the data packet, calculating a ratio of the SEP value to the BEP value based on a function of the SEP value and a modulation order, determining a bit error rate (BER) value based on the calculating step output, and re-computing the bit allocation based on a comparison of the BER value to a target BER tolerance level value.

[0075] Each of embodiments A, B, and C may have one or more of the following additional elements in combination:

Element 1: wherein the calculating the ratio of the SEP value to the BEP value is performed iteratively. Element 2: utilizing the BER value as an input to distributing excess transmission capacity in a sub-channel to one or more other sub-channels, where the excess transmission capacity is identified by an excess BER error margin value. Element 3: communicating data between surface equipment of a well system and downhole equipment of the well system using the re-computed bit allocation. Element 4: modulating the sub-channel with a first modulation scheme and modulating additional sub-channels with a second modulation scheme where the first modulation scheme is different than the second modulation scheme. Element 5: building a look-up table comprising of the BER values corresponding to quadrature amplitude modulation (QAM) for a sub-channel SINR value, and updating iteratively the look-up table based on varying interference levels generated by varying bit allocations. Element 6: utilizing a maximum symbol size value and a minimum symbol size value where the symbol size values are determined from a maximum allowed BER value, and iterating through the method until the maximum symbol size value and the minimum symbol size value have a difference within a targeted range. Element 7: utilizing one of a null, zero length, partial complete length, and full length cyclic prefix (CP) parameter in the computing and re-computing bit allocation steps. Element 8: wherein the estimating step comprises at least one of an inter-symbol interference (IS I) parameter and an inter-channel interference (ICI) parameter. Element 9: a modulator operable to modulate a signal generated from the bit loader output, a transmitter operable to transmit the modulated signal, and an evaluator operable to determine a symbol error probability (SEP) value and bit error probability (BEP) value. Element 10: a receiver operable to receive a digital signal from a separate communication system. Element 11: wherein the communication system is operable to transmit the signal utilizing multiple sub-channels.

Element 12: wherein the signal is transmitted over a wireline of a well system. Element 13: wherein the communication system utilizes a measured impulse response time parameter and a measured signal interference parameter. Element 14: wherein the signal interference includes an inter-symbol interference (ISI) parameter or an inter-channel interference (ICI) parameter. Element 15: wherein the communication system comprises surface well equipment and downhole well equipment, wherein at least one of the surface and downhole well equipment includes the processor, generator, bit loader, modulator, transmitter, and receiver to communicate data there between. Element 16: wherein the transmitter and the receiver comprise a first modem and a second modem located within a wellbore operable to communicate with one or more wellbore tools and the first modem, wherein the first modem is located at a well system surface location and is operable to communicate with one or more well system surface operation equipment. Element 17: wherein the bit allocation further comprises modulating the bit allocation into one or more signals and transmitting the signals. Element 18: wherein the bit allocation further comprises measuring an impulse response time of the modem, determining an interference parameter comprising at least one of an inter-symbol interference (ISI) parameter and an inter-channel interference (ICI) parameter, and utilizing the impulse response time and the interference parameter in the computed bit allocation.