CN109327227A - A kind of channel coding method for wireless drilling measurement Transmission system - Google Patents

Abstract

The invention discloses a kind of channel coding methods for wireless drilling measurement Transmission system, it include: that underground is sent information to carry out Bose-Chaudhuri-Hocquenghem Code, data will be sent to be modulated at carrier wave and send after power amplification, from receiving signal demodulation data in ground instrument, using the hard decision algorithm of Berlecamp iterative algorithm optimization BCH code, the potential of BCH code is excited by the method for exhaustion, and underground is recovered with the alap bit error rate and sends information.Major advantage is: each group of exhaustive decoding result has instantaneity, at most only needs to save the data of two groups of Hard decision decoding results, does not have large effect to memory space；Transmission system is measured to wireless drilling by Soft decision decoding and brings at least coding gain of 2dB, can reduce the bit error rate of measurement while drilling Transmission system, reaches the target of extension measurement-while-drilling system transmission range by reducing signal-to-noise ratio under the premise of the bit error rate is constant.

Description

A kind of channel coding method for wireless drilling measurement Transmission system

Technical field

It is specifically a kind of to be surveyed for wireless drilling the present invention relates to the drilling measuring technologies such as petroleum, natural gas, coal mine field Measure the channel coding method of Transmission system.

Background technique

According to the difference of transmission medium, wireless drilling measuring system is divided into sound wave, mud-pulse and three kinds of electromagnetic wave transmission Mode.Wherein the decaying of sonic transmissions signal is big and serious by environmental disturbances；Mud-pulse high reliablity can be used in passing at a distance It is defeated and easy to operate, but signal transmission rate is low.Electromagnetic wave is not influenced by drilling fluid, can apply to foam drilling and gas bores Well is increased in transmission rate, but big by signal influence of fading, and transmission range is restricted.

Wireless drilling measuring system is divided into downhole instrument and ground instrument, and wherein downhole instrument obtains engineering ginseng from sensor Number, forms transmitting signal after encoded, modulation, amplification, ground instrument completes signal reception, signal condition, signal processing sum number According to demodulation/decoding.The engineering parameter of the system prevailing transmission drill bit, the information content for needing to transmit is small, generallys use shorter code It is long.

BCH code is an important subclass in linear block codes, and BCH code construction is convenient, and coding is simple, and decoding is easy to real It is existing, there is preferable bit error rate performance in the long situation of short code, and there is BCH code complete algebraic process to support, and be current Study a kind of most thorough error correcting code.If wireless electromagnetic measurement while drilling Transmission system channel coding uses linear block codes scheme, Because Hard decision decoding complexity is low but can not obtain preferable bit error rate performance, select Soft decision decoding algorithm very necessary.

Summary of the invention

The technical problem to be solved in the present invention is that for above-mentioned current wireless drilling measurement Transmission system signal transmission speed Rate is low or raising signal transmission rate can be provided one kind and be used for by signal influence of fading, the technological deficiency of limited transmission distance The channel coding method of wireless drilling measurement Transmission system solves the above problems.

A kind of channel coding method for wireless drilling measurement Transmission system, the specific steps are as follows:

Step 11, downhole instrument encodes information M to be sent using the coding method of BCH code, obtains sequence E；

Step 12, downhole instrument by the sequence E after coding it is modulated and amplification after send；

Step 13, it is demodulated from reception signal in ground instrument, obtains receiving sequence r；

Step 14, reception sequence r is decoded using a kind of Soft decision decoding algorithm.

Further, specific step is as follows for the coding method of BCH code in the step 12:

Step 21, a number is chosen on finite field gf (q) according to total code length N and is the irreducible polynomial of m, and construct GF (q^m), wherein q is prime number or prime power, and usually taking 2, m is a certain positive integer, and when q takes 2, m and N meet N=2^m- 1, GF (q^m) It altogether include N number of element, any GF (q^m) it all include element 0, αⁱIt is indicated for the power of remaining N-1 element, i desirable value is 0,1,2 ..., N-2；

Step 22, GF (q is sought^m) element αⁱ, the minimal polynomial m of i=1,3 ... 2t-1_i(x), wherein t indicates BCH code Error correcting capability binary BCH codes are certainly existed with α, α for any positive integer m and t³..., α^2t-1For root, code length N=2^m- 1, t mistake can be corrected, meets mt >=N-K between positive integer m and t and total code length N and information sequence length K；

Step 23, construction can entangle generator polynomial g (x)=m of t mistake₁(x)m₃(x)…m_2t-1(x)；

Step 24, according to generator polynomial structural matrix G₁=[x^k-1g(x) … x²g(x) xg(x) g(x)]^T, through row It converts matrix G₁The square matrix that the k column vector in left side is constituted is transformed to unit matrix, to obtain encoder matrix G, wherein k= K is information sequence length；

Step 25, it completes to encode according to formula E=MG, wherein M and E is respectively the information and warp knit to be sent in step 11 The sequence obtained after code, G are the encoder matrix acquired in step 24.

Further, specific step is as follows for a kind of Soft decision decoding algorithm in the step 14:

Step 31, hard decision is carried out to reception sequence r and obtains hard decision output hd_r；

Step 32, it determines unreliable bit position set the specific method is as follows according to receiving sequence r: in receiving sequence r The smallest preceding P1 position of confidence level is searched for, therein 0 is selected in this P1 position to P position, traverses all combinations It will be all possibleKind selection, which enumerates, to be come, and unreliable location sets T is constructed, to every in unreliable location sets T One group of unreliable position T_iIt executes step 33 and arrives step 36；

Step 33, according to one group provided in step 32 unreliable position T_i, it is assumed that hard decision exports corresponding in hd_r All error generates cycle tests set C=hd_r+T for position decoding_i；

Step 34, Hard decision decoding is carried out to test codeword C and obtains effective code word D, using effective code word D as decoding result Keep in R_flagIn, wherein R_flagFor memory, for storing effective code word D, the initial value of flag is 0；

Step 35, it calculates effective code word D and receives the Euclidean distance between sequence r and kept in Euc_flagIn, Middle Euc_flagFor memory, for storing calculated Euclidean distance；

Step 36, if Euc_flag> Euc_min enables flag=1-flag, and Euc_min is constant, otherwise enables Euc_min= Euc_flag, flag is constant, and wherein Euc_min is floating type variable, and initial value is+∞, generally takes in practical operation biggish Positive number, such as :+1000.0；

Step 37, by R_1-flagIn decoding result as final Soft decision decoding result export.

Further, following steps are used when carrying out Hard decision decoding to each test codeword C in the step 34 It carries out:

Step 41, syndrome S is calculated according to reception code polynomial R (x)_i(x), i ∈ { 1,2 ... 2t }, wherein t is that BCH is hard Decoded error correcting capability is write the test codeword C received as polynomial form:Wherein k₁, k₂,…,k_j∈ { 1,2 ..., N }, j≤N, then according to formulaIt calculates corresponding adjoint Formula；

Step 42, the n-order polynomial σ (x) about x is constructed with Berlecamp iterative algorithm, needs iteration 2t+1 altogether Secondary, wherein σ (x) is error location polynomial, and preceding iteration twice directly assigns initial value, and each iteration updates new out σ (x) and d, Last time iteration update σ (x) out be it is required, wherein σ (j+1) indicates to update σ (x), σ out when iteration j_k(j) Indicate x in σ (j)^kCorresponding coefficient, D (j) indicate the most high order number of x in σ (j), d_j+1It indicates to update out when iteration j D value；It is specific calculation method below:

Step 42 (a), the σ (x) and d assignment when to j=-1 and j=0 are as follows: σ (- 1)=1, D (- 1)=0, d_-1=1, σ (0)=1, D (0)=0, d₀=S₁(x), then the iteration since j=0, each iteration j increase by 1, until j=2t-1, constantly follow Ring 42 (b) is to 42 (d) steps；

Step 42 (b) selects suitable i, i to must satisfy i < j, d_i≠ 0, and the value of i-D (i) is maximum；

Step 42 (c) judges d_jIt whether is 0, if d_j=0 directly enables σ (j+1)=σ (j), otherwise according to formulaUpdate σ new out (j+1)；

Step 42 (d), according to formulaUpdate d new out_j；

Step 43, using the solution of Chien searching algorithm accounting equation σ (x)=0, the possible value one of x is shared: 0, α, α²,…,α^N-1, each possible value is substituted into equation σ (x)=0 and is scanned for, all of equation σ (x)=0 are therefrom found out Solution；

Step 44, sentence firmly if the number of solution of equation in step 43 is equal to the most high order number that x is in multinomial σ (x) Certainly verification passes through, and otherwise hard decision check does not pass through, and if verification, non trivial solution is the error bit in test codeword C if It sets, the information corrigendum of errors present in test codeword C is obtained into effective code word D.

The advantages of this algorithm, is: the hard decision algorithm of BCH code is optimized using Berlecamp iterative algorithm； At least coding gain of 2dB is brought to Transmission system by Soft decision decoding algorithm；Each group of decoding result of exhaustion has i.e. Shi Xing, at most only needs to save the data of two groups of decoding results, does not have large effect to memory space.

Detailed description of the invention

Present invention will be further explained below with reference to the attached drawings and examples, in attached drawing:

Fig. 1 is a kind of channel coding method schematic diagram that Transmission system is measured for wireless drilling of the present invention；

Fig. 2 is the flow chart of Soft decision decoding algorithm of the invention；

Fig. 3 is total code length N=31 of the invention, and BCH Soft decision decoding selects when information sequence length K=16, parameter P=2 Select the corresponding ber curve figure of different parameters P1；

Fig. 4 is total code length N=31 of the invention, and BCH Soft decision decoding selects different parameters when information sequence length K=16 The corresponding ber curve figure of P；

Fig. 5 is total code length N=31 of the invention, information sequence length K=16 and total code length N=63, information sequence length K The comparison diagram of BCH Hard decision decoding and Soft decision decoding ber curve when=36.

Specific embodiment

For a clearer understanding of the technical characteristics, objects and effects of the present invention, now control attached drawing is described in detail A specific embodiment of the invention.

A kind of process for the channel coding method measuring Transmission system for wireless drilling is as shown in Figure 1, wireless drilling survey Amount Transmission system is divided into downhole instrument and ground instrument two parts, specifically sends and receivees information using following methods:

Step 11, downhole instrument encodes information M to be sent using the coding method of BCH code, obtains sequence E；

Step 12, downhole instrument by the sequence E after coding it is modulated and amplification after send；

Step 13, it is demodulated from reception signal in ground instrument, obtains receiving sequence r；

Step 14, reception sequence r is decoded using a kind of Soft decision decoding algorithm.

Wherein specific step is as follows for BCH code coding method in step 11:

Step 21, a number is chosen on finite field gf (q) according to total code length N and is the irreducible polynomial of m, and construct GF (q^m)；

Wherein q is prime number or prime power, and usually taking 2, m is a certain positive integer, and m and N meet N=2^m-1。

Step 22, GF (q is sought^m) element αⁱ, the minimal polynomial m of i=1,3 ... 2t-1_i(x)；

Wherein t indicates the error correcting capability of BCH code.

Step 23, construction can entangle generator polynomial g (x)=m of t mistake₁(x)m₃(x)…m_2t-1(x)；

The step of calculating generator polynomial g (x) is relatively complicated, general directly by tabling look-up to obtain.

Common generator polynomial when binary BCH code code length N=63 and N=31 is as shown in table 1.

N	K	t	G (x) octal system form
				31	26	1	45
	21	2	3551
					16	3	107657
	11	5	5423325
					6	7	313365047
63	45	3	1701317
					39	4	166623567
	36	5	1033500423
					30	6	157464165547
	24	7	17323260404441
					18	10	1363026512351725
	16	11	6331141367235453

Table 1

Step 24, according to generator polynomial structural matrix G₁=[x^k-1g(x)…x²g(x)xg(x)g(x)]^T, converted through row By matrix G₁The square matrix that the k column vector in left side is constituted is transformed to unit matrix, to obtain encoder matrix G；

Wherein k=K is information sequence length.

Step 25, it completes to encode according to formula C=MG.

Decoding portion is decoded using a kind of soft-decision algorithm, and algorithm flow chart is as shown in Figure 2, the specific steps are as follows:

Step 31, hard decision is carried out to reception sequence r and obtains hard decision output hd_r, initialize flag=0, Euc_min =+∞；

Step 32, it determines unreliable bit position set, the smallest preceding P1 position of confidence level is searched in receiving sequence r It sets, selects therein 0 to arrive P position in this P1 position, it will be all possibleKind selection, which enumerates, to be come, construction Unreliable location sets T, to each group of unreliable position T_iIt executes step 33 and arrives step 36；

Step 33, according to one group provided in step 32 unreliable position T_i, it is assumed that hard decision exports corresponding in hd_r All error generates cycle tests set C=hd_r+T for position decoding_i；

Step 34, Hard decision decoding is carried out to test codeword C and obtains effective code word D, using effective code word D as decoding result Keep in R_flagIn；

Step 35, it calculates effective code word D and receives the Euclidean distance between sequence r and kept in Euc_flagIn；

Step 36, if Euc_flag> Euc_min enables flag=1-flag, and Euc_min is constant, otherwise enables Euc_min= Euc_flag, flag is constant；

Step 37, by R_1-flagIn decoding result as final Soft decision decoding result export.

Wherein specific step is as follows for Hard decision decoding in step 34:

Step 41, syndrome S is calculated according to reception code polynomial R (x)_i(x),i∈{1,2,…2t}；

Wherein t is the error correcting capability of BCH hard decoder, will receive test codeword and is write as polynomial form:Wherein k₁,k₂,…,k_jThen ∈ { 1,2 ..., N }, j≤N write out corresponding syndrome

Step 42, the n-order polynomial σ (x) about x is constructed with Berlecamp iterative algorithm, needs iteration 2t+1 altogether Secondary, wherein preceding iteration twice directly assigns initial value, each iteration updates new out σ (x) and d, and last time iteration updates σ out It (x) is required；

It is specific calculation method below, wherein σ (j+1) indicates to update σ (x), σ out when iteration j_k(j) σ is indicated (j) x in^kCorresponding coefficient, D (j) indicate the most high order number of x in σ (j), d_j+1It indicates to update d value out when iteration j.

Step 42 (a), parameter assignment parameter assignment when to j=-1 and j=0 are as follows: σ (- 1)=1, D (- 1)=0, d_-1 =1, σ (0)=1, D (0)=0, d₀=S₁(x), then the iteration since j=0, each iteration j increase by 1, until j=2t-1, no Disconnected circulation 42 (b) to 42 (d) steps；

Step 42 (b) selects suitable i, i to must satisfy i < j, d_i≠ 0, and the value of i-D (i) is maximum；

Step 42 (c) judges d_jIt whether is 0, if d_j=0 directly enables σ (j+1)=σ (j), otherwise according to formulaUpdate σ new out (j+1)；

Step 42 (d), according to formulaUpdate d new out_j。

Step 43, using the solution of Chien searching algorithm accounting equation σ (x)=0；

Wherein the possible value one of x is shared: 0, α, α²,…,α^N-1, each possible value is substituted into equation σ (x)=0 It scans for, therefrom finds out all solutions of equation σ (x)=0；

Step 44, sentence firmly if the number of solution of equation in step 43 is equal to the most high order number that x is in multinomial σ (x) Certainly verification passes through, and otherwise hard decision check does not pass through.

If verification, non trivial solution is the errors present in test codeword C if, by errors present in test codeword C Information corrigendum obtain effective code word D.

According to the flow chart of Soft decision decoding algorithm as shown in Figure 2, which has two parameters of P and P1, in order to make BCH code obtains bit error rate performance as well as possible, selects two parameters of P and P1 using control variate method, finds it by emulation The limit of bit error rate performance.

Below with code length N=31, the process of parameter selection is illustrated for information bit length K=16:

Control parameter P=3 first is constant, is continuously increased parameter P1.As can be seen from Figure 3 the mistake block of P1=5 and P1=4 Rate performance is compared, and gain is less than 0.1dB, therefore, it is considered that P1 takes 5 performances best as P=2.

It is continuously increased parameter P as shown in Figure 4, its performance no longer improves significantly when P gets 5, therefore chooses ginseng Limiting performance of the performance as the algorithm in code length N=31, K=16 when number P=5, P1=8.

Fig. 5 is total code length N=31, information sequence length K=16 and total code length N=63, when information sequence length K=36 The comparison diagram of BCH Hard decision decoding and Soft decision decoding ber curve is as can be seen from the figure given by the method for soft-decision System brings the gain of 2dB or more.

The embodiment of the present invention is described with above attached drawing, but the invention is not limited to above-mentioned specific Embodiment, the above mentioned embodiment is only schematical, rather than restrictive, those skilled in the art Under the inspiration of the present invention, without breaking away from the scope protected by the purposes and claims of the present invention, it can also make very much Form, all of these belong to the protection of the present invention.

Claims (4)

1. a kind of channel coding method for wireless drilling measurement Transmission system, which is characterized in that specific step is as follows:

Step 11, downhole instrument encodes information M to be sent using the coding method of BCH code, obtains sequence E；

Step 12, downhole instrument by the sequence E after coding it is modulated and amplification after send；

Step 13, it is demodulated from reception signal in ground instrument, obtains receiving sequence r；

Step 14, reception sequence r is decoded using a kind of Soft decision decoding algorithm.

2. a kind of channel coding method for wireless drilling measurement Transmission system according to claim 1, feature exist In specific step is as follows for the coding method of BCH code in the step 12:

Step 21, a number is chosen on finite field gf (q) according to total code length N and is the irreducible polynomial of m, and construct GF (q^m), Wherein q is prime number or prime power, and usually taking 2, m is a certain positive integer, and when q takes 2, m and N meet N=2^m- 1, GF (q^m) wrap altogether Containing N number of element, any GF (q^m) it all include element 0, αⁱIt being indicated for the power of remaining N-1 element, i desirable value is 0,1, 2 ..., N-2；

Step 22, GF (q is sought^m) element αⁱ, the minimal polynomial m of i=1,3 ... 2t-1_i(x), wherein t indicates entangling for BCH code Wrong ability certainly exists binary BCH codes for any positive integer m and t with α, α³..., α^2t-1For root, code length N=2^m- 1, it can T mistake is corrected, meets mt >=N-K between positive integer m and t and total code length N and information sequence length K；

Step 23, construction can entangle generator polynomial g (x)=m of t mistake₁(x)m₃(x)…m_2t-1(x)；

Step 24, according to generator polynomial structural matrix G₁=[x^k-1g(x) … x²g(x) xg(x) g(x)]^T, converted through row By matrix G₁The square matrix that the k column vector in left side is constituted is transformed to unit matrix, to obtain encoder matrix G, wherein k=K is Information sequence length；

Step 25, it completes to encode according to formula E=MG, after wherein M and E is respectively information to be sent in step 11 and is encoded Obtained sequence, G are the encoder matrix acquired in step 24.

3. a kind of channel coding method for wireless drilling measurement Transmission system according to claim 1, feature exist In specific step is as follows for a kind of Soft decision decoding algorithm in the step 14:

Step 31, hard decision is carried out to reception sequence r and obtains hard decision output hd_r；

Step 32, it determines unreliable bit position set the specific method is as follows according to receiving sequence r: being searched in receiving sequence r The smallest preceding P1 position of confidence level selects therein 0 to P position in this P1 position, traverses all combinations for institute It is possibleKind selection, which enumerates, to be come, and unreliable location sets T is constructed, to each group in unreliable location sets T Unreliable position T_iIt executes step 33 and arrives step 36；

Step 33, according to one group provided in step 32 unreliable position T_i, it is assumed that corresponding position is translated in hard decision output hd_r All error generates cycle tests set C=hd_r+T to code_i；

Step 34, Hard decision decoding is carried out to test codeword C and obtains effective code word D, kept in effective code word D as decoding result To R_flagIn, wherein R_flagFor memory, for storing effective code word D, the initial value of flag is 0；

Step 35, it calculates effective code word D and receives the Euclidean distance between sequence r and kept in Euc_flagIn, wherein Euc_flagFor memory, for storing calculated Euclidean distance；

Step 36, if Euc_flag> Euc_min enables flag=1-flag, and Euc_min is constant, otherwise enables Euc_min= Euc_flag, flag is constant, and wherein Euc_min is floating type variable, and initial value is+∞, generally takes in practical operation biggish Positive number, such as :+1000.0；

Step 37, by R_1-flagIn decoding result as final Soft decision decoding result export.

4. a kind of channel coding method for wireless drilling measurement Transmission system according to claim 3, feature exist In using following steps progress when in the step 34 to each test codeword C progress Hard decision decoding:

Step 41, syndrome S is calculated according to reception code polynomial R (x)_i(x), i ∈ { 1,2 ... 2t }, wherein t is BCH hard decoder Error correcting capability, write the test codeword C received as polynomial form:Wherein k₁, k₂,…,k_j∈ { 1,2 ..., N }, j≤N, then according to formulaIt calculates corresponding adjoint Formula；

Step 42, the n-order polynomial σ (x) about x is constructed with Berlecamp iterative algorithm, needs iteration 2t+1 times altogether, Middle σ (x) is error location polynomial, and preceding iteration twice directly assigns initial value, and each iteration updates new out σ (x) and d, finally An iteration update σ (x) out be it is required, wherein σ (j+1) indicates to update σ (x), σ out when iteration j_k(j) σ is indicated (j) x in^kCorresponding coefficient, D (j) indicate the most high order number of x in σ (j), d_j+1It indicates to update d value out when iteration j； It is specific calculation method below:

Step 42 (a), the σ (x) and d assignment when to j=-1 and j=0 are as follows: σ (- 1)=1, D (- 1)=0, d_-1=1, σ (0)= 1, D (0)=0, d₀=S₁(x), then the iteration since j=0, each iteration j increase by 1, until j=2t-1, constantly recycle 42 (b) to 42 (d) steps；

Step 42 (b) selects suitable i, i to must satisfy i < j, d_i≠ 0, and the value of i-D (i) is maximum；

Step 42 (c) judges d_jIt whether is 0, if d_j=0 directly enables σ (j+1)=σ (j), otherwise according to formulaUpdate σ new out (j+1)；

Step 42 (d), according to formulaUpdate d new out_j；

Step 43, using the solution of Chien searching algorithm accounting equation σ (x)=0, the possible value one of x is shared: 0, α, α²,…, α^N-1, each possible value is substituted into equation σ (x)=0 and is scanned for, all solutions of equation σ (x)=0 are therefrom found out；

Step 44, the hard decision school if the number of solution of equation in step 43 is equal to the most high order number that x is in multinomial σ (x) It tests and passes through, otherwise hard decision check does not pass through, and if verification, non trivial solution is the errors present in test codeword C if, The information corrigendum of errors present in test codeword C is obtained into effective code word D.