The threshold decoder of the convolutional code


H03M13/12 -

 

(57) Abstract:

The invention relates to computing and communication technology and can be used in digital communication systems using convolutional codes. The purpose of the invention is to increase the reliability of the decoding by fixing the most part three errors is achieved by the introduction of elements OR 8, 13, block 19 multiplied by the weight coefficient deciding circuit 7 and the imaging unit 6 checks, and entered the threshold, the counter 16 and the threshold element 9, the decoder containing encoders 1, 10, offset errors, 4 adders modulo 2 and 11, the elements OR 12, 18, shaper 3 syndrome generator 14 clock pulse shaper 17 time interval, the element 15. The essence of the invention: with the introduction of new elements and relationships implemented new discipline functioning of the threshold decoder of the convolutional code, which is that the decision about the value of the noise symbol is based on the adoption of flexible solutions on the threshold element. In addition, by determining the values of the noise symbol correction of the correction signal from the output of the threshold element, which together allows you to fix most part three errors that Oh technology and communication technology and can be used in digital communication systems, using convolutional codes.

Known threshold decoder of the convolutional code, containing the combined input encoder and corrector of errors and the analyzer syndrome whose outputs across the threshold element and block the ban correction is connected to the inputs of the error corrector and analyzer syndrome (1).

A disadvantage of the known threshold decoder is the low reliability of the decoding.

The closest in technical essence to the proposed device is the threshold decoder of the convolutional code, comprising a generator of clock pulses, the imaging unit time interval, the threshold count, the first and second encoders, the error corrector, the first and second adders modulo two, the first and second elements OR element "BAN", shaper syndrome, the threshold element, the analyzer syndrome (2).

A disadvantage of the known device is low reliability, due to the fact that on the basis of the analysis of the syndrome is detected only three-time errors, not correcting them.

The purpose of the invention is to increase the reliability of the decoding by fixing the most part three errors.

On theconcrete implementation.

The threshold decoder of the convolutional code contains (Fig. 1) first, the encoder 1, the first modulo 2, the imaging unit 3 syndrome, concealer 4 errors, the analyzer 5 syndrome, shaper signal checks, decisive scheme 7, the fourth element, OR 8, the threshold element 9, the second encoder 10, a second modulo-two 11, the first element OR 12, the third element OR 13, the clock 14, the element "BAN" 15, the threshold counter 16, the imaging unit time interval 17, the second element OR 18, block 19 multiplied by weighting factors.

First, the encoder 1 is designed to generate information on the characters in the test sequence. As the first encoder 1 uses a shift register associated with the adders modulo two. The first output of the first encoder 1 is connected to the first input of the corrector 4 errors, the second output with the first input of the first modulo 2.

First modulo 2 is designed to generate a test sequence quasiorthogonal convolutional code. The first input is connected to the second output of the first encoder 1, the second input with the second output of the second encoder 10, and the output from the second input of the shaper syndrome 3.

Formirovanii and a test sequence, formed at the receiving side. As a shaper syndrome is used modulo two. The first input of the shaper 3 syndrome is a validation input device, a second input connected to the output of the first modulo 2, and the output to the first input of the analyzer 5 syndrome.

Corrector 4 errors also represents the modulo two.

The analyzer 5 syndrome is designed to detect errors in the information and check symbols and represents a shift register with feedback and adders modulo two, the composition and quantity of which is determined by generating polynomials orthogonal convolutional code. The first input is connected to the output of the shaper 3 syndrome, the second input with the output of the fourth element OR 13, the first output from the imaging unit 6 checks the second output with the inputs of the third element OR 8 and block the multiplication of the weights 19, the third output to the first input of the second modulo-two 11.

The signal shaper 5 inspections is designed to generate checks, orthogonal with respect to the symbols received on the test channel.

As a shaper 6 checks use the speed deciding circuit 7.

Deciding circuit 7 is designed for a decision on the reliability of the received symbols. As the final circuit 7 uses the element And the first input connected to the output of the imaging unit 6 checks the second input with the output of the third element, OR 8, and the output from the second input of the fourth element OR 13.

The third element, OR 8 is designed to generate an enabling signal "1" to the second input of the deciding circuit 7 from the system of checks AND2AND3AND4supplied at its input with the second output of the analyzer 5 syndrome.

The threshold element 9 is designed for a decision on the reliability of the received symbols. Alarm level threshold element 9 is selected on the basis of patterns of checks. As a threshold element 9 for the case of a decision on the reliability of the received information symbols on weighted tests can be used to summarise the Schmitt trigger (3). The output of the threshold element 9 connected to the first input of the fourth element OR 13.

The second encoder 10 is designed to generate incremental discharges in generating the polynomial quasiorthogonal convolutional code that allows you to increase the weight of the initial code word, quasi the number of digits which communication is due to the additional polynomial quasiorthogonal convolutional code. The input is connected to the output of the corrector 4 errors, and the first output is an information output device.

The fourth element OR 13 is designed to combine the correction signals from outputs of the threshold element 9 and a determining circuit 7. The output of the fourth element OR 13 is connected to the second input of the corrector 4 errors, analyzer 5 syndrome, second modulo two 11 and the first element OR 12.

The generator 14 clock pulses is designed to generate clock pulses necessary for the operation of the shaper time frame 17, and is an independent device. The output of the generator 14 clock pulses associated with the third input element 15 "BAN".

Item 15 "BAN" is intended to supply clock pulses from the output of the generator 14 clock pulses to the input of the shaper interval 17 in the period of time from the time of receipt at the first input element 15 "BAN" signal errors from the third output of the analyzer 5 of the syndrome through the second modulo-two 11 and the first element OR 12 until receipt at its second input the output signal of the second element OR 18.

The threshold counter 16 is designed to count quantities and the first element, OR 12, and issuance of the "error" signal in case of overflow. The threshold threshold counter 16 is selected on the basis of corrective properties quasiorthogonal convolutional code and the requirements for a valid probability transformation messages.

The shaper interval 17 is designed to establish the time frame of the analysis of the information received at the input threshold of the counter 16. As a shaper of the time interval counter 17 is used, the threshold of which is chosen based on the acceptable probability of transformation of messages, length of code restrictions and corrective ability quasiorthogonal convolutional code.

The second element 18 is designed for installation in the closed state of the element 15 "BAN" and reset threshold counter 16 and shaper of the time interval 17 in the case of receipt to the inputs of the OR element 18 of the overflow signal as the output threshold of the counter 16, and the output of the shaper interval 17.

The block 19 has been multiplied by the weighting factor is for multiplying the signals orthogonal inspections ANDion the corresponding weighting factors and summing signalisation inverting adder, built on the basis of the operational amplifier (3). The input unit 19 is connected to the second output of the analyzer 5 of the syndrome, and the output to the input of the threshold element 9.

The essence of the invention lies in the fact that with the introduction of new elements and relationships implemented new discipline functioning of the threshold decoder of the convolutional code, which is that the decision about the value of the noise symbol is based on the adoption of flexible solutions on the threshold element. In addition, by determining the values of the noise symbol correction of the correction signal from the output of the threshold element, which together allows you to fix most part three errors, which in turn increases the reliability of the decoding threshold decoder of the convolutional code.

Let the generating polynomial quasiorthogonal convolutional code has the form (2)

Pto(x) = Rabout(x) + Rg(x)xe(1)

For clarity, we consider quasiorthogonal convolutional code with rate R= 1/2, code restriction nAND=12, the minimum code distancemin=7 generating polynomial of the form (2):

Pkx)=x5+x4+x3+1+(x+1) x7=

= x8+x7+x5+x
S02=eabout1+f02;

S12=e11+f12;

S22=e21+f22;

S32=e01+f31+f32;

S42=e01+f11+f41+f42;

S52=e01+f11+f21+f51+f52. (3)

On the basis of characters of the syndrome in the syndrome analyzer 5 is formed orthogonal system of checks {Ak}, k= relative e10type 2:

AND1=S02= e01+f02;

AND2=S32=e01+e31+e32;

A3=e01+e11+e41+e42;

A4=S12+S52= e01+e21+e51+e12+ e52(4)

In the proposed device, the system checks {Ak} is supplied to the unit multiplied by a weighting factor, where each of the checks {A

The principle of formation of the coefficients presented in the table.

If you compare the weight of checks AND1and a2in the table, we see that W1<W. Therefore, the reliability of the symbol e01verification AND2influenced by a greater number of noise symbols than on the validity of the character than on the reliability of the symbol e01verification AND1. Therefore, the check value AND1greater than the value of the check AND2when deciding on a weighing of the threshold element in W2/W1time. Continuing this reasoning, based on the table, we get the system of equations of the form

(5)

Solving the expression (5) with respect to {Pk} checks {Ak}, get

P1=

P2=

P3=

P4=

Multiplied by the coefficients Pkcheck ANDk1=ANDkPkserved on the threshold element 9. (In this scheme, the selected threshold of Pn= ). If AiPiPnthe threshold is not exceeded and the output of the threshold element of the correction signal is not generated, i.e. = 0. If AiPi> Pnthen the output of the threshold element is formed by the correction signal = 1 , which through the element OR is lementa OR 12 and error corrector 4, at the first input of which receives the transformed information symbol Uo+e01. At the output of the error corrector 4 is formed by the signal Uo+e1o+= Uo. Transformation of communication no. As in the weighted system of checks {Ak1} the most important check AND1therefore, the requirements for its reliability higher than others. Therefore, it is necessary more likely to know the value of the symbol e02coming together with the check symbols for the second channel. Symbol of the syndrome of the form (3) in the driver checks 6 are formed two checks orthogonal symbol ep2of the form (6)

IN1=S02+S32=e02+e31+e32< / BR>
B2= S02+S12+S42= e02+e41+e12+e42, (6) served at the first input of the deciding circuit 7 (the element), the output of which, in case of receiving the second input enabling signal "1" from the OR element 8, will also form the correction signal = 1, which is a fourth element OR 13 flows into the feedback circuit. If a permissive signalerrors, the multiplicity does not exceed the correction ability orthogonal convolutional code, part quasiorthogonal convolutional code is error-free decoding of received messages. When at length code constraint errors, the multiplicity of which more corrective ability orthogonal convolutional code, part quasiorthogonal convolutional code is erroneous decoding of the message, in fact, the occurrence of decoding errors detected by the force of the decoding algorithm quasiorthogonal convolutional code (prototype).

The decoder operates as follows.

In the initial state of the shift registers of the first 1, the second 10 coders and the threshold counter 16 are in the zero state.

Let the link for information and testing the inputs of the proposed threshold decoder of the convolutional code with a clock period T receives a sequence containing three times the error e01e11e21leading to the transformation of the message. In accordance with ratios of the form (3) at the output of the shaper 3 syndrome si is formed;

S42=e01+e11=0; S32=e01=1;

S22=e21=1; S12=e11=1;

S02= e01= 1, which enters the analyzer 5 syndrome, where the formation of the system of checks {Ak} in accordance with the expressions (4), orthogonal relative to the first noise symbol e01of the form (8)

AND1=So2=1,

A2=S32=1,

A3=S42=0,

A4=S12+ S52=0. (8)

The system checks {Ak}, k = goes to the block 19 multiplied by a weighting factor, where the multiplication of each one to the corresponding ratio Rk, k = and is formed by the sum of AiPithat goes on the threshold element 9, which compares with a threshold of Pn= , i.e.

AiPi= 1 + 1 + O + 0 = > Pn< / BR>
At the output of the threshold element 9 is formed by the correction signal = 1, which, through the OR element 13 is supplied by the feedback circuit to the second inputs of the analyzer 5 syndrome, where the elimination of the influence of error correction and subsequent characters of the second modulo D. the information symbol Vo+e01. The output of the corrector 4 errors generated signal Uo+e1o+= Uo. Therefore, transformation of the symbol V0eliminated. This ends the operation of the device at this stage and a shift to the right information at one time. The device is ready for operation on the next cycle. Recorded in the analyzer 5 syndrome has the form S65S52S42S32S22S12001011. This generates the following system checks {Ak}, k =

AND1= 1, AND2=1; A3=0; A4=1, which is received in block 19 multiplied by a weighting factor and a further sum to the input of the threshold element 9

AiPi= 1 + 1 + O + 1 = > Pn< / BR>
The output is formed by the correction signal = 1, which, through the OR element 13 is supplied by the feedback circuit to the second inputs of the analyzer 5 syndrome, where the elimination of the influence of correcting errors on subsequent characters, the second modulo-two 11, the first element OR 12 and corrector 4 errors, at the first input of which receives the transformed symbol V1+e11. The output of the corrector 4 errors generated signal U1+e11+ = the ith step of the device works similarly. Formed syndrome: 111001 and system audits: IIII, there is a threshold AiPi> Pnand at the output of the threshold element 9 is formed by the correction signal = 1, which corrects incorrectly adopted the symbol U2+e12+= U1. Three times the error is completely corrected, the transformation of the messages does not occur.

Let the link for information and testing the inputs of the proposed convolutional code decoder receives a sequence containing three times the error e01e11e02. In accordance with ratios of the form (3) at the output of the shaper syndrome 3 forms by syndromic sequence: S52S42S32S22S12S02001010, which enters the analyzer 5 syndrome, where the formation of the system of checks {Ak} in accordance with the expressions (4), orthogonal relative to the first noise symbol e01A1=0; A2=1; A3=0; A4=1. The system checks {Ak}, k = goes to the block 19 multiplied by a weighting factor, where the multiplication of each one to the corresponding coefficient {Pkn= , i.e.

AiPi= 0 + 1 + 0 + 1 = < Pn,. at the output of the threshold element 9 the correction signal is not generated, i.e. = 0. Concurrently, the first output of the analyzer 5 syndrome in the imaging unit 6 checks form validation1=1, IN2=1, in accordance with expressions of the form (6), orthogonal with respect to the noise symbol e02that receives at the first input of the deciding circuit 7, to the second input of which receives an enable signal "1" from the output of the third element, OR 8, as2+A3+A4=1+0+1=1. Output decisive scheme, a signal is generated correction = 1, which, through uniting the fourth element OR 13 goes through the chain of back - ache due to the second inputs of the analyzer syndrome 5, where the elimination of the influence of correcting errors on subsequent characters, the second modulo-two 11, the first element OR 12 and corrector 4 errors, at the first input of which receives the transformed information symbol V0+e01. The output of the corrector 4 errors generated signal Uo+e1o+= Uo. The transformation of the character is eliminated. A shift to the right information at one time.

The device is ready for operation UB>2S32S22S12111001. System of checks {Ak}, k=;1=1; A2=1; A3=1; A4=1 is the threshold AiPi> Pnand at the output of the threshold element 9 is formed by the correction signal = 1, which is adjusted incorrectly adopted the symbol U1+e11+= U1. Three times the error is completely corrected, the transformation of the messages does not occur.

In the case of three errors that are not corrected by the proposed device, they are detected due to the positive properties of the prototype to detect errors in the proposed threshold decoder of the convolutional code.

Thus, if you had been transformed message when three or more mistake and she was found, now in the proposed device by introducing new elements and links corrected the most part three errors, and the rest three or more errors are detected. In order to fix the most part three mistakes using the previous device, it is necessary that the orthogonal convolutional code, which is part quasiorthogonal SUP>+1.

In this case nAND=36, R=1/2, which proves the achievement of the objectives of the invention.

Known threshold decoder of the convolutional code length code constraint nAND= 12 correcting all single and double errors, and 10 three-time errors, i.e.121+C122+10=12+66+10=88.

The rest of the errors higher ratio it was found.

Thus, a1= 298-88= 210 - number of uncorrectable combinations of errors on the code length constraint nA=12 in a known threshold decoder of the convolutional code.

At research of the proposed device was considered decoding all possible combinations of single, double and triple errors on the code length constraint nAND=12. The total number of combinations is C121+C122+C123=12+66+220=298.

While the proposed device was correct all single, double and 120 triple errors, other errors it found.

The THRESHOLD DECODER of the CONVOLUTIONAL CODE, containing the first encoder, the input of which is an information input of the decoder, the first and second outputs of the first encoder soedinenie with the first input of the shaper syndrome, the second input of which is to test the input of the decoder, the output of the shaper syndrome connected to the first input of the analyzer syndrome, the first output of which is connected to the first input of the second modulo two, the output of which is connected to the first input of the first element OR the first element OR is connected with the first input element of the BAN and the threshold counter whose output is the output error signal of the decoder and is connected to the first input of the second element OR the output of which is connected to the second inputs of the threshold counter and element PROHIBITION and the first input of the shaper time interval, the output of which is connected to a second input of the second element OR clock generator pulses, the output of which is connected with the third input element of the BAN, the output of which is connected to the second input of the shaper time interval, the output of the error corrector is connected to the input of the second encoder, the first output of which is an information decoder output, the second output is connected to a second input of the first modulo two, the second inputs of the offset error, the syndrome analyzer of the second modulo-two and the first element OR combined, and a threshold element, characterized in that the to multiplication the third and fourth elements OR second outputs of the syndrome analyzer connected to the inputs of the driver signal checks, the outputs of which are connected with the first inputs of the decisive scheme, the output of which is connected to the first input of the third element OR the third outputs of the syndrome analyzer connected to inputs of block multiplication, and the fourth element OR the output of which is connected to a second input of the decisive scheme, the outputs of block multiplication is connected to a second input of the third element OR the output of which is connected to the second input of the first element OR.

 

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