Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
  • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
  • H03M13/27—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes using interleaving techniques
  • H03M13/2703—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes using interleaving techniques the interleaver involving at least two directions
  • H03M13/2707—Simple row-column interleaver, i.e. pure block interleaving

Definitions

• Coding method • interleaving and corresponding method of deinterlacing - decoding.
• the field of the invention is that of digital transmissions, in particular to mobiles. More specifically, the invention relates to a coding-interleaving method as well as a deinterlacing - decoding method intended to be implemented in particular in a digital transmission system of the TDMA type (Multiple Time Division Access, or TDMA in Anglo-Saxon).
• TDMA Multiple Time Division Access
• TDMA is a technique whose principle consists in temporally sharing the entire transmission channel. In other words, in order to prevent the information from overlapping, there is only one station which transmits at a time and, when it transmits, it occupies the entire transmission channel.
• the information symbols to be transmitted are protected by adding judiciously determined redundancy symbols to them.
• This classic technique is called error control coding or channel coding.
• redundancy is used to correctly decode the symbols received, that is to say to correct any transmission errors.
• the information is transmitted in the form of blocks of coded symbols which are distributed (that is to say interleaved) in packets (or bursts in Anglo-Saxon) of several consecutive TDMA frames.
• the packets are first equalized and then deinterleaved in order to form coded received blocks which are then decoded, so as to find the transmitted information symbols.
• the quality of a packet after equalization is variable. Indeed, the transmission channel can undergo various disturbances, such as, in particular, the phenomena of rapid fading or of impulsive parasites, which induce blocks of errors in the packets.
• deinterlacing The role of deinterlacing is precisely to burst these blocks of errors, so that the decoding does not have to deal with blocks of errors which are too long and functions correctly.
• the error blocks can be such that, even when deinterleaved, they are split into sub-blocks of errors that are too long to allow correct decoding. These error sub-blocks then taint an even greater number of symbols contained in the packets.
• a known solution aimed at reducing the size of the error sub-blocks, consists in increasing the interleaving depth, that is to say the number of blocks used to build a packet.
• this known solution has the drawback of increasing the transmission delay, and therefore of reducing the quality of the transmission (in particular in the case of speech transmission).
• the invention particularly aims to overcome these various drawbacks of the state of the art.
• one of the objectives of the present invention is to provide a coding-interleaving method which, for an equivalent coding power, is less complex than the coding - interleaving methods of the prior art.
• the invention also aims to provide a deinterlacing - decoding method which allows correct decoding, even when there are blocks of errors, the importance of which is such that it is impossible to correct them with known methods. .
• Another object of the invention is to provide such a deinterlacing - decoding method which makes it possible to reduce the depth of interleaving, and therefore the transmission delay.
• a coding-interleaving process of a source sequence of information symbols to be transmitted making it possible to obtain at least two packets to be transmitted through a transmission channel and made up of said information symbols to be transmitted and redundancy symbols
• this method comprising the steps of: writing line by line (or column by column) of said information symbols to be transmitted from said source sequence in a base matrix, - storing said base matrix in a first quadrant of an extended emission matrix, performing a first coding according to columns of said base matrix, said first coding generating first redundancy symbols which are arranged in a second quadrant of said extended transmission matrix and constitute additional lines of said base matrix, of a second coding along lines of said base matrix, said second coding generating second redundancy symbols which are arranged in a third quadrant of said extended emission matrix and constitute additional columns of said base matrix, reading line by row (or column by column) of said extended emission matrix, each row (or column) of said extended matrix
• said first and second codings each use a separate block code.
• said coding-interleaving method also comprises a step of performing a third coding of at least some of said first and / or second redundancy symbols, said third coding generating third redundancy symbols which are arranged in a fourth quadrant of the extended transmission matrix. This protects the lines and / or the redundancy columns.
• said third coding is a coding belonging to the group comprising: coding, by a code identical to that used for said first coding and according to columns, of at least some of the second redundancy symbols; coding, by a code identical to that used for said second coding and along lines, of at least some of the first redundancy symbols; coding, by a code distinct from those used for said first and second codings and according to columns, of at least some of the second redundancy symbols; coding, by a code distinct from those used for said first and second codings and along lines, of at least some of the first redundancy symbols.
• a fourth quadrant of the extended emission matrix belongs to the group comprising: a fourth empty quadrant; and a fourth quadrant filled with predetermined fixed values.
• the invention also relates to a method of deinterlacing-decoding a received sequence consisting of at least two received symbol packets, making it possible to obtain a received sequence of transmitted information symbols, said received symbol packets being obtained by a coding-interleaving method as presented above and said deinterlacing-decoding method comprising the steps of: - construction of an extended reception matrix by arranging the symbols of the same packet received in the same row (or the same column ) of said extended reception matrix, production, according to columns of the first and second quadrants of said extended reception matrix, of a first decoding corresponding to said first coding, realization, along lines of the first and third quadrants of said extended reception matrix, of a second decoding corresponding to said second coding, reading line by line (or column by column) of the first quadrant of said extended reception matrix to form said sequence received, the chronological order
• the decoding carried out chronologically is done according to an element of matrix structure (row or column) of the same type as that in which the symbols of the same packet are stored during the stage of construction of a matrix of the deinterlacing process - decoding, this means that the decoding carried out first is equivalent to a decoding carried out on symbols which have neither been interleaved nor deinterleaved.
• the decoding carried out in second is then equivalent to a decoding carried out on symbols which have been interlaced but not yet deinterleaved.
• This first case is therefore chosen when the quality of the channel during the transmission of a packet is such that there are only small blocks of errors and it is therefore preferable to start by decoding together the symbols of this transmitted packet (symbols which are for example on the same line) then to decode together symbols of several successive packets
• This second case is therefore chosen when the quality of the channel during the transmission of a packet is such that there are large blocks of errors, and it is therefore preferable to start by decoding together symbols of several successive packets (symbols which are for example on the same column) then to decode together the symbols of the same transmitted packet (symbols which are for example on the same line) and comprising following the first correction (carried out in column), blocks d '' reduced size errors compared to the large error blocks originally existing.
• the invention is very different from conventional coding techniques - interleaving / deinterlacing - decoding. Indeed, in these conventional techniques, the different phases are successive.
• the source sequence of information symbols is coded, and it is the coded sequence which is interleaved in the form of packets. Furthermore, on reception, the received packets are deinterleaved so as to form a received coded sequence, and it is this received coded sequence which is decoded to give the received sequence of information symbols.
• the coding and the interleaving are nested, and on the reception, the deinterlacing and the decoding are also nested.
• the interleaving is carried out in part (namely the steps of writing in the basic matrix and of storing this basic matrix in the extended transmission matrix) before coding (namely the steps of producing the first and second codings), and in part (namely the step of reading the extended transmission matrix to constitute the packets) afterwards.
• the deinterlacing is carried out in part (i.e. the construction of the extended reception material) before decoding (i.e. the steps of first and second decoding), and in part (namely the step of reading the extended reception matrix to constitute the received sequence) after.
• said deinterlacing-decoding method also includes a step of performing a third decoding, said third decoding corresponding to said third coding and being carried out before the (first or second) decoding corresponding to the (first or second) coding having enabled obtaining the (first or second) redundancy symbols on which said third coding was carried out.
• the third decoding makes it possible to correct errors among the redundancy symbols, the redundancy symbols thus corrected then themselves allowing errors to be corrected among the symbols of the first quadrant of the extended reception matrix.
• the deinterlacing-decoding method comprises the steps of: construction of an extended reception matrix by arranging the symbols of the same packet received in the same row (or the same column) of said extended reception matrix , error detection, thanks to a first column decoding corresponding to said first coding, in each column of the first and second quadrants of the extended reception matrix, error detection, thanks to a second online decoding corresponding to said second coding, in each row of the first and third quadrants of the extended reception matrix, classification of the rows and columns of the extended reception matrix according to an increasing order of numbers of errors associated with said rows and columns, - correction of errors in the first element of said ranking thanks to said first decoding if said first element is a column or thanks to said second decoding if said first element is a line, said steps of classification and correction of errors being repeated with the lines and columns not corrected, up to that all the rows and columns are corrected, reading line by line (or column by column) of the first quadrant of said extended reception matrix to form said received sequence.
• a first step we use the capacity of the codes to detect errors
• a second step we use the capacity of the codes to correct detected errors.
• the classification during each iteration is modified if the corrections made previously on a row or column have resulted in a reduction in the number of errors in a row or column having elements in common with the corrected row or column.
• the codes used for the different codings are chosen in a predetermined manner.
• This predetermined choice is for example a function of the average characteristics of the channel and of the transmission system in which the method of the invention is implemented.
• the codes used for the different codings are chosen dynamically as a function of said information on the quality of said transmission channel.
• the method is of the type comprising, on transmission, a step of associating a predetermined training sequence with each packet of symbols to be transmitted, and, on reception, for each packet of symbols received, a step of estimating the impulse response of the transmission channel from a training sequence extracted from said received packet, and a step of equalizing the symbols of said packet received according to a estimated impulse response of the transmission channel, said equalization step delivering, for each symbol received, an estimated symbol and a confidence indicator associated with said estimated symbol, said information on the quality of said transmission channel belonging to the group comprising: information obtained from said estimate of the impulse response of the transmission channel; information obtained from an error rate on said training sequence extracted from a received packet; information obtained from confidence indicators associated with estimated symbols of a received packet.
• said packets of symbols received are obtained using a coding-interleaving method comprising the steps of: - writing line by line (or column by column) of said information symbols to be transmitted from said source sequence in a base matrix, storage of said base matrix in a first quadrant of an extended transmission matrix, - production of a first coding according to columns of said base matrix, said first coding generating first redundancy symbols which are arranged in a second quadrant of said extended emission matrix and constitute additional lines of said base matrix, - production of a second coding along lines of said base matrix, said second coding generating second redundancy symbols which are arranged in a third quadrant of said extended emission matrix and constitute additional columns of said matrix basic, - reading, either line by line or column by column of said extended transmission matrix as a function of information on the quality of said transmission channel, each line or column read from said extended transmission matrix constituting one of said packets to be transmitted, and said deinterlacing-decoding method comprises the steps of: - construction of an
• a packet is either a line or a column of the extended transmission matrix.
• this variant is equivalent, as regards the result, to the previous embodiment.
• a variable packet type (a packet is either a row or a column) with a fixed decoding order is equivalent to a fixed packet type with a variable decoding order (we start either with online decoding or by column decoding).
• FIG. 1 presents, in its upper part, a block diagram of a preferred embodiment of a coding - interleaving method according to the invention, and, in its lower part, a block diagram of a preferential embodiment of a deinterlacing - decoding method according to the invention
• FIG. 2A, respectively 2B presents an example of an extended transmission, respectively reception matrix, created during the implementation of the method presented on the upper, respectively lower, part of FIG. 1
• - Figures 3 and 4 each show a separate operating diagram corresponding to the preferred embodiment of the methods of the invention presented in Figure 1;
• FIG. 1 presents, in its upper part, a block diagram of a preferred embodiment of a coding - interleaving method according to the invention, and, in its lower part, a block diagram of a preferential embodiment of a deinterlacing - decoding method according to the invention
• FIG. 2A, respectively 2B presents an example of an extended transmission, respectively reception matrix, created during the implementation of the method presented on the upper, respectively lower, part of
• FIG. 5 presents a block diagram of a second, respectively third, preferred embodiment of a deinterlacing - decoding method according to the invention
• FIG. 7 presents an explanatory diagram of reception in a digital transmission system capable of implementing a method according to the invention
• Figures 8 and 9 each show a separate operating diagram corresponding to a variant of the preferred embodiment of the methods of the invention presented in Figure 1
• FIG. 10 presents a block diagram of another variant of the preferred embodiment of the deinterlacing - decoding method according to the invention presented in the lower part of FIG. 1.
• the invention therefore relates to a coding - interleaving method as well than a deinterlacing - decoding process.
• FIG. 1 presents a block diagram of a preferred embodiment of a coding-interleaving method according to the invention. This method makes it possible, from a source sequence 1 of information symbols to be transmitted, to obtain packets to be transmitted 2 made up of information symbols to be transmitted and of redundancy symbols.
• FIGS. 1 and 2A showing an example of an extended emission matrix created during the implementation of the above method
• the invention also relates to the case where the writing 3 and reading 7 steps are carried out column by column, each column of the extended transmission matrix then constituting a packet to be transmitted 2.
• FIG. 1 presents a block diagram of a preferred embodiment of a deinterlacing - decoding method according to the invention.
• the deinterlacing - decoding phase makes it possible, from received symbol packets 9, to obtain a received sequence 10 of transmitted information symbols.
• the symbols received 9 are obtained, on transmission, using the coding-interleaving method explained above in relation to the upper part of FIG. 1.
• the objective is to obtain a received sequence 10 equal to the source sequence 1.
• This deinterlacing-decoding method comprises the following steps (see also FIG. 2B which shows an example of an extended reception matrix): construction 11 of an extended reception matrix 22 ′ with L rows and C columns by arranging the symbols of the same received packet 9 in the same line or the same column depending on whether the writing 3 and reading 7 steps were carried out line by line or column by column of this extended reception matrix 22 ′.
• an extended matrix 22 ′ is recreated which, apart from the erroneous symbols due to the transmission in the channel 8, is identical to that created on transmission; realization, according to columns of the first I 'and second II' quadrants of the extended reception matrix 22 ', of a first decoding 12 corresponding to the first coding 5.
• This first decoding allows, thanks to the redundancy elements of the second quadrant II' , r'j with i € [1, Ls] and je [1, k], to correct errors among the symbols of the first quadrant F, x'i to x ' ⁇ ; realization, along lines of the first I 'and third ffl' quadrants of the extended reception matrix 22 ', of a second decoding 13 corresponding to the second coding 6.
• This second decoding allows, thanks to the redundancy elements of the third quadrant m' , t 'with ie [1, s] and j € [1, Ck], to correct errors among the symbols of the first quadrant I', x'j to x'sk; - reading 14 line by line or column by column (depending on the steps writing 3 and reading 7 were done line by line or column by column) of the first quadrant I 'of the extended reception matrix 22', to form the received sequence 10 of transmitted information symbols x 'ia Sk .
• the principle of the invention consists in choosing the chronological order of realization of the first 12 and second 13 decodings as a function of information 15 on the quality of the transmission channel 8. Different examples of calculation of this information 15 are presented by the continued in connection with Figure 7.
• the information 15 indicates that the quality of the transmission channel is very poor, it can be expected that the packets will contain long blocks of errors. Consequently, one chooses to start the decoding (first or second) which is not carried out according to elements (row or column) comprising symbols of the same packet.
• any type of code can be used.
• block codes are used.
• convolutional codes can also be used.
• FIG. 3 presents a first operating diagram of the method presented in FIG. 1 in the case where a packet 2 corresponds to a line of the extended transmission matrix 22 and to a line of the extended reception matrix 22 '.
• FIG. 4 presents a second operating diagram of the method presented in FIG. 1, in the case where a packet 2 corresponds to a column of the extended transmission matrix 22 and to a column of the extended reception matrix 22 '.
• the operation of the method consists in making the following choice: either the first decoding 12 precedes the second decoding 13, or it is the reverse.
• the fourth quadrant IV of the extended emission matrix 22 can be empty or filled with predetermined fixed values. But it is also possible to use the fourth quadrant IV.
• the coding - interleaving phase comprises an additional step of performing a third coding 51, 61 of some of the first and or second redundancy symbols ry and tj, j .
• This third coding 51, 61 makes it possible to generate third redundancy symbols p with ie [1, Ls] and j € [1
• third coding can in particular be: - case 1: a coding, by a code identical to that C i used for the first coding 12 and according to columns, second redundancy symbols tj , j .
• - case 1 a coding, by a code identical to that C i used for the first coding 12 and according to columns, second redundancy symbols tj , j .
• Ci Ci (, i, t2, i, .... t S ⁇ i)
• FIG. 5 corresponds to cases 2 and 4: the third coding 51 is carried out on the redundancy elements rj , j generated during the first coding 5.
• FIG. 6 corresponds to cases 1 and 3: the third coding 61 is carried out on the redundancy elements t; generated during the second coding 6.
• the deinterlacing-decoding method comprises an additional step of performing a third decoding 52, 62, so as to correct the redundancy symbols received corresponding to those on which the third coding 51, 61 was carried out.
• This third decoding 52, 62 is carried out before the coding corresponding to the coding which has made it possible to obtain the redundancy symbols on which the third coding 51, 61 has been carried out.
• the third coding 51 being performed on redundancy elements rj generated during the first coding 5
• the third coding 52 is carried out before the first decoding 12 (which corresponds to the first coding 5).
• FIG. 7 presents an explanatory diagram of the reception in a digital transmission system capable of implementing the methods of the invention.
• each packet of symbols to be transmitted includes additional symbols for start and end, as well as a predetermined learning sequence.
• This sequence is used in reception for synchronization, channel estimation and equalization. It is usually placed in the middle of the packet so as to minimize the fluctuations in the channel that the equalizer will have to process along the packet.
• a training sequence 72 is extracted and allows the estimation 73 of the impulse response of the transmission channel. Then, the useful symbols 74 of the received packet 71 are equalized 76 according to an estimate 75 of the impulse response of the channel determined previously.
• This equalization step 76 which has the role of reducing the interference between symbols tainting the symbols received, delivers, for each symbol received, an estimated symbol 77 (or decision) and a confidence indicator 78 associated with this estimated symbol 77 .
• the deinterlacing-decoding method 79 is carried out on estimated symbol packets 77 and makes it possible to obtain a received sequence 710 of transmitted information symbols.
• a first technique consists in using the estimate 75 of the impulse response of the channel.
• This estimate 75 is in the form of a set of coefficients. We can for example calculate the sum of the squares of these coefficients. The higher this sum, the better the estimate 75. Consequently, the equalization is more efficient and the received and equalized packets are of better quality.
• a second technique consists in using the learning sequence after equalization. In fact, on reception, the learning sequence is known a priori, and it is possible to calculate, by comparison, the error rate on the learning sequence after equalization. The lower this rate, the better the quality of the channel and therefore of the packets received and equalized.
• a third technique consists in using the confidence indicators 78 associated with the estimated symbols 77 of the received packets. For example, if the possible symbols are 0 and 1, the confidence indicators 77 can be integer values between -7 and +7. " -7 indicates a sure 0, and +7 a sure 1. 0 indicates an erasure, that is to say a symbol for which the equalizer prefers not to take a decision. One can for example calculate the average of the values absolute confidence indicators 77. The closer this average is to 7, the better the quality of the channel and therefore of the received and equalized packets.
• this third technique can be implemented both on the rows and on the columns of the extended reception matrix. It allows you to compare the quality of rows and columns, and therefore to correctly decide which decoding (in line or in column) to start.
• FIG. 10 presents a block diagram of a variant of the preferred embodiment of the deinterlacing-decoding method according to the invention presented in the lower part of FIG. 1.
• the deinterlacing-decoding method comprises the steps of : construction 101 of an extended reception matrix 22 ′ by arranging the symbols of the same received packet 9 in the same row (or the same column) of the extended reception matrix, - error detection 102, thanks to a first column decoding corresponding to the first coding, in each column of the first I 'and second W quadrants of the extended reception matrix 22', error detection 103, by virtue of a second online decoding corresponding to said second coding, in each line of the first V and third quadrant HV of the extended reception matrix 22 ', carrying out a classification 104 of the rows and columns of the extended reception matrix 22 'according to an increasing order of numbers of errors associated with the rows and columns, correction of errors 105 in the first element of said classification (that is to say the element containing the least number of errors), thanks to the first de
• FIGS. 8 and 9 each present a separate operating diagram corresponding to yet another variant of the embodiment of the methods of the invention presented in FIG. 1.
• this variant it is at transmission (and not at reception) that there is a choice, the chronological order of realization of the first and second decoding in reception being fixed.
• the choice on transmission as a function of information on the quality of the transmission channel, consists in determining whether a packet consists of a row or else of a column of the extended transmission matrix.
• the choice made in transmission (namely row or column) is retained. This choice can for example be transmitted by the packet itself, in a specific field.
• FIG. 8 presents a diagram of operation in the case where the line decoding 82 is always carried out before the decoding in column 83.
• a packet to be sent 81 is either a line 84 (represented in dotted lines) or a column 85 of the extended matrix transmission 22. The same choice is kept for the construction of the extended reception matrix. Then the line decoding 82 is carried out, before the column decoding. Thus, if the choice at the start is to put a line in each packet, but the quality of the overall decoding (that is to say of the set of two decodings, in line and in column) is poor, we reverse the choice on the show, and we put a column in each package.
• FIG. 9 simply presents the case where the column decoding 83 is always carried out before the online decoding 82.

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• 1994
  • 1994-03-15 FR FR9402988A patent/FR2717644B1/fr not_active Expired - Fee Related
• 1995
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