Method, apparatus, and program for demodulating data frames

Abstract

The invention relates to a method for demodulating a data frame comprising N information words, in which a word occupying a position i# in the frame is modulated by a symbol in a dictionary of K symbols, in which the method comprises the steps of determining (301), for a plurality of symbols and, with i,j#, a vector of K probabilities, called relative distribution, comprising the probabilities associated with the K possible values of the estimated difference between the symbols and; combining (303) the relative distribution with a specific probability distribution determined (302) from the characteristics of the channel; and demodulating (304) the frame on the basis of at least part of the combined distributions.

Description

Technical Field

[0001] This invention generally belongs to the field of telecommunications, and more specifically relates to a modulation technique for improving the demodulation performance of data frames, particularly in communication systems that are intended for transmission and / or processing based on the relative representation of information. Background Technology

[0002] Communication systems that transmit and / or process information based on its relative representation are known. A common example is the use of differential modulation.

[0003] For example, consider a symbol with 5 symbols The frame, each symbol encoded Each information bit is used to obtain the information. A possible differential representation of this frame could be: [value]. In this example, what is encoded is therefore the difference between values, and a single absolute reference is sufficient to decode the entire frame. Of course, in this configuration, within the finite domain considered (in this case, ), (that is, with) Subtraction or any other operation can be performed using the modulo operation.

[0004] This representation can be used for signal transmission or processing purposes within a communication chain. For example, it may be particularly effective for transmitting differences between samples when the variation between consecutive samples is small.

[0005] This differential representation of frames can also prove useful in some receivers, for example when receiving signals modulated by cyclic rotation of a complex symbol root sequence (such as CCSK (Cyclic Code Shift Keying) modulation).

[0006] CCSK modulation modulates the data to be transmitted via cyclic rotation / shifting of a sequence of complex symbols called the root sequence. The root sequence is designed such that its shifted versions are orthogonal to each other, i.e., it provides a good autocorrelation function. Therefore, a specific cyclic shift of a single root sequence is associated with each binary word to be transmitted.

[0007] For example, by selecting a root sequence consisting of four complex symbols [a; b; c; d], CCSK modulation allows two information bits to be orthogonally modulated by rotating this sequence. The binary word '00' can correspond to the transmission of the sequence [a; b; c; d]; the binary word '01' can correspond to the transmission of the sequence [d; a; b; c]; the binary word '10' can correspond to the transmission of the sequence [c; d; a; b], and so on.

[0008] CCSK sequences can be advantageously transmitted in CP-OFDM (Cyclic Prefix Orthogonal Frequency Division Multiplexing) frames, for example, in time-frequency frames, where each of the N time steps contains a complete CCSK sequence of size K distributed across all frequency subcarriers, such as... Figure 1 As shown.

[0009] The receiver knows the absolute shift of a specific sequence in the frame, which enables demodulation of the entire frame. For example, when the shift of the first sequence is known, such as when the specific sequence is present at the beginning of the frame by convention, the receiver can demodulate the frame by estimating the shifts of other sequences relative to the known sequence.

[0010] Therefore, to properly demodulate data, it is necessary to fully understand the differences between the sequences of individual frames. However, sometimes interference does not affect symbols transmitted in the same frame in the same way, and this can cause problems during demodulation. Specifically, in some cases, communication systems may experience changes in the communication channel over time. This is the case, for example, when the Doppler effect caused by relative motion between the receiver and transmitter is present. The higher the relative velocity between the transmitter and receiver, the faster this evolution of the channel occurs. A typical example is satellite communication, where the relative velocity under consideration may be particularly high.

[0011] Therefore, a method is needed to improve demodulation performance when interference on the channel has different effects on the symbols of a single frame (e.g., when the interference varies over time), and especially when communication is based on the relative representation of information. Summary of the Invention

[0012] Therefore, this invention proposes a method for demodulating N information words. The method for data frames, wherein the position occupying the frame is... The word Through having Symbols in a dictionary Modulation is performed, and the method includes the following steps:

[0013] - For multiple symbols in this frame and ,in Determine a vector of K probabilities This vector is called the relative distribution, which includes vectors corresponding to these symbols respectively. and The estimated difference between The probability associated with each possible value

[0014] - Relative distribution A specific probability distribution determined based on the characteristics of the communication channel. Combine them.

[0015] - Demodulate the frame based on at least some of these combined distributions.

[0016] The differences between symbol operations discussed in this document depend on the modulation technique used. In the case of CCSK modulation, this difference corresponds, for example, to the value of a cyclic shift of the considered sequence relative to another sequence. In the case of QPSK modulation, the difference operator is designed to estimate the phase shift or angular shift. The difference between symbols can also correspond to the difference between the index values ​​associated with symbols in the symbol dictionary (which, according to the indexing system, is equal to the set {0, 1, ..., K-1} in an isomorphic sense) and their corresponding probabilities. Therefore, this difference is estimated in a finite group of size K, that is, modulo the cardinality of the symbol dictionary when indexed in the form {0, 1, ..., K-1}.

[0017] Note that a group (in the mathematical sense of the term) is a set that has a single internal associative law and an identity element. A finite group is a group with a finite number of elements.

[0018] relative distribution Indicates the use of symbols when they are known. In the case of estimated channel, symbol Relative to symbols The probability of the relative value (and vice versa). Therefore, when the channel changes over time, for example, if the Doppler effect exists, and when these distributions... Received and When considering the impact of the correlation between the channels experienced, then for the OFDM frames spaced apart... and The values ​​of these distributions are not necessarily reliable.

[0019] According to another example, when considering time-invariant channels and multiple spatial layers (e.g., in MIMO (Multiple-Input Multiple-Output) systems using spatial multiplexing), the level of channel correlation between different layers affects the estimation of the difference between symbols. For example, in a system using four spatial layers, layers 1 and 4 may be slightly correlated, while layers 1 and 2, and layers 1 and 3 are completely decorrelated. Determining and applying an appropriate mask makes it possible to constrain highly unreliable distributions. The impact.

[0020] Therefore, this method proposes to combine the probability distribution of the difference between symbols in a frame with a mask distribution determined based on channel characteristics (the confidence level of symbol estimation or symbol difference estimation depends on these channel characteristics) in order to adjust the impact of certain probability distributions on the demodulation process.

[0021] The resulting relative distribution (which represents the probability of differences between symbols) is used to demodulate the information words of the frame. For example, when the receiver knows the symbols in the frame (such as pilot symbols), knowing the differences between the symbols allows for the demodulation of the complete frame. This method allows for assigning variable importance to these differences based on the reliability of their representative distribution. Demodulation performance is thus improved.

[0022] According to one particular embodiment, the demodulation of the frame is based on at least one partial relative distribution. To be executed, the relative distribution of at least one part is achieved by using symbols and The determined first combination of relative distribution and symbol-based and symbols The second combination is determined by associating it with the relative distribution, where, ,and .

[0023] Therefore, this invention proposes a method based on symbols. and The determined relative distribution of the mask and also based on the symbol and Determining the so-called partial relative distribution based on a given combination of relative distributions In other words, the difference between the first and second symbols is determined through transitivity, that is, based on the difference between the first and third symbols and the index difference between the second and the same third symbol. Therefore, multiple estimates of the index difference between the first and second symbols are obtained based on different symbols.

[0024] Then, for a specific value Determined relative distribution The relative distribution is obtained by combining the products through multiplication. The merged version, in which the impact of the unreliable distribution is considered negligible.

[0025] In a particular embodiment, a specific probability distribution It is based on the symbols and The reliability level is determined by the established reliability level and / or the reliability level determined by the difference between these symbols.

[0026] For example, these mask distributions are determined based on the reliability of symbol estimation and / or the reliability of inter-symbol bias estimation. In this way, a particular mask distribution can be determined that is configured to limit the impact of unreliable estimations and / or to give more importance to the most reliable symbols and / or the differences between symbols in the combined distribution.

[0027] According to a particular embodiment, when the symbol is made in the frame and When the number of separating symbols is less than a threshold, the relative distribution The relative distribution is convolved with a Kronecker distribution (denoted as Kronecker[0]) where the peak is at 0, and when the number is greater than or equal to the threshold, the relative distribution is convolved with a uniform distribution, which is determined according to the characteristics of the communication channel.

[0028] In this way, the difference between symbols spaced a certain distance apart in the frame is not considered for use in the demodulation process. For example, if the Doppler effect exists, symbols at the beginning and end of the frame will not experience the same channel because the latter changes over time. In this way, the method avoids introducing these unreliable estimates into the demodulation process. The threshold for suppressing the relative distribution is defined based on the characteristics of the communication channel.

[0029] According to a specific embodiment, the relative distribution With Kronek Distribution and uniform distribution probability distribution between Perform convolution so that ,parameter It is determined based on the characteristics of the communication channel.

[0030] This setup allows for the assignment of a specific distribution as desired during the demodulation step. The confidence level is used to finely adjust the degree of consideration for that particular distribution.

[0031] According to a specific embodiment, the probability distribution It is based on the symbols in that frame. and The number of symbols to be separated and the time-varying nature of the channel are used to determine this.

[0032] When the channel is affected by time variations (e.g., in the case of the Doppler effect), the symbols at the beginning and end of a frame are not affected the same way, thus it can be shown that the estimation differences between these symbols are unreliable. By determining a mask that takes into account both the distance between symbol pairs in the frame and the time-varying nature of the channel (e.g., Doppler level), the probability distribution with the lowest correlation can be eliminated, thereby improving demodulation performance.

[0033] According to a particular embodiment, in this method, the symbol By using the size of A complex sequence of values ​​obtained by applying a specific cyclic shift to the root sequence. In OFDM symbols Received on each subcarrier.

[0034] The information to be transmitted is modulated by cyclically shifting a root sequence known to the receiver. For example, this modulation is CCSK type modulation using a root sequence of the Zadoff-Chu type.

[0035] The CCSK sequence (or symbols) is integrated into a CP-OFDM frame, such that each element constituting the CCSK sequence (called a chip) is transmitted on a separate OFDM subcarrier. The time-frequency frame is then obtained in its simplest form, in which each of the N time steps contains a complete CCSK symbol of size K distributed across all frequency subcarriers, such as... Figure 1 As shown.

[0036] Since the receiver knows the root sequence (and therefore all its cyclic shifts), the transmitted CCSK sequence can then be used as a pilot sequence for synchronization and channel estimation while transmitting information.

[0037] Therefore, the calculated difference can correspond to the difference between the indices associated with the symbols, or to the difference between the shifts in the sequences that make up these symbols.

[0038] According to another aspect, the present invention relates to a method for demodulating a sequence of information words. The device that occupies a position in the data frame. The word Through having Symbols in a dictionary The device includes a processor coupled to a memory storing program instructions configured to perform the following steps: [The text abruptly ends here, so the translation stops as well.]

[0039] - For multiple symbols in this frame and ,in ,Sure A vector of probabilities This vector is called the relative distribution, which includes the symbols... and The probabilities associated with the K possible values ​​of the estimated difference between them.

[0040] - Relative distribution A specific probability distribution determined based on the characteristics of the communication channel. Combine them.

[0041] - Demodulate the frame based on at least some of these combined distributions.

[0042] The present invention also relates to a communication terminal including the demodulation device described above.

[0043] In one particular embodiment, the different steps of the demodulation method are determined by computer program instructions.

[0044] Therefore, the present invention also relates to a computer program comprising instructions adapted to perform the steps of the demodulation method as described above when the program is executed by a processor.

[0045] The program can use any programming language and can take the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form or in any other desired form.

[0046] The present invention also relates to a computer-readable information medium having a computer program stored thereon, the computer program including instructions for performing the steps of the demodulation method as described above.

[0047] The information medium can be any entity or device capable of storing programs. For example, the medium can include storage devices such as ROM (e.g., CD-ROM or microelectronic circuit ROM), flash memory, or magnetic recording devices (e.g., hard disk).

[0048] On the other hand, the information medium can be a transmissible medium, such as an electrical or optical signal, which can be routed via cable or fiber optic cable, radio, or other means. The program according to the invention can be downloaded, in particular, via the Internet.

[0049] Alternatively, the information medium may be an integrated circuit in which the program is incorporated, the circuit being designed to execute or used to execute the method in question.

[0050] The various embodiments or implementation features described above can be added individually or in combination to the steps of the demodulation method.

[0051] Devices, terminals, programs, and information media have advantages similar to those imparted by the methods to which they correspond. Attached Figure Description

[0052] Other features and advantages will become apparent when reading the preferred embodiments described with reference to the accompanying drawings, in which:

[0053] - Figure 1 An environment suitable for implementing the demodulation method according to a particular embodiment is shown.

[0054] - Figure 2The diagram illustrates a time-frequency frame in which each of the N time steps contains a complete symbol of size K distributed across all frequency subcarriers.

[0055] - Figure 3 This is a flowchart illustrating the main steps in a demodulation method according to a particular embodiment.

[0056] - Figure 4a This is a graph showing an example of a relative distribution.

[0057] - Figure 4b A graph depicting the Kronecker[0] distribution is shown.

[0058] - Figure 4c It illustrates a specific embodiment of the invention. Figure 4a and Figure 4b The graph shows the relative distribution produced by the convolution of the distribution shown.

[0059] - Figure 5a This is a graph showing an example of a relative distribution.

[0060] - Figure 5b A graph depicting a uniform distribution is shown.

[0061] - Figure 5c It illustrates a specific embodiment of the invention. Figure 5a and Figure 5b The graph shows the relative distribution produced by the convolution of the distribution shown.

[0062] - Figure 6a This is a graph showing an example of a relative distribution.

[0063] - Figure 6b A graph depicting an intermediate mask distribution between the Kronecker[0] distribution and the uniform distribution is shown.

[0064] - Figure 6c It illustrates a specific embodiment of the invention. Figure 6a and Figure 6b A graph showing the relative distribution produced by the convolution of the distribution shown, and

[0065] - Figure 7 This is a block diagram illustrating the architecture of a device suitable for implementing a demodulation method in a particular embodiment. Detailed Implementation

[0066] In the following description, embodiments are described based on non-limiting examples that enable the interpretation of the concepts upon which the invention is based. In particular, while the examples and terminology used may refer to certain well-known techniques or standards, these references are non-limiting, and other techniques may also be suitable for implementing the concepts of the invention. For example, the referenced CCSK modulation technique may be replaced by other modulation techniques (such as QPSK (Quadrature Phase Shift Keying) or QAM (Quadrature Amplitude Modulation)) without modifying the invention.

[0067] Figure 1 An environment suitable for implementing a demodulation method according to a particular embodiment is shown.

[0068] The environment includes a communication system 100, which includes a transmitting device 101 and a receiving device 102. The transmitting device 101 is, for example, a communication terminal, a user equipment (UE), a base station, a connected object, a telecommunications satellite, etc. The receiving device 101 is, for example, a user equipment, a terminal, a vehicle or a connected object, or any other device designed to receive wireless data.

[0069] Devices 101 and 102 include radio frequency communication devices, such as transceivers, which are designed to allow devices 101 and 102 to communicate by exchanging time-frequency data frames (e.g., CP-OFDM frames).

[0070] In one particular embodiment, such a frame includes multiple information words, for example, of size [missing information]. Unit-order binary words, these binary words are represented by CCSK symbols (i.e., by a function of size with good autocorrelation). The specific complex value sequence obtained by cyclically shifting the root sequence is modulated. Such a sequence is, for example, the Zadoff-Chu sequence.

[0071] Therefore, the communication system 100 implements CCSK-CP-OFDM modulation. The CCSK-CP-OFDM method combines CP-OFDM technology with CCSK modulation to achieve small packet communication for IoT with high energy efficiency. However, it can be noted that other modulation techniques, as indicated above, are conceivable without modifying the invention.

[0072] Figure 2 An example of a CCSK-CP-OFDM frame is shown, where each of the N time steps contains frames distributed across all... The size on each frequency subcarrier is The complete CCSK sequence allows each symbol to be encoded in a size of . The character for "position".

[0073] The set of CCSK sequences constitutes a cardinality. A dictionary of symbols.

[0074] In one particular embodiment, each symbol in the dictionary is associated with a separate index, making the dictionary... Each symbol is associated with Each index value is associated with a single value. In the case of CCSK modulation, each CCSK sequence in the dictionary can therefore be associated with a single numerical value representing the shift of that sequence relative to the root sequence.

[0075] According to one particular embodiment, symbols are associated with a dictionary. Each index value constitutes a size of finite group The finite group is equipped with an addition rule with zero as the identity element, such that each symbol in the dictionary is associated with a symbol belonging to the finite group. It is associated with individual values.

[0076] Therefore, operations on the index (especially summation and subtraction) are performed using the radix of the symbol dictionary. Modulo operation is used, provided that the elements are indexed in the form {0, 1, ..., K-1}, such that any difference (or sum) between elements in the set is equal to the sum of its components. The modulo operation also applies to values ​​belonging to that set.

[0077] In one particular embodiment, the index value is determined by the group. Definition, considering the following Modular arithmetic is performed on the remainder of the divisor, where, It is a strictly positive integer. It is a set of relative integers.

[0078] For example, in and In this case, obtain the index set [0, 2, 4, 6] such that any difference (or sum) between elements in this set is equal to 0. The modulo operation also belongs to the set of values. Therefore, in this example, we actually find that 0 – 2 = -2 [8] = 6, 0 – 4 = -4 [8] = 4, 2 – 4 = -2 [8] = 6, etc.

[0079] Now refer to Figure 3 This describes a specific embodiment of a demodulation method. The method, for example, is derived from... Figure 1 The equipment 102 in the middle is implemented.

[0080] In the first step 300, device 102 receives N information words. CCSK-CP-OFDM data frames, in which, occupying the position in this frame The word Through having CCSK sequences in the dictionary of sequences Modulation is performed. Therefore, for the position in the frame... Each symbol at the location And for dictionaries Each symbol in Determine the probability vector ,in, It is a location The symbol at the location is a symbol. The probability of . This distribution is determined, for example, by conventionally performing a cross-correlation operation between the symbol at position i and various symbols in the dictionary.

[0081] In step 301, device 102 determines the so-called relative symbol distribution based on the symbol distribution determined in step 300.

[0082] Due to each symbol in the frame It can be compared to a random variable X i The symbol probability distribution represents the two symbols in the frame, therefore... and The difference between them, within the meaning of this invention, is a difference random variable. The distribution of this difference random variable (called the relative distribution) is expressed as: .

[0083] For example, consider symbol frames as having a distribution law. Sequence of discrete random variables It is possible to construct a set containing differenced random variables. The matrix such that And the corresponding distribution can be constructed. The matrix such that ,in, It is a cross-correlation operator. Given the similarity between the concepts of summation and difference in the context of modular arithmetic operations in a finite field, it is also possible to define a set of random variables. The matrix such that And the corresponding distribution can be defined. The matrix such that ,in, This time it's the convolution operator. In this document, "relative distribution" "Indicates two random variables" and The distribution of the random variable generated by the difference (or sum).

[0084] Relative distributions represent the probabilities of differences between symbol pairs received in a frame. These relative distributions are generated for all symbol pairs in a frame through cross-correlation or convolution operations. ( It is certain. More precisely, the symbol. With symbols The difference between them is determined by associating these symbols through cross-correlation or convolution. This difference, for example, corresponds to the shift value between two CCSK sequences in a frame. Therefore, for each symbol... Determine the vector The size of this vector is equal to the cardinality K of the symbol dictionary, and each element in this vector... Including symbols and The relative shift between them has a value The probability of.

[0085] These relative distributions allow us to obtain a relative distribution matrix, in which the elements at coordinates (i, j) are relative distributions. :

[0086]

[0087] According to one particular embodiment, K symbols in the dictionary are associated with K distinct index values ​​of a K-order finite group, such that the difference between symbols is represented by the difference between the indices associated with them.

[0088] This method includes determining the dimensional mask matrix. Step 302, in which element It is Kronek Distribution, uniform Kronecker distribution Or a distribution between the Kronecker distribution and a uniform distribution, where a specific distribution is determined by the symbols assigned to the frame. and The choice is based on the difference in reliability levels between the two. For example, device 102 can obtain a value similar to the symbol. The associated transmission error rate and the symbol The associated transmission error rate is determined, and the distribution is determined based on the obtained error rate. The lower the error rate, the more similar the distribution is to Kronecker's distribution. The higher the error rate, the more the distribution resembles a uniform distribution.

[0089] According to a particular embodiment, each element of the mask matrix It is based on the symbols and The relative position within the frame and the degree of time-varying channel conditions determine this. Specifically, under certain conditions, especially when the channel undergoes time-varying changes (such as the Doppler effect), the reliability of the relative distribution will be related to the symbols within the frame. and The spacing is inversely proportional to the distance between them.

[0090] According to a particular embodiment, the elements of the mask matrix It is a distribution When the symbol is in that frame and When the number of delimiting symbols is less than a threshold, the distribution is Kronecker. The distribution is uniform when the difference is greater than or equal to the threshold. This threshold is determined based on the characteristics of the communication channel.

[0091] According to a particular embodiment, the elements of the mask matrix It is between Kronecker Distribution and uniform distribution Distribution between , making ,parameter It is based on the symbols in that frame. and The number of symbols used for separation is determined based on the characteristics of the communication channel (such as the time-varying nature of the channel).

[0092] One or more mask distributions can be determined by considering the different characteristics of the communication channel. This could be the time-varying degree of the channel, but is not limited to it. For example, in the case of a MIMO system, some layers may be particularly correlated while others are not, causing the symbols in the frame to be affected differently by the channel. Therefore, the mask distribution can be determined based on the correlation level between the layers of the MIMO system. The method includes step 303, during which the relative distribution matrix determined in step 301 is combined with the mask matrix determined in step 302 by convolution. Thus, each relative distribution... With mask distribution Perform convolution so that, based on the sign... and To assign reliability to the distribution, or reliability associated with the difference between these symbols. The importance of more or less.

[0093] The method concludes with a demodulation step 305, during which at least some of the relative distributions of the convolutions in step 304 are used to estimate the value of another symbol based on the symbol used as a reference.

[0094] For example, demodulation can be performed based on the probability of the difference between a symbol (e.g., a pilot symbol) with a known value and position in a frame and other symbols in the frame. The known reference symbol and the probability of the difference between that symbol and other symbols in the frame make it possible to estimate the values ​​of those other symbols.

[0095] According to another example, demodulation may include shift demodulation based on the merged relative distribution. Shift demodulation includes demodulating the frame by using an arbitrary symbol value as a reference, and performing an integrity check on the resulting information words. If the integrity check fails to verify the frame, a new demodulation is performed by using another symbol value as a reference, and a new integrity check is performed. These steps are repeated until the frame is verified through the integrity check.

[0096] In one particular embodiment, demodulation is performed based on recombined relative distributions, which are obtained by applying a mask and being based on symbols. and The determined at least one first relative distribution and the one already based on the symbol and symbols The second mask is obtained by associating it with a relative distribution, where... ,and .

[0097] In other words, the difference between the first and second symbols is determined through transitivity, that is, based on the difference between the first and third symbols and the index difference between the second and the same third symbol. Therefore, multiple so-called partial relative distributions can be obtained. They represent the difference between the first and second symbols, but based on different symbols.

[0098] Then, for a specific value Determined relative distribution The relative distribution is obtained by combining the products through multiplication. The demodulation steps are performed based on the merged version.

[0099] Figure 4a This shows a symbol dictionary for a base K = 5, representing the symbols in the data frame. and Relative distribution of the probability of the difference between them Example chart.

[0100] Figure 4b The mask distribution is depicted. [1, 0, 0, 0, 0] (i.e., Kronecker) A chart showing the distribution.

[0101] Figure 4c It is a demonstration Figure 4a Distribution in and Figure 4b A graph showing the convolution results of the mask distribution in the image. Therefore, the resulting distribution is... Figure 4a The original distribution is the same. In other words, it is the same as the Kronecker distribution. The convolution does not affect the distribution.

[0102] Figure 5a This shows a symbol dictionary for a base K = 5, representing the symbols in the data frame. and Relative distribution of the probability of the difference between them Example chart.

[0103] Figure 5b The mask distribution is depicted. A graph of [1 / 5, 1 / 5, 1 / 5, 1 / 5, 1 / 5] (i.e., a uniform distribution). This distribution is chosen, for example, to mask relative distributions that are considered unreliable.

[0104] Figure 5c It is a demonstration Figure 5a Distribution in and Figure 5b A graph showing the convolution results of the mask distribution in the image. The resulting distribution is uniform, which will have a neutral effect on demodulation.

[0105] Figure 6a This shows a symbol dictionary for a base K = 5, representing the symbols in the data frame. and Relative distribution of the probability of the difference between them Example chart.

[0106] Figure 6b The mask distribution is depicted. [0.6, 0.1, 0.1, 0.1, 0.1] (i.e., between Kronecker) A graph showing the distribution between the uniform distribution and the average distribution. This distribution is chosen, for example, to mask the relative distribution of average reliability.

[0107] Figure 6c It is a demonstration Figure 6a Distribution in and Figure 6b A graph showing the convolution results of the intermediate mask distribution. The resulting distribution narrows the gap between low and high probabilities, thus reducing the impact on demodulation.

[0108] Although this method is described here with reference to the discrete law, this scheme can also be applied, for example, by approximating the continuous law with the discrete law, or by using its parameters (e.g., the mean as a parameter of the normal law). and variance We can model the distribution to generalize to the continuity law. Therefore, it is appropriate to represent the relationship between the parameters of the relative distribution.

[0109] Figure 7 A simplified architecture of a device 700 suitable for implementing a demodulation method according to a particular embodiment is shown.

[0110] Device 700 includes a data processing module comprising a storage space 701 (e.g., memory (MEM)) and a processing unit 702 equipped with, for example, a microprocessor (PROC) and driven by a computer program (PGR) 703 whose instructions are configured to execute as referenced above. Figure 3 The demodulation method described.

[0111] During initialization, before the code instructions of computer program 703 are executed by the processor of processing unit 702, these code instructions are loaded into, for example, memory 701. The microprocessor of processing unit 702 executes the instructions of computer program 703 as described above. Figure 3 The steps of the demodulation method are described.

[0112] For this purpose, in addition to memory 701 and processor 702, the device also includes communication device 704, such as an OFDM transducer designed to receive signals on multiple orthogonal carriers. Communication device 704 is configured, for example, by computer program instructions to allow reception of at least one time-frequency frame (where each of N time steps contains complete symbols of size K distributed across all frequency subcarriers (e.g., CCSK sequences)) and demodulation of the received N OFDM symbols.

[0113] Device 700 also includes module 705 for determining a matrix (referred to as a relative distribution) comprising a set of probability distributions, where each element in the matrix... It has multiple symbol pairs representing the symbols that constitute the frame received by the communication device 704. ; The symbols in ) and A vector of K probabilities of at least one difference between them, where, ,and The difference is calculated based on modular arithmetic operations. Module 707 is implemented, for example, by computer program instructions configured to calculate the difference between index values ​​associated with two symbols in a frame through cross-correlation and / or convolution operations, and to combine a pair of sequences ( ; The result of the difference between the elements in the matrix is ​​stored as the coordinates in the matrix. Place.

[0114] Device 700 includes a tool for determining a set of distributions. The mask matrix module 706, these distributions are based on the symbol and The reliability level is determined by the reliability level of the symbol and / or the difference between these symbols. Module 706 can be implemented by program instructions configured to: when a symbol in a frame... and When the number of delimiting symbols is less than a threshold, assign Kronecker to the element at coordinates (i; j) of the matrix. The element is assigned a uniform distribution when the difference is greater than or equal to the threshold. This threshold is determined based on the time-varying nature of the channel. According to a particular embodiment, these program instructions are configured to assign elements (i; j) of the matrix between Kronecker... Distribution and uniform distribution The distribution between them makes ,parameter It is based on the symbols in that frame. and The number of symbols to be separated and the time-varying nature of the channel are used to determine this.

[0115] The device 700 also includes a module 707 for calculating the convolution of the relative distribution matrix determined by module 705 with the mask matrix determined by module 706. This module can be implemented by program instructions configured to calculate such convolution and produce the convolved relative distribution matrix, wherein the importance of these distributions is affected by the corresponding mask distribution.

[0116] The device 700 finally includes a demodulation module 708, which is designed to demodulate symbols transmitted in the received frame based on the relative distribution merged by module 707. For example, module 708 is implemented by program instructions designed to perform shift demodulation of the data frame based on a relative shift after convolution (e.g., based on a shift of one or more specific rows of the convolutional matrix). According to another example, these instructions are configured to demodulate the symbols based on the difference between the symbols in the frame and a reference symbol (whose position and value are known).

[0117] In one particular embodiment, device 700 is integrated into a communication terminal, a connected object, a vehicle, a gateway, an access point, a communication satellite, or a base station.

Claims

1. A method for demodulating including Information words The method for data frames, wherein... Occupy position in this frame The word Through having Symbols in a dictionary Modulation is performed, and the method includes the following steps: - For multiple symbols in this frame and ,in , confirmed (301) A vector of probabilities This vector is called the relative distribution, which includes the symbols... and The estimated difference between The probability associated with each possible value - Relative distribution The specific probability distribution (302) is determined based on the characteristics of the communication channel. Combine (303). - Demodulate (304) the frame based on at least some of these combined distributions.

2. The method as described in claim 1, wherein, The demodulation of this frame is based on at least one partial relative distribution. To be executed, the relative distribution of at least one part is achieved by using symbols and The determined first combination of relative distribution and symbol-based and the symbol The second combination is determined by associating it with the relative distribution, where, ,and .

3. The method as described in any of the preceding claims, wherein, Specific probability distribution It is based on the symbols and The reliability level is determined by the established reliability level and / or the reliability level determined by the difference between these symbols.

4. The method as described in any of the preceding claims, wherein, When the symbol is in that frame and When the number of separating symbols is less than a threshold, the relative distribution The relative distribution is convolved with a Kronecker distribution whose peak is at 0, and when the number is greater than or equal to the threshold, the relative distribution is convolved with a uniform distribution, the threshold being determined based on the characteristics of the communication channel.

5. The method according to any one of claims 1 to 3, wherein, relative distribution With Kronek Distribution and uniform distribution probability distribution between Perform convolution so that ,parameter It is determined based on the characteristics of the communication channel.

6. The method as described in any of the preceding claims, wherein, probability distribution It is based on the symbols in that frame. and The number of symbols to be separated and the time-varying nature of the channel are used to determine this.

7. The method as described in any of the preceding claims, wherein, In this method, the symbol By using the size of A complex sequence of values ​​obtained by applying a specific cyclic shift to the root sequence. In OFDM symbols Received on each subcarrier.

8. A method for demodulating N information words The device that receives data frames, wherein Occupy position in this frame The word Through having Symbols in a dictionary The device includes a processor (702) coupled to a memory (701) storing program instructions (703) configured to perform the following steps: - For multiple symbols in this frame and ,in ,Sure A vector of probabilities This vector is called the relative distribution, which includes the symbols... and The estimated difference between The probability associated with each possible value - Relative distribution A specific probability distribution determined based on the characteristics of the communication channel. Combine them. - Demodulate the frame based on at least some of these combined distributions.

9. A communication terminal, comprising the demodulation device as described in claim 8.

10. A computer program comprising instructions configured to perform the demodulation method as described in any one of claims 1 to 7 when executed by a processor.

11. A computer-readable information medium having stored thereon instructions configured to implement the demodulation method as described in any one of claims 1 to 7.

Images