A communication system based on forward error correction coding modulation

Abstract

The application provides a communication system based on forward error correction coding modulation, at a sending end, a uniformly distributed source sequence is subjected to Polar code coding, and then bit selection and redundancy insertion are performed on a polar code word through a BCDM algorithm, so that the symbol occurrence probability is adjusted, and shaping gain is obtained.The code word after the Polar code coding is sent to an 8-PAM modulator, so that three continuous bits are mapped into one 8-PAM symbol; and the modulated symbol with a target probability distribution is transmitted through an AWGN channel.At a receiving end, a demodulator demodulates the symbol probability into a bit Log-Likelihood Ratio (LLR); meanwhile, the inverse transformation of the BCDM algorithm is used to delete the redundant information in the bit LLR sequence, and a Polar code decoder corresponding to the Polar code encoder is used for decoding and estimating information bits; and the provision of the system guarantees the shaping gain of the coding modulation scheme, and realizes a low bit error rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of communication technology, in particular to a communication system based on forward error correction coding modulation. BACKGROUND

[0002] With the demand characteristics of users for low latency and high reliability of information, the combination of channel coding and high-order modulation has become an indispensable practical solution. The BCDM-based Polar coding modulation system scheme produces shaping gain by changing the probability distribution of channel input symbols. However, a small amount of redundant bits are added through the BCDM algorithm process, resulting in a loss of communication rate.

[0003] In view of this, the present application is proposed. SUMMARY

[0004] The present application discloses a communication system based on forward error correction coding modulation, aiming to improve the performance of the coding modulation system without increasing the complexity of the coding modulation system.

[0005] The first aspect of the present application provides a communication system based on forward error correction coding modulation, comprising:

[0006] A polar code encoder is configured to receive a random sequence generated by a signal source and encode the random sequence to generate a coded sequence;

[0007] A random number generator is configured to generate a pseudo-random number sequence according to a pseudo-random number seed agreed upon by a communication protocol;

[0008] A shaping code encoder is configured to perform bit selection and insert redundant bits on the coded sequence according to the pseudo-random number sequence and a bit selection condition to generate a selected signal;

[0009] A modulator is configured to modulate the selected signal based on a preset modulation order to achieve the expected distribution of channel input symbols.

[0010] Preferably, the random sequence is a binary random sequence subject to Bernoulli (1 / 2) distribution.

[0011] Preferably, the pseudo-random number sequence is a binary flag sequence flag subject to uniform distribution.

[0012] Preferably, the bit selection condition under PAM4 mapping is:

[0013] The length of the pseudo-random number sequence is L, and when i>L-1, two bits are sequentially taken out from the coded sequence and mapped as PAM4 symbols.

[0014] When the pseudo-random number sequence flag[i] = 0, one bit of the encoding sequence is sequentially taken out as the most significant bit b2 of the symbol, and b0 = b1 = flag[i] = 0 is set.

[0015] Preferably, the bit selection condition under the PAM8 mapping is:

[0016] When the pseudo-random number sequence flag[i] = 0, one bit of the encoding sequence is sequentially taken out as the most significant bit b2 of the symbol, and b0 = b1 = flag[i] = 0 is set.

[0017] When the pseudo-random number sequence flag[i] = 1, two bits of the encoding sequence are sequentially taken out as the significant bits b0, b2 of the symbol, and b1 = flag[i] = 1 is set.

[0018] When the pseudo-random number sequence flag[i] = 0, one bit of the encoding sequence is sequentially taken out as the most significant bit b2 of the symbol, and b0 = b1 = flag[i] = 0 is set.

[0019] Preferably, the bit selection condition under the PAM16 mapping is:

[0020] When the pseudo-random number sequence flag[i] = 0, three bits of the encoding sequence are sequentially taken out as the significant bits b3, b2, b1 of the symbol, and b0 = flag[i] = 0 is set.

[0021] When the pseudo-random number sequence flag[i] = 1, two bits of the encoding sequence are sequentially taken out as the significant bits b1, b3 of the symbol, and b0 = b2 = flag[i] = 1 is set.

[0022] When the pseudo-random number sequence flag[i] = 0, one bit of the encoding sequence is sequentially taken out as the most significant bit b2 of the symbol, and b0 = b1 = flag[i] = 0 is set.

[0023] Preferably, the shaping code encoder comprises a flag judging unit, a bit selection unit, and a bit combination unit.

[0024] The flag judging unit is configured to judge whether the flag[i] is empty or not, if not, the encoding sequence is subjected to bit selection, and if empty, three continuous code words of the encoding sequence are taken out to be combined to generate a bit group.

[0025] The bit selection unit is configured to sequentially take one bit from the encoding sequence as the most significant bit b2 of the symbol when flag[i] = 0, and add two bits 0 before b2 to form a three-bit group; and sequentially take two bits from the encoding sequence as the significant bits b0 and b2 of the symbol when flag[i] = 1, and insert one bit 1 between b0 and b2 to generate a bit group.

[0026] The bit combination unit is configured to combine the bit group generated by the judging unit and the bit group generated by the bit selection unit to generate a selection signal.

[0027] The second aspect of the present application provides a communication system based on forward error correction encoding modulation, comprising:

[0028] A demodulator is configured to demodulate the channel output signal into a sequence of bit log-likelihood ratios (LLRs);

[0029] A random number generator is configured to generate a sequence of pseudo-random numbers according to a pseudo-random number seed agreed upon by a communication protocol;

[0030] A shaping code decoder is configured to perform inverse processing of the bit LLRs according to the sequence of pseudo-random numbers by using a BCDM algorithm to delete redundant bits and generate a bit likelihood sequence.

[0031] A polar code decoder is configured to generate a source estimate value according to the bit likelihood sequence.

[0032] The communication system based on forward error correction encoding modulation provided by the present application, at the sending end, uniformly distributes the source sequence, encodes the source sequence by using a Polar code, performs bit selection and redundancy insertion on the Polar code word by using a BCDM algorithm, adjusts the symbol occurrence probability, and obtains shaping gain. The code word after the Polar code encoding is sent to an 8-PAM modulator to realize mapping of three consecutive bits into one 8-PAM symbol; the modulated symbol with the target probability distribution is transmitted through an AWGN channel. At the receiving end, a demodulator demodulates the symbol probability into a sequence of bit log-likelihood ratios (LLRs); at the same time, inverse transformation of the BCDM algorithm is used to delete the redundant information in the bit LLR sequence, a polar code decoder corresponding to the Polar code encoder is used for decoding and estimating the information bits; the proposed system guarantees the shaping gain of the encoding modulation scheme and realizes a low bit error rate. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a structure schematic diagram of the communication system based on forward error correction encoding modulation provided by the present application;

[0034] Figure 2is a 4-PAM constellation mapping schematic diagram corresponding to the BCDM algorithm provided by the application;

[0035] Figure 3 is an 8-PAM constellation mapping schematic diagram corresponding to the BCDM algorithm provided by the application;

[0036] Figure 4 is a 16-PAM constellation mapping schematic diagram corresponding to the BCDM algorithm provided by the application;

[0037] Figure 5 is a probability distribution diagram of channel input symbols under different flag bit lengths provided by the application;

[0038] Figure 6 is a Polar code encoding modulation system performance comparison diagram under 8-PAM modulation provided by the application. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0040] In order to better understand the technical solutions of the application, the embodiments of the application will be described in detail below with reference to the drawings.

[0041] It should be clear that the described embodiments are only some of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0042] The terms used in the embodiments of the application are only for the purpose of describing the specific embodiments, and are not intended to limit the application. The singular forms "a", "an" and "the" used in the embodiments of the application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0043] It should be understood that the term "and / or" used herein is only to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0044] Depending on the context, the word "if" as used herein can be interpreted to mean "when" or "while" or "in response to determining" or "in response to detecting." Similarly, the phrase "if it is determined" or "if [a stated condition or event] is detected" can be interpreted to mean "upon determining" or "in response to determining" or "upon detecting [the stated condition or event]" or "in response to detecting [the stated condition or event]."

[0045] The "first\second" mentioned in the embodiments are only to distinguish similar objects, and do not represent a specific order of the objects. Understandably, the "first\second" can be interchanged in a specific order or sequence as permitted. It should be understood that the objects distinguished by the "first\second" can be interchanged under appropriate circumstances, so that the embodiments described herein can be implemented in an order other than those illustrated or described herein.

[0046] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0047] The application discloses a communication system based on forward error correction coding modulation, aiming at improving the performance of the coding modulation system without increasing the complexity of the coding modulation system.

[0048] Please refer to Figure 1 The first aspect of the present application provides a communication system based on forward error correction coding modulation, comprising:

[0049] A polar code encoder 1 is configured to receive a random sequence generated by a source and encode the random sequence to generate a coded sequence.

[0050] It should be noted that in the embodiment, the source sequence generated by the source can be a random sequence, which can be a binary random sequence subject to Bernoulli (1 / 2) distribution. Of course, in other embodiments, other types of random sequences can also be used, wherein the process of encoding the random sequence by the polar code encoder 1 to generate a coded sequence is channel coding.

[0051] A random number generator 7 is configured to generate a pseudo-random number sequence according to a pseudo-random number seed agreed upon by a communication protocol.

[0052] It should be noted that in the embodiment, the pseudo-random number sequence can be a uniformly distributed binary flag sequence flag. Of course, in other embodiments, other types of pseudo-random number sequences can also be used.

[0053] A shaping code encoder 2 is configured to perform bit selection and insert redundant bits on the coded sequence according to the pseudo-random number sequence and bit selection conditions to generate a selected signal.

[0054] It should be noted that the bit selection condition under PAM4 mapping is as follows:

[0055] The pseudo-random number sequence has a length of L, and when i>L-1, two bits are sequentially taken from the encoding sequence to map into a PAM4 symbol;

[0056] The pseudo-random number sequence has a length of L, and when i<L, one bit is sequentially taken from the encoding sequence as the most significant bit b1 of the symbol, and b0 is set as flag[i], wherein i is the i-th bit in the flag sequence.

[0057] The bit selection condition under PAM8 mapping is as follows:

[0058] When the pseudo-random number sequence flag[i]=0, one bit is sequentially taken from the encoding sequence as the most significant bit b2 of the symbol, and b0=b1=flag[i]=0 is set;

[0059] When the pseudo-random number sequence flag[i]=1, two bits are sequentially taken from the encoding sequence as the significant bits b0 and b2 of the symbol, and b1=flag[i]=1 is set;

[0060] The pseudo-random number sequence has a length of L, and when i>L-1, three bits are sequentially taken from the encoding sequence to map into a PAM8 symbol, wherein i is the i-th bit in the flag sequence.

[0061] The bit selection condition under PAM16 mapping is as follows:

[0062] When the pseudo-random number sequence flag[i]=0, three bits are sequentially taken from the encoding sequence as the significant bits b3, b2 and b1 of the symbol, and b0=flag[i]=0 is set;

[0063] When the pseudo-random number sequence flag[i]=1, two bits are sequentially taken from the encoding sequence as the significant bits b1 and b3 of the symbol, and b0=b2=flag[i]=1 is set;

[0064] The pseudo-random number sequence has a length of L, and when i>L-1, four bits are sequentially taken from the encoding sequence to map into a PAM16 symbol, wherein i is the i-th bit in the flag sequence.

[0065] Further, in the embodiment, the shaping code encoder 2 can first determine whether flag[i] is empty or not;

[0066] When it is determined that flag[i] is empty, three consecutive code words are taken from the encoding sequence to combine to generate a bit group;

[0067] When it is determined that flag[i] is not empty, bit selection is performed on the encoded sequence, specifically:

[0068] When flag[i] = 0, take one bit sequentially from the encoding sequence as the most significant bit b2 of the symbol, and add two bits 0 before b2 to form a three-bit group;

[0069] When flag[i] = 1, two bits are sequentially taken from the encoding sequence as the effective bits b0 and b2 of the symbol, and a bit 1 is inserted between b0 and b2 to generate a bit group;

[0070] Finally, the generated bit groups are sequentially merged to generate the selection signal.

[0071] Modulator 3 is used to modulate the selected signal based on a preset modulation order to achieve the desired distribution of the input symbols.

[0072] It should be noted that the modulation order may include 4-PAM modulation (e.g., Figure 2 As shown), 8-PAM modulation (such as) Figure 3 As shown), 16-PAM modulation (such as...) Figure 4 As shown in the figure, in this embodiment, the modulation order is 8-PAM modulation. Specifically, it can be based on Gray mapping 8-PAM modulation, mapping three consecutive bits (x1x2x3) onto constellation points {±1,±3,±5,±7} to achieve the desired distribution of the channel input symbols. The modulated signal is transmitted through an AWGN channel represented by the channel model y=x+n, where x is the channel input symbol, n is a symbol with a mean of 0 and a variance of σ. 2 Gaussian noise, where the symbol probability distribution after 8-PAM modulation is as follows: Figure 5 As shown.

[0073] Please continue reading. Figure 1 A second aspect of the present invention provides a communication system based on forward error correction coding modulation, comprising:

[0074] Demodulator 6 is used to demodulate the channel output signal into a sequence of log-likelihood values ​​of bits;

[0075] Random number generator 7 is used to generate pseudo-random number sequences according to the pseudo-random number seed agreed upon in the communication protocol;

[0076] The forming code decoder 5 is used to perform inverse BCDM processing on the log-likelihood ratio of the bits based on the pseudo-random number sequence, so as to remove redundant bits and generate a bit likelihood sequence.

[0077] Polar code decoder 4 is used to generate source estimates based on the bit likelihood sequence.

[0078] The following compares the performance of the communication scheme of the embodiment with that of a conventional uniformly distributed symbol sequence, and simulation results are as shown in Figure 6 Fig. 8, where the Polar code length is 1024, the code rate is 0.75, and the flag bit length L is 256 and 170 respectively, the system performance of the embodiment under 8-PAM modulation and 16-QAM modulation is superior to that of other schemes, which proves the effectiveness of the BCDM algorithm in the embodiment in various Polar coding modulation systems, and proves that the embodiment is applicable to various modulations.

[0079] Based on the communication system provided by the embodiment, at the sending end, a uniformly distributed source sequence is encoded by a Polar code, and then the Polar code word is subjected to bit selection and redundancy insertion by the BCDM algorithm to adjust the symbol occurrence probability and obtain shaping gain. The code word after Polar coding is sent to an 8-PAM modulator to realize the mapping of three consecutive bits into one 8-PAM symbol; the modulation symbol with the target probability distribution is transmitted through an AWGN channel. At the receiving end, a demodulator demodulates the symbol probability into bit Log-Likelihood Ratio (LLR); at the same time, the inverse transformation of the BCDM algorithm is used to delete the redundant information in the bit LLR sequence, and a Polar decoder corresponding to the Polar encoder is used for decoding and estimating information bits; the proposed system guarantees the shaping gain of the coding modulation scheme and realizes low bit error rate.

[0080] The above only describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A communication system based on forward error correction coding modulation, characterized in that, Comprising: A polar code encoder, configured to receive a random sequence generated by a source and encode the random sequence to generate an encoded sequence; A random number generator, configured to generate a pseudo-random number sequence according to a pseudo-random number seed agreed upon by a communication protocol; A shaping code encoder, configured to perform bit selection and insert redundant bits on the encoded sequence according to the pseudo-random number sequence and bit selection conditions to generate a selection signal; wherein, the bit selection conditions under PAM4 mapping are: The length of the pseudo-random number sequence is L. When i > L - 1, two bits are sequentially taken out from the encoded sequence and mapped to a PAM4 symbol; The length of the pseudo-random number sequence is L. When i < L, one bit is sequentially taken out from the encoded sequence and mapped as the most significant bit b1 of the symbol, and b0 = flag[i] is set, where i is the i-th bit in the flag sequence; the bit selection conditions under PAM8 mapping are: When the pseudo-random number sequence flag[i] = 0, one bit is sequentially taken out from the encoded sequence as the most significant bit b2 of the symbol, and b0 = b1 = flag[i] = 0 are set; When the pseudo-random number sequence flag[i] = 1, two bits are sequentially taken out from the encoded sequence as the valid bits b0, b2 of the symbol, and b1 = flag[i] = 1 are set; The length of the pseudo-random number sequence is L. When i > L - 1, three bits are sequentially taken out from the encoded sequence and mapped to a PAM8 symbol, where i is the i-th bit in the flag sequence; the bit selection conditions under PAM16 mapping are: When the pseudo-random number sequence flag[i] = 0, three bits are sequentially taken out from the encoded sequence as the valid bits b3, b2, b1 of the symbol, and b0 = flag[i] = 0 are set; When the pseudo-random number sequence flag[i] = 1, two bits are sequentially taken out from the encoded sequence as the valid bits b1, b3 of the symbol, and b0 = b2 = flag[i] = 1 are set; The length of the pseudo-random number sequence is L. When i > L - 1, four bits are sequentially taken out from the encoded sequence and mapped to a PAM16 symbol, where i is the i-th bit in the flag sequence; A modulator, configured to modulate the selection signal based on a preset modulation order to achieve an expected distribution of channel input symbols; A demodulator, configured to demodulate a channel output signal into a sequence of log-likelihood values of bits; The random number generator is further configured to generate a pseudo-random number sequence according to a pseudo-random number seed agreed upon by a communication protocol; A shaping code decoder is further configured to perform an inverse process of BCDM on the log-likelihood ratio of the bits according to the pseudo-random number sequence to delete redundant bits and generate a bit likelihood sequence; A polar code decoder is further configured to generate a source estimate value according to the bit likelihood sequence.

2. The communication system based on forward error correction coding modulation according to claim 1, characterized in that, The random sequence is a binary random sequence subject to a Bernoulli 1 / 2 distribution.

3. A communication system based on forward error correction coding modulation according to claim 1, characterized in that, The pseudo-random number sequence is a uniformly distributed binary flag sequence flag.

4. A communication system based on forward error correction coding and modulation according to claim 1, characterized in that, The shaping code encoder includes a flag bit judgment unit, a bit selection unit, and a bit combination unit; The flag bit judgment unit is used to determine whether flag[i] is empty. If it is not empty, the bit selection is performed on the encoding sequence. If it is empty, three consecutive code words are taken out from the encoding sequence and combined to generate a bit group. The bit selection unit is used to sequentially extract one bit from the encoded sequence as the most significant bit b2 of the symbol when flag[i]=0, and add two bits 0 before b2 to form a three-bit group; When flag[i]=1, two bits are sequentially taken from the encoding sequence as the effective bits b0 and b2 of the symbol, and a bit 1 is inserted between b0 and b2 to generate a bit group; The bit combination unit is used to combine the bit group generated by the judgment unit and the bit group generated by the bit selection unit to generate a selection signal.

Images