CN114337933B - High-speed visible light communication system based on SCMA and self-adaptive coding and decoding method - Google Patents

High-speed visible light communication system based on SCMA and self-adaptive coding and decoding method Download PDF

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CN114337933B
CN114337933B CN202210254982.1A CN202210254982A CN114337933B CN 114337933 B CN114337933 B CN 114337933B CN 202210254982 A CN202210254982 A CN 202210254982A CN 114337933 B CN114337933 B CN 114337933B
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user
decoding
codebook
users
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CN114337933A (en
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余礼苏
刘超良
王玉皞
王正海
陈俊源
菅杰
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Nanchang University
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Abstract

The invention provides a high-speed visible light communication system based on SCMA and a self-adaptive coding and decoding method, which relate to the technical field of wireless communication, and the communication system comprises: the system comprises a signal sending end, a signal receiving end and a signal processing end, wherein the signal sending end is used for mapping bit signal streams of a plurality of users through a codebook and superposing the bit signal streams to synthesize a four-dimensional complex signal stream, and superposing and transmitting the complex signal stream; a visible light channel for transmitting the complex signal stream; and the signal receiving end is used for receiving the complex signal stream transmitted by the visible light channel and decoding the complex signal stream to obtain an original bit signal stream. The invention aims to reduce the complexity of the original MPA decoding algorithm to the maximum extent on the premise of ensuring the decoding accuracy.

Description

High-speed visible light communication system based on SCMA and self-adaptive coding and decoding method
Technical Field
The invention relates to the technical field of wireless communication, in particular to a high-speed visible light communication system based on a Single Chip Microcomputer (SCMA) and a self-adaptive coding and decoding method.
Background
After the development of 5G technology, people focus on the next generation mobile communication technology, i.e., 6G technology, which is expected to be used in visible light communication and non-orthogonal multiple access technologies. The visible light communication technology has the advantages of high safety, good confidentiality, strong anti-electromagnetic interference capability, integration of communication and illumination functions and no electromagnetic pollution. The SCMA (Sparse Code Multiple Access) technology is a non-orthogonal Multiple Access technology in which Multiple users share spectrum resources, and combines a Low Density Signature (LDS) technology and a Code Division Multiple Access (CDMA) technology together to solve the problem of system overload. The conventional SCMA decoding technique employs a Message Passing Algorithm (MPA), combines a priori probability, and iteratively updates a posteriori probability messages between user nodes and resource nodes using a factor graph, so as to decode codewords originally sent by each user as accurately as possible. Compared with a Maximum Likelihood (ML) detection method, although the algorithm complexity of the MPA decoder is reduced, the complexity increases exponentially with the number of users, so that the decoding efficiency is low, and the deployment requirement of a future 6G system cannot be met. In addition, for the multi-user detection of non-orthogonal multiple access, a technique called Successive Interference Cancellation (SIC) can also be adopted, the SIC decoding technique can greatly reduce the decoding complexity compared with the MPA decoding technique, and a great disadvantage of the SIC decoding technique is that the decoding performance is inferior to that of MPA, especially under the condition of high signal-to-noise ratio.
Aiming at the problem of high complexity brought by the MPA decoding algorithm, people also provide a plurality of improved MPA algorithms, such as algorithms for reducing the MPA decoding complexity, including an MPA algorithm based on a log domain, an MPA decoding algorithm based on a serial mode, an MPA decoding algorithm based on partial code words and the like.
Disclosure of Invention
Based on the above disadvantages of the decoding method, the present invention provides a high-speed visible light communication system and an adaptive encoding and decoding method based on SCMA, aiming at reducing the complexity of the original MPA decoding algorithm to the maximum extent on the premise of ensuring the decoding accuracy.
A first aspect of the present invention is to provide a SCMA-based high-speed visible light communication system, including:
the system comprises a signal sending end, a signal receiving end and a signal processing end, wherein the signal sending end is used for mapping bit signal streams of a plurality of users through a codebook and superposing the bit signal streams to synthesize a four-dimensional complex signal stream, and superposing and transmitting the complex signal stream;
a visible light channel for transmitting the complex signal stream;
and the signal receiving end is used for receiving the complex signal stream transmitted by the visible light channel and decoding the complex signal stream to obtain an original bit signal stream.
According to an aspect of the foregoing technical solution, the expression of the complex signal stream is:
Figure 566465DEST_PATH_IMAGE001
；
wherein,Jrepresent a sum ofJThe number of the individual users is increased by the number of the individual users,
Figure 467425DEST_PATH_IMAGE002
is shown as the firstiThe power allocated by the individual user;
Figure 92441DEST_PATH_IMAGE003
is shown asiThe complex signal stream transmitted by an individual user,xrepresenting the superimposed complex signal streams of the respective users.
According to an aspect of the foregoing technical solution, an expression of the complex signal stream after being decoded is:
Figure 686234DEST_PATH_IMAGE004
；
wherein,
Figure 295070DEST_PATH_IMAGE005
indicating that the receiving end receives the signal,
Figure 202983DEST_PATH_IMAGE006
representing a useriThe gain of the channel of (a) is,
Figure 10402DEST_PATH_IMAGE007
is shown asiThe complex signal stream transmitted by an individual user,
Figure 712779DEST_PATH_IMAGE008
is shown as the firstiThe power allocated to the individual user(s),nrepresenting the total additive white gaussian noise received
Figure 605648DEST_PATH_IMAGE009
。
A second aspect of the present invention is to provide an adaptive coding method applied to the SCMA-based high-speed visible light communication system described in the above technical solution, the method comprising:
when the channel condition is present
Figure 51673DEST_PATH_IMAGE010
When the temperature of the water is higher than the set temperature,
Figure 713599DEST_PATH_IMAGE011
codebook for selecting SIC decoding mode by threshold value representing channel condition
Figure 586877DEST_PATH_IMAGE012
Mapping and coding a bit signal of a user, specifically comprising:
according to a preset coding principle, a signal to be coded is set asX，XIs composed of
Figure 967043DEST_PATH_IMAGE013
A matrix; wherein,Von behalf of the number of users,Ntransmitted on behalf of each userMCarrying out number of the binary signals; and setting the symbol transmitted by each userAre all numberedNUser ofjCorresponding codebook is
Figure 951179DEST_PATH_IMAGE014
Wherein
Figure 733190DEST_PATH_IMAGE015
Represents one
Figure 777370DEST_PATH_IMAGE016
Three-dimensional array of which
Figure 644831DEST_PATH_IMAGE017
For the total number of resource blocks in the SCMA,
Figure 432659DEST_PATH_IMAGE018
represents one
Figure 69177DEST_PATH_IMAGE019
A two-dimensional array;
the code word obtained by the user through codebook mapping superposition is as follows:
Figure 284257DEST_PATH_IMAGE020
；
wherein
Figure 373436DEST_PATH_IMAGE022
Representing the superimposed composite codeword.
A third aspect of the present invention is to provide an adaptive coding method applied to the SCMA-based high-speed visible light communication system described in the above technical solution, the method comprising:
when the channel condition is present
Figure 964954DEST_PATH_IMAGE023
Selecting a codebook of MPA decoding scheme
Figure 455979DEST_PATH_IMAGE024
Mapping of user bit signalsThe encoding specifically includes:
according to a preset coding principle, a signal to be coded is set asX，XIs composed of
Figure 841961DEST_PATH_IMAGE025
A matrix; wherein,Von the behalf of the number of users,Ntransmitted on behalf of each userMCarrying out number of the binary signals; and the number of symbols transmitted by each user is set to beNUser ofjCorresponding codebook is
Figure 684015DEST_PATH_IMAGE026
Wherein
Figure 813645DEST_PATH_IMAGE027
Represents one
Figure 362438DEST_PATH_IMAGE028
Three-dimensional array of which
Figure 247217DEST_PATH_IMAGE029
Being the total number of resource blocks in the SCMA,
Figure 248671DEST_PATH_IMAGE030
represents one
Figure 244309DEST_PATH_IMAGE031
A two-dimensional array;
the code word obtained by the user through codebook mapping superposition is as follows:
Figure 382029DEST_PATH_IMAGE032
。
a fourth aspect of the present invention is to provide an adaptive decoding method applied to the SCMA-based high-speed visible light communication system described in the above technical solution, the method comprising:
when the channel condition is
Figure 437710DEST_PATH_IMAGE033
Selecting an SIC decoding mode, which specifically comprises the following steps:
calculating the codebook power of each user, performing descending sequencing on the codebook powers of all the users, and recording the arrangement sequence of the codebook powers of all the users;
decoding the codebook power in sequence according to the arrangement sequence of the codebook power of all users;
by means of a factor graph
Figure 926460DEST_PATH_IMAGE034
Inquiring the position of the resource block occupied by the decoding user at the moment specifically comprises the following steps:
Figure 460210DEST_PATH_IMAGE035
whereinkindicating the location where the user occupies the resource block,
Figure 718016DEST_PATH_IMAGE036
is shown as
Figure 944598DEST_PATH_IMAGE037
The user, expressed by the above formula, is
Figure 655065DEST_PATH_IMAGE037
Individual user is in the factor graph
Figure 992505DEST_PATH_IMAGE038
Position of occupied resource block is storedkIn the method, find represents a find query function in matlab software and is used for querying the position of a resource block occupied by each user;
decoding the first
Figure 370397DEST_PATH_IMAGE037
The signal transmitted by each user specifically includes:
Figure 502301DEST_PATH_IMAGE039
(ii) a Wherein m represents the symbol corresponding to the nth symbolThe decoded value norm represents norm function of norm in matlab software, min represents min minimum function in matlab software,
Figure 965643DEST_PATH_IMAGE041
which represents the signal received at the receiving end,
Figure 841195DEST_PATH_IMAGE042
representing the decoded recovered signal, n represents the nth signal,
Figure 339173DEST_PATH_IMAGE043
represents decoding tojThe nth signal sent by each user;
after decoding a signal of one user, removing the secondary received signal from the total received signal, specifically comprising:
Figure 579661DEST_PATH_IMAGE044
；
wherein,
Figure 592617DEST_PATH_IMAGE045
indicating that the receiving end receives the signal,kthe representation indicates the position of the resource block occupied by the user, and n indicates the nth signal.
A fifth aspect of the present invention is to provide an adaptive decoding method, wherein the adaptive decoding method is applied to the SCMA-based high-speed visible light communication system described in the above technical solution, and the method includes:
when the channel condition is present
Figure 6280DEST_PATH_IMAGE023
Then, selecting an MPA decoding scheme specifically includes:
initialization function node
Figure 93185DEST_PATH_IMAGE046
To the user node
Figure 35733DEST_PATH_IMAGE047
The probability value is specifically implemented as follows:
Figure 270406DEST_PATH_IMAGE048
wherein
Figure 425443DEST_PATH_IMAGE049
wherein
Figure 694751DEST_PATH_IMAGE050
representing functional nodes
Figure 277042DEST_PATH_IMAGE046
To the user node
Figure 999010DEST_PATH_IMAGE047
The initial probability of delivering a message is,kis shown in commonKOne of the resource blocks is a resource block,jis shown in commonJThe number of the individual users is increased by the number of the individual users,
Figure 957739DEST_PATH_IMAGE052
the initial probability is represented by a probability of being,
Figure 81553DEST_PATH_IMAGE047
is shown as
Figure 100324DEST_PATH_IMAGE054
The number of the individual user nodes is,
Figure 309589DEST_PATH_IMAGE046
is shown as
Figure 806429DEST_PATH_IMAGE056
A function node for each of the plurality of function nodes,
Figure 784749DEST_PATH_IMAGE057
representing a signal to be decoded by a user;
the functional node is updated, and the specific implementation is as follows:
Figure 974422DEST_PATH_IMAGE058
Figure 670983DEST_PATH_IMAGE059
；
wherein,
Figure 237093DEST_PATH_IMAGE060
representing user nodes
Figure 7603DEST_PATH_IMAGE047
To function node
Figure 430494DEST_PATH_IMAGE046
The updated probability of the delivery of the message,
Figure 552034DEST_PATH_IMAGE061
is shown in the factor graph
Figure 452994DEST_PATH_IMAGE062
To middlekThe position of the non-zero element in the row,
Figure 343590DEST_PATH_IMAGE063
is shown as
Figure 937382DEST_PATH_IMAGE054
The estimated signal of the individual user or users,
Figure 280639DEST_PATH_IMAGE064
which represents the variance of the noise, is,
Figure 250869DEST_PATH_IMAGE065
which represents the gain of the channel and is,tthe number of iterations is indicated and,
Figure 995971DEST_PATH_IMAGE066
indicating a received signal at a receiving end;
judging whether the maximum iteration number is reached
Figure 760665DEST_PATH_IMAGE067
If the maximum iteration times are reached, entering the next step, and if the maximum iteration times are not reached, continuously updating the resource nodes and the user nodes;
decoding the signal sent by each user, and specifically implementing the following steps:
Figure 591217DEST_PATH_IMAGE068
；
Figure 833980DEST_PATH_IMAGE069
；
Figure 699168DEST_PATH_IMAGE070
；
wherein
Figure 634763DEST_PATH_IMAGE071
Representing the bit signal finally decoded by decision,
Figure 952612DEST_PATH_IMAGE072
is shown in the factor graph
Figure 999065DEST_PATH_IMAGE073
To middlejThe position of the non-zero elements in the column,
Figure 718759DEST_PATH_IMAGE074
the maximum number of iterations is indicated,
Figure 825256DEST_PATH_IMAGE075
representing the signal to be judged, the judgment rule being a current expression
Figure 630400DEST_PATH_IMAGE076
Figure 480545DEST_PATH_IMAGE077
When the signal is true, the bit signal judged at the moment is 1, otherwise, the bit signal is judged to be 0, and finally, the signal obtained by judgment is obtainedNumber storing variable
Figure 320325DEST_PATH_IMAGE078
In (1).
Compared with the prior art, the high-speed visible light communication system based on the SCMA and the self-adaptive coding and decoding method have the advantages that:
1) aiming at a SCMA (Single chip multiple Access) assisted high-speed visible light communication system, a new channel condition-based adaptive coding and decoding strategy is provided;
2) the decoding complexity of the system can be obviously reduced to a great extent, and the error rate of the system can be properly reduced, so that the performance of the system can be integrally improved.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
FIG. 1 is a block diagram of an SCMA-based high-speed visible light communication system according to an embodiment of the present invention;
FIG. 2 is a system model diagram of adaptive encoding and decoding of a SCMA-based high-speed visible light communication system according to an embodiment of the present invention;
FIG. 3 is a flow chart of an adaptive coding method in a SCMA-based high-speed visible light communication system according to an embodiment of the present invention;
FIG. 4 is a flow chart of another adaptive decoding method in an SCMA-based high-speed visible light communication system according to an embodiment of the present invention;
FIG. 5 is a diagram illustrating simulation results of the performance of an adaptive codec system of the SCMA-based high-speed visible light communication system according to an embodiment of the present invention;
FIG. 6 is a partially enlarged view of a performance simulation result of an adaptive encoding and decoding system of a SCMA-based high-speed visible light communication system according to an embodiment of the present invention;
the following detailed description will further illustrate the invention in conjunction with the above-described figures.
Detailed Description
In order to make the objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. Several embodiments of the invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Example one
Referring to fig. 1-2, a first embodiment of the present invention provides a high-speed visible light communication system based on SCMA, which includes at least three parts, including an encoded signal transmitting end, a visible light channel, and a receiving and decoding end.
Wherein, at the signal transmitting end,Jshared by one userKFor better explaining the implementation principle of the present invention, the following system models share 4 resource blocks for 6 users, and the constituent expression of the transmission signal is as follows:
Figure 535406DEST_PATH_IMAGE079
specifically, the signals of 6 users are codebook-mapped, and then are superimposed and synthesized into a 4-dimensional complex signal stream, and the complex signal streams of the respective users are superimposed and transmitted. However, since the visible light communication can only use the intensity modulation/direct detection (IM/DD) method for signal transmission and conversion, the coded complex signal stream must be converted into a real-positive signal stream, and the hermitian symmetric transform is usually used. In the present embodiment, however, the ACO-OFDM technology is adopted to realize high-speed visible light communication. The generated 4-dimensional parallel complex signals are converted into serial signals in parallel and in series before the ACO-OFDM modulation, the signals after the ACO-OFDM modulation are converted into serial signals, the modulated signals are converted again, the dimensionality of the signals is the same as that of the signals after codebook mapping at the beginning, the converted 4-dimensional parallel signals are used for driving 4-primary-color LED lamps to transmit the signals, and therefore the purpose that the signals are transmitted is achievedJEach user shares 4 spectrum resource blocksAnd (4) sending a signal.
In the above embodiment, for the convenience of analysis, it is assumed that each user is signaled in the same visible light channel, so their channel conditions are the same, and they are all subjected to channel equalization.
Further, at the signal receiving end, after the transmission signal is transmitted through the visible light channel, the signal representation of the mixed noise after filtering by the optical filter and the ACO-OFDM demodulation is as follows:
Figure 624584DEST_PATH_IMAGE080
in the formula,
Figure 216103DEST_PATH_IMAGE081
representing a useriThe channel gain of (a) is determined,nrepresenting the total additive white gaussian noise received
Figure 707127DEST_PATH_IMAGE082
。
Example two
Referring to fig. 3, a second embodiment of the present invention provides an adaptive coding method, which indicates that a signal to be transmitted is adaptively selected to perform coding mapping according to the channel condition when performing SCMA coding mapping.
Wherein the channel condition adopts a quantization index signal-to-noise ratio
Figure 93109DEST_PATH_IMAGE083
According to the measurement, theoretical analysis and simulation verification show that a signal-to-noise ratio-error rate curve graph obtained by adopting a codebook suitable for SIC decoding in a SIC decoding mode and a signal-to-noise ratio-error rate curve graph obtained by adopting a codebook suitable for MPA decoding in an MPA decoding mode have an intersecting intersection point. The signal-to-noise ratio corresponding to the intersection point can be obtained from theoretical analysis, and the ratio of the received noise power to the received noise is used for quantifying the channel shapeIn condition of using
Figure 935163DEST_PATH_IMAGE083
Indicating that the signal-to-noise ratio is set as a threshold condition for distinguishing channel conditions
Figure 64793DEST_PATH_IMAGE084
Represent
In this embodiment, when the channel condition is satisfied
Figure 410324DEST_PATH_IMAGE085
Then, select the codebook of SIC decoding mode
Figure 232786DEST_PATH_IMAGE086
Mapping and coding a bit signal of a user, specifically comprising:
according to a preset coding principle, a signal to be coded is set asX，XIs composed of
Figure 296557DEST_PATH_IMAGE087
A matrix; wherein,Von behalf of the number of users,Ntransmitted on behalf of each userMCarrying out number of the system signals; and the number of symbols transmitted by each user is set to beNUser ofjCorresponding codebook is
Figure 964299DEST_PATH_IMAGE088
Wherein
Figure 429915DEST_PATH_IMAGE089
Represents one
Figure 423279DEST_PATH_IMAGE028
Three-dimensional array of which
Figure 708767DEST_PATH_IMAGE029
Being the total number of resource blocks in the SCMA,
Figure 711358DEST_PATH_IMAGE090
represents one
Figure 969164DEST_PATH_IMAGE031
A two-dimensional array;
the code word obtained by the user through codebook mapping superposition is as follows:
Figure 930167DEST_PATH_IMAGE091
；
wherein
Figure 906213DEST_PATH_IMAGE022
Representing the superimposed composite codeword.
Specifically, the adaptive encoding method shown in this embodiment includes:
step S1, when the channel condition is correct
Figure 243653DEST_PATH_IMAGE085
Then, through the codebook of SIC decoding mode
Figure 355966DEST_PATH_IMAGE092
Mapping and coding the bit signal of the user;
specifically, step S1 includes steps S11-S12:
step S11, according to the SCMA encoding principle, without loss of generality, assume that the signal to be encoded isX，XIs one
Figure 753449DEST_PATH_IMAGE087
Matrix of whichVWhich represents how many users there are,Ntransmitted on behalf of each userMNumber of binary signals, assuming that the number of symbols transmitted by each user isNUser ofjCorresponding codebook is
Figure 951212DEST_PATH_IMAGE088
；
Step S12, the code word obtained by the user through codebook mapping superposition is:
Figure 92344DEST_PATH_IMAGE093
。
in this embodiment, when the channel condition is satisfied
Figure 324742DEST_PATH_IMAGE094
Selecting a codebook of MPA decoding scheme
Figure 627547DEST_PATH_IMAGE024
Mapping and coding a bit signal of a user, specifically comprising:
according to a preset coding principle, a signal to be coded is set asX，XIs one
Figure 578186DEST_PATH_IMAGE087
Matrix of whichVWhich represents how many users there are,Ntransmitted on behalf of each userMNumber of binary signals, assuming that the number of symbols transmitted by each user isNUser ofjCorresponding codebook is
Figure 257429DEST_PATH_IMAGE095
；
The user obtains the code word by mapping and superposing the codebook into
Figure 344333DEST_PATH_IMAGE096
。
Specifically, the adaptive encoding method shown in this embodiment includes:
step S2: when the channel condition is
Figure 818040DEST_PATH_IMAGE094
Codebook of time-multiplexed MPA decoding scheme
Figure 990395DEST_PATH_IMAGE024
Mapping and coding the bit signal of the user;
specifically, step S2 includes steps S21-S22:
step S21, according to SCMA encoding principle without loss of generality, assume the signal to be encoded isX，XIs one
Figure 473329DEST_PATH_IMAGE087
Matrix therein ofVWhich represents how many users there are,Ntransmitted on behalf of each userMNumber of binary signals, assuming that the number of symbols transmitted by each user isNUser ofjCorresponding codebook is
Figure 414741DEST_PATH_IMAGE097
；
Step S22, the user obtains the code word by the superposition of codebook mapping
Figure 324928DEST_PATH_IMAGE098
。
EXAMPLE III
Referring to fig. 4, a third embodiment of the present invention provides an adaptive decoding method for decoding a signal by using a suitable decoding algorithm to recover an original bit stream.
In this embodiment, when the channel condition is satisfied
Figure 984579DEST_PATH_IMAGE099
Then, selecting a SIC decoding mode, which specifically includes:
calculating the codebook power of each user, performing descending sequencing on the codebook powers of all the users, and recording the arrangement sequence of the codebook powers of all the users;
according to the arrangement sequence of the codebook power of all users, decoding the codebook power in sequence;
by a factor map
Figure 208887DEST_PATH_IMAGE034
Inquiring the position of the resource block occupied by the decoding user at the moment specifically comprises the following steps:
Figure 332701DEST_PATH_IMAGE035
wherein
Figure 351472DEST_PATH_IMAGE100
to representFirst, the
Figure 295158DEST_PATH_IMAGE101
A user, and will
Figure 57577DEST_PATH_IMAGE036
Individual user is in the factor graph
Figure 35898DEST_PATH_IMAGE034
Position of occupied resource blockkPerforming the following steps;
decoding the first
Figure 225571DEST_PATH_IMAGE102
The signal transmitted by each user specifically includes:
Figure 945569DEST_PATH_IMAGE039
；
after decoding a signal of one user, removing the secondary received signal from the total received signal, specifically comprising:
Figure 246100DEST_PATH_IMAGE044
。
specifically, the adaptive decoding method shown in this embodiment includes:
step S1: when the channel condition is
Figure 78927DEST_PATH_IMAGE103
Then, we select SIC decoding mode;
specifically, step S1 includes steps S11-S16:
step S11, obtaining codebook power of each user;
step S12, sorting the codebook power of the user in descending order and recording the arrangement order of the codebook power;
step S13, decoding is carried out in sequence according to the power arrangement sequence of the codebook;
step S14, passing through the factor graph
Figure 439501DEST_PATH_IMAGE034
Finding out the position of the resource block occupied by the decoding user at the moment, the implementation method is as follows:
Figure 357778DEST_PATH_IMAGE035
here, the
Figure 462001DEST_PATH_IMAGE037
Is shown as
Figure 414913DEST_PATH_IMAGE037
A user, here will be
Figure 946389DEST_PATH_IMAGE037
Individual user is in factor graph
Figure 351962DEST_PATH_IMAGE034
The position of the occupied resource block is storedkThe preparation method comprises the following steps of (1) performing;
step S15, decoding the first
Figure 994296DEST_PATH_IMAGE037
The signal transmitted by each user is specifically realized as follows:
Figure 4977DEST_PATH_IMAGE039
；
step S16, after decoding a signal of a user each time, removing the secondary received signal from the total received signal to reduce interference to the next user to be detected, which is specifically implemented as follows:
Figure 769671DEST_PATH_IMAGE044
here, the signal of each user needs to be detected before entering the next round of signal detection, that is, the detection is sequential and cannot be skipped.
In this embodiment, when the channel condition is satisfied
Figure 396962DEST_PATH_IMAGE094
Then, selecting an MPA decoding scheme specifically includes:
the probability value from the function node to the user node is initialized, and the specific implementation is as follows:
Figure 842986DEST_PATH_IMAGE048
wherein
Figure 770491DEST_PATH_IMAGE049
whereinkis shown in commonKOne of the resource blocks is a resource block,jis shown in commonJA user;
the functional node is updated, and the specific implementation is as follows:
Figure 909348DEST_PATH_IMAGE104
Figure 961618DEST_PATH_IMAGE059
wherein
Figure 273651DEST_PATH_IMAGE105
is shown in the factor graph
Figure 993345DEST_PATH_IMAGE106
To middlekThe position of a non-zero element in a row;
judging whether the maximum iteration number is reached
Figure 99841DEST_PATH_IMAGE067
If the maximum iteration times are reached, entering the next step, and if the maximum iteration times are not reached, continuously updating the resource nodes and the user nodes;
decoding the signal transmitted by each user, which is specifically implemented as follows:
Figure 639407DEST_PATH_IMAGE068
；
Figure 489551DEST_PATH_IMAGE107
；
Figure 63752DEST_PATH_IMAGE070
；
specifically, the adaptive decoding method shown in this embodiment includes:
step S2, when the channel condition is correct
Figure 341150DEST_PATH_IMAGE108
Here we select MPA decoding mode;
specifically, step S2 includes steps S21-S25:
step S21, initializing function node
Figure 633591DEST_PATH_IMAGE046
To the user node
Figure 21847DEST_PATH_IMAGE047
The probability values are specifically implemented as follows:
Figure 716133DEST_PATH_IMAGE048
here, the
Figure 164432DEST_PATH_IMAGE049
Wherein
Figure 678590DEST_PATH_IMAGE050
representing functional nodes
Figure 870537DEST_PATH_IMAGE046
To the user node
Figure 419330DEST_PATH_IMAGE047
The initial probability of delivering a message is,kis shown in commonKA number of resource blocks, each of which is a number of resource blocks,jis shown in commonJThe number of the individual users is increased by the number of the individual users,
Figure 38530DEST_PATH_IMAGE052
the initial probability is represented by a probability of being,
Figure 305564DEST_PATH_IMAGE047
is shown as
Figure 238884DEST_PATH_IMAGE054
The number of the individual user nodes is,
Figure 438922DEST_PATH_IMAGE046
is shown as
Figure 229023DEST_PATH_IMAGE056
A function node for each of the plurality of function nodes,
Figure 983352DEST_PATH_IMAGE057
representing a signal to be decoded by a user;
step S22, updating the functional node, specifically implementing as follows:
Figure 720364DEST_PATH_IMAGE058
Figure 40487DEST_PATH_IMAGE059
；
wherein,
Figure 939173DEST_PATH_IMAGE060
representing user nodes
Figure 977536DEST_PATH_IMAGE047
To function node
Figure 252660DEST_PATH_IMAGE046
The updated probability of the delivery of the message,
Figure 427289DEST_PATH_IMAGE061
is shown in the factor graph
Figure 762456DEST_PATH_IMAGE062
To middlekThe position of the non-zero element in the row,
Figure 22536DEST_PATH_IMAGE063
is shown as
Figure 101350DEST_PATH_IMAGE054
The estimated signal of the individual user or users,
Figure 130486DEST_PATH_IMAGE064
which represents the variance of the noise, is,
Figure 636554DEST_PATH_IMAGE065
which represents the gain of the channel and is,tthe number of iterations is indicated and,
Figure 383930DEST_PATH_IMAGE066
indicating a received signal at a receiving end;
step S23, updating the user node, which is specifically implemented as follows:
Figure 856DEST_PATH_IMAGE109
here, the
Figure 150078DEST_PATH_IMAGE110
Is shown in the factor graph
Figure 827047DEST_PATH_IMAGE073
To middle
Figure 61719DEST_PATH_IMAGE112
The position of a non-zero element in a column;
step S24, judging whether the maximum iteration number is reached
Figure 482336DEST_PATH_IMAGE067
If the maximum iteration times are reached, entering the next step, and if the maximum iteration times are not reached, continuously updating the resource nodes and the user nodes;
step S25, decoding the signal sent by each user, which is specifically implemented as follows:
Figure 689326DEST_PATH_IMAGE068
；
Figure 333934DEST_PATH_IMAGE069
；
Figure 55903DEST_PATH_IMAGE070
。
in summary, by using the adaptive coding and decoding method of the present invention, two different sets of codebook combinations can be generated for a SCMA-based high-speed visible light communication system in which 6 users share 4 spectrum resource blocks, wherein the coding codebook optimized by SIC decoding is used, and the coding codebook optimized by SIC decoding is used
Figure 14631DEST_PATH_IMAGE113
Representing the code codebook optimized by MPA decoding
Figure 138445DEST_PATH_IMAGE114
And (4) showing. FIGS. 5 and 6 show two sets of codebook combinations constructed
Figure 157217DEST_PATH_IMAGE115
And
Figure 304164DEST_PATH_IMAGE116
constructed codebook combinations
Figure 128901DEST_PATH_IMAGE086
And
Figure 44904DEST_PATH_IMAGE114
the performance curve obtained by adaptive coding and decoding can be seen from the simulation results obtained in fig. 5 and 6
Figure 296894DEST_PATH_IMAGE117
The performance of the decoding algorithm using SIC is indeed better than that of the decoding algorithm using MPA
Figure 665558DEST_PATH_IMAGE108
The performance of the MPA decoding algorithm is actually better than that of the SIC decoding algorithm; therefore, from the simulation result level, the self-adaptive coding and decoding method provided by the invention is reasonable and can be realized, and self-adaptive coding and self-adaptive decoding are carried out according to the channel condition, so that the error rate of system decoding is reduced, and the decoding complexity of the system is also reduced.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The above examples only show several embodiments of the present invention, and the description thereof is specific and detailed, but not to be construed as limiting the scope of the present invention. It should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the spirit of the invention, and these changes and modifications are all within the scope of the invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (5)

1. A SCMA-based high-speed visible light communication system, the communication system comprising:
the system comprises a signal sending end, a signal receiving end and a signal processing end, wherein the signal sending end is used for mapping bit signal streams of a plurality of users through a codebook and superposing the bit signal streams to synthesize a four-dimensional complex signal stream, and superposing and transmitting the complex signal stream;
a visible light channel for transmitting the complex signal stream;
a signal receiving end, configured to receive the complex signal stream transmitted through the visible light channel, and decode the complex signal stream to obtain an original bit signal stream;
the signal transmitting end is specifically configured to:
when the channel condition is present
Figure 491982DEST_PATH_IMAGE001
When the temperature of the water is higher than the set temperature,
Figure 747514DEST_PATH_IMAGE002
codebook for selecting SIC decoding mode by threshold value representing channel condition
Figure 262809DEST_PATH_IMAGE003
Mapping and coding a bit signal of a user, specifically comprising:
according to a preset coding principle, a signal to be coded is set asX，XIs composed of
Figure 513662DEST_PATH_IMAGE004
A matrix; wherein,Von the behalf of the number of users,Ntransmitted on behalf of each userMCarrying out number of the binary signals; and the number of symbols transmitted by each user is set to beNUser ofjCorresponding codebook is
Figure 980678DEST_PATH_IMAGE005
Wherein
Figure 316981DEST_PATH_IMAGE006
Represents one
Figure 901546DEST_PATH_IMAGE007
Three-dimensional array of which
Figure 882272DEST_PATH_IMAGE008
For the total number of resource blocks in the SCMA,
Figure 628511DEST_PATH_IMAGE009
represents one
Figure 452110DEST_PATH_IMAGE010
A two-dimensional array;
the code word obtained by the user through codebook mapping superposition is as follows:
Figure 699421DEST_PATH_IMAGE011
；
wherein,
Figure 659287DEST_PATH_IMAGE012
is shown asjA user transmitsiAnMA binary digital signal;
or, when the channel condition
Figure 576427DEST_PATH_IMAGE013
Selecting a codebook of MPA decoding scheme
Figure 28268DEST_PATH_IMAGE014
Mapping and coding a bit signal of a user, specifically comprising:
according to a preset coding principle, a signal to be coded is set asX，XIs composed of
Figure 689057DEST_PATH_IMAGE015
A matrix; wherein,Von the behalf of the number of users,Ntransmitted on behalf of each userMCarrying out number of the binary signals; and the number of symbols transmitted by each user is set to beNUser ofjCorresponding codebook is
Figure 503429DEST_PATH_IMAGE016
Wherein
Figure 748728DEST_PATH_IMAGE017
Represents one
Figure 281340DEST_PATH_IMAGE007
Three-dimensional array of which
Figure 745820DEST_PATH_IMAGE008
Being the total number of resource blocks in the SCMA,
Figure 414698DEST_PATH_IMAGE018
represents one
Figure 80166DEST_PATH_IMAGE010
A two-dimensional array;
the code word obtained by the user through codebook mapping superposition is as follows:
Figure 100075DEST_PATH_IMAGE019
；
wherein,
Figure 102666DEST_PATH_IMAGE012
is shown asjA user transmitsiAnMA binary digital signal.
2. A SCMA-based high speed visible light communication system according to claim 1 wherein the complex signal stream is expressed as:
Figure 281843DEST_PATH_IMAGE020
；
wherein,Jrepresent a sumJThe number of the individual users is increased by the number of the individual users,
Figure 977267DEST_PATH_IMAGE021
is shown asiThe power allocated by the individual user;
Figure 218892DEST_PATH_IMAGE022
is shown asiThe complex signal stream transmitted by an individual user,xrepresenting the superimposed complex signal streams of the respective users.
3. The SCMA-based high-speed visible light communication system according to claim 1, wherein the complex signal stream after being decoded is expressed as:
Figure 166120DEST_PATH_IMAGE023
；
wherein,
Figure 340749DEST_PATH_IMAGE024
indicating that the receiving end receives the signal,
Figure 579312DEST_PATH_IMAGE025
representing a useriThe channel gain of (a) is determined,
Figure 839392DEST_PATH_IMAGE026
is shown asiThe complex signal stream transmitted by an individual user,
Figure 183786DEST_PATH_IMAGE027
is shown as the firstiThe power allocated to the individual user(s),nrepresenting the total additive white gaussian noise received
Figure 822709DEST_PATH_IMAGE028
。
4. An adaptive decoding method applied to the SCMA-based high-speed visible light communication system according to any one of claims 1-3, the method comprising:
when the channel condition is present
Figure 859935DEST_PATH_IMAGE029
Selecting an SIC decoding mode, which specifically comprises the following steps:
calculating the codebook power of each user, performing descending sequencing on the codebook powers of all the users, and recording the arrangement sequence of the codebook powers of all the users;
decoding the codebook power in sequence according to the arrangement sequence of the codebook power of all users;
by a factor map
Figure 341732DEST_PATH_IMAGE030
Inquiring the position of the resource block occupied by the decoding user at the moment specifically comprises the following steps:
Figure 614450DEST_PATH_IMAGE031
whereinkindicating the location where the user occupies the resource block,
Figure 232513DEST_PATH_IMAGE032
is shown as
Figure 440641DEST_PATH_IMAGE033
The user, expressed by the above formula, is the first to
Figure 285100DEST_PATH_IMAGE033
Each user is in the factor graph
Figure 971296DEST_PATH_IMAGE034
Position of occupied resource blockkIn the method, the find represents a find query function in matlab software and is used for querying the position of a resource block occupied by each user;
decoding the first
Figure 975024DEST_PATH_IMAGE033
The signal transmitted by each user specifically includes:
Figure 714572DEST_PATH_IMAGE035
(ii) a Wherein m represents the decoded value corresponding to the nth symbol, norm represents matlNorm function is taken by norm in ab software, min represents min minimum function in matlab software,
Figure 905382DEST_PATH_IMAGE037
which represents the signal received at the receiving end,
Figure 395269DEST_PATH_IMAGE038
representing the decoded recovered signal, n represents the nth signal,
Figure 128870DEST_PATH_IMAGE039
represents decoding tojThe nth signal transmitted by each user;
after decoding a signal of one user, removing the secondary received signal from the total received signal, specifically comprising:
Figure 678800DEST_PATH_IMAGE040
；
wherein,
Figure 622485DEST_PATH_IMAGE041
indicating that the receiving end receives the signal,kthe representation indicates the position of the resource block occupied by the user, and n indicates the nth signal.
5. An adaptive decoding method applied to the SCMA-based high-speed visible light communication system according to any one of claims 1-3, the method comprising:
when the channel condition is present
Figure 775118DEST_PATH_IMAGE042
Then, selecting an MPA decoding scheme specifically includes:
initialization function node
Figure 222280DEST_PATH_IMAGE043
To the user node
Figure 208691DEST_PATH_IMAGE044
The probability values are specifically implemented as follows:
Figure 249459DEST_PATH_IMAGE045
wherein
Figure 81149DEST_PATH_IMAGE046
wherein
Figure 382817DEST_PATH_IMAGE047
representing functional nodes
Figure 166227DEST_PATH_IMAGE043
To the user node
Figure 818926DEST_PATH_IMAGE044
The initial probability of delivering a message is,kis shown in commonKA number of resource blocks, each of which is a number of resource blocks,jis shown in commonJThe number of the individual users is increased by the number of the individual users,
Figure 454306DEST_PATH_IMAGE049
the initial probability is represented by a probability of being,
Figure 751427DEST_PATH_IMAGE044
is shown as
Figure 814061DEST_PATH_IMAGE051
The number of the individual user nodes is,
Figure 688476DEST_PATH_IMAGE043
is shown as
Figure 127547DEST_PATH_IMAGE053
The number of the functional nodes is equal to the number of the functional nodes,
Figure 794021DEST_PATH_IMAGE054
representing a signal to be decoded by a user;
the functional node is updated, and the specific implementation is as follows:
Figure 27556DEST_PATH_IMAGE055
Figure 389267DEST_PATH_IMAGE056
；
wherein,
Figure 241817DEST_PATH_IMAGE057
representing user nodes
Figure 638163DEST_PATH_IMAGE044
To function node
Figure 42600DEST_PATH_IMAGE043
The updated probability of the delivery of the message,
Figure 517706DEST_PATH_IMAGE058
is represented in a factor graph
Figure 298580DEST_PATH_IMAGE059
To middlekThe position of the non-zero element in the row,
Figure 549432DEST_PATH_IMAGE060
is shown as
Figure 136DEST_PATH_IMAGE051
The estimated signal of the individual user or users,
Figure 602019DEST_PATH_IMAGE061
which represents the variance of the noise, is,
Figure 921005DEST_PATH_IMAGE062
which represents the gain of the channel and is,trepresenting the number of iterations，
Figure 150998DEST_PATH_IMAGE063
Indicating a received signal at a receiving end;
judging whether the maximum iteration number is reached
Figure 162816DEST_PATH_IMAGE064
If the maximum iteration times are reached, entering the next step, and if the maximum iteration times are not reached, continuously updating the resource nodes and the user nodes;
decoding the signal sent by each user, and specifically implementing the following steps:
Figure 720837DEST_PATH_IMAGE065
；
Figure 718880DEST_PATH_IMAGE066
；
Figure 678745DEST_PATH_IMAGE067
；
wherein
Figure 595886DEST_PATH_IMAGE068
Representing the bit signal finally decoded by decision,
Figure 798459DEST_PATH_IMAGE069
is shown in the factor graph
Figure 724827DEST_PATH_IMAGE070
To middlejThe position of the non-zero elements in the column,
Figure 539199DEST_PATH_IMAGE071
the maximum number of iterations is indicated,
Figure 768186DEST_PATH_IMAGE072
representing the signal to be judged, the judgment rule being a current expression
Figure 566378DEST_PATH_IMAGE073
Figure 765278DEST_PATH_IMAGE074
When the signal is true, the judged bit signal is 1, otherwise, the judged bit signal is 0, and finally, the signal obtained by judgment is stored in a variable
Figure 824370DEST_PATH_IMAGE075
In (1).
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