CN110113136B - Decoding method in SCMA system - Google Patents
Decoding method in SCMA system Download PDFInfo
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- CN110113136B CN110113136B CN201910405171.5A CN201910405171A CN110113136B CN 110113136 B CN110113136 B CN 110113136B CN 201910405171 A CN201910405171 A CN 201910405171A CN 110113136 B CN110113136 B CN 110113136B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0045—Arrangements at the receiver end
- H04L1/0047—Decoding adapted to other signal detection operation
- H04L1/005—Iterative decoding, including iteration between signal detection and decoding operation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0045—Arrangements at the receiver end
- H04L1/0052—Realisations of complexity reduction techniques, e.g. pipelining or use of look-up tables
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Abstract
The invention has proposed the decoding method in a SCMA system, step 1, the information input; step 2, dividing different resource blocks into different priorities according to the anti-interference capability of the resource blocks; step 3, separating and solving the user group code words in the first priority resource block through MPA iterative computation; step 4, deducing code words transmitted by users in the first priority resource block on other resource blocks according to the codebook; step 5, MPA iterative operation is carried out to separate and solve the user group code words in the second priority resource block; different resource blocks are graded on the anti-interference capacity, the code words of the resource blocks with strong capacity are decoded first, and then the code words on other resource blocks are reasoned, so that the decoding BER performance is not influenced, and the operation complexity of a decoding end can be greatly reduced. Especially for the large-size codebook for practical use, the advantages of the scheme are more prominent and superior, and all the schemes have considerable practical application values.
Description
Technical Field
The invention relates to a decoding algorithm, and belongs to the field of wireless communication.
Background
In the Fifth-Generation mobile communication (5G) era in the future, driven by the rapid development of Internet of Things (IoT) services, a huge amount of mobile devices will be connected in the future, and an extremely low air interface delay is required, which undoubtedly provides a more serious challenge for wireless air interface technologies. Therefore, in order to meet the requirement of 5G application scenarios, the conventional Orthogonal Multiple Access (OMA) technology, such as time division Multiple Access, frequency division Multiple Access, etc., cannot meet the requirement of future wireless communication development, and it is necessary to turn attention to some Non-Orthogonal Multiple Access (NOMA), and the new Multiple Access technology becomes a popular research problem for wireless communication.
The SCMA technology is a non-orthogonal Multiple Access scheme for sharing frequency resources by Multiple users, combines a Low Density Signal (LDS) technology and a Code Division Multiple Access (CDMA) technology, and can be used for solving the overload problem of a system with mass connection. However, to become a very competitive socket technology in 5G, the SCMA system still needs to solve the following problems: the method comprises the steps of optimizing codebook design, low-complexity multi-user detection schemes, good system performance, channel allocation optimization, scheduling-free strategies, blind detection schemes and the like.
In the SCMA system, an efficient multi-user detection algorithm is an important component of a 5G wireless air interface technology. The Maximum A Posteriori (MAP) algorithm is used as the optimal multi-user detection scheme of the SCMA system, the calculation complexity of the MAP algorithm increases exponentially along with the number of users, and the decoding complexity at a signal receiving end is too high to meet the actual communication requirement. And the Message Passing Algorithm (MPA) is taken as a near-optimal SCMA multi-user detection scheme, and the MAP decoding performance can be effectively approached by utilizing the code word sparse characteristic, and the decoding complexity can be greatly reduced. However, as the number of users and the size of the codebook increase, the decoding complexity of the MPA algorithm still increases exponentially, so it is important to reduce the complexity of the MPA algorithm in the SCMA system.
Disclosure of Invention
The technical problem to be solved by the invention is to reduce the complexity of MPA algorithm in the SCMA system, and provide a decoding method in the SCMA system for overcoming the defects of the prior art.
The invention provides a decoding method in an SCMA system, which comprises the following steps:
step 1, inputting information;
step 2, dividing different resource blocks into different priorities according to the anti-interference capability of the resource blocks;
step 3, separating and solving the user group code words in the first priority resource block through MPA iterative computation;
step 4, deducing code words transmitted by users in the first priority resource block on other resource blocks according to the codebook;
step 5, MPA iterative operation is carried out to separate and solve the user group code words in the second priority resource block;
step 6, calculating the code words transmitted by the users in the resource blocks with the second priority on other resource blocks according to the codebook;
and 7, repeating the steps until the code words of all the users are separated.
Further, the specific content of step 2 is as follows:
firstly, the strength of the anti-interference capability of each resource block k is judged in a grading way, and initialization setting is carried out:
further, the specific content of step 3 is as follows:
when i < m, then:
further, the specific content of step 4 is as follows:
when i is m, then
I.e. users with priority 1 resource block:
further, the specific content of step 5 is as follows:
when m < i < m + γ, then:
further, the specific content of step 6 is as follows:
when i ═ m + γ, then:
i.e. users with a priority of 2 resource blocks
Further, the specific content of step 7 is as follows:
when If m + gamma < i < T, then
So when i is T, then
I.e. users with a priority of 3 resource blocks
Compared with the prior art, the invention adopting the technical scheme has the following technical effects: different resource blocks are graded on the anti-interference capacity, the code words of the resource blocks with strong capacity are decoded first, and then the code words on other resource blocks are reasoned, so that the decoding BER performance is not influenced, and the operation complexity of a decoding end can be greatly reduced. Especially for the large-size codebook for practical use, the advantages of the scheme are more prominent and superior, and all the schemes have considerable practical application values.
Drawings
FIG. 1 is a diagram of an SCMA system model according to the present invention.
FIG. 2 is a factor graph of the system of the present invention.
FIG. 3 is a schematic diagram of the algorithm of the present invention.
Fig. 4 is a flow chart of the algorithm of the present invention.
Detailed Description
The technical scheme of the invention is further explained in detail by combining the attached drawings 1-4:
the embodiment provides a decoding method in an SCMA system, comprising the steps of 1, inputting information;
step 2, based on the anti-interference capability of the resource blocks, users on different resource blocks are divided into different priorities: firstly, the strength of the anti-interference capability of each resource block k is judged in a grading way, and initialization setting is carried out:
and 3, separating and resolving the code words of the first priority user group through a small number of iterative MPAs: when i < m, then:
and 4, deducing code words transmitted by the users with the first priority on other resource blocks according to the codebook: when i is m, then
I.e. users with priority 1 resource block:
and 5, performing proper MPA iterative operation to separate and solve the code words of the second priority user group: when m < i < m + γ, then:
step 6, calculating a second priority according to the codebookCode word transmitted by the users of the rank on other resource blocks: when i ═ m + γ, then:
i.e. users with a priority of 2 resource blocks
And 7, repeating the steps until the code words of all the users are separated: when If m + gamma < i < T, then
So when i is T, then
I.e. users with a priority of 3 resource blocks,
in the invention, there are 4 resource blocks and 6 users in the factor graph 2, the strength of the anti-interference capability of the resource block is (RE1> RE2> RE3> RE4), the strongest anti-interference capability of the resource block can be obtained (RE1), that is, the interference on the information transmitted by the user on the resource block is the smallest, the user information can be separated after a small number of iterations, so that the users (UE1, UE3, and UE5) on RE1 are preferentially separated, and after knowing the code words transmitted by UE1, UE3, and UE5 on RE1, the code words transmitted by the users UE1 on RE2, UE3 on RE3, and UE5 on RE4 are also separated according to the characteristics of the code book. The anti-interference capability of the RE2 is secondly, then the UE1, the UE4 and the UE6 are separated from the lower side, because the UE1 has been separated on the upper part, only the UE4 and the UE6 need to be separated from the lower side, after a small amount of iterative computations, the two users are separated, and finally, only the user 2 (UE2) remains, because the two resource blocks used by the UE2 for transmission have weaker anti-interference capability, the number of iterations required for separating the user is the largest, and thus the process is continued downwards until all user codewords are decoded and separated.
The invention divides different resource blocks into different priority levels according to the strength of the anti-interference capability of the different resource blocks, and users on the resource blocks are user groups with different priority levels. And preferentially separating the user groups with high priority through certain iteration according to the priority, and then separating and decoding the user groups with the second best priority through a small amount of iteration until the user group with the lowest priority is decoded and separated, thereby finally obtaining the code words of all users. The method mainly uses resources as a user grouping basis to decode and separate different user groups in sequence, and the separated users do not need to participate in subsequent iterative operation, so that the overall operation complexity is reduced, and the performance loss is avoided.
The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can understand that the modifications or substitutions within the technical scope of the present invention are included in the scope of the present invention, and therefore, the scope of the present invention should be subject to the protection scope of the claims.
Claims (7)
1. A decoding method in an SCMA system, comprising the steps of:
step 1, inputting information;
step 2, dividing different resource blocks into different priorities according to the anti-interference capability of the resource blocks;
step 3, separating and solving the user group code words in the first priority resource block through MPA iterative computation;
step 4, deducing code words transmitted by users in the first priority resource block on other resource blocks according to the codebook;
step 5, MPA iterative operation is carried out to separate and solve the user group code words in the second priority resource block;
step 6, calculating the code words transmitted by the users in the resource blocks with the second priority on other resource blocks according to the codebook;
and 7, repeating the steps until the code words of all the users are separated.
2. The decoding method in the SCMA system according to claim 1, wherein the specific content of the step 2 is as follows:
firstly, the strength of the anti-interference capability of each resource block k is judged in a grading way, and initialization setting is carried out:
3. the decoding method in the SCMA system according to claim 2, wherein the specific content of step 3 is as follows:
when i < m, then:
4. the decoding method in an SCMA system according to claim 3, wherein the detailed contents of step 4 are as follows:
when i is m, then
I.e. users with priority 1 resource block:
5. the decoding method in an SCMA system according to claim 4, wherein the specific content of the step 5 is as follows:
when m < i < m + γ, then:
6. the decoding method in the SCMA system according to claim 5, wherein the detailed contents of the step 6 are as follows:
when i ═ m + γ, then:
i.e. users with a priority of 2 resource blocks
7. The decoding method in the SCMA system according to claim 6, wherein the detailed contents of step 7 are as follows:
when If m + gamma < i < T, then
So when i is T, then
I.e. users with a priority of 3 resource blocks
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