A Low-Complexity Message Passing Decoding Algorithm Based on Factor Graph Evolution in Sparse Code Multiple Access

Abstract

The invention provides a low-complexity message passing decoding algorithm based on factor graph evolution. A factor graph is simplified to realize low-complexity decoding, the degrees of resource nodes are classified at first, all resource nodes are removed at first, then the low-degree nodes are added to the factor graph for decoding gradually, therefore the evolution of the factor graph is realized, the obtained symbol experience information is stored, when the high-degree nodes are added to the factor graph subsequently, the high complexity of the traditional message passing algorithm under codebook collision can be greatly reduced by means of the hard judgment of a part of symbols by using the experience information, thereby reducing the decoding delay and further improving the performance expression of SCMA, in addition, by means of different settings of an update step length and a final update value of the factor graph, different compromise situations between the decoding accuracy and the decoding complexity can be obtained, and thus the algorithm is applicable to the actual application demands more flexibly.

Description

technical field [0001] The invention belongs to the technical field of non-orthogonal multiple access, in particular to a low-complexity message passing decoding algorithm based on factor graph evolution in sparse code multiple access. Background technique [0002] Sparse Code Multiple Access SCMA (Sparse Code Multiple Access) allocates codebooks for users to implement non-orthogonal multiple access. Through the sparsity design of the codebook, it can ensure that the codewords from multiple different codebooks are superimposed together and the receiver can still decode, so as to realize the overload when the number of access users is more than the number of available orthogonal communication resources, and increase the number of connectable number, which cannot be realized by traditional orthogonal multiple access. It is also because of this feature that SCMA does not require users to establish a connection with the base station before transmitting, but allows users to dire...

AI Technical Summary

Problems solved by technology

Since the traditional message passing algorithm needs to traverse the possible symbol set and iterate multiple times, when the codebook conflict mentioned above occurs, the symbols of multiple users will conflict at the same resource node, which is equivalent to the required traversal The possible symbol integration exponentially expands, which increases the decoding complexity, increases the overall access delay, and may eventually destroy the real-time requirements

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