Compute-Forward Multiple Access (CFMA): Practical Implementations

We present a practical strategy that aims to attain rate points on the dominant face of the multiple access channel capacity using a standard low complexity decoder. This technique is built upon recent theoretical developments of Zhu and Gastpar on compute-forward multiple access which achieves the...

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Bibliographic Details
Published in:IEEE transactions on communications 2019-02, Vol.67 (2), p.1133-1147
Main Authors: Sula, Erixhen, Zhu, Jingge, Pastore, Adriano, Lim, Sung Hoon, Gastpar, Michael
Format: Article
Language:English
Subjects:
Algorithms
Binary codes
Binary system
Channel capacity
Codes
Complexity
Complexity theory
Computer simulation
Compute–forward multiple access (CFMA)
Decoding
Face
Interference channels
Low density parity check codes
low density parity check codes (LDPC)
Multiple access
multiple access channel
Parity check codes
Receivers
sequential decoding
Strategy
sum-product algorithm
Time sharing
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Summary:We present a practical strategy that aims to attain rate points on the dominant face of the multiple access channel capacity using a standard low complexity decoder. This technique is built upon recent theoretical developments of Zhu and Gastpar on compute-forward multiple access which achieves the capacity of the multiple access channel using a sequential decoder. We illustrate this strategy with off-the-shelf LDPC codes. In the first stage of decoding, the receiver first recovers a linear combination of the transmitted codewords using the sum-product algorithm (SPA). In the second stage, by using the recovered sum-of-codewords as side information, the receiver recovers one of the two codewords using a modified SPA, ultimately recovering both codewords. The main benefit of recovering the sum-of-codewords instead of the codeword itself is that it allows to attain points on the dominant face of the multiple access channel capacity without the need of rate-splitting or time sharing while maintaining a low complexity in the order of a standard point-to-point decoder. This property is also shown to be crucial for some applications, e.g., interference channels. For all the simulations with single-layer binary codes, our proposed practical strategy is shown to be within 1.7 dB of the theoretical limits, without explicit optimization on the off-the-self LDPC codes.
ISSN:0090-6778
1558-0857
DOI:10.1109/TCOMM.2018.2874240