Browsing by Author "Kliewer, Jorg"

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Joint Constellation and Code Design for the Gaussian Multiple Access Channel
(2017-01-01)
Liang, Yu-Chung
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Rini, Stefano
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Kliewer, Jorg
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交大名義發表
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National Chiao Tung University
The joint design of both transmit constellation and low-density parity-check codes (LDPC) for the two-user, symbol-synchronous, binary-input Gaussian multiple access channel is considered. A transmission scheme is proposed to approach the symmetric capacity without the use of time-sharing or rate-splitting by joint decoding of the noisy sum of two LDPC codewords. This scheme relies on an extension of the classic belief propagation (BP) algorithm which allows for the simultaneous decoding of two LDPC codewords. We use a Gaussian approximation (GA) of the message distribution to investigate the convergence of the decoding process and derive a linear programming technique for joint code design. We also implement a superposition modulation scheme to achieve higher rate. This code design is applied to different input constellation choices which attain the symmetric capacity in different SNR regimes. It is shown that, quite surprisingly, in the moderate SNR regime the best performance is obtained by an asymmetric constellation.
LDPC Coded Multiuser Shaping for the Gaussian Multiple Access Channel
(2019-01-01)
Balatsoukas-Stimming, Alexios
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Rini, Stefano
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Kliewer, Jorg
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交大名義發表
;
National Chiao Tung University
The joint design of input constellation and low-density parity-check (LDPC) codes to approach the symmetric capacity of the two-user Gaussian multiple access channel is studied. More specifically, multilevel coding is employed at each user to construct a high-order input constellation and the constellations of the users are jointly designed so as to maximize the multiuser shaping gain. At the receiver, each layer of the multilevel coding is jointly decoded among users, while successive cancellation is employed across layers. The LDPC code employed by each user in each layer is designed using EXIT charts to support joint decoding among users for the prescribed per-layer rate and SNR. Numerical simulations are provided to validate the proposed constellation and LDPC code designs.