Joint constellation and code design for the Gaussian multiple access channel

Document Type

Conference Proceeding

Publication Date

7-2-2017

Abstract

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.

Identifier

85050973627 (Scopus)

ISBN

[9781538618233]

Publication Title

Conference Record of 51st Asilomar Conference on Signals Systems and Computers Acssc 2017

External Full Text Location

https://doi.org/10.1109/ACSSC.2017.8335656

First Page

1728

Last Page

1732

Volume

2017-October

Grant

CCF-1440001

Fund Ref

National Science Foundation

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