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Protograph LDPC Code Design for Asynchronous Random Access

1
Institute of Communications and Navigation of the German Aerospace Center (DLR), D-82234 Wessling, Germany
2
School of Electrical Engineering and Computing, University of Newcastle, University Drive, Callaghan, NSW 2308, Australia
3
Center for IoT and Telecommunications, School of Electrical and Information Engineering, The University of Sydney, Darlington, NSW 2006, Australia
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
This paper is an extended version of our paper published in IEEE 10th International Symposium on Turbo Codes Iterative Information Processing (ISTC), Hong Kong, 25–29 November 2018.
Algorithms 2019, 12(8), 170; https://doi.org/10.3390/a12080170
Received: 30 July 2019 / Revised: 8 August 2019 / Accepted: 13 August 2019 / Published: 15 August 2019
(This article belongs to the Special Issue Coding Theory and Its Application)
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Abstract

This work addresses the physical layer channel code design for an uncoordinated, frame- and slot-asynchronous random access protocol. Starting from the observation that collisions between two users yield very specific interference patterns, we define a surrogate channel model and propose different protograph low-density parity-check code designs. The proposed codes are both tested in a setup where the physical layer is abstracted, as well as on a more realistic channel model, where finite-length physical layer simulations of the entire asynchronous random access scheme, including decoding, are carried out. We find that the abstracted physical layer model overestimates the performance when short blocks are considered. Additionally, the optimized codes show gains in supported channel traffic, a measure of the number of terminals that can be concurrently accommodated on the channel, of around 17% at a packet loss rate of 10 2 w.r.t. off-the-shelf codes. View Full-Text
Keywords: medium access control; grant-free access; unequal error protection; successive interference cancellation; physical layer simulations; quantized density evolution; Gaussian interference channel medium access control; grant-free access; unequal error protection; successive interference cancellation; physical layer simulations; quantized density evolution; Gaussian interference channel
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Clazzer, F.; Matuz, B.; Jayasooriya, S.; Shirvanimoghaddam, M.; Johnson, S.J. Protograph LDPC Code Design for Asynchronous Random Access. Algorithms 2019, 12, 170.

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