University of Oulu

H. Asgharimoghaddam and A. Tölli, "Resource Allocation in Low Density Spreading Uplink NOMA via Asymptotic Analysis," 2020 IEEE International Symposium on Information Theory (ISIT), Los Angeles, CA, USA, 2020, pp. 3049-3054, doi: 10.1109/ISIT44484.2020.9174401

Resource allocation in low density spreading uplink NOMA via asymptotic analysis

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Author: Asgharimoghaddam, Hossein1; Tölli, Antti1
Organizations: 1Centre for wireless communications (CWC), University of Oulu, Oulu, Finland
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 0.5 MB)
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Language: English
Published: Institute of Electrical and Electronics Engineers, 2020
Publish Date: 2020-12-18


Low density spreading non-orthogonal multiple- access (LDS-NOMA) is considered where K single-antenna user equipments (UEs) communicate with a base station (BS) over F fading sub-carriers. Each UE k spreads its data symbol over d k <; F sub-carriers. Given d k , ∀k as design parameters, we characterize the resource allocation solutions that closely maximize the ergodic mutual information (EMI) in a scenario where the BS assigns resources solely based on the UEs’ pathlosses. Conducting analysis in asymptotic limit where F, K, and d k , ∀k converge to +∞ at the same rate, we present EMI in terms of a deterministic equivalent plus a residual term. The deterministic equivalent is given in terms of pathloss values and LDS-codes, and the small residual term scales as O(1/d 2 ) where d = min{d k , ∀k}. We formulate an optimization problem to get the set C̅* of all spreading codes, irrespective of sparsity constraints, which maximize the deterministic equivalent of EMI. The spreading codes in C̅* with desired sparsity are obtained via a simple and efficient algorithmic solution. In the finite regime, the residual term is shown to be a small incremental gain for the sparse solutions in C̅*, which is dictated mainly by d k , ∀k values. Accordingly, we show that the solutions in C̅* with desired sparsity yield close to optimum values of EMI in the finite regime. Numerical simulation validates the attainable spectral efficiency enhancement as compared to regular, and random spreading.

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Series: IEEE International Symposium on Information Theory proceedings
ISSN: 2157-8095
ISSN-E: 2157-8117
ISSN-L: 2157-8095
ISBN: 978-1-7281-6432-8
ISBN Print: 978-1-7281-6433-5
Pages: 3049 - 3054
DOI: 10.1109/ISIT44484.2020.9174401
Host publication: 2020 IEEE International Symposium on Information Theory (ISIT)
Conference: IEEE International Symposium on Information Theory
Type of Publication: A4 Article in conference proceedings
Field of Science: 213 Electronic, automation and communications engineering, electronics
Funding: This work has been supported in part by the Academy of Finland 6Genesis Flagship (grant no. 318927).
Academy of Finland Grant Number: 318927
Detailed Information: 318927 (Academy of Finland Funding decision)
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