Reduced Complexity Rate-Splitting Multiple Access
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Authors
Sadeghabadi, Elaheh
Date
2024-07-31
Type
thesis
Language
eng
Keyword
Rate-splitting multiple access , Broadcast channel , Multiple-input single-output communications , Non-orthogonal multiple access , Space-division multiple access , Multiple access channel , Single-input single-output communications , Sum rate maximization , Fairness
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Abstract
Future wireless communication systems face challenges to handle severe multi-user interference. Rate splitting multiple access (RSMA) enables interference management trade-offs between space-division multiple access and non-orthogonal multiple access to serve multiple users in the multiple-input multiple-output broadcast channel. The number of transmitted streams and possible decoding orders in the general form of RSMA grow exponentially with the number of users. In addition, the RSMA optimization problem to design precoding is non-convex, and as a result, sub-optimal precoding design approaches must be applied. Hence, the performance of RSMA depends on (i) how streams are generated and (ii) precoding design.
In this thesis, to provide low-complexity solutions for RSMA, hierarchical streams that transmit a subset of possible streams of encoded messages are proposed for rate splitting and analyzed. Simulation results show that the proposed scheme can achieve attractive performance vs. complexity trade-offs compared to several others in the literature.
To reduce precoding complexity, RSMA-IN, that nulls the portion of interference that is not decoded is investigated by formulating a sum rate maximization problem subject to a total power constraint. To solve this non-convex problem, a method that combines interference nulling and stream signal-to-noise-ratio maximization is proposed. In addition, a convex upper bound problem is formulated for the sum rate to compare existing algorithms. Simulation results indicate that the proposed approaches enhance performance over existing ones as well as approach their upper bounds in certain instances.
Low-complexity precoding design problem is considered in a more general way that the interference nulling condition is removed, and the RSMA performance evaluation function may be an arbitrary increasing function of split user rates. In this regard, a parameterization of optimal beamforming directions for different performance maximization problems subject to a total power constraint is obtained for RSMA.
This thesis also investigates rate-splitting for the uplink. The unsolved problem of finding the RSMA scheme to achieve a given users' rate tuple in a single antenna multiple access channel is addressed by proposing an algorithm that hierarchically and recursively derives the splitting powers and the decoding orders, which has less complexity in comparison to other available approaches.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.