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Bits-to-Symbol Mappings for Superposition Coding
Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-7599-4367
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Superposition coding can be used in scenarios where orthogonal sharing of resources is not efficient. In this paper, we consider two such scenarios in which superposition coding is used to send two or more users data (or packets of data) to the destination with efficient utilization of resources. Conventional way of superposing users data in Euclidean space leads to a natural mapping of bits-to-superposed-symbols. We propose the use of Gray mapping of bitsto-superposed-symbols and study the effect in terms of mutual information at the destination for the two scenarios considered in this paper. We also present some numerical results showing that using a Gray mapping of bitsto-superposed-symbols has better performance compared to the conventional natural mapping. From the results, we also conclude that the choice of optimal superposition ratio values for the AWGN channel using Gray mapping of bits for two and three user scenarios results in 4-PAM and 8-PAM constellation points for the superposed modulation symbols respectively.

National Category
Engineering and Technology
URN: urn:nbn:se:liu:diva-68282OAI: diva2:417355
Available from: 2011-05-16 Created: 2011-05-16 Last updated: 2016-08-31Bibliographically approved
In thesis
1. Improved Techniques for Retransmission and Relaying in Wireless Systems
Open this publication in new window or tab >>Improved Techniques for Retransmission and Relaying in Wireless Systems
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The last three decades have seen significant advances in the wireless communication field. As the data rates of wireless systems are increasing, the demand for mobile services also is increasing rapidly. Like other natural resources, radio spectrum suitable for mobile wireless communications is also limited. In order to keep up with this ever increasing demand, there is a requirement of new signal processing algorithms.

Diversity is a technique used in wireless systems to combat the effects of fading and thereby improve reliability of data transfer. There are many ways in which algorithms can exploit diversity in wireless channels. Hybrid-automatic repeat request (H-ARQ) schemes and relaying mechanisms are two such diversity extracting techniques. Even though these diversity achieving techniques have been well understood in theory, there are many ways in which one can optimize these techniques for specific application scenarios.In this thesis, we focus on improving the performance of retransmission schemes and relaying systems.

In the first part of the thesis, we improve the performance of H-ARQ schemes in the 3GPP- long term evolution (LTE) system by improving the performance of feedback signaling. We employ complex-field coding to extract the inherent frequency diversity available in the resources. Next, we provide a sub-optimal solution to the outage-optimal power allocation problem in incremental redundancy based H-ARQ system, whose performance is practically the same as that of the optimal solution.

In the later part of the thesis, we propose a retransmission scheme based on superposition coding (SPC) for the symmetric relaying scenario. We provide packet error probability (PEP) expressions and solutions for the optimal fraction of power allocated for the partners' data. Finally, we study the optimal bits-to-symbol mappings for SPC and its effect on an H-ARQ scheme and the symmetric relaying scenario using SPC.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 19 p.
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1494
Hybrid-ARQ, relaying schemes, superposition coding, 3GPP- LTE
National Category
Engineering and Technology
urn:nbn:se:liu:diva-68289 (URN)978-91-7393-144-1 (ISBN)
2011-06-17, Visionen, Hus B, Campus Valla, Linköpings universitet, Linköping, 13:15 (English)
Available from: 2011-05-27 Created: 2011-05-17 Last updated: 2016-08-31Bibliographically approved

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