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Improved Techniques for Retransmission and Relaying in Wireless Systems
Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
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.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1494
Keyword [en]
Hybrid-ARQ, relaying schemes, superposition coding, 3GPP- LTE
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-68289ISBN: 978-91-7393-144-1OAI: oai:DiVA.org:liu-68289DiVA: diva2:417493
Presentation
2011-06-17, Visionen, Hus B, Campus Valla, Linköpings universitet, Linköping, 13:15 (English)
Opponent
Supervisors
Available from: 2011-05-27 Created: 2011-05-17 Last updated: 2016-08-31Bibliographically approved
List of papers
1. Improved Error Protection for Uplink Control Signaling in 3GPP-LTE via Complex-Field Coding
Open this publication in new window or tab >>Improved Error Protection for Uplink Control Signaling in 3GPP-LTE via Complex-Field Coding
2010 (English)In: Proceedings of the IEEE Vehicular Technology Conference (VTC), 2010Conference paper (Refereed)
Abstract [en]

We study the uplink control signaling in 3GPP-Long Term Evolution (LTE) systems. Specifically, we propose a precoding method that uses complex-field coding (CFC) to improve the performance of the PUCCH format 2 control signaling. In the case of perfect channel state information (CSI) at the receiver and with a single receive antenna, the proposed method offers significant gains compared to the coding currently used in 3GPP-LTE. However the gains are marginal with two receive antennas. In order to examine the impact of channel estimation errors, we also derive the optimal detector for the case of imperfect receiver CSI, both for conventional coding and for the proposed CFC method.

Series
, IEEE Vehicular Technology Conference, ISSN 1550-2252
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-53651 (URN)10.1109/VETECS.2010.5493842 (DOI)978-1-4244-2518-1 (ISBN)
Conference
IEEE 71st Vehicular Technology Conference, May 16-19, Taipei, Taiwan
Note
©2010 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEEAvailable from: 2010-05-27 Created: 2010-01-27 Last updated: 2016-08-31Bibliographically approved
2. Outage-Optimal Power Allocation for Hybrid ARQ with Incremental Redundancy
Open this publication in new window or tab >>Outage-Optimal Power Allocation for Hybrid ARQ with Incremental Redundancy
2011 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 10, no 7, 2069-2074 p.Article in journal (Refereed) Published
Abstract [en]

We consider the optimization of power in incremental redundancy (IR) based hybrid automatic repeat request (HARQ) schemes when the maximum number of(re)transmissions is fixed. We formulate two optimization problems:(i) minimizing the packet drop probability (PDP) undera total average transmit power constraint, and (ii) minimizingthe average transmit power under a fixed PDP constraint.We consider in detail the special case of only two allowed transmissions, and we prove that the two optimization problems are equivalent. For this special case, we also provide a sub-optimal root- finding solution and compare its performance with the optimal solution obtained through an exhaustive search.The results show that the optimal power allocation can provide significant gains over the equal power solution in terms of average transmit power spent. The performance of the proposed root-finding solution is practically the same as that of the optimal solution.

Place, publisher, year, edition, pages
IEEE, 2011
Keyword
Hybrid ARQ, incremental redundancy, optimal power allocation, outage probability.
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-67132 (URN)10.1109/TWC.2011.041311.101978 (DOI)000293685400010 ()
Note
Funding Agencies|Swedish Research Council (VR)||Swedish Foundation for Strategic Research (SSF)||ELLIIT||Knut and Alice Wallenberg Foundation||Available from: 2011-03-31 Created: 2011-03-31 Last updated: 2016-08-31Bibliographically approved
3. Superposition Modulation Based Symmetric Relaying with Hybrid ARQ: Analysis and Optimization
Open this publication in new window or tab >>Superposition Modulation Based Symmetric Relaying with Hybrid ARQ: Analysis and Optimization
2011 (English)In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 60, no 8, 3667-3683 p.Article in journal (Refereed) Published
Abstract [en]

We present a retransmission scheme based on superposition modulation for the symmetric relaying scenario when the number of retransmissions for a data packet is limited. We consider both diversity combining based as well as code combining based retransmission schemes. Under the assumption that the receiver implements a mechanism that can use all accumulated received mutual information when decoding the message, we derive the packet error probability (PEP) expressions for the proposed retransmission scheme for the case when only one retransmission is allowed. Based on the PEP expressions derived, we provide a closed-form solution for the optimal superposition ratio (the fraction of power used for the relaying operation). Simulation results show that the proposed retransmission scheme offers significant gains compared to a retransmission scheme based on classical decode-and-forward (DF) relaying.

Place, publisher, year, edition, pages
IEEE, 2011
Keyword
Cooperative communications, hybrid ARQ, superposition modulation, outage probability
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-68288 (URN)10.1109/TVT.2011.2162971 (DOI)000296021300011 ()
Note
Funding agencies|Swedish Foundation for Strategic Research and the Excellence Center at Linkoping-Lund in Information Technology||Knut and Alice Wallenberg Foundation through a Royal Swedish Academy of Sciences||Available from: 2011-05-17 Created: 2011-05-17 Last updated: 2016-08-31
4. Bits-to-Symbol Mappings for Superposition Coding
Open this publication in new window or tab >>Bits-to-Symbol Mappings for Superposition Coding
(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
Identifiers
urn:nbn:se:liu:diva-68282 (URN)
Available from: 2011-05-16 Created: 2011-05-16 Last updated: 2016-08-31Bibliographically approved

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