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HARQ Systems: Resource Allocation, Feedback Error Protection, and Bits-to-Symbol Mappings
Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Reliability of data transmission is a fundamental problem in wireless communications. Fading in wireless channels causes the signal strength to vary at the receiver and this results in loss of data packets. To improve the reliability, automatic repeat request (ARQ) schemes were introduced. However these ARQ schemes suffer from a reduction in the throughput. To address the throughput reduction, conventional ARQ schemes were combined with forward error correction (FEC) schemes to develop hybrid-ARQ (HARQ) schemes. For improving the reliability of data transmission, HARQ schemes are included in the present wireless standards like LTE, LTE-Advanced and WiMAX.

Conventional HARQ systems use the same transmission power and the same number of channel uses in different ARQ rounds. However this is not optimal in terms of minimizing the average transmit power or the average energy spent for successful transmission of a data packet. We address this issue in the first part of the dissertation, where we consider optimal resource allocation in HARQ systems with a limit on the maximum number of allowed transmissions for a data packet. Specifically, we consider the problem of minimizing the packet drop probability (PDP) under an average transmit power constraint or equivalently minimizing the average transmit power under a fixed PDP constraint. We consider both incremental redundancy (IR)-based and Chase combining (CC)-based HARQ systems in our work. For an IR-HARQ system, for the special case of two allowed transmissions for each packet, we provide a solution for the optimal number of channel uses and the optimal power to be used in each ARQ round. For a CC-HARQ system, we solve the problem of optimal power allocation in i.i.d. Rayleigh fading channels as well as correlated Rayleigh fading channels. For the CC-HARQ case, we also provide a low complexity geometric programming (GP) solution using an approximation of the outage probability expression.

HARQ systems conventionally use one bit acknowledgement (ACK)/negative ACK (NACK) feedback from the receiver to the transmitter. In the 3GPP-LTE systems, one method for sending these HARQ acknowledgement bits is to jointly code them with the other control signaling information using a specified Reed-Muller code consisting of 20 coded bits. Even though the resources used for sending this control signaling information can inherently provide a diversity gain, the Reed-Muller code with such a short block size is not good at extracting all of the available diversity. To address this issue, in the second part of this dissertation, we propose two new methods: i) based on complex-field coding (CFC), and ii) using repetition across frequency bands, to extract the inherent diversity available in the channel resources and improve the error protection for the HARQ acknowledgement bits along with the other control signaling information. In the second part of the dissertation, we also propose a new signal space diversity (SSD) scheme, which results in transmit signals having constant envelope (CE). The proposed CE-SSD scheme results in a better overall power efficiency due to the reduced back-off requirements on the radio frequency power amplifier. Moreover, the proposed CE-SSD technique can be useful for application scenarios involving transmission of small number of information bits, such as in the case of control signaling information transmission.

In conventional HARQ systems, during the retransmission phase, the channel resources are exclusively used for the retransmitted data packet. This is not optimal in terms of efficient resource utilization. For efficient utilization of channel resources during the retransmissions, a superposition coding (SPC) based HARQ scheme was proposed in the literature. In an SPC based HARQ system, an erroneous packet is transmitted together with a new data packet by superposition in the Euclidean space. In the final part of this dissertation, we study performance of different bits-to-symbol mappings for such an SPC based HARQ system.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. , 43 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1526
Keyword [en]
HARQ Systems, Resource Allocation, Geometric Programming, 3GPP-LTE, PUCCH Format 2, Complex-field coding, Signal Space Diversity, Optimization, Superposition Coding
National Category
Communication Systems Telecommunications
Identifiers
URN: urn:nbn:se:liu:diva-96021ISBN: 978-91-7519-574-2 (print)OAI: oai:DiVA.org:liu-96021DiVA: diva2:640306
Public defence
2013-09-27, Visionen, Hus B, Campus Valla, Linköpings universitet, Linköping, 10:56 (English)
Opponent
Supervisors
Available from: 2013-09-11 Created: 2013-08-13 Last updated: 2017-01-13Bibliographically approved
List of papers
1. 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: 2017-12-11Bibliographically approved
2. Optimal Resource Allocation for IR-HARQ
Open this publication in new window or tab >>Optimal Resource Allocation for IR-HARQ
2011 (English)In: Proceedings of the IEEE Swe-CTW, 2011, 74-79 p.Conference paper, Published paper (Refereed)
Abstract [en]

In this work, we first provide an exact closed-form expression for the packet drop probability (PDP) in incremental redundancy (IR) based hybrid automatic repeat request (HARQ) schemes with a limit on the maximum number of transmissions. In the later part, we extend our work in [5], and consider the optimal resource allocation problem of minimizing the PDP under the constraints of an average transmit power and total number of channel uses. We provide two approaches to solve this optimization problem and compare their performance with the solution given in [5].

Keyword
Hybrid ARQ, Incremental redundancy, Optimal resource allocation, Outage probability
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-71014 (URN)10.1109/Swe-CTW.2011.6082492 (DOI)978-1-4577-1876-2 (ISBN)978-1-4577-1877-9 (ISBN)
Conference
IEEE Swedish Communication Technologies Workshop (Swe-CTW)
Funder
Swedish Research CouncileLLIIT - The Linköping‐Lund Initiative on IT and Mobile Communications
Available from: 2011-09-27 Created: 2011-09-27 Last updated: 2016-08-31
3. Optimal Power Allocation for Hybrid ARQ with Chase Combining in i.i.d. Rayleigh Fading Channels
Open this publication in new window or tab >>Optimal Power Allocation for Hybrid ARQ with Chase Combining in i.i.d. Rayleigh Fading Channels
2013 (English)In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 61, no 5, 1835-1846 p.Article in journal (Refereed) Published
Abstract [en]

We consider the optimization of Chase combining (CC)-based hybrid-automatic repeat request (HARQ) schemes with a limit on the maximum number of retransmissions. We formulate two optimization problems: (i) minimizing the packet drop probability (PDP) under a total average transmit power constraint, and (ii) minimizing the average transmit power under a fixed PDP constraint. Towards solving these equivalent optimization problems, we provide a closed-form expression for the outage probability of a CC-HARQ scheme. We then show that solving the optimization problems using an exact expression of the outage probability becomes complex with an increase in the maximum number of retransmissions. We propose an alternative approach in which we approximate the optimization problems by using an approximate outage probability expression and formulate the two optimization problems as two equivalent geometric programming problems (GPPs), which can be solved efficiently even for a large limit on the maximum number of retransmissions.

The results show that the optimal power allocation solution provides significant gains over the equal power allocation solution. For PDP values below 10-3 , the optimal solution provided by the GPP approach has a performance close to that of the solution provided by solving the optimization problem exactly using nonlinear optimization techniques.

Place, publisher, year, edition, pages
IEEE Press, 2013
Keyword
Hybrid-ARQ, diversity combining, optimal power allocation, outage probability, geometric programming.
National Category
Communication Systems Telecommunications
Identifiers
urn:nbn:se:liu:diva-89650 (URN)10.1109/TCOMM.2013.032013.120422 (DOI)000319752600019 ()
Funder
eLLIIT - The Linköping‐Lund Initiative on IT and Mobile CommunicationsSwedish Foundation for Strategic Research Swedish Research Council
Available from: 2013-04-03 Created: 2013-02-28 Last updated: 2017-12-06Bibliographically approved
4. Adaptive power allocation for HARQ with Chase combining in correlated Rayleigh fading channels
Open this publication in new window or tab >>Adaptive power allocation for HARQ with Chase combining in correlated Rayleigh fading channels
2014 (English)In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 3, no 2, 169-172 p.Article in journal (Refereed) Published
Abstract [en]

We consider the problem of minimizing the packet drop probability (PDP) under an average transmit power constraint for Chase combining (CC)-based hybrid-automatic repeat request (HARQ) schemes in correlated Rayleigh fading channels. We propose a method to find a solution to the non-convex optimization problem using an exact expression of the outage probability. However, the complexity of this method is high. Therefore, we propose an alternative approach in which we use an asymptotically equivalent expression for the outage probability and reformulate it as a geometric programming problem (GPP), which can be efficiently solved using convex optimization algorithms.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2014
National Category
Signal Processing
Identifiers
urn:nbn:se:liu:diva-129056 (URN)10.1109/WCL.2013.122113.130793 (DOI)000209681200013 ()
Note

The previous status of this article was Manuscript and the working title was Adaptive Power Allocation for Hybrid ARQ with Chase Combining in Correlated Rayleigh Fading Channels.

Available from: 2016-06-09 Created: 2016-06-09 Last updated: 2017-11-30Bibliographically approved
5. Improving 3GPP-LTE Uplink Control Signaling Performance Using Complex-Field Coding
Open this publication in new window or tab >>Improving 3GPP-LTE Uplink Control Signaling Performance Using Complex-Field Coding
2013 (English)In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 62, no 1, 161-171 p.Article in journal (Refereed) Published
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 physical uplink control channel (PUCCH) format 2 control signaling. We derive optimal detectors for both the conventional method and the proposed precoding method for different cases of channel state information (CSI) and noise variance information at the receiver. With a single receive antenna, the proposed method offers significant gains compared to the coding currently used in 3GPP-LTE for all the different scenarios considered in this work. However the gains are relatively less with two receive antennas.

Keyword
3GPP-LTE, uplink control signaling, complex-field coding, perfect CSI, imperfect CSI, optimal detection.
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-80150 (URN)10.1109/TVT.2012.2215061 (DOI)000318514000016 ()
Funder
eLLIIT - The Linköping‐Lund Initiative on IT and Mobile Communications
Note

(c) 2012 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.

Available from: 2012-08-21 Created: 2012-08-21 Last updated: 2017-12-07
6. Improving 3GPP-LTE Uplink Control Signaling by Repetition Across Frequency Bands
Open this publication in new window or tab >>Improving 3GPP-LTE Uplink Control Signaling by Repetition Across Frequency Bands
2013 (English)In: Proceedings of the IEEE International Conference on Communications (ICC), IEEE , 2013, 1243-1248 p.Conference paper, Published paper (Refereed)
Abstract [en]

We propose improvements for the physical uplink control channel (PUCCH) format 2 control signaling in 3GPP-LTE systems. These improvements can be useful for low-cost UE design and optimization planned for the future LTE releases. In the proposed method, instead of repeating a single QPSK symbol across the 12 subcarriers in each OFDM symbol of a resource block as done in the current release of the standard, we pick two QPSK symbols from two independent resource blocks and repeat them across 6 subcarriers each. The proposed method has a performance gain of about 5.5 dB and 1.85 dB over the conventional method with one and two receiving antennas at the base station, respectively. These gains can be achieved without the use of any additional transmission power, time-frequency resources or receiver complexity.

The cell-specific QPSK sequences specified in the standard for PUCCH transmission are chosen according to the conventional repetition across the 12 subcarriers, hence we suggest new cell-specific QPSK sequences which minimize the peak-to-average-power ratio (PAPR) of the PUCCH signal with the proposed method.

Place, publisher, year, edition, pages
IEEE, 2013
Keyword
3GPP-LTE, uplink, control signaling, PUCCH
National Category
Communication Systems Telecommunications
Identifiers
urn:nbn:se:liu:diva-89654 (URN)10.1109/ICCW.2013.6649427 (DOI)978-146735753-1 (ISBN)
Conference
IEEE International Conference on Communications (ICC 2013), 9-13 June 2013, Budapest, Hungary
Funder
VinnovaeLLIIT - The Linköping‐Lund Initiative on IT and Mobile Communications
Available from: 2013-04-03 Created: 2013-02-28 Last updated: 2016-08-31Bibliographically approved
7. Constant envelope signal space diversity
Open this publication in new window or tab >>Constant envelope signal space diversity
2014 (English)In: Proceedings of the 2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), IEEE conference proceedings, 2014, 3147-3151 p.Conference paper, Published paper (Refereed)
Abstract [en]

We propose a nonlinear signal space diversity (SSD) precoding techniquethat produces transmit signals that have constant envelope(CE) in discrete time, resulting in low peak-to-average power ratio(PAPR) waveforms after pulse-shape filtering. We propose twomethods for construction of CE signal set. While the proposed CESSDscheme is inferior to the conventional SSD designs in termsof coding gain performance, it performs better in terms of overallpower efficiency because of the reduced back-off requirement of thepower amplifier (PA).

Place, publisher, year, edition, pages
IEEE conference proceedings, 2014
Series
IEEE International Conference on Acoustics, Speech and Signal Processing. Proceedings, ISSN 1520-6149
Keyword
Signal space diversity, constant envelope, constellation design, power amplifier efficiency, low PAPR
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-109639 (URN)10.1109/ICASSP.2014.6854180 (DOI)000343655303036 ()
Conference
Acoustics, Speech and Signal Processing (ICASSP), 2014 IEEE International Conference on
Note

The previous status of this article was Manuscript.

Available from: 2014-08-22 Created: 2014-08-22 Last updated: 2017-01-13Bibliographically approved
8. Bits-to-Symbol Mappings for Superposition Coding Based HARQ Systems
Open this publication in new window or tab >>Bits-to-Symbol Mappings for Superposition Coding Based HARQ Systems
2013 (English)In: Proceedings of the IEEE Wireless Communications and Networking Conference (WCNC), Institute of Electrical and Electronics Engineers (IEEE), 2013, 2468-2472 p.Conference paper, Published paper (Refereed)
Abstract [en]

We consider the mapping of bits-to-superimposed constellation symbols in terms of the achievable rate on the channel for the HARQ system using superposition coding as proposed in [2]. We show that using a Gray mapping of bits-to-superimposed constellation symbols has better performance thanthe conventional natural mapping that results from superposition in signal space, for all the values of the superposition ratio. We also show through link-level simulations that the predicted gains in terms of achievable rate can be realized in practice using LDPC codes. Furthermore, we show that the optimal superposition ratio for the Gray mapping case results in conventional higher order constellation symbols after the superposition operation.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2013
Series
IEEE Wireless Communications and Networking Conference. Proceedings, ISSN 1525-3511
Keyword
Superposition coding, bits-to-symbol mapping, hybrid ARQ
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-87279 (URN)10.1109/WCNC.2013.6554948 (DOI)978-1-4673-5938-2 (ISBN)978-1-4673-5937-5 (ISBN)
Conference
IEEE Wireless Communications and Networking Conference, WCNC 2013, 7-10 April, Shanghai; China
Note

The previous status of this article was Manuscript and the working title was Bits-to-Symbol Mappings for Superposition Coding.

Available from: 2013-04-03 Created: 2013-01-15 Last updated: 2017-01-13Bibliographically approved

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