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From Orthogonal to Non-orthogonal Multiple Access: Energy- and Spectrum-Efficient Resource Allocation
Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The rapid pace of innovations in information and communication technology (ICT) industry over the past decade has greatly improved people’s mobile communication experience. This, in turn, has escalated exponential growth in the number of connected mobile devices and data traffic volume in wireless networks. Researchers and network service providers have faced many challenges in providing seamless, ubiquitous, reliable, and high-speed data service to mobile users. Mathematical optimization, as a powerful tool, plays an important role in addressing such challenging issues.

This dissertation addresses several radio resource allocation problems in 4G and 5G mobile communication systems, in order to improve network performance in terms of throughput, energy, or fairness. Mathematical optimization is applied as the main approach to analyze and solve the problems. Theoretical analysis and algorithmic solutions are derived. Numerical results are obtained to validate our theoretical findings and demonstrate the algorithms’ ability of attaining optimal or near-optimal solutions.

Five research papers are included in the dissertation. In Paper I, we study a set of optimization problems of consecutive-channel allocation in single carrier-frequency division multiple access (SCFDMA) systems. We provide a unified algorithmic framework to optimize the channel allocation and improve system performance. The next three papers are devoted to studying energy-saving problems in orthogonal frequency division multiple access (OFDMA) systems. In Paper II, we investigate a problem of jointly minimizing energy consumption at both transmitter and receiver sides. An energy-efficient scheduling algorithm is developed to provide optimality bounds and near-optimal solutions. Next in Paper III, we derive fundamental properties for energy minimization in loadcoupled OFDMA networks. Our analytical results suggest that the maximal use of time-frequency resources can lead to the lowest network energy consumption. An iterative power adjustment algorithm is developed to obtain the optimal power solution with guaranteed convergence. In Paper IV, we study an energy minimization problem from the perspective of scheduling activation and deactivation of base station transmissions. We provide mathematical formulations and theoretical insights. For problem solution, a column generation approach, as well as a bounding scheme are developed. Finally, towards to 5G communication systems, joint power and channel allocation in non-orthogonal multiple access (NOMA) is investigated in Paper V in which an algorithmic solution is proposed to improve system throughput and fairness.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2016. , 45 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1752
National Category
Communication Systems Telecommunications Computational Mathematics Computer Engineering Signal Processing
Identifiers
URN: urn:nbn:se:liu:diva-126937DOI: 10.3384/diss.diva-126937ISBN: 978-91-7685-804-2 (print)OAI: oai:DiVA.org:liu-126937DiVA: diva2:917891
Public defence
2016-05-16, K3, Kåkenhus, Campus Norrköping, Norrköping, 13:15 (English)
Opponent
Supervisors
Available from: 2016-04-08 Created: 2016-04-08 Last updated: 2016-04-12Bibliographically approved
List of papers
1. A Unified Graph Labeling Algorithm for Consecutive-Block Channel Allocation in SC-FDMA
Open this publication in new window or tab >>A Unified Graph Labeling Algorithm for Consecutive-Block Channel Allocation in SC-FDMA
2013 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 12, no 11, 5767-5779 p.Article in journal (Refereed) Published
Abstract [en]

Optimal channel allocation is a key performance engineering aspect in single-carrier frequency-division multiple access (SC-FDMA). In SC-FDMA with localized channel assignment, the channels of each user must form a consecutive block. Subject to this constraint, various performance objectives, such as maximum utility, minimum power, and minimum number of channels, have been studied. We present a unified graph labeling algorithm for these problems, based on the structural insight that SC-FDMA channel allocation can be modeled as finding an optimal path in an acyclic graph. By this insight, our algorithm applies the concept of labeling and label domination that represent non-trivial extensions of finding a shortest or longest path. The key parameter in trading performance versus computation is the number of labels kept per node. Increasing the number ultimately enables global optimality. The algorithms approach is further justified by its global optimality guarantee with strong polynomial-time complexity for two specific scenarios, where the input is user-invariant and channel-invariant, respectively. For the general case, we provide numerical results demonstrating the algorithms ability of attaining near-optimal solutions.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2013
Keyword
Algorithm, channel allocation, optimization, single carrier frequency division multiple access
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-102855 (URN)10.1109/TWC.2013.092313.130092 (DOI)000328058400034 ()
Note

R)||A*STAR, Singapore||Linkoping-Lund Excellence Center in Information Technology (ELLIIT), Sweden||

Available from: 2014-01-07 Created: 2014-01-02 Last updated: 2017-12-06
2. Resource Scheduling to Jointly Minimize Receiving and Transmitting Energy in OFDMA Systems
Open this publication in new window or tab >>Resource Scheduling to Jointly Minimize Receiving and Transmitting Energy in OFDMA Systems
2014 (English)In: 2014 11TH INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATIONS SYSTEMS (ISWCS), IEEE , 2014, 187-191 p.Conference paper, Published paper (Refereed)
Abstract [en]

Resource scheduling in orthogonal frequency division multiple access (OFDMA) for energy saving has attracted extensive attention. Most current research considers the reduction of energy at the transmitter or the receiver separately. In this paper, we focus on minimizing the energy consumption in both sides concurrently by formulating the problem of joint receiving and transmitting energy-efficient scheduling (RTEES) in OFDMA downlink. We show that this problem can be cast as a binary integer programme. We solve the RTEES problem by a computationally efficient algorithm. We proposed a specialized solution approach, named time-slot-oriented column generation (TSOCG) algorithm, for approaching and bounding the global optimality. Numerical studies show that the proposed algorithm solution is competitive and time-efficient to provide a close-to-optimum solution and a tight bound.

Place, publisher, year, edition, pages
IEEE, 2014
Keyword
Energy saving; column generation; resource allocation; resource scheduling; OFDMA
National Category
Civil Engineering
Identifiers
urn:nbn:se:liu:diva-123094 (URN)000363906500036 ()978-1-4799-5863-4 (ISBN)
Conference
11th International Symposium on Wireless Communications Systems (ISWCS)
Available from: 2015-12-03 Created: 2015-12-03 Last updated: 2016-04-08
3. Power and Load Coupling in Cellular Networks for Energy Optimization
Open this publication in new window or tab >>Power and Load Coupling in Cellular Networks for Energy Optimization
2015 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 14, no 1, 509-519 p.Article in journal (Refereed) Published
Abstract [en]

We consider the problem of minimization of sum transmission energy in cellular networks where coupling occurs between cells due to mutual interference. The coupling relation is characterized by the signal-to-interference-and-noise-ratio (SINR) coupling model. Both cell load and transmission power, where cell load measures the average level of resource usage in the cell, interact via the coupling model. The coupling is implicitly characterized with load and power as the variables of interest using two equivalent equations, namely, non-linear load coupling equation (NLCE) and non-linear power coupling equation (NPCE), respectively. By analyzing the NLCE and NPCE, we prove that operating at full load is optimal in minimizing sum energy, and provide an iterative power adjustment algorithm to obtain the corresponding optimal power solution with guaranteed convergence, where in each iteration a standard bisection search is employed. To obtain the algorithmic result, we use the properties of the so-called standard interference function; the proof is nonstandard because the NPCE cannot even be expressed as a closed-form expression with power as the implicit variable of interest. We present numerical results illustrating the theoretical findings for a real-life and large-scale cellular network, showing the advantage of our solution compared to the conventional solution of deploying uniform power for base stations.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2015
Keyword
Cellular networks; energy minimization; load coupling; power coupling; power adjustment allocation; standard interference function
National Category
Civil Engineering
Identifiers
urn:nbn:se:liu:diva-115830 (URN)10.1109/TWC.2014.2353043 (DOI)000349675400041 ()
Note

Funding Agencies|Linkoping-Lund Excellence Center in Information Technology (ELLIIT), Sweden; Chinese Scholarship Council (CSC); Institute for Infocomm Research (I2R), A*STAR, Singapore

Available from: 2015-03-20 Created: 2015-03-20 Last updated: 2017-12-04
4. Optimal Cell Clustering and Activation for Energy Saving in Load-Coupled Wireless Networks
Open this publication in new window or tab >>Optimal Cell Clustering and Activation for Energy Saving in Load-Coupled Wireless Networks
2015 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 14, no 11, 6150-6163 p.Article in journal (Refereed) Published
Abstract [en]

Optimizing activation and deactivation of base station transmissions provides an instrument for improving energy efficiency in cellular networks. In this paper, we study the problem of performing cell clustering and setting the activation time of each cluster, with the objective of minimizing the sum energy, subject to a time constraint of serving the users traffic demand. Our optimization framework accounts for inter-cell interference, and, thus, the users achievable rates depend on cluster formation. We provide mathematical formulations and analysis, and prove the problems NP hardness. For problem solution, we first apply an optimization method that successively augments the set of variables under consideration, with the capability of approaching global optimum. Then, we derive a second solution algorithm to deal with the trade-off between optimality and the combinatorial nature of cluster formation. Numerical results demonstrate that our solutions achieve more than 40% energy saving over existing schemes, and that the solutions we obtain are within a few percent of deviation from global optimum.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2015
Keyword
Cell activation; cell clustering; energy minimization; load coupling; column generation
National Category
Civil Engineering
Identifiers
urn:nbn:se:liu:diva-123331 (URN)10.1109/TWC.2015.2449295 (DOI)000365046100020 ()
Note

Funding Agencies|European Union FP7 Marie Curie Project MESH-WISE [434515]; European Union FP7 Marie Curie Project WiNDOW [318992]; Chinese Scholarship Council; Institute for Infocomm Research (I2R); A*STAR, Singapore, through overseas Ph.D. research internship scheme; Swedish Research Council; European Union FP7 Marie Curie IOF [329313]

Available from: 2015-12-14 Created: 2015-12-11 Last updated: 2017-12-01

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