| 1. |
- Abrahamsson, Olle, 1988-
(författare)
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On Aggregation and Dynamics of Opinions in Complex Networks
- 2024
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis studies two problems defined on complex networks, of which the first explores a conceivable extension of structural balance theory and the other concerns convergence issues in opinion dynamics. In the first half of the thesis we discuss possible definitions of structural balance conditions in a network with preference orderings as node attributes. The main result is that for the case with three alternatives (A, B, C) we reduce the (3!)3 = 216 possible configurations of triangles to 10 equivalence classes, and use these as measures of balance of a triangle towards possible extensions of structural balance theory. Moreover, we derive a general formula for the number of equivalent classes for preferences on n alternatives. Finally, we analyze a real-world data set and compare its empirical distribution of triangle equivalence classes to a null hypothesis in which preferences are randomly assigned to the nodes. The second half of the thesis concerns an opinion dynamics model in which each agent takes a random Bernoulli distributed action whose probability is updated at each discrete time step, and we prove that this model converges almost surely to consensus. We also provide a detailed critique of a claimed proof of this result in the literature. We generalize the result by proving that the assumption of irreducibility in the original model is not necessary. Furthermore, we prove as a corollary of the generalized result that the almost sure convergence to consensus holds also in the presence of a fully stubborn agent which never changes its opinion. In addition, we show that the model, in both the original and generalized cases, converges to consensus also in rth moment.
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| 2. |
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| 3. |
- Boyvalenkov, P., et al.
(författare)
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Refinements of Levenshtein Bounds in q-ary Hamming Spaces
- 2018
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Ingår i: Problems of Information Transmission. - : Pleiades Publishing. - 0032-9460 .- 1608-3253. ; 54:4, s. 329-342
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Tidskriftsartikel (refereegranskat)abstract
- We develop refinements of the Levenshtein bound in q-ary Hamming spaces by taking into account the discrete nature of the distances versus the continuous behavior of certain parameters used by Levenshtein. We investigate the first relevant cases and present new bounds. In particular, we derive generalizations and q-ary analogs of the MacEliece bound. Furthermore, we provide evidence that our approach is as good as the complete linear programming and discuss how faster are our calculations. Finally, we present a table with parameters of codes which, if exist, would attain our bounds.
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| 4. |
- Chandhar, Prabhu, 1986-, et al.
(författare)
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Massive MIMO for Communications With Drone Swarms
- 2018
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Ingår i: IEEE Transactions on Wireless Communications. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1536-1276 .- 1558-2248. ; 17:3, s. 1604-1629
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Tidskriftsartikel (refereegranskat)abstract
- We illustrate the potential of Massive MIMO for communication with unmanned aerial vehicles (UAVs). We consider a scenario, where multiple single-antenna UAVs simultaneously communicate with a ground station (GS) equipped with a large number of antennas. Specifically, we discuss the achievable uplink (UAV to GS) capacity performance in the case of line-of-sight conditions. We develop a realistic geometric model, which incorporates an arbitrary orientation, of the GS and UAV antenna elements to characterize the polarization mismatch loss, which occurs due to the movement and orientation of the UAVs. A closed-form expression for a lower bound on the ergodic rate for a maximum-ratio combining receiver with estimated channel state information is derived. The optimal antenna spacing that maximizes the ergodic rate achieved by an UAV is also determined for uniform linear and rectangular arrays. It is shown that when the UAVs are spherically uniformly distributed around the GS, the ergodic rate per UAV is maximized for an antenna spacing equal to an integer multiple of one-half wavelength.
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| 5. |
- Chandhar, Prabhu, 1986-, et al.
(författare)
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On the Zero-Forcing Receiver Performance for Massive MIMO Drone Communications
- 2018
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Ingår i: 2018 IEEE 19th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538635124 - 9781538635117 - 9781538635131 ; , s. 930-934
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Konferensbidrag (refereegranskat)abstract
- We study the uplink ergodic rate performance of the zero-forcing (ZF) receiver in a Massive multiple-input and multiple-output (MIMO) enabled drone communication system. Considering a 3D geometric model for line-of-sight (LoS) propagation, approximate but accurate analyses of lower and upper bounds on the uplink ergodic rate with estimated channel state information (CSI) are provided.
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| 6. |
- ChengWen, Xing, et al.
(författare)
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Statistically robust resource allocation for distributed multi-carrier cooperative networks
- 2013
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Ingår i: Science China Information Sciences. - : Springer. - 1674-733X .- 1869-1919. ; 56:2, s. 109-121
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we investigate joint subcarrier and power allocation scheme for distributed multi-carrier cooperative networks with imperfect channel state information. Using practical channel estimation algorithms, the statistic model of the channel estimation error is first derived. Then based on the channel error model, the resource allocation scheme aims at maximizing the sum rate of the overall network. Specifically, both subcarrier allocation and power allocation are taken into account. In the subcarrier allocation, a realistic problem of the power leakage between neighboring subcarriers is also addressed. Furthermore, based on Lagrange dual-decomposition algorithm, a practical power allocation algorithm is proposed. Finally, the simulation results demonstrate the performance advantages of the proposed robust design.
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| 7. |
- Danev, Danyo, 1973-, et al.
(författare)
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A Family of Constacyclic Ternary Quasi-Perfect Codes with Covering Radius 3
- 2009
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Ingår i: Proceedings of the International Workshop on Coding and Cryptography (WCC'09). ; , s. 111-118
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Konferensbidrag (refereegranskat)abstract
- In this paper a family of constacyclic ternary quasi-perfect linearblock codes is presented. This family extends the result presented ina previous work by the first two authors, where the existence of codeswith the presented parameters was stated as an open question. The codes have a minimum distance 5 and covering radius 3.
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| 8. |
- Danev, Danyo, 1973-, et al.
(författare)
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A Family of Ternary Quasi-Perfect BCH Codes
- 2008
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Ingår i: Designs, Codes and Cryptography. - : Springer Science and Business Media LLC. - 0925-1022 .- 1573-7586. ; 49, s. 265-271
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a family of ternary quasi-perfect BCH codes. These codes are of minimum distance 5 and covering radius 3. The first member of this family is the ternary quadratic-residue code of length 13.
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| 9. |
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| 10. |
- Danev, Danyo, 1973-, et al.
(författare)
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Efficient Message-Passing Decoding of LDPC Codes using Vector-based Messages
- 2006
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Konferensbidrag (refereegranskat)abstract
- In this paper we investigate reduced complexitydecoders for LDPC codes over M-PSK modulation. Capacitycalculations show only minor losses if only phase informationis considered in the decoder. We device a decoder based onphase angle summation, which unfortunately does not work forcodes over Galois fields (but shows promising results for codesover integer rings). For codes over Galois Fields we constructtable-based decoders which gives performance close to BeliefPropagation decoders at substantially reduced complexity.
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| 11. |
- Danev, Danyo, 1973-, et al.
(författare)
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Multiple Access Adder Channel
- 2007
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Ingår i: Multiple Access Channels - Theory and Practice. - Amsterdam : IOS Press. - 9781586037284 - 1586037285 ; , s. 26-53
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- While multiple-access communication dates back to systems invented in the 1870's to transmit simultaneous data through a single wire, the foundation of the discipline now known as 'multiuser information theory' was laid in 1961, when Claude E. Shannon published his paper on two-way channels. Since then, multiuser information theory has been an extremely active research area, and has seen a large number of fundamental contributions, covering, besides the two-way channel studied in, multiple access, interference, broadcast, and wiretap channels. However, several key canonical problems have defied many efforts. This book brings together leading experts working in the fields of information theory, coding theory, multiple user communications, discrete mathematics, etc., who survey recent and general results on multiple-access channels (rate regions, rate splitting, etc.), and give an overview of the problems of current CDMA solutions (fading channels, multi-user detection, multiple-antenna systems, iterative joint decoding, OFDMA, etc.). This publication consist of three parts. The first part includes chapters devoted to the information-theoretical aspects of multiple-access communication. In the second part, multiple-access techniques are discussed and the third part of this volume covers coding techniques
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| 12. |
- Danev, Danyo, 1973-, et al.
(författare)
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Multiple Access Euclidean Channel
- 2007
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Ingår i: Multiple Access Channels - Theory and Practice. - Amsterdam : IOS Press. - 9781586037284 - 1586037285 ; , s. 54-72
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- While multiple-access communication dates back to systems invented in the 1870's to transmit simultaneous data through a single wire, the foundation of the discipline now known as 'multiuser information theory' was laid in 1961, when Claude E. Shannon published his paper on two-way channels. Since then, multiuser information theory has been an extremely active research area, and has seen a large number of fundamental contributions, covering, besides the two-way channel studied in, multiple access, interference, broadcast, and wiretap channels. However, several key canonical problems have defied many efforts. This book brings together leading experts working in the fields of information theory, coding theory, multiple user communications, discrete mathematics, etc., who survey recent and general results on multiple-access channels (rate regions, rate splitting, etc.), and give an overview of the problems of current CDMA solutions (fading channels, multi-user detection, multiple-antenna systems, iterative joint decoding, OFDMA, etc.). This publication consist of three parts. The first part includes chapters devoted to the information-theoretical aspects of multiple-access communication. In the second part, multiple-access techniques are discussed and the third part of this volume covers coding techniques
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| 13. |
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| 14. |
- Danev, Danyo, 1973-
(författare)
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On Signal Detection Techniques for the DVB-T Standard
- 2010
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Ingår i: Proceedings of the International Symposium on Communications, Control and Signal Processing (ISCCSP). ; , s. 1-5
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper we discuss some spectrum sensing techniques for detection of DVB-T signals. Their performance is compared in terms of probability of detection and ROC curves. Some simulation results are presented for various scenarios.
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| 15. |
- Jorswieck, Eduard A., et al.
(författare)
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Complete Characterization of the Pareto Boundary for the MISO Interference Channel
- 2008
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Ingår i: IEEE Transactions on Signal Processing. - 1053-587X .- 1941-0476. ; 56:10, s. 5292-5296
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Tidskriftsartikel (refereegranskat)abstract
- In this correspondence, we study the achievable rate region of the multiple-input single-output (MISO) interference channel, under the assumption that all receivers treat the interference as additive Gaussian noise. Our main result is an explicit parametrization of the Pareto boundary for an arbitrary number of users and antennas. The parametrization describes the boundary in terms of a low-dimensional manifold. For the two-user case we show that a single real-valued parameter per user is sufficient to achieve all points on the Pareto boundary and that any point on the Pareto boundary corresponds to beamforming vectors that are linear combinations of the zero-forcing (ZF) and maximum-ratio transmission (MRT) beamformers. We further specialize the results to the MISO broadcast channel (BC). A numerical example illustrates the result.
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| 16. |
- Larsson, Erik G., 1974-, et al.
(författare)
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Accuracy Comparison of LS and Squared-Range LS for Source Localization
- 2010
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Ingår i: IEEE Transactions on Signal Processing. - : IEEE. - 1053-587X .- 1941-0476. ; 58:2, s. 916-923
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Tidskriftsartikel (refereegranskat)abstract
- In this correspondence we compute a closed-form expression for theasymptotic (large-sample) accuracy of the recently proposedsquared-range least-squares (SR-LS) method for source localization. We compare its accuracy to that of the classicalleast-squares (LS) method and show that LS and SR-LS performdifferently in general. We identify geometries where theperformances of the methods are identical but also geometries when thedifference in performance is unbounded.
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| 17. |
- Larsson, Erik G., 1974-, et al.
(författare)
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Asymptotically Optimal Transmit Strategies for the Multiple Antenna Interference Channel
- 2008
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Ingår i: Proceedings of the 46th Annual Allerton Conference on Communication, Control, and Computing (Allerton'08). ; , s. 708-714
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Konferensbidrag (refereegranskat)abstract
- We consider the interference channel with multiple antennas at the transmitter. We prove that at high signal-to-noise ratio (SNR), the zero-forcing transmit scheme is optimal in the sum-rate sense. Furthermore we prove that at low SNR, maximum-ratio transmission is optimal in the sum-rate sense. We also provide a discussion of the connection to classical results on spectral efficiency in the wideband regime. Finally, we propose a non-convex optimization approach based on monotonic optimization to solve the sum rate maximization problem.
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| 18. |
- Larsson, Erik G., 1974-, et al.
(författare)
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Teaching the Principles of Massive MIMO : Exploring reciprocity-based multiuser MIMO beamforming using acoustic waves
- 2017
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Ingår i: IEEE signal processing magazine (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1053-5888 .- 1558-0792. ; 34:1, s. 40-47
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Tidskriftsartikel (refereegranskat)abstract
- Massive multiple-input, multiple-output (MIMO) is currently the most compelling wireless physical layer technology and a key component of fifth-generation (5G) systems. The understanding of its core principles has emerged during the last five years, and material is becoming available that is rigorously refined to focus on timeless fundamentals [1], facilitating the instruction of the topic to both master- and doctoral-level students [2]. Meaningful laboratory work that exposes the operational principles of massive MIMO is more difficult to accomplish. At Linköping University, Sweden, this was achieved through a project course, based on the conceive-design-implement-operate (CDIO) concept [3], and through the creation of a specially designed experimental setup using acoustic signals.
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| 19. |
- Roth, Stefan, et al.
(författare)
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Subframe allocation for relay networks in the LTE advanced standard
- 2010
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Ingår i: Proceedings of IEEE 21st International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), 2010. - 9781424480173 ; , s. 1758-1763
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Konferensbidrag (refereegranskat)abstract
- The use of relays is a promising way to extend coverage and increase rates in Long Term Evolution Advanced (LTE Advanced) networks. Performing a transmission in several hops (BS-relay & relay-user) requires more radio resources than a single hop transmission. This paper analyses how the available radio resource should be allocated between relays and users in order to maximize throughput and/or fairness. Time and frequency multiplexed backhaul is investigated under some basic assumptions on the division of the radio resource. It is shown that the system will typically be backhaul limited and that the two ways of multiplexing will perform equally when fairness is taken into account. The analysis results in throughput/fairness suboptimal solutions, dependant on the number of relays per cell, spectral efficiencies and fraction of users served by relays. The analysis is verified by simulations, performed using a MATLAB based network simulator.
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| 20. |
- Tumula V.K., Chaitanya, et al.
(författare)
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Constant envelope signal space diversity
- 2014
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Ingår i: Proceedings of the 2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). - : IEEE conference proceedings. ; , s. 3147-3151
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Konferensbidrag (refereegranskat)abstract
- 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).
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| 21. |
- ZeSong, Fei, et al.
(författare)
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Power allocation for OFDM-based cognitive heterogeneous networks
- 2013
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Ingår i: Science China Information Sciences. - : Springer. - 1674-733X .- 1869-1919. ; 56:4, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the capacity maximization and the spectrum utilization efficiency improvement are investigated for the Pico cells in broadband heterogeneous networks. In frequency-reuse model, the users attached to Macro base station are usually viewed as primary users, and those attached to Pico base station should be regarded as cognitive radio (CR) users. As both the primary users and the CR users communicate in parallel frequency bands, the performance of the system is limited by the mutual inter-carrier interference (ICI). In order to control ICI and maximize the achievable transmission rate of the CR users, an effective power allocation scheme is proposed to maximize the transmission rate of the CR users under a given interference threshold prescribed by the primary users. By transforming this suboptimal solution into an innovative matrix expression, the algorithm is easier to perform in practice. The simulation results demonstrate that the proposed algorithm provides a large performance gain in Pico cell capacity over the non-cooperative and equal power allocation schemes.
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