Change search
Link to record
Permanent link

Direct link
Publications (10 of 64) Show all publications
Wu, Z., Yun, Y., Gao, R., Miao, Z., Lennerstad, H. & Xiao, L. (2022). A wide-band all-metal and high-gain omnidirectional antenna with simple prototype. International Journal of RF and Microwave Computer-Aided Engineering, 32(1), Article ID e22936.
Open this publication in new window or tab >>A wide-band all-metal and high-gain omnidirectional antenna with simple prototype
Show others...
2022 (English)In: International Journal of RF and Microwave Computer-Aided Engineering, ISSN 1096-4290, E-ISSN 1099-047X, Vol. 32, no 1, article id e22936Article in journal (Refereed) Published
Abstract [en]

An all-metal dipole two-element array antenna is proposed to achieve a wide-band impedance bandwidth and an omnidirectional radiation pattern. The concept of this antenna derives from a quarter-shorted magnetic dipole structure. The proposed antenna consists of an air-filled metallic parallel bi-plate and two dipole elements. The dipole elements are perpendicularly fabricated at the open end of the bi-plate. Fed by a single coaxial SMA connector in the center of this structure, a quasi-TEM mode in the bi-plate can be excited similar to the parallel waveguide. Based on the multiple resonances and line-array effect, the proposed antenna can achieve a wide-band working bandwidth and a stable omnidirectional pattern. Simulated and experimental results confirm that this antenna has a peak gain of 4.16 dBi and a relative impedance bandwidth of 72% (0.8-1.7 GHz). The proposed antenna can be used in UAV (unmanned aerial vehicle) application.

Place, publisher, year, edition, pages
WILEY, 2022
Keywords
all-metal; dipole; omnidirectional; wide-band
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Communication Systems
Identifiers
urn:nbn:se:bth-22223 (URN)10.1002/mmce.22936 (DOI)000704290300001 ()2-s2.0-85116442361 (Scopus ID)
Available from: 2021-10-21 Created: 2021-10-21 Last updated: 2022-01-11Bibliographically approved
Wu, Z., Yun, Y., Miao, Z. & Lennerstad, H. (2021). A single-layer high-gain dipole antenna array with a bidirectional radiation pattern based on parallel-strip line. IET Microwaves, Antennas & Propagation, 15(3), 323-331
Open this publication in new window or tab >>A single-layer high-gain dipole antenna array with a bidirectional radiation pattern based on parallel-strip line
2021 (English)In: IET Microwaves, Antennas & Propagation, ISSN 1751-8725, E-ISSN 1751-8733, Vol. 15, no 3, p. 323-331Article in journal (Refereed) Published
Abstract [en]

A single-layer dipole antenna array with quasi-Yagi configuration has been proposed and demonstrated, which provides a dual radiation pattern with the same sense. This antenna is mainly composed of a substrate-supported parallel strip line (PSL) and several periodic dipole elements. Fed by PSL, dipole elements can be stimulated with a uniform power, forming a linear dipole antenna array. By adjusting the elements separation appropriately, the step phase of array factor can be tuned to achieve the same directivity as the element dipole. When an SubMiniature version A (SMA) coaxial connector is connected at the beginning of PSL, the fundamental mode TEM in the PSL is excited and the radiation electromagnetic wave from the dipole elements is achieved. A taper line between the SMA and PSL can be used to reduce the discontinuity, minimizing the reflection coefficient of the port. According to the theory of classical Yagi antenna, the gain can be further improved by introducing multiple directors, achieving the gain increment of about 3 dBi in the proposed design. Considering 5 GHz frequency band applications (4.85-5.2 GHz), the experimental and simulated results show the proposed antenna array has a working bandwidth (|S11|<=-10dB) from 4.85 to 12 GHz.

Place, publisher, year, edition, pages
WILEY, 2021
Keywords
Dipole antennas, Directional patterns (antenna), Directive antennas, Microwave antennas, Strip telecommunication lines
National Category
Telecommunications Communication Systems
Identifiers
urn:nbn:se:bth-21303 (URN)10.1049/mia2.12045 (DOI)000623969400008 ()2-s2.0-85112603403 (Scopus ID)
Note

open access

Available from: 2021-04-01 Created: 2021-04-01 Last updated: 2021-08-27Bibliographically approved
Fredriksson, H., Dahl, M., Lövström, B., Holmgren, J. & Lennerstad, H. (2021). Modeling of road traffic flows in the neighboring regions. In: Shakshuki E., Yasar A. (Ed.), Procedia Computer Science: . Paper presented at The 12th International Conference on Emerging Ubiquitous Systems and Pervasive Networks (EUSPN), Leuven, Belgium, November 1-4, 2021 (pp. 43-50). Elsevier
Open this publication in new window or tab >>Modeling of road traffic flows in the neighboring regions
Show others...
2021 (English)In: Procedia Computer Science / [ed] Shakshuki E., Yasar A., Elsevier, 2021, p. 43-50Conference paper, Published paper (Refereed)
Abstract [en]

Traffic flows play a very important role in transportation engineering. In particular, link flows are a source of information about the traffic state, which is usually available from the authorities that manage road networks. Link flows are commonly used in both short-term and long-term planning models for operation and maintenance, and to forecast the future needs of transportation infrastructure. In this paper, we propose a model to study how traffic flow in one location can be expected to reflect the traffic flow in a nearby region. The statistical basis of the model is derived from link flows to find estimates of the distribution of traffic flows in junctions. The model is evaluated in a numerical study, which uses real link flow data from a transportation network in southern Sweden. The results indicate that the model may be useful for studying how large departing flows from a node reflect the link flows in a neighboring geographic region. 

Place, publisher, year, edition, pages
Elsevier, 2021
Series
Procedia Computer Science, E-ISSN 1877-0509 ; 198
Keywords
link flows, traffic volumes, flow distribution, flow estimation, transportation network
National Category
Transport Systems and Logistics
Research subject
Mathematics and applications
Identifiers
urn:nbn:se:bth-22071 (URN)10.1016/j.procs.2021.12.209 (DOI)2-s2.0-85124595881 (Scopus ID)
Conference
The 12th International Conference on Emerging Ubiquitous Systems and Pervasive Networks (EUSPN), Leuven, Belgium, November 1-4, 2021
Note

open access

Available from: 2021-09-01 Created: 2021-09-01 Last updated: 2022-12-02Bibliographically approved
Lundberg, L., Lennerstad, H., Boeva, V. & García Martín, E. (2019). Handling non-linear relations in support vector machines through hyperplane folding. In: ACM International Conference Proceeding Series: . Paper presented at 11th International Conference on Machine Learning and Computing, ICMLC 2019; Zhuhai; China; 22 February 2019 through 24 February (pp. 137-141). Association for Computing Machinery
Open this publication in new window or tab >>Handling non-linear relations in support vector machines through hyperplane folding
2019 (English)In: ACM International Conference Proceeding Series, Association for Computing Machinery , 2019, p. 137-141Conference paper, Published paper (Refereed)
Abstract [en]

We present a new method, called hyperplane folding, that increases the margin in Support Vector Machines (SVMs). Based on the location of the support vectors, the method splits the dataset into two parts, rotates one part of the dataset and then merges the two parts again. This procedure increases the margin as long as the margin is smaller than half of the shortest distance between any pair of data points from the two different classes. We provide an algorithm for the general case with n-dimensional data points. A small experiment with three folding iterations on 3-dimensional data points with non-linear relations shows that the margin does indeed increase and that the accuracy improves with a larger margin. The method can use any standard SVM implementation plus some basic manipulation of the data points, i.e., splitting, rotating and merging. Hyperplane folding also increases the interpretability of the data. © 2019 Association for Computing Machinery.

Place, publisher, year, edition, pages
Association for Computing Machinery, 2019
Keywords
Hyperplane folding, Hyperplane hinging, Non-linear relations, Piecewise linear classification, Support vector machines, Geometry, Piecewise linear techniques, Vectors, Different class, Interpretability, Nonlinear relations, Piecewise linear, Support vector, Support vector machine (SVMs)
National Category
Computer Sciences
Identifiers
urn:nbn:se:bth-18039 (URN)10.1145/3318299.3318319 (DOI)000477981500023 ()2-s2.0-85066460409 (Scopus ID)
Conference
11th International Conference on Machine Learning and Computing, ICMLC 2019; Zhuhai; China; 22 February 2019 through 24 February
Available from: 2019-06-14 Created: 2019-06-14 Last updated: 2021-07-30Bibliographically approved
Lennerstad, H. (2019). The n -dimensional Stern-Brocot tree. International Journal of Number Theory, 15(6), 1219-1236
Open this publication in new window or tab >>The n -dimensional Stern-Brocot tree
2019 (English)In: International Journal of Number Theory, ISSN 1793-0421, Vol. 15, no 6, p. 1219-1236Article in journal (Refereed) Published
Abstract [en]

This paper generalizes the Stern-Brocot tree to a tree that consists of all sequences of n coprime positive integers. As for n = 2, each sequence P is the sum of a specific set of other coprime sequences, its Stern-Brocot set B(P), where |B(P)| is the degree of P. With an orthonormal base as the root, the tree defines a fast iterative structure on the set of distinct directions in ℤ+n and a multiresolution partition of S+n-1. Basic proofs rely on a matrix representation of each coprime sequence, where the Stern-Brocot set forms the matrix columns. This induces a finitely generated submonoid SB(n, ℕ) of SL(n, ℕ), and a unimodular multidimensional continued fraction algorithm, also generalizing n = 2. It turns out that the n-dimensional subtree starting with a sequence P is isomorphic to the entire |B(P)|-dimensional tree. This allows basic combinatorial properties to be established. It turns out that also in this multidimensional version, Fibonacci-type sequences have maximal sequence sum in each generation. © 2019 World Scientific Publishing Company.

Place, publisher, year, edition, pages
World Scientific Publishing Co. Pte Ltd, 2019
Keywords
coprimality, matrix representation, multidimensional continued fraction, S L (n, ℕ), Stern-Brocot tree
National Category
Geometry Mathematical Analysis
Identifiers
urn:nbn:se:bth-17772 (URN)10.1142/S1793042119500672 (DOI)000476732000007 ()2-s2.0-85062921934 (Scopus ID)
Available from: 2019-04-05 Created: 2019-04-05 Last updated: 2019-09-10Bibliographically approved
Sidorova, Y., Sköld, L., Lennerstad, H. & Lundberg, L. (2019). The Use of Fuzzy Logic in Creating a Visual Data Summary of a Telecom Operator’s Customer Base. In: Communications in Computer and Information Science: . Paper presented at 1st International Conference on Intelligent Technologies and Applications, INTAP 2018; Bahawalpur; Pakistan; 23 October 2018 through 25 October 2018 (pp. 301-312). Springer Verlag, 932
Open this publication in new window or tab >>The Use of Fuzzy Logic in Creating a Visual Data Summary of a Telecom Operator’s Customer Base
2019 (English)In: Communications in Computer and Information Science, Springer Verlag , 2019, Vol. 932, p. 301-312Conference paper, Published paper (Refereed)
Abstract [en]

As pointed out by Zadeh, the mission of fuzzy logic in the era of big data is to create a relevant summary of huge amounts of data and facilitate decision-making. In this study, elements of fuzzy set theory are used to create a visual summary of telecom data, which gives a comprehensive idea concerning the desirability of boosting an operator’s presence in different neighborhoods and regions. The data used for validation cover historical mobility in a region of Sweden during a week. Fuzzy logic allows us to model inherently relative characteristics, such as “a tall man” or “a beautiful woman”, and importantly it also defines “anchors”, the situations (characterized with the value of the membership function for the characteristic) under which the relative notion receives a unique crisp interpretation. We propose color coding of the membership value for the relative notions such as “the desirability of boosting operator’s presence in the neighborhood” and “how well the operator is doing in the region”. The corresponding regions on the map (e.g., postcode zones or larger groupings) are colored in different shades passing from green (1) though yellow (0.5) to red (0). The color hues pass a clear intuitive message making the summary easy to grasp. © 2019, Springer Nature Singapore Pte Ltd.

Place, publisher, year, edition, pages
Springer Verlag, 2019
Series
Communications in Computer and Information Science, ISSN 1865-0929 ; 932
Keywords
Call Detail Records, Color, Fuzzy membership function, Mobility data, Computer circuits, Decision making, Fuzzy set theory, Membership functions, Color coding, Customerbase, Membership values, Mobility datum, Telecom operators, Use of fuzzy logic, Fuzzy logic
National Category
Telecommunications
Identifiers
urn:nbn:se:bth-17870 (URN)10.1007/978-981-13-6052-7_26 (DOI)000465006200026 ()9789811360510 (ISBN)
Conference
1st International Conference on Intelligent Technologies and Applications, INTAP 2018; Bahawalpur; Pakistan; 23 October 2018 through 25 October 2018
Available from: 2019-05-02 Created: 2019-05-02 Last updated: 2021-12-09Bibliographically approved
Lennerstad, H. & Eriksson, M. (2018). List graphs and distance-consistent node labelings. Electronic Journal of Graph Theory and Applications, 6(1), 152-165
Open this publication in new window or tab >>List graphs and distance-consistent node labelings
2018 (English)In: Electronic Journal of Graph Theory and Applications, ISSN 2338-2287, Vol. 6, no 1, p. 152-165Article in journal (Refereed) Published
Abstract [en]

In this paper we consider node labelings c of an undirected connected graph G = (V,E) with labels (1, 2, ...,|V|), which induce a list distance c(u, v) = |c(v) - c(u)| besides the usual graph distance d(u, v). Our main aim is to find a labeling c so c(u; v) is as close to d(u, v) as possible. For any graph we specify algorithms to find a distance-consistent labeling, which is a labeling c that minimize Σ u,vεV (c(u, v) - d(u, v))2. Such labeliings may provide structure for very large graphs. Furthermore, we define a labeling c fulfilling d(u1, v1) &lt; d(u2, v2) ) c(u1, v1) ⇒ c(u2, v2) for all node pairs u1; v1 and u2; v2 as a list labeling, and a graph that has a list labeling is a list graph. We prove that list graphs exist for all n = |V| and all k = |E|: n - 1 ≤ k ≤ n(n - 1)/2, and establish basic properties. List graphs are Hamiltonian, and show weak versions of properties of path graphs. © 2018 Indonesian Combinatorics Society.

Place, publisher, year, edition, pages
INST TEKNOLOGI BANDUNG, 2018
Keywords
Extremal combinatorics, Graph distance, Graph labeling
National Category
Mathematics
Identifiers
urn:nbn:se:bth-16110 (URN)10.5614/ejgta.2018.6.1.11 (DOI)000437328400011 ()2-s2.0-85045005282 (Scopus ID)
Available from: 2018-04-19 Created: 2018-04-19 Last updated: 2018-08-20Bibliographically approved
Laksman, E., Lennerstad, H. & Nilsson, M. (2015). Generalized upper bounds on the minimum distance of PSK block codes. IMA Journal of Mathematical Control and Information, 32(2), 305-327
Open this publication in new window or tab >>Generalized upper bounds on the minimum distance of PSK block codes
2015 (English)In: IMA Journal of Mathematical Control and Information, ISSN 0265-0754, E-ISSN 1471-6887, Vol. 32, no 2, p. 305-327Article, review/survey (Refereed) Published
Abstract [en]

This paper generalizes previous optimal upper bounds on the minimum Euclidean distance for phase shift keying (PSK) block codes, that are explicit in three parameters: alphabet size, block length and code size. The bounds are primarily generalized from codes over symmetric PSK to codes over asymmetric PSK and also to general alphabet size. Furthermore, block codes are optimized in the presence of other types of noise than Gaussian, which induces also non-Euclidean distance measures. In some instances, codes over asymmetric PSK prove to give higher Euclidean distance than any code over symmetric PSK with the same parameters. We also provide certain classes of codes that are optimal among codes over symmetric PSK.

Abstract [sv]

Detta papper generaliserar tidigare optimala övre gränser för minimala Euklidiska avståndet för fasskift block koder, s.k. phase shift keying (PSK). De är explicita i tre parametrar: alfabetstorlek, blocklängd och kodstorlek. Gränserna är framförallt generaliserade från koder över symmetrisk PSK till koder över asymmetrisk PSK men även till generell alfabetsstorlek. Block koder är även generaliserade i närvaro av annat brus än gaussiskt, vilket leder till icke-Euklidiska avståndsmått. I vissa fall ger asymmetrisk PSK högre Euklidiskt avstånd än symmetriskt med samma parametrar. Vi visar också att vissa kodklasser är optimala i gruppen av symmetrisk PSK.

Place, publisher, year, edition, pages
Oxford Journals, 2015
Keywords
Assymetric PSK, symmetric PSK, Elias' bound.
National Category
Mathematical Analysis Telecommunications
Identifiers
urn:nbn:se:bth-6608 (URN)10.1093/imamci/dnt047 (DOI)000358779200006 ()oai:bth.se:forskinfo7520A9E3949B10C1C1257D630059B28A (Local ID)oai:bth.se:forskinfo7520A9E3949B10C1C1257D630059B28A (Archive number)oai:bth.se:forskinfo7520A9E3949B10C1C1257D630059B28A (OAI)
Note

Open access article

Available from: 2014-10-03 Created: 2014-09-30 Last updated: 2017-12-04Bibliographically approved
Niyizamwiyitira, C., Lundberg, L. & Lennerstad, H. (2015). Utilization-Based Schedulability Test of Real-Time Systems on Virtual Multiprocessors. In: 2015 44TH INTERNATIONAL CONFERENCE ON PARALLEL PROCESSING WORKSHOPS: . Paper presented at 44th Annual Conference of the International Conference on Parallel Processing Workshops, (ICPPW), Beijing (pp. 267-276). IEEE Computer Society, 2015-January
Open this publication in new window or tab >>Utilization-Based Schedulability Test of Real-Time Systems on Virtual Multiprocessors
2015 (English)In: 2015 44TH INTERNATIONAL CONFERENCE ON PARALLEL PROCESSING WORKSHOPS, IEEE Computer Society, 2015, Vol. 2015-January, p. 267-276Conference paper, Published paper (Refereed)
Abstract [en]

The number of applications that use virtual systems is growing, and one would like to use this kind of systems also for real-time applications with hard deadlines. Virtual machines with many cores are interesting since the underlying physical infrastructure usually contains many cores. We consider hard real-time tasks that execute on a virtual machine with m cores. Tasks are scheduled globally on the cores using fixed-priority preemptive scheduling. This means that a task can execute on different virtual cores at different instances in time. In order to avoid Dhall’s effect, which may cause task sets with even very low utilization to miss deadlines, we classify tasks into two priority classes, namely heavy and light tasks. Heavy tasks have higher priority than light tasks. For light tasks we use rate monotonic priority assignment. In this paper we propose a utilization-based test that shows if a task set is schedulable or not. If the task set is schedulable the test provides the priority for each task. The input to the test is the task set, the number of cores in the virtual machine (m), a period for the virtual machine with m cores, and the blocking time when a virtual machine does not have access to the underlying hardware in each period. © 2015 IEEE.

Place, publisher, year, edition, pages
IEEE Computer Society, 2015
Series
International Conference on Parallel Processing Workshops, ISSN 1530-2016
Keywords
Interactive computer systems; Java programming language; Multiprocessing systems; Scheduling; Testing, Fixed priority preemptive; Fixed priority scheduling; Hard real-time; Hard real-time task; Multi processor scheduling; Priority assignment; Real-time application; Utilization based tests, Real time systems
National Category
Computer and Information Sciences
Identifiers
urn:nbn:se:bth-11582 (URN)10.1109/ICPPW.2015.27 (DOI)000377378800034 ()2-s2.0-84954511253 (Scopus ID)9781467375894 (ISBN)
Conference
44th Annual Conference of the International Conference on Parallel Processing Workshops, (ICPPW), Beijing
Available from: 2016-02-03 Created: 2016-02-03 Last updated: 2021-05-05Bibliographically approved
Lennerstad, H. (2014). Local Linear Time Convergence of a Primal-Dual Energy Minimization Algorithm for Parallel Processing. In: : . Paper presented at 13th International Symposium on Parallel and Distributed Computing (ISPDC), Marseille. IEEE
Open this publication in new window or tab >>Local Linear Time Convergence of a Primal-Dual Energy Minimization Algorithm for Parallel Processing
2014 (English)Conference paper, Published paper (Refereed)
Abstract [en]

We consider energy minimization by speed-scaling of an open shop multiprocessor with n jobs and m machines. The paper studies the complexity of a primal-dual solution algorithm of [4], which was an open question in that paper.We prove that in a neighbourhood of the solution the complexity of the algorithm is O(mn log(1/ε) if n and m are not equal and ε is the roundoff error of the computer. The paper demonstrates how linearization can be used to investigate the complexity of an algorithm close to the optimum. An estimate of the size of the neighbourhood where the linearization error is smaller than the computer’s roundoff error is also given.

Abstract [sv]

Pappret undersöker en energiminimiseringsalgoritm för en multiprocessor där processorns hastighet kan lokalt varieras för att minimera energin. För en open shop multiprocessor med n tasks och m maskiner studeras effektiviteten för en nyligen publicerad primal-dual algoritm. Nära optimium är dess komplexitet O(mn log(1/ε)) om n och m inte är lika och ε är datorns avrundningsfel. I pappret demonstreras hur linjarisering kan användas för att undersöka en algoritms komplexitet nära optimum. Vi visare också en uppskattning storleken för det område runt optimum där linjariseringsfelet är mindre än datorns avrundningsfel.

Place, publisher, year, edition, pages
IEEE, 2014
Series
International Symposium on Parallel and Distributed Computing, ISSN 2379-5352
Keywords
Open shop multiprocessor, Primal-dual algoritm, Speed-scaling, Complexity, Linearization.
National Category
Mathematical Analysis Computer Sciences
Identifiers
urn:nbn:se:bth-6413 (URN)10.1109/ISPDC.2014.21 (DOI)000360933900019 ()oai:bth.se:forskinfo3286C721500AD2A6C1257DF000334A06 (Local ID)978-1-4799-5918-1 (ISBN)oai:bth.se:forskinfo3286C721500AD2A6C1257DF000334A06 (Archive number)oai:bth.se:forskinfo3286C721500AD2A6C1257DF000334A06 (OAI)
Conference
13th International Symposium on Parallel and Distributed Computing (ISPDC), Marseille
Note

Published in proceedings of 2014 IEEE 13th International Symposium on Parallel and Distributed Computing (ISPDC), http://ieeexplore.ieee.org/xpl/mostRecentIssue.jsp?punumber=6898623

Available from: 2015-02-18 Created: 2015-02-18 Last updated: 2018-01-11Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5389-6179

Search in DiVA

Show all publications