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Publications (10 of 215) Show all publications
Hossain, M. I., Azari, A., Markendahl, J. & Zander, J. (2017). Enhanced Random Access:: Initial Access Load Balance in HighlyDense LTE-A Networks for Multiservice (H2H-MTC) Traffic. In: : . Paper presented at IEEE ICC 2017 Mobile and Wireless Networking (pp. 1-7). IEEE
Open this publication in new window or tab >>Enhanced Random Access:: Initial Access Load Balance in HighlyDense LTE-A Networks for Multiservice (H2H-MTC) Traffic
2017 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The Random Access (RA) procedure in existing cellular networks is not capable of functioning properly during high access load conditions. For this purpose, overload control mechanisms are needed. Most proposed mechanisms in the literature offer a tradeoff between access rate and experienced delays. However, when the maximal tolerated delay and the energy spent on retransmissions are tightly bounded, the very high access rate, targeted for 5G systems, cannot be achieved. For these situations, we propose the Delay Estimation based RA (DERA)-scheme that has the potential to meet very stringent reliability requirements, even in high access load conditions. The present work shows that this goal can be achieved only at the cost of limited additional complexity. Furthermore, we also study the optimal switchover point at which the proposed scheme moves from low-load to the high-load phase. The derived tool can also be used along with other proposed RA overload control schemes, e.g.when to invoke access class barring. The performance evaluation results show that the novel DERA scheme can significantly improve the control channels’ resource utilization along with the success rate in dense deployment scenarios.

Place, publisher, year, edition, pages
IEEE, 2017
Keywords
Random access, PRACH, 5G, Machine to machine communications, Propagation delay, contention.
National Category
Communication Systems
Research subject
Information and Communication Technology
Identifiers
urn:nbn:se:kth:diva-214960 (URN)10.1109/ICC.2017.7996622 (DOI)2-s2.0-85028360554 (Scopus ID)978-1-4673-9000-2 (ISBN)
Conference
IEEE ICC 2017 Mobile and Wireless Networking
Projects
H2020 project METIS-II
Funder
Wireless@kth
Note

QC 20171002

Available from: 2017-09-26 Created: 2017-09-26 Last updated: 2017-10-02Bibliographically approved
Tombaz, S., Sung, K. W., Han, S. W. & Zander, J. (2016). An economic viability analysis on energy-saving solutions for wireless access networks. Computer Communications, 75, 50-61
Open this publication in new window or tab >>An economic viability analysis on energy-saving solutions for wireless access networks
2016 (English)In: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703X, Vol. 75, p. 50-61Article in journal (Refereed) Published
Abstract [en]

As the energy bill for mobile operators rises with the continuing traffic growth, energy efficiency problems attract an increasing attention in the telecommunication industry. However, the investment for the implementation of any energy-saving solution could be so costly that it may not achieve the total cost reduction. Therefore, the economic viability of the proposed solutions is of substantial importance for the operators in the process of investment decisions. In this paper, we present a methodology for assessing the economic viability of energy-saving solutions. We conduct two case studies using the proposed methodology, and analyze the cost-benefit tradeoff for: (i) hardware upgrade enabling dynamic sleep mode operation at the base stations (BSs), and (ii) energy efficient network deployment minimizing the network energy consumption. Simulation results show that the hardware upgrade can save up to 60% of energy consumption particularly when the high data rate requirement forces low network resource utilization. Consequently, the solution is shown to be increasingly cost effective as the unit energy cost increases. Network deployment optimized for energy efficiency is shown to bring about further energy savings, but it demands denser deployment of BSs. Thus, it is not deemed as economically viable considering today's cost values.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Energy efficiency, Economic viability, Network planning, Cell DTX, Total cost of investment
National Category
Energy Systems
Identifiers
urn:nbn:se:kth:diva-184553 (URN)10.1016/j.comcom.2015.10.005 (DOI)000371843300004 ()2-s2.0-84959062279 (Scopus ID)
Note

QC 20160406

Available from: 2016-04-06 Created: 2016-04-01 Last updated: 2017-11-30Bibliographically approved
Han, S.-W. -., Kim, H., Han, Y., Cioffi, J. M., Leung, V. C. & Zander, J. (2016). Cooperative multiple access in cognitive radios to enhance QoS for cell edge primary users: asynchronous algorithm and convergence. Telecommunications Systems, 61(4), 631-643
Open this publication in new window or tab >>Cooperative multiple access in cognitive radios to enhance QoS for cell edge primary users: asynchronous algorithm and convergence
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2016 (English)In: Telecommunications Systems, ISSN 1018-4864, E-ISSN 1572-9451, Vol. 61, no 4, p. 631-643Article in journal (Refereed) Published
Abstract [en]

Cognitive radio (CR) systems have been proposed for efficient usage of spare spectrum licensed to primary systems. This leads to the issue of providing as much spectrum to CR users as possible while not degrading the quality of service (QoS) of primary users of the spectrum. This paper proposes a novel cooperation scheme between primary and CR users to guarantee QoS of primary users up to the cell edge while making the licensed spectrum available for opportunistic access by the CR users. We suggest that the primary users at the cell edge, who have poor QoS, should allow secondary users to access their spectrum, while at the same time, the secondary users would help to enhance the primary users QoS using superposition coding on the primary users transmissions. Thus the proposed method can provide a so called “win-win strategy” by benefiting both primary and CR users. The proposed cooperative access scheme in cognitive radios solves efficiently the sum-rate maximization problem on cognitive Gaussian Multiple Access Channels (GMACs) for power allocation of primary systems that cooperates with CR systems in a distributed fashion. We solved the problem using iterative Jacobian method in a distributed manner. A totally asynchronous distributed power allocation for sum-rate maximization on cognitive GMACs is suggested. Numerical results show that the QoS of primary users at the cell edge is improved by the proposed cooperative access scheme.

Place, publisher, year, edition, pages
Springer-Verlag New York, 2016
Keywords
Cell edge primary users, Cognitive radio, Distributed power allocation, Non-convex QCQP, Sum-rate maximization, Algorithms, Cells, Cognitive systems, Communication channels (information theory), Cytology, Iterative methods, Quality of service, Radio systems, Asynchronous algorithms, Cooperative multiple access, Distributed Power-Allocation, Gaussian multiple-access channels, Primary Users, Sum-rate maximizations, Super-position coding
National Category
Computer and Information Sciences
Identifiers
urn:nbn:se:kth:diva-176240 (URN)10.1007/s11235-015-0058-x (DOI)000371417000002 ()2-s2.0-84959540807 (Scopus ID)
Note

QC 20151116. QC 20160407

Available from: 2015-11-16 Created: 2015-11-02 Last updated: 2018-01-10Bibliographically approved
Miao, G., Zander, J., Sung, K. W. & Slimane, S. B. (2016). Fundamentals of Mobile Data Networks. Cambridge: Cambridge University Press
Open this publication in new window or tab >>Fundamentals of Mobile Data Networks
2016 (English)Book (Other academic)
Place, publisher, year, edition, pages
Cambridge: Cambridge University Press, 2016
Keywords
Wireless Networks, Wireless Communication, Cellular Systems
National Category
Communication Systems
Research subject
SRA - ICT; Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-185815 (URN)978-1-107-14321-0 (ISBN)
Note

QC 20160623

Available from: 2016-04-28 Created: 2016-04-28 Last updated: 2016-06-23Bibliographically approved
Obregon, E. C., Sung, K. W. & Zander, J. (2016). Is spectrum sharing in the radar bands commercially attractive?: -a regulatory and business overview. European transactions on telecommunications, 27(3), 428-438
Open this publication in new window or tab >>Is spectrum sharing in the radar bands commercially attractive?: -a regulatory and business overview
2016 (English)In: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 27, no 3, p. 428-438Article in journal (Refereed) Published
Abstract [en]

The need to meet users' expectations in the 'mobile data avalanche' represents a significant challenge for mobile network operators. More spectrum is a natural way to meet these requirements in a cost and time-efficient way, but new, exclusively licenced spectrum is increasingly hard to come by. Instead, vertical spectrum sharing has been discussed as a potential solution for finding additional spectrum. In this paper, we focus on vertical spectrum sharing in the radar bands for providing short-range wireless access, for example, indoors and in hotspots that 'offload' traffic demand. We propose a methodology for analysing the technical, regulatory and business aspects of deploying large-scale wireless networks. Then, we identify the following criteria for achieving business success: spectrum availability, availability of low-cost end-user devices, system scalability in terms of number of concurrently used devices and finally the ability to guarantee a quality of service for the users. Our technical availability assessment has identified geo-location database as the necessary technical enabler and detect-and-avoid mechanism as an auxiliary enabler for improving sharing conditions. Moreover, licenced shared access was found to be the suitable regulatory framework to support the proposed sharing mechanism and regulatory policies in real-life implementation. Our business feasibility assessment concludes that there is enough spectrum available for indoor and hotspots communication in urban areas in the radar bands to make a large-scale system commercially viable. Service quality can be guaranteed, and there is a strong potential to construct low-cost devices. Uncertainties do, however, remain regarding the spectrum access cost.

Place, publisher, year, edition, pages
John Wiley & Sons, 2016
Keywords
Costs, Large scale systems, Quality of service, Wireless networks, Availability assessment, Feasibility assessment, Geo-location database, Mobile network operators, Real-life implementations, Regulatory frameworks, Spectrum availability, Vertical spectrum sharing, Radar
National Category
Computer and Information Sciences
Identifiers
urn:nbn:se:kth:diva-176247 (URN)10.1002/ett.2962 (DOI)000371643900009 ()2-s2.0-84959532789 (Scopus ID)
Note

QC 20160401

Available from: 2015-11-13 Created: 2015-11-02 Last updated: 2018-01-10Bibliographically approved
Piunti, P., Cavdar, C., Morosi, S., Teka, K. E., Del Re, E. & Zander, J. (2015). Energy efficient adaptive cellular network configuration with QoS guarantee. In: 2015 IEEE International Conference on Communications (ICC): . Paper presented at IEEE International Conference on Communications, ICC 2015, London, United Kingdom, 8 June 2015 through 12 June 2015 (pp. 68-73). IEEE conference proceedings
Open this publication in new window or tab >>Energy efficient adaptive cellular network configuration with QoS guarantee
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2015 (English)In: 2015 IEEE International Conference on Communications (ICC), IEEE conference proceedings, 2015, p. 68-73Conference paper, Published paper (Refereed)
Abstract [en]

Cellular network energy optimization is driven by different factors, namely transmission power and activity of the base stations. Quality of Service (QoS) of users is determined by received power, interference and bandwidth allocation and cannot be neglected. In existing studies, such drivers are treated separately, i.e., bandwidth allocation is fixed while power consumption is a variable to be optimized. This paper proposes a novel optimization framework which is aimed at minimizing the power consumption in cellular networks while affording a minimum bit rate for each mobile terminal by jointly considering energy consumption and QoS drivers. Mixed Integer Quadratic Programming (MIQP) based optimization framework solves the problems of the determination of the user association, the bandwidth allocation, the identification of the active base stations and their transmission power, guaranteeing also a requested service rate for each user. The proposed solution is shown to allow power savings of up to 60%, very close to the optimum lower bound, when the traffic is below the 35% of the maximum load.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2015
Series
IEEE International Conference on Communications, ISSN 1550-3607
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-181156 (URN)10.1109/ICC.2015.7248300 (DOI)000371708100012 ()2-s2.0-84953726308 (Scopus ID)978-1-4673-6432-4 (ISBN)
Conference
IEEE International Conference on Communications, ICC 2015, London, United Kingdom, 8 June 2015 through 12 June 2015
Note

QC 20160212, OQ 20160421

Available from: 2016-02-12 Created: 2016-01-29 Last updated: 2016-04-21Bibliographically approved
Shi, L., Sung, K. W. & Zander, J. (2015). Future TV Content Delivery Over Cellular Networks From Urban to Rural Environments. IEEE Transactions on Wireless Communications, 14(11), 6177-6187
Open this publication in new window or tab >>Future TV Content Delivery Over Cellular Networks From Urban to Rural Environments
2015 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 14, no 11, p. 6177-6187Article in journal (Refereed) Published
Abstract [en]

With the increasing number of TV channels and the growing need for on-demand services, the traditional digital terrestrial television is becoming a less attractive way of distributing TV content. As an alternative, we discuss a converged platform in the UHF band for TV and mobile broadband provisioning based on LTE cellular technology and infrastructure, which is here referred to as CellTV. The requirement for CellTV is to provide seamless TV coverage from urban to rural environments and to minimize the spectrum requirement so that the leftover can be used for mobile services. We formulate an optimal spectrum allocation problem for CellTV to distribute different TV channels with different transmission modes. Each TV channel is delivered via either unicast links or the broadcast over single-frequency networks of different modulation orders according to the location-dependent viewing demand and the cellular infrastructure availability. Based on a case study of the Greater Stockholm region, we identify that CellTV only requires a small portion of the UHF band to deliver the TV content in urban areas, thus releasing a significant amount of spectra for mobile broadband services. Meanwhile, the spectrum requirement for CellTV is considerably higher in suburban and rural areas due to the transitions of transmission modes. We further generalize these findings to provide a guiding principle for CellTV deployment in mixed environments and to demonstrate the flexibility advantage of CellTV in adapting to the growing diversity of TV content.

Place, publisher, year, edition, pages
IEEE Press, 2015
Keywords
UHF TV band, terrestrial TV broadcasting, multimedia broadcasting/multicast service, single frequency network, unicast video streaming
National Category
Communication Systems Telecommunications
Identifiers
urn:nbn:se:kth:diva-179171 (URN)10.1109/TWC.2015.2449841 (DOI)000365046100022 ()2-s2.0-84959560935 (Scopus ID)
Note

QC 20151214

Available from: 2015-12-14 Created: 2015-12-11 Last updated: 2017-12-01Bibliographically approved
Ullah, I., Sjöstrand, J., Andersson, P., Sennblad, B. & Lagergren, J. (2015). Integrating Sequence Evolution into Probabilistic Orthology Analysis. Systematic Biology, 64(6), 969-982
Open this publication in new window or tab >>Integrating Sequence Evolution into Probabilistic Orthology Analysis
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2015 (English)In: Systematic Biology, ISSN 1063-5157, E-ISSN 1076-836X, Vol. 64, no 6, p. 969-982Article in journal (Refereed) Published
Abstract [en]

Orthology analysis, that is, finding out whether a pair of homologous genes are orthologs - stemming from a speciation - or paralogs - stemming from a gene duplication - is of central importance in computational biology, genome annotation, and phylogenetic inference. In particular, an orthologous relationship makes functional equivalence of the two genes highly likely. A major approach to orthology analysis is to reconcile a gene tree to the corresponding species tree, (most commonly performed using the most parsimonious reconciliation, MPR). However, most such phylogenetic orthology methods infer the gene tree without considering the constraints implied by the species tree and, perhaps even more importantly, only allow the gene sequences to influence the orthology analysis through the a priori reconstructed gene tree. We propose a sound, comprehensive Bayesian MCMC-based method, DLRSOrthology, to compute orthology probabilities. It efficiently sums over the possible gene trees and jointly takes into account the current gene tree, all possible reconciliations to the species tree, and the, typically strong, signal conveyed by the sequences. We compare our method with PrIME-GEM, a probabilistic orthology approach built on a probabilistic duplication-loss model, and MrBayesMPR, a probabilistic orthology approach that is based on conventional Bayesian inference coupled with MPR. We find that DLRSOrthology outperforms these competing approaches on synthetic data as well as on biological data sets and is robust to incomplete taxon sampling artifacts.

Place, publisher, year, edition, pages
Oxford University Press, 2015
Keywords
Comparative genomics, orthology, paralogy, gene duplication, gene loss, sequence evolution, relaxed molecular clock, probabilistic modeling, phylogenetics, tree reconciliation, tree realization
National Category
Bioinformatics (Computational Biology)
Research subject
Computer Science
Identifiers
urn:nbn:se:kth:diva-168167 (URN)10.1093/sysbio/syv044 (DOI)000363168100007 ()2-s2.0-84946111865 (Scopus ID)
Funder
Swedish e‐Science Research CenterSwedish Research Council, 2010-4757Magnus Bergvall Foundation
Note

QC 20151216. Updated from manuscript to article in journal.

Available from: 2015-05-27 Created: 2015-05-27 Last updated: 2018-01-11Bibliographically approved
Ozyagci, A., Sung, K. W. & Zander, J. (2014). Association and deployment considerations in dense wireless LANs. In: Vehicular Technology Conference (VTC Spring), 2014 IEEE 79th: . Paper presented at 2014 79th IEEE Vehicular Technology Conference, VTC 2014-Spring, Seoul, South Korea, 18 May 2014 through 21 May 2014. IEEE conference proceedings
Open this publication in new window or tab >>Association and deployment considerations in dense wireless LANs
2014 (English)In: Vehicular Technology Conference (VTC Spring), 2014 IEEE 79th, IEEE conference proceedings, 2014Conference paper, Published paper (Refereed)
Abstract [en]

Wireless LANs based on the IEEE 802.11 standard are one of the most commonplace indoor wireless access solutions. As the ever growing demand for data consumption necessitates higher rates and volumes, it is fairly common to observe more and more WLANs being deployed in close proximity to each other. As distances between WLAN installations diminish, the access points (APs) and stations (STAs) in these WLANs create a complex interference environment, which is also compounded by the indoor propagation environment. In this paper, we investigate the impact of two important parameters related to the deployment and operation of densely deployed wireless LANs on the aggregate throughput obtained by all the nodes in these WLANs. The first such operational parameter we investigate is access point and user station association; namely, whether STAs associate with a random ``strong'' AP or the AP from which they obtain the strongest received power. The second operational parameter we consider is the way in which APs are placed in the indoor environment; namely, whether APs are deployed randomly or in a manner to reduce inter-AP interference. In order to account for the complex node interactions in the MAC layer, which is crucial for accurate performance estimation, we perform packet-level simulations using OPNET. Our results show that the type of node association used in densely deployed WLANs has a critical impact on the aggregate throughput. In comparison, the type of AP deployment used is not nearly as significant; varying from moderate to no impact at all.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2014
Series
IEEE Vehicular Technology Conference, ISSN 1550-2252
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-154336 (URN)10.1109/VTCSpring.2014.7022839 (DOI)2-s2.0-84936886431 (Scopus ID)
Conference
2014 79th IEEE Vehicular Technology Conference, VTC 2014-Spring, Seoul, South Korea, 18 May 2014 through 21 May 2014
Note

QC 20151214

Available from: 2014-10-17 Created: 2014-10-17 Last updated: 2016-11-11Bibliographically approved
Park, J., Kim, S.-L. -. & Zander, J. (2014). Asymptotic behavior of ultra-dense cellular networks and its economic impact. In: 2014 IEEE Global Communications Conference, GLOBECOM 2014: . Paper presented at 2014 IEEE Global Communications Conference, GLOBECOM 2014, 8 December 2014 through 12 December 2014 (pp. 4941-4946).
Open this publication in new window or tab >>Asymptotic behavior of ultra-dense cellular networks and its economic impact
2014 (English)In: 2014 IEEE Global Communications Conference, GLOBECOM 2014, 2014, p. 4941-4946Conference paper, Published paper (Refereed)
Abstract [en]

This paper investigates the relationship between base station (BS) density and average spectral efficiency (SE) in the downlink of a cellular network. This relationship has been well known for sparse deployment, i.e. when the number of BSs is small compared to the number of users. In this case the SE is independent of BS density. As BS density grows, on the other hand, it has previously been shown that increasing the BS density increases the SE, but no tractable form for the SE-BS density relationship has yet been derived. In this paper we derive such a closed-form result that reveals the SE is asymptotically a logarithmic function of BS density as the density grows. Further, we study the impact of this result on the network operator's profit when user demand varies, and derive the profit maximizing BS density and the optimal amount of spectrum to be utilized in closed forms. In addition, we provide deployment planning guidelines that will aid the operator in his decision if he should invest in densifying his network or in acquiring more spectrum.

Keywords
Average spectral efficiency, Base station density, Network economics, Profit maximization, Spectrum amount, Stochastic geometry, Ultra-dense cellular network, Base stations, Mobile telecommunication systems, Profitability, Stochastic systems, Wireless networks, Cellular network, Mobile security
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-167494 (URN)10.1109/GLOCOM.2014.7037588 (DOI)2-s2.0-84924358331 (Scopus ID)9781479935116 (ISBN)
Conference
2014 IEEE Global Communications Conference, GLOBECOM 2014, 8 December 2014 through 12 December 2014
Note

QC 20150612

Available from: 2015-06-12 Created: 2015-05-22 Last updated: 2015-06-12Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-4986-6123

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