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  • 51. Messenger, Jon
    Gschwind, Lutz
    Boehmer, Simon
    Vermeylen, Greet
    Wilkens, Mathijn
    Working anytime, anywhere: The effects on the world of work2017Report (Other (popular science, discussion, etc.))
  • 52.
    Naeser, Gustaf
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computer Systems. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    A flexible framework for detection of feature interactions in telecommunication systems2000Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The complexity of today's telecommunications systems grows with each new feature introduced. As the number of services an operator provides can be used to gain advantage over competitors the number of services will continue to increase. As the complexity grows, so does the possibility for feature interactions, situations where the operation of features interfere with the operation of other features. Interactions cost more to resolve the later during the introduction of a new feature they are detected. This makes the need for analysis of feature interactions during development preeminent.

    There exists a multitude of frameworks and techniques for specification and analysis of models of telecommunications systems. However, we have identified that they often impose unnecessary design decisions on the models, making them untoward.

    In this thesis we propose a framework for specification of models of telecommunications systems. The framework is designed to describe them as general systems of communicating processes in a flexible way which allows alterations to be made late during the design. We also present definitions of interactions and how the interaction definitions are used in the framework to detect undesired interactions.

    A model for telephony systems is derived through observations made of common telephony concepts and constructs. Delving into concepts early in the design of the system is shown to avoid several sources of interactions.

    To demonstrate the potential of the framework we present a case study where the system and services described in the first interaction detection contest has been implemented and searched for interactions.

  • 53.
    Nekouei, Ehsan
    et al.
    Univ Melbourne, Dept Elect & Elect Engn, Parkville, Vic 3010, Australia.
    Inaltekin, Hazer
    Antalya Int Univ, Dept Elect & Elect Engn, Antalya, Turkey.
    Dey, Subhrakanti
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Power control and asymptotic throughput analysis for the distributed cognitive uplink2014In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 64, no 1, p. 41-58Article in journal (Refereed)
    Abstract [en]

    This paper studies optimum power control and sum-rate scaling laws for the distributed cognitive uplink. It is first shown that the optimum distributed power control policy is in the form of a threshold based water-filling power control. Each secondary user executes the derived power control policy in a distributed fashion by using local knowledge of its direct and interference channel gains such that the resulting aggregate (average) interference does not disrupt primary's communication. Then, the tight sum-rate scaling laws are derived as a function of the number of secondary users N under the optimum distributed power control policy. The fading models considered to derive sum-rate scaling laws are general enough to include Rayleigh, Rician and Nakagami fading models as special cases. When transmissions of secondary users are limited by both transmission and interference power constraints, it is shown that the secondary network sum-rate scales according to 1/en(h) log log (N), where n(h) is a parameter obtained from the distribution of direct channel power gains. For the case of transmissions limited only by interference constraints, on the other hand, the secondary network sum-rate scales according to 1/e gamma(g) log (N), where gamma(g) is a parameter obtained from the distribution of interference channel power gains. These results indicate that the distributed cognitive uplink is able to achieve throughput scaling behavior similar to that of the centralized cognitive uplink up to a pre-log multiplier 1/e, whilst primary's quality-of-service requirements are met. The factor 1/e can be interpreted as the cost of distributed implementation of the cognitive uplink.

  • 54. Nijas, C. M.
    et al.
    Deepak, U.
    Vinesh, P. V.
    Raman, Sujith
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Mridula, S.
    Vasudevan, K.
    Mohanan, P.
    Low-Cost Multiple-Bit Encoded Chipless RFID Tag Using Stepped Impedance Resonator2014In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 62, no 9, p. 4762-4770Article in journal (Refereed)
    Abstract [en]

    A novel compact multiple-bit encoded chipless RFID tag using a stepped impedance resonator (SIR) is proposed. The main advantage of SIR compared with other resonators is the independent control over the fundamental as well as first harmonic frequency by varying either the impedance ratio (K) or length ratio (alpha). The tag utilizes both the fundamental and the first harmonic frequency of the SIR to represent two bit information with a single resonator. The tag is capable of representing 2(2N) number of bit combinations with resonators. RFID tags are fabricated on C-MET LK4.3 and (epsilon(r) = 4.3 and tan delta = 0.0018) and RT Duriod (epsilon(r) = 2.2 and tan delta = 0.0009) substrates. The structural information of the tag is encoded in the frequency spectrum, both in the magnitude and group delay of the backscattered signal. The data encoding capacity of the tag is enhanced by using the frequency shift coding technique. The proposed RFID tags have an operating range of 50 cm in the outdoor environment. Theoretical and numerical methods are used to verify the measured resonant frequencies of the tag.

  • 55.
    Nordström, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Gunningberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Tschudin, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology. Datorsystem. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Comparison of Forwarding Strategies in Internet Connected MANETs2004In: ACM SIGMOBILE Mobile Computing Reviews, Vol. 1, no 2Article in journal (Refereed)
    Abstract [en]

    For efficient Internet Connectivity in MANETs, multiple gateways and potentially multihoming and hand-over need to be supported. We compare two forwarding strategies; default routes and tunneling to gateways, and how they support this. We find that tunneling is more efficient and flexible compared to default routes. In fact, we show that default routes will not operate correctly in some situations, particularly when there are multiple gateways.

  • 56. Nourian, Mojtaba
    et al.
    Dey, Subhrakanti
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Ahlén, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Distortion Minimization in Multi-Sensor Estimation With Energy Harvesting2015In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 33, no 3, p. 524-539Article in journal (Refereed)
    Abstract [en]

    This paper presents a design methodology for optimal energy allocation to estimate a random source using multiple wireless sensors equipped with energy harvesting technology. In this framework, multiple sensors observe a random process and then transmit an amplified uncoded analog version of the observed signal through Markovian fading wireless channels to a remote station. The sensors have access to an energy harvesting source, which is an everlasting but unreliable random energy source compared to conventional batteries with fixed energy storage. The remote station or so-called fusion centre estimates the realization of the random process by using a best linear unbiased estimator. The objective is to design optimal energy allocation policies at the sensor transmitters for minimizing total distortion over a finite-time horizon or a long term average distortion over an infinite-time horizon subject to energy harvesting constraints. This problem is formulated as a Markov decision process (MDP) based stochastic control problem and the optimal energy allocation policies are obtained by the use of dynamic programming techniques. Using the concept of submodularity, the structure of the optimal energy allocation policies is studied, which leads to an optimal threshold policy for binary energy allocation levels. Motivated by the excessive communication burden for the optimal control solutions where each sensor needs to know the channel gains and harvested energies of all other sensors, suboptimal decentralized strategies are developed where only statistical information about all other sensors' channel gains and harvested energies is required. Numerical simulation results are presented illustrating the performance of the optimal and suboptimal algorithms.

  • 57.
    Nyström, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computer Systems. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    A formalisation of the ITU-T Intelligent Network standard2000Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Telecommunication systems are today among the largest and most heterogeneous computer systems that exist. The functionality offered by them is rapidly increasing, by numerous features: call waiting, credit-card billing and call-forwarding to name a few.

    The realisation of extra services poses a challenge to implementors, in particular since different services are developed at different times and places, by different people. Not only is the number and complexity of services increasing but some vendors want to enable users to tailor their own services and ultimately design them entirely. This of course calls for rigorous control of the services so that they do not come into conflict with the interest of the vendors, other users or surprise the users with their behaviours.

    One way of aiding the service designers is to provide a service creation environment containing a set of well defined building blocks that would be uniform for all features, irrespective of vendor or service. Such an environment also needs tool support for writing, checking, validating and analysing for possible conflicts.

    We have constructed a formalism for compactly specifying the interface behaviour of the switching and service logic system underlying a service creation environment, and for specifying the behaviour of components of an environment for service creation. For this formalism we supply tool support in the form of a simulator.

    We have further made a formalisation, in our framework, of the ITU-T Intelligent Network model, Capability Set-1. The formalisation concerns both the underlying service architecture, in which service logic is perform by a dedicated Service Control Function, and the component language, in which Service Independent Building Blocks are composed to yield new services.

  • 58.
    Oldoni, Matteo
    et al.
    SIAE Microelettron, R&D Dept, IT-20093 Cologno Monzese, MI, Italy..
    Spinello, Fabio
    Univ Padua, Dept Informat Engn, IT-35131 Padua, Italy.;TwistOff SRL, IT-35129 Padua, Italy..
    Mari, Elettra
    TwistOff SRL, IT-35129 Padua, Italy..
    Parisi, Giuseppe
    TwistOff SRL, IT-35129 Padua, Italy..
    Someda, Carlo Giacomo
    TwistOff SRL, IT-35129 Padua, Italy..
    Tamburini, Fabrizio
    TwistOff SRL, IT-35129 Padua, Italy..
    Romanato, Filippo
    Univ Padua, Dept Phys & Astron G Galilei, IT-35131 Padua, Italy..
    Ravanelli, Roberto Antonio
    SIAE Microelettron, R&D Dept, IT-20093 Cologno Monzese, MI, Italy..
    Coassini, Piero
    SIAE Microelettron, R&D Dept, IT-20093 Cologno Monzese, MI, Italy..
    Thidé, Bo
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Space-Division Demultiplexing in Orbital-Angular-Momentum-Based MIMO Radio Systems2015In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 63, no 10, p. 4582-4587Article in journal (Refereed)
    Abstract [en]

    Radio beams that carry nonzero orbital angular momentum (OAM) are analyzed from the viewpoint of a multiple-input-multiple-output (MIMO) communication system. Often, the natural OAM-beam orthogonality cannot be fully exploited because of spatial constraints on the receiving antenna size. Therefore, we investigate how far OAM-induced phase variations can be exploited in spatial demultiplexing based on conventional (linear momentum) receivers. Performances are investigated versus position and size of the transmitting and receiving devices. The use of OAM-mode coherent superpositions is also considered, in view of recent work by Edfors et al. Our final goal is to assess the merits of an OAM-based MIMO system, in comparison with a conventional one.

  • 59. Phan-Huy, D-T
    et al.
    Sternad, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Svensson, T.
    Chalmers, Sydney, NSW, Australia.;Nokia Bell Labs, Sydney, NSW, Australia..
    Zirwas, W.
    Villeforceix, B.
    Orange Labs, Sydney, NSW, Australia..
    Karim, F.
    Orange Labs, Sydney, NSW, Australia..
    El-Ayoubi, S. -E
    5G on Board: How Many Antennas Do We Need on Connected Cars?2016In: 2016 IEEE GLOBECOM WORKSHOPS (GC WKSHPS), New York: IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    Mobile networks will support increasing numbers of connected vehicles. Successive generations of mobile networks have reduced the cost of data rate, in terms of spectrum usage and power consumption at the base station, by increasingly exploiting the concept of channel state information at the transmitter. Unfortunately, beyond a limiting velocity (which depends on the carrier frequency), networks are no longer cost efficient, since such information is not usable. Recently, channel prediction techniques requiring several antennas on the car roof have been introduced to solve this problem. In this paper, for the first time, we determine the most cost efficient configurations, in terms of numbers of antennas on the car roof and carrier frequency, in various scenarios (highway and dense urban). Our studies show that with a simple prediction technique based on predictor antennas, the network can use twice less spectrum and around 20 dB less power, for cars with 3 antennas on their tops than for cars with the same number of antennas and not using prediction.

  • 60.
    Pérez-Penichet, Carlos
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Hermans, Frederik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    On Limits of Constructive Interference in Backscatter Systems2017In: Global Internet of Things Summit (GIoTS), 2017, IEEE, 2017, p. 178-182Conference paper (Other academic)
    Abstract [en]

    Backscatter communication reduces the energy consumption of resource-constrained sensors and actuators by several orders of magnitude as it avoids the resource-consuming need to generate a radio wave. Many backscatter systems and applications suffer from low communication range. By exploiting the collective power of several tags that transmit the same data simultaneously, constructive interference may help to remedy this problem and increase the communication range. When several tags backscatter the same signal simultaneously it is not necessarily true that constructive interference occurs. As our theoretical results and previous work indicate the interference might also be destructive. Our experimental results on real hardware suggest that exploiting constructive interference to increase the communication range requires careful coordination which is difficult in decentralized settings.

  • 61.
    Pérez-Penichet, Carlos
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Noda, Claro
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication. RISE SICS, Kista, Sweden.
    Augmenting WSNs with Interoperable 802.15.4 Sensor Tags2017In: Proceedings of the 15th ACM Conference on Embedded Networked Sensor Systems, 2017Conference paper (Refereed)
    Abstract [en]

    The sensing capabilities of most sensor networks are fixed at the time of deployment. Adding new sensing capabilities to such networks is a costly and cumbersome process. We present Passive Sensor Tags, battery-free sensing devices that could be used to extend the sensing capabilities of an existing network. Sensor tags feature our new 802.15.4 receiver design which is suitable for micro-power operation, making battery-free tags possible. Because our tags can both transmit and receive 802.15.4 frames there is no need for any modification to the deployed hardware. We present preliminary measurements of transmission and reception range.

  • 62. Rousseaux, O
    et al.
    Leus, G
    Stoica, Peter
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology, Automatic control. Systemteknik.
    Moonen, M
    Gaussian maximum-likelihood channel estimation with short training sequences2005In: IEEE Transactions on Wireless Communication, Vol. 4, p. 2945-2955Article in journal (Refereed)
  • 63.
    Rydberg, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Gruden, Mathias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Selection Algorithms for Enhanced MIMOAntenna Measurements using Mode-Stirred Reverberation Chambers2012In: IEEE Trans. on Antennas and PropagationArticle in journal (Refereed)
  • 64.
    Rydén, Vilhelm
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Outdoor to Indoor Coverage in 5G Networks2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Outdoor to indoor mobile coverage is evaluated for differentfrequencies in two scenarios, a single building scenario and a cityenvironment. A new model for outdoor to indoor propagation issuggested, connecting existing, highly detailed indoor and outdoorray-tracing propagation models. The model is compared to previous,site specific as well as statistical, propagation models. Resultsconclude that the new model gives higher path gain for edge users inthe single building scenario, whereas results from the city scenarioare inconclusive. Furthermore, results from the single buildingscenario suggest that indoor coverage is possible at 5 GHz and belowfor most buildings, whereas for the city scenario indoor coverage at5 GHz will be possible only for buildings without metally coatedwindows. Achieving indoor coverage at 30 GHz is highly problematicfor all cases, and it is concluded that indoor base stations arenecessary if frequencies of 10 GHz and above are to be used infuture mobile networks.

    In addition, an indoor analysis is made to verify existing lossper meter indoor models. It is concluded that such models are oftenoptimistic, although their assumption of log-normal shadowing remainvalid, at least for closed offices. Furthermore, the assumption ofloss as a linear function of distance might be unfeasible for higherfrequencies, where a breakpoint in the linear model was observed ata distance of roughly 10 meters.

  • 65.
    Salimi, Somayeh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Dey, Subhrakanti
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Ahlén, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Sequential Detection of Deception Attacks in Networked Control Systems with Watermarking2019In: 2019 18th European Control Conference (ECC), IEEE, 2019, p. 883-890Conference paper (Refereed)
    Abstract [en]

    In this paper, we investigate the role of a physical watermarking signal in quickest detection of a deception attack in a scalar linear control system where the sensor measurements can be replaced by an arbitrary stationary signal generated by an attacker. By adding a random watermarking signal to the control action, the controller designs a sequential test based on a Cumulative Sum (CUSUM) method that accumulates the log-likelihood ratio of the joint distribution of the residue and the watermarking signal (under attack) and the joint distribution of the innovations and the watermarking signal under no attack. As the average detection delay in such tests is asymptotically (as the false alarm rate goes to zero) upper bounded by a quantity inversely proportional to the Kullback-Leibler divergence(KLD) measure between the two joint distributions mentioned above, we analyze the effect of the watermarking signal variance on the above KLD. We also analyze the increase in the LQG control cost due to the watermarking signal, and show that there is a tradeoff between quick detection of attacks and the penalty in the control cost. It is shown that by considering a sequential detection test based on the joint distributions of residue/innovations and the watermarking signal, as opposed to the distributions of the residue/innovations only, we can achieve a higher KLD, thus resulting in a reduced average detection delay. We also present some new structural results involving the associated KLD and its behaviour with respect to the attacker's signal power and the watermarking signal power. These somewhat non-intuitive structural results can be used by either the attacker to choose their power to minimize the KLD, and/or by the system designer to choose its watermarking signal variance appropriately to increase the KLD. Numerical results are provided to support our claims.

  • 66.
    Soumah, Lucile
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Development, analysis and calibration methods for the dielectric characterization of biomaterials2015Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
  • 67.
    Tran, Martina
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Energy Consumption Optimizations for 5G networks2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The importance of energy efficiency has grown alongside awareness of climate change due to the rapid increase of greenhouse gases. With the increasing trend regarding mobile subscribers, it is necessary to prevent an expansion of energy consumption via mobile networks.

    In this thesis, the energy optimization of the new radio access technology called 5G NR utilizing different sleep states to put base stations to sleep when they are not transmitting data is discussed. Energy savings and file latency with heterogeneous and super dense urban scenarios was evaluated through simulations with different network deployments.

    An updated power model has been proposed and the sensitivity of the new power model was analyzed by adjusting wake-up time and sleep factors. This showed that careful implementation is necessary when adjusting these parameter settings, although in most cases it did not change the end results by much.

    Since 5G NR has more potential in energy optimization compared to the previous generation mobile network 4G LTE, up to 4 sleep states was implemented on the NR base stations and one idle mode on LTE base stations. To mitigate unnecessary sleep, deactivation timers are used which decides when to put base stations to sleep. Without deactivation timers, the delay could increase significantly, while with deactivation timers the delay increase would only be a few percent.

    Up to 42.5% energy could be saved with LTE-NR non-standalone deployment and 72.7% energy with NR standalone deployment compared to LTE standalone deployment, while minimally impacting the delay on file by 1%.

  • 68. Valenta, Vaclav
    et al.
    Spreng, Thomas
    Yuan, Shuai
    Winkler, Wolfgang
    Ziegler, Volker
    Dancila, Dragos
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Rydberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Schumacher, Hermann
    Design and experimental evaluation of compensated bondwire interconnects above 100 GHz2015In: International journal of microwave and wireless technologies, ISSN 1759-0795, E-ISSN 1759-0787, Vol. 7, no 3-4, p. 261-270Article in journal (Refereed)
    Abstract [en]

    Different types of bondwire interconnect for differential chip-to-antenna and single-ended chip-to-chip interfaces are investigated. Two differential compensation structures for various lengths of interconnects are designed and experimentally evaluated using dedicated transmit and receive radar modules operating across a 110-156 GHz band. Measurement results demonstrate that a fractional bandwidth of 7.5% and a minimum insertion loss of 0.2 dB can be achieved for differential interconnects as long as 0.8 mm. Design and measurement results of an extremely wideband low-loss single-ended chip-to-chip bondwire interconnect that features 1.5 dB bandwidth from DC to 170 GHz and insertion loss of less than 1 dB at 140 GHz are presented as well. The results show that the well-established wire-bonding techniques are still an attractive solution even beyond 100 GHz. Reproducibility and scalability of the proposed solutions are assessed as well.

  • 69.
    Willighagen, Egon
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Alvarsson, Jonathan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Andersson, Annsofie
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Cancer Pharmacology and Computational Medicine.
    Eklund, Martin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Lampa, Samuel
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Lapins, Maris
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Spjuth, Ola
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Wikberg, Jarl
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Linking the Resource Description Framework to cheminformatics and proteochemometrics2011In: Journal of Biomedical Semantics, ISSN 2041-1480, E-ISSN 2041-1480, Vol. 2, no Suppl 1, p. 6-Article in journal (Refereed)
    Abstract [en]

    BACKGROUND :

    Semantic web technologies are finding their way into the life sciences. Ontologies and semantic markup have already been used for more than a decade in molecular sciences, but have not found widespread use yet. The semantic web technology Resource Description Framework (RDF) and related methods show to be sufficiently versatile to change that situation.

    RESULTS :

    The work presented here focuses on linking RDF approaches to existing molecular chemometrics fields, including cheminformatics, QSAR modeling and proteochemometrics. Applications are presented that link RDF technologies to methods from statistics and cheminformatics, including data aggregation, visualization, chemical identification, and property prediction. They demonstrate how this can be done using various existing RDF standards and cheminformatics libraries. For example, we show how IC50 and Ki values are modeled for a number of biological targets using data from the ChEMBL database.

    CONCLUSIONS :

    We have shown that existing RDF standards can suitably be integrated into existing molecular chemometrics methods. Platforms that unite these technologies, like Bioclipse, makes this even simpler and more transparent. Being able to create and share workflows that integrate data aggregation and analysis (visual and statistical) is beneficial to interoperability and reproducibility. The current work shows that RDF approaches are sufficiently powerful to support molecular chemometrics workflows.

  • 70. Xu, Y
    et al.
    Liu, F
    Wu, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Interference management for D2D communications in heterogeneous cellular networks2018In: Pervasive and Mobile Computing, ISSN 1574-1192, E-ISSN 1873-1589, Vol. 51, p. 138-149Article in journal (Refereed)
    Abstract [en]

    Device-to-device (D2D) communications in cellular networks enable user equipments (UEs) to directly communicate with each other without the relay of base stations (BSs). They can improve network performance, while they also complicate interference management (IM). In this paper, the IM issue is studied for the D2D communications underlaying heterogeneous networks consisting of macro and small cells. Investigation is first made into D2D performance for UEs in different communication modes (D2D mode and device-to-cell modes). Then, a D2D feasible set is defined and derived which gives a region to allow D2D links to share network resource; and a feasible set scheme is proposed to manage the interference among communication links in order for the cellular links and D2D links to satisfy quality of service (QoS) requirements. After this, the optimal deployment of small cells is studied and an optimal deployment scheme is found that maximizes the transmission density while the QoS of links in different communication modes can be guaranteed. The analytical results are obtained and the calculations show that the proposed interference management schemes can effectively mitigate interference among cellular links and D2D links; and all the links (macro cell link, small cell link and D2D link) can satisfy the QoS requirement when they are sharing the resources. Compared to the neighbor based scheme, the proposed scheme can reduce the average outage probability up to 92%. In addition, the proposed deployment scheme can maximize the transmission capacity with guaranteed link QoSs.

  • 71. You, L.
    et al.
    Yuan, D.
    Load Optimization With User Association in Cooperative and Load-Coupled LTE Networks2017In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, no 5, p. 3218-3231Article in journal (Refereed)
  • 72.
    You, Lei
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computing Science. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Network Optimization of Evolving Mobile Systems with Presence of Interference Coupling2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The rapid development from 4G to 5G of mobile communications poses significant challenges in providing high rate and capacity, making it more crucial for efficient utilization of time-frequency resource via optimally configuring the network. Mathematical optimization serves as a powerful tool for addressing this type of problems. However, gauging its potential in large-scale cellular networks is non-trivial due to the inherent coupling relation of interference among cells. To address this issue, the dissertation adopts a so-called load-coupling system that mathe-matically formulates the mutual influence caused by radio resource allocation among cells. The model defines the time-frequency resource consumption in each cell as the cell load. The load of one cell governs the interference that the cell generates to the others, since the cell trans-mits more frequently with higher load. The model enables joint optimization of resource al-location in multiple cells with respect to the dynamics of resource occupancy of cells. Under the load coupling model, the dissertation applies mathematical optimization to resolve resource management problems with respect to a number of evolving technologies, such as coordinated multipoint (CoMP) transmission, wireless relays, cloud radio access networks (C-RAN), and non-orthogonal multiple access (NOMA). Six research papers are included in the dissertation. Paper I addresses the question of how network planning and coordination may increase the ef-ficiency of spectrum usage, by jointly optimizing user association and resource allocation with CoMP. Paper II investigates the potential of relay cooperation for energy saving. As an extension of Paper I, Paper III studies the capacity maximization for a target group of users, while keep-ing the quality-of-service (QoS) of other users being strictly met. Paper IV provides a general framework and a series of theoretical analysis for algorithmically enabling resource optimization in multi-cell NOMA with load coupling, where users are allowed to group together for sharing time-frequency resource by successive interference cancellation (SIC). Under this framework, Paper V explores the potential of NOMA networks. For a restricted setup of NOMA, the paper achieves globally optimal resource usage efficiency, in terms of power allocation, user pair se-lection, and time-frequency resource allocation. Finally, Paper VI, serving as a complementary note, overcomes a key obstacle in analyzing convergence of applying load coupling in NOMA networks.

    List of papers
    1. Load Optimization With User Association in Cooperative and Load-Coupled LTE Networks
    Open this publication in new window or tab >>Load Optimization With User Association in Cooperative and Load-Coupled LTE Networks
    2017 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, no 5, p. 3218-3231Article in journal (Refereed) Published
    Keywords
    cooperative communication;integer programming;interference;linear programming;Long Term Evolution;load optimization;user association;cooperative load-coupled LTE networks;cellular networks;inter-cell interference;optimization problems;sum load minimization;maximum load minimization;MinSumL;MinMaxL;mixed integer linear programming based scheme;partial optimality conditions;Interference;Couplings;Load modeling;Resource management;Mathematical model;Optimization;Minimization;Joint transmission;load balancing;load-coupling;heterogeneous networks;resource efficiency
    National Category
    Telecommunications
    Identifiers
    urn:nbn:se:uu:diva-391126 (URN)10.1109/TWC.2017.2676762 (DOI)
    Available from: 2019-08-19 Created: 2019-08-19 Last updated: 2019-08-19
    2. Energy-Aware Wireless Relay Selection in Load-Coupled OFDMA Cellular Networks
    Open this publication in new window or tab >>Energy-Aware Wireless Relay Selection in Load-Coupled OFDMA Cellular Networks
    2017 (English)In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, no 1, p. 144-147Article in journal (Refereed) Published
    Abstract [en]

    We investigate transmission energy minimization via optimizing wireless relay selection in orthogonal-frequency-division multiple access networks. We take into account the impact of the load of cells on transmission energy. We prove the NP-hardness of the energy-aware wireless relay selection problem. To tackle computational complexity, a partial optimality condition is derived for providing insights in respect of designing an effective and efficient algorithm. Numerical results show the resulting algorithm achieves high energy performance.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2017
    Keywords
    Heterogeneous network, wireless relay, OFDMA, energy efficiency
    National Category
    Telecommunications
    Identifiers
    urn:nbn:se:uu:diva-319321 (URN)10.1109/LCOMM.2016.2615604 (DOI)000393788000036 ()
    Available from: 2017-04-10 Created: 2017-04-10 Last updated: 2019-08-19Bibliographically approved
    3. User-centric Performance Optimization with Remote Radio Head Cooperation in C-RAN
    Open this publication in new window or tab >>User-centric Performance Optimization with Remote Radio Head Cooperation in C-RAN
    2020 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 19, no 1, p. 340-353Article in journal (Refereed) Published
    Abstract [en]

    In a cloud radio access network (C-RAN), distributed remote radio heads (RRHs) are coordinated by baseband units (BBUs) in the cloud. The centralization of signal processing provides flexibility for coordinated multipoint transmission (CoMP) of RRHs to cooperatively serve user equipments (UEs). We target enhancing UEs' capacity performance, by jointly optimizing the selection of RRHs for serving UEs, i.e., CoMP selection, and resource allocation. We analyze the computational complexity of the problem. Next, we prove that under fixed CoMP selection, the optimal resource allocation amounts to solving a so-called iterated function. Towards user-centric network optimization, we propose an algorithm for the joint optimization problem, aiming at scaling up the capacity maximally for any target UE group of interest. The proposed algorithm enables network-level performance evaluation for quality of experience.

    Keywords
    Resource management, Quality of service, Optimization, Interference, Quality of experience, Load modeling, Couplings, Cloud radio access network, user-centric network, resource allocation, CoMP
    National Category
    Telecommunications
    Identifiers
    urn:nbn:se:uu:diva-391127 (URN)10.1109/TWC.2019.2944606 (DOI)000508384000025 ()
    Available from: 2019-08-19 Created: 2019-08-19 Last updated: 2020-03-06Bibliographically approved
    4. A Framework for Optimizing Multi-cell NOMA: Delivering Demand with Less Resource
    Open this publication in new window or tab >>A Framework for Optimizing Multi-cell NOMA: Delivering Demand with Less Resource
    Show others...
    2017 (English)In: GLOBECOM 2017 - 2017 IEEE Global Communications Conference, IEEE , 2017Conference paper, Published paper (Refereed)
    Abstract [en]

    Non-orthogonal multiple access (NOMA) allows multiple users to simultaneously access the same time-frequency resource by using superposition coding and successive interference cancellation (SIC). Thus far, most papers on NOMA have focused on performance gain for one or sometimes two base stations. In this paper, we study multi-cell NOMA and provide a general framework for user clustering and power allocation, taking into account inter-cell interference, for optimizing resource allocation of NOMA in multi-cell networks of arbitrary topology. We provide a series of theoretical analysis, to algorithmically enable optimization approaches. The resulting algorithmic notion is very general. Namely, we prove that for any performance metric that monotonically increases in the cells' resource consumption, we have convergence guarantee for global optimum. We apply the framework with its algorithmic concept to a multi-cell scenario to demonstrate the gain of NOMA in achieving significantly higher efficiency.

    Place, publisher, year, edition, pages
    IEEE, 2017
    Series
    IEEE Global Communications Conference, ISSN 2334-0983
    National Category
    Computer Sciences
    Identifiers
    urn:nbn:se:uu:diva-357087 (URN)10.1109/GLOCOM.2017.8254922 (DOI)000428054305033 ()978-1-5090-5019-2 (ISBN)
    Conference
    IEEE Global Communications Conference (GLOBECOM), DEC 04-08, 2017, YourSingapore, Singapore, SINGAPORE
    Available from: 2018-08-10 Created: 2018-08-10 Last updated: 2019-08-19Bibliographically approved
    5. Resource optimization with load coupling in multi-cell NOMA
    Open this publication in new window or tab >>Resource optimization with load coupling in multi-cell NOMA
    Show others...
    2018 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, no 7, p. 4735-4749Article in journal (Refereed) Published
    National Category
    Communication Systems
    Identifiers
    urn:nbn:se:uu:diva-361538 (URN)10.1109/TWC.2018.2830386 (DOI)000438727700036 ()
    Available from: 2018-05-03 Created: 2018-10-01 Last updated: 2019-08-19Bibliographically approved
    6. A Note on Decoding Order in Optimizing Multi-cell NOMA
    Open this publication in new window or tab >>A Note on Decoding Order in Optimizing Multi-cell NOMA
    (English)Manuscript (preprint) (Other academic)
    National Category
    Telecommunications
    Identifiers
    urn:nbn:se:uu:diva-391128 (URN)
    Available from: 2019-08-19 Created: 2019-08-19 Last updated: 2019-08-30
  • 73.
    You, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Liao, Qi
    Nokia Bell Labs, D-70435 Stuttgart, Germany.
    Pappas, Nikolaos
    Linkoping Univ, Dept Sci & Technol, S-60174 Norrkoping, Sweden.
    Yuan, Di
    Linkoping Univ, Dept Sci & Technol, S-60174 Norrkoping, Sweden.
    Resource Optimization With Flexible Numerology and Frame Structure for Heterogeneous Services2018In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, no 12, p. 2579-2582Article in journal (Refereed)
    Abstract [en]

    We explore the potential of optimizing resource allocation with flexible numerology in frequency domain and variable frame structure in time domain, with services of with different types of requirements. We prove the NP-hardness of the problem and propose a scalable optimization algorithm based on linear programming and Lagrangian duality. Numerical results show significant advantages of adopting flexibility in both time and frequency domains for capacity enhancement and meeting the requirements of mission critical services.

  • 74.
    You, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    A Note on Decoding Order in Optimizing Multi-cell NOMAManuscript (preprint) (Other academic)
  • 75.
    You, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    User-centric Performance Optimization with Remote Radio Head Cooperation in C-RAN2020In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 19, no 1, p. 340-353Article in journal (Refereed)
    Abstract [en]

    In a cloud radio access network (C-RAN), distributed remote radio heads (RRHs) are coordinated by baseband units (BBUs) in the cloud. The centralization of signal processing provides flexibility for coordinated multipoint transmission (CoMP) of RRHs to cooperatively serve user equipments (UEs). We target enhancing UEs' capacity performance, by jointly optimizing the selection of RRHs for serving UEs, i.e., CoMP selection, and resource allocation. We analyze the computational complexity of the problem. Next, we prove that under fixed CoMP selection, the optimal resource allocation amounts to solving a so-called iterated function. Towards user-centric network optimization, we propose an algorithm for the joint optimization problem, aiming at scaling up the capacity maximally for any target UE group of interest. The proposed algorithm enables network-level performance evaluation for quality of experience.

  • 76.
    You, Lei
    et al.
    Linkoping Univ, Dept Sci & Technol, S-60174 Linkoping, Sweden..
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science. Linkoping Univ, Dept Sci & Technol, S-60174 Linkoping, Sweden..
    Pappas, Nikolaos
    Linkoping Univ, Dept Sci & Technol, S-60174 Linkoping, Sweden..
    Varbrand, Peter
    Linkoping Univ, Dept Sci & Technol, S-60174 Linkoping, Sweden..
    Energy-Aware Wireless Relay Selection in Load-Coupled OFDMA Cellular Networks2017In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, no 1, p. 144-147Article in journal (Refereed)
    Abstract [en]

    We investigate transmission energy minimization via optimizing wireless relay selection in orthogonal-frequency-division multiple access networks. We take into account the impact of the load of cells on transmission energy. We prove the NP-hardness of the energy-aware wireless relay selection problem. To tackle computational complexity, a partial optimality condition is derived for providing insights in respect of designing an effective and efficient algorithm. Numerical results show the resulting algorithm achieves high energy performance.

  • 77.
    Zachariah, Dave
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Dwivedi, Satyam
    KTH Royal Inst Technol, Dept Elect Engn, SE-10044 Stockholm, Sweden..
    Handel, Peter
    KTH Royal Inst Technol, Dept Elect Engn, SE-10044 Stockholm, Sweden..
    Stoica, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Scalable and Passive Wireless Network Clock Synchronization in LOS Environments2017In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, no 6, p. 3536-3546Article in journal (Refereed)
    Abstract [en]

    Clock synchronization is ubiquitous in wireless systems for communication, sensing, and control. In this paper, we design a scalable system in which an indefinite number of passively receiving wireless units can synchronize to a single master clock at the level of discrete clock ticks. Accurate synchronization requires an estimate of the node positions to compensate the time-of-flight transmission delay in line-of-sight environments. If such information is available, the framework developed here takes position uncertainties into account. In the absence of such information, as in indoor scenarios, we propose an auxiliary localization mechanism. Furthermore, we derive the Cramer-Rao bounds for the system, which show that it enables synchronization accuracy at sub-nanosecond levels. Finally, we develop and evaluate an online estimation method, which is statistically efficient.

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