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  • 1.
    Abarghouyi, Hadis
    et al.
    IUST, Iran; MTNi Co, Iran.
    Razavizadeh, S. Mohammad
    IUST, Iran.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    QoE-Aware Beamforming Design for Massive MIMO Heterogeneous Networks2018Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 67, nr 9, s. 8315-8323Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One of the main goals of the future wireless networks is improving the users quality of experience (QoE). In this paper, we consider the problem of the QoE-based resource allocation in the downlink of a massive multiple-input multiple-output heterogeneous network. The network consists of a macrocell with a number of small cells embedded in it. The small cells base stations (BSs) are equipped with a few antennas, while the macro BS is equipped with a massive number of antennas. We consider the two services Video and Web Browsing and design the beamforming vectors at the BSs. The objective is to maximize the aggregated mean opinion score (MOS) of the users under constraints on the BSs powers and the required quality of service of the users. We also consider extra constraints on the QoE of users to more strongly enforce the QoE in the beamforming design. To reduce the complexity of the optimization problem, we suggest suboptimal and computationally efficient solutions. Our results illustrate that increasing the number of antennas at the BSs and also increasing the number of small cells antennas in the network leads to a higher user satisfaction.

  • 2.
    Abdul Aziz Hasan Ali, Aamir
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Shahzad, Muhammad Adil
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    A Joint Subcarrier/Power allocation Scheme for OFDMA-based Cellular Networks2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The assignment of this master thesis consists of initiating power, subcarrier allocation in a dynamic FFR based scheme designed for multi-cell OFDMA networks and to enhance the throughput of all center users in bandwidth hungry borrower cells (overloaded cells) which was previously degraded by original FFR3 scheme as a result of partitioning of system bandwidth into center and edge bands respectively. The method uses band borrowing to compensate center user’s throughput loss in a semi and fully overloaded system. The scheme uses dynamic programming method (0/1 knapsack problem) to bargain an edge band on various power levels and tends to check the best combination (power and sub-carrier) which the system can utilize while still maintaining acceptable throughput loss for the users at the edge of the neighboring cell (lender cell).

    The algorithm consists of generating a borrowing request to neighboring cells for utilizing their edge bands by the overloaded borrower cell if their average center user throughput reaches below a minimum threshold value set in the system. The borrowing method uses 0/1 knapsack problem to capture an edge band based on limiting factors of total cost in average throughput losses by neighbors (Ci) and Un (tolerable mean user edge user throughput loss by lending cell). While solving knapsack problem the lender (neighbors) will check Ci and Un before granting the right to use its edge band. The later stage requires reducing subcarrier power level in order to utilize the lenders edge band using "soft borrower" mode. The borrowed sub-carriers will be activated take power from the original center band sub-carriers of the overloaded cell by taking into account the interference between the lender and the borrower. In case of negative (0) reply from the lender cell after the first request, multiple requests are generated at reduce power level at every step to order to acquire more bands. If a neighbor has band borrowing requests from multiple overloaded base stations, the band will be granted to the one which gives minimal loss in terms of throughput to the lender cell.

    The simulation results are analyzed w.r.t reuse-1 and FFR3 scheme of a multi cell regular and irregular scenarios comprising of lightly to heavily overloaded cells with various subcarrier allocation patterns. An overhead and time assessment is also presented between borrower and lender cells. Simulation results show an increase of 60% in center user’s throughput w.r.t original FFR3 scheme with an acceptable loss of 18% at the edges in complex overloaded scenarios while the overall system throughout increases by 35%.

  • 3.
    Ahmad, Ijaz
    et al.
    University of Oulu, Finland.
    Kumar, Tanesh
    University of Oulu, Finland.
    Liyanage, Madhusanka
    University of Oulu, Finland.
    Okwuibe, Jude
    University of Oulu, Finland.
    Ylianttila, Mika
    University of Oulu, Finland.
    Gurtov, Andrei
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    5G Security: Analysis of Threats and Solutions2017Ingår i: 2017 IEEE CONFERENCE ON STANDARDS FOR COMMUNICATIONS AND NETWORKING (CSCN), IEEE , 2017, s. 193-199Konferensbidrag (Refereegranskat)
    Abstract [en]

    5G will provide broadband access everywhere, entertain higher user mobility, and enable connectivity of massive number of devices (e.g. Internet of Things (IoT)) in an ultrareliable and affordable way. The main technological enablers such as cloud computing, Software Defined Networking (SDN) and Network Function Virtualization (NFV) are maturing towards their use in 5G. However, there are pressing security challenges in these technologies besides the growing concerns for user privacy. In this paper, we provide an overview of the security challenges in these technologies and the issues of privacy in 5G. Furthermore, we present security solutions to these challenges and future directions for secure 5G systems.

  • 4.
    Ahmad, Ijaz
    et al.
    Univ Oulu, Finland.
    Liyanage, Madhusanka
    Univ Oulu, Finland.
    Ylianttila, Mika
    Univ Oulu, Finland.
    Gurtov, Andrei
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Analysis of Deployment Challenges of Host Identity Protocol2017Ingår i: 2017 EUROPEAN CONFERENCE ON NETWORKS AND COMMUNICATIONS (EUCNC), IEEE , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Host Identity Protocol (HIP), a novel internetworking technology proposes separation of the identity-location roles of the Internet Protocol (IP). HIP has been successful from the technological perspectives for network security and mobility, however, it has very limited deployment. In this paper we assess HIP to find the reasons behind its limited deployment and highlight the challenges faced by HIP for its commercial use. We propose technological development and outline deployment strategies for the wide use of HIP. Furthermore, this paper investigates the use of HIP in Software Defined Networks (SDN) to evaluate its performance in new disruptive networking technologies. In a nutshell, this paper presents revealing challenges for the deployment of innovative networking protocols and a way ahead for successful and large scale deployment.

  • 5.
    Ahmed, Atheeq
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem.
    Human Detection Using Ultra Wideband Radar and Continuous Wave Radar2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    A radar works by radiating electromagnetic energy and detecting the reflected signal returned from the target. The nature of the reflected signal provides information about the target’s distance or speed. In this thesis, we will be using a UWB radar and a CW radar to help detect the presence and rough location of trapped survivors by detecting their motions. Range is estimated in the UWB radar using clutter removal with SVD and for the dual frequency CW Radar using STFT and median filtering. The effect of the algorithm parameters on their performance was analyzed. The performance of the implemented algorithms with regards to small motion detection, distance estimation and penetration capability was analyzed. Both systems are certainly capable of human detection and tracking.

  • 6.
    Ahmed, Zubair
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Design of Autonomous Low Power Sensor for Soil Moisture Measurement.2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Drought is the most severe disaster compared to other disasters in human civilization and their impacts are serious which can cause hungur, thrist, food shortages, loss of livestock directly effects the human life. The main objective of this project is to develop an early warning system (EWS) [3] for drought indices by using wireless sensor networks (WSNs) which is the only way forward for an on-site monitoring and validation of locally defined drought indices [3].The designed wireless sensor network (WSN) consisting of a sensor unit, a master unit and a sensor power management unit (PMU). The sensor unit measures the moisture of the soil and transmitt the measured data through ZigBee module to the master unit. A real time clock (RTC) is also used in the sensor unit which records the information of second, minute, hour, day, month of day and year about when or what time the measurement taken. The master unit consisting of a SD-card and Bluetooth module. SD-card is used to store measured data from other sensor units and it is possible to take out the reading of measured data from the master unit by accessing the SD-card via Bluetooth inside the master unit to a PC or a smartphone mobile.To manage the power in the sensor unit and to make sensor alive for several years, the power management unit (PMU) manages the power level between two energy storage buffers (i.e., a supercapacitor and a Li+ ion battery) for a sensor node.

  • 7.
    Ahola, David
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yin To, Jie
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    To be entered/Green Cargo2013Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Schemakonstruktion för järnvägspersonal är en stor utmaning. En orsak är att arbetsuppgifterna vid järnvägen kräver olika kunskaps- och kompetenskrav, samt att det finns många arbetsregler som utgör restriktioner för schemakonstruktionen. I detta examensarbete har en fallstudie utförts för datorstödd schemakonstruktion för personalbemanning. Examensarbetet har utförts vid avdelningen för bemanningsplanering som ansvarar för planering av personal vid två av Green Cargos olika bangårdar. Huvudsyftet med det här examensarbetet är att utreda skillnaderna i scheman som skapats manuellt respektive automatiskt med hjälp av programvaran BP. Schemajämförelserna ska också redovisa nyttan av det automatiska planeringssättet där det finns applicerat. Under arbetet genomfördes litteraturstudier samt en fallstudie. I fallstudien genomfördes testkörningar med olika schemakonstruktionsmetoder på två bangårdar. Det numeriska resultatet visar att den datorassisterade bemanningsmetoden innebär en förbättrad bemanningsplanering ur företagets synvinkel då produktionsbehovet kan täckas utan ökade kostnader. Detta innebär också en ökad flexibilitet i produktionsplaneringen då tjänstgöringsturer enkelt kan ändras. Det gör det också mycket enklare att tilldela personal olika arbetsuppgifter som de har kompetens för. Den optimeringsbaserade bemanningsplanen innebär inte en ökad arbetsbelastning för medarbetaren. Trots att fler bangårdstjänster kan bemannas genom att använda den datorassisterade metoden visar det sig att den totala utlagda arbetstiden inte alls ökar eller att den bara ökar marginellt för vissa medarbetare. När planering sker med programvaran styrs denna av parametrar som är lätta att ändra. Dessa inställningar av parametrar är avgörande för utseendet på schemat. Indata kan vara fridagsplanering, kompetenstillgång och produktionsbehov. De i sin tur avgör i betydande grad på hur balansen mellan livs- och ekonomiska kvalitetsmåtten ser ut för medarbetarna.

  • 8.
    Alesand, Elias
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem.
    Identification of Flying Drones in Mobile Networks using Machine Learning2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Drone usage is increasing, both in recreational use and in the industry. With it comes a number of problems to tackle. Primarily, there are certain areas in which flying drones pose a security threat, e.g., around airports or other no-fly zones. Other problems can appear when there are drones in mobile networks which can cause interference. Such interference comes from the fact that radio transmissions emitted from drones can travel more freely than those from regular UEs (User Equipment) on the ground since there are few obstructions in the air. Additionally, the data traffic sent from drones is often high volume in the form of video streams. The goal of this thesis is to identify so-called "rogue drones" connected to an LTE network. Rogue drones are flying drones that appear to be regular UEs in the network. Drone identification is a binary classification problem where UEs in a network are classified as either a drone or a regular UE and this thesis proposes machine learning methods that can be used to solve it. Classifications are based on radio measurements and statistics reported by UEs in the network. The data for the work in this thesis is gathered through simulations of a heterogenous LTE network in an urban scenario. The primary idea of this thesis is to use a type of cascading classifier, meaning that classifications are made in a series of stages with increasingly complex models where only a subset of examples are passed forward to subsequent stages. The motivation for such a structure is to minimize the computational requirements at the entity making the classifications while still being complex enough to achieve high accuracy. The models explored in this thesis are two-stage cascading classifiers using decision trees and ensemble learning techniques. It is found that close to 60% of the UEs in the dataset can be classified without errors in the first of the two stages. The rest is forwarded to a more complex model which requires more data from the UEs and can achieve up to 98% accuracy. 

  • 9.
    Ali, Rahman
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Design of Building Blocks in Digital Baseband Transceivers for Body-Coupled Communication2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Advances in communication technologies continue to increase information sharing among the people.~Short-range wireless networking technologies such as Bluetooth or ZigBee, which are mainly used for data transfer over short range, will, however, suffer from network congestion, high power consumption and security issues in the future.

    The body-coupled communication (BCC), a futuristic short-range wireless technology, uses the human body as a transmission medium. In BBC channel, a small electric field is induced onto the human body which enables the propagation of a signal between communication devices that are in the proximity or direct contact with the human body. The direct baseband transmission and simple architecture make BCC an attractive candidate for a future short-range wireless communication technology in particular applications such as body area network.

    The main focus of this thesis is on the design and implementation of digital baseband transmitter and receiver for the body-coupled communication. The physical layer (PHY) implementation of the digital baseband transmitter and receiver is inspired from the IEEE 802.3 Ethernet transmission protocol. The digital design is implemented at RTL level using hardware description language (VHDL). The functionality of the digital baseband transmitter and receiver is demonstrated by developing data transfer application layers.

  • 10.
    Almquist, Mathias
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Almquist, Viktor
    Linköpings universitet, Institutionen för datavetenskap.
    Analysis of 360° Video Viewing Behaviours2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In this thesis we study users' viewing motions when watching 360° videos in order to provide information that can be used to optimize future view-dependent streaming protocols. More specifically, we develop an application that plays a sequence of 360° videos on an Oculus Rift Head Mounted Display and records the orientation and rotation velocity of the headset during playback. The application is used during an extensive user study in order to collect more than 21 hours of viewing data which is then analysed to expose viewing patterns, useful for optimizing 360° streaming protocols. 

  • 11.
    Almquist, Mathias
    et al.
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten.
    Almquist, Viktor
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten.
    Vergara Alonso, Ekhiotz Jon
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Nadjm-Tehrani, Simin
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Communication Energy Overhead of Mobiles Games2015Ingår i: MobiGames '15: Proceedings of the 2nd Workshop on Mobile Gaming, Association for Computing Machinery (ACM), 2015, s. 1-6Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Although a significant proportion of the mobile apps are games there has been little attention paid to their specific characteristics with respect to communication energy. In this paper we select 20 mobile games among the top 100 free Android games, and study their data patterns and communication energy use over a total of 25 hours of playing. The analysis of the energy for communication over 3G networks indicates that there is a wide variation among the games, the largest footprint being 8 times higher than the lowest one. The results also indicates both app-specific and category-specific relations between data pattern and energy use, as well as variations in CPU utilisation.

  • 12.
    Alodeh, Maha
    et al.
    Univ Luxembourg, Luxembourg.
    Spano, Danilo
    Univ Luxembourg, Luxembourg.
    Kalantari, Ashkan
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten. Univ Luxembourg, Luxembourg.
    Tsinos, Christos G.
    Univ Luxembourg, Luxembourg.
    Christopoulos, Dimitrios
    Newtec Satcom, Belgium.
    Chatzinotas, Symeon
    Univ Luxembourg, Luxembourg.
    Ottersten, Bjorn
    Univ Luxembourg, Luxembourg.
    Symbol-Level and Multicast Precoding for Multiuser Multiantenna Downlink: A State-of-the-Art, Classification, and Challenges2018Ingår i: IEEE Communications Surveys and Tutorials, ISSN 1553-877X, E-ISSN 1553-877X, Vol. 20, nr 3, s. 1733-1757Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Precoding has been conventionally considered as an effective means of mitigating or exploiting the interference in the multiantenna downlink channel, where multiple users are simultaneously served with independent information over the same channel resources. The early works in this area were focused on transmitting an individual information stream to each user by constructing weighted linear combinations of symbol blocks (codewords). However, more recent works have moved beyond this traditional view by: 1) transmitting distinct data streams to groups of users and 2) applying precoding on a symbol-persymbol basis. In this context, the current survey presents a unified view and classification of precoding techniques with respect to two main axes: 1) the switching rate of the precoding weights, leading to the classes of block-level and symbol-level precoding and 2) the number of users that each stream is addressed to, hence unicast, multicast, and broadcast precoding. Furthermore, the classified techniques are compared through representative numerical results to demonstrate their relative performance and uncover fundamental insights. Finally, a list of open theoretical problems and practical challenges are presented to inspire further research in this area.(1)

  • 13.
    Al-Salihi, Hayder
    et al.
    The Department of Informatics, King’s College London, UK.
    Van Chien, Trinh
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Le, Tuan Anh
    The Department of Design Engineering and Mathematics, Middlesex University, London, UK.
    Nakhai, Mohammad Reza
    The Department of Informatics, King’s College London, London, UK.
    A Successive Optimization Approach to Pilot Design for Multi-Cell Massive MIMO Systems2018Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, nr 5, s. 1086-1089Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this letter, we introduce a novel pilot designapproach that minimizes the total mean square errors of theminimum mean square error estimators of all base stations (BSs)subject to the transmit power constraints of individual users inthe network, while tackling the pilot contamination in multicellmassive MIMO systems. First, we decompose the originalnon-convex problem into distributed optimization sub-problemsat individual BSs, where each BS can optimize its own pilotsignals given the knowledge of pilot signals from the remainingBSs. We then introduce a successive optimization approach totransform each optimization sub-problem into a linear matrixinequality form, which is convex and can be solved by availableoptimization packages. Simulation results confirm the fast convergenceof the proposed approach and prevails a benchmarkscheme in terms of providing higher accuracy.

  • 14.
    Anchora, Luca
    et al.
    IMT of Lucca.
    Badia, Leonardo
    Università degli Studi di Padova.
    Karipidis, Eleftherios
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Zorzi, Mikele
    Università degli Studi di Padova.
    Capacity Gains due to Orthogonal Spectrum Sharing in Multi-Operator LTE Cellular Networks2012Ingår i: Proceedings of the Ninth International Symposium on Wireless Communication Systems (ISWCS), 2012, s. 286-290Konferensbidrag (Refereegranskat)
    Abstract [en]

    Static spectrum allocation leads to resource wastage and inter-operator spectrum sharing is a possible way to improve spectrum efficiency. In this work, we assume that two cellular network operators agree upon sharing part of their spectrum, which can then be dynamically accessed by either of them in a mutually exclusive way. Our goal is to numerically assess the gain, in terms of cell capacity, due to such orthogonal spectrum sharing. Hence, we propose a centralized algorithm that performs coordinated scheduling, in order to numerically evaluate an upper bound on the achievable sum capacity. The algorithm is centralized and exploits complete information on both networks to perform the optimum allocation. The simulation results illustrate the impact of the multiuser diversity and the asymmetry in the traffic load among the networks on the overall achievable gain.

  • 15.
    Anchora, Luca
    et al.
    IMT of Lucca.
    Badia, Leonardo
    Università degli Studi di Padova.
    Zhang, Haibin
    TNO ICT.
    Fahldieck, Torsten
    Bell Labs, Alcatel-Lucent.
    Zhang, Jianshu
    Ilmenau University of Technology.
    Szydelko, Michal
    Wroclaw Research Centre EIT+ .
    Schubert, Martin
    Fraunhofer Institute for Telecommunications HHI.
    Karipidis, Eleftherios
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Haardt, Martin
    Ilmenau University of Technology.
    Resource Allocation and Management in Multi-Operator Cellular Networks with Shared Physical Resources2012Ingår i: Proceedings of the Ninth International Symposium on Wireless Communication Systems (ISWCS), IEEE , 2012, s. 296-300Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we focus on next-generation cellular networks and discuss physical resources sharing among the operators. This implies cooperative usage of the available radio frequencies and also infrastructure sharing. In particular, we analyze the spectrum sharing gain achievable at different time scales and the main factors impacting on it. Then, we move towards a wider idea of resource sharing and consider a joint spectrum and infrastructure sharing (full sharing). We describe a two-layer resource management architecture that enables operators to reduce costs while still guaranteeing a good service level. The main findings of our investigations are to quantify the effectiveness of resource sharing and open up new perspectives for the operators of next-generation networks.

  • 16.
    Andersson, Martin
    Linköpings universitet, Institutionen för systemteknik, Informationskodning.
    Parametric Prediction Model for Perceived Voice Quality in Secure VoIP2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    More and more sensitive information is communicated digitally and with thatcomes the demand for security and privacy on the services being used. An accurateQoS metric for these services are of interest both for the customer and theservice provider. This thesis has investigated the impact of different parameterson the perceived voice quality for encrypted VoIP using a PESQ score as referencevalue. Based on this investigation a parametric prediction model has been developedwhich outputs a R-value, comparable to that of the widely used E-modelfrom ITU. This thesis can further be seen as a template for how to construct modelsof other equipments or codecs than those evaluated here since they effect theresult but are hard to parametrise.

    The results of the investigation are consistent with previous studies regarding theimpact of packet loss, the impact of jitter is shown to be significant over 40 ms.The results from three different packetizers are presented which illustrates theneed to take such aspects into consideration when constructing a model to predictvoice quality. The model derived from the investigation performs well withno mean error and a standard deviation of the error of a mere 1:45 R-value unitswhen validated in conditions to be expected in GSM networks. When validatedagainst an emulated 3G network the standard deviation is even lower.v

  • 17.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Avgouleas, Ioannis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Fitzgerald, Emma
    Lund University, Sweden.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten. University of Maryland, MD 20742 USA.
    Allocation of Heterogeneous Resources of an IoT Device to Flexible Services2016Ingår i: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 3, nr 5, s. 691-700Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Internet-of-Things (IoT) devices can be equipped with multiple heterogeneous network interfaces. An overwhelmingly large amount of services may demand some or all of these interfaces available resources. Herein, we present a precise mathematical formulation of assigning services to interfaces with heterogeneous resources in one or more rounds. For reasonable instance sizes, the presented formulation produces optimal solutions for this computationally hard problem. We prove the NP-completeness of the problem and develop two algorithms to approximate the optimal solution for big instance sizes. The first algorithm allocates the most demanding service requirements first, considering the average cost of interfaces resources. The second one calculates the demanding resource shares and allocates the most demanding of them first by choosing randomly among equally demanding shares. Finally, we provide simulation results giving insight into services splitting over different interfaces for both cases.

  • 18.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Avgouleas, Ioannis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Flexible allocation of heterogeneous resources to services on an IoT device2015Ingår i: 2015 IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS), Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 99-100Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the Internet of Things (IoT), devices and gateways may be equipped with multiple, heterogeneous network interfaces which should be utilized by a large number of services. In this work, we model the problem of assigning services' resource demands to a device's heterogeneous interfaces and give a Mixed Integer Linear Program (MILP) formulation for it. For meaningful instance sizes the MILP model gives optimal solutions to the presented computationally-hard problem. We provide insightful results discussing the properties of the results on the properties of the derived solutions with respect to the splitting of services to different interfaces.

  • 19.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Efrat, Alon
    University of Arizona, AZ 85721 USA.
    Packer, Eli
    IBM Research Haifa, Israel.
    Polishchuk, Valentin
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Sedov, Leonid
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    BBTM: New life for old ATM2016Ingår i: 2016 IEEE/AIAA 35TH DIGITAL AVIONICS SYSTEMS CONFERENCE (DASC), IEEE , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper investigates algorithmic questions related to the possibility of managing UAV traffic with beacon-based navigation, which we dub BBTM - Beacon-Based Traffic Management. The specific problem addressed is: How to install the minimum number of beacons in a mountainous terrain to ensure connectivity among a given set of UAS terminals on the terrain? BBTM is relevant for low-cost UAVs operating in remote areas not on time-critical missions, and may also be used as a backup system for better-equipped UAS in case the precise positioning or control information is lost, spoofed or jammed. We give algorithms for the beacon tower placement and evaluate their performance both on synthetic and real-world terrain data; the experiments suggest that our solutions can be used to efficiently quantify costs of establishing direct-visibility routing networks for UAS management.

  • 20.
    Aria, Erfan
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Investigation of automated vehicle effects on driver’s behavior and traffic performance2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Advanced Driver Assistance Systems (ADAS) offer the possibility of helping drivers to fulfill their driving tasks. Automated vehicles are capable of communicating with surrounding vehicles (V2V) and infrastructure (V2I) in order to collect and provide essential information about driving environment. Studies have proved that automated vehicles have a potential to decrease traffic congestion on road networks by reducing the time headway, enhancing the traffic capacity and improving the safety margins in car following. Furthermore, vehicle movement and driver’s behavior of conventional vehicles will be affected by the presence of automated vehicles in traffic networks. Despite different encouraging factors, automated driving raises some concerns such as possible loss of situation awareness, overreliance on automation and degrading driving skills in absence of practice. Moreover, coping with complex scenarios, such as merging at ramps and overtaking, in terms of interaction between automated vehicles and conventional vehicles need more research. This thesis work aims to investigate the effects of automated vehicles on driver’s behavior and traffic performance. A broad literature review in the area of driving simulators and psychological studies was performed to examine the automated vehicle effects on driver’s behavior. Findings from the literature survey, which has been served as setup values in the simulation study of the current work, reveal that the conventional vehicles, which are driving close to the platoon of automated vehicles with short time headway, tend to reduce their time headway and spend more time under their critical time headway. Additionally, driving highly automated vehicles is tedious in a long run, reduce situation awareness and can intensify driver drowsiness, exclusively in light traffic. In order to investigate the influences of automated vehicles on traffic performance, a microscopic simulation case study consisting of different penetration rates of automated vehicles (0, 50 and 100 percentages) was conducted in VISSIM software. The scenario network is a three-lane autobahn segment of 2.9 kilometers including an off-ramp, on-ramp and a roundabout with some surrounding urban roads. Outputs of the microscopic simulation in this study reveal that the positive effects of automated vehicles on roads are especially highlighted when the network is crowded (e.g. peak hours). This can definitely count as a constructive point for the future of road networks with higher demands. In details, average density of autobahn segment remarkably decreased by 8.09% during p.m. peak hours in scenario with automated vehicles. Besides, Smoother traffic flow with less queue in the weaving segment was observed. Result of the scenario with 50% share of automated vehicles moreover shows a feasible interaction between conventional vehicles and automated vehicles. Meaningful outputs of this case study, based on the input data from literature review, demonstrate the capability of VISSIM software to simulate the presence of automated vehicles in great extent, not only as an automated vehicle scenario but also a share of them, in traffic network. The validity of the output values nonetheless needs future research work on urban and rural roads with different traffic conditions.

  • 21.
    Arvidsson, Simon
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Ekblom, Tobias
    Linköpings universitet, Institutionen för datavetenskap.
    Marknadsplatsapplikation för Android2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Målet med examensarbetet är att utveckla en marknadsplatsapplikation för Android. Marknadsplatsapplikationen ska tillhandahålla funktioner för att ge användaren förutsättningar att hitta och ladda ner applikationer över Internet ifrån marknadsplatsens serversida. Marknadsplatsapplikationen kommer likt en tunn klient vara helt beroende av innehåll från en serversida. Vid examensarbetets utförande existerade dock ingen serversida då denna ännu inte var färdigutvecklad.

    För att utveckla marknadsplatsapplikationen utan närvaron av en serversida, implementerades en emulerad serversida som utåt sett hade funktionaliteten av en framtida serversida. En mjukvaruarkitektur implementerades bestående av tre lager: användargränsnitt (GUI), kärnfunktionalitet (Core) och webbkommunikation (WebCom). Syftet med arikitekturen var dels att begränsa inverkan av övergången från en emulerad serversida till en riktig serversida, och dels att avgränsa och avlasta användargränsnittet från tunga operationer för att därigenom uppnå god responsivitet.

    Marknadsplatsapplikationen implementerades med all funktionalitet som planerades. Arkitekturen med tydlig separation mellan GUI, Core ochWebCom, förväntas leda till en smidig övergång till en riktig serversida. Även ett tydligt öde för att hämta och skicka data mellan marknadsplatsapplikationen och serversida förväntas underlätta att implementera ny funktionalitet som är beroende av en serversida. Användargränsnittet uppvisar fortfarande brist på responsivitet. Arkitekturen med endast en asynkron klass GuiWorker, som hanterar exekveringen av tunga operationer på bakgrundstrådar, förväntas dock kunna uppnå ett responsivt användargränsnitt.

  • 22.
    Aspnäs, Frida
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Eliminating Right-Turn-on-Red (RTOR) at Key Intersections in a City Core2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The City of Fredericton is the capital of New Brunswick, located in eastern Canada. Rightturn-on-red (RTOR) is a general practice at any traffic intersection in this maritime province. Many collisions between pedestrians and vehicles have been recorded at signalized intersections in the downtown area of the city. Due to the number of collisions, the City of Fredericton was interested in investigating how a restriction against RTOR could affect vehicular traffic. The purpose and goal of this project was to develop a calibrated traffic model of the downtown area of Fredericton that could be used for simulation studies. Two main changes were investigated: 1) a restriction against RTOR for each of eleven key intersections in the downtown area, and 2) a restriction against left-turns at one selected intersection. The traffic simulation model was also used for analyzing how factors such as pedestrian volumes, lane channelization, and turning proportions affect the changes in traffic conditions due to permitting, or prohibiting, right-turn-on-red.

    The traffic simulation model was created in the TSIS/CORSIM software. Several different scenarios were generated for analysis. The results of the simulation show that the traffic conditions in the whole downtown area will be affected when introducing a restriction against RTOR. Certain intersections show a relatively high change while others show no significant change at all. Several different factors were seen to affect the number of RTOR that could be performed at an intersection. One main factor was lane channelization. With a shared lane, the proportion of right-turning vehicles at the intersection was found to highly affect how many RTOR can be performed. Pedestrian volumes prove to be a third factor affecting the number of RTOR at an intersection.

    Overall results demonstrate that there are only a few intersections where it is suitable for the City of Fredericton to implement a restriction against RTOR.

  • 23.
    Avazkonandeh Gharavol, Ebrahim
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Robust Joint Optimization of MIMO Interfering Relay Channels with Imperfect CSI2011Ingår i: 2001 4th IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP), Piscataway, NJ, USA: IEEE , 2011, , s. 5s. 209-212Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we deal with the problem of the joint optimization of the precoders, equalizers and relay beamformer of a multiple-input multiple-output interfering relay channel. This network can be regarded az a generalized model for both one-way and two-way relay channels with/without direct interfering links. Unlike the conventional design procedures, we assume that the Channel State Information (CSI) is not known perfectly. The imperfect CSI is described using the norm bounded error framework. We use a system-wide Sum Mean Square Error (SMSE) based problem formulation which is constrained using the transmit power of the terminals and the relay node. The problem at hand, from a worst-case design perspective, is a multilinear, and hence, a nonconvex problem which is also semiinfinite in its constraints. We use a generalized version of the Peterson’s lemma to handle the semi-infiniteness and reduce the original problem to a single Linear Matrix Inequality (LMI). However, this LMI is not convex, and to resolve this issue we propose an iterative algorithm based on the alternating convex search methodology to solve the aforementioned problem. Finally simulation results, i.e., the convergence of the proposed algorithm and the SMSE properties, are included to asses the performance of the proposed algorithm.

  • 24.
    Avazkonandeh Gharavol, Ebrahim
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Robust Joint Optimization of Non-regenerative MIMO Relay Channels with Imperfect CSI2011Ingår i: Conference Record of the Forty Fifth Asilomar Conference on Signals, Systems and Computers (ASILOMAR), 2011, IEEE Computer Society, 2011, s. 1589-1593Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we deal with the problem of joint optimization of the source precoder, the relay beamformer and the destination equalizer in a nonregenerative relay network with only a partial knowledge of the Channel State Information (CSI).

    We model the partial CSI using a deterministic norm bounded error model, and we use a system-wide mean square error performance measure which is constrained based on the transmit power regulations for both source and relay nodes.

    Most conventional designs employ the average performance optimization, however, we solve this problem from a worst-case design perspective.

    The original problem formulation is a semi-infinite trilinear optimization problem which is not convex.

    To solve this problem we extend the existing theories to deal with the constraints which are semi-infinite in different independent complex matrix variables.

    We show that the equivalent approximate problem is a set of linear matrix inequalities, that can be solved iteratively.

    Finally simulation results assess the performance of the proposed scheme.

  • 25.
    Avazkonandeh Gharavol, Ebrahim
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    The Sign-Definiteness Lemma and Its Applications to Robust Transceiver Optimization for Multiuser MIMO Systems2013Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 61, nr 2, s. 238-252Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We formally generalize the sign-definiteness lemma to the case of complex-valued matrices and multiple norm-bounded uncertainties. This lemma has found many applications in the study of the stability of control systems, and in the design and optimization of robust transceivers in communications. We then present three different novel applications of this lemma in the area of multi-user multiple-input multiple-output (MIMO) robust transceiver optimization. Specifically, the scenarios of interest are: (i) robust linear beamforming in an interfering adhoc network, (ii) robust design of a general relay network, including the two-way relay channel as a special case, and (iii) a half-duplex one-way relay system with multiple relays. For these networks, we formulate the design problems of minimizing the (sum) MSE of the symbol detection subject to different average power budget constraints. We show that these design problems are non-convex (with bilinear or trilinear constraints) and semiinfinite in multiple independent uncertainty matrix-valued variables. We propose a two-stage solution where in the first step the semi-infinite constraints are converted to linear matrix inequalities using the generalized signdefiniteness lemma, and in the second step, we use an iterative algorithm based on alternating convex search (ACS). Via simulations we evaluate the performance of the proposed scheme.

  • 26.
    Avgouleas, Ioannis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    IoT Networking Resource Allocation and Cooperation2017Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The Internet of Things (IoT) promises that "anything that can be connected, will be connected". It comprises of Information and Communication Technologies that interconnect billions of physical and visual things with some "basic" intelligence. The emerging IoT services will be able to react with minimal human intervention and further contribute to the big data era that requires real-time, ultrareliable, ubiquitous, scalable, and heterogeneous operation.

    This thesis is the result of our investigations on problems dealing with the evolution of such technologies. First, we explore the potential of using relay i.e., intermediate, nodes that assist users to transmit their packets in a a cellular network. Paper I provides insights into how adapting the cooperation of the relay's receiver and transmitter optimizes the network-wide throughput while the relay's queue stability is guaranteed.

    The next part of the thesis copes with the resource allocation of services on IoT devices equipped with multiple network interfaces. The resources are heterogeneous and can be split among dierent interfaces. Additionally, they are not interchangeable. In paper II, we develop optimization models for this resource allocation problem, prove the complexity of the models, and derive results that give intuition into the problems. Moreover, we propose algorithms that approximate the optimal solution and show under which circumstances this is possible.

    Finally, in paper III, we present a resource allocation problem specically for smart cities services. In comparison to the previous problem denition, resources are of one type but the IoT network device can oer capacities that vary over time. Furthermore, services have a tolerance regarding their preferred scheduling, namely, their allocation over time. We parametrize each service with a pricing function to indicate its tolerance to be served at the beginning of the scheduling window. We prove that the problem is computationally hard and provide numerical results to gain insight into how different pricing weight functions impact the allocations' distribution within the scheduling window.

    Delarbeten
    1. Probabilistic Cooperation of a Full-Duplex Relay in Random Access Networks
    Öppna denna publikation i ny flik eller fönster >>Probabilistic Cooperation of a Full-Duplex Relay in Random Access Networks
    2017 (Engelska)Ingår i: IEEE Access, E-ISSN 2169-3536, Vol. 5, s. 7394-7404Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In this paper, we analyze the probabilistic cooperation of a full-duplex relay in a multiuser random-access network. The relay is equipped with on/off modes for the receiver and the transmitter independently. These modes are modeled as probabilities by which the receiver and the transmitter are activated. We provide analytical expressions for the performance of the relay queue, such as arrival and service rates, stability conditions, and the average queue size. We optimize the relays operation setup to maximize the network-wide throughput while, simultaneously, we keep the relays queue stable and lower the relays receptions and transmissions. Furthermore, we study the effect of the SINR threshold and the self-interference coefficient on the per-user and network-wide throughput. For low SINR threshold, we show under which circumstances it is beneficial to switch off the relay completely, or switch off the relays receiver only.

    Ort, förlag, år, upplaga, sidor
    IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2017
    Nyckelord
    Cooperative communication; relays; relay networks; multiaccess communication; multiple access interference; internet of things (IoT); internet; wireless sensor networks (WSNs); body sensor networks (BSNs)
    Nationell ämneskategori
    Datorsystem
    Identifikatorer
    urn:nbn:se:liu:diva-139423 (URN)10.1109/ACCESS.2016.2642540 (DOI)000403140800053 ()
    Anmärkning

    Funding Agencies|European Union [609094, 612361]

    Tillgänglig från: 2017-08-07 Skapad: 2017-08-07 Senast uppdaterad: 2019-05-09
    2. Allocation of Heterogeneous Resources of an IoT Device to Flexible Services
    Öppna denna publikation i ny flik eller fönster >>Allocation of Heterogeneous Resources of an IoT Device to Flexible Services
    Visa övriga...
    2016 (Engelska)Ingår i: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 3, nr 5, s. 691-700Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Internet-of-Things (IoT) devices can be equipped with multiple heterogeneous network interfaces. An overwhelmingly large amount of services may demand some or all of these interfaces available resources. Herein, we present a precise mathematical formulation of assigning services to interfaces with heterogeneous resources in one or more rounds. For reasonable instance sizes, the presented formulation produces optimal solutions for this computationally hard problem. We prove the NP-completeness of the problem and develop two algorithms to approximate the optimal solution for big instance sizes. The first algorithm allocates the most demanding service requirements first, considering the average cost of interfaces resources. The second one calculates the demanding resource shares and allocates the most demanding of them first by choosing randomly among equally demanding shares. Finally, we provide simulation results giving insight into services splitting over different interfaces for both cases.

    Ort, förlag, år, upplaga, sidor
    Institute of Electrical and Electronics Engineers (IEEE), 2016
    Nyckelord
    Internet of Things (IoT); mixed integer linear programming; network interfaces; optimization; resource management; scheduling algorithms
    Nationell ämneskategori
    Kommunikationssystem
    Identifikatorer
    urn:nbn:se:liu:diva-135000 (URN)10.1109/JIOT.2016.2535163 (DOI)000393047800006 ()
    Anmärkning

    Funding Agencies|Excellence Center at Linkoping-Lund in Information Technology; European Union [324515, 612316, 609094]

    Tillgänglig från: 2017-03-06 Skapad: 2017-03-06 Senast uppdaterad: 2019-05-09Bibliografiskt granskad
  • 27.
    Avgouleas, Ioannis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Utilizing multiple full-duplex relays in wireless systems with multiple packet reception2014Ingår i: 2014 IEEE 19th International Workshop on Computer Aided Modeling and Design of Communication Links and Networks (CAMAD), IEEE, 2014, s. 193-197Konferensbidrag (Refereegranskat)
    Abstract [en]

    Relay nodes with physical layer cooperation have been used extensively to assist users' transmissions in wireless networks. This network level cooperation has been lately been gaining popularity and analytical expressions of the performance of a network with up to two relay nodes exist in recent literature. In this work, we give simulation results outlining the potential network level benefits of using multiple full-duplex relay nodes. We examine configurations where multiple full-duplex transceivers offer consistent improvement and provide guidelines on using them different network conditions.

  • 28.
    Avgouleas, Ioannis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Scheduling Services on an IoT Device Under Time-Weighted Pricing2017Ingår i: Conference Proceedings IEEE 28th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC): Workshop on "Communications for Networked Smart Cities", IEEE conference proceedings, 2017, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    The emerging vision of smart cities necessitates the use of Internet of Things (IoT) network devices to implement sustainable solutions that will improve the operations of urban areas. A massive amount of smart cities services may demand allocation of computational resources, such as processing power or storage, that IoT devices offer. Within this context, we present an IoT network device comprising interfaces with one specific computational resource available. The efficient utilization of available IoT resources would improve the Quality of Service (QoS) of the IoT network that serves the smart city. All resource allocations must be completed within a given scheduling window and every service is parametrized by a pricing weight function to indicate its tolerance to be served at the beginning of the scheduling window. We propose a mathematical optimization formulation to minimize the total cost of allocating all demands within the scheduling window considering the tolerance level of each service at the same time. Moreover, we prove that the problem is computationally hard and we provide numerical results to gain insight into the impact of different pricing weight functions on the allocations’ distribution within the scheduling window.

  • 29.
    Axell, Erik
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Spectrum Sensing Algorithms Based on Second-Order Statistics2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Cognitive radio is a new concept of reusing spectrum in an opportunistic manner. Cognitive radio is motivated by recent measurements of spectrum utilization, showing unused resources in frequency, time and space. Introducing cognitive radios in a primary network inevitably creates increased interference to the primary users. Secondary users must sense the spectrum and detect primary users' signals at very low SNR, to avoid causing too much interference.This dissertation studies this detection problem, known as spectrum sensing.

    The fundamental problem of spectrum sensing is to discriminate an observation that contains only noise from an observation that contains a very weak signal embedded in noise. In this work, detectors are derived that exploit known properties of the second-order moments of the signal. In particular, known structures of the signal covariance are exploited to circumvent the problem of unknown parameters, such as noise and signal powers or channel coefficients.

    The dissertation is comprised of six papers, all in different ways related to spectrum sensing based on second-order statistics. In the first paper, we considerspectrum sensing of orthogonal frequency-division multiplexed (OFDM) signals in an additive white Gaussian noise channel. For the case of completely known noise and signal powers, we set up a vector-matrix model for an OFDM signal with a cyclic prefix and derive the optimal Neyman-Pearson detector from first principles. For the case of completely unknown noise and signal powers, we derive a generalized likelihood ratio test (GLRT) based on empirical second-order statistics of the received data. The proposed GLRT detector exploits the non-stationary correlation structure of the OFDM signal and does not require any knowledge of the noise or signal powers.

    In the second paper, we create a unified framework for spectrum sensing of signals which have covariance matrices with known eigenvalue multiplicities. We derive the GLRT for this problem, with arbitrary eigenvalue multiplicities under both hypotheses. We also show a number of applications to spectrum sensing for cognitive radio.

    The general result of the second paper is used as a building block, in the third and fourth papers, for spectrum sensing of second-order cyclostationary signals received at multiple antennas and orthogonal space-time block coded (OSTBC) signals respectively. The proposed detector of the third paper exploits both the spatial and the temporal correlation of the received signal, from knowledge of the fundamental period of the cyclostationary signal and the eigenvalue multiplicities of the temporal covariance matrix.

    In the fourth paper, we consider spectrum sensing of signals encoded with an OSTBC. We show how knowledge of the eigenvalue multiplicities of the covariance matrix are inherent owing to the OSTBC, and propose an algorithm that exploits that knowledge for detection. We also derive theoretical bounds on the performance of the proposed detector. In addition, we show that the proposed detector is robust to a carrier frequency offset, and propose another detector that deals with timing synchronization using the detector for the synchronized case as a building block.

    A slightly different approach to covariance matrix estmation is taken in the fifth paper. We consider spectrum sensing of Gaussian signals with structured covariance matrices, and propose to estimate the unknown parameters of the covariance matrices using covariance matching estimation techniques (COMET). We also derive the optimal detector based on a Gaussian approximation of the sample covariance matrix, and show that this is closely connected to COMET.

    The last paper deals with the problem of discriminating samples that containonly noise from samples that contain a signal embedded in noise, when the variance of the noise is unknown. We derive the optimal soft decision detector using a Bayesian approach. The complexity of this optimal detector grows exponentially with the number of observations and as a remedy, we propose a number of approximations to it. The problem under study is a fundamental one andit has applications in signal denoising, anomaly detection, and spectrum sensing for cognitive radio.

    Delarbeten
    1. Optimal and Sub-Optimal Spectrum Sensing of OFDM Signals in Known and Unknown Noise Variance
    Öppna denna publikation i ny flik eller fönster >>Optimal and Sub-Optimal Spectrum Sensing of OFDM Signals in Known and Unknown Noise Variance
    2011 (Engelska)Ingår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 29, nr 2, s. 290-304Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    We consider spectrum sensing of OFDM signals in an AWGN channel. For  the case of completely known noise and signal powers, we set up  a vector-matrix model for an OFDM signal with a cyclic prefix and  derive the optimal Neyman-Pearson detector from first  principles. The optimal detector exploits the inherent correlation  of the OFDM signal incurred by the repetition of data in the cyclic  prefix, using knowledge of the length of the cyclic prefix and the  length of the OFDM symbol. We compare the optimal detector to the energy  detector numerically. We show that the energy detector is  near-optimal (within 1 dB SNR) when the noise variance is  known. Thus, when the noise power is known, no substantial gain can  be achieved by using any other detector than the energy detector.

    For the case of completely unknown noise and signal powers, we  derive a generalized likelihood ratio test (GLRT) based onempirical second-order statistics of  the received data. The proposed GLRT detector exploits the  non-stationary correlation structure of the OFDM signal and does not  require any knowledge of the noise power or the signal power. The  GLRT detector is compared to state-of-the-art OFDM signal detectors,  and shown to improve the detection performance with 5 dB SNR in  relevant cases.

    Ort, förlag, år, upplaga, sidor
    Institute of Electrical and Electronics Engineers (IEEE), 2011
    Nyckelord
    spectrum sensing, signal detection, OFDM, cyclic prefix, subspace detection, second-order statistics
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-58515 (URN)10.1109/JSAC.2011.110203 (DOI)000286676500003 ()
    Anmärkning

    ©2011 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Erik Axell and Erik G. Larsson, Optimal and Sub-Optimal Spectrum Sensing of OFDM Signals in Known and Unknown Noise Variance, 2011, IEEE Journal on Selected Areas in Communications, (29), 2, 290-304. http://dx.doi.org/10.1109/JSAC.2011.110203

    The previous status of this article was Manuskript.

    Tillgänglig från: 2010-08-12 Skapad: 2010-08-12 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
    2. A Unified Framework for GLRT-Based Spectrum Sensing of Signals with Covariance Matrices with Known Eigenvalue Multiplicities
    Öppna denna publikation i ny flik eller fönster >>A Unified Framework for GLRT-Based Spectrum Sensing of Signals with Covariance Matrices with Known Eigenvalue Multiplicities
    2011 (Engelska)Ingår i: Proceedings of the IEEE International Conference on Acoustics, Speech and SignalProcessing (ICASSP), IEEE conference proceedings, 2011, s. 2956-2959Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    In this paper, we create a unified framework for spectrum sensing of signals which have covariance matrices with known eigenvalue multiplicities. We derive the generalized likelihood-ratio test (GLRT) for this problem, with arbitrary eigenvalue multiplicities under both hypotheses. We also show a number of applications to spectrum sensing for cognitive radio and show that the GLRT for these applications, of which some are already known, are special cases of the general result.

    Ort, förlag, år, upplaga, sidor
    IEEE conference proceedings, 2011
    Serie
    IEEE International Conference on Acoustics, Speech and SignalProcessing, ISSN 1520-6149
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-64320 (URN)10.1109/ICASSP.2011.5946277 (DOI)000296062403092 ()
    Anmärkning
    ©2011 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Erik Axell and Erik G. Larsson, A Unified Framework for GLRT-Based Spectrum Sensing of Signals with Covariance Matrices with Known Eigenvalue Multiplicities, 2011, Proceedings of the IEEE International Conference on Acoustics, Speech and SignalProcessing (ICASSP), 2956-2959. http://dx.doi.org/10.1109/ICASSP.2011.5946277 Tillgänglig från: 2011-01-19 Skapad: 2011-01-19 Senast uppdaterad: 2016-08-31
    3. Multiantenna Spectrum Sensing of a Second-Order Cyclostationary Signal
    Öppna denna publikation i ny flik eller fönster >>Multiantenna Spectrum Sensing of a Second-Order Cyclostationary Signal
    2011 (Engelska)Ingår i: Proceedings of the 4th IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP'11), 2011, s. 329-332Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    We consider spectrum sensing of a second-order cyclostationary signal receivedat multiple antennas. The proposed detector exploits both the spatial andthe temporal correlation of the received signal, from knowledge of thefundamental period of the cyclostationary signal and the eigenvaluemultiplicities of the temporal covariance matrix. All other parameters, suchas the channel gains or the noise power, are assumed to be unknown. The proposeddetector is shown numerically to outperform state-of-the-art detectors forspectrum sensing of anOFDM signal, both when using a single antenna and with multiple antennas.

    Nyckelord
    spectrum sensing, multiple antennas, cyclostationarity, GLRT
    Nationell ämneskategori
    Kommunikationssystem Signalbehandling
    Identifikatorer
    urn:nbn:se:liu:diva-70858 (URN)10.1109/CAMSAP.2011.6136017 (DOI)978-1-4577-2103-8 (ISBN)
    Konferens
    4th IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP), December 13-16 2011, San Juan, Puerto Rico (USA)
    Forskningsfinansiär
    eLLIIT - The Linköping‐Lund Initiative on IT and Mobile CommunicationsVetenskapsrådet
    Tillgänglig från: 2011-09-20 Skapad: 2011-09-20 Senast uppdaterad: 2016-08-31Bibliografiskt granskad
    4. Spectrum Sensing of Orthogonal Space-Time Block Coded Signals with Multiple Receive Antennas
    Öppna denna publikation i ny flik eller fönster >>Spectrum Sensing of Orthogonal Space-Time Block Coded Signals with Multiple Receive Antennas
    2010 (Engelska)Ingår i: Proceedings of the IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Institute of Electrical and Electronics Engineers (IEEE), 2010, s. 3110-3113Konferensbidrag, Publicerat paper (Övrigt vetenskapligt)
    Abstract [en]

    We consider detection of signals encoded with orthogonal space-time block codes (OSTBC), using multiple receive antennas. Such signals contain redundancy and they have a specific structure, that can be exploited for detection. We derive the optimal detector, in the Neyman-Pearson sense, when all parameters are known. We also consider unknown noise variance, signal variance and channel coefficients. We propose a number of GLRT based detectors for the different cases, that exploit the redundancy structure of the OSTBC signal. We also propose an eigenvalue-based detector for the case when all parameters are unknown. The proposed detectors are compared to the energy detector. We show that when only the noise variance is known, there is no gain in exploiting the structure of the OSTBC. However, when the noise variance is unknown there can be a significant gain.

    Ort, förlag, år, upplaga, sidor
    Institute of Electrical and Electronics Engineers (IEEE), 2010
    Serie
    Acoustics Speech and Signal Processing (ICASSP), ISSN 1520-6149, E-ISSN 2379-190X
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-51745 (URN)10.1109/ICASSP.2010.5496088 (DOI)000287096003014 ()9781424442959 (ISBN)9781424442966 (ISBN)
    Konferens
    IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP), 2010, 14-19 March, Dallas, Texas, U.S.A.
    Anmärkning

    ©2010 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.: Erik Axell and Erik G. Larsson, Spectrum Sensing of Orthogonal Space-Time Block Coded Signals with Multiple Receive Antennas, 2010, Proceedings of the 35th IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP'10).

    The previous status of this articel was Manuscript.

    Tillgänglig från: 2009-11-17 Skapad: 2009-11-17 Senast uppdaterad: 2018-02-02Bibliografiskt granskad
    5. Spectrum Sensing of Signals with Structured Covariance Matrices Using Covariance Matching Estimation Techniques
    Öppna denna publikation i ny flik eller fönster >>Spectrum Sensing of Signals with Structured Covariance Matrices Using Covariance Matching Estimation Techniques
    2011 (Engelska)Ingår i: Proceedings of the IEEE Global Communications Conference (GLOBECOM), 2011, s. 1-5Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    In this work, we consider spectrum sensing of Gaussian signals with structured covariance matrices. We show that the optimal detector based on the probability distribution of the sample covariance matrix is equivalent to the optimal detector based on the raw data, if the covariance matrices are known. However, the covariance matrices are unknown in general. Therefore, we propose to estimate the unknown parameters using covariance matching estimation techniques (COMET). We also derive the optimal detector based on a Gaussian approximation of the sample covariance matrix, and show that this is closely connected to COMET.

    Nyckelord
    spectrum sensing, sample covariance, COMET
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-69639 (URN)10.1109/GLOCOM.2011.6133506 (DOI)978-1-4244-9267-1 (ISBN)978-1-4244-9266-4 (ISBN)
    Konferens
    IEEE Global Communications Conference (GLOBECOM), 3-7 December, Anaheim, California, USA
    Tillgänglig från: 2011-07-08 Skapad: 2011-07-08 Senast uppdaterad: 2016-08-31
    6. A Bayesian Approach to Spectrum Sensing, Denoising and Anomaly Detection
    Öppna denna publikation i ny flik eller fönster >>A Bayesian Approach to Spectrum Sensing, Denoising and Anomaly Detection
    2009 (Engelska)Ingår i: Proceedings of the 34th IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP'09), 2009, s. 2333-2336Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    This paper deals with the problem of discriminating samples that contain only noise from samples that contain a signal embedded in noise. The focus is on the case when the variance of the noise is unknown. We derive the optimal soft decision detector using a Bayesian approach. The complexity of this optimal detector grows exponentially with the number of observations and as a remedy, we propose a number of approximations to it. The problem under study is a fundamental one and it has applications in signal denoising, anomaly detection, and spectrum sensing for cognitive radio. We illustrate the results in the context of the latter.

    Serie
    Acoustics, Speech and Signal Processing, ISSN 1520-6149 ; 2009
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-25592 (URN)10.1109/ICASSP.2009.4960088 (DOI)978-1-4244-2354-5 (ISBN)978-1-4244-2353-8 (ISBN)
    Konferens
    34th IEEE international conference on acoustics, speech and signal processing,19-24 April, Taipei, Taiwan
    Anmärkning
    ©2009 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Erik Axell and Erik G. Larsson, A Bayesian Approach to Spectrum Sensing, Denoising and Anomaly Detection, 2009, Proceedings of the 34th IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP'09), 2333-2336. http://dx.doi.org/10.1109/ICASSP.2009.4960088Tillgänglig från: 2009-10-08 Skapad: 2009-10-08 Senast uppdaterad: 2016-08-31Bibliografiskt granskad
  • 30.
    Axell, Erik
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Multiantenna Spectrum Sensing of a Second-Order Cyclostationary Signal2011Ingår i: Proceedings of the 4th IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP'11), 2011, s. 329-332Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider spectrum sensing of a second-order cyclostationary signal receivedat multiple antennas. The proposed detector exploits both the spatial andthe temporal correlation of the received signal, from knowledge of thefundamental period of the cyclostationary signal and the eigenvaluemultiplicities of the temporal covariance matrix. All other parameters, suchas the channel gains or the noise power, are assumed to be unknown. The proposeddetector is shown numerically to outperform state-of-the-art detectors forspectrum sensing of anOFDM signal, both when using a single antenna and with multiple antennas.

  • 31.
    Babu, Bibin
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Connected Me: Hardware for high speed BCC2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Body coupled communication (BCC) is a hot topic in personal networking domain. Many works arepublished suggesting different architectures for BCC since its inception in 1995 by Zimmerman. The number ofelectronic gadgets used by a single person increases as time pass by. Its a tedious job to transfer data betweenthen from a user point of view. Many of these gadgets can share their resources and save power and money.The existing wired or wireless networks does not meet the requirements for this network like scalable data rate,security etc. So here comes the novel idea of using human body as communication medium. The aim of thisthesis is to realize a hardware for BCC based on wide band signaling as part of a big project.The human body consists of 70% of water. This property makes the human body a fairly good conductor.By exploiting this basic property makes the BCC possible. A capacitance is formed if we place a metal platenear to the human body with the skin as a dielectric. This capacitance forms the interface between the humanbody and the analog front-end of the BCC transceiver. Any other metal structures near to the human body canattenuate the signal.A first-order communication link is established in software by the human body model and the transceiver inthe loop along with noise and interference. This communication link is used to verify the human body modeland the base band model done as part of the same big project. Based on the results a hardware prototype isimplemented. Measurements are taken in different scenarios using the hardware setup. The trade-off betweendesign parameters are discussed based on the results. At the end, it suggests a road map to take the projectfurther.

  • 32.
    Berggren, Magnus
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Simon, Daniel
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Nilsson, D
    Acreo Swedish ICT, Box 787, SE-601 17, Norrköping, Sweden..
    Dyreklev, P
    Acreo Swedish ICT, Box 787, SE-601 17, Norrköping, Sweden..
    Norberg, P
    Acreo Swedish ICT, Box 787, SE-601 17, Norrköping, Sweden..
    Nordlinder, S
    Acreo Swedish ICT, Box 787, SE-601 17, Norrköping, Sweden..
    Ersman, PA
    Acreo Swedish ICT, Box 787, SE-601 17, Norrköping, Sweden..
    Gustafsson, G
    Acreo Swedish ICT, Box 787, SE-601 17, Norrköping, Sweden..
    Wikner, Jacob
    Linköpings universitet, Institutionen för systemteknik, Elektroniska Kretsar och System. Linköpings universitet, Tekniska fakulteten.
    Hederén, J
    DU Radio, Ericsson AB, SE-583 30, Linköping, Sweden..
    Hentzell, H
    Swedish ICT Research, Box 1151, SE-164 26, Kista, Sweden..
    Browsing the Real World using Organic Electronics, Si-Chips, and a Human Touch.2016Ingår i: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 28, nr 10, s. 1911-1916Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Organic electronics have been developed according to an orthodox doctrine advocating "all-printed, "all-organic and "ultra-low-cost primarily targeting various e-paper applications. In order to harvest from the great opportunities afforded with organic electronics potentially operating as communication and sensor outposts within existing and future complex communication infrastructures, high-quality computing and communication protocols must be integrated with the organic electronics. Here, we debate and scrutinize the twinning of the signal-processing capability of traditional integrated silicon chips with organic electronics and sensors, and to use our body as a natural local network with our bare hand as the browser of the physical world. The resulting platform provides a body network, i.e., a personalized web, composed of e-label sensors, bioelectronics, and mobile devices that together make it possible to monitor and record both our ambience and health-status parameters, supported by the ubiquitous mobile network and the resources of the "cloud".

  • 33.
    Berglund, Joel
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Extended LTE Coverage For Indoor Machine Type Communication2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The interest of Machine Type Communication (MTC) is increasing and is expected to play an important role in the future network society. In the process of increasing the number of connected devices, the coverage plays an important role. This thesis work aims to study the possibility of supporting coverage limited MTC-devices within LTE by extending the LTE coverage.

    It shows that coverage increase by means of repetition is a good candidate, which allows for a significant increase without hardware upgrades at a low cost in terms of radio resources. For inter-site distances up to 2500 m, the proposed repetition scheme with an increase of 20 dB allows for almost complete coverage where today’s LTE have significant lack of coverage. It also shows that even though the increased coverage implies higher resource usage, the limitation is not in the number of users supported, but rather the coverage at longer inter-site distances.

  • 34.
    berglund, Mattias
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem.
    Bluetooth LE Mesh Network in an Industrial Environment2018Självständigt arbete på grundnivå (högskoleexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    With wireless signals, it is possible to send all kind of data through a communication system. Many companies today having problems implementing wireless communication system because of big areas and many obstacles that blocks the wireless signals. Recent releases of mesh network standards that has the main objective to provide a network over a large area. Toyota Material Handling Europe (TMHE) that develops and produce trucks is one company that wants to use this new network topology to get to the next level of communication.

    TMHE is developing a new communication system between their trucks and the goal is to be independent of Wi-Fi and fixed structures in an industry. The aim is to establish communication through Bluetooth and create a mesh network between the trucks at a site. This kind of communication can create many new possibilities for new features, which can make the daily work easier.

    The problem with obstacles and interferences is still a problem and TMHE created a thesis to research Bluetooth mesh networks to see if this kind of implementation is suitable for the environments that exists in an industry. This thesis research the architecture of a Bluetooth mesh network and different setups of a network and tests how it stands in an industry with many different surrounding.

  • 35.
    Bergström, Andreas
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten. Ericsson Research.
    Hendeby, Gustaf
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Gunnarsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten. Ericsson Research.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    TOA Estimation Improvements in Multipath Environments by Measurement Error Models2017Ingår i: Proceedings of the 2017 IEEE 28th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 1-8Konferensbidrag (Refereegranskat)
    Abstract [en]

    Many positioning systems rely on accuratetime of arrival measurements. In this paper, we addressnot only the accuracy but also the relevance of Time ofArrival (TOA) measurement error modeling. We discusshow better knowledge of these errors can improve relativedistance estimation, and compare the impact of differentlydetailed measurement error information. These models arecompared in simulations based on models derived froman Ultra Wideband (UWB) measurement campaign. Theconclusion is that significant improvements can be madewithout providing detailed received signal information butwith a generic and relevant measurement error model.

  • 36.
    Bertilsson, Erik
    Linköpings universitet, Institutionen för systemteknik, Datorteknik.
    A Scalable Architecture for Massive MIMO Base Stations Using Distributed Processing2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Massive MIMO is an emerging technology for future wireless systems that has received much attention from both academia and industry recently. The most prominent feature of Massive MIMO is that the base station is equiped with a large number of antennas. It is therefore important to create scalable architectures to enable simple deployment in different configurations.

    In this thesis, a distributed architecture for performing the baseband processing in a massive OFDM MU-MIMO system is proposed and analyzed. The proposed architecture is based on connecting several identical nodes in a K-ary tree. It is shown that, depending on the chosen algorithms, all or most computations can be performed in a distrbuted manner. Also, the computational load of each node does not depend on the number of nodes in the tree (except for some timing issues) which implies simple scalability of the system.

    It is shown that it should be enough that each node contains one or two complex multipliers and a few complex adders running at a couple of hundres MHz to support specifications similar to LTE. Additionally the nodes must communicate with each other over links with data rates in the order of some Gbps.

    Finally, a VHDL implementation of the system is proposed. The implementation is parameterized such that a system can be generated from a given specification.

  • 37.
    Bertilsson, Erik
    et al.
    Linköpings universitet, Institutionen för systemteknik, Datorteknik. Linköpings universitet, Tekniska fakulteten.
    Gustafsson, Oscar
    Linköpings universitet, Institutionen för systemteknik, Datorteknik. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    A Modular Base Station Architecture for Massive MIMO with Antenna and User Scalability per Processing Node2018Ingår i: 2018 CONFERENCE RECORD OF 52ND ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS, AND COMPUTERS, IEEE , 2018, s. 1649-1653Konferensbidrag (Refereegranskat)
    Abstract [en]

    Massive MIMO is key technology for the upcoming fifth generation cellular networks (5G), promising high spectral efficiency, low power consumption, and the use of cheap hardware to reduce costs. Previous work has shown how to create a distributed processing architecture, where each node in a network performs the computations related to one or more antennas. The required total number of antennas, M, at the base station depends on the number of simultaneously operating terminals, K. In this work, a flexible node architecture is presented, where the number of terminals can he traded for additional antennas at the same node. This means that the same node can be used with a wide range of system configurations. The computational complexity, along with the order in which to compute incoming and outgoing symbols is explored.

  • 38.
    Bertilsson, Erik
    et al.
    Linköpings universitet, Institutionen för systemteknik, Datorteknik. Linköpings universitet, Tekniska fakulteten.
    Gustafsson, Oscar
    Linköpings universitet, Institutionen för systemteknik, Datorteknik. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    A Scalable Architecture for Massive MIMO Base Stations Using Distributed Processing2016Ingår i: 2016 50TH ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS AND COMPUTERS, Washington: IEEE COMPUTER SOC , 2016, s. 864-868Konferensbidrag (Refereegranskat)
    Abstract [en]

    Massive MIMO-systems have received considerable attention in recent years as an enabler in future wireless communication systems. As the idea is based on having a large number of antennas at the base station it is important to have both a scalable and distributed realization of such a system to ease deployment. Most work so far have focused on the theoretical aspects although a few demonstrators have been reported. In this work, we propose a base station architecture based on connecting the processing nodes in a K-ary tree, allowing simple scalability. Furthermore, it is shown that most of the processing can be performed locally in each node. Further analysis of the node processing shows that it should be enough that each node contains one or two complex multipliers and a few complex adders/subtracters operating at some hundred MHz. It is also shown that a communication link of some Gbps is required between the nodes, and, hence, it is fully feasible to have one or a few links between the nodes to cope with the communication requirements.

  • 39.
    Bertilsson, Erik
    et al.
    Linköpings universitet, Institutionen för systemteknik, Datorteknik. Linköpings universitet, Tekniska fakulteten.
    Gustafsson, Oscar
    Linköpings universitet, Institutionen för systemteknik, Datorteknik. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Computation Limited Matrix Inversion Using Neumann Series Expansion for Massive MIMO2017Ingår i: 2017 FIFTY-FIRST ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS, AND COMPUTERS, 2017, s. 466-469Konferensbidrag (Refereegranskat)
    Abstract [en]

    Neumann series expansion is a method for performing matrix inversion that has received a lot of interest in the context of massive MIMO systems. However, the computational complexity of the Neumann methods is higher than for the lowest complexity exact matrix inversion algorithms, such as LDL, when the number of terms in the series is three or more. In this paper, the Neumann series expansion is analyzed from a computational perspective for cases when the complexity of performing exact matrix inversion is too high. By partially computing the third term of the Neumann series, the computational complexity can be reduced. Three different preconditioning matrices are considered. Simulation results show that when limiting the total number of operations performed, the BER performance of the tree different preconditioning matrices is the same.

  • 40.
    Bhatti, Ayesha
    Linköpings universitet, Institutionen för datavetenskap.
    Snippet Generation for Provenance Workflows2011Självständigt arbete på avancerad nivå (masterexamen), 30 poäng / 45 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Scientists often need to know how data was derived in addition to what it is. The detailed tracking of data transformation or provenance allows result reproducibility, knowledge reuse and data analysis. Scientific workflows are increasingly being used to represent provenance as they are capable of recording complicated processes at various levels of detail. In context of knowledge reuse and sharing; search technology is of paramount importance specially considering the huge and ever increasing amount of scientific data. It is computationally hard to produce a single exact answer to the user's query due to sheer volume and complicated structure of provenance.  One solution to this difficult problem is to produce a list of candidate matches and let user select the most relevant result. Here search result presentation becomes very important as the user is required to make the final decision by looking at the workflows in the result list. Presentation of these candidate matches needs to be brief, precise, clear and revealing. This is a challenging task in case of workflows as they contain textual content as well as graphical structure. Current workflow search engines such as Yahoo Pipes! or myExperiment ignore the actual workflow specification and use metadata to create summaries. Workflows which lack metadata do not make good summaries even if they are useful and relevant as search criteria. This work investigates the possibility of creating meaningful and usable summaries or snippets based on structure and specification of workflows. We shall  (1) present relevant published work done regarding snippet building techniques (2) explain how we mapped current techniques to our work (3) describe how we identified techniques from interface design theory in order to make usable graphical interface (4) present implementation of two new algorithms for workflow graph compression and their complexity analysis (5) identify future work in our implementation and outline open research problems in snippet building field.

  • 41.
    Bhide, Priyanka
    Linköpings universitet, Institutionen för systemteknik, Datorteknik.
    Design and Evaluation of Aceelerometer Based Mobile Authentication Techniques2017Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Smartphones’ usages are growing rapidly. Smart phone usages are not limited to the receiving/calling or SMSing anymore. People use smartphone for online shopping, searching various information in the web, bank transactions, games, different applications for different usages etc. Anything is possible by just having a smartphone and the internet. The more usages of the smartphone also increase keeping more secrete information about the user in the phone. The popularity is increasing and so is different ways to steal/hack the phones. There are many areas which require further investigation in the field of smartphone security and authentication.

    This thesis work evaluates the scope of different inbuilt sensors in smartphones for mobile authentication based techniques. The Android Operating system was used in the implementation phase. Android OS has many open source library and Services which have been used for the sensor identification using Java Android platform.

    Two applications using Accelerometer sensor and one using Magnetometer sensor were developed. Two foremost objectives of this thesis work were-1) To figure it out the possibilities of sensor based authentication technique. 2) To check the end user perception/opinion about the applications.

    Usability testing was conducted to gather the user’s assessments/vision of the applications. Two methods which were used for usability testing are named Magical move and Tapping. Users (Most of them) have shown interest and inclination towards tapping application. Although, some users were also expressed inhibitions using both sensor based methods.

  • 42.
    Billman, Johan
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Hellström, Victor
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Abusing Keep-Alive Forwarding to flood a VANET: When safety messages become a safety risk2016Självständigt arbete på grundnivå (högskoleexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Cooperative Intelligent Transport Systems (C-ITS) enable vehicles to cooperate with each other and can be used to increase traffic safety and traffic flow. There are several standard initiatives for C-ITS, such as WAVE in the US, ARIB in Japan and ETSI ITS G5 in Europe.

    Decentralized Environment Notification Message (DENM) is a kind of message within ETSI TC ITS. DENMs are event-triggered, multi-hop notification messages that can be for- warded using Keep-Alive Forwarding (KAF).

    In this thesis, KAF is used to flood the network with DENMs sent from a single attack- ing vehicle. Using the simulation tools SUMO, OmNet++ and Veins, a highway scenario is studied. In the scenario, a vehicle sends out a DENM into a network that is being attacked by one other vehicle. Due to how KAF allows messages to be forwarded the other vehicles help flood the network. The results clearly indicate that KAF can be abused to create a Denial of Service (DoS) attack. After just a few seconds, the attack has introduced large de- lays and very high packet loss. The delay to receive a DENM is increased by several orders of magnitude and the packet loss reach unacceptable levels. By getting DENMs several seconds after they are needed, or by not getting them at all, could lead to traffic hazards. 

  • 43.
    Biswas, Kamal
    et al.
    IITD, India.
    Mohammed, Saif Khan
    IITD, India.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Efficient Techniques for Broadcast of System Information in mmWave Communication Systems2018Ingår i: 2018 IEEE 19TH INTERNATIONAL WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS (SPAWC), IEEE , 2018, s. 366-370Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we consider Millimeter wave (mmWave) Massive MIMO systems where a large antenna array at the base station (BS) serves a few scheduled terminals. The high dimensional null space of the channel matrix to the scheduled terminals is utilized to broadcast system information to the non-scheduled terminals on the same time-frequency resource. Our analysis reveals the interesting result that with a sufficiently large antenna array this non-orthogonal broadcast strategy requires significantly less total transmit power when compared to the traditional orthogonal strategy where a fraction of the total resource is reserved for broadcast of system information.

  • 44.
    Björklund, Daniel
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Implementation of a Software-Defined Radio Transceiver on High-Speed Digitizer/Generator SDR142012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis describes the specification, design and implementation of a software-defined radio system on a two-channel 14-bit digitizer/generator. The multi-stage interpolations and decimations which are required to operate two analog-to-digital converters at 800 megasamples per second (MSps) and two digital-to-analog converters at 1600 MSps from a 25 MSps software-side interface, were designed and implemented. Quadrature processing was used throughout the system, and a combination of fine-tunable low-rate mixers and coarse high-rate mixers were implemented to allow frequency translation across the entire first Nyquist band of the converters. Various reconstruction filter designs for the transmitter side were investigated and a cheap implementation was done through the use of programmable base-band filters and polynomial approximation.

  • 45.
    Björklund, Fredrik
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Karlström, Elin
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Enabling Testing of Lateral Active Safety Functions in a Multi-rate Hardware in the Loop Environment2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    As the development of vehicles moves towards shorter development time, new ways of verifying the vehicle performance is needed in order to begin the verification process at an earlier stage. A great extent of this development regards active safety, which is a collection name for systems that help both avoid accidents and minimize the effects of a collision, e.g brake assist and steering control systems. Development of these active safety functions requires extensive testing and verification in order to guarantee the performance of the functions in different situations. One way of testing these functions is to include them in a Hardware in the Loop simulation, where the involved hardware from the real vehicle are included in the simulation loop.

    This master thesis investigates the possibility to test lateral active safety functions in a hardware in the loop simulation environment consisting of multiple subsystems working on different frequencies. The subsystems are all dependent of the output from other subsystems, forming an algebraic loop between them. Simulation using multiple hardware and subsystems working on different frequencies introduces latency in the simulation. The effect of the latency is investigated and proposed solutions are presented. In order to enable testing of lateral active safety functions, a steering model which enables the servo motor to steer the vehicle is integrated in the simulation environment and validated.

  • 46.
    Björkman Höglund, Matilda
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Olsson, Maria
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    The future of e-commerce2017Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    E-handeln växer eftersom allt fler personer handlar via internet. Konsumtionsmönstret ändras och allt fler söker sig till företags hemsidor för att köpa varor online. Även tjänster som exempelvis musik och film blir mer internetbaserat och köps och beställs ofta via internet. Nu kan nästan vad som helst köpas online, allt från mat till kläder och elektronik. E-handeln är ett smidigare och ibland billigare komplement till den traditionella handeln. Detta underlättar för kunderna och kan frigöra mer tid till de personer som e-handlar. Med den ökade e-handeln uppstår det också problem. Det behövs bra distributionsupplägg som kan ta hand om alla varor som ska transporteras. Den ökade e-handeln innebär fler transporter i städerna. Om e-handeln fortsätter att öka och det blir ännu fler transporter, vilka konsekvenser får det? Vilka olika distributionsupplägg kommer det att finnas i framtiden för att kunna leverera varor till kunderna på ett effektivt sätt? I det här examensarbetet har klädbranschen och dess e-handel undersökts. Det som har studerats, är hur branschen påverkar transporterna kopplat till e-handeln. Intervjuer med olika företag har genomförts i examensarbetet för att få en överblick över hur deras e-handel har utvecklats över tid samt hur de tror att e-handeln kommer att se ut i framtiden. Intervjuer med teoretiker som arbetar med citylogistik har även gjorts, för att få information hur de tror e-handeln kommer påverka transporterna kopplat till e-handeln. I framtiden kommer det troligtvis inte användas några nya distributionsupplägg, utan de som redan finns kommer bli mer utvecklade. De distributionsupplägg som finns idag är att kunderna hämtar sina varor via ett ombud, i en butik/lagerlokal, paketombud eller att varorna skickas hem till kunden. I framtiden kan det bli allt vanligare med hemleverans och att kunderna eventuellt kommer att få styra sina leveranser mer än vad som är möjligt idag. För att se konsekvenserna av transporterna kopplat till e-handeln presenteras två olika fall. Dessa två fall delas upp i åtta olika scenarier. Dessa scenarier är uppbyggda efter olika antaganden om vilka transportmedel som används och i vilken utsträckning. Det scenario som gav lägst koldioxidutsläpp och lägst fordonskilometer var det scenario där 100 % av godset levereras till ett utlämningsställe via en samlastningscentral utan att kunderna använder sin personbil mer. En förändrad volym av e-handel ger olika konsekvenser på transporterna, beroende på vilken typ av distributionsupplägg som används och vilket transportmedel som utnyttjas, samt vilken systemavgränsning som görs. Generellt sett tyder det på att antalet transportkilometer kopplat till e-handeln kommer att öka i framtiden. Vad gäller koldioxidutsläppen är det svårare att göra en bedömning, beroende på vilka transportmedel som kommer att användas i framtiden men också på den tekniska utvecklingen av dessa. Även om antalet fordonskilometer ökar kan effektivare transporter leda till minskade koldioxidutsläpp.

  • 47.
    Björnson, Emil
    KTH Royal Institute Technology, Sweden; Supelec, France.
    Kountouris, Marios
    CentraleSupelec, France.
    Debbah, Merouane
    CentraleSupelec, France.
    Massive MIMO Systems with Non-Ideal Hardware: Energy Efficiency, Estimation, and Capacity Limits2014Ingår i: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 60, nr 11, s. 7112-7139Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of large-scale antenna arrays can bring substantial improvements in energy and/or spectral efficiency to wireless systems due to the greatly improved spatial resolution and array gain. Recent works in the field of massive multiple-input multiple-output (MIMO) show that the user channels decorrelate when the number of antennas at the base stations (BSs) increases, thus strong signal gains are achievable with little interuser interference. Since these results rely on asymptotics, it is important to investigate whether the conventional system models are reasonable in this asymptotic regime. This paper considers a new system model that incorporates general transceiver hardwareimpairments at both the BSs (equipped with large antenna arrays) and the single-antenna user equipments (UEs). As opposed to the conventional case of ideal hardware, we show that hardwareimpairments create finite ceilings on the channel estimation accuracy and on the downlink/uplink capacity of each UE. Surprisingly, the capacity is mainly limited by the hardware at the UE, while the impact of impairments in the large-scale arrays vanishes asymptotically and interuser interference (in particular, pilot contamination) becomes negligible. Furthermore, we prove that the huge degrees of freedom offered by massive MIMO can be used to reduce the transmit power and/or to tolerate larger hardware impairments, which allows for the use of inexpensive and energy-efficient antenna elements.

  • 48.
    Björnson, Emil
    KTH Royal Institute Technology, Sweden; Supelec, France.
    Debbah, Merouane
    CentraleSupelec, France.
    Ottersten, Björn
    KTH Royal Institute of Technology.
    Multi-Objective Signal Processing Optimization: The Way to Balance Conflicting Metrics in 5G Systems2014Ingår i: IEEE signal processing magazine (Print), ISSN 1053-5888, E-ISSN 1558-0792, Vol. 31, nr 6, s. 14-23Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The evolution of cellular networks is driven by the dream of ubiquitous wireless connectivity: any data service is instantly accessible everywhere. With each generation of cellular networks, we have moved closer to this wireless dream; first by delivering wireless access to voice communications, then by providing wireless data services, and recently by delivering a Wi-Fi-like experience with wide-area coverage and user mobility management. The support for high data rates has been the main objective in recent years [1], as seen from the academic focus on sum-rate optimization and the efforts from standardization bodies to meet the peak rate requirements specified in IMT-Advanced. In contrast, a variety of metrics/objectives are put forward in the technological preparations for fifth-generation (5G) networks: higher peak rates, improved coverage with uniform user experience, higher reliability and lower latency, better energy efficiency (EE), lower-cost user devices and services, better scalability with number of devices, etc. These multiple objectives are coupled, often in a conflicting manner such that improvements in one objective lead to degradation in the other objectives. Hence, the design of future networks calls for new optimization tools that properly handle the existence of multiple objectives and tradeoffs between them.

  • 49.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    de Carvalho, Elisabeth
    Aalborg University, Denmark.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Popovski, Petar
    Aalborg University, Denmark.
    Random Access Protocol for Massive MIMO: Strongest-User Collision Resolution (SUCR)2016Ingår i: 2016 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE , 2016, s. 820-825Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wireless networks with many antennas at the base stations and multiplexing of many users, known as Massive MIMO systems, are key to handle the rapid growth of data traffic. As the number of users increases, the random access in contemporary networks will be flooded by user collisions. In this paper, we propose a reengineered random access protocol, coined strongest-user collision resolution (SUCR). It exploits the channel hardening feature of Massive MIMO channels to enable each user to detect collisions, determine how strong the contenders channels are, and only keep transmitting if it has the strongest channel gain. The proposed SUCR protocol can quickly and distributively resolve the vast majority of all pilot collisions.

  • 50.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    de Carvalho, Elisabeth
    Aalborg University, Denmark.
    Sorensen, Jesper H.
    Aalborg University, Denmark.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Popovski, Petar
    Aalborg University, Denmark.
    A Random Access Protocol for Pilot Allocation in Crowded Massive MIMO Systems2017Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, nr 4, s. 2220-2234Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The massive multiple-input multiple-output (MIMO) technology has great potential to manage the rapid growth of wireless data traffic. Massive MIMO achieves tremendous spectral efficiency by spatial multiplexing many tens of user equipments (UEs). These gains are only achieved in practice if many more UEs can connect efficiently to the network than today. As the number of UEs increases, while each UE intermittently accesses the network, the random access functionality becomes essential to share the limited number of pilots among the UEs. In this paper, we revisit the random access problem in the Massive MIMO context and develop a reengineered protocol, termed strongest-user collision resolution (SUCRe). An accessing UE asks for a dedicated pilot by sending an uncoordinated random access pilot, with a risk that other UEs send the same pilot. The favorable propagation of massive MIMO channels is utilized to enable distributed collision detection at each UE, thereby determining the strength of the contenders signals and deciding to repeat the pilot if the UE judges that its signal at the receiver is the strongest. The SUCRe protocol resolves the vast majority of all pilot collisions in crowded urban scenarios and continues to admit UEs efficiently in overloaded networks.

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