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  • 151.
    Beckman, Claes
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth. KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Thaung, Jörgen
    Sjöstrand, Johan
    In-vitro lens scatter measurements and glare testing1994Konferensbidrag (Övrigt vetenskapligt)
  • 152.
    Bellagamba, Elisa
    et al.
    Ericsson Research.
    Andersson, Loa
    Ericsson AB.
    Sköldström, Pontus
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Ward, Dave
    Drake, John
    Configuration of Pro-Active Operations, Administration, and Maintenance (OAM) Functions for MPLS-based Transport Networks using LSP Ping2013Övrigt (Övrig (populärvetenskap, debatt, mm))
  • 153.
    Ben Slimane, Slimane
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Approximation to the Symmetric Capacity of Rayleigh Fading Channels with Multi-Level Signals2006Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 0, nr 3, s. 129-131Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A simple approximation for the symmetric capacity of Rayleigh fading channels with finite input alphabet and ideal channel state information is proposed in this letter. This approximation is quite tight over all SNR ranges and can be considered as a good alternative for estimating the symmetric channel capacity for both AWGN and Rayleigh fading channels.

  • 154.
    Ben Slimane, Slimane
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Combined Transmitter Diversity and Multi-Level Modulation Techniques2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    Orthogonal transmitter diversity such as frequency diversity and time diversity is quite simple to implementand, with optimum signal combining, can take full advantage of fading multipath channels. However, such a scheme has a bandwidth efficiency that decreases inversely with the number of diversity branches making it less attractive in wireless communications applications. This paper considers combined orthogonal transmitter diversity and multi-level linear modulation techniques. The idea is to view the signal constellations of the modulation scheme in an augmented signal space formed by the modulation signal dimension and the number of branches of the transmitter diversityscheme. This augmented signal space provides a good spread for the modulation signal points and can be quite efficientfor high-level linear modulation techniques. The obtained results show that this combined scheme, not only improves the system performance in both additive white Gaussian noise and fading multipath channels, but also improves the bandwidth efficiency of orthogonal transmitter diversity.

  • 155.
    Ben Slimane, Slimane
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Combined transmitter diversity and multi-level modulation techniques2006Ingår i: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. 39, nr 2, s. 215-227Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Orthogonal transmitter diversity such as frequency diversity and time diversity is quite simple to implement and, with optimum signal combining, can take full advantage of fading multipath channels. However, such a scheme has a bandwidth efficiency that decreases inversely with the number of diversity branches making it less attractive in wireless communications applications. This paper considers combined orthogonal transmitter diversity and multi-level linear modulation techniques. The idea is to view the signal constellations of the modulation scheme in an augmented signal space formed by the modulation signal dimension and the number of branches of the transmitter diversity scheme. This augmented signal space provides a good spread for the modulation signal points and can be quite efficient for high-level linear modulation techniques. The obtained results show that this combined scheme, not only improves the system performance on both additive white Gaussian noise and fading multipath channels, but also improves the bandwidth efficiency of orthogonal transmitter diversity.

  • 156.
    Ben Slimane, Slimane
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Reducing the Peak-to-Average Power Ratio of OFDM Signals Through Precoding2007Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 56, nr 2, s. 686-695Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Orthogonal-frequency-division-multiplexing (OFDM) techniques allow the transmission of high data rates over broadband radio channels subject to multipath fading without the need for powerful channel equalization. However, they are very sensitive to nonlinear effects due to the high peak-to-average power ratio (PAPR) owned by their transmitted signals. This paper proposes an efficient technique for reducing the PAPR of OFDM signals. The proposed technique is data-independent and, thus, does not require new processing and optimization for each transmitted OFDM block. The reduction in PAPR of the OFDM signal is obtained through a proper selection of a precoding scheme that distributes the power of each modulated symbol over the OFDM block. The obtained results show that this precoding scheme is an attractive solution to the PAPR problem of OFDM signals. It is shown, through computer simulations, that the PAPR of precoded OFDM signals approaches that of single-carrier signals. The good improvement in PAPR given by the present technique permits the reduction of the complexity and cost of the transmitter significantly. The precoding schemes also take advantage of the frequency variations of the communication channel and can provide considerable performance gain in fading-multipath channels.

  • 157.
    Ben Slimane, Slimane
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Li, Xuesong
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Bo, Zhou
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Syed, Nauroze
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Dheim, Mohammad Abu
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Delay Optimization in Cooperative Relaying with Cyclic Delay Diversity2008Ingår i: 2008 IEEE International Conference On Communications, Proceedings: Vols 1-13, 2008, s. 3553-3557Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cooperative relaying has recently been recognized as an alternative to MIMO in a typical multi cellular environment Inserting random delays at the non-regenerative fixed relays, further improve the system performance. However, random delay results in limited performance gain from multipath diversity. In this paper, two promising delay optimization schemes are introduced for a multi cellular OFDM system with cooperative relaying with stationary multiple users and fixed relays. Both of the schemes basically aim to take the most advantages of the potential frequency selectivity by inserting pre-determined delays at the relays, in order to further improve the system performance (coverage and throughput). Evaluation results for different multipath fading environments show that the system performance with delay optimization increases tremendously compared with the case of random delay.

  • 158.
    Ben Slimane, Slimane
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Naik, Siddharth
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Toyserkani, Arash
    An Improved Cancellation Multiuser Detector for Narrowband Signals2005Ingår i: VTC 2005-Spring: 2005 IEEE 61st Vehicular Technology Conference, New York: IEEE , 2005, s. 973-977Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper examines the possibility of reducing error propagation in the successive interference cancellation multiuser detector (SIC-MUD) for a narrowband system. A simple sequence estimation algorithm is employed, working on a symbol by symbol user basis, not affecting the operation of FEC decoding if present. Operating along the stages of the SIC-MUD scheme, this algorithm has a complexity that increases only linearly with the number of users and thus can be used for a larger number of users, as against the optimum joint detection-MUD (JD-MUD), whose complexity increases exponentially with the number of users. Investigation is carried out for both AWGN and Rayleigh fading channels. The obtained results show that the Improved SIC-MUD scheme reduces the error propagation considerably and, with its low complexity, can be a good alternative for the JD-MUD scheme.

  • 159.
    Ben Slimane, Slimane
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Osseiran, Afif
    Ericsson Research, Ericsson AB, Stockholm, Sweden.
    Relay Communication with Delay Diversity for Future Communication Systems2006Ingår i: 2006 IEEE 64TH VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-6, New York: IEEE , 2006, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we consider relay communication as a way of increasing the diversity gain in fading wireless environments. The idea is to combine relay communication with delay diversity where each relay introduces a certain time delay to the signal before forwarding. The result is an increased frequency selectivity in the relay channel which can be exploited at the receiver. The obtained results show that, for single carrier signals with frequency domain equalization, considerable performance gain is obtained.

  • 160.
    Ben Slimane, Slimane
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Zhou, Bo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Li, Xuesong
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Delay Optimization in Cooperative Relaying with Cyclic Delay Diversity2008Ingår i: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, s. 736818-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cooperative relaying has recently been recognized as an alternative to MIMO in a typical multicellularenvironment. Inserting random delays at the nonregenerative fixed relays further improve the system performance.However, random delays result in limited performance gain from multipath diversity. In this paper, two promisingdelay optimization schemes are introduced for a multicellular OFDM system with cooperative relaying withstationary multiple users and fixed relays. Both of the schemes basically aim to take the most advantages ofthe potential frequency selectivity by inserting predetermined delays at the relays, in order to further improve thesystem performance (coverage and throughput). Evaluation results for different multipath fading environments showthat the system performance with delay optimization increases tremendously compared with the case of randomdelay.

  • 161. Bentley, F.
    et al.
    Tollmar, Konrad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab).
    The power of mobile notifications to increase wellbeing logging behavior2013Ingår i: CHI '13 Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, ACM Digital Library, 2013, s. 1095-1098Konferensbidrag (Refereegranskat)
    Abstract [en]

    Self-logging is a critical component to many wellbeing systems. However, self-logging often is difficult to sustain at regular intervals over many weeks. We demonstrate the power of passive mobile notifications to increase logging of wellbeing data, particularly food intake, in a mobile health service. Adding notifications increased the frequency of logging from 12% in a one-month, ten-user pilot study without reminders to 63% in the full 60-user study with reminders included. We will discuss the benefits of passive notifications over existing interruptive methods.

  • 162. Bentley, F
    et al.
    Tollmar, Konrad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Dernirdjian, D
    Koile, K
    Darrell, T
    Perceptive presence2003Ingår i: IEEE Computer Graphics and Applications, ISSN 0272-1716, E-ISSN 1558-1756, Vol. 23, s. 26-36Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Perceptive presence systems automatically convey awareness of user states to a remote location or application without the user having to perform explicit commands or mode selection. The article describes a component-based architecture for creating presence applications using perceptual user interface widgets. Each widget performs a machine perception function, such as tracking a face or monitoring activity in a specific 3D location. Widgets provide an abstraction barrier between the perception algorithms and the needs of application writers. Two example applications developed using this framework are presented: one uses a luminous display to express a user’s availability for communication to a colleague at a remote location, and a second uses activity to control devices in a context-aware environment.

  • 163. Bentley, Frank
    et al.
    Tollmar, Konrad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Designing From Data: A Case Study From the Health Mashups Service2013Ingår i: Workshop on Informing Future Design via Large-Scale Research Methods and Big Data, 2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Instrumentation of mobile service interactions now allows for the ability to understand use in new ways and to base the design of system iterations as well as future services on data obtained from use “in the wild”over extended periods of time. This position paper will detail a few specific instances in the Health Mashupsproject where we were able to use usage data to improve the design and to create design implications to increase engagement in new services.

  • 164. Bentley, Frank
    et al.
    Tollmar, Konrad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Stephenson, Peter
    Levy, Laura
    Jones, Brian
    Robertson, Scott
    Price, Ed
    Catrambone, Richard
    Wilson, Jeff
    Health Mashups: Presenting Statistical Patterns between Wellbeing Data and Context in Natural Language to Promote Behavior Change2013Ingår i: ACM Transactions on Computer-Human Interaction, ISSN 1073-0516, E-ISSN 1557-7325, Vol. 20, nr 5, s. 30-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    People now have access to many sources of data about their health and wellbeing. Yet, most people cannot wade through all of this data to answer basic questions about their long-term wellbeing: Do I gain weight when I have busy days? Do I walk more when I work in the city? Do I sleep better on nights after I work out? We built the Health Mashups system to identify connections that are significant over time between weight, sleep, step count, calendar data, location, weather, pain, food intake, and mood. These significant observations are displayed in a mobile application using natural language, for example, "You are happier on days when you sleep more." We performed a pilot study, made improvements to the system, and then conducted a 90-day trial with 60 diverse participants, learning that interactions between wellbeing and context are highly individual and that our system supported an increased self-understanding that lead to focused behavior changes.

  • 165.
    Berg, Miguel
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Markendahl, Jan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    A Concept for Public Access to Privately Operated Cooperating Local Access Points2005Ingår i: IEEE Vehicular Technology Conference, New York: IEEE , 2005, s. 2959-2963Konferensbidrag (Refereegranskat)
    Abstract [en]

    For many future mobile communication scenarios, the traditional operators are believed to be unable or unwilling to support some services, mainly for cost reasons. Thus, there will always be gaps in the coverage and capacity of these systems.   This paper describes a non-conventional and low-cost concept for wireless access using privately operated local access points (LAPs) contributing to the public access, thus adding coverage and capacity in e.g. homes, offices and public hotspots.  The work has been performed in the EU-funded Ambient Networks (AN) project. A migration path is presented, starting with today’s LAPs for private-use-only to LAPs for public use, implementing the AN objective of “access for anyone to any network”. The main contributions in the paper are 1) the identification and analysis of re-use of fixed and wireless transport and access capacity using adhoc mesh networks between LAPs and 2) the use of network advertising &  discovery for LAP concepts.

  • 166.
    Berggren, Fredrik
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    An error bound for moment matching methods of lognormal sum distributions2005Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 6, nr 6, s. 573-577Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To evaluate the distribution function of a sum of lognormal random variables. it is common to use approximation methods based on moment matching.  These include the classical and simple Fenton-Wilkinson method, which approximates the sum with a single lognormal variable, having the first two moments matched.  In this letter, we give a closed-form bound for the error of the distribution function, resulting from moment matching methods.  Numerical evaluation for a typical CDMA case, shows that the bound becomes tight for large processing gains.  The error bound can also be used to find bounds on the outage probability.

  • 167.
    Berggren, Fredrik
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Spectral-effciency analysis in noncooperative interference environments2005Ingår i: 2005 IEEE Wireless Communications and Networking Conference, Vols 1-4: WCNC 2005: Broadband Wireless for the Masses Ready for Take-Off, IEEE Communications Society, 2005, s. 741-745Konferensbidrag (Refereegranskat)
    Abstract [en]

    The current focus on innovative spectrum policies and efficient wireless bandwidth utilization has motivated research on methods for dynamic spectrum access. By letting systems share the spectrum, trunking gains and better utilization of the bandwidth is predicted. From a technical point of view, the paradigm shift to open frequency bands implies a need to investigate and verify resulting capacity gains. In this paper, we give a general method for evaluating system capacity subject to outage probability constraints over fading channels, in an unlicensed environment with uncoordinated systems. The channel fading effects include attenuation, shadowing and multipath propagation and we end up with expressions, solved by numerical integration. The spectrum sharing is here performed by means of autonomous dynamic channel allocation (DCA), and we compare several DCA methods, e.g., maximum SIR and random DCA.

  • 168.
    Berggren, Fredrik
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Bria, Aurelian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Veronesi, Riccardo
    Multi-radio resource management for ambient networks2005Ingår i: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, IEEE , 2005, s. 942-946Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Ambient Networks concept targets forthcoming dynamic communication environments, characterized by the presence of a multitude of different wireless devices, radio access technologies, network operators and business actors, which can form instant inter-network agreements with each other. MultiRadio Resource Management (MRRM) mechanisms, coordinating several radio accesses, fulfill a key role for providing wireless services with improved resource efficiency, coverage and service quality. This paper presents an MRRM concept for Ambient Networks, describes the principal MRRM functions and discusses design criteria.

  • 169.
    Berggren, Fredrik
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Litjens, Remco
    TNO ICT, The Netherlands.
    Performance analysis of access selection and transmit diversity in multi-access networks2006Ingår i: MOBICOM 2006, ACM , 2006, s. 251-261Konferensbidrag (Refereegranskat)
    Abstract [en]

    Motivated by the "beyond 3g" vision of radio access network integration and coordinated radio resource management, a purely analytical performance assessment is presented for a single access point integrating multiple radio accesses. Principal focus is placed on the evaluation of multi-user diversity, multi-access diversity and trunking gains. Scenarios with persistent and non-persistent data flows are investigated, concentrating on throughput and transfer time performance, respectively. A number of numerical experiments are included in order to quantify the relative contribution of the distinguished aspects to the performance gain. These experiments indicate that the exploitation of multi-user diversity with a channel-aware access selection scheme attains the most significant gains, while also the trunking gain that is due to an above-proportional performance enhancement when aggregating system-specific capacities, is noted to be significant. The assignment of multiple accesses to a given flow is demonstrated to have limited potential.

  • 170.
    Bhatia, Nupur
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Policy Management in Context-Aware Networks2007Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Ambient Network är ett EU-finansierat project inom det 6:e ramprogrammet.Projektets mål är att möjliggöra samarbete mellan heterogena nätverk, som använderbåde dagens men även framtidens trådlösa teknologier, för att minimeraslutanvändarens insats för att nå den tjänst de är intresserade av – oberoende av platseller vilket nätverk de använder. På grund av den stora delen av mobila användaresom kräver omedelbar och dynamisk tillgång till tjänster måste dessa nätverk gåsamman ’on the fly’ utan tidigare konfigurering.Användningen av context information i Ambient Networks kan elmininera behovet avförkonfigurering av nätverk, följaktligen blir de då autonoma. Dock, ett problem somuppkommer med detta är att den fria och okontrollerade spridningen av contextinformation bryter integriteten för deltagarna. Det är väldigt viktigt att ta itu med dettaproblem för att kunna kontrollera vilka som har tillgång till vilken contextinformation. Den här kontrollen kan uppnås genom väldefinierade policies. Dettaskapar ett behov av ett ramverk inom ContextWare arkitekturen för att skydda dentillgängliga context informationen.

    Den här uppsatsen är en del i ansträngningen att skapa en policy baserad infrastrukturför attestering av tillgång till context information inom Ambient Networks. Uppsatsenundersöker och designar en arkitektur för ett policy handhavande system som ärbaserat på OASIS XACML, den bygger vidare på arkitekturen för handhavande avcontext information i Ambient Networks. Utöver policy hantering inom ett ambientnetwork skapas också policy hantering mellan ambient networks när de förenas. Denframtagna arkitekturen är därefter implementerad för att visa på konceptets hållbarhet. En sammanslagning av två policy handhavande system när två nätverk slås ihop ärbehandlat endast i teorin, det är inte implementerat.

    Designen utvärderas genom att köra test på den implementerade versionen ochdärefter analysera och visa resultaten i rapporten. Dessa test innehåller mätningar avfördröjningen av en enda begäran samt flera, responstiden i ett system med policyhanteringjämfört med utan samt prestandan i ett policy-hanteringssystem med en litenmängd policies jämfört med en större mängd policies.

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  • 171.
    Bhattacharya, Sujata
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Dedicated Channel Capacity of a WCDMA system with HSDPA Channels2005Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Keeping an eye on the future upcoming demands for mobile applications, 3GPP has the target to enhance the downlink packet data rate in many folds.  As a result, WCDMA specifications have been evolved with the addition of a new feature called HSDPA (High Speed Downlink Packet Access) in Release 5.  The goal of HSDPA has been to increase the system capacity by increasing the data rate and reduce the round trip delay.  The increase of system capacity has been achieved by dynamic sharing of code resource and certain amount of power.

    A number of research papers have shown that HSDPA will enhance WCDMA system with the fulfillment of the above objective.  As per the business forcast, HSDPA will start getting deployed towards the end of this year (2005).  Howe ver, in a real deployment scenario, it may happen that some of the cells are implemented with HSDPA and some are not yet; what will happen to the capaci ty of those cells without HSDPA?  When HSDPA is implemented in a cell, the base station uses more power, imparting more interference to the neighbouring cells, thus affecting their dedicated channel capacity.  In addition to the higher power, if the availability of data in the HSDPA channel varies, then the interf erence to the neighbouring cell might be larger and °uctuating, in turn, the dedicated channel capacity of the neighbouring cells might be affected.

    This scenario has been studied in this master thesis.  Mainly, it has been studied how is the dedicated channel capacity of a cell without HSDPA affected by the introduction of an HSDPA channel in adjacent cell.  Does this influence depend on the data traffic on the HSDPA channel?

    With the simple system model used, it has been observed that though there is a change in the capacity of the system after implementing HSDPA in adjacent cells, the variation is negligible.  It has been found that the decrease in the dedicated channel capacity is more if the HSDPA data traffic is larger.  The fluctuating data in HSDPA channel has not degraded the capacity further; it is only the higher power, which has affected the dedicated channel capacity. However, in all these cases, variation can be considered as negligible.  So, it has been concluded that there is no impact on the capacity of cells which are not with HSDPA after implementing HSDPA in adjacent cells.  Considering the limitations in this study, it has been suggested to study this aspect further by using a more complex system model to find out the reality.

  • 172.
    Bin, Yang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Using Six Sigma Methodology to improve the performance of the Shipment Test2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Konkurrens och ledtid tryck motiverar oss att hitta nya och bättre vägar att kontinuerligt förbättra resultatet av vårt arbete. Betoningen av förbättring av både effektivitet och kvalité har blivit allt mer signifikant i våra dagliga aktiviteter. Prestationen av Ericssons AXE/APZ produkter under sändningens test fas är en sådan aktivitet och det är där fokusen på detta tes projekt ligger. En av de grundläggande principerna av sändnings test är att se till att test kampanjer avslutat i tid. Under de senaste årtionden har företag spenderat stora summor tid och pengar att förbättra test kvalité och effektivitet. Tyvärr har resultaten inte vart så bra som förväntat. Det ser ut så att det är mycket svårt att förbättra sändnings test prestationen när du använder traditionella test förvaltningsmetoder. Six Sigma metodik har blivit tillämpad som en ledningsfilosofi fokuserad på att förbättra effektivitet och prestation under test exekverings perioden.

    Denna tes ger en introduktion till Six Sigma tillvägagångssättet, inklusive konceptet från Sig Sigma, dess historia, utveckling och metodik. Mer specifikt använder vi Define, Measure, Analyze, Improve och Control (DMAIC) tillvägagångssätt för att utvärdera prestationen av Ericssons AXE/APZ sändnings testning.  Denna process kräver definitionen av prestationsmålet, mätningar av nuvarande prestanda och analys av data för att hitta rötterna till orsakerna av problemen. Resultatet av denna definition, mätning och analys var en rad förslag till förbättringar och kontroll av den förbättrade processen för att säkerhetsställa hållbara förbättrade prestations resultat.

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  • 173.
    Blomgren, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Traffic estimation and traffic sensitive scheduling in mobile ad hoc networks2005Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Different CSMA variants (Carrier Sense Multiple Access), such as the widely spread WLAN-standards IEEE 802.11, are often suggested as MAC-protocols in ad hoc networks. Many of the problems that a CSMA-system suffers in a one-hop network are aggravated in a multi-hop network. This makes CSMAschemes less attractive to use in ad hoc networks. Several methods of scheduling transmissions in TDMA and in its more evolved form STDMA (Spatial reuse TDMA) have proved to give a higher maximum throughput than CSMA. TSST (Traffic Sensitive Scheduled TDMA) is proposed in this work, it is a novel algorithm for scheduling transmissions.

    TSST makes schedules based on the estimated queue length in every node.

    It is assumed that reports of queue lengths cannot instantaneously propagate from node to node. The updates will be received with a fixed delay (lag). Using this lagged information with support of traffic estimates and the knowledge of previous send schedules, TSST is capable of estimate the current queue lengths.

    The results show that TSST can achieve higher throughput than CSMA. The results also show that TSST can achieve lower end to end delay than idealised forms of prior TDMA-schemes, even if it has to estimate the queue lengths with quite old information and inaccurate traffic estimates.

    It is concluded that TSST is an efficient way of scheduling for TDMA and that the accuracy of the traffic estimator is of great importance.

  • 174.
    Bogdanov, Kirill
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Latency Dataset for the paper "The Nearest Replica Can Be Farther Than You Think"2015Dataset
  • 175.
    Bogdanov, Kirill
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Reducing Long Tail Latencies in Geo-Distributed Systems2016Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [sv]

    Databehandlingstjänster är en välintegrerad del av det moderna samhället. Miljontals människor förlitar sig dagligen på dessa tjänster för kommunikation, samordning, handel, och åtkomst till information. För att möta höga krav implementeras och placeras många populära tjänster som geo-fördelning applikationer ovanpå tredje parters virtuella molntjänster. Det ligger emellertid i sakens natur att sådana utplaceringar resulterar i varierande prestanda. För att leverera höga servicekvalitetskrav behöver sådana system sträva efter att ständigt anpassa sig efter ändrade förutsättningar genom att övervaka tillståndsändringar och ta realtidsbeslut, som till exempel val av server peering, replika placering, och val av kvorum.

    Den här avhandlingen avser att förbättra kvaliteten på realtidsbeslut tagna av geo-fördelning system. Detta kan uppnås genom: (1) en bättre förståelse av underliggande utplaceringsvillkor, (2) systematisk och noggrann testning av beslutslogik redan implementerad i dessa system, och (3) en tydlig inblick i nätverket och systemtillstånd som tillåter dessa tjänster att utföra mer informerade beslut.

    Vi utförde en långsiktig korsa datacenter latensmätning av Amazons EC2 molntjänst. Mätdata användes sedan till att kvantifiera variationen av nätverkstillstånd och demonstrera dess inverkan på prestanda för system placerade ovanpå denna molntjänst.

    Därnäst validerades en applikations beslutslogik vanlig i populära lagringssystem genom att undersöka replika valalgoritmen. GeoPerf, ett verktyg som tillämpar symbolisk exekvering och lättviktsmodellering för systematisk testning av replika valalgoritmen, användes för att testa två populära lagringssystem och vi hittade en bugg i båda.

    Genom traceroute och envägslatensmätningar över EC2 demonstrerar vi ihängande korrelation mellan nätverksvägar och nätverkslatens. Vi introducerar också EdgeVar, ett verktyg som frikopplar dirigering och trängsel baserat på förändringar i nätverkslatens. Genom att tillhandahålla denna ytterligare information förbättrade vi kvaliteten på latensuppskattningen och stabiliteten på nätverkets val av väg.

    Slutligen introducerade vi Tectonic, ett verktyg som följer en applikations begäran och gensvar på både användare-läge och kernel-läge. Tillsammans med EdgeVar förses en komplett bild av fördröjningar associerade med varje beräkningssteg av begäran och gensvar. Med Tectonic kunde vi analysera inverkan av att dela CPUer i en virtuell miljö och kan avslöja hypervisor schemaläggningsprinciper. Vi argumenterar för betydelsen av att känna till dessa principer och föreslå användningen av de i beslutsprocessen.

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  • 176.
    Bogdanov, Kirill
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Peón-Quirós, Miguel
    Complutense University of Madrid.
    Maguire Jr., Gerald Q.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Kostic, Dejan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    The Nearest Replica Can Be Farther Than You Think2015Ingår i: Proceedings of the ACM Symposium on Cloud Computing 2015, Association for Computing Machinery (ACM), 2015, s. 16-29Konferensbidrag (Refereegranskat)
    Abstract [en]

    Modern distributed systems are geo-distributed for reasons of increased performance, reliability, and survivability. At the heart of many such systems, e.g., the widely used Cassandra and MongoDB data stores, is an algorithm for choosing a closest set of replicas to service a client request. Suboptimal replica choices due to dynamically changing network conditions result in reduced performance as a result of increased response latency. We present GeoPerf, a tool that tries to automate the process of systematically testing the performance of replica selection algorithms for geodistributed storage systems. Our key idea is to combine symbolic execution and lightweight modeling to generate a set of inputs that can expose weaknesses in replica selection. As part of our evaluation, we analyzed network round trip times between geographically distributed Amazon EC2 regions, and showed a significant number of daily changes in nearestK replica orders. We tested Cassandra and MongoDB using our tool, and found bugs in each of these systems. Finally, we use our collected Amazon EC2 latency traces to quantify the time lost due to these bugs. For example due to the bug in Cassandra, the median wasted time for 10% of all requests is above 50 ms.

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  • 177.
    Bogdanov, Kirill
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Peón-Quirós, Miguel
    Complutense University of Madrid.
    Maguire Jr., Gerald Q.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Kostić, Dejan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Toward Automated Testing of Geo-Distributed Replica Selection Algorithms2015Ingår i: Proceedings of the 2015 ACM Conference on Special Interest Group on Data Communication, Association for Computing Machinery (ACM), 2015, s. 89-90Konferensbidrag (Refereegranskat)
    Abstract [en]

    Many geo-distributed systems rely on a replica selection algorithms to communicate with the closest set of replicas.  Unfortunately, the bursty nature of the Internet traffic and ever changing network conditions present a problem in identifying the best choices of replicas. Suboptimal replica choices result in increased response latency and reduced system performance. In this work we present GeoPerf, a tool that tries to automate testing of geo-distributed replica selection algorithms. We used GeoPerf to test Cassandra and MongoDB, two popular data stores, and found bugs in each of these systems.

  • 178.
    Bogdanov, Kirill
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Reda, Waleed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab). Université catholique de Louvain.
    Kostic, Dejan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Maguire Jr., Gerald Q.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Canini, Marco
    KAUST.
    Kurma: Fast and Efficient Load Balancing for Geo-Distributed Storage Systems: Evaluation of Convergence and Scalability2018Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report provides an extended evaluation of Kurma, a practical implementation of a geo-distributed load balancer for backend storage systems. In this report we demonstrate the ability of distributed Kurma instances to accurately converge to the same solutions within 1% of the total datacenter’s capacity and the ability of Kurma to scale up to 8 datacenters using a single CPU core at each datacenter.

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  • 179.
    Bordenave, Charles
    et al.
    University of California, Berkeley, USA.
    McDonald, David
    University of Ottawa, Canada.
    Proutiere, Alexandre
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Random multi-access algorithms in networks with partial interaction: A mean field analysis2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider a network with a fixed number of links whose transmitters are saturated and access a channel using a random back-off algorithm. Some of the links may be hidden in the sense that they do not interfere with all other links but rather with a subset of the links. Using mean field techniques, we analyze a variety of random back-off algorithms by explicit calculating the throughput of the links in such networks. We apply our results to analyze the performance of the exponential back-off algorithm in networks with partial interaction. The results are striking and confirm experimental results. Hidden transmitters that fail to sense collisions with other links unfairly grab too much bandwidth at the expense of transmitters that comply with the back-off rules. We believe the model can be used to develop new algorithms realizing an adequate trade-off between fairness and efficiency.

  • 180.
    Bordenave, Charles
    et al.
    CNRS & Université de Toulouse.
    McDonald, David
    University of Ottawa, Canada.
    Proutiere, Alexandre
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Random multi-access algorithms in networks with partial interaction: A mean field analysis2010Ingår i: Networks and Heterogeneous Media, ISSN 1556-1801, E-ISSN 1556-181X, Vol. 5, nr 1, s. 31-62Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study an interacting particle system whose dynamics depends on an interacting random environment. As the number of particles grows large, the transition rate of the particles slows down (perhaps because they share a common resource of fixed capacity). The transition rate of a particle is determined by its state, by the empirical distribution of all the particles and by a rapidly varying environment. The transitions of the environment are determined by the empirical distribution of the particles. We prove the propagation of chaos on the path space of the particles and establish that the limiting trajectory of the empirical measure of the states of the particles satisfies a deterministic differential equation. This deterministic differential equation involves the time averages of the environment process.

    We apply the results on particle systems to understand the behavior of computer networks where users access a shared resource using a distributed random Medium Access Control (MAC) algorithm. MAC algorithms are used in all Local Area Network (LAN), and have been notoriously difficult to analyze. Our analysis allows us to provide simple and explicit expressions of the network performance under such algorithms.

  • 181.
    Borgström, Kristofer
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Multimedia Messaging Service Components for Web 2.02008Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Syftet med detta examensarbete är att förenkla utbyte (i båda riktningarna) av multimedia mellan mobiltelefoner och nätverksuppkopplade webbservrar. Lösningen som föreslås i denna rapport behandlar specifikt hur Multimedia Messaging Service (MMS)-meddelanden kan visas i en webbläsare via nätverksuppkopplade webbservrar och hur MMS-meddelanden kan komponeras grafiskt via ett webbinterface.

    Detta examensarbete är viktigt eftersom det för multimedia, i form av MMS-meddelanden, från isolering i telekommunikationsvärlden närmare en bred tillgänglighet via Internet. Denna övergång är viktig eftersom det är på Internet som multimedia görs tillgängligt för världen i dagens läge. Denna approach förbättrar upplevelsen för användare som vill dela med sig av innehåll genom sin telefon genom en hemsida. Den ökar också möjligheterna för mobiloperatörer att öka MMS-trafiken i sina nätverk.

    Lösningen är inte trivial eftersom det existerar ett antal komplexiteter i båda ändarna. Detta beror på att MMS-meddelanden som skapas i mobiltelefoner skiljer sig åt mellan såväl tillverkare som modeller. Dessutom används inte MMS-formatet (MMS SMIL) på Internet. Således måste en transformering till ett format som stöds av webbläsare genomföras. Detta examensarbete undersöker i vilken utsträckning denna transformering kan automatiseras helt och även hur MMS-meddelanden kan skapas via ett webbinterface.

    Resultaten visar att MMS-meddelanden framgångsrikt kan transformeras till HTML och bäddas in på en hemsida på ett sådant sätt att de upplevs som en del av hemsidan. Beroende på vilken typ av media som MMS-meddelandet innehåller, den aktuella webbläsarkonfigurationen och på vilka mediaspelar-plug-ins som finns tillgängliga, måste olika HTML genereras för att innehållet ska visas på ett bra sätt. Resultaten visar också att MMS-meddelanden kan skapas grafiskt, i realtid, direkt genom ett webbinterface med goda resultat.

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  • 182.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    A New Multi-Camera Approach For Lane Departure Warning2011Ingår i: ACIVS 2011: Proceedings of Acivs 2011, 2011, s. 58-69Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we present a new multi camera approach to Lane Departure Warning (LDW). Upon acquisition, the captured images are transformed to a bird's-eye view using a modified perspective removal transformation. Then, camera calibration is used to accurately determine the position of the two cameras relative to a reference point. Lane detection is performed on the front and rear camera images which are combined using data fusion. Finally, the distance between the vehicle and adjacent lane boundaries is determined allowing to perform LDW. The proposed system was tested on real world driving videos and shows good results when compared to ground truth.

  • 183.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    A Non Overlapping Camera Network: Calibration and Application Towards Lane Departure Warning2011Ingår i: IPCV 2011: Proceedings of the 15th International Conference on Image Processing, Computer Vision, and Pattern Recognition, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we present a new multi camera approach toLane DepartureWarning (LDW). First, a perspective removaltransformation is applied to the camera captured images toconvert them into bird’s-eye view images. Then, the positionof the two cameras relative to a reference point is accuratelydetermined using a new calibration technique. Lane detectionis performed on the front and rear camera images who resultsare combined using data fusion. Finally, LDW is implementedby determining the distance between the vehicle andadjacent lane boundaries. The proposed system was tested onreal world driving videos and shows good results when comparedto ground truth.

  • 184. Borkar, Amol
    et al.
    Hayes, Monson
    Smith, Mark T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    A Novel Lane Detection System With Efficient Ground Truth Generation2012Ingår i: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 13, nr 1, s. 365-374Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new night-time lane detection system and its accompanying framework are presented in this paper. The accompanying framework consists of an automated ground truth process and systematic storage of captured videos that will be used for training and testing. The proposed Advanced Lane Detector 2.0 (ALD 2.0) is an improvement over the ALD 1.0 or Layered Approach with integration of pixel remapping, outlier removal, and prediction with tracking. Additionally, a novel procedure to generate the ground truth data for lane marker locations is also proposed. The procedure consists of an original process called time slicing, which provides the user with unique visualization of the captured video and enables quick generation of ground truth information. Finally, the setup and implementation of a database hosting lane detection videos and standardized data sets for testing are also described. The ALD 2.0 is evaluated by means of the user-created annotations accompanying the videos. Finally, the planned improvements and remaining work are addressed.

  • 185.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Advanced Lane Detection Using Elliptical Lane Marker Grouping and Cascaded Templates2010Ingår i: ACIVS 2010: Proceedings of ACIVS 2010, 2010Konferensbidrag (Refereegranskat)
  • 186.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    An Efficient Method to Generate Ground Truth For Evaluating Lane Detection Systems2010Ingår i: 2010 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH, AND SIGNAL PROCESSING, 2010, s. 1090-1093Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this document, a new and efficient method to specify the ground truth locations of lane markers is presented. The method comprises of a novel process called Time-Slicing that provided the user with a unique visualization of the video. Coupled with automation via spline interpolation, the quick generation of necessary ground truth information is achieved. Videos recorded from a vehicle while driving on local city roads and highways are marked with ground truth information for use in testing. The performance of a variety of lane detection systems is compared to the ground truth and the error is computed for each system. Finally, quantitative analysis shows that the reference lane detection system presented in [1] produces the most accurate lane detections which is depicted by the smallest error.

  • 187.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Detecting Lane Markers in Complex Environments Using a Monocular Camera2011Ingår i: SPPRA 2011: Proceedings of the Eighth IASTED International Conference on Signal Processing, Pattern Recognition, and Applications, 2011Konferensbidrag (Refereegranskat)
  • 188.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Detecting Lane Markers in Complex Urban Environments2010Ingår i: 2010 IEEE 7th International Conference on Mobile Adhoc and Sensor Systems (MASS), 2010, s. 727-732Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we present a new methodology for detecting lane markers that is able to withstand many challenging situations like scattered shadows, illumination changes, and presence of neighboring vehicles to name a few. At first, the input image undergoes a perspective removal followed by a color space conversion. Then, the core elements consisting of template matching, lane region merging, and elliptical projections are explained. Finally, the developed system showed good results when tested on 15 minutes of real-world driving videos containing variations in illumination, traffic, and road surface conditions.

  • 189.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Lane Detection and Tracking Using a Layered Approach2009Ingår i: ADVANCED CONCEPTS FOR INTELLIGENT VISION SYSTEMS, PROCEEDINGS / [ed] BlancTalon, J; Philips, W; Popescu, D; Scheunders, P, 2009, s. 474-484Konferensbidrag (Refereegranskat)
    Abstract [en]

    A new night-time lane detection system that extends the idea of a Layered Approach [1] is presented in this document. The extension includes the incorporation of (1) inverse Perspective Mapping (IPM) to generate a bird's-eye view of the road surface, (2) application of Random Sample Consensus (RANSAC) to rid outliers from the data., and (3) Kalman filtering to smooth the output of the lane tracker. Videos of driving scenarios on local city roads and highways were used to test the new system. Quantitative analysis shows higher accuracy in detecting lane markers in comparison to other approaches.

  • 190.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Lane Detection Using Constraints of Parallel Lines2011Ingår i: ICCE 2011: Proceedings of the 29th IEEE International Conference on Consumer Electronics, 2011Konferensbidrag (Refereegranskat)
  • 191.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Polar Randomized Hough Transform For Lane Detection Using Loose Constraints of Parallel Lines2011Ingår i: 2011 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH, AND SIGNAL PROCESSING, 2011, s. 1037-1040Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we propose a new methodology for detecting lane markers that exploits the parallel nature of lane boundaries on the road. First, the input image is pre-processed and filtered to detect lane marker features. Then, using the Polar Randomized Hough Transform that is introduced in this paper, lines are fitted through the detected features and the orientation of each line is evaluated. By finding near parallel lines separated by a constraint specified distance, false signalling caused by artifacts in the image is greatly reduced. The proposed system was tested using a real world driving videos and showed good results despite the presence of neighboring vehicles, shadows, and irregularities on the road surface.

  • 192.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Robust Lane Detection and Tracking With Ransac and Kalman Filter2009Ingår i: 2009 16TH IEEE INTERNATIONAL CONFERENCE ON IMAGE PROCESSING, VOLS 1-6, 2009, s. 3225-3228Konferensbidrag (Refereegranskat)
    Abstract [en]

    In a previous paper, a simple approach to lane detection using the Hough transform and iterated matched filters was described [1]. This paper extends this work by incorporating an inverse perspective mapping to create a bird's-eye view of the road, applying random sample consensus to help eliminate outliers due to noise and artifacts in the road, and a Kalman filter to help smooth the output of the lane tracker.

  • 193.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Pankanti, Sharath
    IBM T.J. Watson Research Center.
    A Layered Approach to Robust Lane Detection at Night2009Ingår i: CIVVS 2009: 2009 IEEE WORKSHOP ON COMPUTATIONAL INTELLIGENCE IN VEHICLES AND VEHICULAR SYSTEMS, 2009, s. 51-57Konferensbidrag (Refereegranskat)
    Abstract [en]

    A layered approach is designed to address many of the real-world problems that an inexpensive lane detection system would encounter. A region of interest is first extracted from the image followed by an enhancement procedure to manipulate the shape of the lane markers. The extracted region is then converted to binary using an adaptive threshold. A model based line detection system hypothesizes lane position. Finally, an iterated matched filtering scheme estimates the final lane position. The developed system shows good performance when tested on real-world data that contains fluctuating illumination and a variety of traffic conditions.

  • 194.
    Bratu, Vlad-Ioan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Self-optimization of Antenna Tilt in Mobile Networks2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The increased complexity of mobile networks, the need to deliver high data rate services and the variation of mobile traffic put a high burden on operation and maintenance in terms of extra workload and additional costs . New approaches to network optimization and management should be taken into account to increase network performance and reduce operational costs. Antenna tilt is a powerful parameter for optimization of a mobile network. It has direct impact on shaping the boundary of the serving cell and hence on the coverage and interference parameters of the network. With the introduction of Remote Electrical Tilt (RET) antennas, tilt optimization can be used in the context of self-optimization. This work discusses how base station antenna tilt can be used as a self-optimization tool for load-balancing and presents a framework for a self-optimization process that can be integrated into existing and future mobile networks. Tests using real traffic data proved that the self-optimization process can be used to correctly identify congested cells. Both link level and system level simulations are performed to determine the impact of tilt adjustments on network performance. The results show that antenna tilt can be an effective tool to achieve load-balance between neighbouring cells and thus increase the Grade of Service (GoS). Furthermore, different tilt adjustment procedures are discussed each with it's advantages and disadvantages. It is concluded that antenna tilt can be successfully used for self-optimization purposes and possible limitations and issues are discussed.

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  • 195.
    Bratu, Vlad-Ioan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Beckman, Claes
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Antenna Tilt Load Balancing in Self-Organizing Networks2013Ingår i: International Journal of Research in Wireless Systems, ISSN 2320-3617, Vol. 2, nr 1, s. 21-26Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Base station antenna tilt is a powerful tuning parameter in traditional cellular network optimization. With theintroduction of Self-Organizing Networks (SON), this parameter may now be used also in the context of self-optimization.One envisioned scenario is load balancing (LB), where the coverage shaping properties of the antenna radiation pattern canbe used to control the cell borders. In this paper, a generalized framework for antenna tilt LB is presented and discussed. Inorder to assess the performance of antenna tilt as a tool for load balancing, simulations are performed to determine theeffect of tilt angle, vertical beamwidth and handover offset. The results show that there is a direct relation between theseparameters and the number of users that can be shifted towards neighboring cells. In conclusion, it is found that usingantennas with narrow vertical beamwidths together with small hand over offsets is an efficient way of performing loadbalancing but results also in high SIR variations.

  • 196.
    Bratu, Vlad-Ioan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Beckman, Claes
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Base station antenna tilt for load balancing2013Ingår i: 2013 7th European Conference on Antennas and Propagation (EUCAP), New York: IEEE , 2013, s. 2039-2043Konferensbidrag (Refereegranskat)
    Abstract [en]

    The coverage shaping and interference reduction ability of base station antenna tilt are important tools in cellular network optimization. Through tilt changes, the coverage area of a serving cell may also be either reduced or expanded. Therefore, antenna tilt has the potential to be used for load balancing purposes. This paper gives an overview of base station antennas performance and antenna tilt. Simulations are performed in order to determine the impact of tilt changes when used for load balancing. The results show that while antenna tilt load balancing can improve the Grade of Service (GoS) in a congested cell, it will also influence the user bit rates and total cell throughput for both the congested cell and the neighbors.

  • 197.
    Bratu, Vlad-Ioan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Beckman, Claes
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Base Station Antenna Tilt for Load Balancing and Potential use in Self-Optimizating Networks2013Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The coverage shaping and interference reduction ability of base station antenna tilt are important tools in cellular network optimization. Through tilt changes, the coverage area of a serving cell may also be either reduced or expanded. Therefore, antenna tilt has the potential to be used for load balancing purposes. With the introduction of Self-Organizing Networks (SON) in the mobile communications, this parameter may now be used also in the context of self-optimization, to address the common situation where traffic has an uneven spatial distribution between serving cells. This work gives an overview of base station antennas and antenna tilt. Simulations are performed in order to determine the impact of tilt changes when used for load balancing. The effect of tilt angle, vertical beam width and handover offset are analyzed also. The results show that there is a direct relation between these parameters and the number of users that can be shifted towards neighboring cells. In conclusion, it is found that using antennas with narrow vertical beam widths together with small hand over offsets is an efficient way of performing load balancing but results also in high SIR. Although antenna tilt load balancing can improve the Grade of Service (GoS) in a congested cell, it will also influence the user bit rates and total cell throughput for both the congested cell and the neighbors.

  • 198.
    Bremstedt Pedersen, Ivan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Andersson, Alfred
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    More than downloading: Visualization of data produced by sensors in a home environment2012Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    ”Home automation” syftar till ett system som låter användaren kontrollera och styra olika apparater i hemmet, ofta sker detta utifrån. Dessa apparater inkluderar, men är inte begränsade till ljusbrytare, termostater, termometrar, persienner eller klimatanläggningar. Potentialen för ett sådant system är enormt då antalet apparater som skulle kunna övervakas med endast minimal och billig extra hårdvara är stort. Många av dessa apparater kan dra nytta av att vara ansluten till ett system som gör det möjligt för ägaren att hantera och styra enheter i deras hem. Antalet apparater är därför mångdubbelt fler än antalet hem som är kopplade till systemet.

    Det finns flera system på marknaden som ger användaren ett sätt att övervaka och styra en hemmiljö, men dessa system är ofta låsta och stödjer bara specifika enheter. Genom att införa en öppen plattform för allmänheten som inte är bunden till något system, kan vi tillåta att fler enheter kan integreras i hemmet och bidra till ytterligare utveckling av smartare hem.

    Målet med detta projekt var att skapa en skalbar öppen plattform med möjlighet till asynkron uppdatering. Detta har gjorts genom att implementera flera logiska delar för att förse användaren med ett webbgränssnitt och för att tillåta oss hantera kommunikation och lagring av data. Alla dessa delar är sammanlänkade för att bilda ett system av servrar som hanterar alla bakgrundsprocesser. Denna avhandling diskuterar och presenterar implementeringar av alla dessa servrar, hur de genomförs, kommunicera med varandra, ger säkra anslutningar och hur de kan skala med ökad användning. I denna process diskuterar och presenterar vi de tekniker som använts, hur man använder dem och deras fördelar.

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  • 199.
    Bria, Aurelian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Cost-based resource management in hybrid cellular-broadcasting systems2005Ingår i: VTC2005-SPRING: 2005 IEEE 61ST VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5, PROCEEDINGS  , New York: IEEE , 2005, s. 3183-3187Konferensbidrag (Refereegranskat)
    Abstract [en]

    This article introduces a cost based framework for the resource management in hybrid cellular-broadcasting systems with adaptive data rate. The considered service is delivery of multimedia items to the cache memory of user terminals. The problem investigated here is the minimization of the delivery cost per item, given that we have at our disposal a cellular and a broadcasting system. The proposed solution is to search for optimum set of users that are assigned to the broadcasting radio access and the respective data rate for serving them. The simulations performed on a test bed show that it is possible to achieve even four to five times reduction in cost per item if we employ both infrastructures, compared to a simpler strategy that assumes the transmission to only one of them. This significant gain justify the need for centralized resource management of the cellular and broadcasting systems. We have identified also situations when this gain is not significant, hence centralized management is not needed. Both situations are possible in realistic environments.

  • 200.
    Bria, Aurelian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Future Hybrid Cellular-Broadcasting Systems for Multimedia Multicasting2006Ingår i: Second International Conference on Wireless and Mobile Communications, ICWMC 2006, IEEE , 2006, s. 18-Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper discusses hybrid cellular-broadcasting systems as an alternative for future delivery of wireless multimedia multicast services. A resource management framework is proposed, with the objective of minimizing the cost of multicasting transmissions. A comparison with traditional cellular and broadcasting systems is performed, showing the advantages of the hybrid solution under specific settings. Several implementation issues are investigated, as the number of broadcasting modulation and coding rates (MCR) and the importance of radio link monitoring. Dynamic control of the coverage of the broadcasting system by choosing from a pre-defined set of MCRs is shown to be the most important requirement for minimizing transmission cost. As the existing digital broadcasting technologies do not offer the possibility to dynamically change the MCR, several possibilities to overcome this are identified.

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