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  • 151.
    Beckman, Claes
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Lindmark, Björn
    Ahlberg, Mikael
    Dual Band Base Station Antenna Systems1998In: Broad Band Radio Access, Linköping, 1998, p. 69-74, article id 9Conference paper (Other academic)
    Abstract [en]

    An analysis of the possibilities of using dualband antennas in cellular radio is presented. Results from simultaneous measurements at 900 MHz and 1800 MHz are presented and analyzed. Based on the measured results, a dual polarized, dual band base station antenna has been designed. Such an antenna proveides the opportunity to replace a 4 antenna space diversity installation with a single antenna, thereby reducing costs and tower space.

  • 152.
    Beckman, Claes
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Lundgren, L.
    Roos, D.
    Dielectric-loaded circular ridge waveguide applicator for hyperthermia1988In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 1, no 6, p. 221-223Article in journal (Refereed)
    Abstract [en]

    An applicator for intracavitary hyperthermia treatment of cancer has been designed and tested. The applicator is a section of a dielectric-loaded circular ridge waveguide closed at both ends to form a transmission cavity. An aperture in the cavity wall can produce a directed heating of a tumor growing in the wall of a body cavity such as the vagina.

  • 153.
    Beckman, Claes
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Nilsson, Kristoffer
    The Technical and Economic Consequences of Protecting GSM-R in Sweden2016In: 2016 IEEE 83RD VEHICULAR TECHNOLOGY CONFERENCE (VTC SPRING), IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    A number of protection criteria were implemented by the Swedish regulator PTS in order to protect the GSM-R operations in Sweden. In order to protect the GSM-R receivers from interference and blocking, two different constraints were implemented: First, a limitation of the "out-of-band" emissions from the mobile operators' existing base stations operating in the 900MHz band was implemented. Secondly, a limitation of the aggregated power received over the railroad within the operator's spectrum allocation in the 900 band was added. In this study, the background of these protection criteria is presented and their technical and economic consequences estimated. Regarding "out-of-band" emissions from base stations, four alternative protection levels have been investigated: -92, -95, -98 and -107 dBm. It is found that in order to meet these requirements, safety distances of between 280 and 1200m need to be introduced, which means that between 1500 and 2700 base stations would be needed to be taken out of service. In order to avoid blocking, the received power over the embankment from each base station within the public GSM band would also be needed to be limited. The consequences of limiting the received power levels to either -10, -23 or -40 dBm were here investigated. Given the level of blocking protection, it is found that between 1085 and 2330 base stations within the vicinity of the railway track would be affected and possibly needed to be shut down To avoid causing interference, all operators - with the exception of Hi3G - may limit their "out-of-band" emissions by installing filters on the base stations. The cost of such installations is estimated at 50 000 SEK per base station. Depending on the protection level that is applied, the estimated total cost for the mobile operators is between 67 and 113 million SEK (about 12 million Euros). In order to protect the GSM-R receivers from blocking, some 3500 locomotives would need to be equipped with additional filters at a total cost of around 130 million SEK (about 14 million Euros).

  • 154.
    Beckman, Claes
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Thaung, Jörgen
    Sjöstrand, Johan
    In-vitro lens scatter measurements and glare testing1994Conference paper (Other academic)
  • 155.
    Bellagamba, Elisa
    et al.
    Ericsson Research.
    Andersson, Loa
    Ericsson AB.
    Sköldström, Pontus
    KTH, School of Information and Communication Technology (ICT), Communication Systems, 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 Ping2013Other (Other (popular science, discussion, etc.))
  • 156.
    Ben Slimane, Slimane
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Approximation to the Symmetric Capacity of Rayleigh Fading Channels with Multi-Level Signals2006In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 0, no 3, p. 129-131Article in journal (Refereed)
    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.

  • 157.
    Ben Slimane, Slimane
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Combined transmitter diversity and multi-level modulation techniques2006In: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. 39, no 2, p. 215-227Article in journal (Refereed)
    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.

  • 158.
    Ben Slimane, Slimane
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Combined Transmitter Diversity and Multi-Level Modulation Techniques2005Conference paper (Refereed)
    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.

  • 159.
    Ben Slimane, Slimane
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Reducing the Peak-to-Average Power Ratio of OFDM Signals Through Precoding2007In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 56, no 2, p. 686-695Article in journal (Refereed)
    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.

  • 160.
    Ben Slimane, Slimane
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Li, Xuesong
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Bo, Zhou
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Syed, Nauroze
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Dheim, Mohammad Abu
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Delay Optimization in Cooperative Relaying with Cyclic Delay Diversity2008In: 2008 IEEE International Conference On Communications, Proceedings: Vols 1-13, 2008, p. 3553-3557Conference paper (Refereed)
    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.

  • 161.
    Ben Slimane, Slimane
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Naik, Siddharth
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Toyserkani, Arash
    An Improved Cancellation Multiuser Detector for Narrowband Signals2005In: VTC 2005-Spring: 2005 IEEE 61st Vehicular Technology Conference, New York: IEEE , 2005, p. 973-977Conference paper (Refereed)
    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.

  • 162.
    Ben Slimane, Slimane
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Osseiran, Afif
    Ericsson Research, Ericsson AB, Stockholm, Sweden.
    Relay Communication with Delay Diversity for Future Communication Systems2006In: 2006 IEEE 64TH VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-6, New York: IEEE , 2006, p. 1-5Conference paper (Refereed)
    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.

  • 163.
    Ben Slimane, Slimane
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Zhou, Bo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Li, Xuesong
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Delay Optimization in Cooperative Relaying with Cyclic Delay Diversity2008In: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, p. 736818-Article in journal (Refereed)
    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.

  • 164. Bentley, F.
    et al.
    Tollmar, Konrad
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    The power of mobile notifications to increase wellbeing logging behavior2013In: CHI '13 Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, ACM Digital Library, 2013, p. 1095-1098Conference paper (Refereed)
    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.

  • 165. Bentley, F
    et al.
    Tollmar, Konrad
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Dernirdjian, D
    Koile, K
    Darrell, T
    Perceptive presence2003In: IEEE Computer Graphics and Applications, ISSN 0272-1716, E-ISSN 1558-1756, Vol. 23, p. 26-36Article in journal (Refereed)
    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.

  • 166. Bentley, Frank
    et al.
    Tollmar, Konrad
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Designing From Data: A Case Study From the Health Mashups Service2013In: Workshop on Informing Future Design via Large-Scale Research Methods and Big Data, 2013Conference paper (Refereed)
    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.

  • 167. Bentley, Frank
    et al.
    Tollmar, Konrad
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, 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 Change2013In: ACM Transactions on Computer-Human Interaction, ISSN 1073-0516, E-ISSN 1557-7325, Vol. 20, no 5, p. 30-Article in journal (Refereed)
    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.

  • 168.
    Berg, Miguel
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Markendahl, Jan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    A Concept for Public Access to Privately Operated Cooperating Local Access Points2005In: IEEE Vehicular Technology Conference, New York: IEEE , 2005, p. 2959-2963Conference paper (Refereed)
    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.

  • 169.
    Berggren, Fredrik
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    An error bound for moment matching methods of lognormal sum distributions2005In: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 6, no 6, p. 573-577Article in journal (Refereed)
    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.

  • 170.
    Berggren, Fredrik
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Spectral-effciency analysis in noncooperative interference environments2005In: 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, p. 741-745Conference paper (Refereed)
    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.

  • 171.
    Berggren, Fredrik
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Bria, Aurelian
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Veronesi, Riccardo
    Multi-radio resource management for ambient networks2005In: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, IEEE , 2005, p. 942-946Conference paper (Refereed)
    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.

  • 172.
    Berggren, Fredrik
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Litjens, Remco
    TNO ICT, The Netherlands.
    Performance analysis of access selection and transmit diversity in multi-access networks2006In: MOBICOM 2006, ACM , 2006, p. 251-261Conference paper (Refereed)
    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.

  • 173.
    Bhatia, Nupur
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Policy Management in Context-Aware Networks2007Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Ambient Network (AN) Project is part of the European Commission’s 6th Framework Programme and aims to enable cooperation between heterogeneous networks, using current and future wireless technologies, minimising the effort of mobile users to gain access to the services that they are interested in - irrespective of their location or the network they are currently using. Because of the highly mobile nature of users and a demand for instant and dynamic access to services, these networks have to be composed ‘on the fly’ without any pre-configurations.

    The use of context information in AN can remove the need for pre-configuration of networks, hence making them autonomic. However, a concern exists that the free and uncontrolled dissemination of context information could breech the privacy of the participants. It is extremely important to address these privacy issues in order to control who has access to what context information. This control can be achieved through the use of well defined policies. This creates a requirement for a framework in the ContextWare architecture for protecting context information.

    This masters thesis project is part of an effort to create a policy based infrastructure for authorisation of access to network context information within the AN. The thesis investigates, models, and designs an architecture for a policy management system based on OASIS XACML, that creates an extension to the architecture for management of context information in the AN. In addition to a policy management architecture within an AN, a policy management architecture for composing ANs is also created. To facilitate the transfer of requests and policies, the thesis creates a Policy Management Protocol. The designed architecture was then implemented to create a proof of concept.

    The designed architecture and protocol were evaluated by running tests on the prototype. The measurements from the tests are analysed and presented in this thesis. The analysis of the experimental data indicates that a policy management system is both feasible and practical. The results show that the delay overhead caused by introducing policy management in a distributed context provisioning system, ranges from 1.7% in a system without load to 6% in a worst case scenario. The throughput of the policy management system is 15 requests per second under load.

  • 174.
    Bhattacharya, Sujata
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Dedicated Channel Capacity of a WCDMA system with HSDPA Channels2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    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.

  • 175.
    Bin, Yang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Using Six Sigma Methodology to improve the performance of the Shipment Test2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Competition and lead-time pressure motivates us to find new and better ways of continuously improving the output of our work. The emphasis on improvement in both efficiency and quality has become more and more significant in daily activities. The performance of Ericsson’s AXE/APZ products during shipment test phase is one such activity and is the focus of this thesis project. One of the essential principles of shipment testing is to ensure that the test campaigns finish on time. Over the last several decades companies have spent large amounts of time and money on improving test quality and efficiency. Unfortunately, the results have not always been as good as expected. It seems that it is very difficult to improve shipment testing performance using traditional test management methods.

    Motorola introduced Six Sigma in 1986 and achieved 5.4 Sigma level which help them saved 2.2 Billion dollars during the first six years. From Statistic aspect, it means only 3.4 defects per million opportunities. The Six Sigma methodology has been applied as a management philosophy focused on improving efficiency and performance during the shipment test period.

    This thesis gives an introduction to the Six Sigma approach, including the concepts of Six Sigma, its history, development, and methodology. More specifically the author uses the Define, Measure, Analyze, Improve, and Control (DMAIC) approach to evaluate the performance of Ericsson’s AXE/APZ Shipment Testing. This project goal was defined: Compare with the performance of 08AXE shipment test which 87% of test campaigns (2.68 sigma level) were finished on time, 3 sigma level in 09AXE shipment test which means 93%of the test campaigns will be finished on time has to be achieved.  The thesis measured the 08AXE shipment test performance and analyzed the lead time of test campaigns, found the root causes such as poor documents quality from the legacy project, lack of test resources, no system impact analysis. The thesis also provided a set of proposals for improvements and control of the improved process in order to ensure sustainable improved performance results. Finally 93% test campaigns were finished on time in 09AXE and project goal was fulfilled.

  • 176.
    Blomgren, Mats
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Traffic estimation and traffic sensitive scheduling in mobile ad hoc networks2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    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.

  • 177.
    Bogdanov, Kirill
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Latency Dataset for the paper "The Nearest Replica Can Be Farther Than You Think"2015Data set
  • 178.
    Bogdanov, Kirill
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Reducing Long Tail Latencies in Geo-Distributed Systems2016Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Computing services are highly integrated into modern society. Millions of people rely on these services daily for communication, coordination, trading, and accessing to information. To meet high demands, many popular services are implemented and deployed as geo-distributed applications on top of third party virtualized cloud providers. However, the nature of such deployment provides variable performance characteristics. To deliver high quality of service, such systems strive to adapt to ever-changing conditions by monitoring changes in state and making run-time decisions, such as choosing server peering, replica placement, and quorum selection.

    In this thesis, we seek to improve the quality of run-time decisions made by geo-distributed systems. We attempt to achieve this through: (1) a better understanding of the underlying deployment conditions, (2) systematic and thorough testing of the decision logic implemented in these systems, and (3) by providing a clear view into the network and system states which allows these services to perform better-informed decisions.

    We performed a long-term cross datacenter latency measurement of the Amazon EC2 cloud provider. We used this data to quantify the variability of network conditions and demonstrated its impact on the performance of the systems deployed on top of this cloud provider.

    Next, we validate an application’s decision logic used in popular storage systems by examining replica selection algorithms. We introduce GeoPerf, a tool that uses symbolic execution and lightweight modeling to perform systematic testing of replica selection algorithms. We applied GeoPerf to test two popular storage systems and we found one bug in each.

    Then, using traceroute and one-way delay measurements across EC2, we demonstrated persistent correlation between network paths and network latency. We introduce EdgeVar, a tool that decouples routing and congestion based changes in network latency. By providing this additional information, we improved the quality of latency estimation, as well as increased the stability of network path selection.

    Finally, we introduce Tectonic, a tool that tracks an application’s requests and responses both at the user and kernel levels. In combination with EdgeVar, it provides a complete view of the delays associated with each processing stage of a request and response. Using Tectonic, we analyzed the impact of sharing CPUs in a virtualized environment and can infer the hypervisor’s scheduling policies. We argue for the importance of knowing these policies and propose to use them in applications’ decision making process.

  • 179.
    Bogdanov, Kirill
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Peón-Quirós, Miguel
    Complutense University of Madrid.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Kostic, Dejan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    The Nearest Replica Can Be Farther Than You Think2015In: Proceedings of the ACM Symposium on Cloud Computing 2015, Association for Computing Machinery (ACM), 2015, p. 16-29Conference paper (Refereed)
    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.

  • 180.
    Bogdanov, Kirill
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Peón-Quirós, Miguel
    Complutense University of Madrid.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Kostić, Dejan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Toward Automated Testing of Geo-Distributed Replica Selection Algorithms2015In: Proceedings of the 2015 ACM Conference on Special Interest Group on Data Communication, Association for Computing Machinery (ACM), 2015, p. 89-90Conference paper (Refereed)
    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.

  • 181.
    Bogdanov, Kirill
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Reda, Waleed
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab). Université catholique de Louvain.
    Kostic, Dejan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Canini, Marco
    KAUST.
    Kurma: Fast and Efficient Load Balancing for Geo-Distributed Storage Systems: Evaluation of Convergence and Scalability2018Report (Other academic)
    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.

  • 182.
    Bordenave, Charles
    et al.
    University of California, Berkeley, USA.
    McDonald, David
    University of Ottawa, Canada.
    Proutiere, Alexandre
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Random multi-access algorithms in networks with partial interaction: A mean field analysis2007Conference paper (Refereed)
    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.

  • 183.
    Bordenave, Charles
    et al.
    CNRS & Université de Toulouse.
    McDonald, David
    University of Ottawa, Canada.
    Proutiere, Alexandre
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Random multi-access algorithms in networks with partial interaction: A mean field analysis2010In: Networks and Heterogeneous Media, ISSN 1556-1801, E-ISSN 1556-181X, Vol. 5, no 1, p. 31-62Article in journal (Refereed)
    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.

  • 184.
    Borgström, Kristofer
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Multimedia Messaging Service Components for Web 2.02008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this master’s thesis is to simplify the exchange (in both directions) of multimedia content between mobile phones and network attached web servers. The solution proposed in this report specifically concerns displaying Multimedia Messaging Service (MMS) messages via a web browser connected to a network-attached web server and graphically authoring MMS messages via a web interface.

    This thesis project is important because it brings multimedia content, in the form of MMS messages, from isolation in the telecommunication world closer to wide availability via the Internet. This transition is very important as the Internet is where media is shared with the world today. This approach brings added value to end users who want to share content generated using their phone on a web site. It also provides added value to operators who want to increase the amount of MMS traffic in their networks.

    The solution is non-trivial because there are a number of complexities at both ends. This is because the MMS messages that are authored at mobile phones differ between both handset models and manufacturers. Moreover, the format used for MMS (MMS SMIL) is not widely used on the Internet, thus a transformation to an Internet browser supported format must be performed. The thesis examines to what extent this transformation can be completely automatic and how MMS messages can be authored through a web interface.

    The results show that MMS messages can be successfully transformed to HTML and embedded directly in web pages, thus providing a seamless experience for viewing MMS messages. Depending on the content of the MMS message in question, the current browser and which media player plug-ins are available, the generated HTML will be displayed differently. The results also show that MMS messages can be composed in real time* through a web interface with good results.

  • 185.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    A New Multi-Camera Approach For Lane Departure Warning2011In: ACIVS 2011: Proceedings of Acivs 2011, 2011, p. 58-69Conference paper (Refereed)
    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.

  • 186.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    A Non Overlapping Camera Network: Calibration and Application Towards Lane Departure Warning2011In: IPCV 2011: Proceedings of the 15th International Conference on Image Processing, Computer Vision, and Pattern Recognition, 2011Conference paper (Refereed)
    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.

  • 187. Borkar, Amol
    et al.
    Hayes, Monson
    Smith, Mark T.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    A Novel Lane Detection System With Efficient Ground Truth Generation2012In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 13, no 1, p. 365-374Article in journal (Refereed)
    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.

  • 188.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Advanced Lane Detection Using Elliptical Lane Marker Grouping and Cascaded Templates2010In: ACIVS 2010: Proceedings of ACIVS 2010, 2010Conference paper (Refereed)
  • 189.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    An Efficient Method to Generate Ground Truth For Evaluating Lane Detection Systems2010In: 2010 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH, AND SIGNAL PROCESSING, 2010, p. 1090-1093Conference paper (Refereed)
    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.

  • 190.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Detecting Lane Markers in Complex Environments Using a Monocular Camera2011In: SPPRA 2011: Proceedings of the Eighth IASTED International Conference on Signal Processing, Pattern Recognition, and Applications, 2011Conference paper (Refereed)
  • 191.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Detecting Lane Markers in Complex Urban Environments2010In: 2010 IEEE 7th International Conference on Mobile Adhoc and Sensor Systems (MASS), 2010, p. 727-732Conference paper (Refereed)
    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.

  • 192.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Lane Detection and Tracking Using a Layered Approach2009In: ADVANCED CONCEPTS FOR INTELLIGENT VISION SYSTEMS, PROCEEDINGS / [ed] BlancTalon, J; Philips, W; Popescu, D; Scheunders, P, 2009, p. 474-484Conference paper (Refereed)
    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.

  • 193.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Lane Detection Using Constraints of Parallel Lines2011In: ICCE 2011: Proceedings of the 29th IEEE International Conference on Consumer Electronics, 2011Conference paper (Refereed)
  • 194.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Polar Randomized Hough Transform For Lane Detection Using Loose Constraints of Parallel Lines2011In: 2011 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH, AND SIGNAL PROCESSING, 2011, p. 1037-1040Conference paper (Refereed)
    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.

  • 195.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Robust Lane Detection and Tracking With Ransac and Kalman Filter2009In: 2009 16TH IEEE INTERNATIONAL CONFERENCE ON IMAGE PROCESSING, VOLS 1-6, 2009, p. 3225-3228Conference paper (Refereed)
    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.

  • 196.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Pankanti, Sharath
    IBM T.J. Watson Research Center.
    A Layered Approach to Robust Lane Detection at Night2009In: CIVVS 2009: 2009 IEEE WORKSHOP ON COMPUTATIONAL INTELLIGENCE IN VEHICLES AND VEHICULAR SYSTEMS, 2009, p. 51-57Conference paper (Refereed)
    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.

  • 197.
    Bratu, Vlad-Ioan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Self-optimization of Antenna Tilt in Mobile Networks2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    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.

  • 198.
    Bratu, Vlad-Ioan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Antenna Tilt Load Balancing in Self-Organizing Networks2013In: International Journal of Research in Wireless Systems, ISSN 2320-3617, Vol. 2, no 1, p. 21-26Article in journal (Other academic)
    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.

  • 199.
    Bratu, Vlad-Ioan
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Base station antenna tilt for load balancing2013In: 2013 7th European Conference on Antennas and Propagation (EUCAP), New York: IEEE , 2013, p. 2039-2043Conference paper (Refereed)
    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.

  • 200.
    Bratu, Vlad-Ioan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Base Station Antenna Tilt for Load Balancing and Potential use in Self-Optimizating Networks2013Conference paper (Other academic)
    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.

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