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  • 301. Dixit, A.
    et al.
    Mahloo, Mozhgan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Lannoo, B.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Colle, D.
    Pickavet, M.
    Protection strategies for Next Generation Passive Optical Networks -22014In: 2014 International Conference on Optical Network Design and Modeling, 2014, 13-18 p.Conference paper (Refereed)
    Abstract [en]

    Next Generation Passive Optical Networks-2 (NG-PON2) are being considered to upgrade the current PON technology to meet the ever increasing bandwidth requirements of the end users while optimizing the network operators’ investment. Reliability performance of NG-PON2 is very important due to the extended reach and, consequently, large number of served customers per PON segment. On the other hand, the use of more complex and hence more failure prone components than in the current PON systems may degrade reliability performance of the network. Thus designing reliable NG-PON2 architectures is of a paramount importance. Moreover, for appropriately evaluating network reliability performance, new models are required. For example, the commonly used reliability parameter, i.e., connection availability, defined as the percentage of time for which a connection remains operable, doesn’t reflect the network wide reliability performance. The network operators are often more concerned about a single failure affecting a large number of customers than many uncorrelated failures disconnecting fewer customers while leading to the same average failure time. With this view, we introduce a new parameter for reliability performance evaluation, referred to as the failure impact. In this paper, we propose several reliable architectures for two important NG-PON2 candidates: wavelength division multiplexed (WDM) PON and time and wavelength division multiplexed (TWDM) PON. Furthermore, we evaluate protection coverage, availability, failure impact and cost of the proposed schemes in order to identify the most efficient protection architecture.

  • 302.
    Do, Tan Tai
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Oechtering, Tobias J.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Optimal Transmission for the MIMO Bidirectional Broadcast Channel in the Wideband Regime2013In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 61, no 20, 5103-5116 p.Article in journal (Refereed)
    Abstract [en]

    This paper considers a transmit strategy for an AWGN MIMO bidirectional broadcast channel in the wideband regime. In order to characterize the boundaries of the wideband capacity and energy per bit regions, the transmit strategy at the relay is designed to maximize the weighted wideband rate sum. A closed form of the optimal transmit covariance matrix is derived, which shows that a single beam transmit strategy is optimal. The transmit strategies for some special cases are also analyzed. The fairness versus energy efficiency tradeoff is then discussed. In addition, an extension to multipair MIMO bidirectional broadcast channel is studied in which we show that serving a certain pair with full power is optimal in the sense of maximizing the achievable weighted wideband rate sum. Finally, a discussion on the conjecture of the minimum energy per bit for multi-pair systems is provided.

  • 303.
    Do, Tan Tai
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Oechtering, Tobias
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Achievable energy per bit for the multi-pair MIMO bidirectional broadcast channel2012In: European Wireless, 2012. EW. 18th European Wireless Conference, 2012Conference paper (Refereed)
    Abstract [en]

    This paper presents a transmit strategy for the AWGN multi-pair MIMO bidirectional broadcast channels in the wideband regime. An achievable wideband rate region and an achievable energy per bit region are provided. The transmit covariance matrix at the relay has been designed in order to maximize the wideband weighted rate sum. A closed form of the optimal matrix is derived, which shows that a single beam transmit strategy is optimal. In addition, an energy efficiency versus fairness analysis is considered. Lastly, some discussions on the minimum energy per bit are given.

  • 304.
    Do, Tan Tai
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Oechtering, Tobias
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Optimal transmission for the MIMO bidirectional broadcast channel in the wideband regime2011In: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC, 2011, 356-360 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents an optimal transmit strategy for multiple antennas bidirectional broadcast channels in the wideband regime. The transmit covariance matrix at the relay has been designed in order to maximize the wideband weighted sum rate. A closed form of the optimal matrix is derived, which shows that a single beam transmit strategy is optimal. The transmit strategies for some special cases, the wideband capacity region, and the minimum energy per bit versus fairness issues are also discussed.

  • 305.
    Do, Tan Tai
    et al.
    Electronic & Radio Engineering, KyungHee University.
    Park, Jae Cheol
    Electronic & Radio Engineering, KyungHee University.
    Song, Iickho
    Kim, Yun Hee
    Electronic & Radio Engineering, KyungHee University.
    Cross-layer design of multiple antenna multicast combining AMC with truncated HARQ2010In: Annales des télécommunications, ISSN 0003-4347, E-ISSN 1958-9395, Vol. 65, no 11-12, 803-815 p.Article in journal (Refereed)
    Abstract [en]

    Combining adaptive modulation and coding with truncated hybrid automatic request, this paper presents a cross-layer design for multiple antenna multicast over a common radio channel. In the design, the modulation and coding scheme of a multicast packet is selected based on the minimum signal-to-noise ratio (SNR) in the multicast group in such a way that the constraint on the packet loss rate is satisfied for all users in the group. A general expression for the throughput of the proposed design is derived in frequency-flat fading channel environment and specific results in Rayleigh, Nakagami, and Rician fading channels are provided. It is shown that the proposed multicast design provides a significant throughput gain compared to the unicast counterpart, in particular, in the mid- to high SNR region. It is also shown that a larger value of the diversity order, Nakagami parameter, and Rician factor is more beneficial to multicast than to unicast.

  • 306.
    Do, Tan Tai
    et al.
    Electronics & Radio Engineering Department, KyungHee University.
    Park, Jae Chul
    Electronics & Radio Engineering Department, KyungHee University.
    Kim, Yun Hee
    Electronics & Radio Engineering Department, KyungHee University.
    Cooperative diversity for wireless multicast transmission with truncated ARQ2009In: 2009 9th International Symposium on Communications and Information Technology, ISCIT 2009, 2009, 947-948 p.Conference paper (Refereed)
    Abstract [en]

    This paper proposes a cooperative diversity protocol with truncated automatic repeat request (ARQ) for multicast transmission. The proposed method employs SNR threshold-based selective relaying for distributed space time block coding for retransmission. Numerical results will show that the proposed method with optimal SNR threshold improves the error and throughput performance remarkably.

  • 307.
    Do, Tan Tai
    et al.
    Electronics & Radio Engineering Department, KyungHee University.
    Park, Jae Chul
    Electronics & Radio Engineering Department, KyungHee University.
    Kim, Yun Hee
    Electronics & Radio Engineering Department, KyungHee University.
    Song, Iickho
    Cross-Layer Design of Adaptive Wireless Multicast Transmission with Truncated HARQ2009In: 2009 IEEE VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5, 2009, 1879-1883 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a cross-layer design of adaptive modulation and coding (AMC) with truncated hybrid automatic repeat request (HARQ) for one-to-many multicast transmission, in order to increase the spectral efficiency under the quality-of-service (QoS) constraints. For adaptive transmission over the channel common to the multicast group users, the AMC mode is chosen with the minimum SNR among the users to guarantee the target performance of all users. In the meanwhile, the minimum SNR required to support an AMC mode is aggressively designed by allowing retransmission with HARQ schemes. For the proposed design, we derive the average packet error rate, average number of transmission, and spectral efficiency and provide the performance numerically obtained. Numerical results show that the cross-layer design for multicast provides a significant performance gain at a small number of retransmissions as in unicast. In particular, it is observed that AMC design with HARQ is more beneficial in the low SNR region where multicast performs worse than unicast

  • 308. Dombrowski, Christian
    et al.
    Gross, James
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Reducing Outage Probability over Wireless Channels Under Hard Real-Time Constraints2011Conference paper (Refereed)
  • 309. Dombrowski, Christian
    et al.
    Junges, Sebastian
    Katoen, Joost Pieter
    Gross, James
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Model-Checking Assisted Protocol Design for Ultra-Reliable Low-Latency Wireless Networks2016Conference paper (Refereed)
    Abstract [en]

    Recently, the wireless networking community is getting more and more interested in novel protocol designs for safety-critical applications. These new applications come with unprecedented latency and reliability constraints which poses many open challenges. A particularly important one relates to the question how to develop such systems. Traditionally, development of wireless systems has mainly relied on simulations to identify viable architectures. However, in this case the drawbacks of simulations – in particular increasing run-times – rule out its application. Instead, in this paper we propose to use probabilistic model checking, a formal model-based verification technique, to evaluate different system variants during the design phase. Apart from allowing evaluations and therefore design iterations with much smaller periods, probabilistic model checking provides bounds on the reliability of the considered design choices. We demonstrate these salient features with respect to the novel EchoRing protocol, which is a token-based system designed for safety-critical industrial applications. Several mechanisms for dealing with a token loss are modeled and evaluated through probabilistic model checking, showing its potential as suitable evaluation tool for such novel wireless protocols. In particular, we show by probabilistic model checking that wireless tokenpassing systems can benefit tremendously from the considered fault-tolerant methods. The obtained performance guarantees for the different mechanisms even provide reasonable bounds for experimental results obtained from a real-world implementation.

  • 310. Dombrowski, Christian
    et al.
    Petreska, Neda
    Görtzen, Simon
    Schmeink, Anke
    Gross, James
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Energy-efficient multi-hop transmission for machine-to-machine communications2013In: 2013 11th International Symposium and Workshops on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks, WiOpt 2013, 2013, 341-348 p.Conference paper (Refereed)
    Abstract [en]

    Emerging machine-to-machine communication scenarios are envisioned to deal with more stringent quality-of-service demands. This relates mainly to outage and latency requirements, which are for example for safety-critical messages quite different than for traditional applications. On the other hand, it is widely accepted that machine-to-machine communication systems need to be energy-efficient because of the widespread use of battery-powered devices, but also due to their huge deployment numbers. In this paper, we address these issues with respect to multi-hop transmissions. Specifically, we deal with minimizing the consumed energy of transmitting a packet with end-to-end outage and latency requirements. We account for the cases in which the system can utilize solely average channel state information, or in addition obtain and profit from instantaneous channel state information. The developed solution is based on convex optimization. It is shown numerically that despite accounting for the energy consumption of acquiring instantaneous channel state information, especially as the outage and latency requirements become tough, it is by up to 100 times more energy efficient to convey a packet with instantaneous than with average channel state information.

  • 311.
    Dominique, Torkel
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Push services based on SIP2001Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Session Initiation Protocol (SIP) is the most potential protocol for Real Time IP communication, for example IP telephony, today. This M.Sc. thesis project aim to create a solution for information providers to push information to a large numbers of users, using the SIP protocol and a number of proposed extensions to SIP. The system will be built on a SUBSCRIBE/NOTIFY mechanism similar to the one used for instant messages and presence. This system can be used for companies to build information push services (i.e. News, Traffic information, etc.) or to push commercial advertisement.

    The reason to use the SIP protocol for this is that SIP has already solved the addressing problem by introducing email-like addresses that follow the user when he moves around in the system. This is perfect for the push service that wants to reach the user wherever he is.

  • 312.
    Domínguez Sánchez, Carlos
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Speaker Recognition in a handheld computer2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Handheld computers are widely used, be it a mobile phone, personal digital assistant (PDA), or a media player. Although these devices are personal, often a small set of persons can use a given device, for example a group of friends or a family.

    The most natural way to communicate for most humans is through speech. Therefore a natural way for these devices to know who is using them is for the device to listen to the user’s speech, i.e., to recognize the speaker based upon their speech.

    This project exploits the microphone built into most of these devices and asks whether it is possible to develop an effective speaker recognition system which can operate within the limited resources of these devices (as compared to a desktop PC). The goal of this speaker recognition is to distinguish between the small set of people that could share a handheld device and those outside of this small set. Therefore the criteria is that the device should work for any of the members of this small set and not work for anyone outside of this small set. Furthermore, within this small set the device should recognize which specific person within this small group is using it.

    An application for a Windows Mobile PDA has been developed using C++. This application and its underlying theoretical concepts, as well as parts of the code and the results obtained (in terms of accuracy rate and performance) are presented in this thesis. The experiments conducted within this research indicate that it is feasible to recognize the user based upon their speech is within a small group and further more to identify which member of the group is the user. This has great potential for automatically configuring devices within a home or office environment for the specific user. Potentially all a user needs to do is speak within hearing range of the device to identify themselves to the device. The device in turn can configure itself for this user. 

  • 313. Dordlofva, Bengt
    et al.
    Karlsson, Magnus
    Larsson, Per
    Larsson, Thomas
    Zetterberg, Per
    KTH.
    Arrangement for Frequency Planning in Cellular Systems1999Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    The invention relates to an arrangement for frequency planning in cellular systems using a mix of wide and narrow antenna beams. The arrangement employs a dual frequency reuse for the respective wide and narrow antenna beams. According to the invention, a first frequency group is allocated to a cluster with a reuse distance sufficient for narrow beam channels and a second frequency group is allocated to a larger cluster with a reuse distance sufficent for wide beam channels. The second frequency group is a subdivision of and contained in the first frequency group. The second frequency group is the only frequency group available for wide beam channels, while all the frequencies of the two groups are available for the narrow beams channels. Generally, the wide beams are used for control channels and the narrow beams are used for traffic channels. A frequency planning in accordance with the invention makes it possible to use narrow beam traffic channels more efficiently compared to known state of the art methods which results in improved trunking efficiency.

  • 314.
    Dreier, Dennis
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Silveira, Semida
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Smart City Concepts in Curitiba - innovation for sustainable mobility and energy efficiency: Project NEWSLETTER, January 20162016Other (Other (popular science, discussion, etc.))
  • 315.
    Dreier, Dennis
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Silveira, Semida
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Smart City Concepts in Curitiba - innovation for sustainable mobility and energy efficiency: Project NEWSLETTER, November 20162016Other (Other (popular science, discussion, etc.))
  • 316.
    Drugge, Fredrik
    KTH, Superseded Departments, Teleinformatics.
    Design of a Multimedia Help System in UNIX1995Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The department G at EUA has developed a project management method and tool, PROPS-N. The PROPS-N is an on-line system built in FrameMaker that operates in a SUN/UNIX environment.

    This master's thesis attends to the problem of how to organize and implement a prototype of a multimedia help system for PROPS-N, with the help of the commercial tools available today.

    I have searched for multimedia authoring tools and screen activity recorders, that can be used for the development of the prototype. I have evaluated the multimedia authoring tools IconAuthor 6.0, Gain Momentum 3.1 and MetaCard 1.4. I have also evaluated the screen activity recorders ScreenPlay 2.3 and XRecorder 1.101.

    Some aspects that help you create usable help systems, and ensure learning, are also shown in this thesis. I have used a Multimedia Design and Development Methodology, with the tools ScreenPlay and MetaCard for the implementation of the prototype.

    This thesis also includes suggestions for future development of the prototype.

  • 317. Du, G.
    et al.
    Li, M.
    Lu, Zhonghai
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Gao, M.
    Wang, C.
    An analytical model for worst-case reorder buffer size of multi-path minimal routing NoCs2014In: Proceedings - 2014 8th IEEE/ACM International Symposium on Networks-on-Chip, NoCS 2014, IEEE , 2014, 49-56 p.Conference paper (Refereed)
    Abstract [en]

    Reorder buffers are often needed in multi-path routing networks-on-chips (NoCs) to guarantee in-order packet delivery. However, the buffer sizes are usually over-dimensioned, due to lack of worst-case analysis, leading to unnecessary larger area overhead. Based on network calculus, we propose an analysis framework for the worst-case reorder buffer size in multi-path minimal routing NoCs. Experiments with synthetic traffic and an industry case show that our method can effectively explore the traffic splitting space, as well as the mapping effects in terms of reorder buffer size with a maximum improvement of 36.50%.

  • 318.
    Du, Jinfeng
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS.
    Signell, Svante
    KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS.
    Classic OFDM Systems and Pulse Shaping OFDM/OQAM Systems2007Report (Other academic)
    Abstract [en]

    In this report, we provide a comparative study of state-of-the-art in Orthogonal Frequency Division Multiplexing (OFDM) techniques with orthonormal analysis and synthesis basis. Two main categories, OFDM/QAM which adopts base-band Quadrature Amplitude Modulation (QAM) and rectangular pulse shape, and OFDM/OQAM which uses baseband offset QAM and various pulse shapes, are intensively reviewed. OFDM/QAM can provide high data rate communication and effectively remove intersymbol interference (ISI) by employing guard interval, which costs a loss of spectral efficiency and increases power consumption. Meanwhile it remains very sensitive to frequency offset which causes inter-carrier interference (ICI). In order to achieve better spectral efficiency and reducing combined ISI/ICI, OFDM/OQAM using well designed pulses with proper Time Frequency Localization (TFL) is of great interest. Various prototype functions, such as rectangular, half cosine, Isotropic Orthogonal Transfer Algorithm (IOTA) function and Extended Gaussian Functions (EGF) are discussed and simulation results are provided to illustrate the TFL properties by the ambiguity function and the interference function.

  • 319.
    Du, Manxing
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Analyzing Caching Gain in Small Geographical Areas in IP Access Networks2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Since its emergence, user generated content (UGC) has become the driving force in the growth of Internet traffic. As one of the most successful and popular UGC systems, YouTube contributes a great share of Internet traffic volume and has attracted a lot of academic interest. The continuously increasing amount of IP traffic motivates the need for better network design, more efficient content distribution mechanisms, and more sustainable system development. Web caching is one of the widely used techniques to reduce the inter Internet Service Provider (ISP) traffic. Web caching is considered an important part in the design of a content distribution infrastructure.

    This master’s thesis utilizes a one month trace of YouTube traffic in two residential networks in Sweden. Based upon a systematic and in-depth measurement we focus on analyzing the geographic locality of traffic patterns within small areas for these two networks. We summarize the YouTube traffic characteristics and user replay patterns, and then discuss why caching can be useful for YouTube-like systems.

    We present the optimal caching gain on a per area basis and also divide users into two groups: PC and mobile device users to show the caching gain for these two groups. Overall, an infinite capacity proxy cache for each small area could reduce the YouTube streaming data traffic by 30% to 45%. The result presented in this paper help us to understand YouTube traffic and user behaviors and provides valuable information for the ISPs to enable them to design more efficient caching mechanisms.

    When this work began we thought that a reduction of backhaul traffic (especially for mobile operators) may delay the need to make investments in upgrading their network capacity. However, an important conclusion from this thesis project is that the cache efficiency depends on the terminal type. For mobile terminals (smart phones, iPads, etc) a terminal cache solution is found to be the most efficient. For PCs in fixed networks, a network cache would be more efficient. It should be noted that the mobile terminals covered in the project are connected through home Wi-Fi, so further research is needed in order to draw definite conclusions for caching solutions for cellular networks.

  • 320. Du, R.
    et al.
    Fischione, C.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Joint node deployment and wireless energy transfer scheduling for immortal sensor networks2017In: 2017 15th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, WiOpt 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, 7959918Conference paper (Refereed)
    Abstract [en]

    The lifetime of a wireless sensor network (WSN) is limited by the lifetime of the individual sensor nodes. A promising technique to extend the lifetime of the nodes is wireless energy transfer. The WSN lifetime can also be extended by exploiting the redundancy in the nodes' deployment, which allows the implementation of duty-cycling mechanisms. In this paper, the joint problem of optimal sensor node deployment and WET scheduling is investigated. Such a problem is formulated as an integer optimization whose solution is challenging due to the binary decision variables and non-linear constraints. To solve the problem, an approach based on two steps is proposed. First, the necessary condition for which the WSN is immortal is established. Based on this result, an algorithm to solve the node deployment problem is developed. Then, the optimal WET scheduling is given by a scheduling algorithm. The WSN is shown to be immortal from a networking point of view, given the optimal deployment and WET scheduling. Theoretical results show that the proposed algorithm achieves the optimal node deployment in terms of the number of deployed nodes. In the simulation, it is shown that the proposed algorithm reduces significantly the number of nodes to deploy compared to a random-based approach. The results also suggest that, under such deployment, the optimal scheduling and WET can make WSNs immortal.

  • 321.
    Du, Rong
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Gkatzikis, Lazaros
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Xiag, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Energy Efficient Sensor Activation for Water Distribution Networks Based on Compressive Sensing2015In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 33, no 12, 2997-3010 p.Article in journal (Refereed)
    Abstract [en]

    The recent development of low cost wireless sensors enables novel internet-of-things (IoT) applications, such as the monitoring of water distribution networks. In such scenarios, the lifetime of the wireless sensor network (WSN) is a major concern, given that sensor node replacement is generally inconvenient and costly. In this paper, a compressive sensing-based scheduling scheme is proposed that conserves energy by activating only a small subset of sensor nodes in each timeslot to sense and transmit. Compressive sensing introduces a cardinality constraint that makes the scheduling optimization problem particularly challenging. Taking advantage of the network topology imposed by the IoT water monitoring scenario, the scheduling problem is decomposed into simpler subproblems, and a dynamic-programming-based solution method is proposed. Based on the proposed method, a solution algorithm is derived, whose complexity and energy-wise performance are investigated. The complexity of the proposed algorithm is characterized and its performance is evaluated numerically via an IoT emulator of water distribution networks. The analytical and numerical results show that the proposed algorithm outperforms state-of-the-art approaches in terms of energy consumption, network lifetime, and robustness to sensor node failures. It is argued that the derived solution approach is general and it can be potentially applied to more IoT scenarios such as WSN scheduling in smart cities and intelligent transport systems.

  • 322.
    Du, Rong
    et al.
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Ozcelikkale, A.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Optimal energy beamforming and data routing for immortal wireless sensor networks2017In: 2017 IEEE International Conference on Communications, ICC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, 7996326Conference paper (Refereed)
    Abstract [en]

    Wireless sensor networks (WSNs) consist of energy limited sensor nodes, which limits the network lifetime. Such a lifetime can be prolonged by employing the emerging technology of wireless energy transfer (WET). In WET systems, the sensor nodes can harvest wireless energy from wireless charger, which can use energy beamforming to improve the efficiency. In this paper, a scenario where dedicated wireless chargers with multiple antennas use energy beamforming to charge sensor nodes is considered. The energy beamforming is coupled with the energy consumption of sensor nodes in terms of data routing, which is one novelty of the paper. The energy beamforming and the data routing are jointly optimized by a non-convex optimization problem. This problem is transformed into a semidefinite optimization problem, for which strong duality is proved, and thus the optimal solution exists. It is shown that the optimal solution of the semi-definite programming problem allows to derive the optimal solution of the original problem. The analytical and numerical results show that optimal energy beamforming gives two times better monitoring performance than that of WET without using energy beamforming.

  • 323.
    Dubroca, Sabrina Marjorie
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Cross-Layer optimization in a satellite communication network2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis aims to improve a satellite communication network which carries both data streams and Voice over IP (VoIP) communication sessions with resource reservation. The resource reservations are made using the standard protocols for Traffic Engineering: MPLS-TE and RSVP-TE. The goal of this thesis project is to optimize the number of concurrent VoIP calls that can be made, in order to use the available bandwidth while maintaining a guaranteed Quality of Service (QoS) level, which is not possible in the existing system.

    This thesis proposes and evaluates a solution to this optimization problem in the specific context of a satellite modem system that was developed by Thales Communications. This optimization improves the system's ability to carry VoIP communications through better use of the available transmission resources. A solution to this problem would also increase the  exibility in bandwidth allocation within the modem system, and could provide a framework for future development.

    The proposed solution allows all of the reservable bandwidth to be used.  The amount of reservable bandwidth must be at least a little lower than the channel's available bandwidth in order to avoid congestion. Some areas of future work are proposed.

  • 324.
    Dubrova, Elena
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronics and Embedded Systems.
    Hell, Martin
    Lund University, Sweden.
    Espresso: A stream cipher for 5G wireless communication systems2017In: Cryptography and Communications, ISSN 1936-2447, E-ISSN 1936-2455, Vol. 9, no 2, 273-289 p.Article in journal (Refereed)
    Abstract [en]

    The demand for more efficient ciphers is a likely to sharpen with new generation of products and applications. Previous cipher designs typically focused on optimizing only one of the two parameters - hardware size or speed, for a given security level. In this paper, we present a methodology for designing a class of stream ciphers which takes into account both parameters simultaneously. We combine the advantage of the Galois configuration of NLFSRs, short propagation delay, with the advantage of the Fibonacci configuration of NLFSRs, which can be analyzed formally. According to our analysis, the presented stream cipher Espresso is the fastest among the ciphers below 1500 GE, including Grain-128 and Trivium.

  • 325.
    Dubrova, Elena
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronics and Embedded Systems.
    Näslund, Mats
    Ericsson AB.
    Selander, Göran
    Ericsson AB.
    CRC-Based Message Authentication for 5G Mobile Technology2015In: Proceedings of 2015 IEEE Trustcom/BigDataSE/ISPA, IEEE , 2015, Vol. 1, 1186-1191 p.Conference paper (Refereed)
    Abstract [en]

    Our society greatly depends on mobile technologies. As wirelessly connected devices take over the control of the electricity in our homes, the water we drink and the transportation we use, it becomes increasingly important to guarantee the security of interactions of all players involved in a network. Apart from the high security needs, 5G will require utmost efficiency in the use of bandwidth and energy. In this paper, we show how to make the type of CRC checksum used in current LTE standards cryptographically secure with minimum extra resources. We present a new CRC-based message authentication method and provide a quantitative analysis of the achieved security as a function of message and CRC sizes. The presented method retains most of the implementation simplicity of the traditional CRC except that the LFSR implementing the encoding and decoding is required to have re-programmable connections. Similarly to previously proposed cryptographically secure CRCs, the presented CRC enables combining the detection of random and malicious errors without increasing bandwidth. Its main advantage is the ability to detect all double-bit errors in a message, which is of special importance for systems using Turbo codes, including LTE.

  • 326.
    Dwivedi, Satyam
    Electrical Communication Engineering Departme, Indian Institute of Science.
    Low Power Receiver Architecture and Algorithms for Low Data Rate Wireless Personal Area Networks2011Doctoral thesis, comprehensive summary (Other academic)
  • 327.
    Dwivedi, Satyam
    et al.
    Department of Electrical Communication Engineering, Indian Institute of Science.
    Amrutur, Bharadwaj
    Bhat, Navakant
    Optimizing resolution of signals in a low-IF receiver2007In: ISSCS 2007: International Symposium on Signals, Circuits and Systems, Vols 1 and 2, 2007, 349-352 p.Conference paper (Refereed)
    Abstract [en]

    The resolution of the digital signal path has a crucial impact on the design, performance and the power dissipation of the radio receiver data path, downstream from the ADC. The ADC quantization noise has been traditionally included with the Front End receiver noise in calculating the SNR as well as BER for the receiver. Using the IEEE 802.15.4 as an example, we show that this approach leads to an over-design for the ADC and the digital signal path, resulting in larger power. More accurate specifications for the front-end design can be obtained by making SNRreq a function of signal resolutions. We show that lower resolution signals provide adequate performance and quantization noise alone does not produce any bit-error. We find that a tight bandpass filter preceding the ADC can relax the resolution requirement and a I-bit ADC degrades SNR by only 1.35 dB compared to 8-bit ADC. Signal resolution has a larger impact on the synchronization and a 1-bit ADC costs about 5 dB in SNR to maintain the same level of performance as a 8-bit ADC.

  • 328.
    Dwivedi, Satyam
    et al.
    Microelectronics Lab., ECE Dept., Indian Institute of Science.
    Amrutur, Bharadwaj
    BHat, Navakant
    Power Scalable Digital Baseband Architecture for IEEE 802.15.42011In: 24th International Conference on VLSI Design, VLSI Design 2011, Held Jointly with 10th International Conference on Embedded Systems, 2011, 30-35 p.Conference paper (Refereed)
    Abstract [en]

    We propose a power scalable digital baseband for a low-IF receiver for IEEE 802.15.4-2006. The digital section's sampling frequency and bit width are used as knobs to reduce the power under favorable signal and interference scenarios, thus recovering the design margins introduced to handle worst case conditions. We propose tuning of these knobs based on measurements of Signal and the interference levels. We show that in a 0.13u CMOS technology, for an adaptive digital baseband section of the receiver designed to meet the 802.15.4 standard specification, power saving can be up to nearly 85% (0.49mW against 3.3mW) in favorable interference and signal conditions.

  • 329. Dwivedi, Satyam
    et al.
    Vedavathy, T.S.
    Shivaprasad, A.P.
    A divide-and-conquer approach with adaptive modulation to CDMA systems2003Conference paper (Refereed)
  • 330.
    Dzaferagic, Samir
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Secure Session Mobility for VoIP2008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    High data rate wireless packet data networks have made real-time IP based services available through mobile devices. At the same time, differences in the characteristics of radio technologies (802.11/WiFi and 3G networks) make seamless handoff across heterogeneous wireless networks difficult. Despite this, many believe that the ultimate goal of next generation networks (often referred to as the fourth generation) is to allow convergence of such dissimilar heterogeneous networks. Supporting voice over Internet Protocol in next-generation wireless systems is thought by some to require support for mobility and quality of service features. Currently a mobile node can experience interruptions or even sporadic disconnections of an on going real-time session due to handovers between both networks of different types and networks of the same type.

    Many tests have already been done in this area and one may wonder why it is worth spending even more time investigating it? This thesis focuses on the important problem of providing session security despite handovers between networks (be they operated by the same operator or different operators and be they the same link technologies or different). One of the goals in this thesis is to investigate how an ongoing speech session can continue despite a change in transmission media1. Additionally, a number of security threats that could occur due to the handover will be identified and presented. Finally, the most suitable solution to address these threats will be tested in a real environment. Eventual shortcomings and weaknesses will be identified and presented; along with suggestions for future work. 

    1 When utilizing IP over carriers such as wired Ethernet, WLAN, and 3G.

  • 331. Dzanko, M.
    et al.
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Mikac, B.
    Zervas, G.
    Hugues-Salas, E.
    Simeonidou, D.
    Synthesis, resiliency and power efficiency of function programmable optical nodes2015In: Proceedings of the 13th International Conference on Telecommunications, IEEE , 2015Conference paper (Refereed)
    Abstract [en]

    Due to the large transmibion speeds and enormous volumes of transferred data, network availability performance is one of the key ibues in optical long-haul networks, comprising nodes implemented by optical crob-connects (OXCs). In this context, the design of OXCs is becoming very challenging since they have to support both legacy lower bit-rates and future highspeed super-channels by means of flexible allocation of spectral resources, and at the same time provide high availability of established connections. In this paper we study the availability and power consumption of different node architectures. We focus on the design of the new generation of synthetic programmable OXCs based on the Architecture on Demand concept which can reduce the number of utilized node components when a certain part of signals is switched at the fibre level, resulting in lower mean down time and power consumption compared to traditional node architectures.

  • 332.
    Dán, György
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Carlsson, N.
    Centralized and distributed protocols for tracker-based dynamic swarm management2013In: IEEE/ACM Transactions on Networking, ISSN 1063-6692, E-ISSN 1558-2566, Vol. 21, no 1, 297-310 p.Article in journal (Refereed)
    Abstract [en]

    With BitTorrent, efficient peer upload utilization is achieved by splitting contents into many small pieces, each of which may be downloaded from different peers within the same swarm. Unfortunately, piece and bandwidth availability may cause the file-sharing efficiency to degrade in small swarms with few participating peers. Using extensive measurements, we identified hundreds of thousands of torrents with several small swarms for which reallocating peers among swarms and/or modifying the peer behavior could significantly improve the system performance. Motivated by this observation, we propose a centralized and a distributed protocol for dynamic swarm management. The centralized protocol (CSM) manages the swarms of peers at minimal tracker overhead. The distributed protocol (DSM) manages the swarms of peers while ensuring load fairness among the trackers. Both protocols achieve their performance improvements by identifying and merging small swarms and allow load sharing for large torrents. Our evaluations are based on measurement data collected during eight days from over 700 trackers worldwide, which collectively maintain state information about 2.8 million unique torrents. We find that CSM and DSM can achieve most of the performance gains of dynamic swarm management. These gains are estimated to be up to 40% on average for small torrents.

  • 333.
    Dán, György
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Carlsson, Niklas
    Linköping University.
    Dynamic Content Allocation for Cloud-assisted Service of Periodic Workloads2014In: INFOCOM, 2014 Proceedings IEEE, IEEE conference proceedings, 2014, 853-861 p.Conference paper (Refereed)
    Abstract [en]

    Motivated by improved models for content workloadprediction, in this paper we consider the problem of dynamiccontent allocation for a hybrid content delivery system thatcombines cloud-based storage with low cost dedicated serversthat have limited storage and unmetered upload bandwidth. Weformulate the problem of allocating contents to the dedicatedstorage as a finite horizon dynamic decision problem, and showthat a discrete time decision problem is a good approximation forpiecewise stationary workloads. We provide an exact solution tothe discrete time decision problem in the form of a mixed integerlinear programming problem, propose computationally feasibleapproximations, and give bounds on their approximation ratios.Finally, we evaluate the algorithms using synthetic and measuredtraces from a commercial music on-demand service and giveinsight into their performance as a function of the workload characteristics.

  • 334.
    Dán, György
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Lui, King-Shan
    The University of Hong-Kong.
    Tabassum, Rehana
    University of Illinois at Urbana-Champaign.
    Zhu, Quanyan
    University of Illinois at Urbana-Champaign.
    Nahrstedt, Klara
    University of Illinois at Urbana-Champaign.
    SELINDA: A Secure, Scalable and Light-Weight Data Collection Protocol for Smart Grids2013In: 2013 IEEE International Conference on Smart Grid Communications (SmartGridComm), 2013, 480-485 p.Conference paper (Refereed)
    Abstract [en]

    Security in the smart grid is a challenge as an increasing number of sensors and measurement devices are connected to the power grid. General purpose security protocols are not suitable for providing data security to devices with limited memory, computational power and network connectivity. In this paper, we develop a secure and light-weight scalable security protocol that allows a power system operator (PO) to collect data from measurement devices (MDs) using data collectors (DCs). The security protocol trades off between computations and device memory requirements and provides flexible association between DC and MDs. These features allow data to be securely transferred from MDs to PO via mobile or untrustworthy DCs. We analyze the complexity and security of the protocol and validate its performance using experiments. Our results confirm that our proposed protocol collects data in a secure, fast and efficient manner.

  • 335.
    Dössel, Leefke
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Anytime reliability of systematic LDPC convolutional codes2012In: Communications (ICC), 2012 IEEE International Conference on, IEEE , 2012, 2171-2175 p.Conference paper (Refereed)
    Abstract [en]

    We propose a LDPC Convolutional Code ensemble together with an expanding-window message-passing decoder that asymptotically have anytime properties when used for streaming transmission on the binary erasure channel. We show analytically that the decoding erasure probability of these codes decays exponentially over decoding delay and determine the corresponding anytime exponents.

  • 336.
    Ebler, Mats
    et al.
    KTH, Superseded Departments, Teleinformatics.
    Flodén, Anders
    KTH, Superseded Departments, Teleinformatics.
    Mobility for Cordless Multimedia1995Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This project has developed a system for cordless multimedia business communication. It supports multimedia conferencing using existing applications across a mix of cordless and wired networks.

  • 337.
    Ebrahimi, Hamid
    KTH, Superseded Departments, Teleinformatics. KTH, School of Information and Communication Technology (ICT).
    Linjelyssnare för Gränssnitt mot DECT-basestation1998Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There purpose of this thesis was design and evaluate a device which would listen to the proprietary interface between a Private Automatic Branch Exchange (PBX) and a Digital Enhanced Cordless Telecommunications (DECT) basestation. The signal information has been transfered to a PC in order to collect and analyse data. The analysis has been limited to the bottom 4 layers. The software developed enables the display of the messages in either hex or clear text.

  • 338.
    Eckerström, Johan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Location Aware Communication2003Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Automotive telematic systems will be as common in future cars as ABS and airbags are in current cars. These systems will provide services such as navigation aid, automatic emergency alerts, traffic and road information, information about parking possibilities, tourist information, and personalized news. All these services need a communication link to the mobile Internet to be able to work properly. In this master’s thesis General Packet Radio Service, GPRS will be investigated and evaluated as a bearer for these kinds of services. A test application was built to test the location aware communication on the field. Upstream and downstream delays, possible bottlenecks in the network, connection set-up time, characteristics of different operators, and connection breakdowns where analyzed.

    The tests showed high network delays, and that many connection breakdowns occurred. The operators did not differ much when it comes to performance. One mayor drawback with GPRS is the low scalability with respect to operator’s lack of IP addresses, which will be discussed.

    Conclusions of the evaluation were that only certain location-based services are suitable over GPRS with the quality of today.

  • 339.
    Edström, Petter
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Overhead Impacts on Long-Term Evolution Radio Networks2007Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As a result of the constant efforts to improve mobile system performance and spectral efficiency, the 3GPP standardization forum is currently defining new architectural and functional requirements that hope to ensure long-term evolution (specifically defined as the “Long-Term Evolution (LTE) concept”) and general future competitiveness of the 2G and 3G radio access technologies.

    Previous discussions on LTE efficiency have been focused on general assumptions on signaling overhead and overall system capacity, based on experience from existing mobile systems. However, as 3GPP standardization has become more mature (although not yet settled), there is a need to investigate how different potential LTE services will be affected by the use of available overhead information and basic scheduling algorithms. This thesis investigates the lower protocol layers’ overhead impacts on the downlink for different packet switched services, in an LTE radio access network (RAN).

    Results show that the use of RTP/TCP/IP header compression (ROHC) is the single most important factor to reduce payload overhead, for packet sizes of ~1kB or smaller. However, for packets larger than ~1 kB, the use of ROHC becomes insignificant.

    Protocol headers – including the AMR frame header, RLC/MAC headers, and CRC where applicable – remain the largest part of payload overhead regardless of packet size and header compression (ROHC). For VoIP over the UDP protocol (with ROHC), RLC/MAC headers constitute the largest part of protocol headers.

    For TCP/IP applications (without ROHC), TCP/IP headers are predominant. Services that require packet sizes beyond ~1 kB will require about the same power per payload bit regardless of percentage of payload overhead.

  • 340.
    Egman, Tommy
    KTH, Superseded Departments, Teleinformatics.
    Solution Verification for Call Centre in BC101999Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report is about how a Call Centre solution can be verified and what different tools that are needed to be able to do a proper verification. The Call Centre that are being verified is Ericsson’'s MD110 Call Centre for BC10. The different parts that the report is focusing on are how to generate Telephony traffic into the MD110 over ISDN, to measure LAN activities, and to generate Call Centre Agents behaviour. The report will come to conclusions that certain ways of handling the solution can improve the performance of the Call Centre.

  • 341. Ehdaie, M.
    et al.
    Alexiou, Nikolaos
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Ahmadian, M.
    Aref, M. R.
    Papadimitratos, Panagiotis
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Key splitting for random key distribution schemes2012In: Network Protocols (ICNP), 2012 20th IEEE International Conference on, IEEE , 2012, 6459951- p.Conference paper (Refereed)
    Abstract [en]

    A large number of Wireless Sensor Network (WSN) security schemes have been proposed in the literature, relying primarily on symmetric key cryptography. To enable those, Random Key pre-Distribution (RKD) systems have been widely accepted. However, WSN nodes are vulnerable to physical compromise. Capturing one or more nodes operating with RKD would give the adversary keys to compromise communication of other benign nodes. Thus the challenge is to enhance resilience of WSN to node capture, while maintaining the flexibility and low-cost features of RKD. We address this problem, without any special-purpose hardware, proposing a new and simple idea: key splitting. Our scheme does not increase per-node storage, and computation and communication overheads, and it can increase connectivity. More important, it achieves a significant increase in resilience to compromise compared to the state of the art, notably when the adversary does not have overwhelming computational power.

  • 342.
    Ehdaie, Mohammad
    et al.
    CCL, K.N. Toosi University of Technology, Iran.
    Alexiou, Nikolaos
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Ahmadian, Mahmoud
    CCL, K.N. Toosi University of Technology, Iran.
    Reza Aref, Mohammad
    CCL, K.N. Toosi University of Technology, Iran.
    Papadimitratos, Panos
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Key Splitting for Random Key Distribution Schemes2012In: 7th Workshop on Secure Network Protocols (NPSec12), 2012Conference paper (Refereed)
  • 343. Ehdaie, Mohammad
    et al.
    Alexiou, Nikolaos
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Attari, Mahmoud Ahmadian
    Aref, Mohammad Reza
    Papadimitratos, Panos
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Key splitting: making random key distribution schemes resistant against node capture2015In: Security and Communication Networks, ISSN 1939-0114, E-ISSN 1939-0122, Vol. 8, no 3, 431-445 p.Article in journal (Refereed)
    Abstract [en]

    A large number of random key pre-distribution (RKD) schemes have been proposed in the literature to secure wireless sensor network applications, relying on symmetric key cryptography. However, sensor nodes are exposed to physical compromise by adversaries, who target the symmetric keys stored at each node. With the stolen keys in their possession, the adversaries are then able to compromise communication links between benign nodes. Here, the big challenge arises: how to increase resilience of RKD schemes for wireless sensor networks to node capture, while maintaining the flexibility and low-cost features of RKD? We propose the idea of key splitting to address this problem, without the need of any special-purpose hardware. Our key splitting scheme neither increases per-node storage nor introduces additional computation and communication overheads. Nevertheless, it can achieve better connectivity. More importantly, it significantly increases resilience to node compromise, when the adversary does not have overwhelming computational power.

  • 344.
    Eidlert, Fredrik
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Messaging and positioning in a dynamic TETRA environment2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Advanced communication with capabilities such as voice, data, and messaging usually requires an infrastructure with base stations, servers, and etcetera. The TETRA technology offers such communication not only in TMO (infrastructure-based network) but also in DMO where all nodes communicate directly (or via a repeater) with each other.

    This master’s thesis concerns messaging (specifically short messages) in a dynamic multi link TETRA DMO network. It examines what type of messaging technique to use and how to do path selection. The messages will be clear text, status, and GPS location information. The solution is implemented as a part of the ISIS software (which is developed by Know IT Dataunit). The planned multi link-part of the thesis could not be tested, so there is no implementation or evaluation of this. The evaluation of the implementation concerning sending and reception of messages shows that the proposed solution fulfils the demands for this kind of product. During a four day long test, messages (short text messages and positioning messages) were sent and received while a normal number of voice conversations took place, without packet loss.

  • 345. Eisenblaetter, Andreas
    et al.
    Geerdes, Hans-Florian
    Gross, James
    Punyal, Oscar
    Schweiger, Jonas
    A Two-Stage Approach to WLAN Planning: Detailed Performance Evaluation Along the Pareto Frontier2010In: Proceedings of the 8th International Symposium on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks (WiOpt), 2010, 2010, 227-236 p.Conference paper (Refereed)
    Abstract [en]

    This paper proposes an efficient solution to the open problem of network planning for large-scale WLAN deployments. WLAN performance is governed by the Csma-Ca protocol, whose dynamic effects are difficult to capture. Accurate performance evaluation depends on simulations and takes time. A detailed analysis of dozens candidate designs with varying Ap positions and channel assignments during network planning is therefore infeasible. In our solution, we first identify few good candidate designs using a multi-criteria optimization model, which features notions of cell overlap and station throughput. These candidate designs are taken from the corresponding Pareto frontier. In the second step, we evaluate the performance of the candidate designs by means of simulations. We apply our method to a realistic, large-scale planning scenario for an indoor office environment. The detailed simulations reveal important characteristics of the candidate designs that are not captured by the optimization model. The resulting performance differs significantly across the candidate designs. Hence, this approach successfully combines the benefits of mathematical optimization and simulations, yet avoiding their individual drawbacks.

  • 346.
    Ejigayehu Teka, Kaleab
    KTH, School of Information and Communication Technology (ICT).
    Energy Effcient Design and Bandwidth Assignment in Wireless Access Networks2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In recent years, traffic demands and quality of service requirements in cellular networks is increasing rapidly. Network operators deploymore number of base stations or increase the transmission power of the existing deployment in order to satisfy this user demand. This increases theenergy consumption and operational cost of cellular networks as well as the capital expenditures. Energy efficient design of cellular networks is a promising strategy to reduce energy consumption. Proper utilization of spectrum, high spectral efficiency and application of interference mitigation approaches provides more capacity in wireless access. Traditional bandwidth allocationschemes are intended to maximize the throughput of the system and increase the quality of service. Different resource allocation methods have been proposed as a solution for energy efficient resource management in wireless access networks. We investigate the efficiency of different resource allocation methods and the effect of excess capacity for reducing the total power consumption.

    In this thesis we intend to analyze the impact of excess capacity on reducing energy consumption in the network. Performance of different bandwidth allocation schemes is studied in order to reduce power consumption as much as possible. Three different resource allocation schemes have been studied depending on the way they distribute available resourcesblocks(RBs) to users. The first scheme is equal bandwidth allocation where users are assigned resources equally in a round robin manner. The second scheme is proportional bandwidth allocation scheme with residuals. This scheme assigns the whole resources considering the quality of service of users. The third one is proportional resource allocation without residuals. Here resources are allocated until every user meets the required quality of service and then leaves the residual resources.

  • 347.
    Ejner, Mikael
    KTH, Superseded Departments, Teleinformatics.
    Bi-directional Differentiated Services in aBroadband Access Server1999Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Quality of Service (QoS) is a highly desired feature of an IP network. The best-effort quality of traffic behaviour that the Internet provides by default today is not enough for certain timing-, mission- and throughput-critical applications such as video conferencing. One approach to achieve Quality of Service is Differentiated Services (DiffServ). However, one shortcoming of DiffServ is that it is unidirectional. This means that a user paying for premium FTP service will, when downloading a file, only get premium service for the requests, not for the actual file transfer.

    The goal of this project was to find a suitable method for making DiffServ bi-directional.

    This report presents the background and some available options, and motivates a preferred solution for the bi-directional Differentiated Services problem. The preferred option is, as the discussion shows, a centralised server-based solution with bi-directional DiffServ as an integrated feature of a policy-based network. A primitive prototype system was implemented to validate the concept.

  • 348. Eklund, J.
    et al.
    Grinnemo, K. -J
    Brunstrom, A.
    Cheimonidis, Georgios
    KTH. Ericsson Research.
    Ismailov, Y.
    Impact of slow start on SCTP handover performance2011In: Proc Int Conf Comput Commun Networks ICCCN, 2011Conference paper (Refereed)
    Abstract [en]

    The rapidly growing interest in untethered Internet connections, especially in terms of WLAN and 3G/4G mobile connections, calls for intelligent session management: a mobile device should be able to provide a reasonable end-user experience despite location changes, disconnection periods and, not least, handovers. As part of an effort to develop a SCTP-based session management framework that meets these criteria, we are studying ways of improving the SCTP handover delay for real-time traffic; especially the startup delay on the connection between a mobile device and the target access point. To obtain an appreciation of the theoretically feasible gains of optimizing the startup delay on the handover-target path, we have developed a model that predicts the transfer times of SCTP messages during slow start. This paper experimentally validates our model and demonstrates that it could be used to predict the message transfer times in a variable bitrate flow by approximating the variable flow with a constant dito. It also employs our model to obtain an appreciation of the startup delay penalties incured by slow start during handovers in typical mobile, real-time traffic scenarios.

  • 349.
    Eklund, Martin
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Ståhlberg, Patrik
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Distributed denial of service attacks: Protection, Mitigation, and Economic Consequences2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Distributed Denial of Service attacks is a problem that constantly threatens companies that rely on the internet for major parts of their business. A successful DDoS attack that manages to penetrate a company’s network can lead to devastating damages in the form of lost income, reduced productivity, increase in costs, and damage to the company’s image and reputation.

    The different DDoS attacks are many and of different character and often Offer different parts of the network, which makes it very difficult to defend against. It is also very clear that DDoS attacks are increasing in both numbers and size every year. From our experiments we have proven that anyone with little knowledge and limited resources can perform DDoS attacks that will make a website unavailable. This fact should cause companies that base their business on the internet, aware that they are likely to someday be subject to a DDoS attack.

    From our research we have found a variety of different DDoS solutions on the market that promise to offer protection. Many of which claim to protect against all different types of DDoS attacks. In practice it is impossible to find something that guarantees 100% safety. According to earlier research in the field, there are many different ways of protecting a network against DDoS attacks, e.g. via Software Defined Networking, Hop-Count Filtering, or Kill-bots.

    Our own tests show that a virtual firewall can offer protection against DDoS attacks on a low scale, but that such a solution has a number of weaknesses. If the firewall does protect the website, the attacker could instead shift to attacking the firewall itself.

    Our research also shows that the most common motives behind DDoS attacks are criminal purposes. Criminals use DDoS attacks to earn money by offering directed DDoS attacks against websites or by trying to blackmail companies into paying a fee for not being attacked.

    We have also seen that the economic consequence of DDoS attacks are devastating if not handled with a sufficiently fast response. After investigating the e-commerce company CDON.com we learned that they could potentially lose roughly 36 410 SEK per minute when a DDoS attack is underway against them.

    In today’s business climate it is important for companies to be able to rely on the internet for their activity and for customers to have easy access to the company’s products and services. However, companies’ websites are being attacked and thus these companies need an explicit plan of how to mitigate such attacks.

  • 350.
    Eklöf, William
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Adaptive Video Streaming: Adapting video quality to radio links with different characteristics2008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    During the last decade, the data rates provided by mobile networks have improved to the point that it is now feasible to provide richer services, such as streaming multimedia, to mobile users. However, due to factors such as radio interference and cell load, the throughput available to a client varies over time. If the throughput available to a client decreases below the media’s bit rate, the client’s buffer will eventually become empty. This causes the client to enter a period of rebuffering, which degrades user experience. In order to avoid this, a streaming server may provide the media at different bit rates, thereby allowing the media’s bit rate (and quality) to be modified to fit the client’s bandwidth. This is referred to as adaptive streaming.

    The aim of this thesis is to devise an algorithm to find the media quality most suitable for a specific client, focusing on how to detect that the user is able to receive content at a higher rate. The goal for such an algorithm is to avoid depleting the client buffer, while utilizing as much of the bandwidth available as possible without overflowing the buffers in the network. In particular, this thesis looks into the difficult problem of how to do adaptation for live content and how to switch to a content version with higher bitrate and quality in an optimal way.

    This thesis examines if existing adaptation mechanisms can be improved by considering the characteristics of different mobile networks. In order to achieve this, a study of mobile networks currently in use has been conducted, as well as experiments with streaming over live networks. The experiments and study indicate that the increased available throughput can not be detected by passive monitoring of client feedback. Furthermore, a higher data rate carrier will not be allocated to a client in 3G networks, unless the client is sufficiently utilizing the current carrier. This means that a streaming server must modify its sending rate in order to find its maximum throughput and to force allocation of a higher data rate carrier. Different methods for achieving this are examined and discussed and an algorithm based upon these ideas was implemented and evaluated. It is shown that increasing the transmission rate by introducing stuffed packets in the media stream allows the server to find the optimal bit rate for live video streams without switching up to a bit rate which the network can not support.

    This thesis was carried out during the summer and autumn of 2008 at Ericsson Research, Multimedia Technologies in Kista, Sweden.

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