Change search
Refine search result
45678910 301 - 350 of 1980
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 301.
    Devlic, Alisa
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Graf, A.
    Barone, P.
    Evaluation of context distribution methods via Bluetooth and WLAN: Insights gained while examining Battery Power Consumption2008In: MobiQuitous 2008 - 5th International ICST Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services, 2008Conference paper (Refereed)
    Abstract [en]

    In a traditional context-aware system, most context information is local to a device. However, we may need access to context information from outside the device. Increasingly mobile electronic devices are equipped with Bluetooth and/or WLAN network interfaces. Both of these technologies enable ad hoc discovery & networking. In this paper we evaluate the use of these technologies for context distribution within a local area (i.e., limited to a single hop). Using Bluetooth, we begin by discovering devices using Bluetooth's discovery protocol, collect their context information, create an XML file containing this information, and distribute this file to all discovered devices, such that every device now has the same context information. Next we perform the same discovery, collect, and distribute functions, but using WLAN. In each case we have performed the cycle of operations starting with a fully charged battery and continuing until the device was not able to utilize the selected wireless interface any longer. Finally we compare both approaches to context distribution in terms of battery power consumption. We observe that Bluetooth consumes 2-6 times more energy for transmission of a 1MB file to two devices than to discover these two devices. Furthermore, the transfer of this file is two times slower than WLAN, and we must unicast this file to each device. Multicasting via WLAN proved to be less energy consuming than the Bluetooth transmission, if data is to be sent to more than three users. In addition, the energy to discover 2 devices along with their services using Bluetooth consumed 52 times more energy than to receive the same amount of data via a WLAN multicast. Thus, this paper shows that it is more energy efficient to distribute context knowledge to other devices, than having each device learn this information itself. Finally, we give equations for calculating the battery power consumption of transmitting data using any protocol that runs over Bluetooth or over WLAN.

  • 302.
    Devlic, Alisa
    et al.
    Ericsson Research.
    John, Wolfgang
    Ericsson Research.
    Sköldström, Pontus
    A use-case based analysis of network management functions in the ONF SDN model2012In: European Workshop on SDN, 2012Conference paper (Refereed)
    Abstract [en]

    The concept of software-defined networking (SDN) recently gained huge momentum in the industry, driven mainly by IT companies interested in data center applications. In this paper, however, we apply SDN to the carrier domain, which poses additional requirements in terms of network management functions. As a specific use-case we take a virtualized carrier network shared by multiple customers. We consider the current SDN model as defined by the Open Networking Foundation (ONF), including the OpenFlow and OF-config protocols. Through a step-by-step discussion of the rocedures required to configure and manage the virtualized network, we analyze the applicability of the current SDN model as specified by the ONF. As a result, we identify shortcomings and propose necessary extensions to the ONF SDN model. The highlighted extensions include control network bootstrapping considerations, updates to the SDN and NOS model, and most importantly extensions of the OF-config management data model

  • 303.
    Devlic, Alisa
    et al.
    Ericsson Research.
    John, Wolfgang
    Ericsson Research.
    Sköldström, Pontus
    Carrier-grade Network Management Extensions to the SDN Framework2012In: 8th Swedish National Computer Networking Workshop SNCNW 2012 Stockholm, 2012Conference paper (Refereed)
    Abstract [en]

    The concept of software-defined networking (SDN)recently  gained  huge  momentum  in  the  industry,  driven  mainlyby  IT  companies  interested  in  datacenter  applications.  In  thispaper, however, we consider SDN applied in the carrier domain,which poses additional requirements on the network architecture,including  network  management  functions.  We  derive  concreterequirements  for  the  use-case  of  a  virtualized  multi-provideraccess/aggregation  network  based  on  carrier-grade  SDN.  Wethen provide initial architectural considerations for integrationof  network  management  extensions  to  the  SDN  framework  asdefined  by  the  Open  Networking  Foundation  (ONF).  Architec-tural considerations include definition of the required entities andtheir interactions. Finally, we apply the proposed architecture onthe access/aggregation network use-case, outlining procedures ofhow  the  network  management  extensions  can  enable  networkwide and node specific management & configuration

  • 304.
    Devlic, Alisa
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Kamaraju, Pavan
    Lungaro, Pietro
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Segall, Zary
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Tollmar, Konrad
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    QoE-aware optimization for video delivery and storage2015In: 2015 IEEE 16th International Symposium on "A World of Wireless, Mobile and Multimedia Networks" (WoWMoM) 2015, Boston, MA, USA, 2015, 1-10 p.Conference paper (Refereed)
    Abstract [en]

    The explosive growth of Over-the-top (OTT) online video strains capacity of operators’ networks, which severely threatens video quality perceived by end users. Since video is very bandwidth consuming, its distribution costs are becoming too high to scale with network investments that are required to support the increasing bandwidth demand. Content providers and operators are searching for solutions to reduce this video traffic load, without degrading their customers’ perceived Quality ofExperience (QoE). This paper proposes a method that can programmatically optimize video content for desired QoE accordingto perceptual video quality and device display properties, while achieving bandwidth and storage savings for content providers, operators, and end users. The preliminary results obtained with Samsung Galaxy S3 phone show that up to 60% savings can be achieved by optimizing movies without compromising the perceptible video quality, and up to 70% for perceptible, but not annoying video quality difference. Tailoring video optimization to individual user perception can provide seamless QoE delivery across all users, with a low overhead (i.e., 10%) required to achieve this goal. Finally, two applications of video optimization: QoE-aware delivery and storage, are proposed and examined.

  • 305.
    Devlic, Alisa
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Kamaraju, Pavan
    Lungaro, Pietro
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Segall, Zary
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Tollmar, Konrad
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Towards QoE-aware adaptive video streaming2016In: 2015 IEEE 23rd International Symposium on Quality of Service (IWQoS), IEEE, 2016, 75-76 p., 7404713Conference paper (Refereed)
    Abstract [en]

    This paper describes a novel QoE-aware adaptive video streaming method that enhances the viewing experience on mobile devices and reduces cellular network bandwidth consumed by Dynamic Adaptive Streaming over HTTP (DASH) by considering perceptual video quality and data rate channel conditions in the bitrate adaptation process. By streaming an optimized video for the particular video quality and channel conditions toa mobile device, we can improve the worst video qualities causedby DASH streaming and reduce quality variations using fewer number of bits.

  • 306.
    Devlic, Alisa
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Lungaro, Pietro
    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.
    Segall, Zary
    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.
    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.
    Evaluation of energy profiles for mobile video prefetching in generalized stochastic access channels2014In: Mobile and Ubiquitous Systems: Computing, Networking, and Services: 10th International Conference, MOBIQUITOUS 2013, Tokyo, Japan, December 2-4, 2013, Revised Selected Papers, Springer, 2014, 209-223 p.Conference paper (Refereed)
    Abstract [en]

    This paper evaluates the energy cost reduction of Over-The-Top mobile video content prefetching in various network conditions. Energy cost reduction is achieved by reducing the time needed to download content over the radio interface by prefetching data on higher data rates, compared to the standard on demand download. To simulate various network conditions and user behavior, a stochastic access channel model was built and validated using the actual user traces. By changing the model parameters, the energy cost reduction of prefetching in different channel settings was determined, identifying regions in which prefetching is likely to deliver the largest energy gains. The results demonstrate that the largest gains (up to 70%) can be obtained for data rates with strong correlation and low noise variation. Additionally, based on statistical properties of data rates, such as peak-to-mean and average data rate, prefetching strategy can be devised enabling the highest energy cost reduction that can be obtained using the proposed prefetching scheme.

  • 307.
    Dhainaut, Guillaume
    KTH, School of Electrical Engineering (EES), Communication Networks.
    A reverse proxy for VoIP: Or how to improve security in a ToIP network2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The need for security is crucial in Telephony over IP (ToIP). Secure protocols have been designed as well as specific devices to fulfill that need. This master thesis examines one of such devices called Session Border Controller (SBC), which can be compared to reverse proxies for ToIP. The idea is to apply message filters to increase security.

    This thesis presents the reasons of SBC existence, based on the security weaknesse sa ToIP network can show. These reasons are then used to establish a list of features which can be expected from a SBC and discuss its ideal placement in a ToIP network architecture. A test methodology for SBCs is established and used on the free software Kamailio as an illustration. Following this test, improvements of this software, regarding threats prevention and attacks detection, are presented and implemented.

  • 308. Dhaou, I. B.
    et al.
    Kondoro, A.
    Kelati, A.
    Rwegasira, D. S.
    Naiman, S.
    Mvungi, N. H.
    Tenhunen, H.
    Communication and security technologies for smart grid2017In: International Journal of Embedded and Real-Time Communication Systems, ISSN 1947-3176, E-ISSN 1947-3184, Vol. 8, no 2, 40-65 p.Article in journal (Refereed)
    Abstract [en]

    The smart grid is a new paradigm that aims to modernize the legacy power grid. It is based on the integration of ICT technologies, embedded system, sensors, renewable energy and advanced algorithms for management and optimization. The smart grid is a system of systems in which communication technology plays a vital role. Safe operations of the smart grid need a careful design of the communication protocols, cryptographic schemes, and computing technology. In this article, the authors describe current communication technologies, recently proposed algorithms, protocols, and architectures for securing smart grid communication network. They analyzed in a unifying approach the three principles pillars of smart-gird: Sensors, communication technologies, and security. Finally, the authors elaborate open issues in the smart-grid communication network.

  • 309. Di Giglio, A.
    et al.
    Schiano, M.
    Ruffini, M.
    Payne, D.
    Doran, N.
    Achouche, M.
    Jensen, R.
    O’Sullivan, B.
    Pfeiffer, T.
    Bonk, R.
    Rohde, H.
    Talli, G.
    Yin, X.
    Wessaly, R.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Montalvo, J.
    Towards the distributed core for ubiquitous superfast broadband optical access2014In: 2014 European Conference on Networks and Communications (EuCNC), 2014, 1-5 p.Conference paper (Refereed)
    Abstract [en]

    In this paper, we describe recent architectural and technological advances of the end to end optical network architecture proposed by the DISCUS project (the DIStributed Core for unlimited bandwidth supply for all Users and Services). The two main targets of DISCUS are the principle of equivalence in the access and the reduction of optical-to-electronic conversions in the metro-core network. Technological advances and techno-economic evaluation of Long-Reach Passive Optical Networks (LR-PON), as well as the optimal metro-core node architecture and the required network control plane framework are reported. Network infrastructure sharing challenges are also discussed.

  • 310.
    Di Marco, Piergiuseppe
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. Ericsson Research, Sweden.
    Athanasiou, Georgios
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. Institute of Communications and Computer Systems, National Technical University of Athens, Greece.
    Mekikis, Prodromos
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. Signal Theory and Communications Dept., Technical University of Catalonia, Barcelona, Spain.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    MAC-aware routing metrics for the internet of things2015In: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703XArticle in journal (Refereed)
    Abstract [en]

    The development of the internet of things (IoT) has significantly affected the concept of wireless networking. As the number of wireless devices is rising, new medium access control (MAC) and routing protocols have been developed to guarantee end-to-end network performance. When existing layered solutions are stacked together, there might be detrimental effects on the overall network performance. In this paper, an analysis of MAC and routing protocols for IoT is provided with focus on the IEEE 802.15.4 MAC and the IETF RPL standards. It is shown that existing routing metrics do not account for the complex interactions between MAC and routing, and thus novel metrics are proposed. This enables a protocol selection mechanism for selecting the routing option and adapting the MAC parameters, given specific performance constraints. Extensive analytical and experimental results show that the behavior of the MAC protocol can hurt the performance of the routing protocol and vice versa, unless these two are carefully optimized together by the proposed method.

  • 311.
    Di Marco, Piergiuseppe
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Santucci, F.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Effects of Rayleigh-lognormal fading on IEEE 802.15.4 networks2013In: Communications (ICC), 2013 IEEE International Conference on, IEEE conference proceedings, 2013, 1666-1671 p.Conference paper (Refereed)
    Abstract [en]

    The IEEE 802.15.4 communication protocol is a de-facto standard for wireless applications in industrial and home automation. Although the performance of the medium access control (MAC) of the IEEE 802.15.4 has been thoroughly investigated under the assumption of ideal wireless channel, there is still a lack of understanding of the cross-layer interactions between MAC and physical layer in the presence of realistic wireless channel models that include path loss, multi-path fading and shadowing. In this paper, an analytical model of these dynamics is proposed. The analysis considers simultaneously a composite Rayleigh-lognormal channel fading, interference generated by multiple terminals, the effects induced by hidden terminals, and the MAC reduced carrier sensing capabilities. It is shown that the reliability of the contention-based MAC over fading channels is often far from that derived under ideal channel assumptions. Moreover, it is established to what extent fading may be beneficial for the overall network performance.

  • 312.
    Di, Shuang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    USB Attached Network Performance: Uplink Performance2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    More and more people all over the world are using a USB modem to connect to the Internet. This is especially true in Sweden- which has the highest 3G coverage in Europe. Comparable to fixed broadband access, using a 3G USB modem is a wonderful experience for the customer. Increasingly, anywhere we can use our cellular phone is a place that we are able to access the Internet, even if we are traveling in a train, walking in a park, or sitting on the beach. This makes working on the move much easier. However, customers do not know if the network throughput, delay, and the cost of connectivity match their needs. Additionally, there is also the question of the time to connect to the network when there has not been some traffic for a period of time. However, the throughput, delay, and "time to connect" when using such a modem to connect to a wireless network depend on several factors. In this thesis we will examine these factors. More specifically, the thesis will analyze in detail the effects of using a USB attached network interface, in order to gain greater understanding of such an interface’s network performance. We have chosen to focus on the uplink, as it was expected to have a low throughput and it has not had as much attention as the downlink performance.

  • 313.
    Dimitriou, Eleftherios
    KTH, Superseded Departments, Teleinformatics.
    An Archive Robot for Video Mail1998Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today most of the real-time voice communications are carried over the Plain Old Telephone System (POTS). In the future that might well change. Research indicates a strong interest for developing the network to support real-time communications in a satisfactory way. Applications will be needed in this new world of IP (Internet Protocol) based communications.

    In this thesis we present an application called the Video Mail service. The Video Mail service can record and playback audio and video messages over the Internet using standard Internet telephony protocols. It is built on top of a more general platform called the Archive Robot. The Archive Robot provides the real-time functionality of the system. It is not explicitly designed to support the Video Mail service. Other services such as Conference Tool and Interactive Voice Response can also be supported.

    The Video Mail service was designed and implemented. Furthermore, this first prototype was used to evaluate the performance of the overall system.

  • 314. Ding, Zhiguo
    et al.
    Krikidis, Ioannis
    Rong, Beiyu
    Thompson, John S.
    Wang, Chao
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Yang, Sheng
    On Combating The Half-Duplex Constraint In Modern Cooperative Networks: Protocols And Techniques2012In: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 19, no 6, 20-27 p.Article in journal (Refereed)
    Abstract [en]

    A key issue that characterizes cooperative wireless networks is the half-duplex constraint (HDC), which refers to the inability of current modems to receive and transmit data in the same frequency at the same time. This hardware limitation results in inefficient use of system resources (bandwidth loss) as it requires dedicated bandwidth allocation for relay transmissions. Methods to overcome the HDC have been studied intensively in the literature of cooperative networks in recent years, and several approaches have been proposed. In this article we highlight four different techniques which combat the HDC by using existing technology. The first approach is non-orthogonal protocols, which allow the source to be active during relay transmissions. The second approach is the overlap of several relaying transmissions in order to mimic an ideal full-duplex operation. The third solution is the two-way relay channel where two sources exchange data via the assistance of a shared relay. Finally, the fourth approach incorporates cooperation on the "network" level and uses the cognitive radio concept to enable relay transmissions during silent periods of source terminals. These techniques summarize some of the most significant HDC solutions that cover both the physical and network layers.

  • 315. Dixit, A.
    et al.
    Lannoo, B.
    Colle, D.
    Pickavet, M.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Mahloo, Mozhgan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Efficient protection schemes for hybrid WDM/TDM Passive Optical Networks2012In: Communications (ICC), 2012 IEEE International Conference on, IEEE , 2012, 6220-6224 p.Conference paper (Refereed)
    Abstract [en]

    Hybrid WDM/TDM Passive Optical Network (PON) is a promising candidate for next-generation optical access (NGOA) solutions as it is able to offer a high splitting ratio and consequently achieves a relatively low cost and power consumption on a per-user basis compared with other NGOA architectures. On the other hand, the end users require a certain level of connection availability while the operators need to reduce the failure impact (i.e. to avoid a huge number of end users being affected by any single failure). Therefore, by evaluating the connection availability and failure impact robustness we identify the most efficient parts to provide resilience in a hybrid WDM/TDM PON from an operator and an end-user perspective. Then, we select the appropriate protection schemes to construct some novel reliable architectures and analyze their reliability performance in urban and rural scenarios. In this way, this paper provides a comprehensive insight into the most relevant protection mechanisms for hybrid WDM/TDM PONs.

  • 316. 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.

  • 317.
    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.

  • 318.
    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.

  • 319.
    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.

  • 320.
    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.

  • 321.
    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.

  • 322.
    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

  • 323. Dogadaev, Anton
    et al.
    Pang, Xiaodan
    RISE ACREO AB.
    Deng, Lei
    Ruepp, Sarah
    Dittmann, Lars
    Christiansen, Henrik
    Experimental and simulation analysis of the W-band SC-FDMA hybrid optical-wireless transmission2014In: IEEE Photonics Conference (IPC), San Diego, CA, USA, 2014, 77-78 p.Conference paper (Refereed)
  • 324. 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)
  • 325. 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.

  • 326. 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.

  • 327.
    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.

  • 328.
    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. 

  • 329. 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.

  • 330.
    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.))
  • 331.
    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.))
  • 332.
    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.

  • 333. 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%.

  • 334.
    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.

  • 335.
    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.

  • 336.
    Du, Rong
    et al.
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    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.

  • 337.
    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.

  • 338.
    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.

  • 339.
    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.

  • 340.
    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.

  • 341.
    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.

  • 342.
    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)
  • 343.
    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.

  • 344.
    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.

  • 345. Dwivedi, Satyam
    et al.
    Vedavathy, T.S.
    Shivaprasad, A.P.
    A divide-and-conquer approach with adaptive modulation to CDMA systems2003Conference paper (Refereed)
  • 346.
    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.

  • 347. 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.

  • 348.
    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.

  • 349.
    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.

  • 350.
    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.

45678910 301 - 350 of 1980
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf