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  • 1851.
    Vikrant, Nikam
    KTH, School of Information and Communication Technology (ICT).
    Design and Performance Evaluation of Resource Allocation Mechanisms in Optical Data Center Networks2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A datacenter hosts hundreds of thousands of servers and a huge amount of bandwidth is required to accommodate communication between thousands of servers. Several packet switched based datacenter architectures are proposed to cater the high bandwidth requirement using multilayer network topologies, however at the cost of increased network complexity and high power consumption. In recent years, the focus has shifted from packet switching to optical circuit switching to build the data center networks as it can support on demand connectivity and high bit rates with low power consumption.

    On the other hand, with the advent of Software Defined Networking (SDN) and Network Function Virtualization (NFV), the role of datacenters has become more crucial. It has increased the need of dynamicity and flexibility within a datacenter adding more complexity to datacenter networking. With NFV, service chaining can be achieved in a datacenter where virtualized network functions (VNFs) running on commodity servers in a datacenter are instantiated/terminated dynamically. A datacenter also needs to cater large capacity requirement as service chaining involves steering of large aggregated flows. Use of optical circuit switching in data center networks is quite promising to meet such dynamic and high capacity traffic requirements.

    In this thesis work, a novel and modular optical data center network (DCN) architecture that uses multi-directional wavelength switches (MD-WSS) is introduced. VNF service chaining use case is considered for evaluation of this DCN and the end-to-end service chaining problem is formulated as three inter-connected sub-problems: multiplexing of VNF service chains, VNFs placement in the datacenter and routing and wavelength assignment. This thesis presents integer linear programming (ILP) formulation and heuristics for solving these problems, and numerically evaluate them.

  • 1852.
    Villa, Tania
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Merz, R.
    Vidales, P.
    Performance evaluation of OFDMA femtocells link-layers in uncontrolled deployments2010In: 2010 European Wireless Conference, EW 2010, 2010, p. 825-832Conference paper (Refereed)
    Abstract [en]

    The rapidly increasing use of smart phones with Internet access or data connectivity solutions for laptops is putting the infrastructure of cellular operators under stress. Both the number of devices and the bandwidth requirement are increasing. Indoor usage is also becoming prominent. One envisioned solution is the use of so-called femtocells. Femtocells are portable and low-cost base-stations for in-home usage. They are deployed by end-users and are connected to the operator network by a digital subscriber line (DSL), cable modem or optical fiber connection. The femtocells are operated along with the macrocell in a typical two-tier network structure. The regular base stations operate in one tier and the femtocells operate in the other tier. In a shared spectrum configuration, the uncontrolled deployment and loose control of the femtocells generate challenging interference management scenarios. With extensive simulations, we perform an evaluation of several femtocell to femtocell interference scenarios and one macrocell to femtocell scenario. We focus on typical 4G cases, with an orthogonal frequency-division multiple access (OFDMA) physical layer and full frequency reuse. Our results show that without any interference management, system performance is significantly degraded and that complete outages occur in specific cases.

  • 1853.
    Visockas, Vilius
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Comparing Expected and Real–Time Spotify Service Topology2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Spotify is a music streaming service that allows users to listen to their favourite music. Due to the rapid growth in the number of users, the amount of processing that must be provided by the company’s data centers is also growing. This growth in the data centers is necessary, despite the fact that much of the music content is actually sourced by other users based on a peer-to-peer model.

    Spotify’s backend (the infrastructure that Spotify operates to provide their music streaming service) consists of a number of different services, such as track search, storage, and others. As this infrastructure grows, some service may behave not as expected. Therefore it is important not only for Spotify’s operations (footnote: Also known as the Service Reliability Engineers Team (SRE)) team, but also for developers, to understand exactly how the various services are actually communicating. The problem is challenging because of the scale of the backend network and its rate of growth. In addition, the company aims to grow and expects to expand both the number of users and the amount of content that is available. A steadily increasing feature-set and support of additional platforms adds to the complexity. Another major challenge is to create tools which are useful to the operations team by providing information in a readily comprehensible way and hopefully integrating these tools into their daily routine. The ultimate goal is to design, develop, implement, and evaluate a tool which would help the operations team (and developers) to understand the behavior of the services that are deployed on Spotify’s backend network.

    The most critical information is to alert the operations staff when services are not operating as expected. Because different services are deployed on different servers the communication between these services is reflected in the network communication between these servers. In order to understand how the services are behaving when there are potentially many thousands of servers we will look for the patterns in the topology of this communication, rather than looking at the individual servers. This thesis describes the tools that successfully extract these patterns in the topology and compares them to the expected behavior.

  • 1854.
    Vlasenko, Michail
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Supervision of video and audio content in digital TV broadcasts2007Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    An automatic system for supervision of the video and audio content in digital TV broadcasts was investigated in this master’s thesis project. The main goal is to find the best and most cost effective solution for Teracom to verify that the broadcast TV content as received by remote receivers is the same as that incoming to Teracom from content providers. Different solutions to this problem will be presented.

    The report begins with some background information about the Swedish terrestrial digital TV network and the MPEG-2 compression standard used to transport audio and video; including a description of the DVB Systems and Transport Stream protocol. It describes two current techniques for the supervision of the audio and video content, including an evaluation of these techniques.

    The first solution is to monitor the video and audio content either by detecting common errors such as frozen picture, visible artifacts, or by comparing the content from two different sources, i.e. a comparison of the output and the input content. The later could be done using video fingerprinting. The second solution monitors the video and audio content indirectly by analyzing the Transport Stream. This could be done either by comparing two Transport Streams to verify that the broadcast signal is identical to the received signal or by detecting common errors in the streams.

    Further two new potential solutions will be presented based on the research utilizing background knowledge of the MPEG-2 compression standard. The thesis ends with a summary with conclusions and evaluations of all four solutions and future work.

  • 1855.
    Vodopivec, Dario
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    On-demand Television combined with non-real-time Peer-to-Peer Content Delivery for Television Content Providers2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the expansion of the Internet and an increasing fraction of consumers having broadband connections, more and more content is finding its way on-line. Video content is becoming one of the most popular types of media content on the Internet. Traditional media content providers, such as television networks, are placing their content on the Internet in order to gain a broader audience. On-demand websites such as kanal5play.se allow viewers to view the multimedia content they want at the time of their choice. While this gives viewers flexibility in their viewing, it creates resource problems for content providers.

    Statistics from Kanal5 AB show that, even with individual viewers requesting content when they want, there are still patterns in which multiple viewers watch the same content at the same time. This means there are correlations in the demand for content. With unicast distribution this leads to spikes in requirements for bandwidth to the viewers. These peaks lead to high costs for network and server resources to deliver the requested content, but these resources have low average utilization. This thesis project investigates how a content provider can make use of each viewer’s own resources to deliver content to other users using peer-to-peer techniques. The thesis evaluates what methods can be used in order to reduce the content provider’s resource requirements during peak hours by exploiting copies of contents that have already been delivered to viewers who requested this same content earlier.

    A prototype was made to evaluate the suggested design using Java Remote Method Invocation (RMI), which is built on top of the Transfer Control Protocol (TCP). Experiments show that an initial delay of several seconds is reached on a network with a simulated delay of 100ms, while a minimal initial delay was observed on a network with low delay, i.e. ideal conditions. The throughput results of the prototype show that the suggested solution is adequate for delivering on-demand content supplied by Kanal5 AB. However, the relatively poor startup performance of this solution argues for tuning the application to better work with the TCP protocol or to utilize another transport protocol - especially if the round-trip delay is large as TCP’s 3-way handshake and flow control algorithm limit the performance of the prototype system.

  • 1856.
    Voicu, Andra M.
    et al.
    Rhein Westfal TH Aachen, Inst Networked Syst, Aachen, Germany..
    Lava, Laurent
    Rhein Westfal TH Aachen, Inst Networked Syst, Aachen, Germany..
    Simic, Ljiljana
    Rhein Westfal TH Aachen, Inst Networked Syst, Aachen, Germany..
    Petrova, Marina
    KTH, School of Information and Communication Technology (ICT).
    The Importance of Adjacent Channel Interference: Experimental Validation of ns-3 for Dense Wi-Fi Networks2017In: Proceedings Of The 20th ACM International Conference On Modelling, Analysis and Simulation of Wireless And Mobile Systems (MSWIM'17), Association for Computing Machinery (ACM), 2017, p. 43-52Conference paper (Refereed)
    Abstract [en]

    In its evolution to provide ever higher data rates, the Wi-Fi standard has incorporated sophisticated PHY-layer techniques, which has in turn increased the complexity of network-wide interference relationships. Proper modelling of the resulting inter-device interactions is crucial for accurately estimating Wi-Fi network performance, especially in the contemporary context of traffic and network densification. Event-driven simulators like the open-source ns-3 are in principle able to capture these interactions, however it is imperative to validate, against experimental results, whether their underlying models reflect the network behaviour in practice. In this paper we first perform experiments in a large-scale indoor testbed to validate the IEEE 802.11ac Wi-Fi model in ns-3, for various channel width and allocation configurations. Our results show that ns-3 captures Wi-Fi co-channel interactions with reasonable precision, but fails to model adjacent channel interference (ACI), which our experiments show to be critical in dense networks. We therefore propose and implement an ACI model in ns-3. Importantly, our model successfully captures the qualitative behaviour of the CSMA/CA mechanism when transmissions on adjacent channels occur. Further, our ACI implementation significantly improves the accuracy of both the network and per-device throughput estimates for the considered dense IEEE 802.11ac network compared to the basic ns-3 Wi-Fi model without ACI. For example, without ACI modelling, ns-3 overestimates the aggregate network throughput by up to 230%, whereas with our ACI implementation the aggregate throughput estimate is no more than 65% higher than the experimental results.

  • 1857.
    Vu Hoang, Tung
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Secure data and voice over wireless networks in disaster and emergency response2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Communication is often limited in a disaster area and other emergency situations where no infrastructure exists or existing infrastructure has been destroyed. This makes its difficult for relief workers in the field to communicate with one another and with their home head office. Ericsson Response has developed a Wireless LAN in Disaster and Emergency Response (WIDER) solution. WIDER is based on broadband Wireless LAN internetworking to satellite and GSMnetworks. The WIDER solution has identified ways for organizations to share their communication infrastructure, and information in a secure and cost effective manner during an emergency response operation. Data over WIDER needs to be secured to prevent from unauthorized access to sensitive information of relief organizations. VoIP calls should be protected against eavesdropping. The thesis investigated how to enhance security solution in WIDER and implement a secure VoIP client. Measurements of the performance of WIDER and the total delay of VoIP over satellite were used to estimate the capability of WIDER before deployment in the field.

  • 1858.
    Vu Hong, Linh
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    DNS Traffic Analysis for Network-based Malware Detection2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Botnets are generally recognized as one of the most challenging threats on the Internet today. Botnets have been involved in many attacks targeting multinational organizations and even nationwide internet services. As more effective detection and mitigation approaches are proposed by security researchers, botnet developers are employing new techniques for evasion. It is not surprising that the Domain Name System (DNS) is abused by botnets for the purposes of evasion, because of the important role of DNS in the operation of the Internet. DNS provides a flexible mapping between domain names and IP addresses, thus botnets can exploit this dynamic mapping to mask the location of botnet controllers. Domain-flux and fast-flux (also known as IP-flux) are two emerging techniques which aim at exhausting the tracking and blacklisting effort of botnet defenders by rapidly changing the domain names or their associated IP addresses that are used by the botnet. In this thesis, we employ passive DNS analysis to develop an anomaly-based technique for detecting the presence of a domain-flux or fast- flux botnet in a network. To do this, we construct a lookup graph and a failure graph from captured DNS traffic and decompose these graphs into clusters which have a strong correlation between their domains, hosts, and IP addresses. DNS related features are extracted for each cluster and used as input to a classication module to identify the presence of a domain-flux or fast-flux botnet in the network. The experimental evaluation on captured traffic traces veried that the proposed technique successfully detected domain-flux botnets in the traces. The proposed technique complements other techniques for detecting botnets through traffic analysis.

  • 1859.
    Vu, Minh thanh
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Oechtering, Tobias J.
    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.
    Lossy distributed storage with limited failure loss2015In: Proceedings of the International Symposium on Wireless Communication Systems, VDE Verlag GmbH, 2015, p. 191-195Conference paper (Refereed)
    Abstract [en]

    In this paper a successive refinement problem is considered where decoders can access only distributed storage nodes, subject to an additional constraint on the loss of information if failures happen. We characterize the optimal tradeoff for a given a distortion tuple and an equivocation constraint between storage nodes. A binary example is provided to illustrate the trade-off between the loss of information constraint and the corresponding achievable rate region.

  • 1860.
    Vukadinovic, Vladimir
    et al.
    Disney Research Zürich.
    Helgason, Ólafur
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    An analytical model for pedestrian content distribution in a grid of streets2013In: Mathematical and computer modelling, ISSN 0895-7177, E-ISSN 1872-9479, Vol. 57, no 11-12, p. 2933-2944Article in journal (Refereed)
    Abstract [en]

    Mobile communication devices may be used for spreading multimedia data without support of an infrastructure. Such a scheme, where the data is carried by people walking around and relayed from device to device by means of short range radio, could potentially form a public content distribution system that spans vast urban areas. The transport mechanism is the flow of people and it can be studied but not engineered. We study the efficiency of pedestrian content distribution by modeling the mobility of people moving around in a city, constrained by a given topology. The model is supplemented by simulation of similar or related scenarios for validation and extension. The results show that contents spread well with pedestrian speeds already at low arrival rates into a studied region. Our contributions are both the queuing analytic model that captures the flow of people and the results on the feasibility of pedestrian content distribution.

  • 1861.
    Vuković, Ognjen
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Data Integrity and Availability in Power System Communication Infrastructures2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Society is increasingly dependent on the proper functioning of electric power systems. Today's electric power systems rely heavily on information and networking technology in order to achieve efficient and secure operation. Recent initiatives to upgrade power systems into smart grids target an even tighter integration with information and communication technologies in order to enable the integration of renewable energy sources, local and bulk generation and demand response. Therefore for a proper functioning of smart grids, it is essential that the communication network is secure and reliable both in the face of network failures and in the face of attacks. This thesis contributes to improving the security of power system applications against attacks on the communication infrastructure. The contributions lie in two areas.

    The first area is the interaction of network and transport layer protocols with power system application layer security. We consider single and multi-area power system state estimation based on redundant telemetry measurements. The state estimation is a basis for a set of applications used for information support in the control center, and therefore its security is an important concern. For the case of single-area state estimation, we look at the security of measurement aggregation over a wide area communication network. Due to the size and complexity of power systems, it can be prohibitively expensive to introduce cryptographic security in every component of the communication infrastructure. Therefore, we investigate how the application layer logic can be leveraged to optimize the deployment of network, transport and application layer security solutions. We define security metrics that quantify the importance of particular components of the network infrastructure. We provide efficient algorithms to calculate the metrics, and that allow identification of the weakest points in the infrastructure that have to be secured. For the case of multi-area state estimation, we look at the security of data exchange between the control centers of neighboring areas. Although the data exchange is typically cryptographically secure, the communication infrastructure of a control center may get compromised by a targeted trojan that could attack the data before the cryptographic protection is applied or after it is removed. We define multiple attack strategies for which we show that they can significantly disturb the state estimation. We also show a possible way to detect and to mitigate the attack.

    The second area is a study of the communication availability at the application layer. Communication availability in power systems has to be achieved in the case of network failures as well as in the case of attacks. Availability is not necessarily achieved by cryptography, since traffic analysis attacks combined with targeted denial-of-service attacks could significantly disturb the communication. Therefore, we study how anonymity networks can be used to improve availability, which comes at the price of increased communication overhead and delay. Because of the way anonymity networks operate, one would expect that availability would be improved with more overhead and delay. We show that surprisingly this is not always the case. Moreover, we show that it is better to overestimate than to underestimate the attacker's capabilities when configuring anonymity networks.

  • 1862.
    Vuković, Ognjen
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks.
    On the Security of Distributed Power System State Estimation under Targeted Attacks2013In: Proceedings of the 28th Annual ACM Symposium on Applied Computing, 2013, p. 666-672Conference paper (Refereed)
    Abstract [en]

    State estimation plays an essential role in the monitoring and control of power transmission systems. In modern, highly inter-connected power systems the state estimation should be performed in a distributed fashion and requires information exchange between the control centers of directly connected systems. Motivated by recent reportson trojans targeting industrial control systems, in this paper we investigate how a single compromised control center can affect the outcome of distributed state estimation. We describe five attack strategies, and evaluate their impact on the IEEE 118 benchmark power system. We show that that even if the state estimation converges despite the attack, the estimate can have up to 30% of error, and bad data detection cannot locate theattack. We also show that if powerful enough, the attack can impede the convergence of the state estimation, and thus it can blind the system operators. Our results show that it is important to provide confidentiality for the measurement data in order to prevent the most powerful attacks. Finally, we discuss a possible way to detect and to mitigate these attacks.

  • 1863.
    Vuković, Ognjen
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Mitigating Denial of Service Attacks using Anonymity Networks: Relationship Anonymity-Communication Overhead Trade-offManuscript (preprint) (Other academic)
    Abstract [en]

    Denial-of-service attacks are a significant threat to mission critical communication infrastructures, e.g., to industrial control systems. They are relatively easy to perpetrate, as an attacker that has access to communication links or equipment could observe the source and destination addresses for every message, and can identify and discard the messages exchanged between particular communication participants. Mix networks and anonymity networks could render these attacks more difficult by providing anonymous communication via relaying. Nevertheless, relaying introduces overhead and increases the end-to-end message delivery delay, which in practice must often be low. Hence, an important question is how to optimize anonymity for limited overhead and delay. In this paper we address this question by studying two anonymity networks: MCrowds, an extension of Crowds, which provides unbounded communication delay and Minstrels, which provides bounded communication delay. We derive exact and approximate analytical expressions for the relationship anonymity for these systems. Using MCrowds and Minstrels we show that, contrary to intuition, increased overhead does not always improve anonymity. We investigate the impact of the system's parameters on anonymity and on the optimal anonymity network parameters, and the sensitivity of anonymity to the misestimation of the number of attackers.

  • 1864.
    Vuković, Ognjen
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Traffic Analysis Attacks in Anonymity Networks: Relationship Anonymity-Overhead Trade-off2013Report (Other academic)
    Abstract [en]

    Mix networks and anonymity networks provide anonymous communication via relaying, which introduces overhead and increases the end-to-end message delivery delay. In practice overhead and delay must often be low, hence it is important to understand how to optimize anonymity for limited overhead and delay. In this work we address this question under passive traffic analysis attacks, whose goal is to learn the traffic matrix. For our study, we use two anonymity networks: MCrowds, an extension of Crowds, which provides unbounded communication delay and Minstrels, which provides bounded communication delay. We derive exact and approximate analytical expressions for the relationship anonymity for these systems. Using MCrowds and Minstrels we show that, contrary to intuition, increased overhead does not always improve anonymity. We investigate the impact of the system's parameters on anonymity, and the sensitivity anonymity to the misestimation of the number of attackers.

  • 1865.
    Wahlgren, Rune
    KTH, Superseded Departments, Teleinformatics.
    Broadcast of financial information : How to broadcast web information to wireless users1996Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Mobile or wireless information retrieval is an area that is expected to increased dramatically in near future. In order to meet the demand for broadband of content, and to learn how these systems can used for publishing, Bonnier is participating in the On the Move Project. But, the On the Move project intends to use UMTS. As this systems is not yet available, Bonnier has initiated a cooperation with Teracom in the MEMO project. The MEMO project will develop a common platform for an wireless asymmetric communication system that will consist of a broadband downstream channel (DAB) and narrowband upstream channels (GSM). They have also develop a framework of an architecture and a interface to the DAB channel for this purpose.

    Wireless asymmetric communication systems utelise the nature of an information retrieval session very well, because the request from the clients are very modest regarding demanded bandwidth in contrast to the server response which usually demand much bandwidth for downloading the requested information to the client.

    In my thesis project I have developed and implemented three different software's that will fit in the MEMO architecture and offer the user the specified functionality. That is, the user shall be able to retrieve information in broadcast and/or on-demand mode. The software's developed is a client part which will be running on the mobile host, a server software which will serve the client with the requested information, and a broadcast software which enables the content provider to broadcast specific content in their service. The broadcast channel is developed by Teracom.

    The result that this project has achieved is, first some measurement on a model of the system that shows the benefits with broadcast mode in the system. The test also showed that introduction of caching in the system considerably reduce the latency for the client in retrieving information. Second, their have been some needs outlined that the content provider have on these kinds on systems, and how the content provider shall construct a service that are intended for these kinds of systems.

  • 1866.
    Wahlund, Thomas
    KTH, Superseded Departments, Teleinformatics.
    Using Concentrators to build a cost effective network1995Independent thesis Advanced level (degree of Master (Two Years)), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    The intention with this project was to examine the way FTNS Nordic is using concentrators as network nodes to build a cost effective network. The strategy for where and when to place out new concentrators in the network was also analysed. In his presentation, Thomas will describe the different ways to use concentrators in the network, in order to make network subscribers share bandwidth between the point of access and the network switches. He will also describe a process to analyse the costs involved in placing out new concentrators. Some methods on how to calculate the cost of bandwidth according to the price list for leased lines, and how to calculate the optimised placement (according to the cost of lines) of new concentrators are also presented.

  • 1867.
    Walldén, Marcus
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Özkan, Aylin
    KTH, School of Information and Communication Technology (ICT).
    A graph database management system for a logistics-related service2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Higher demands on database systems have lead to an increased popularity of certain database system types in some niche areas. One such niche area is graph networks, such as social networks or logistics networks. An analysis made on such networks often focus on complex relational patterns that sometimes can not be solved efficiently by traditional relational databases, which has lead to the infusion of some specialized non-relational database systems. Some of the database systems that have seen a surge in popularity in this area are graph database systems.

    This thesis presents a prototype of a logistics network-related service using a graph database management system called Neo4j, which currently is the most popular graph database management system in use. The logistics network covered by the service is based on existing data from PostNord, Sweden’s biggest provider of logistics solutions, and primarily focuses on customer support and business to business.

    By creating a prototype of the service this thesis strives to indicate some of the positive and negative aspects of a graph database system, as well as give an indication of how a service using a graph database system could be created.

    The results indicate that Neo4j is very intuitive and easy to use, which would make it optimal for prototyping and smaller systems, but due to the used evaluation method more research in this area would need to be carried out in order to confirm these conclusions.

  • 1868.
    Waltersson, Roland
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Middleware for adaptive network connectivity2006Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As the coverage of modern wireless technologies expands, today’s mobile phones and PDAs often have a range of heterogeneous networks to which they may connect. It would benefit mobile applications to use the network which best corresponds to its need. However, making the handovers between networks transparent to allow communication sessions to survive is not trivial as the TCP/IP suite, used by most networking applications today, was initially not designed with mobility in mind.

    A Vinnova founded research project at Saab (together with associates1) has found that it could prove advantageous to monitor network quality together with the application’s needs and make intelligent decisions regarding what network to use. An algorithm for network classification and evaluation has been proposed.

    This thesis examined prerequisites and methods for implementing adaptive network connectivity through transparent handovers for mobile devices, resulting in a tentative model to demonstrate the mentioned research results. The prototype, implemented as a user space middleware, utilizes UDP encapsulation and a per-packet basis link evaluation, resulting in small overhead and fast context adaptation. Link monitoring ensures that server and clients are constantly updated about network quality and availability.

    The prototype yielded transparent handovers between networks, with short handover delays, at the cost of reduced performance for fast networks.

    1 Blekinge Institute of Technology, Swedish National Testing and Research Institute, and SwedishRoad Administration

  • 1869.
    Wang, Chao
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Rasmussen, Lars
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Performance analysis of coded secondary relaying in overlay cognitive radio networks2012In: 2012 IEEE Wireless Communications and Networking Conference, WCNC, IEEE Communications Society, 2012, p. 294-299Conference paper (Refereed)
    Abstract [en]

    We study the error and diversity-multiplexing tradeoff (DMT) performance of a (secondary) multi-user relay network, where a class of finite field network codes are applied in the relays to efficiently provide spatial diversity. To eliminate spectral efficiency loss induced by half-duplex limitation we adopt the cognitive radio overlay spectrum sharing concept and consider aligning the relays' operation with that of a primary system. To compensate the interference introduced by the secondary relaying, the secondary destination also transmits the primary signals to boost the signal power of the primary system. We also consider exploiting Automatic Repeat Request (ARQ) feedback signals from the secondary destination to minimize the energy consumption of the secondary system. In addition, by allowing multiple secondary sources to transmit non-orthogonally, the performance can be further enhanced.

  • 1870.
    Wang, Guojun
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Optimizing System Level Testing of Evolved Packet Gateway2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The goal of this thesis project is to improve industrial system testing efficiency. The thesis is mainly focused on the field of telecommunication. Testing is one of the most important steps before selling a product to customers and testing is also an important component of after sale maintenance. The work load for testers can be decreased and more projects could be carried out in parallel, if the testing efficiency can be improved.

    The thesis project is carried out within the Ericsson Product Development Unit (PDU) Packet Core System Test section. The goal is to improve the system testing efficiency of the Evolved Packet Gateway, as system testing has gradually become one of the bottle necks for the whole product release. Ericsson wants to accelerate its pace in releasing new products to the market and releasing new software to their customers. An initial investigation was made to get a clear view about how the complete system testing procedure is currently carried out and then, an analysis was made based on this information. Ideas were collected for a proposed new implementation and finally a prototype for the most useful ideas was developed and evaluated to show how the system testing efficiency can be improved.

    Finally, these ideas were proved to be valuable for Ericsson PDU Packet Core System Test section and two of them have been adopted and are already under developing.

  • 1871.
    Wang, Huajun
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Hossain, Masum M.Aftab
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Cloud RAN architectures with optical and mm-Wave transport technologies2017In: 2017 19th International Conference on Transparent Optical Networks (ICTON), IEEE Computer Society, 2017, article id 8025007Conference paper (Refereed)
    Abstract [en]

    Cloud RAN has been regarded as a promising architecture for 5G mobile networks in terms of combination of implementing the very tight radio coordination schemes and sharing baseband processing and cooling system resources. However, the high capacity and stringent delay requirement for the fronthaul, the segment of the network between Baseband Units (BBU) and Remote Radio Heads (RRH) is one of the biggest barriers to larger deployments. To relax these constraints, physical layer functions can be split and centralized partially. In this paper, under one specific case scenario with the fixed number of LTE base stations, we calculate the transport capacity requirement for different physical layer function splitting solutions and adopt different transport technologies, i.e. Ethernet Passive Optical Network (EPON), Time-Wavelength Division Multiplexing PON, (TWDM-PON) and millimeter Wave (mm-Wave). We develop an end-to end power consumption model where the total power consumption is calculated by adding up the power utilized by RRHs, transport network and baseband processing. TWDM-PON shows better energy performance as fronthaul network when the capacity requirement is high, compared to EPON. The mm-Wave fronthaul is a better solution in terms of saving fiber and flexibility of deployment but comparatively more energy consuming.

  • 1872. Wang, J.
    et al.
    Ebrahimi, Masoumeh
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits. University of Turku, Finland.
    Huang, L.
    Li, Q.
    Li, G.
    Jantsch, A.
    Minimizing the system impact of router faults by means of reconfiguration and adaptive routing2017In: Microprocessors and microsystems, ISSN 0141-9331, E-ISSN 1872-9436, Vol. 51, p. 252-263Article in journal (Refereed)
    Abstract [en]

    To tolerate faults in Networks-on-Chip (NoC), routers are often disconnected from the NoC, which affects the system integrity. This is because cores connected to the disabled routers cannot be accessed from the network, resulting in loss of function and performance. We propose E-Rescuer, a technique offering a reconfigurable router architecture and a fault-tolerant routing algorithm. By taking advantage of bypassing channels, the reconfigurable router architecture maintains the connection between the cores and the network regardless of the router status. The routing algorithm allows the core to access the network when the local router is disabled.Our analysis and experiments show that the proposed technique provides 100% packet delivery in 100%, 92.56%, and 83.25% of patterns when 1, 2 and 3 routers are faulty, respectively. Moreover, the throughput increases up to 80%, 46% and 33% in comparison with FTLR, HiPFaR, and CoreRescuer, respectively.

  • 1873.
    Wang, Jiaheng
    et al.
    National Mobile Communications Research Laboratory, Southeast University, Nanjing, China .
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Simplified alternating optimization for robust MMSE MIMO transceiver2011In: International Conference on Wireless Communications and Signal Processing (WCSP), 2011, IEEE conference proceedings, 2011Conference paper (Refereed)
    Abstract [en]

    We consider a worst-case robust transceiver design for multiple-input multiple-output (MIMO) channels, under the minimum mean square error (MMSE) criterion, to combat against the imperfection of channel state information (CSI). The joint robust transceiver design is formulated as a minimax problem. We show that for a given precoder (equalizer), the optimal robust equalizer (precoder) is obtained in a semi-closed form by channel diagonalization. Thus, a joint robust transceiver can be efficiently achieved by alternately optimizing the equalizer and precoder, where in each iteration only a power allocation problem is to be solved. We also propose efficient algorithms to solve the power allocation problems in each iteration.

  • 1874.
    Wang, Ke
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Exploiting Presence2008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    By exploiting context awareness, traditional applications can be extended to offer better quality or new functions. Utilizing a context-aware infrastructure, a variety of context information is merged and processed to produce information that is useful to applications. Applications exploiting such context can provide more intelligent and creative services to end users.

    This thesis examines two ways to make use of a user’s location along with room occupancy information in context aware applications: a Context Agent and a Call Secretary. In the former case, the application subscribes to room occupancy information via a context server, and provides a Meeting Room Booking System with “real-time” information about the utilization of the rooms which the room booking system is to manage. The Call Secretary acquires both location and room occupancy information from a server. When the user is in one of the meeting rooms and multiple people are present, then this is interpreted as the user being in a meeting -- therefore it triggers a CPL module in a SIP proxy to redirect the user’s incoming call to their voice mail box. A description of the implementation of these two applications will be presented along with an evaluation of these applications’ performance.

    The evaluation of the Context Agent showed that it was straightforward to integrate information from a presence source and to extend the meeting room booking system to use this information. The Call Secretary needs a more reliable source for the user's location. However, given this location the Call Secretary provides the service which the user expects.

  • 1875.
    Wang, Ke
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101). Acreo AB, Kista, Sweden .
    Li, J.
    Djupsjöbacka, A.
    Chacinski, Marek
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101).
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101).
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101).
    Jacobsen, Gunnar
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101). Acreo AB, Kista, Sweden .
    Hurm, V.
    Makon, R. E.
    Driad, R.
    Walcher, H.
    Rosenzweig, J.
    Steffan, A. G.
    Mekonnen, G. G.
    Bach, H. -. G.
    100 Gb/s complete ETDM system based on monolithically integrated transmitter and receiver modules2010In: 2010 Conference on Optical Fiber Communication, Collocated National Fiber Optic Engineers Conference, OFC/NFOEC 2010, 2010, p. 5465571-Conference paper (Refereed)
    Abstract [en]

    A complete ETDM system based on monolithically integrated transmitter and receiver modules was demonstrated with BER performance below FEC threshold up to 107 Gb/s. ETDM signal at 112 Gb/s with clear eye opening was also observed.

  • 1876.
    Wang, Lei
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Ecole Polytechnique Fédérale de Lausanne, Switzerland.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Mosig, J. R.
    Wideband omnidirectional planar antenna with vertical polarization2017In: 2017 11th European Conference on Antennas and Propagation, EUCAP 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 3865-3868, article id 7928581Conference paper (Refereed)
    Abstract [en]

    In this paper we propose a circular leaky wave-antenna with omnidirectional radiation in the H-plane. The design utilizes double-layered strips to create an end-fire antenna. A linear tapering of the stripes in the design endows the antenna with a 27% impedance bandwidth of 26.4-34.6 GHz. The antenna is vertically polarized with a cross polarization below -30 dB. The antenna has low gain variation in H-plane and it is compact as a planar structure. Furthermore, it can be easily fabricated and integrated by standard PCB processing techniques, which is very promising for applications such as base stations for wireless communication, spectrum monitoring and jamming systems.

  • 1877.
    Wang, Lihui
    National Research Council of Canada.
    A Web-based Approach for Real-time Robot Operations2008In: International Journal of Internet Manufacturing and Services, ISSN 1751-6048, Vol. 1, no 2, p. 90-103Article in journal (Refereed)
    Abstract [en]

    Owing to the business decentralisation and outsourcing, manufacturing is moving toward the direction in distributed environment. A new enabling technology is required, especially in remote monitoring and control of daily manufacturing operations. As web is rooted into business, a web-based solution for real-time monitoring and control is preferable due to its popularity, low cost, and availability. However, unpredictable network traffic posts a major challenge for web-based real-time application development. This paper proposes to use computer graphics augmented with real sensor data for reducing data transmission over the network. Particularly, a web-based technology for remote robot operations is presented.

  • 1878.
    Wang, Lihui
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Fratini, L.
    Shih, A. J.
    Preface2017In: Procedia Manufacturing, ISSN 2351-9789, Vol. 10, p. vii-viiiArticle in journal (Refereed)
  • 1879.
    Wang, Liping
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fodor, Viktoria
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Cooperative geographic routing in wireless mesh networks2010Conference paper (Refereed)
    Abstract [en]

    We propose cooperative geographic routing (cGeo-routing) for wireless mesh networks by combining cooperative transmission with traditional geographic routing. We model and evaluate two cGeo-routing schemes including Cooperative-Random Progress Forwarding (C-RPF) and Cooperative-Nearest with Forward Progress (C-NFP). We show that cGeo-routing significantly increases the average transport capacity for a single hop in well connected mesh networks, and the gain increases with the transmitted signal-to noise ratio (SNR). Moreover, there exists an optimal topology knowledge range in C-RPF, whereas an optimal node density in C-NFP. Our results also suggest that hop-by-hop cooperation can increase transport capacity in high-connectivity and high-SNR regimes, however, it does not change the transport capacity scaling law of the mesh network.

  • 1880.
    Wang, Meiqian
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Furdek, Marija
    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.
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Wavelength overprovisioning strategies for enhanced optical path restoration2016In: International Conference on Transparent Optical Networks, IEEE Computer Society, 2016Conference paper (Refereed)
    Abstract [en]

    This paper proposes two wavelength overprovisioning strategies that can be used to improve the performance of path restoration in optical core networks under dynamic traffic conditions while considering single fiber link failure scenarios. The study presented in the paper shows that with the two proposed schemes it is possible to achieve nearly the same level of average connection availability and restorability typical of dedicated path protection schemes (i.e., 100%) with, on the other hand, better blocking probability performance.

  • 1881.
    Wang, Qiwen
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Jaggi, Sidharth
    Chinese Univ Hong Kong, Dept Informat Engn, SE-10044 Stockholm, Sweden..
    End-to-End Error-Correcting Codes on Networks With Worst-Case Bit Errors2018In: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 64, no 6, p. 4467-4479Article in journal (Refereed)
    Abstract [en]

    In highly dynamic wireless networks, communications face several challenges. In the first place, noise levels between nodes might be difficult to predict a priori. Besides, a Byzantine attacker hidden in the network, with knowledge of the network topology and observation of all transmissions, can choose arbitrary locations to inject corrupted packets. Considering that transmissions are usually in bits and hardware in wireless networks usually use modulation schemes with the size of modulation alphabet being powers of two, e.g. BPSK, QPSK, 16-QAM, 64-QAM, and so on, to address the above problem, we study coding for networks experiencing worst case bit errors, and with network codes over binary extension fields. We demonstrate that in this setup prior network error-correcting schemes can be arbitrarily far from achieving the optimal network throughput. A new transform metric for errors under the considered model is proposed. Using this metric, we replicate many of the classical results from coding theory. Specifically, new Hamming-type, Plotkin-type, and Elias-Bassalygo-type upper bounds on the network capacity are derived. A commensurate lower bound is shown based on Gilbert-Varshamov (GV)-type codes for error-correction. The GV codes used to attain the lower bound can be non-coherent, that is, they require neither prior knowledge of the network topology nor network coding kernels. We also propose a computationally efficient concatenation scheme. The rate achieved by our concatenated codes is characterized by a Zyablov-type lower bound. We provide a generalized minimum-distance decoding algorithm which decodes up to half the minimum distance of the concatenated codes. The end-to-end nature of our design enables our codes to be overlaid on the classical distributed random linear network codes. The other advantage of the end-to-end strategy over the link-by-link error-correction is that it reduces the computational cost at the internal nodes for performing error-correction.

  • 1882.
    Wang, Qiwen
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Skoglund, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Secure Private Information Retrieval from Colluding Databases with Eavesdroppers2018In: 2018 IEEE International Symposium on Information Theory (ISIT), Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 2456-2460Conference paper (Refereed)
    Abstract [en]

    The problem of private information retrieval (PIR) is to retrieve one message out of K messages replicated at N databases, without revealing the identity of the desired message to the databases. We consider the problem of PIR with colluding databases and eavesdroppers, named ETPIR. Specifically, any T out of N databases may collude, that is, they may communicate their interactions with the user to guess the identity of the requested message. An eavesdropper is curious to know the content of the messages and can tap in on the incoming and outgoing transmissions of any E databases with the user. The databases share some common randomness unknown to the eavesdropper and the user, and use the common randomness to generate the answers, such that the eavesdropper can learn no information about the K messages. The capacity is defined as the maximum retrieval rate, i.e. the number of information bits of the desired message retrieved per downloaded bit. In our previous work [1], we found that when Egeq T, the capacity equals 1-frac E N. In this work, we focus on the case when Eleq T. We find an outer bound (converse bound) and an inner bound (achievability) on the optimal achievable rate. The gap between the derived inner and outer bounds vanishes as the number of messages K tends to infinity.

  • 1883.
    Wang, Qiwen
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Symmetric private information retrieval for MDS coded distributed storage2017In: 2017 IEEE International Conference on Communications, ICC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7997029Conference paper (Refereed)
    Abstract [en]

    A user wants to retrieve a file from a database without revealing the identity of the file retrieved at the database, which is known as the problem of private information retrieval (PIR). If it is further required that the user obtains no information about the database other than the desired file, the concept of symmetric private information retrieval (SPIR) is introduced to guarantee privacy for both parties. In this paper, the problem of SPIR is studied for a database stored among N nodes in a distributed way, by using an (N, M)-MDS storage code. The information-theoretic capacity of SPIR, defined as the maximum number of information bits of the desired file retrieved per downloaded bit, for the coded database is derived. It is shown that the SPIR capacity for coded database is 1-M/N, when the amount of the shared common randomness of distributed nodes (unavailable at the user) is at least M/N-M times the file size. Otherwise, the SPIR capacity for the coded database equals zero.

  • 1884.
    Wang, Willy
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Evaluating the use of PXI modules in tests of a radio base station2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis project was carried out at the electromagnetic compatibility (EMC) department at Ericsson AB. One of the department’s goals is to seek a possible replacement to the box test instruments by utilizing PCI extension for instrumentation (PXI) modules. The main objective of this project is to evaluate how different PXI modules work during testing of a radio base station (RBS), in terms of performance, test time, and cost. A downlink decoder was implemented in LabVIEW with an extension called MathScript and several software test solutions were examined to measure error vector magnitude (EVM), frequency error, and power, and to perform parallel measurements in a multiple radio access technology (multi-RAT) test configuration. Moreover, several uplink tests were performed to decide if PXI modules are a suitable substitute for the previous box based test instruments. The findings from this study show that PXI modules can replace the previous box based test instruments. However it was concluded that not all areas can be covered and not all discrete test instrument can (yet) be replaced. Future work should complete the downlink decoder implementation in the field programmable gate array (FPGA) level in order to further improve the performance further. Future work should also examine if it is possible to replace all of the discrete test instruments with PXI modules.

  • 1885. Wang, X.
    et al.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Wang, L.
    Tornatore, M.
    Chung, H. S.
    Lee, H. H.
    Park, S. M.
    Mukherjee, B.
    Virtualized Cloud Radio Access Network for 5G Transport2017In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 55, no 9, p. 202-209, article id 8030505Article in journal (Refereed)
    Abstract [en]

    Current radio access networks (RANs) need to evolve to handle diverse service requirements coming from the growing number of connected devices and increasing data rates for the upcoming 5G era. Incremental improvements on traditional distributed RANs cannot satisfy these requirements, so the novel and disruptive concept of a cloud RAN (CRAN) has been proposed to decouple digital units (DUs) and radio units (RUs) of base stations (BSs), and centralize DUs into a central office, where virtualization and cloud computing technologies are leveraged to move DUs into the cloud. However, separating RUs and DUs requires low-latency and high-bandwidth connectivity links, called "fronthaul," as opposed to traditional backhaul links. Hence, design of the 5G transport network, that is, the part of the network that carries mobile data traffic between BSs and the core network and data centers, is key to meet the new 5G mobile service requirements and effectively transport the fronthaul traffic. Today, consensus is yet to be achieved on how the fronthaul traffic will be transported between RUs and DUs, and how virtualization of network resources will occur from a radio network segment to the centralized baseband processing units. In this article, we present a new 5G architecture, called virtualized cloud radio access network (V-CRAN), moving toward a cell-less 5G network architecture. We leverage the concept of a virtualized BS (V-BS) that can be optimally formed by exploiting several enabling technologies such as software defined radio (SDR) and coordinated multipoint (CoMP) transmission/reception. A V-BS can be formed on a per-cell basis or per-user basis by allocating virtualized resources on demand. For the fronthaul solution, our approach exploits the passive optical network (PON), where a wavelength can be dynamically assigned and shared to form a virtualized passive optical network (VPON). Several use cases of the V-CRAN are presented to show how network architecture evolution can enhance system throughput, energy efficiency, and mobility management.

  • 1886. Wang, X.
    et al.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Wang, L.
    Tornatore, M.
    Zhao, Y.
    Chung, H. S.
    Lee, H. H.
    Park, S.
    Mukherjee, B.
    Joint allocation of radio and optical resources in virtualized cloud RAN with CoMP2017In: 2016 IEEE Global Communications Conference, GLOBECOM 2016 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7841923Conference paper (Refereed)
    Abstract [en]

    5G Radio Access Networks (RANs) are supposed to increase their capacity by 1000x to handle growing number of connected devices and increasing data rates. The concept of cloud-RAN (CRAN) has been recently proposed to decouple digital units (DUs) and radio units (RUs) of base stations (BSs), and centralize DUs into central offices. CRAN can ease the implementation of advanced radio coordination techniques, e.g., Coordinated Multi-Point (CoMP) Transmission/Reception, to enhance its system throughput. However, separating DUs and RUs, and implementing CoMP in CRAN require low-latency and high-bandwidth connectivity links, called "fronthaul". Today, consensus has not yet been achieved on how BSs, fronthaul, and central offices will be orchestrated to enhance the system throughput. In this study, we present a CRAN over Passive Optical Network (PON) architecture called virtualized-CRAN (V-CRAN). V-CRAN leverages the concept of virtualized PON (VPON) that can dynamically associate any RU to any DU so that several RUs can be coordinated by the same DU, and the concept of virtualized BS (V-BS) that can jointly transmit common signals from multiple RUs to a user. We propose a novel mathematical model based on constraint programming for joint allocation of radio, optical network, and baseband processing resources to enhance RAN throughput, and we solve it by optimally forming VPONs and V-BSs. Comprehensive simulations show that V-CRAN can enhance the system throughput and the efficiency of resource utilization.

  • 1887. Wang, X.
    et al.
    Wang, L.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Tornatore, M.
    Figueiredo, G. B.
    Chung, H. S.
    Lee, H. H.
    Park, S.
    Mukherjee, B.
    Handover reduction in virtualized cloud radio access networks using TWDM-PON fronthaul2016In: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 8, no 12, p. B124-B134Article in journal (Refereed)
    Abstract [en]

    To meet challenging 5G capacity requirements, operators are densifying their cellular networks by deploying additional small cells to cover hot spots, and such an increase in the number and density of cells may result in excessive numbers of handovers. In this study, we propose a handover reduction mechanism implemented in a cloud radio access network (CRAN) by exploiting the high capacity of an optical access network serving as a "fronthaul." CRAN has been proposed as a 5G radio access network architecture, where the digital unit (DU) of a conventional base station (BS) is separated from the radio unit (RU) and moved to the "cloud" (DU-cloud) for better mobility management and cost saving. Separating RUs and DUs requires a low-latency and high-bandwidth 5G transport network to handle "fronthaul" traffic, for which optical access is an excellent choice. Here, we present a new 5G architecture, called virtualized-CRAN (V-CRAN), moving toward a cell-less 5G mobile network architecture. We leverage the concept of a "virtualized-BS" (V-BS) that can be formed by exploiting several enabling technologies such as software-defined radio and coordinated multipoint transmission/reception. A V-BS can be formed on a per-user basis by allocating virtualized resources on demand so that common signals can be jointly transmitted from multiple RUs to the user without triggering handover. We first model the handover reduction optimization problem for a scenario where future mobility information is known, and then propose a suite of algorithms for a scenario where future information is unknown. Simulation results show that V-CRAN can enhance the throughput of users at the cell-edge, as well as significantly reduce the number of handovers, handover delay, and failure rate.

  • 1888.
    Wang, Xiaoxin
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    3G HSDPA Performance In Mobile Internet Connections2004Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A key objective for 3G wireless networks, such as the Universal Mobile Telecommunication System (UMTS), is the explicit support for data communications for mobile users. Today, the dominant transport protocol in the Internet is the Transport Control Protocol (TCP). Since TCP was not tailored for wireless networks, there are some performance issues occurring when TCP traffic is transferred over a UMTS radio link.

    In this paper, the characteristics of TCP and UMTS are specified and the problems of TCP over UMTS dedicated channels (DCHs) are analyzed. The problem is high delays implying low utilization of allocated resources for small file transfers or due to packet losses. High Speed Downlink Packet Access (HSDPA)’s potential to solve the problem is studied. Since in HSDPA, High-Speed Downlink shared channel (HS-DSCH) is introduced as an alternative of DCH on downlink packet access, a model of HS-DSCH is built and simulations are performed in order to compare its TCP performance with DCH. The focus is on studying retransmission delay and Block Error Rate (BLER) targets. Some scheduling methods are also compared. The results indicate that HS-DSCH gives better TCP performance than a DCH, and that advanced scheduling methods gives similar result as round robin if there are packet losses. Moreover, a somewhat surprising result is found regarding fast retransmission and channel utilization for increasing BLER targets.

  • 1889.
    Wang, Y.
    et al.
    Xi'an Jiaotong University.
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Wang, X.
    Xi'an Jiaotong University.
    A Non-cooperative Scheme for SFR-Based Power Control in LTE Networks2014Conference paper (Refereed)
    Abstract [en]

    We propose a non-cooperative power allocation scheme for cellular systems using soft frequency reuse and in the power control, each user selfishly maximizes its utility.To find the tradeoff between QoS satisfaction and energy consumption, we design a utility function that considers both QoS requirements and the cost. We then show there exists a Nash equilibrium and provide conditions to assure its uniqueness. This scheme has limited signaling overhead and only pricing information needs to be exchanged among cells. Simulation results show that this scheme improves throughput and coverage performance compared with conventional SFR schemes.

  • 1890. Wang, Y.
    et al.
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Wang, X.
    Joint Interference Mitigation and Power Allocation for Multi-Cell LTE Networks: A Non-Cooperative Game Approach2014In: 2014 IEEE 80th Vehicular Technology Conference (VTC Fall), IEEE , 2014, p. 6966031-Conference paper (Refereed)
    Abstract [en]

    We propose a non-cooperative game-theoretic power allocation (NGPA) scheme for interference mitigation in long term evolution (LTE) uplink in this paper. We first set up the interference model employing conventional soft frequency reuse (SFR) scheme for inter-cell interference coordination (ICIC) in a nineteen-cell LTE network. Since each user may selfishly maximize its own performance in power allocation, we design a utility function that considers both quality of service (QoS) satisfaction and energy consumption. We then investigate the existence of Nash equilibrium and derive a sufficient condition to assure its uniqueness. Simulation results show that the proposed scheme improves throughput and coverage performances compared with conventional SFR schemes. Moreover, this scheme only requires limited signaling overhead among cells, which can be readily implemented in a distributed manner for practical systems.

  • 1891. Wang, Y.
    et al.
    Wei, Xiaoyu
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Timus, Bogdan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Sankar, R.
    Morgera, S.
    Feasibility study of pico cellular-relaying system in urban outdoor environment2011In: 2011 IEEE 12th Annual Wireless and Microwave Technology Conference, WAMICON, 2011Conference paper (Refereed)
    Abstract [en]

    Heterogeneous networks, in particular cellular-relaying networks, have the potential to provide high data-rate services at low infrastructure costs. Macro and micro base stations have traditionally been used to provide coverage and capacity, respectively. In this paper, we analyze a new approach in which coverage is provided by means of inband relays. We show that compared with a traditional network based on macro base stations, a good outdoor coverage for a target data rate could be provided in a more cost efficient way by deploying a network based on pico base stations and relays. However, this is valid only for low data-rate because part of the spectrum is allocated to the backhaul and therefore the capacity of cellular-relaying networks is typically limited. Moreover, this break-even point depends on how the networks are deployed.

  • 1892.
    Wang, Yuanshuang
    et al.
    Xi'an Jiaotong University.
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Wang, Xia
    Xi'an Jiaotong University.
    An Energy-Efficient Non-Cooperative Game Approach for Channel-Aware Distributed Medium Access Control2014In: 2014 IEEE 80th Vehicular Technology Conference (VTC Fall), IEEE , 2014, p. 1-6Conference paper (Refereed)
    Abstract [en]

    In this paper, an energy-efficient non-cooperative game approach is proposed for channel-aware distributed medium access control (EN-CDMAC) in slotted-Aloha systems, where users act selfishly to improve their own utilities. To resolve the network contention in a distributed manner, the capture model is employed and a pricing-based non-cooperative game scheme is designed to enable selfish users effectively achieve multi-user diversity by adjusting their equilibrium thresholds while guaranteeing fairness by the pricing mechanism. Then the existence of Nash equilibrium is proved, and the necessary and sufficient condition is derived to ensure its uniqueness. Furthermore, the equilibrium stability is investigated with stochastic process theory. Simulation results show that the proposed approach significantly improves the network throughput and delay performance without sacrificing energy efficiency compared to the conventional slotted-Aloha scheme. In particular, the proposed approach is more applicable for high-load systems.

  • 1893. Wang, Yujue
    et al.
    Hauser, Carl
    Wu, Yiming
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Quantifying Uncertainties of Security and QoS for Design of Power Grid Communications Systems2016In: 2016 49th Hawaii International Conference on System Sciences (HICSS), IEEE Computer Society, 2016, p. 2566-2575Conference paper (Refereed)
    Abstract [en]

    Reliable and secure communication, and high quality of service (QoS) (low latency, high availability, etc.) of data are critical to the successful operation of power systems. However, uncertainties, both aleatory and epistemic, are inherent to the system, which makes it difficult to secure the communication while fulfilling the QoS requirements. Nowadays, the administrators of the power grid's communication system have much flexibility in choosing a specific security scheme but the uncertainties make answering the question "what is the best scheme" or even "what is an adequate scheme" very difficult. Appropriately quantifying uncertainty and its effects on security is a key to choosing a sufficiently secure communication system for power grid while meeting QoS requirements. In this paper, we model aleatory and epistemic uncertainties using probability distributions and subjective logic respectively. Comprehensive quantification of the uncertainties can greatly sharpen administrators' understanding of the trade-offs between security and QoS and help them to select the most fitting security scheme to meet the QoS requirements. A case study demonstrates how our method works for two different application scenarios.

  • 1894. Wang, Z.
    et al.
    Chen, Xiaowen
    KTH, School of Information and Communication Technology (ICT), Electronics. National University of Defense Technology, China.
    Li, C.
    Guo, Y.
    Fairness-oriented and location-aware NUCA for many-core SoC2017In: 2017 11th IEEE/ACM International Symposium on Networks-on-Chip, NOCS 2017, Association for Computing Machinery (ACM), 2017, article id 13Conference paper (Refereed)
    Abstract [en]

    Non-uniform cache architecture (NUCA) is often employed to organize the last level cache (LLC) by Networks-on-Chip (NoC). However, along with the scaling up for network size of Systems-on-Chip (SoC), two trends gradually begin to emerge. First, the network latency is becoming the major source of the cache access latency. Second, the communication distance and latency gap between different cores is increasing. Such gap can seriously cause the network latency imbalance problem, aggravate the degree of non-uniform for cache access latencies, and then worsen the system performance. In this paper, we propose a novel NUCA-based scheme, named fairness-oriented and location-aware NUCA (FL-NUCA), to alleviate the network latency imbalance problem and achieve more uniform cache access. We strive to equalize network latencies which are measured by three metrics: average latency (AL), latency standard deviation (LSD), and maximum latency (ML). In FL-NUCA, the memory-to-LLC mapping and links are both non-uniform distributed to better fit the network topology and traffics, thereby equalizing network latencies from two aspects, i.e., non-contention latencies and contention latencies, respectively. The experimental results show that FL-NUCA can effectively improve the fairness of network latencies. Compared with the traditional static NUCA (SNUCA), in simulation with synthetic traffics, the average improvements for AL, LSD, and ML are 20.9%, 36.3%, and 35.0%, respectively. In simulation with PARSEC benchmarks, the average improvements for AL, LSD, and ML are 6.3%, 3.6%, and 11.2%, respectively.

  • 1895.
    Wang, Zhao
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Schaefer, Rafael F.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Poor, H. Vincent
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Strong Secrecy for Interference Channels from Channel Resolvability2015In: 2015 49th Asilomar Conference on Signals, Systems and Computers, IEEE Computer Society, 2015, p. 559-563, article id 7421191Conference paper (Refereed)
    Abstract [en]

    The achievable rate region is studied for interference channels with confidential messages under strong secrecy constraints. The problem is investigated based on the framework of the channel resolvability theory. The information-spectrum method introduced by Han and Verdu is first generalized to an arbitrary interference channel to obtain a direct channel resolvability result. The derived resolvability results are then shown to be the achievable strong secrecy rates for the stationary and memoryless interference channel. Our results provide further evidence that channel resolvability can be a powerful and general framework for strong secrecy analysis in multiuser networks.

  • 1896.
    Wang, Zhao
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Secrecy degrees of freedom of the 2 interference channel with delayed CSIT2014In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 3, no 4, p. 341-344, article id 6784143Article in journal (Refereed)
    Abstract [en]

    We consider the two-hop interference channel with confidential messages (ICC), where each transmitter sends one confidential message to its intended destination through two trusted relays. We study the secrecy degrees of freedom (SDoF) of the considered 2 ?2 ?2 ICC with delayed channel state information at transmitters (CSIT). We settle the optimal SDoF of the considered network to be (1/2, 1/2). Thus, the considered network has a strictly larger sum SDoF than a two-user one-hop ICC with even full CSIT. Moreover, we study the SDoF of the network with limited Shannon feedback, that only one relay can obtain the delayed CSIT and output feedback from the destinations. The optimal SDoF is also shown to be (1/2, 1/2), revealing that only limited feedback can also bring SDoF gain. Our proposed achievable schemes in both cases are integrated forms of the retrospective interference alignment and artificial noise transmission.

  • 1897.
    Wase, Ulrika
    KTH, Superseded Departments, Teleinformatics.
    Integration av Orbix och distributionen av objekt inom Ericsson Broadband System1996Independent thesis Advanced level (degree of Master (Two Years)), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    Distributed-object computing is distributed computing where objects, instead of processes, are the components of distribution. The most important part of distributed-object computing is an Object Request Broker (ORB) which handles all the practical things of communication.

    The most influential standardspecification of ORBs is CORBA (Common Object Request Broker Architecture). In CORBA an Interface Definition Language (IDL-language) is included. In this language one writes interfaces to objects. In that way the user of the object does not have to know the implementation, only the interface. On the market there are several implementations of CORBA and one of these is Orbix. Within the work with Ericsson Broadband System (EBS) an IDL-language and a kind of an ORB have been developed.

    In this master's thesis presentation a theoretical description of the above will be made. A proposal of how to implement a dialogue, the one that is described in the EBS dialogue concept, between one object in EBS and one in Orbix, will also be presented.

    The implementation proposal is described by the included files and their assignment, however the necessary code will not be presented.

  • 1898.
    Wazir, Omerjan
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Computer and Electronic Engineering.
    Frantsalis, Ioannis
    KTH, School of Technology and Health (STH), Medical Engineering, Computer and Electronic Engineering.
    Prestandautvärdering av Bluetooth och Wi-Fi för en smart hubb2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis has been carried out on behalf of the consulting company Seavus to re-duce cable usage in their office. Smart hubs (i.e. a central control unit) are made tomake usage of devices more effective.One problem is to decide between Bluetooth and Wi-Fi for communication betweenthe user and the smart hub. The choice may depend upon several factors such asbandwidth (throughput), jitter (variation in delay) and packet loss, which are im-portant parameters for assessing the quality of the communication channel.The HW-platform Raspberry Pi and compatible software was used as a measure-ment tool to test Bluetooth and Wi-Fi in different environments.The result showed that Wi-Fi is best suited for communication systems that requirehigh bandwidth and low jitter, and where high amount of packet loss is tolerable.Bluetooth is best suited for communication systems where low bandwidth and highjitter is tolerable, and minimal packet losses preferred.

  • 1899. Weeraddana, P. C.
    et al.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    On the Privacy of Optimization2017In: IFAC-PapersOnLine, ISSN 2405-8963, Vol. 50, no 1, p. 9502-9508Article in journal (Refereed)
    Abstract [en]

    In distributed or multiparty computations, optimization theory methods offer appealing privacy properties compared to cryptography and differential privacy methods. However, unlike cryptography and differential privacy, optimization methods currently lack a formal quantification of the privacy they can provide. The main contribution of this paper is to propose a quantification of the privacy of a broad class of optimization approaches. The optimization procedures generate a problem's data ambiguity for an adversarial observer, which thus observes the problem's data within an uncertainty set. We formally define a one-to-many relation between a given adversarial observed message and an uncertainty set of the problem's data. Based on the uncertainty set, a privacy measure is then formalized. The properties of the proposed privacy measure are analyzed. The key ideas are illustrated with examples, including localization and average consensus.

  • 1900.
    Wei, Li
    KTH, Superseded Departments, Teleinformatics.
    Gateway between Packet and Switched Networks for Speech Communication1994Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report is a result of a six month thesis work which was carried out and completed with the support of Ericsson Radio Systems AB in Kista, Stockholm. The purpose of this work was to connect the ordinary telephone world and the computer world by building a gateway between them. Since the hardware today is already qualified for such an idea, sofware construction including programming in Erland and C became the major task of the thesis. The system consists of an Ericsson MD110, an embedded computer as the gateway, programs supporting speech communication between workstations over an Ethernet LAN, speech communication between telephones attached to the MD110, and the speech communication between obe telephone and one workstation via the gateway.

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