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  • 151.
    BUDDA, SARATH CHANDRA REDDY
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    RATCHA, SREEKANTH
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Estimation of Direction of Arrival and Beamforming in Adaptive Array Antennas2005Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    In recent years there has been a rapid growth in the number of wireless users, particularly in the area of mobile communications. This rapid growth in mobile communications demands for more system capacity through efficient utilization of frequency spectrum and also keeping the Interference as low as possible. In today’s Radio resource management, Adaptive array antennas have an important role in increasing the system capacity and controlling the interference in mobile communications. Adaptive array antenna is an antenna system, which uses spatially separated antennas called array antennas and processes the received signals with a digital signal processor. Simply speaking these array antennas can reduce the co channel interference and effectively utilize the bandwidth by steering a high gain in the direction of interest and low gains in the undesired directions, technically this is called adaptive beamforming. This adaptive beamforming enables the base station to form narrow beam towards desired user and nulls towards the interfering user, hence improving the signal quality.

  • 152.
    Budda, Shiva Tarun
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Performance Analysis of Proxy based Encrypted communication in IoT environments: Security and Privacy ~ Distributed Systems Security2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 153.
    Bukhari, Syed Majid Ali Shah
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Khan, Inayat Ullah
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    SWOT Analysis of IP Multimedia Sub System Security Authentication Schemes2009Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    In this thesis we have accomplish SWOT analysis of IMS security authentication schemes for IMS network services. SWOT analysis for IMS security authentication schemes are divided into two main categories i.e. SIM based authentication and Non SIM based authentication. Analysis results provided strengths, weaknesses, opportunities and threats about an individual authentication scheme. The selection of authentication scheme is important for design and development within the MOBICOME project. SWOT analysis tool itself exhibit necessary information for advantages and disadvantages. The study holds significance, because of IMS deployment in the FMC environment to achieve seamless access to the services. The goal of the thesis was achieved by defining and selecting the most appropriate authentication schemes after conducting SWOT analysis in Chapters 5 & 6.

  • 154.
    Bunyakitanon, Monchai
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Peng, Mengyuan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Performance Measurement of Live Migration Algorithms2014Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    This thesis involves the area of virtualization. We have studied about improving load balancing in data center by using automated live migration techniques. The main idea is to migrate virtual machine(s) automatically from high loaded hosts to less loaded hosts with efficiency. The successful implementation can help administrator of data center maintain a load-balanced environment with less effort than before. For example, such a system can automatically identify hotspots and coldspots in a large data center and also decide which virtual machine to migrate, and which host should the machine be migrated to. We have implemented previously developed Push and Pull strategies on a real testbed for Xen and KVM. A new strategy, Hybrid, which is the combination of Push and Pull, has been created. All scripts applied in the experiments are Python-based for further integration to the orchestration framework OpenStack. By implementing the algorithms on a real testbed, we have solved a node failure problem in the algorithms, which was not detected previously through simulation. The results from simulation and those from testbed are similar. E.g. Push strategy has quick responses when the load is medium to high, while Pull strategy has quick responses when the load is low to medium. The Hybrid strategy behaves similar to Push strategy with high load and to Pull strategy with low load, but with greater number of migration attempts, and it responds quickly regardless to the load. The results also show that our strategies are able to handle different incidents such as burst, drain, or fluctuation of load over time. The comparison of results from different hypervisors, i.e., Xen and KVM, shows that both hypervisors conduct in the same way when applying same strategies in the same environment. It means the strategies are valid for both of them. Xen seems to be faster in improving the System performance. The migration attempts are similar, but KVM has much less Migrations over time than Xen with same scenario.

  • 155.
    Buqinca, Alban
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Zangana, Ala
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    TelMe Mobile2009Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    Dagens teknik har bidragit till att mobiltelefonens användningsområden har expanderat avsevärt de senaste åren. Detta har lett till att alltfler mobila tjänster har dykt upp på marknaden. Uppgiften i detta examensarbete består i att utveckla en version anpassad för mobiltelefoner av den existerande produkten TelMe, som är en webbtjänst för vikarietillsättning inom olika verksamheter. Den mobilanpassade versionen kommer att gå under namnet TelMe Mobile. Problemställningen var att implementera de väsentliga funktionerna i produkten med avsikt för att göra dessa tillgängliga för mobiltelefoner. För att hitta en lösning till problemställningen har följande frågeställningar formulerats; hur kan webbtjänsten TelMe anpassas till en mobiltelefon, hur kan innehållet presenteras i en mobiltelefon på ett användarvänligt sätt, hur kan dataflödet reduceras samt hur implementeras de tekniska lösningarna för TelMe Mobile? Eftersom utveckling för mobiltelefoner kräver ett helt annat tankesätt, samlades information om mobila webbapplikationer från officiella organisationer. Begränsningar i mobiltelefoner som t.ex. skärmstorlek, bandbredd och förhållandevis underlägsen hårdvara innebär att webbapplikationen måste vara enkel och inte resurskrävande. Med hänsyn till ovanstående restriktioner måste TelMe designas om och följa denna enkla struktur. Webbapplikationen måste ha en enkelkolumnig layout på grund av mobiltelefoners relativt mindre skärmstorlekar. På grund av den begränsade bandbredden och minneskapaciteten för mobiltelefoner är det viktigt att datamängden inte är för stor. För att reducera datamängden för varje sida måste antalet rader med information minskas. Användning av bilder för layouten kan bidra till en ökning av datamängden, därför bör mindre eller inga bilder utnyttjas. Den tekniska lösningen för TelMe Mobile har implementerats som en separat sida för mobiltelefoner medan TelMe är avsedd för datorer. Implementeringen genomfördes med hjälp av XHTML Mobile Profile 1.0 och eFrog Builder. W3C:s riktlinjer för mobil webbutveckling har följts för att säkerställa TelMe Mobiles kompatibilitet med ett brett utbud av mobiltelefoner. Kompatibiliteten kan dock inte garanteras med alla mobiltelefoner på grund av den breda variationen av mobila plattformar. TelMe Mobile har testats på ett antal olika mobiltelefoner med de vanligast förekommande plattformarna. Webbapplikationen har även testats på Opera Mini, som är en populär tredjepartswebbläsare med bra stöd för den mobila webben. Mobilvänligheten för TelMe Mobile har validerats på http://ready.mobi, vilket kontrollerar webbapplikationen gentemot W3C:s standarder för mobil webbutveckling.

  • 156. Burakowski, Wojciech
    et al.
    Krieger, Udo R.
    Leibnitz, Kenji
    Beben, Andrzej
    Meo, Michela
    Ors, Tolga
    Garcia-Vidal, Jorge
    Fiedler, Markus
    An overview on activities on wireless networks on the European project COST 2572000Konferensbidrag (Refereegranskat)
    Abstract [en]

    The paper summarises the work on wireless networks inside the COST 257 project, entitled “Impact of new services on the architecture and performance of broadband networks” and chaired by Prof. Tran-Gia of the Technical University of Wurzburg (Germany). This project was established for 4 years (1996-2000) and collected the researchers from 16 European countries represented by 32 organisations. Its topics are modelling, performance, network planning and the analysis of present and future wireless systems.

  • 157.
    Burke, Clive
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Implementation and Evaluation of Virtual Network Functions Performance in the Home Environment2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 158.
    Burra, Sudhir Kumar
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Yendrapalli, Reddy Prasad Reddy
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    User Scheduling Algorithm for MU-MIMO System with limited feedback2010Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    In conventional cellular systems, each base station (BS) transmits signals intended for a single user in a particular resource allocation. As bandwidth is a scarce resource, effective utilization of the available bandwidth in the system is essential in modern wireless systems especially for applications such as video streaming and voice over internet protocol (VoIP) which demands high data rate. Fortunately since the users feedback the channel state information to the network, there is an opportunity for the BS to schedule more than one users data in a single resource allocation by designing precoders which beamform the data to the intended user. This technique which is called multi-user multiple-input and multiple-output (MU-MIMO) is adopted in the evolving radio interface technologies. For properly utilizing the feedback information, scheduling algorithms are designed which selects pairs of users which would maximize system capacity. In this thesis we describe MU-MIMO technique with codebook based precoding that has been proposed for the IEEE 802.16m mobile broadband standard. A multi-user proportional fair (PF) scheduling algorithm is designed to improve both sum capacity and fairness among users.

  • 159.
    Byanyuma, Mastidia
    et al.
    Neslon Mandela African Institution of Science and Technology, TZA.
    Zaipuna, Yonah
    Neslon Mandela African Institution of Science and Technology, TZA.
    Simba, Fatuma
    University of Dar es Salaam, TZA.
    Trojer, Lena
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för teknik och estetik.
    Utilization of Broadband Connectivity in Rural and Urban-Underserved Areas: The case of Selected Areas in Arusha-Tanzania2018Ingår i: International Journal of Computing and Digital Systems, E-ISSN 2210-142X, Vol. 7, nr 2, s. 75-83Artikel i tidskrift (Refereegranskat)
    Abstract [en]

     Utilization is a key aspect in the management of any societal resource not only when it is scarce but in all cases to allow for optimum benefits to be accrued to everyone in the society. Internet bandwidth, which is a rare commodity especially in rural areas is hardly available where needed at the same cost and quality due to various reasons. Tanzania as a case study is among countries that have invested much in international, national and metro backbone networks, but still, there are areas without or with inadequate internet access services implying a significant utilization problem. In this paper, we present as a case study, the status of broadband connectivity in selected rural areas in Tanzania (Arusha) and the status is used to make recommendations for optimized utilization of installed capacity.

  • 160. Calderón González, Julian
    et al.
    Carmona Salazar, Òscar Daniel
    Image Enhancement with Matlab Algorithms2015Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 161. Carlsson, Patrik
    Multi-Timescale Modelling of Ethernet Traffic2003Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Ethernet är en av den vanligaste länk teknikerna, den används i lokala nätverk, trådlösa nätverk och stadsnätverk. Dock finns det en brist för trafikmodeller för Ethernet som är användbara i prestanda analys. I denna avhandling beskrivs en modell för Ethernet trafik. Modellen modellerar flera moment av bit intensiteten på flera tidsskalor. För att matcha modell parametrar mot mätt trafik så har fyra metoder utvecklats. När en modell har byggts, så kan den användas direkt i den stokastiska flödes modellen för prestanda beräkningar. Resultaten visar att när antalet källor ökar på en länk, så blir modellen bättre och mindre komplex.

  • 162. Carlsson, Patrik
    et al.
    Constantinescu, Doru
    Popescu, Adrian
    Fiedler, Markus
    Nilsson, Arne A.
    Delay Performance in IP Routers2004Konferensbidrag (Refereegranskat)
    Abstract [en]

    The main goals of the paper are towards an understanding of the delay process in best-effort Internet for both non-congested and congested networks. A dedicated measurement system is re-ported for delay measurements in IP routers, which follows specifications of the IETF RFC 2679. The system is using both passive measurements and active probing. Dedicated application-layer software is used to generate UDP traffic with TCP-like characteristics. Pareto traffic models are used to generate self-similar traffic in the link. The reported results are in the form of several impor-tant statistics regarding processing delay of a router, router delay for a single data flow, router delay for more data flows as well as end-to-end delay for a chain of routers. We confirm results reported earlier about the fact that the delay in IP routers is generally influenced by traffic characteristics, link conditions and, at some extent, details in hardware implementation and different IOS releases. The delay in IP routers usually shows heavy-tailed characteristics. It may also occasionally show extreme values, which are due to improper functioning of the routers.

  • 163. Carlsson, Patrik
    et al.
    Ekberg, Anders
    Fiedler, Markus
    On an Implementation of a Distributed Passive Measurement Infrastructure2003Övrigt (Övrigt vetenskapligt)
    Abstract [en]

    Having access to relevant, up-to-date measurement data is a key issue for network analysis in order to allow for efficient Internet performance monitoring and management. New applications keep appearing; user and protocol behavior keep evolving; traffic mixes and characteristics are continuously changing, which implies that some year old traffic traces may not reflect reality any more. In order to give a holistic view of what is going on in the network, passive measurements have to be carried out at different places simultaneously. Other challenges relate to the simultaneous use of one specific measurement point at a certain location for different measurement processes, and to continuously ongoing measurements needed for capturing long-term traffic behaviors. On this background, this paper proposes a passive measurement infrastructure for a campus backbone, consisting of distributed coordinated measurement points, collected in measurement areas, measurement administration and data management. … The framework is generic with regards to the capturing equipment, ranging from simple PCAP based devices to high-end DAG cards, and dedicated ASICs, in order to promote a large deployment of measurement points. This structure allows for an efficient use of passive monitoring equipment in order to supply researchers and network managers with up-to-date and relevant data.

  • 164. Carlsson, Patrik
    et al.
    Fiedler, Markus
    Multifractal Products of Stochastic Processes: Fluid Flow Analysis2000Konferensbidrag (Refereegranskat)
    Abstract [sv]

    I nätverks trafik så har multifraktala egenskaper uppmätts. Vi skapar processer med dessa egenskaper och använder sedan en fluid flow analys för att få fram prestanda mått.

  • 165. Carlsson, Patrik
    et al.
    Fiedler, Markus
    Nilsson, Arne A.
    Matching Multi-Fractal Process Parameters Against Real Data Traffic2002Konferensbidrag (Refereegranskat)
    Abstract [sv]

    Vi försöker matcha parametrar som hör till processer med multifraktala egenskaper. Vi försöker matcha mot verklig trafik.

  • 166. Carlsson, Patrik
    et al.
    Fiedler, Markus
    Nilsson, Arne A.
    Modelling of Ethernet Traffic on Multiple Timescales2004Konferensbidrag (Refereegranskat)
    Abstract [en]

    Ethernet is one of the most common link layer technologies, used in local area networks, wireless networks and wide area networks. There is however a lack of traffic models for Ethernet that is usable in performance analysis. In this paper we use such a model. The model operates on matching multiple moments of the bit rate at several timescales. In order to match the model parameters to measured traffic, five methods have been developed. We use this to model three different links; the BCpOct89 Bellcore trace, an Internet access link and an ADSL link. Our results show that, as the number of sources present on an Ethernet link grows, the model becomes better and less complex.

  • 167. Carlsson, Patrik
    et al.
    Fiedler, Markus
    Tutschku, Kurt
    Chevul, Stefan
    Nilsson, Arne A.
    Obtaining Reliable Bit Rate Measurements in SNMP-Managed Networks2002Konferensbidrag (Refereegranskat)
    Abstract [sv]

    Vi undersöker vilka problem som kan finnas när man använder SNMP för att mäta prestanda i ett nätverk.

  • 168.
    Carlsson, Viktor
    et al.
    Blekinge Tekniska Högskola, Sektionen för management.
    Lindskog, Magnus
    Blekinge Tekniska Högskola, Sektionen för management.
    Kritiska Prestations Indikatorer (KPI), Hur väl fungerar KPI:er som verksamhetsstyrning inom den producerande industrin?2012Självständigt arbete på grundnivå (kandidatexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    The purpose of this thesis is to examine how key performance indicators are being used as performance management tools within the production industry. Specifically the purpose is to investigate how the KPI:s within the telecommunications industry drives reusability regarding production test systems. This thesis will also highlight today’s cost models and suggest improvements of the KPI and what new ones could be introduced. A case study at Ericsson AB has been performed. The study has an abductive approach because the study is both based on current theories and hypotheses but also from empirical data. Personal interviews were also conducted at HWDSS, Ericsson AB. The conclusion of this case study is that the management control measurements used today, to some extent creates incentives for modular design with high reusability. However, there is room for improvements, both in order to more clearly show the positive effects with high reusability and to more directly control the activity toward this goal. It’s our belief that better monitoring of the proportion of previous modules/components being used in new designs and to have a target value for this part clearly would promote modular design with high reusability. It’s also important to continuously measure the enablers for the goal and not just follow the implementation of identified key activities. KPI, PI and cost models of the business must always be up to date and pointing in the direction of the business laid strategy.

  • 169.
    Carmona, Manuel Bejarano
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    A simple and low cost platform to perform Power Analysis Attacks2012Studentuppsats (Examensarbete)
    Abstract [en]

    Power Analysis Attacks use the fact that power consumption in modern microprocessors and cryptographic devices depends on the instructions executed on them and so, it varies with time. This leak- age is mainly used to deduce cryptographic keys as well as algorithms by direct observation of power traces. Power Analysis is a recent field of study that has been developed for the last decade. Since then, the techniques used have evolved into more complex forms, that some- times require a variety of skills that makes the subject difficult to start with. Nowadays it is changeling to tackle the problem without expen- sive equipment; what is more, the off-the-shelf solutions to do Power Analysis Attacks are rare and expensive. This thesis aim to provide a low cost and open platform as an entry point to Power Analysis for a price under 10 USD. Besides that, it is designed to be able to per- form Simple Power Analysis and Differential Power Analysis attacks to a 8 bit microcontroller, including the software needed to automate the process of taking the measurements. Finally, the platform can be extended to cover a wide range of microcontrollers, microprocessors and cryptographic devices by simple insertion in a bread board, which makes it the perfect device for new comers to the field.

  • 170.
    Cedergren, Joakim
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Assisted GPS for Location Based Services2005Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    The mobile operators are seeking for opportunities to create differentiation and increase profit. One powerful way is to provide personalized mobile services. A good example of personalisation is by location. Services based on position are called Location Based Services – LBS. To realise LBS, some sort of positioning method is needed. The two most common positioning methods today are Global Positioning System - GPS and network based positioning. GPS is not fully suited for LBS because you need an additional handset to receive the satellite signals. In network positioning however, you only need a mobile phone, but on the other hand, the accuracy is far less, only between 100 metres up to several kilometres. What technology would be a good positioning technology for location based services? Could A-GPS be such technology? A-GPS is a positioning system which uses the same satellites as GPS, but besides that, it also uses a reference network. The reference network tracks the receiver and the satellites. It also makes some of the heavy calculations that the handsets are doing in the GPS system. That makes the A-GPS receivers less power consuming and more suited to be implemented into mobile phones. Furthermore, A-GPS are more sensitive, meaning that it easier can receive signals when using indoor, for example. The question is if A-GPS technology holds its promises? Does A-GPS really work well in mobile phones? Is the accuracy and availability as good as the theory says and is it possible to implement an own, well working, location based service into an A-GPS mobile phone?

  • 171.
    Chakraborty, Joyraj
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Jampana, Venkata Krishna chaithanya varma.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    ANFIS BASED OPPURTUNISTIC POWER CONTROL FOR COGNITIVE RADIO IN SPECTRUM SHARING2013Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Cognitive radio is a intelligent technology that helps in resolving the issue of spectrum scarcity. In a spectrum sharing network, where secondary user can communicate simultaneously along with the primary user in the same frequency band, one of the challenges in cognitive radio is to obtain balance between two conflicting goals that are to minimize the interference to the primary users and to improve the performance of the secondary user. In our thesis we have considered a primary link and a secondary link (cognitive link) in a fading channel. To improve the performance of the secondary user by maintaining the Quality of Service (Qos) to the primary user, we considered varying the transmit power of the cognitive user. Efficient utilization of power in any system helps in improving the performance of that system. For this we proposed ANFIS based opportunistic power control strategy with primary user’s SNR and primary user’s channel gain interference as inputs. By using fuzzy inference system, Qos of primary user is adhered and there is no need of complex feedback channel from primary receiver. The simulation results of the proposed strategy shows better performance than the one without power control. Initially we have considered propagation environment without path loss and then extended our concept to the propagation environment with path loss where we have considered relative distance between the links as one of the input parameters.

  • 172.
    Chakraborty, Joyraj
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    J.V.K.C., Varma
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Erman, Maria
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    ANFIS based Opportunistic power control for cognitive radio in spectrum sharing2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cognitive radio is an intelligent technology that helps in resolving the issue of spectrum scarcity. In a spectrum sharing network, where secondary user can communicate simultaneously along with the primary user in the same frequency band, one of the challenges is to obtain balance between two conflicting goals that are to minimize the interference to the primary users and to improve the performance of the secondary user. In our paper we have considered a primary link and a secondary link (cognitive link) in a fading channel. To improve the performance of the secondary user by maintaining the Quality of Service (Qos) to the primary user, we considered varying the transmit power of the cognitive user. For this we proposed ANFIS based opportunistic power control strategy with primary user's SNR and primary user's interference channel gain as inputs. By using fuzzy inference system, Qos of primary user is adhered and there is no need of complex feedback channel from primary receiver. The simulation results of the proposed strategy shows better performance than the one without power control.

  • 173.
    Chalamalasetty, Kalyani
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Architecture for IMS Security to Mobile:Focusing on Artificial Immune System and Mobile Agents Integration2009Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    The IP Multimedia Subsystem (IMS) is an open IP based service infrastructure that enables an easy deployment of new rich multimedia services mixing voice and data. The IMS is an overlay network on top of IP that uses SIP as the primary signaling mechanism. As an emerging technology, the SIP standard will certainly be the target of Denial of Service (DoS) attacks and consequently IMS will also inherit this problem. The objective of proposed architecture for IMS is to cram the potential attacks and security threats to IP Multimedia Subsystem (IMS) and explore the security solutions developed by 3GPP. This research work incorporates the ideas of immune system and multiagent architecture that is capable of detecting, identifying and recovering from an attack. The proposed architecture protects IMS core components i.e. P-CSCF (Proxy- Call Session Control Function), I-CSCF (Interrogating-Call Session Control Function), S-CSCF (Serving Call Session Control Function) and HSS (Home Subscriber Server) from external and internal threats like eavesdropping, SQL injection and denial-ofservice (DoS) attacks. In the first level i.e. CPU under normal load all incoming and out going messages were investigated to detect and prevent SQL injection. Second level considers Denial of Service (DOS) attacks when CPU load exceeds threshold limit. Proposed architecture is designed and evaluated by using an approach called Architecture Tradeoff Analysis Method (ATAM). The results obtained confirm consistency of the architecture.

  • 174.
    Chapala, Usha Kiran
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datavetenskap.
    Peteti, Sridhar
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datavetenskap.
    Continuous Video Quality of Experience Modelling using Machine Learning Model Trees1996Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Adaptive video streaming is perpetually influenced by unpredictable network conditions, whichcauses playback interruptions like stalling, rebuffering and video bit rate fluctuations. Thisleads to potential degradation of end-user Quality of Experience (QoE) and may make userchurn from the service. Video QoE modelling that precisely predicts the end users QoE underthese unstable conditions is taken into consideration quickly. The root cause analysis for thesedegradations is required for the service provider. These sudden changes in trend are not visiblefrom monitoring the data from the underlying network service. Thus, this is challenging toknow this change and model the instantaneous QoE. For this modelling continuous time, QoEratings are taken into consideration rather than the overall end QoE rating per video. To reducethe user risk of churning the network providers should give the best quality to the users.

    In this thesis, we proposed the QoE modelling to analyze the user reactions change over timeusing machine learning models. The machine learning models are used to predict the QoEratings and change patterns in ratings. We test the model on video Quality dataset availablepublicly which contains the user subjective QoE ratings for the network distortions. M5P modeltree algorithm is used for the prediction of user ratings over time. M5P model gives themathematical equations and leads to more insights by given equations. Results of the algorithmshow that model tree is a good approach for the prediction of the continuous QoE and to detectchange points of ratings. It is shown that to which extent these algorithms are used to estimatechanges. The analysis of model provides valuable insights by analyzing exponential transitionsbetween different level of predicted ratings. The outcome provided by the analysis explains theuser behavior when the quality decreases the user ratings decrease faster than the increase inquality with time. The earlier work on the exponential transitions of instantaneous QoE overtime is supported by the model tree to the user reaction to sudden changes such as video freezes.

  • 175.
    Chatlapalle, S S Sampurna Akhila
    Blekinge Tekniska Högskola.
    Generic Deployment Tools for Telecom Apps in Cloud2018Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 176.
    Chaudhry, Fazal-e-Abbas
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Speaker Separation Investigation2007Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    This report describes two important investigations which formed part of an overall project aimed at separating overlapping speech signals. The first investigation uses chirp signals to measure the acoustic transfer functions which would typically be found in the speaker separation project. It explains the behaviour of chirps in acoustic environments that can be further used to find the room reverberations as well, besides their relevance to measuring the transfer functions in conjunction with speaker separation. Chirps that have been used in this part are logarithmic and linear chirps. They have different lengths and are analysed in two different acoustic environments. Major findings are obtained in comparative analysis of different chirps in terms of their cross-correlations, specgrams and power spectrum magnitude. The second investigation deals with using automatic speech recognition (ASR) system to test the performance of the speaker separation algorithm with respect to word accuracy of different speakers. Speakers were speaking in two different scenarios and these were nonoverlapping and overlapping scenarios. In non-overlapping scenario speakers were speaking alone and in overlapping scenario two speakers were speaking simultaneously. To improve the performance of speaker separation in the overlapping scenario, I was working very close with my fellow colleague Mr. Holfeld who was improving the existing speech separation algorithm. After cross-examining our findings, we improved the existing speech separation algorithm. This further led to improvement in word accuracy of the speech recognition software in overlapping scenario.

  • 177.
    CHAVALI, SRIKAVYA
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem. Select...
    AUTOMATION OF A CLOUD HOSTED APPLICATION: Performance, Automated Testing, Cloud Computing2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Context: Software testing is the process of assessing quality of a software product to determine whether it matches with the existing requirements of the customer or not. Software testing is one of the “Verification and Validation,” or V&V, software practices. The two basic techniques of software testing are Black-box testing and White box testing. Black-box testing focuses solely on the outputs generated in response to the inputs supplied neglecting the internal components of the software. Whereas, White-box testing focuses on the internal mechanism of the software of any application. To explore the feasibility of black-box and white-box testing under a given set of conditions, a proper test automation framework needs to be deployed. Automation is deployed in order to reduce the manual effort and to perform testing continuously, thereby increasing the quality of the product.

     

    Objectives: In this research, cloud hosted application is automated using TestComplete tool. The objective of this thesis is to verify the functionality of Cloud application known as Test data library or Test Report Analyzer through automation and to measure the impact of the automation on release cycles of the organization.

     

    Methods: Here automation is implemented using scrum methodology which is an agile development software process. Using scrum methodology, the product with working software can be delivered to the customers incrementally and empirically with updating functionalities in it. Test data library or Test Report Analyzer functionality of Cloud application is verified deploying testing device thereby the test cases can be analyzed thereby analyzing the pass or failed test cases.

     

    Results: Automation of test report analyzer functionality of cloud hosted application is made using TestComplete and impact of automation on release cycles is reduced. Using automation, nearly 24% of change in release cycles can be observed thereby reducing the manual effort and increasing the quality of delivery.

     

    Conclusion: Automation of a cloud hosted application provides no manual effort thereby utilization of time can be made effectively and application can be tested continuously increasing the efficiency and the quality of an application.

  • 178.
    Chebudie, Abiy Biru
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Monitoring of Video Streaming Quality from Encrypted Network Traffic: The Case of YouTube Streaming2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The video streaming applications contribute to a major share of the Internet traffic. Consequently, monitoring and management of video streaming quality has gained a significant importance in the recent years. The disturbances in the video, such as, amount of buffering and bitrate adaptations affect user Quality of Experience (QoE). Network operators usually monitor such events from network traffic with the help of Deep Packet Inspection (DPI). However, it is becoming difficult to monitor such events due to the traffic encryption. To address this challenge, this thesis work makes two key contributions. First, it presents a test-bed, which performs automated video streaming tests under controlled time-varying network conditions and measures performance at network and application level. Second, it develops and evaluates machine learning models for the detection of video buffering and bitrate adaptation events, which rely on the information extracted from packets headers. The findings of this work suggest that buffering and bitrate adaptation events within 60 second intervals can be detected using Random Forest model with an accuracy of about 70%. Moreover, the results show that the features based on time-varying patterns of downlink throughput and packet inter-arrival times play a distinctive role in the detection of such events.

  • 179.
    Cheema, Rukhsar Ahmad
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Irshad, Muhammad Jehanzeb
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Issues and Optimization of UMTS Handover2009Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    UMTS is an emerging cell phone technology and it is basically another name for 3G mobile communication systems. It provides an enhanced range of multimedia services like video conferencing and high speed internet access. Sometimes UMTS is marketed as 3GSM emphasizing the both 3G nature and GSM standards which it was designed to succeed. UMTS is also European term for wireless systems based on the IMT-2000 standards. To utilize various merits in mobile telecommunication system which consist of various radio access networks, UMTS as Third Generation wireless technology utilizes a wideband CDMA or TD/CDMA transceiver and also cover large area. Handover is basically a function which continues the communication between users without any gaps when the hardware goes to a place where it finds no network coverage. When we talk in terms of cellular communications systems, handover is a process which is referred to the transfer of a connection from one cell to another. Handover time is generally between 200 and 1,200 milliseconds (ms), which accounts for the delay. In this thesis we are going to find the reasons for these factors which affect the Quality of service of handover. The main focus of this research is to study the some factors which really affect the handover phenomenon in UMTS that basically affect the overall quality of mobile network. For this we intend to find the solution for problems which born during the handover. Handover provides the mobility to users which are the main theme of wireless technology and it is also make the interoperability between different network technologies.

  • 180. Chen, Hong
    et al.
    Nie, Zedong
    Ivanov, Kamen
    Wang, Lei
    Liu, Ran
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    A statistical MAC protocol for heterogeneous-traffic human body communication2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    In wireless body sensor networks (WBSN) and wireless body area networks (WBAN), sensor nodes have different bandwidth requirements, therefore, heterogeneous traffic is created. In this paper, we propose a statistical medium access control (MAC) protocol with periodic synchronization for use in heterogeneous traffic networks based on human body communication (HBC). The MAC protocol is designated to ensure energy efficiency by means of flexible time slot allocation and a statistical frame. The statistical frame is intended to increase the sleep time and keep low duty cycles in each beacon period. The MAC protocol was fully implemented on our HBC platform. The experimental results proved that the proposed MAC protocol is compact and energy-efficient.

  • 181.
    CHETACHI, UMUNNA CHRISTIAN CHEZZ
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Security and Performance Analysis of Topology-Based Intrusion Detection System in Ad Hoc Networks2009Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    Som Trådlöst ad-hoc-nätverk blir en allt mer framväxande teknik med en central plats i spännande forskningsområden som har lockat många forskning uppmärksamhet i kommunikationssystem, behovet av effektiva intrångslarm detekteringsmetoder att förbättra nät-säkerhet och integritet har fått betydande utrymme. För upptäckt av intrång system (IDS) i ad hoc-nät ger en effektiv metod för att förbättra säkerhet, energieffektivitet för avsändande noder som möjliggör bättre fysisk återanvändning av trådlös kanal och kontroll över nätverkets resurser för att optimera nod säkerhet och överföra makt därigenom bibehålla nätverksanslutning. Men dessa globala egenskaper har förfalskats på grund av brist på lämpliga Intrusion Detection System som leder till svår nätverk misslyckanden som är bane för nästa generation ad hoc-nät. I denna avhandling har vi undersöka några trådlösa ad hoc-säkerhet attacker och svagheter i förhållande till topologi kontrollera och utvärdera deras resultat under fientliga miljöer. Vi föreslår en ny Distributed Intrusion Detection System (DIDS) som innefattar regel-baserade kluster topologi betydelse för både trådlösa sensornätverk (WSNs) och Mobile ad hoc-nätverk (MANETs) för att fastställa deras säkerhet och prestanda i ansökan specifika miljöer. Vår DIDS drar slutsatser av intrång genom att jämföra avvikande mönster från paketkoppling spår av sända och ta emot signalen befogenheter, förhållandet paketkoppling ankomst priser och brist på radiomottagare paketkoppling makten tröskelvärden använder buffert fönster räkna. Därför utvärderar vi våra intrångslarm upptäckt mekanismen för en jammer attack och observera effekten på nätet genomströmning. Vår inställning är simuleras med hjälp av OPNET ® simulator. Simulering Resultaten visar att detekteringskapaciteten av våra system under en Denial of Service (DoS) (jammer) attack, ökar bit felfrekvenser, ökade överlämna dröjsmål svaren och betydande minskning i både signal-brus befogenheter och den genomsnittliga nät kapacitet på grund till förekomsten av jammer attack som ligger till grund för vår analys krävs för att upprätthålla effektiv energianvändning och förbättra säkerheten i ad hoc-nätverk.

  • 182. Chevul, Stefan
    On Application-Perceived Quality of Service in Wireless Networks2006Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Wireless and Mobile Internet have changed the way people and businesses operate. Communication from any Internet access point, including wireless networks such as UMTS, GPRS or WLAN has enabled organizations to have a mobile workforce. However, networked applications such as web, email, streaming multimedia etc. rely upon the ability of timely data delivery. The achievable throughput is a quality measure for the very task of a communication system, which is to transport data in time. Throughput is thus one of the most essential enablers for networked applications. While in general, throughput is defined on network or transport level, the application-perceived throughput reflects the Quality of Service from the viewpoints of the application and user. The focus of the thesis is on the influence of the network on the applicationperceived Quality of Service and thus the user perceived experience. An analysis of application based active measurements mimicking the needs of streaming applications is presented. The results reveal clear influence of the network on the application-perceived Quality of Service seen from variations of application-perceived throughput on small time scales. Results also indicate that applications have to cope with considerably large jitter when trying to use the nominal throughputs. It was observed that the GPRS network had considerable problems in delivering packets in the downstream direction even when the nominal capacity of the link was not reached. Finally, the thesis discusses the suitability of wireless networks for different mobile services, since the influence of the network on the application-perceived Quality of Service is of great significance when it comes to customer satisfaction. Therefore, application-perceived Quality of Service in wireless networks must also be considered by the mobile application programmer during the application development.

  • 183. Chevul, Stefan
    et al.
    Isaksson, Lennart
    Fiedler, Markus
    Karlsson, Johan
    Lindberg, Peter
    Measurement of application-perceived throughput of an E2E VPN connection using a GPRS network2005Konferensbidrag (Refereegranskat)
    Abstract [sv]

    Vi identifierar orsaker varför VPN fungerar dåligt via GPRS

  • 184. Chevul, Stefan
    et al.
    Isaksson, Lennart
    Fiedler, Markus
    Lindberg, Peter
    Waltersson, Roland
    Network Selection Box: An Implementation of Seamless Communication2006Konferensbidrag (Refereegranskat)
    Abstract [sv]

    Pappret beskriver nätverksvalboxen (Network Selection Box) som togs fram inom VINNOVA-sponsrade projektet PIITSA och som implementerar en äkt end-till-end lösning för sömlös kommunikation. Network Selection Box, sömlös kommunikation, automatiskt nätverksval, tjänstekvalitet, säkerhet, kostnad, implementering, QoS

  • 185. Chevul, Stefan
    et al.
    Karlsson, Johan
    Isaksson, Lennart
    Fiedler, Markus
    Lindberg, Peter
    Strandén, Lars
    Measurements of Application-Perceived Throughput in DAB, GPRS, UMTS and WLAN Environments2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    Communication services are expected to deliver the desired information in a timely manner without challenging the user’s patience. The corresponding offers by networks are reflected in user- or applications-perceived throughput, which is measured end-to-end for different mobile and wireless networks, namely Digital Audio Broadcast (DAB), General Packet Radio Service (GPRS), Universal Mobile Telecommunication Systems (UMTS), and Wireless Local Area Networks (WLAN). The measurements are based on passive monitoring of throughput statistics for active test traffic and reveal amongst others different kinds of changes of traffic burstiness induced by mobile up- and downlinks and by buffering, respectively. The results will be used for seamless communication, i.e. automatic network selection within the project PIITSA (Personal Information for Intelligent Transport Systems through Seamless communications and Autonomous decisions) aiming at maintaining user-perceived performance and security at the desired levels while keeping communication cost as small as possible.

  • 186.
    Chilukuri, Megh Phani Dutt
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Power Profiling of Network Switches2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Context In the present world, there is an increase in the usage of the telecommunication networking services, as there is a need of efficient networking services in various fields which can be obtained by using the efficient networking components. For that purpose we have to know about the components parameters. One of the most important parameter is the energy usage of networking components. Therefore, there is a need in power profiling of the network switches.

    Objectives The objective of this research is to profile the power usage of different network components(Switches) for various load scenarios. Power measurements are done by using the open energy monitoring tool called emonpi.

    Methods The research method has been carried out by using an experimental test bed. In this research, we are going to conduct the experiments with different configurations to obtain different load conditions for sources and destinations which will be passed through DUT(Device Under Test). For that DUT’s we will measure power usage by monitoring tool called emonpi. Then the experiments are conducted for different load scenarios for different switches and results are discussed.

    Conclusion From the results obtained, the Power profiles of different DUT’s are tabulated and analyzed. These were done under different ports and load scenarios for Cisco2950, Cisco3560 and Netgear GS-724T. From the results and analysis it can be stated that the power usage of Cisco 2950 is having the maximum power usage in all the considered scenarios with respect to packet rate and also number of active ports. The Netgear-GS724T is having the minimum power usage from the three switches as it having the green switch characteristics in all scenarios. And the Cisco 3560 is in between the above two switches as it is having energy efficient management from Cisco. From this we have proposed a simple model for energy/power measurement.

  • 187.
    Chowdhury, Moyamer
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Alam, Aminul
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Study Comparison of WCDMA and OFDM2007Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Wideband Code Division Multiple Access (WCDMA) is one of the main technologies for the implementation of third-generation (3G) cellular systems. It is based on radio access technique proposed by ETSI Alpha group and the specifications was finalised 1999. WCDMA is also known as UMTS and has been adopted as a standard by the ITU under the name “IMT-2000 direct spread”. The implementation of WCDMA will be a technical challenge because of its complexity and versatility. The complexity of WCDMA systems can be viewed from different angles: the complexity of each single algorithm, the complexity of the overall system and the computational complexity of a receiver. In WCDMA interface different users can simultaneously transmit at different data rates and data rates can even vary in time. WCDMA increases data transmission rates in GSM systems by using the CDMA air interface instead of TDMA. WCDMA is based on CDMA and is the technology used in UMTS. WCDMA is the dominating 3G technology, providing higher capacity for voice and data and higher data rates. The gradual evolution from today's systems is driven by demand for capacity, which is required by new and faster data based mobile services. WCDMA enables better use of available spectrum and more cost-efficient network solutions. The operator can gradually evolve from GSM to WCDMA, protecting investments by re-using the GSM core network and 2G/2.5G services. Orthogonal Frequency Division Multiplexing (OFDM) - technique for increasing the amount of information that can be carried over a wireless network uses an FDM modulation technique for transmitting large amounts of digital data over a radio wave. OFDM works by splitting the radio signal into multiple smaller sub-signals that are then transmitted simultaneously at different frequencies to the receiver. OFDM reduces the amount of crosstalk in signal transmissions. 802.11a WLAN, 802.16 and WiMAX technologies use OFDM. It's also used in the ETSI's HiperLAN/2 standard. In addition, Japan's Mobile Multimedia Access Communications (MMAC) WLAN broadband mobile technology uses OFDM. In frequency-division multiplexing, multiple signals, or carriers, are sent simultaneously over different frequencies between two points. However, FDM has an inherent problem: Wireless signals can travel multiple paths from transmitter to receiver (by bouncing off buildings, mountains and even passing airplanes); receivers can have trouble sorting all the resulting data out. Orthogonal FDM deals with this multipath problem by splitting carriers into smaller subcarriers, and then broadcasting those simultaneously. This reduces multipath distortion and reduces RF interference allowing for greater throughput. In this paper we have discussed about these two methods of third generation radio transmission system which are WCDMA and OFDM with various aspects. In between these two radio transmission technique, a better choice will be investigated.

  • 188.
    Chowdhury, Moyamer
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Alam, Aminul
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Study Comparison of WCDMA and OFDM2007Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Wideband Code Division Multiple Access (WCDMA) is one of the main technologies for the implementation of third-generation (3G) cellular systems. It is based on radio access technique proposed by ETSI Alpha group and the specifications was finalised 1999. WCDMA is also known as UMTS and has been adopted as a standard by the ITU under the name “IMT-2000 direct spread”. The implementation of WCDMA will be a technical challenge because of its complexity and versatility. The complexity of WCDMA systems can be viewed from different angles: the complexity of each single algorithm, the complexity of the overall system and the computational complexity of a receiver. In WCDMA interface different users can simultaneously transmit at different data rates and data rates can even vary in time. WCDMA increases data transmission rates in GSM systems by using the CDMA air interface instead of TDMA. WCDMA is based on CDMA and is the technology used in UMTS. WCDMA is the dominating 3G technology, providing higher capacity for voice and data and higher data rates. The gradual evolution from today's systems is driven by demand for capacity, which is required by new and faster data based mobile services. WCDMA enables better use of available spectrum and more cost-efficient network solutions. The operator can gradually evolve from GSM to WCDMA, protecting investments by re-using the GSM core network and 2G/2.5G services. Orthogonal Frequency Division Multiplexing (OFDM) - technique for increasing the amount of information that can be carried over a wireless network uses an FDM modulation technique for transmitting large amounts of digital data over a radio wave. OFDM works by splitting the radio signal into multiple smaller sub-signals that are then transmitted simultaneously at different frequencies to the receiver. OFDM reduces the amount of crosstalk in signal transmissions. 802.11a WLAN, 802.16 and WiMAX technologies use OFDM. It's also used in the ETSI's HiperLAN/2 standard. In addition, Japan's Mobile Multimedia Access Communications (MMAC) WLAN broadband mobile technology uses OFDM. In frequency-division multiplexing, multiple signals, or carriers, are sent simultaneously over different frequencies between two points. However, FDM has an inherent problem: Wireless signals can travel multiple paths from transmitter to receiver (by bouncing off buildings, mountains and even passing airplanes); receivers can have trouble sorting all the resulting data out. Orthogonal FDM deals with this multipath problem by splitting carriers into smaller subcarriers, and then broadcasting those simultaneously. This reduces multipath distortion and reduces RF interference allowing for greater throughput. In this paper we have discussed about these two methods of third generation radio transmission system which are WCDMA and OFDM with various aspects. In between these two radio transmission technique, a better choice will be investigated.

  • 189.
    Chu, Thi My Chin
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Phan, Hoc
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    MIMO Incremental AF Relay Networks with TAS/MRC and Adaptive Modulation2013Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    In this paper, we study the use of adaptive modulation (AM) for a dual-hop multiple-input multiple-output (MIMO) network with transmit antenna selection (TAS) at the transmitter and maximal ratio combining (MRC) at the receiver. Our system deploys incremental amplify-and-forward (AF) relaying with AM to forward the source signal. A switching policy for selecting between the relaying and the direct communication is utilized to maximize spectrum efficiency. In particular, we derive closed-form expressions for the outage probability, spectrum efficiency, and bit error rate (BER) for the considered system over Nakagami-m fading. The considered network not only takes advantage of TAS transmission such as achieving full diversity order with low transmit complexity but also inherits the beneficial feature of AM such as spectrum efficiency improvement. Reference

  • 190.
    Chu, Thi My Chin
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kreativa teknologier.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kreativa teknologier.
    On Capacity of Full-Duplex Cognitive Cooperative Radio Networks with Optimal Power Allocation2017Ingår i: 2017 IEEE WIRELESS COMMUNICATIONS AND NETWORKING CONFERENCE (WCNC), IEEE , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we examine a full-duplex transmission scheme for cognitive cooperative radio networks (CCRNs) to improve capacity. In this network, the secondary transmitter and secondary relay are allowed to utilize the licensed spectrum of the primary user by using underlay spectrum access. We assume that the CCRN is subject to the interference power constraint of the primary receiver and maximum transmit power limit of the secondary transmitter and secondary relay. Under these constraints, we propose an optimal power allocation policy for the secondary transmitter and the secondary relay based on average channel state information (CSI) to optimize capacity. Then, we derive an expression for the corresponding achievable capacity of the secondary network over Nakagami-m fading. Numerical results are provided for several scenarios to study the achievable capacity that can be offered by this full-duplex underlay CCRN using the proposed optimal power allocation scheme.

  • 191.
    Chu, Thi My Chinh
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    On the Performance Assessment of Advanced Cognitive Radio Networks2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Due to the rapid development of wireless communications together with the inflexibility of the current spectrum allocation policy, radio spectrum becomes more and more exhausted. One of the critical challenges of wireless communication systems is to efficiently utilize the limited frequency resources to be able to support the growing demand of high data rate wireless services. As a promising solution, cognitive radios have been suggested to deal with the scarcity and under-utilization of radio spectrum. The basic idea behind cognitive radios is to allow unlicensed users, also called secondary users (SUs), to access the licensed spectrum of primary users (PUs) which improves spectrum utilization. In order to not degrade the performance of the primary networks, SUs have to deploy interference control, interference mitigating, or interference avoidance techniques to minimize the interference incurred at the PUs. Cognitive radio networks (CRNs) have stimulated a variety of studies on improving spectrum utilization. In this context, this thesis has two main objectives. Firstly, it investigates the performance of single hop CRNs with spectrum sharing and opportunistic spectrum access. Secondly, the thesis analyzes the performance improvements of two hop cognitive radio networks when incorporating advanced radio transmission techniques. The thesis is divided into three parts consisting of an introduction part and two research parts based on peer-reviewed publications. Fundamental background on radio propagation channels, cognitive radios, and advanced radio transmission techniques are discussed in the introduction. In the first research part, the performance of single hop CRNs is analyzed. Specifically, underlay spectrum access using M/G/1/K queueing approaches is presented in Part I-A while dynamic spectrum access with prioritized traffics is studied in Part I-B. In the second research part, the performance benefits of integrating advanced radio transmission techniques into cognitive cooperative radio networks (CCRNs) are investigated. In particular, opportunistic spectrum access for amplify-and-forward CCRNs is presented in Part II-A where collaborative spectrum sensing is deployed among the SUs to enhance the accuracy of spectrum sensing. In Part II-B, the effect of channel estimation error and feedback delay on the outage probability and symbol error rate (SER) of multiple-input multiple-output CCRNs is investigated. In Part II-C, adaptive modulation and coding is employed for decode-and-forward CCRNs to improve the spectrum efficiency and to avoid buffer overflow at the relay. Finally, a hybrid interweave-underlay spectrum access scheme for a CCRN is proposed in Part II-D. In this work, the dynamic spectrum access of the PUs and SUs is modeled as a Markov chain which then is utilized to evaluate the outage probability, SER, and outage capacity of the CCRN.

  • 192. Chu, Thi My Chinh
    et al.
    Duong, Quang Trung
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    MRT/MRC for Cognitive AF Relay Networks under Feedback Delay and Channel Estimation Error2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we examine the performance of multiple-input multiple-output cognitive amplify-and-forward (AF) relay systems with maximum ratio transmission (MRT). In particular, closed-form expressions in terms of a tight upper bound for outage probability (OP) and symbol error rate (SER) of the system are derived when considering channel estimation error (CEE) and feedback delay (FD) in our analysis. Through our works, one can see the impact of FD and CEE on the system as well as the benefits of deploying multiple antennas at the transceivers utilizing the spatial diversity of an MRT system.

  • 193. Chu, Thi My Chinh
    et al.
    Duong, Quang Trung
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Outage Probability and Ergodic Capacity for MIMO-MRT Systems under Co-Channel Interference and Imperfect CSI2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we investigate the performance of multiple-input multiple-output (MIMO) systems deploying maximum ratio transmission (MRT). Our analysis takes into account not only imperfect channel estimation at the receiver and feedback delay at the transmitter, but also includes co-channel interference (CCI). In particular, we first derive the statistical properties of the signal-to-interference-plus-noise ratio (SINR). Next, we obtain a closed-form expression for outage probability and an approximation for capacity. Finally, we show the consistency between analytical results and Monte-Carlo simulations. Our results indicate that the system performance is improved considerably in proportion to the number of transceiver antennas. Conversely, the outage probability increases, and the capacity decreases significantly with the severity of channel estimation error, feedback delay, and CCIs.

  • 194.
    Chu, Thi My Chinh
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Duong, Quang Trung
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Performance analysis for multiple-input multiple output- maximum ratio transmission systems with channel estimation error, feedback delay and co-channel interference2013Ingår i: IET Communications, ISSN 1751-8628, Vol. 7, nr 4, s. 279-285Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, the authors analyse the impact of channel estimation error (CEE), feedback delay (FD), and co-channel interference (CCI) on the performance of multiple-input multiple-output (MIMO) systems deploying maximum ratio transmission (MRT). In particular, the authors derive closed-form expressions for the ergodic capacity and the symbol error rate (SER) as well as the outage probability (OP). In addition, to reveal the effect of CEE, FD and CCI on the MIMO-MRT system, the authors adopt more simplified and tractable formulas in terms of asymptotic expressions for the ergodic capacity, SER and OP. The analysis shows that the system performance is degraded considerably under imperfect transmission conditions such as CEE, FD and CCI. However, the authors can compensate part of this degradation by deploying MRT transmission with a large number of antennas at the transmitter and receiver. Finally, the selected examples exhibit consistency between analytical results and Monte Carlo simulations.

  • 195.
    Chu, Thi My Chinh
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Phan, Hoc
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Duong, Quang Trung
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Elkashlan, Maged
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Beamforming Transmission in Cognitive AF Relay Networks with Feedback Delay2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we investigate the effect of feedback delay on outage probability (OP) and symbol error rate (SER) of cognitive amplify-and-forward (AF) relay networks with beamforming transmission in Rayleigh fading environment. It is assumed that the secondary transmitter and the secondary receiver are equipped with multiple antennas, whereas the relay and the primary user comprise of a single antenna. Furthermore, in this system, the secondary users use the underlay scheme in which the secondary transmitter and the relay can coexist with the primary user as long as their interference caused to the primary receiver is below a predefined threshold. Through our analysis, numerical results are provided to show the level of degradation of cognitive AF relay systems in proportion to the degree of feedback delay. In addition, we also present the effect of the number of antennas at the secondary transceiver on the performance of the considered system.

  • 196.
    Chu, Thi My Chinh
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Phan, Hoc
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Adaptive Modulation and Coding with Queue Awareness in Cognitive Incremental Decode-and-Forward Relay Networks2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper studies the performance of adaptive modulation and coding in a cognitive incremental decode-and-forward relaying network where a secondary source can directly communicate with a secondary destination or via an intermediate relay. To maximize transmission efficiency, a policy which flexibly switches between the relaying and direct transmission is proposed. In particular, the transmission, which gives higher average transmission efficiency, will be selected for the communication. Specifically, the direct transmission will be chosen if its instantaneous signal-to-noise ratio (SNR) is higher than one half of that of the relaying transmission. In this case, the appropriate modulation and coding scheme (MCS) of the direct transmission is selected only based on its instantaneous SNR. In the relaying transmission, since the MCS of the transmissions from the source to the relay and from the relay to the destination are implemented independently to each other, buffering of packets at the relay is necessary. To avoid buffer overflow at the relay, the MCS for the relaying transmission is selected by considering both the queue state and the respective instantaneous SNR. Finally, a finite-state Markov chain is modeled to analyze key performance indicators such as outage probability and average transmission efficiency of the cognitive relay network.

  • 197.
    Chu, Thi My Chinh
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Phan, Hoc
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Amplify-and-Forward Relay Assisting both Primary and Secondary Transmissions in Cognitive Radio Networks over Nakagami-m Fading2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we study the performance for the primary and secondary transmissions in cognitive radio networks where the amplify-and-forward (AF) secondary relay helps to transmit the signals for both the primary and secondary transmitters over independent Nakagami-m fading. First, we derive exact closed-form expressions for outage probability and symbol error rate (SER) of the primary network. Then, we derive an exact closed-form expression for outage probability and a closed-form expression of a tight upper bound for SER of the secondary network. Furthermore, we also make a comparison for the performance of the primary system with and without the help of the secondary relay.

  • 198.
    Chu, Thi My Chinh
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Phan, Hoc
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Cognitive AF Relay Assisting both Primary and Secondary Transmission with Beamforming2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper investigates the system performance of a cognitive relay network with underlay spectrum sharing wherein the relay is exploited to assist both the primary and secondary transmitters in forwarding their signals to the respective destinations. To exploit spatial diversity, beamforming transmission is implemented at the transceivers of the primary and secondary networks. Particularly, exact expressions for the outage probability and symbol error rate (SER) of the primary transmission and tight bounded expressions for the outage probability and SER of the secondary transmission are derived. Furthermore, an asymptotic analysis for the primary network, which is utilized to investigate the diversity and coding gain of the network, is developed. Finally, numerical results are presented to show the benefits of the proposed system.

  • 199.
    Chu, Thi My Chinh
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Phan, Hoc
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Cognitive MIMO AF Relay Network with TAS/MRC Under Peak Interference Power Constraint2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we study the use of transmit antenna selection (TAS) and maximal ratio combining (MRC) for a cognitive multiple-input multiple-output (MIMO) amplify-andforward (AF) relay network. We focus on the scenario that each of the source and relay selects only a single antenna which maximizes the instantaneous signal-to-noise ratio (SNR) to transmit and forward the signal while the receiver combines the signals from all receive antennas. Utilizing TAS, the considered cognitive network not only offers advantages such as achieving full diversity order with low transmit complexity but also reduces the interference induced to the primary transmission as compared to maximum ratio transmission (MRT). This in turn becomes beneficial for the secondary network when this network operates under the interference power constraint of the primary receiver. In particular, we derive expressions for the outage probability and symbol error rate (SER) of the network to evaluate the system performance. We also develop an asymptotic analysis for the outage probability and the SER to obtain diversity and coding gain. With the tractable asymptotic expressions, the effect of network parameters such as the number of antennas, the transmission distances, and the interference power constraint of the primary receiver on the system performance are readily revealed.

  • 200.
    Chu, Thi My Chinh
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Phan, Hoc
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Delay Analysis for Cognitive Ad Hoc Networks Using Multi-channel Medium Access Control2014Ingår i: IET Communications, ISSN 1751-8628, E-ISSN 1751-8636, Vol. 8, nr 7, s. 1083-1093Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, the authors analyse the average end-to-end packet delay for a cognitive ad hoc network where multiple secondary nodes randomly contend for accessing the licensed bands of primary users in non-slotted time mode. Before accessing the licensed bands, each node must perform spectrum sensing and collaboratively exchange the sensing results with other nodes of the corresponding communication as a means of improving the accuracy of spectrum sensing. Furthermore, the medium access control with collision avoidance mechanism based distributed coordination function specified by IEEE802.11 is applied to coordinate spectrum access for this cognitive ad hoc network. To evaluate the system performance, the authors model the considered network as an open G/G/1 queuing network and utilise the method of diffusion approximation to analyse the end-to-end packet delay. The authors’ analysis takes into account not only the number of secondary nodes, the arrival rate of primary users and the arrival rate of secondary users but also the effect of the number of licensed bands when assessing the average end-to-end packet delay of the networks.

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