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  • 251. Dam, Hai Huyen
    et al.
    Zepernick, Hans-Jürgen
    Nordholm, Sven
    Nordberg, Jörgen
    Spreading Code Design Using a Global Optimization Method2005Ingår i: Annals of Operations Research, ISSN 0254-5330, E-ISSN 1572-9338, Vol. 133, nr 1-4, s. 249-264Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The performance of a code division multiple access system depends on the correlation properties of the employed spreading code. Low cross-correlation values between spreading sequences are desired to suppress multiple access interference and to improve bit error performance. An auto-correlation function with a distinct peak enables proper synchronization and suppresses intersymbol interference. However, these requirements contradict each other and a trade-off needs to be established. In this paper, a global two dimensional optimization method is proposed to minimize the out-of-phase average mean-square aperiodic auto-correlation with average mean-square aperiodic cross-correlation being allowed to lie within a fixed region. This approach is applied to design sets of complex spreading sequences. A design example is presented to illustrate the relation between various correlation characteristics. The correlations of the obtained sets are compared with correlations of other known sequences.

  • 252.
    Dantuluri, Kishore Varma
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Impact of Virtualization on Timestamp Accuracy2015Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    The ever-increasing demand for high quality services require a good quantification of performance parameters such as delay and jitter. Let’s consider one of the parameters, jitter, which is the difference between the inter arrival time of two subsequent packets and the average inter-arrival time. The arrival or departure time of a packet is termed as time-stamp. The accuracy of the timestamp will influence any performance metrics based on the arrival/departure time of a packet. Hence, the knowledge or awareness of time-stamping accuracy is important for performance evaluation. This study investigates how the time-stamping process is affected by virtualization

  • 253.
    Darisipudi, Veeravenkata Naga S Maniteja
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Sustainable Throughput – QoE Perspective2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In recent years, there has been a significant increase in the demand for streaming of high quality videos on the smart mobile phones. In order to meet the user quality requirements, it is important to maintain the end user quality while taking the resource consumption into consideration. This demand caught the attention of the research communities and network providers to prioritize Quality of Experience (QoE) in addition to the Quality of Service (QoS). In order to meet the users’ expectations, the QoE studies have gained utmost importance, thus creating the challenge of evaluating it in such a way that the quality, cost and energy consumption are taken into account. This gave way to the concept of QoE-aware sustainable throughput, which denotes the maximal throughput at which QoE problems can be still kept at a desired level.

    The aim of the thesis is to determine the sustainable throughput values from the QoE perspective. The values are observed for different delay and packet loss values in wireless and mobile scenarios. The evaluation is done using the subjective video quality assessment method.

    In the subjective assessment method, the evaluation is done using the ITU-T recommended Absolute Category Rating (ACR). The video quality ratings are taken from the users, and are then averaged to obtain the Mean Opinion Score (MOS). The obtained scores are used for analysis in determining the sustainable throughput values from the users’ perspective.

    From the results it is determined that, for all the video test cases, the videos are rated better quality at low packet loss values and low delay values. The quality of the videos with the presence of delay is rated high compared to the video quality in the case of packet loss. It was observed that the high resolution videos are feeble in the presence of higher disturbances i.e. high packet loss and larger delays. From considering all the cases, it can be observed that the QoE disturbances due to the delivery issues is at an acceptable minimum for the 360px video. Hence, the 480x360 video is the threshold to sustain the video quality.

  • 254.
    Darukumalli, Subbareddy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Baraki, Yared Tuemay
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Video Content Assessment Based on Perceptual Quality Indicators (A Popularity Predictor Model for YouTube Videos)2014Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Various video quality assessment methods have been developed to assess the quality of videos worldwide. Most of these methods and metrics focus on certain impairments and degradation that are caused during processing or transmission. Only very few do focus on metrics of video quality based on their content. Those few are also limited in that they are specifically designed and developed to deal on a specific parameter. It is customary to hear about the most popular music and clips being announced on the mainstream media based on the hits they have in a specific period. Attempts have been made to develop algorithms that predict the hits of music singles. Studies show that a subject’s liking or disliking of the contents of videos influence subjective assessments. In this thesis, we have considered opinion deviations of viewers’ as gradient function. The amount of differences between assessments of a subject for a certain video defines the order of deviation which is called as gradient degree. The accumulated numbers of all subjects’ assessments for a certain video and for each gradient degree defines the amplitude of the related gradient degree. Video popularity sometimes is related to its perceptual quality, due to this reason; we used perceptual quality indicators as video content assessment categories. In this thesis, we have presented a new methodology that can be used to predict the subjective video content perception of viewers. In this paper, we have also proposed a model that uses the new gradient methodology to predict popularity of streaming videos. With the proposed model, we have found global weighting constants for predicting video popularity of YouTube video database. In this thesis we concluded that, we can predict the video quality of a video package from the decision consistency (inconsistency) of a certain number of people using the PQI categories. Having a predefined, but enough, number of people we can predict the acceptance of a video before we release to the wider population.

  • 255.
    Das, Subrata Kumar
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Synthetic Aperture Radar Image Quality Measurements2010Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Abstract Synthetic Aperture Radar (SAR) is an important tool for remote sensing now a day. SAR image quality measurements play an important role in the development of SAR image digital processing methods. The essential SAR image quality assessments are spatial resolutions, Integrated Sidelobe Ratio (ISLR) and Peak Sidelobe Ratio (PSLR). This thesis mainly focuses on the UWB SAR image quality measurements. Since the spatial resolutions depend on integration angle in UWB SAR, measurements should be performed at different integration angles for a UWB SAR system. Evaluation or comparison of the resolutions obtained with different UWB SAR systems can be based on another measurement named differential resolution measurements. For ISLR and PSLR measurements, it is seen that elliptical areas are more suitable for delimitation of mainlobe and sidelobe areas of a UWB SAR image than rectangular areas. This is proved by an investigation relied on a newly derived Impulse Response Function in SAR Imaging (IRF-SAR) instead of the widely used sinc function. From this investigation, we can also see that a factor of 2.5 is sufficient to represent the spread of mainlobe in both azimuth and range direction. In this work, we use simulated UWB-low frequency CARABAS-II data. The simulations are performed in Matlab. In spite of the main drawback in computational cost, Global Backprojection (GBP) algorithm is still selected for UWB SAR image formation due to its time-domain characteristics such as extreme range migration handling, manageable motion compensation.

  • 256.
    Dehghannayyeri, Atefeh
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Developing a Fluid Flow Model for Mobile Video Transmission in the Presence of Play-Out Hysteresis2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This work focuses on improving video transmission quality over a mobile link. More specifically, the impact of buffering and link outages on the freeze probability of transmitted videos is studied. It introduces a new fluid flow model that provides an approximation of the freeze probability in the presence of play-out hysteresis. The proposed model is used to study the impact of two streaming buffer sizes over different possible combinations of outage parameters (data channel on/off times). The outcome of this thesis shows that outage parameters play a dominant role in freezing of streaming video content, and that an increase in these parameters cannot be easily compensated for by an increase in the size of the receiving buffer. Generally, in most cases when there is a variation in outage parameters, an increased buffer size has a negative impact on the freeze probability. To lower the probability of freeze during video playback over a weak mobile link, it is better to sacrifice resolution just to keep the video content playing. Similarly, shifting focus from off to on times brings better results than increasing buffer size.

  • 257.
    Delgado, Sergio Mellado
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Velasco, Alberto Díaz
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Indoor Positioning using the Android Platform2014Självständigt arbete på grundnivå (kandidatexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    In recent years, there has been a great increase in the development of wireless technologies and location services. For this reason, numerous projects in the location field, have arisen. In addition, with the appearance of the open Android operating system, wireless technologies are being developed faster than ever. This Project approaches the design and development of a system that combines the technologies of wireless, location and Android with the implementation of an indoor positioning system. As a result, an Android application has been obtained, which detects the position of a phone in a simple and useful way. The application is based on the WIFI manager API of Android. It combines the data stored in a SQL database with the wifi data received at any given time. Afterwards the position of the user is determined with the algorithm that has been implemented. This application is able to obtain the position of any person who is inside a building with Wi-Fi coverage, and display it on the screen of any device with the Android operating system. Besides the estimation of the position, this system displays a map that helps you see in which quadrant of the room are positioned in real time. This system has been designed with a simple interface to allow people without technology knowledge. Finally, several tests and simulations of the system have been carried out to see its operation and accuracy. The performance of the system has been verified in two different places and changes have been made in the Java code to improve its precision and effectiveness. As a result of the several tests, it has been noticed that the placement of the access point (AP) and the configuration of the Wireless network is an important point that should be taken into account to avoid interferences and errors as much as possible, in the estimation of the position.

  • 258.
    Dernaika, Ghina
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Khavtasi, Sophia
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Multimedia Codec Evaluation and Overview2007Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Movies, songs, conferences, video streams and other multimedia services are spreading in everybody’s life, needs and work. Different types of audio and video codecs of various qualities appear to be used for different purposes. However, each codec can be suitable for a special usage, as for example a codec that can be use for high quality film may not be suitable for streaming it into network. The main purpose of this thesis is to compare the performance of different codecs in one particular scenario and indicate which codec performance is the best. The thesis work includes the investigation of several codec aspects (audio and video) and problems related to choosing a multimedia codec (coder/decoder) suitable for large-scale multimedia distribution over the Internet. More specifically, the work focuses on various features of modern media codecs, compares them and finds the best application for each of them. Furthermore, the thesis provides an overview of available research results related to this work and codec comparison tables for codecs and their features. Additionally, as part of this work, a testbed was developed to measure the performance of codecs when used to stream media over a network. The testbed enabled the collection of various QoS parameters, such as bandwidth usage and burst, size for each codec considered in this thesis.

  • 259. DeVogeleer, Karel
    et al.
    Erman, David
    Popescu, Adrian
    Simulating BitTorrent2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    IP Television (IPTV) and other media distribution applications are expected to be one of the next Internet killer applications. One indication of this is the corporate backing that the IP Multimedia Subsystem (IMS) is getting. However, the bandwidth utilization of these applications is still an issue, as the volume of multimedia grows due to larger image resolution and higher bitrate audio. One way of managing this increase in bandwidth requirements is to use existing endhost bandwidth to decrease the load on the content server in a Peer-to-Peer (P2P) fashion. One of the most successful P2P applications is BitTorrent (BT), a swarming file transfer system. This paper presents an implementation of a BT simulator intended for future use in investigating modifications to the BT system to provide streaming media capabilities. The simulator is validated against real-world measurements and a brief performance analysis is provided.

  • 260.
    Dey, Ajoy Kumar
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Saha, Susmita
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Acoustic Beamforming: Design and Development of Steered Response Power With Phase Transformation (SRP-PHAT).2011Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Acoustic Sound Source localization using signal processing is required in order to estimate the direction from where a particular acoustic source signal is coming and it is also important in order to find a soluation for hands free communication. Video conferencing, hand free communications are different applications requiring acoustic sound source localization. This applications need a robust algorithm which can reliably localize and position the acoustic sound sources. The Steered Response Power Phase Transform (SRP-PHAT) is an important and roubst algorithm to localilze acoustic sound sources. However, the algorithm has a high computational complexity thus making the algorithm unsuitable for real time applications. This thesis focuses on describe the implementation of the SRP-PHAT algorithm as a function of source type, reverberation levels and ambient noise. The main objective of this thesis is to present different approaches of the SRP-PHAT to verify the algorithm in terms of acoustic enviroment, microphone array configuration, acoustic source position and levels of reverberation and noise.

  • 261.
    Dhakal, Prabesh
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Tiwari, Prabhat
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Chan, Pawan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Perceptual Video Quality Assessment Tool2014Självständigt arbete på grundnivå (kandidatexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    In our research work, we have designed the tool that can be used to conduct a mass-scale level survey or subjective tests. ACR is the only method used to carry out the subjective video assessment. The test is very useful in the context of a video streaming quality. The survey can be used in various countries and sectors with low internet speeds to determine the kind of video or the compression technique, bit rate, or format that gives the best quality.

  • 262.
    Dhakal, Rajendra
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Mahat, Sagar Raj
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Performance Analysis of DF Relay Systems with Keyhole and Correlation Effects2011Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    In recent years, the innovation of multiple-input multiple-output (MIMO) has completely changed the face of wireless communication system. Especially, the concept of MIMO is evolved to fulfill the demand of multimedia services. However, challenges have risen to the system provider for maintaining the quality of service (QoS) and reliability of MIMO system. Additionally, very recently, cooperative communication has been proposed in order to face and deal with the shortcomings of MIMO system. In cooperative communication, the addition of relay between source and destination enhances the QoS and reliability of wireless system. The main purpose of this paper is to derive the closed form analytical expressions of symbol error rate (SER) of M-ary phase shift keying (MPSK) for MIMO decode-and forward (DF) relay system. Besides, SER derivation is based on moment generating function (MGF) of the overall system. In our case, we only deal with a downlink MIMO DF relay system. Here, we consider an $n_t$-antenna at the source $S$, an $n_r$-antenna at the relay $R$ and an $n_d$-antenna at the destination $D$, where the propagated signal from the source passes through keyhole and correlated channel. Further, the same orthogonal space time block codes (OSTBC) is applied to source-destination, source-relay and relay-destination link to exploit the maximal diversity gain. Furthermore, we analyze the effects of MPSK modulation on MIMO DF system under different values of correlation coefficient by combining the different antenna pairs at different nodes. Beside this, we compare keyhole and no keyhole MIMO relay systems with fix value of correlation coefficient and antenna pairs. With the use of cooperative scheme, effects of keyhole on MIMO DF architecture can be minimized to certain level. Eventually, our simulation analysis excellently matches with analytical results, which is sufficient to validate our work.

  • 263.
    Dhungana, Ramesh
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Shahi, Deepak
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    A Quantitative Study of Quality of Experience (QoE) for Decreasing and Increasing Network Performance.2011Självständigt arbete på grundnivå (kandidatexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Currently, user satisfaction is becoming one of the major concerns for the service provider in accommodating user demand. This paper evaluates the user’s perception (Quality of Experience, QoE) of the increasing and decreasing response times (Quality of Service, QoS), in particular a login to web login page by the implementation of Mean Opinion Score (MOS). By comparing the results to user perception of web login performance, we show that the users perceive web login for increasing and decreasing RTs in different ways. So, we conduct interview among specific users applying increased and decreased RTs in particular web login to rank the users satisfaction level. Study of the two results for RTs of the web login page is presented.

  • 264.
    Ding, Yuan
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Wu, YiBing
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    TDD Linear Precoding Methods for Next Generation Mobile Communication Systems2011Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    I denna avhandling ger vi våra förutsägelse om nästa mobila kommunikationssystem, som utökar kapaciteten i rumsliga domän med hjälp av ett stort antal antenner och fortfarande håller förenligheten med den tidigare generationens mobila kommunikationssystem. Men för det oförenliga del-precoding-in sådana nya system, presenterar vi två TDD linjär precoding metoder i denna avhandling. Genom simuleringar kan vi se att dessa två precoding metoder är möjlig för det nya systemet och bidra till att öka dess kapacitet prestanda.

  • 265.
    , D.M.BAPPY
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    RAHMAN, MD HAMIDUR
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    A Study in 3D Structure Detection Implementing Forward Camera Motion2012Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    In this thesis we have studied detection of 3D structures having a forward camera movement which has strong influence of translation along the optical axis of the camera. During the forward movement the camera might undergoes rotation and translation .We have used “Plane plus Parallax” algorithm to cancel out this unwanted rotation. The input to the algorithm is a sequence of frames aligned with respect to a certain planar surface. The algorithm gives three types of outputs. (i) Dense correspondence across all frames. (ii) Dense 3D structure relative to the planar surface. (ii) Focus of Expansion (FOE) in all frames with respect to reference frame. Camera calibration is not needed for this algorithm. We have applied this algorithm to real world images and synthetic images. In both cases the 3D structure information could be obtained clearly even for objects far from the reference plane. Our result shows the potential of the method in 3D reconstruction implementing ego-motion of a single camera.

  • 266.
    Donkena, Kaushik
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Gannamani, Subbarayudu
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Performance Evaluation of Cloud Database and Traditional Database in terms of Response Time while Retrieving the Data2012Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Context: There has been an exponential growth in the size of the databases in the recent times and the same amount of growth is expected in the future. There has been a firm drop in the storage cost followed by a rapid increase in t he storage capacity. The entry of Cloud in the recent times has changed the equations. The Performance of the Database plays a vital role in the competition. In this research, an attempt has been made to evaluate and compare the performance of the traditional database and the Cloud Database. Objectives: This thesis investigates about the prior works on the issues that affect the performance of Cloud Database. And compares the performance of a Database in Traditional to that Cloud Environments Methods: Two different research methods are used to carry the research. They are Systematic Literature Review (SLR) and Quantitative Methodology. Articles from Scientific Databases are chosen for SLR process. Results: From the SLR process, 4 issues were identified. From the Experimentation results, Cloud Database is having poor performance compared to the Traditional Database. Conclusions: Issues that affect the performance of Cloud Database are identified and a test bed is created to test the performance of a Database. Attempts are to be made to improve the performance of Cloud Database.

  • 267. Doria, Avri
    ForCES Protocol Specification2007Övrigt (Övrigt vetenskapligt)
    Abstract [en]

    This document specifies the Forwarding and Control Element Separation (ForCES) protocol. ForCES protocol is used for communications between Control Elements(CEs) and Forwarding Elements (FEs) in a ForCES Network Element (ForCES NE). This specification is intended to meet the ForCES protocol requirements defined in RFC3654. Besides the ForCES protocol messages, the specification also defines the framework, the mechanisms, and the Transport Mapping Layer (TML) requirements for ForCES protocol.

  • 268. Doria, Avri
    GSMPv3 Base Specification2006Övrigt (Övrigt vetenskapligt)
    Abstract [en]

    This document describes the base General Switch Management Protocol Version 3 (GSMPv3). The GSMPv3 is an asymmetric protocol that allows one or more external switch controllers to establish and maintain the state of a label switch. The GSMPv3 allows control of both unicast and multicast switch connection state as well as control of switch system resources and QoS features.

  • 269. Doria, Avri
    et al.
    Davies, Elwyn
    Analysis of IDR requirements and History2007Övrigt (Övrigt vetenskapligt)
    Abstract [en]

    This document analyses the current state of IDR routing with respect to RFC1126 and other IDR requirements and design efforts. It is the companion document to "Requirements for Inter-Domain Routing" [I-D.irtf-routing-reqs], which is a discussion of requirements for the future routing architecture and future routing protocols. Publication of this document is in accordance with the consensus of the active contributors the IRTF's Routing Research Group.

  • 270. Doria, Avri
    et al.
    Lindgren, Anders
    Probabilistic Routing Protocol for Intermittently Connected Networks2007Övrigt (Övrigt vetenskapligt)
    Abstract [en]

    This document defines PRoPHET, a Probabilistic Routing Protocol using History of Encounters and Transitivity. PRoPHET is a routing protocol for intermittently connected networks, where there is no guarantee that a fully connected path between source and destination exists at any time, rendering traditional routing protocols unable to deliver messages between hosts. These networks are examples of networks where the Delay-Tolerant Network architecture[1] is applicable. The document presents an architectural overview followed by the protocol specification.

  • 271. Du, Xu
    et al.
    Vo, Nguyen-Son
    Cheng, Wenqing
    Duong, Quang Trung
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Shu, Lei
    Joint Replication Density and Rate Allocation Optimization for VoD Systems over Wireless Mesh Networks2013Ingår i: IEEE transactions on circuits and systems for video technology (Print), ISSN 1051-8215, E-ISSN 1558-2205, Vol. 23, nr 7, s. 1260-1273Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Due to the limited resources and dynamically varying nature of wireless links, guaranteeing high quality demands for a large number of heterogeneous users is very challenging in video streaming over wireless networks. In this paper, we introduce a layered multiple description coding with an embedded forward error correction scheme (LMDC-FEC). The combination of layered MDC and FEC aims at coping with not only the diverse bandwidth and unreliability of wireless links but also the heterogeneous user devices. We further propose a joint replication density and rate allocation (RD-RA) optimization problem in the context of video on-demand systems (VoDs) over wireless mesh networks (WMNs), and employ a genetic algorithms based approach to solve the optimization problem. Our objective is to elaborately distribute proper replication density for each video segment and allocate optimal bit rate to each layer of each segment in order to gain high userperceived quality (UPQ) with small consumption of storage resource. By this method, both optimal replication densities and rate allocations are found in accordance with the access rate of segments, the diverse loss characteristics of descriptions in each segment, and the rate–distortion relationship of segments, so as to thoroughly optimize UPQ and storage resource consumption. Simulation results demonstrate that our proposed method significantly enhances the streaming performance of VoDs over WMNs.

  • 272. Duong, Quang Trung
    Exact Closed-Form Expression for Average Symbol Error Rate of MIMO-MRC Systems2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we derive closed-form expressions for exact average symbol error rate (SER) of multiple-input multiple-output (MIMO)-maximum ratio combining (MRC) systems with M-ary modulations. We obtain the tractable compact closed-form expressions for the average SER in terms of the Gauss and Appell hypergeometric functions which are provided as library functions in common mathematical softwares such as MAPLE and MATHEMATICA. The analysis is validated by comparing with Monte-Carlo simulations and we further show that our general SER expressions reduce to the previous known results for binary signals (M=2) as a special case. Applying the series representation of the Gauss and Appell hypergeometric function, we derive a very tight approximation for the average SER

  • 273. Duong, Quang Trung
    On Cooperative Communications and Its Application to Mobile Multimedia2010Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    With the rapid growth of multimedia services, future generations of wireless communications require higher data rates and a more reliable transmission link while keeping satisfactory quality of service. In this respect, multipleinput multiple-output (MIMO) antenna systems have been considered as an efficient approach to address these demands by offering significant multiplexing and diversity gains over single-antenna systems without increasing requirements on radio resources such as bandwidth and power. Although MIMO systems can unfold their huge benefit in cellular base stations, they may face limitations when it comes to their deployment in mobile handsets. In particular, the typically small-size of mobile handsets makes it impractical to deploy multiple antennas. To overcome this drawback, the concept of cooperative communications has recently been proposed and gained large interest in the research community. The key idea is to form a virtual MIMO antenna array by utilizing a third terminal, a so-called relay node, which assists the direct communication. After receiving the source’s message, the relay processes and forwards it to the destination. With this approach, the benefits of MIMO systems can be attained in a distributed fashion. Furthermore, cooperative communications can efficiently combat the severity of fading and shadowing effects through the assistance of relay terminals. It has been shown that using the relay can extend the coverage of wireless networks. In this thesis, we focus on the performance evaluation of such cooperative communication systems and their application to mobile multimedia. The thesis is divided into five parts. In particular, the first part proposes a hybrid decode-amplify-forward (HDAF) relaying protocol which can significantly improve the performance of cooperative communication systems compared to the two conventional schemes of decode-and-forward (DF) and amplify-and-forward (AF). It is interesting to see that the performance gain of HDAF over DF and AF strictly depends on the relative value of channel conditions between the two hops. The second part extends HDAF to the case of multiple relays. It is important to note that the gains are saturated as the number of relays tends to be a large value. This observation motivates us to use a small number of relays to reduce network overhead as well as system complexity while the obtained gains are still as much as in the large-number case. In the third part, we analyze the performance of DF relaying networks with best relay selection over Nakagami-m fading channels. Besides the diversity gain, we show that the spatial multiplexing gain can be achieved by cooperative communications. We analyze the performance of cooperative multiplexing systems in terms of symbol error rate and ergodic capacity over composite fading channels. Finally, in the fifth part, we exploit the benefit of both diversity and multiplexing gain by proposing an unequal error transmission scheme for mobile multimedia services using cooperative communications.

  • 274. Duong, Quang Trung
    et al.
    Alay, Ozgu
    Erkip, Elza
    Zepernick, Hans-Jürgen
    End-to-End Performance of Randomized Distributed Space-Time Codes2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    The exact closed-form expressions for symbol error probability and outage probability of randomized distributed space-time codes (RDSTC) under Rayleigh fading are derived. The diversity gain derived in the literature uses the Chernoff bound which may not be achievable in general. Utilizing the exact expression, the achievable diversity gain of RDSTCs is validated. The closed-form expressions are verified by Monte-Carlo simulations.

  • 275. Duong, Quang Trung
    et al.
    Alexandropoulos, George C.
    Tsiftsis, Theodoros A.
    Zepernick, Hans-Jürgen
    Outage probability of MIMO AF relay networks over Nakagami-m fading channels2010Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 46, nr 17Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The outage probability (OP) of multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay networks using orthogonal space-time block code is investigated. In particular, a closed-form tight lower bound expression for the OP over independently but not necessarily identically distributed Nakagami-m fading channels is derived. Moreover, an asymptotic approximation for OP which reveals the coding and diversity gains is presented. The analytical expressions are validated by Monte-Carlo simulations.

  • 276. Duong, Quang Trung
    et al.
    Alexandropoulos, George C.
    Zepernick, Hans-Jürgen
    Tsiftsis, Theodoros A.
    Orthogonal Space-Time Block Codes with CSI-Assisted Amplify-and-Forward Relaying in Correlated Nakagami-m Fading Channels2011Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 60, nr 3, s. 882-889Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the performance of multiple-input multiple-output (MIMO) dual-hop amplify-and-forward (AF) relay systems using orthogonal space-time block codes (OSTBCs) over arbitrarily correlated Nakagami-m fading channels is analyzed. In particular, closed-form expressions for the end-to-end outage probability (OP) and the symbol error probability (SEP) with arbitrary number of transceiver antennas and general correlation matrices are derived. Their mathematically tractable forms readily enable us to evaluate the performance of MIMO AF relay systems that utilize OSTBCs. For sufficiently high signal-to-noise ratios, asymptotically tight approximations for the OP and SEP are also attained which reveal insights into the effects of fading parameters and antenna correlation on the system’s performance. Furthermore, we prove that the correlation has no impact on the achievable diversity gain which is equal to the minimum of the sum of fading parameters between the two hops. Selected numerically evaluated results are presented showing an excellent agreement between the proposed analysis and equivalent Monte-Carlo simulations.

  • 277. Duong, Quang Trung
    et al.
    Bao, Vo Nguyen Quoc
    Alexandropoulos, George C.
    Zepernick, Hans-Jürgen
    Cooperative spectrum sharing networks with AF relay and selection diversity2011Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 47, nr 20, s. 1149-1151Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The exact outage probability (OP) of cognitive dual-hop relay networks equipped with a single amplify-and-forward (AF) relay and a selection combining receiver at the destination is derived under spectrum sharing constraint on a primary user. The tractable closed-form OP readily enables evaluation of system performance, which indicates the significance of using a relay in cognitive radio networks with a spectrum sharing approach. The proposed analysis is validated by numerical examples.

  • 278.
    Duong, Quang Trung
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Bao, Vo Nguyen Quoc
    Tran, Hung
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Alexandropoulos, George C.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Effect of primary network on performance of spectrum sharing AF relaying2012Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 48, nr 1, s. 25-U95Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Most of the research in spectrum sharing has neglected the effect of interference from primary users. In this reported work, the performance of spectrum sharing amplify-and-forward relay networks under interference-limited environment, where the interference induced by the transmission of primary networks is taken into account, is investigated. In particular, a closed-form expression tight lower bound of outage probability is derived. To reveal additional insights into the effect of primary networks on the diversity and array gains, an asymptotic expression is also obtained.

  • 279. Duong, Quang Trung
    et al.
    Bao, Vo Nguyen Quoc
    Tran, Nguyen Nam
    Ergodic Capacity of Cooperative Networks Using Adaptive Transmission and Selection Combining2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    Closed-form expressions for channel capacity of repetition-based cooperative networks under adaptive transmission with selection combining are presented under the assumption of independent Rayleigh fading. Specifically, three different adaptive techniques are investigated: optimal simultaneous power and rate adaptation (OPRA), constant power with optimal rate adaptation (OPA) and channel inversion with fixed rate (TIFR). Among them, for an arbitrary number of relays, TIFR gives the worst channel capacity; OPRA gives the best channel capacity and ORA has a channel capacity quality in between the others. The analysis results, based on the upper and lower bound of the end-to-end SNR, agree very well with the simulated results and definitely show the impact of selection combining on the calculated channel capacity per unit bandwidth

  • 280. Duong, Quang Trung
    et al.
    Bao, Vo Nguyen Quoc
    Zepernick, Hans-Jürgen
    Exact outage probability of cognitive AF relaying with underlay spectrum sharing2011Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 47, nr 17, s. 1001-1002Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The exact closed-form expression for the outage probability (OP) of cognitive radio dual-hop amplify-and-forward (AF) relay networks is derived. The tractable expression of the OP, given in the form of elementary functions, readily enables evaluating the effect of primary users on the secondary system performance. It has been shown that the use of AF relaying significantly improves the performance of cognitive radio networks compared to its direct transmission counterpart.

  • 281. Duong, Quang Trung
    et al.
    Bao, Vo Nguyen Quoc
    Zepernick, Hans-Jürgen
    On the Performance of Selection Decode-and-Forward Relay Networks over Nakagami-m Fading Channels2009Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 13, nr 3, s. 172-174Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we present the performance of fixed decode-and-forward cooperative networks with relay selection over independent but not identically distributed Nakagamim fading channels, with integer values of the fading severity parameter m. Specifically, closed-form expressions for the symbol error probability and the outage probability are derived using the statistical characteristic of the signal-to-noise ratio. We also perform Monte-Carlo simulations to verify the analytical results

  • 282.
    Duong, Quang Trung
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Costa, Daniel Benevides da
    Elkashlan, Maged
    Bao, Vo Nguyen Quoc
    Cognitive Amplify-and-Forward Relay Networks over Nakagami-m Fading2012Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 61, nr 5, s. 2368-2374Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this correspondence, the outage probability (OP) of dual-hop cognitive amplify-and-forward (AF) relay networks subject to independent non-identically distributed (i.n.i.d.) Nakagami-m fading is examined. We assume a spectrum sharing environment, where two different strategies are proposed for determining the transmit powers of the secondary network. Specifically, the transmit power conditions of the proposed spectrum sharing network are governed by either: (i) the combined power constraint of the interference on the primary network and maximum transmission power at the secondary network; or (ii) the single power constraint of the interference on the primary network. Closed-form lower bounds and asymptotic expressions for the OP are derived. Regardless of the transmit power constraint, we reveal that the diversity order is strictly defined by the minimum fading severity between the two hops of the secondary network. This aligns with the well-known result for conventional dual-hop AF relaying without spectrum sharing. Furthermore, the impact of the primary network on the diversity-multiplexing tradeoff is investigated. We confirm that the diversity-multiplexing tradeoff is independent of the primary network.

  • 283.
    Duong, Quang Trung
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    da Costa, Daniel Benevides
    Tsiftsis, Theodoros A.
    Zhong, Caijun
    Nallanathan, Arumugam
    Outage and Diversity of Cognitive Relaying Systems under Spectrum Sharing Environments in Nakagami-m Fading2012Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 12, nr 11Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this letter, the outage performance of dualhop cooperative spectrum sharing systems with a direct link is investigated. A selection combining receiver is employed at the destination in order to combine the signals received from the decode-and-forward (DF) relay and from the source. Assuming independent non-identically distributed Nakagami-m fading channels, exact and asymptotic closed-form expressions are derived for the outage probability. Our results reveal that the diversity order of the considered system is solely determined by the fading severity parameters of the secondary network, being equal to min(m1, m2) + m0, where m0, m1, and m2 represent the fading severity parameters of the secondary nodes i.e., source→destination, source→relay, and relay→destination links, respectivel

  • 284. Duong, Quang Trung
    et al.
    Engelke, Ulrich
    Zepernick, Hans-Jürgen
    Cooperative Wireless Communications with Unequal Error Protection and Fixed Decode-And-Forward Relays2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we examine an unequal error protection (UEP) scheme for wireless imaging that is based on utilizing the distributed diversity offered by decode-and-forward (DF) networks. Specifically, the data stream after source encoding is divided into high and low priority sub-streams depending on their importance for image reconstruction. A relay-selection combining (R-SC) scheme is exploited for high priority image data to achieve high reliability while cooperative spatial multiplexing is employed to low priority image data to support high spectral efficiency. In this work, we specifically take into account the setting that relays may forward erroneously detected signals to the destination when cooperating with fixed DF. In this context, the analytical and numerical results validate that R-SC outperforms other relaying protocols in terms of average symbol error probability while the considered UEP approach offers the highest spectral efficiency among the examined relaying schemes.

  • 285. Duong, Quang Trung
    et al.
    Engelke, Ulrich
    Zepernick, Hans-Jürgen
    Unequal Error Protection for Wireless Multimedia Transmission in Decode-and-Forward Relay Networks2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we propose an unequal error protection (UEP) scheme for multimedia transmission over wireless decode-and-forward (DF) relay networks. We prove that relay selection combining (R-SC) mode yields a better error rate performance than all-participate relays, i.e., distributed spacetime codes (DSTC) and orthogonal transmission with maximum ratio combining (OT-MRC) at the destination. Hence, we apply the R-SC scheme for transmitting bit sequence with high priority while the cooperative spatial multiplexing scheme is employed for the bit-stream with low priority. With this strategy, we achieve the maximum spatial diversity gain for high priority data and a high spatial multiplexing gain for low priority data. Monte- Carlo simulations and analytical results are shown to validate the proposed UEP scheme.

  • 286. Duong, Quang Trung
    et al.
    Hoang, Le-Nam
    Bao, Vo Nguyen Quoc
    On the Performance of Two-Way Amplify-and-Forward Relay Networks2009Ingår i: IEICE transactions on communications, ISSN 0916-8516, E-ISSN 1745-1345, Vol. E92-B, nr 12, s. 3957-3959Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The performance of two-way amplify-and-forward (AF) relay networks is presented. In particular, we derive exact closed-form expressions for symbol error rate (SER), average sum-rate, and outage probability of two-way AF relay systems in independent but not identically distributed (i.n.i.d.) Rayleigh fading channels. Our analysis is validated by a comparison against the results of Monte-Carlo simulations.

  • 287. Duong, Quang Trung
    et al.
    Le, Thanh-Tan
    Zepernick, Hans-Jürgen
    Performance of Cognitive Radio Networks with Maximal Ratio Combining over Correlated Rayleigh Fading2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we apply the maximal ratio combining (MRC) technique to achieve higher detection probability in cognitive radio networks over correlated Rayleigh fading channels. We present a simple approach to derive the probability of detection in closed-form expression. The numerical results reveal that the detection performance is a monotonically increasing function with respect to the number of antennas. Moreover, we provide sets of complementary receiver operating characteristic (ROC) curves to illustrate the effect of antenna correlation on the sensing performance of cognitive radio networks employing MRC schemes in some respective scenarios.

  • 288.
    Duong, Quang Trung
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Ngo, Hien Quoc
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Nallanathan, Arumugam
    Distributed Space-Time Coding in Two-Way Fixed Gain Relay Networks over Nakagami-m Fading2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    The distributed Alamouti space-time code in two-way fixed gain amplify-and-forward (AF) relay is proposed in this paper. In particular, closed-form expressions for approximated ergodic sum-rate and exact pairwise error probability (PWEP) are derived for Nakagami-m fading channels. To reveal further insights into array and diversity gains, an asymptotic PWEP is also obtained. Finally, numerical results are provided to corroborate the proposed theoretical analysis.

  • 289. Duong, Quang Trung
    et al.
    Nguyen, Ngoc-Tien
    Hoang, Trang
    Nguyen, Viet-Kinh
    Pairwise Error Probability of Distributed Space--Time Coding Employing Alamouti Scheme in Wireless Relays Networks2009Ingår i: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. 51, nr 2, s. 231-244Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we analyze the pairwise error probability (PEP) of distributed space-time codes, in which the source and the relay generate Alamouti space--time code in a distributed fashion. We restrict our attention to the space-time code construction for Protocol III in [1]. In particular, we derive two closed-form approximations for PEP when the relay is either close to the destination or source and an upper bound for any position of the relay. Using the alternative definition of $Q$-function, we can express these PEPs in terms of finite integral whose integrand is composed of trigonometric functions. We further show that with only one relay assisted source-destination link, system still achieves diversity order of two, assuming single-antenna terminals. We also perform Monte-Carlo simulations to verify the analysis.

  • 290.
    Duong, Quang Trung
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Shu, Lei
    Chen, Min
    Vo Nguyen Quoc, Bao
    Dac Binh, Ha
    Performance analysis of cooperative spatial multiplexing networks with AF/DF relaying and linear receiver over Rayleigh fading channels2015Ingår i: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, Vol. 15, nr 3, s. 500-509Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cooperative spatial multiplexing (CSM) system has played an important role in wireless networks by offering a substantial improvement in multiplexing gain compared with its cooperative diversity counterpart. However, there is a limited number of research works that consider the performance of CSM systems. As such, in this paper, we have derived exact performance of CSM with amplify-and-forward and decode-and-forward relays in terms of outage capacity and ergodic capacity. We have shown that CSM systems yield a unity diversity order regardless of the number of antennas at the destination and the number of relays in the networks, which is the direct result of diversity and multiplexing gain trade-off. Our analytical expressions are corroborated by Monte-Carlo simulations.

  • 291.
    Duong, Quang Trung
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Suraweera, Himal A.
    Tsiftsis, Theodoros A.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Nallanathan, Arumugam
    Keyhole Effect in Dual-Hop MIMO AF Relay Transmission with Space-Time Block Codes2012Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 60, nr 12, s. 1-11Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the effect of keyhole on the performance of multiple-input multiple-output (MIMO) amplifyand-forward (AF) relay networks with orthogonal space-time block codes (OSTBCs) transmission is investigated. In particular, we analyze the asymptotic symbol error probability (SEP) performance of a downlink communication system where the amplifying processing at the relay can be implemented by either the linear or squaring approach. Our tractable asymptotic SEP expressions enable us to obtain both diversity and array gains. Our finding reveals that with condition nS > min(nR, nD), the linear approach can provide the full achievable diversity gain of min(nR, nD) when only the second hop suffers from the keyhole effect, i.e., single keyhole effect (SKE), where nS, nR, and nD are the number of antennas at source, relay, and destination, respectively. However, for the case that both the source-relay and relay-destination links experience the keyhole effect, i.e., double keyhole effect (DKE), the achievable diversity order is only one regardless of the number of antennas. In contrast, utilizing the squaring approach, the overall diversity gain can be achieved as min(nR, nD) for both SKE and DKE. An important observation corroborated by our studies is that for satisfying the tradeoff between performance and complexity, we should use the linear approach for SKE and the squaring approach for DKE.

  • 292. Duong, Quang Trung
    et al.
    Suraweera, Himal A.
    Tsiftsis, Theodoros A.
    Zepernick, Hans-Jürgen
    Nallanathan, Arumugam
    OSTBC Transmission in MIMO AF Relay Systems with Keyhole and Spatial Correlation Effects2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we investigate the degenerative effects of antenna correlation and keyhole on the performance of multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay networks. In particular, we considered a downlink MIMO AF relay system consisting of an nS-antenna base station S, an nR-antenna relay station R, and an nD-antenna mobile station D, in which the signal propagation originated from the mobile station suffers from keyhole and spatial correlation effects. We have derived an exact expression for the moment generation function of the instantaneous signal-to-noise ratio which enables us to analyze the symbol error probability and outage probability of the considered system.We have shown that although the mobile station is in a poor scattering environment, i.e., keyhole, the relay channel (S → R → D link) still achieves a cooperative diversity order of min(nR, nD) provided that the channel from the source (S → R link) is keyhole-free. This result is important to radio system designers since under such a severe scenario it is unnecessary to deploy a large number of antennas on the relay station (nR) but only requires nR = nD to obtain the maximum achievable diversity gain.

  • 293. Duong, Quang Trung
    et al.
    Suraweera, Himal A.
    Yuen, Chau
    Zepernick, Hans-Jürgen
    Multi-Keyhole Effect in MIMO AF Relay Downlink Transmission with Space-Time Block Codes2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Multi-keyhole bridges the gap between single keyhole and full-scattering multiple-input multiple-output (MIMO) channels. In this paper, we therefore investigate the multi-keyhole effect on the MIMO amplify-and-forward (AF) relay downlink transmission with orthogonal space-time block codes. In particular, we derive the analytical symbol error rate (SER) expression for the considered system with arbitrary number of keyholes. Moreover, SER approximations in the high SNR regime for several important special scenarios of multi-keyhole channels are further derived. These asymptotic results provide important insights into the impact of system's parameters on the SER performance. Our analysis is confirmed by comparing with Monte-Carlo simulations.

  • 294.
    Duong, Quang Trung
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Suraweera, Himal A.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Yuen, Chau
    Beamforming in Two-Way Fixed Gain Amplify-and-Forward Relay Systems with CCI2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    We analyze the outage performance of a two-way fixed gain amplify-and-forward (AF) relay system with beamforming, arbitrary antenna correlation, and co-channel interference (CCI). Assuming CCI at the relay, we derive the exact individual user outage probability in closed-form. Additionally, while neglecting CCI, we also investigate the system outage probability of the considered network, which is declared if any of the two users is in transmission outage. Our results indicate that the position of the relay in this system plays an important role in determining the user as well as the system outage probability via such parameters as signal-to-noise imbalance, antenna configuration, spatial correlation, and CCI power. To render further insights into the effect of antenna correlation and CCI on the diversity and array gains, an asymptotic expression which tightly converges to exact results is also derived.

  • 295.
    Duong, Quang Trung
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Vo, Nguyen-Son
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Shu, Lei
    Du, Xu
    Cheng, Wenping
    Replication Strategies for Video On-Demand over Wireless Mesh Networks: A Cross-Layer Optimization Approach2012Ingår i: Using Cross-Layer Techniques for Communication Systems / [ed] Rashvand, Habib F.; Kavian, Yousef S., IGI , 2012, s. 349-375Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    In this chapter, dependencies between the different protocol layers and across the hops through WMNs will be exploited to deliver video streaming with high QoE. Specifically, a cross-layer optimization approach is applied to a replication strategy for video on-demand over WMNs. Additionally, the authors consider a distributed implementation algorithm, namely Mod&Timer, to handle the placement of replicas for saving storage resources of the network. Simulation results are shown to demonstrate that the proposed cross-layer design outperforms many existing schemes in terms of QoE. More importantly, compared to other strategies without cross-layer interaction, the proposed cross-layer design satisfies the heterogeneous bandwidth constraint of end users.

  • 296. Duong, Quang Trung
    et al.
    Yuen, Chau
    Zepernick, Hans-Jürgen
    Lei, Xianfu
    Average Sum-Rate of Distributed Alamouti Space--Time Scheme in Two-Way Amplify-and-Forward Relay Networks2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we propose a distributed Alamouti space-time code (DASTC) for two-way relay networks employing a single amplify-and-forward (AF) relay. We first derive closed-form expressions for the approximated average sum-rate of the proposed DASTC scheme. Our analysis is validated by a comparison against the results of Monte-Carlo simulations. Numerical results verify the effectiveness of our proposed scheme over the conventional DASTC with one-way communication.

  • 297. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Adaptive Transmission Scheme for Wireless Cooperative Communications2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    An adaptive transmission scheme for cooperative communications is proposed in this paper. Communication protocols with amplify-and-forward relays based on the distributed-Alamouti space-time code (achieving spatial diversity gain) and cooperative spatial multiplexing (C-SM) (pertaining spatial multiplexing gain) are considered. Specifically, under a fix transmission rate, we use adaptively the cooperative diversity (C-DIV) and C-SM according to channel conditions. With this strategy, either C-DIV with higher order modulation or C-SM with lower order modulation can be properly selected to enhance the error rate performance. The proposed adaptive protocol is shown to provide superior performance compared to C-DIV and C-SM.

  • 298.
    Duong, Quang Trung
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Cross-Layer Design for Packet Data Transmission in Maximum Ratio Transmission Systems with Imperfect CSI and Co-Channel Interference2012Ingår i: Using Cross-Layer Techniques for Communication Systems / [ed] Rashvand, Habib F.; Kavian, Yousef S., IGI , 2012, s. 376-399Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    This chapter will therefore present some new results for the cross-layer design for packet data transmission applied to co-located MIMO with maximum ratio transmission. In this context, closed-form expressions for the average packet error rate, average achievable spectral efficiency, and outage probability are derived. This enables one to evaluate the performance of the cross-layer design under predetermined delay and packet loss constraints. Some important results in the high Signal-to-Noise Ratio (SNR) regime are also provided, revealing insights on how system and channel parameters affect system performance. More importantly, a mathematical analysis is proved to be a powerful tool to investigate the impact of practical issues such as channel estimation error, feedback delay, antenna correlation, and rank-deficient MIMO channel matrix, on the performance of cross-layer design.

  • 299. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Exact Average Symbol Error Rate of Cooperative Spatial Multiplexing in Composite Channels2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    Performance of cooperative spatial multiplexing systems over composite channels is presented. In particular, we derive the exact closed-form average symbol error rate (SER) expressions for cooperative spatial multiplexing systems with linear equalization receiver (e.g., Zero-Forcing) and M-ary modulation scheme in the composite channel of log-normal shadowing and Rayleigh fading. Using the Gauss-Hermite quadrature integration, the average SER is expressed in the forms of Appell hypergeometric function. Applying the series representation of Appell hypergeometric function, we derive a very tight approximation for the average SER. We also perform Monte-Carlo simulations to validate our analysis.

  • 300. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    On the Ergodic Capacity of Cooperative Spatial Multiplexing Systems in Composite Channels2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    The ergodic capacity of cooperative spatial multiplexing systems over composite channels is presented. Specifically, we derive the exact closed-form expressions for ergodic capacity of cooperative spatial multiplexing systems with linear receiver in the composite channel of log-normal shadowing and Rayleigh fading. Using the Gauss-Hermite quadrature integration, the final analytical result of ergodic capacity is described in a closed-form expression. We also perform Monte-Carlo simulations to validate our analysis. Subsequently, we apply the obtained analytical expression to evaluate some representative scenarios regarding to spatial multiplexing gain in relay composite channels

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