4,885 research outputs found

    Estimating commitment in a digital market place environment

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    The future generation of mobile communication shall be a convergence of mobile telephony and information systems which promises to change people's lives by enabling them to access information when, where and how they want. It presents opportunities to offer multimedia applications and services that meet end-toend service requirements. The Digital Marketplace framework will enable users to have separate contracts for different services on a per call basis. In order for such a framework to function appropriately, there has to be some means for the network operator to know in advance if its network will be able to support the user requirements. This paper discusses the methods by which the network operator will be able to determine if the system will be able to support another user of a certain service class and therefore negotiate parameters like commitment, QoS and the associated cost for providing the service, thus making the Digital Marketplace wor

    Robust and scalable matching pursuits video transmission using the Bluetooth air interface standard

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    This paper introduces an error resilient implementation of the matching pursuits algorithm for video coding. The video bitstream is transmitted using a simulation of the Bluetooth air interface standard, which recommends ARQ as a means of overcoming channel errors in the data packets. This approach may be unsuitable for real time and broadcast applications. Therefore, a modified receiver is proposed in this paper, which does not request the retransmission of erroneous packets, but instead passes them to the video decoder to exploit error resilience. This strategy is shown to be superior to a standard compliant system if ARQ cannot be applied. The work confirms that wireless communication standards should support a transparent mode for video applications

    Link adaptation algorithms for improved delivery of delay- and error-sensitive packet-data services over wireless networks

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    Link Adaptation is a radio resource management technique that assesses the channel conditions and selects a transport mode, from a set of possible options, which is optimised for these conditions according to a predefined criterion. The optimum transport mode is commonly determined so as to maximise the throughput. Although this approach may be appropriate for best-effort services, its suitability for multimedia services, usually characterised by tight delay and error performance constraints, has been questioned. As a result, a number of alternative algorithms have been proposed in the literature. In this context, this paper presents and evaluates in a dynamic radio environment several Link Adaptation algorithms designed to enhance the provision of delay- and error-sensitive multimedia packet-data services over wireless systems. The obtained results demonstrate that significant improvements in terms of throughput, transmission delay, error performance and operation of Link Adaptation itself can be obtained with the proposed schemes.Postprint (published version

    Distributed video coding for wireless video sensor networks: a review of the state-of-the-art architectures

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    Distributed video coding (DVC) is a relatively new video coding architecture originated from two fundamental theorems namely, Slepian–Wolf and Wyner–Ziv. Recent research developments have made DVC attractive for applications in the emerging domain of wireless video sensor networks (WVSNs). This paper reviews the state-of-the-art DVC architectures with a focus on understanding their opportunities and gaps in addressing the operational requirements and application needs of WVSNs

    Integer Linear Programming Optimization of Joint RRM Policies for Heterogeneous Wireless Systems

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    Wireless systems will be characterized by the coexistence of heterogeneous Radio Access Technologies (RATs) with different, but also complementary, performance and technical characteristics. These heterogeneous wireless networks will provide network operators the possibility to efficiently and coordinately use the heterogeneous radio resources, for which novel Joint Radio Resource Management (JRRM) policies need to be designed. In this context, this work proposes and evaluates a JRRM policy that simultaneously determines for each user an adequate combination of RAT and number of radio resources within such RAT to guarantee the user/service QoS requirements, and efficiently distribute the radio resources considering a user fairness approach aimed at maximizing the system capacity. To this aim, the JRRM algorithm, which takes into account the discrete nature of radio resources, is based on integer linear programming optimization mechanisms

    Slight-Delay Shaped Variable Bit Rate (SD-SVBR) Technique for Video Transmission

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    The aim of this thesis is to present a new shaped Variable Bit Rate (VBR) for video transmission, which plays a crucial role in delivering video traffic over the Internet. This is due to the surge of video media applications over the Internet and the video typically has the characteristic of a highly bursty traffic, which leads to the Internet bandwidth fluctuation. This new shaped algorithm, referred to as Slight Delay - Shaped Variable Bit Rate (SD-SVBR), is aimed at controlling the video rate for video application transmission. It is designed based on the Shaped VBR (SVBR) algorithm and was implemented in the Network Simulator 2 (ns-2). SVBR algorithm is devised for real-time video applications and it has several limitations and weaknesses due to its embedded estimation or prediction processes. SVBR faces several problems, such as the occurrence of unwanted sharp decrease in data rate, buffer overflow, the existence of a low data rate, and the generation of a cyclical negative fluctuation. The new algorithm is capable of producing a high data rate and at the same time a better quantization parameter (QP) stability video sequence. In addition, the data rate is shaped efficiently to prevent unwanted sharp increment or decrement, and to avoid buffer overflow. To achieve the aim, SD-SVBR has three strategies, which are processing the next Group of Picture (GoP) video sequence and obtaining the QP-to-data rate list, dimensioning the data rate to a higher utilization of the leaky-bucket, and implementing a QP smoothing method by carefully measuring the effects of following the previous QP value. However, this algorithm has to be combined with a network feedback algorithm to produce a better overall video rate control. A combination of several video clips, which consisted of a varied video rate, has been used for the purpose of evaluating SD-SVBR performance. The results showed that SD-SVBR gains an impressive overall Peak Signal-to-Noise Ratio (PSNR) value. In addition, in almost all cases, it gains a high video rate but without buffer overflow, utilizes the buffer well, and interestingly, it is still able to obtain smoother QP fluctuation
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