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Energy conservation is very important task for wireless sensor networks (WSN), since external power sources are typically unavailable and the replacement of batteries is clearly impractical for large networks. A classical protocol widely used in WSN, called LEACH (low-energy adaptive clustering hierarchy), is a cluster-based protocol which aims at reducing energy consumption in the network. However,...
The Datagram Congestion Control Protocol (DCCP) protocol was proposed to provide a great variety of functionality to real-time applications. Its congestion control mechanisms were defined to be friendly to the TCP-Reno, which makes its operation inappropriate to high speed networks. In this paper, a variant of the DCCP, called FAST DCCP, is proposed to overcome such deficiency. As evidenced by experimental...
Mobile hand-held devices such as smart-phones and tablets have gained in popularity over recent years. However, this induces cellular networks to suffer severe traffic demands that are hard to accommodate. In this respect, utilizing the ad-hoc communication of devices (e.g., bluetooth) can be an alternative way to obtain information while reducing the network overhead. Until now, the application possibility...
Due to the increased capabilities of mobile devices and through wireless opportunistic contacts, users can experience new ways to share and retrieve content anywhere and anytime, even in the presence of link intermittency. Due to the significant number of available routing solutions, it is difficult to understand which one has the best performance, since all of them follow a different evaluation method...
This paper presents an estimation of Quality of Experience (QoE) metrics based on Quality of Service (QoS) metrics in WiMAX networks. Applications used to generate such estimations were EvalVid and Network Simulator 2 (NS-2). The QoE was estimated by employing a Multilayer Artificial Neural Network by means of the WEKA tool. The results show a very efficient estimation of metrics of QoE parameters...
A filter bank multicarrier (FBMC) system having a high level of compatibility with OFDM systems is proposed as new technique for Digital TV transmission. In order to reach the level of robustness, selectivity and performance required by the Digital TV transmission channel, the approach is based on near-perfect reconstruction (NPR) filter bank system combined with OQAM modulation. A key feature of...
Wireless Sensors Network (WSN) together with an efficient delivery of information can provide important benefits to society. However, this technology is still in its early stage. The smart transducer concept, defined by the IEEE 1451 standard and combined with embedded operating systems like TinyOS, can simplify the design and management of WSNs. This work integrates the capabilities of TinyOS and...
Distributed antenna systems (DAS) have been shown to considerably outperform conventional cellular systems in terms of capacity improvement and interference resilience. However, the influence of frequency reuse planning on the performance of DAS remains relatively unknown. To partially fill this gap, this paper presents a comparative analysis of the down-link of DAS versus conventional cellular systems...
A dynamic lightpath allocation algorithm that considers the impact of Raman amplification on the quality of the signal is proposed. To do so, an exhaustive theoretical model that includes fiber attenuation, Rayleigh scattering, stimulated Raman scattering (gain and depletion of channels and pumps) and spontaneous Stokes and anti-Stokes scattering caused by Distributed Fiber Raman Amplifiers (DFRAs)...
Ensuring Quality of Service (QoS) guarantees for real-time traffic in ad hoc networks is challenging due to the lack of infrastructure, energy constraints, contention between packets of a flow and variability of the channel. Cetinkaya et al. designed a measurement-based admission control system that characterizes arrivals and network service by envelope processes, avoiding assumptions of constant...
In recent years, smart-phones and GPS-enabled devices have been a critical factor in the popularization and increasing demand of location based information systems. However, at the same time, the concern of privacy has also increased on users who would like to protect their exact location from attackers or from the service provider. One technique to protect the location is called Location Obfuscation,...
In a near future, wireless mesh networks (WMNs) and multimedia content will be abundant technologies/applications in the Internet. Hence, in order to keep and attract new customers, as well as, reduce operational costs, the development of new quality level control schemes are needed and it is one of the key requirements for the success of next generation wireless multimedia systems. With this goal...
Near field beamforming has been of interest lately due to its capacity to discriminate unwanted sources in the direction of desired signal at a different distance. Due to their required large matrix inverse and eigenvalue decompositions, the existing methods are not very attractive in real time dynamic signal reception scenario because of their prohibitive computational demands. This paper proposes...
This paper addresses transmission aspects on very high aggregate wavelength-division multiplexing (WDM) based passive optical networks (PON) capable of delivering, up to 1000 wavelengths/users separated by a few Gigahertz broadband connections at 1–10Gb/s through a single optical fiber. These networks rely on employing high-order modulation formats such as M-ary PSK (phase-shift keying) or M-ary QAM...
In this paper, we study the impact of churn on object management policies implemented by a P2P assisted CDN. The effectiveness of buffer enlargement and replicating control, in reducing the effects of churn on these policies, is analyzed. We have found that neither the simply enlargement of peers' storage capacity nor a zero replicating strategy are effective actions to improve performance of an object...
Steering angle errors are known to be a major cause of performance degradation of adaptive beamformers, especially when the signal of interest is present in the measurements. Diagonal loading is one of the most widely used and effective methods to improve robustness of adaptive beamformers. This paper presents two robust beamforming algorithms using efficient realisation techniques. The techniques...
The huge computing power available in some graphic cards may be used to significantly speedup scientific computing compared with common parallel clusters. The low price and virtually ubiquitous Graphics Processing Units (GPU), in conjunction with C style parallel programming tools, like CUDA (Compute Unified Device Architecture), allow the programmers to exploit their fine grain parallelism and multithreading...
The integration of WiMAX networks with EPON networks combine the large bandwidth availability in optical access networks with the mobility provided by wireless technologies. In this integration, a WiMAX bandwidth scheduler that takes into account the variability of the channel capacity provided by the EPON scheduler is quite important, since the granted bandwidth must be sufficient to support the...
Radio-over-Fiber (RoF) has been employed in network infrastructures due to its large capacity, low attenuation, low operational costs and enlarged network coverage. Wireless Sensor Networks (WSNs) has also been broadly deployed. The integration of these two powerful technologies leads to new infrastructures. In this work, we introduce a new approach for integrating of RoF and WSNs, and present HMARS,...
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