Abstract:In Wireless Sensor Networks, many new protocols have been designed to reduce overall end-to-end delay when transmitting the data gathered by the sensor node to the storage sink. Most of the importance have been given to the delay sensitive applications and reduce the delay using routing protocols. This paper makes a survey on recent routing protocols which reduce the delay in delay sensitive applications. Several delay types are identified and moreover founded that solutions are given mainly for queuing delay and propagation delay. Finally, we comment on the research issues are open in several delay types
Abstract:The challenging issue of defining and implementing an effective law for load balancing in Content Delivery Networks (CDNs). The proposal on a forma study of a CDN system, carried out through the exploitation of a fluid flow model characterization of the network of servers. Starting from such characterization, it derives and proves a lemma about the network queues equilibrium. The result is then leverage in order to devise a novel distributed and timecontinuous algorithm for load balancing, which is also reformulated in a time-discrete version. The discrete formulation of the proposed balancing law is eventually discussed in terms of its actual implementation in a real-world scenario. Finally, the overall approach is validated by means of simulations.
In the modern communication and computation era, internet of things (IoT) is developing as the key technology that satisfies the requirements of various applications. Prolonging device lifetime and maintaining network reliability is the evident objective for IoT network. Therefore, the authors come up with the network architecture that integrates node placement technique and routing technique. In the architecture, node placement is implemented by varying the density of nodes, by varying battery level of nodes, and by varying transmission range of nodes. Energy efficient and reliable path computation is addressed by routing technique. Therefore, enhancing the features of routing and node placement technique and integrating them together in network architecture can efficiently prolong the network lifetime. From the results, the authors observed that the proposed network architecture prolongs the network lifetime two times better than the standard model and also outperforms EQSR protocol and maintains the reliable data transfer.
The last decade has witnessed a growing demand for wireless radio spectrum due to the rapid deployment of new wireless devices and applications. Spectrum is a precious resource and thus underutilization of a large part of allocated spectrum is not acceptable. Cognitive radio (CR) is proposed as a promising solution for increasing spectrum utilization and thereby helping to mitigate spectrum scarcity. CR is capable of sensing the unused spectrum bands and adapt to operate in the vacant bands. Once cognitive radios detect the presence of a primary user in their operating band, they must vacate the band immediately. Hence, accurate spectrum sensing is an essential feature of CR systems. In this paper, a cyclostationary spectrum sensing method for identifying the presence of primary user is introduced which uses the concept of periodicity in OFDM signals. In existing method,the periodicity of pilot signals in the OFDM symbols is used to detect the signals. The proposed scheme is robust to the detection of primary user signal with guard interval insertion in the OFDM signals which use the concept of periodicity. The power spectral density of average and true method which defines the spectrum power is compared and the simulation results are given in this paper. It is observed from the results that true power spectral density method is well suitable for CR which enables perfect sensing over primary users.
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