Current Issue : July - September Volume : 2013 Issue Number : 3 Articles : 5 Articles
Cognitive radio is being intensively researched as the enabling technology for license-exempt access to the so-called TV White\r\nSpaces (TVWS), large portions of spectrum in the UHF/VHF bands which become available on a geographical basis after digital\r\nswitchover. Both in the US, and more recently, in the UK the regulators have given conditional endorsement to this new mode\r\nof access. This paper reviews the state-of-the-art in technology, regulation, and standardisation of cognitive access to TVWS. It\r\nexamines the spectrum opportunity and commercial use cases associated with this form of secondary access....
The optimal allocation of the retransmission bandwidth is essential for IPTV service providers to ensure maximal service\r\nquality. This paper highlights the relevance of the wireless transport in today�s IPTV solution and discusses how this new media\r\naffects the existing broadcast technologies. A new Markovian channel model is developed to address the optimization issues\r\nof the retransmission throughput, and a new method is presented which is evaluated by empirical measurements followed by\r\nmathematical analysis....
Due to the fact that proxy-driven proxy cache management and the client-driven streaming solution of Dynamic Adaptive\r\nStreaming over HTTP (DASH) are two independent processes, some difficulties and challenges arise in media data management\r\nat the proxy cache and rate adaptation at the DASH client. This paper presents a novel client-driven joint proxy cache management\r\nandDASHrate adaptationmethod, named CLICRA,whichmoves prefetching intelligence fromthe proxy cache to the client. Based\r\non the philosophy of CLICRA, this paper proposes a rate adaptation algorithm, which selects bitrates for the next media segments\r\nto be requested by using the predicted buffered media time in the client. CLICRA is realized by conveying information on the\r\nsegments that are likely to be fetched subsequently to the proxy cache so that it can use the information for prefetching. Simulation\r\nresults show that the proposed method outperforms the conventional segment-fetch-time-based rate adaptation and the proxydriven\r\nproxy cache management significantly not only in streaming quality at the client but also in bandwidth and storage usage in\r\nproxy caches....
The orthogonal frequency division multiplexing (OFDM) modulation technique is one of the key strategies for multiuser signal\r\ntransmission especially in smart grids and wind farms. This paper introduces an approach for peak-to-average power ratio (PAPR)\r\nreduction of such signals based on novel global harmony search (NGHS) and partial transmit sequence (PTS) schemes. In PTS\r\ntechnique, the data block to be transmitted is partitioned into disjoint subblocks, which are combined using phase factors to\r\nminimize PAPR. The PTS requires an exhaustive search over all combinations of allowed phase factors. Therefore, with respect to\r\nthe fast implementation and simplicity of NGHS technique, we could achieve significant reduction of PAPR....
With the wide deployment of Internet Protocol (IP) infrastructure and rapid development of digital technologies, Internet Protocol\r\nTelevision (IPTV) has emerged as one of the majormultimedia access techniques. A general IPTV transmission system employs\r\nboth encryption and forward error correction (FEC) to provide the authorized subscriber with a high-quality perceptual experience.\r\nThis two-layer processing, however, complicates the system design in terms of computational cost and management cost. In\r\nthis paper, we propose a novel FEC scheme to ensure the secure and reliable transmission for IPTV multimedia content and services.\r\nThe proposed secure FEC utilizes the characteristics of FEC including the FEC-encoded redundancies and the limitation of\r\nerror correction capacity to protect themultimedia packets against the malicious attacks and data transmission errors/losses. Experimental\r\nresults demonstrate that the proposed scheme obtains similar performance compared with the joint encryption and FEC\r\nscheme....
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