Current Issue : January - March Volume : 2014 Issue Number : 1 Articles : 5 Articles
In vehicular networks, sparse roadside vehicular communication (RVC) systems on highways are difficult to provide full coverage\r\nof existing roadways because the distance between the roadside units (RSUs) is farther than the RSU�s transmission range. In\r\nsparse RVC, collision-free communication is required because the time available for communication is very short. In addition, the\r\ncollision-free communication has an energy-efficient feature. Therefore, we propose an energy-efficient broadcastMAC protocol in\r\norder to expand the service coverage in RVC systems and collision-free communication. The proposed protocol performs a hybrid\r\nvehicular communication (HVC). It has a rebroadcast mechanism using a vehicle�s velocity, distance, and angle fromnearby vehicle\r\nfor collision-free communication. Then, we show our protocol�s performance evaluation using ns-2....
Data broadcast is a fundamental operation in wireless sensor networks (WSNs). The existence of wireless interference makes\r\nit nontrivial to design a minimum-latency broadcast scheme, which is known to be NP-hard. Existing works all assume strict\r\ntime synchronization and provide centralized TDMA scheduling algorithms. However, WSNs in practice are more likely to be\r\ndistributed asynchronous systems. In this paper, we investigate the problem of data broadcast with minimum latency for distributed\r\nasynchronous WSNs. To this end, we propose a Distributed Asynchronous Broadcast (DAB) algorithm which crucially leverages\r\nan elaborately optimized carrier-sensing range together with collision-backoff schemes to coordinate the transmissions among\r\nthe nodes on a predetermined broadcast backbone. Theoretical analysis shows that DAB is order-optimal and achieves constant\r\nfactor approximation to the optimal delay. We then conduct extensive simulations to evaluate the practical capability of DAB in\r\nasynchronousWSNs and the results corroborate our theoretical analysis....
Improving energy efficiency is the most important challenge in wireless sensor networks. Because sensing information is correlated\r\nin many sensor network applications, some previous works have proposed ideas that reduce the energy consumption of the\r\nnetwork by exploiting the spatial correlation between sensed information. In this paper, we propose a distributed data compression\r\nframework that exploits the broadcasting characteristic of the wireless medium to improve energy efficiency. We analyze the\r\nperformance of the proposed framework numerically and compare it with the performance of previous works using simulation.\r\nThe proposed scheme performs better when the sensing information is correlated....
High-quality real-time video streaming to users in mobile networks is challenging due to the dynamically changing nature of\r\nthe network paths, particularly the limited bandwidth and varying end-to-end delay. In this paper, we empirically investigate\r\nthe performance of multipath streaming in the context of multihomed mobile networks. Existing schemes that make use of the\r\naggregated bandwidth ofmultiple paths can overcome bandwidth limitations on a single path but suffer an efficiency penalty caused\r\nby retransmission of lost packets in reliable transport schemes or path switching overheads in unreliable transport schemes. This\r\nwork focuses on the evaluation of schemes to permit concurrent use of multiple paths to deliver video streams. A comprehensive\r\nstreaming framework for concurrent multipath video streaming is proposed and experimentally evaluated, using current stateof-\r\nthe-art H.264 Scalable Video Coding (H.264/SVC) and the next generation High Efficiency Video Coding (HEVC) standards.\r\nIt provides a valuable insight into the benefit of using such schemes in conjunction with encoder specific packet prioritisation\r\nmechanisms for quality-aware packet scheduling and scalable streaming. The remaining obstacles to deployment of concurrent\r\nmultipath schemes are identified, and the challenges in realising HEVC based concurrent multipath streaming are highlighted....
Due to the advancement of network technology, video-on-demand (VoD) services are growing in popularity. However, individual\r\nstream allocation for client requests easily causes a VoD system overload; when its network and disk bandwidth cannot match\r\nclient growth. This study thus presents a fundamentally different approach by focusing solely on a class of applications identified\r\nas latency tolerant applications. Because video broadcasting does not provide interactive (i.e., VCR) functions, a client is able to\r\ntolerate playback latency froma video server. One efficient broadcasting method is periodic broadcasting,which divides a video into\r\nsmaller segments and broadcasts these segments periodically on multiple channels. However, numerous practical systems, such as\r\ndigital video broadcasting-handheld (DVB-H), do not allow clients to download video data frommultiple channels because clients\r\nusually only have one tuner. To resolve this problem in multiple-channel broadcasting, this study proposes a novel single-channel\r\nbroadcasting scheme, which leverages segment-broadcasting capability further for more efficient video delivery.The comparison\r\nresults show that, with the same settings of broadcasting bandwidth, the proposed scheme outperforms the alternative broadcasting\r\nscheme, the hopping insertion scheme, SingBroad, PAS, and the reverse-order scheduling scheme for the maximal waiting time....
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