Current Issue : October - December Volume : 2012 Issue Number : 4 Articles : 6 Articles
Broadcasting schemes, such as the fast broadcasting and harmonic broadcasting schemes, significantly reduce the bandwidth\r\nrequirement of video-on-demand services. In the real world, some history events are very hot. For example, every year in March,\r\nthousands of people connect to Internet to watch the live show of Oscar Night. Such actions easily cause the networks contested.\r\nHowever, the schemes mentioned previously cannot alleviate the problem because they do not support live broadcasting. In this\r\npaper, we analyze the requirements for transferring live videos. Based on the requirements, a time skewing approach is proposed\r\nto enable the broadcasting schemes to support live broadcasting. However, the improved schemes require extra bandwidth for live\r\nbroadcasting once the length of live shows exceeds the default. Accordingly, we proposed a scalable binomial broadcasting scheme\r\nto transfer live videos using constant bandwidth by increasing clients� waiting time. When the scheme finds that the length of a\r\nvideo exceeds the default, it doubles the length of to-be-played segments and then its required bandwidth is constant....
Internet protocol TV (IPTV) is a promising Internet killer application, which integrates video, voice, and data onto a single IP\r\nnetwork, and offers viewers an innovative set of choices and control over their TV content. To provide high-quality IPTV services,\r\nan effective strategy is based on caching. This work proposes a segment-based two-tier caching approach, which divides each video\r\ninto multiple segments to be cached. This approach also partitions the cache space into two layers, where the first layer mainly\r\ncaches to-be-played segments and the second layer saves possibly played segments. As the segment access becomes frequent, the\r\nproposed approach enlarges the first layer and reduces the second layer, and vice versa. Because requested segments may not\r\nbe accessed frequently, this work further designs an admission control mechanism to determine whether an incoming segment\r\nshould be cached or not. The cache architecture takes forward/stop playback into account and may replace the unused segments\r\nunder the interrupted playback. Finally, we conduct comprehensive simulation experiments to evaluate the performance of the\r\nproposed approach. The results show that our approach can yield higher hit ratio than previous work under various environmental\r\nparameters....
We develop a framework that exploits network coding (NC) and multiple-input/multiple-output (MIMO) techniques, jointly\r\ntogether, to improve throughput of downlink broadcast channels. Specifically, we consider a base station (BS) equipped with\r\nmultiple transmit antennas that serves multiple mobile stations (MSs) simultaneously by generating multiple signal beams. Given\r\nthe large number of MSs and the small number of transmit antennas, the BS must decide, at any transmission opportunity, which\r\ngroup of MSs it should transmit packets to, in order to maximize the overall throughput.We propose two algorithms for grouping\r\nMSs that take advantage of NC and the orthogonality of user channels to improve the overall throughput. Our results indicate that\r\nthe proposed techniques increase the achievable throughput significantly, especially in highly lossy environments....
Multi-channel Peer-to-Peer (P2P) Video-on-Demand (VoD) systems can be categorized into independent-channel P2P VoD\r\nsystems and correlated-channel P2P VoD systems. Streaming capacity for a channel is defined as the maximal streaming rate that\r\ncan be received by every user of the channel. In this paper, we study the streaming capacity problem in multi-channel P2P VoD\r\nsystems. In an independent-channel P2P VoD system, there is no resource correlation among channels. Therefore, we can find the\r\naverage streaming capacity for the independent-channel P2P VoD system by finding the streaming capacity for each individual\r\nchannel, respectively. We propose a distributed algorithm to solve the streaming capacity problem for a single channel in an\r\nindependent-channel P2P VoD system. The average streaming capacity for a correlated-channel P2P VoD system depends on\r\nboth the intra-channel and cross-channel resource allocation. To better utilize the cross-channel resources, we first optimize the\r\nserver upload allocation among channels to maximize the average streaming capacity and then propose cross-channel helpers to\r\nenable cross-channel sharing of peer upload bandwidths.We demonstrate in the simulations that the correlated-channel P2P VoD\r\nsystems with both intra-channel and cross-channel resource allocation can obtain a higher average streaming capacity compared\r\nto the independent-channel P2P VoD systems with only intra-channel resource allocation....
The Digital Video Broadcasting organisation has recently introduced the second generation of terrestrial broadcast transmission\r\nstandards, DVB-T2. The newly introduced tools ensure significant gain in performance of DVB-T2 compared to the first\r\ngeneration variant of the standard. One of these tools is the new physical layer concatenated forward error correction code. The\r\ninner among the concatenated codes is the Low-Density Parity Check code. The paper proposes a method to extend this code\r\nso varying coding strength inside one physical layer pipe of DVB-T2 is enabled in a backward compatible way. As consequence,\r\nunequal error protection transmission scheme at a physical layer of DVB-T2 can be efficiently deployed. The paper provides a\r\nstep-by-step description of the design procedure of the extension. Moreover, the modification to the processing chain and the\r\nframing structure of DVB-T2, that ensures backward compatibility to the legacy system, is provided. The proposed method is\r\nevaluated under AWGN channel and TU6 channel. Experiments performed on four different video sequences show significant\r\nimprovements in quality of experience when the proposed extension is used to achieve UEP transmission....
This paper addresses methodology and tools applied to the monitoring of accessibility services in digital television at a time\r\nwhen the principles of accessibility and design are being considered in all new audiovisual media communication services. The\r\nmain objective of this research is to measure the quality and quantity of existing accessibility services offered by digital terrestrial\r\ntelevision (DTT). The preliminary results, presented here, offer the development of a prototype for automatic monitoring and a\r\nmethodology for obtaining quality measurements, along with the conclusions drawn by initial studies carried out in Spain. The\r\nrecent approval of the UN Convention on the Rights of Persons with Disabilities gives special relevance to this research because it\r\nprovides valuable guidelines to help set the priorities to improve services currently available to users....
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