Peer-to-peer (P2P) computing or networking system is a distributed application architecture that partitions tasks or bandwidth between peers. Every peer in the system is equitable and equivalent to each other. P2P computing makes a breakthrough to the limitations of traditional client-server architecture, for examples, it can reduce the server’s load and improve the scalability and heterogeneity of a cooperative network. The resource, such as computing power, network bandwidth, and file data etc., can be shared via the upload capacity of every peer. Thanks to the successful popularity of pioneering file-sharing applications on the Internet, the more and more live multimedia distributions have been deployed around our surroundings.
1.1. Background
Computer networking is one of the most interesting and important technique in recent three decades. The network not only provides a communication function and computation infrastructure, but also connects the global sociality and publicity. Internet is the most important application closed popularly to the convenient life on the public network. Internet interconnects and shares the information among computers and users, and more and more people rely on Internet. However, the number of the end systems grows exponentially, and the traditional client-server architecture cannot be affordable for the exponential increases or burst crowds. Therefore, a P2P solution is proposed to overcome the limitations.
In P2P solution, each peer plays the equal role to share and balance the network’s load, and acts both as a client and a server, or called servent. The distributed ability and upload capacity of every peer can be utilized to achieve a task collaboratively. P2P technology encourages the development of network service with three advantages at least: (1) Server’s
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resources can be economized. (2) The cost of service infrastructure can be greatly reduced.
(3) The scalability challenge of large-scale application can be resolved. Due to these advantages, P2P network is applied for file sharing, group conferencing, multimedia multicasting, and live streaming. Nowadays, the P2P system dominates over 60% of wired network traffic [15]. It is reported that, in 2007, the P2P Internet traffic is up to 21268836 TB, which is approximately 54.4% of the global consumer Internet traffic, and 37.9% of the global Internet traffic [16].
With the development of triple-play network and social network, the real-time multimedia service is more and more important. Although live media streams can be delivered effectively through the content distribution network (CDN) or the IP multicast technique, the infrastructure must be established in advance and maintained in period.
Moreover, the deployment cost of CDN is too high to be affordable, and IP multicast mostly encounters the problem of business policies, which obstruct the service deployment. It is difficult to perform IP multicast across the heterogeneous routers and the different Internet service providers. For these reasons, the application layer multicast is employed to support the live multimedia streaming nowadays. One of the proper application layer multicast approaches is the P2P technology.
1.2. Issues
With the advance of basic network infrastructure and the development of television digitization, the users can access P2P network easily and enjoy the high quality possibly.
For examples, the subscribers are interested in BitTorrent [17], Skype [18], and PPStream [19], for their entertainments and communications. BitTorrent is an application for file sharing, how to avoid the disappearance of source is the critical issue; Skype is an application for voice communicating, how to deliver the real-time voice data is the major
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issue; PPStream is an application for video distributing, how to break through the bottleneck of asymmetrical bandwidth is the important issue. In the paper, we must consider these issues simultaneously in the service of Internet television.
Based on P2P video distribution, Internet television can be divided into two kinds:
video on demand (VoD) and live programs. PPTV [20] and PPStream belong to the kind of VoD. Most of VoD systems provide the movies and dramas, which are non-live video data.
There are few instant factors in VoD system, so it can tolerate the delays. However, unlike VoD downloading, on-line viewers usually watch the live games, the first-hand stock information or the latest news on live streaming services. These viewers would not like to suffer any sensible lags in such live programs. Therefore, the buffering techniques used by both VoD and P2P file sharing are ineffective to benefit the implementation of live streaming system. Hence, how to continue the stream smoothly and deliver it efficiently among the peers is important for P2P solution.
Because Internet television breaks through the stereotype of traditional television, the innovative development brings the expectable advantages for academic and commercial areas: (1) every user can publish his/her made content on Internet television. (2) All television stations can get the accurate report of viewer rating statistics. (3) A television station needn’t consider the problems of radio or cable any more. (4) The customized programs and advertisements can be provided for the specific subscribers. (5) All programs are global access. (6) Every user can interact with Internet television. Therefore, we would like to stand out these advantages in the paper.
1.3. Motivation
To design a live streaming system or Internet television, both network aspect and multimedia manipulation must be considered. How to reduce bandwidth consumption of the
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IPTV streaming system and deliver instant video data efficiently throughout the network are major difficulties. However, most of the existing systems consider the issues individually. A lack of integration leads to the inefficient delivery. Therefore, we design a novel delivery strategy for the general video coder and live large-scale distribution on Internet. In addition, we also design a mechanism to improve system stability. We consider the above advantages to implement Internet television on P2P network due to the high scalability and low cost.
Our proposed scheme can stabilize the P2P live streaming [22].
However, there are several inherent challenges in P2P live streaming. P2P technology brings some drawbacks such as the long startup delay and the uneven playback, which lead to the poor quality of experience (QoE). Measurement studies pointed out that the major limitation of overlay constructing is peer churning, and the annoying bottleneck of service provisioning is the insufficient upload bandwidth. Although the proposed scheme still meets the inherent challenges, a novel mechanism utilizes system bandwidth efficiently. On the other hand, a comprehensive integration of data scheduling can shorten the startup delay and improve the playback smoothness to heighten the QoE.
In utilization of system bandwidth, we introduce a mechanism to reduce waste of bandwidth. In data delivery, first, the data should be defined in priority; second, the instant and prior data should be delivered with high priority. In general, a video film can be divided into many frames, and a stream can be divided into the continuous chunks. Although frames and chunks are encapsulated sequentially in the network transmission, there is no relationship between frames and chunks. In general, the frames include of key-frames and general frames. The key-frame can be decoded independently, but the general frame must be decoded depending on the key-frame. Therefore, the key-frames should be forwarded first.
We propose a content-aware delivery mechanism which put the user watching behavior into account. Users know what contents his favorite programs are playing through our approach. This results in decrease of unnecessary channel zapping. In addition, a
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frame-aware scheme is introduced to check the frame type, which tags the key-frame in a special chunk. The special chunk has a high distribution priority in network. An additional chunk scheduling cooperates with the proposed scheme to raise the probability of key-frame distribution. This leads to the increase of effective data, which avoids the content bottleneck and improves the playback smoothness. The frame-aware chunk scheduling can be implemented in the existing P2P protocols with a little modification, and it is suitable for the asymmetric network or the limited bandwidth capacity especially.
1.4. Goal
Our proposed scheme needn’t modify the P2P overlay or peer adaptation. We only modify the content delivery and the chunk scheduling strategy. Transmission of low quality pictures to let users know the playing content of their favorite channels. In order to receiving these additional data, we have to add additional buffer in client and introduce an approach to share these low quality pictures. Through the notification of these pictures, users don’t frequently find their interesting programs by surfing the channels. There is a significant reduction of surfing times in the system by applying our method, and this lead to improvement of system robustness.
Further, a dependency between the frame type and the chunk type is formed to consider the network aspect and multimedia manipulation. The integration of frame-aware scheme must team up with encoder modification and chunk division. The design principle is that the chunk including of the key-frame is prioritized to deliver among the peers.
Moreover, a chunk scheduling helps the balanced distribution to avoid the starvation problem and content bottleneck. The goal is to let the key-frames always be decoded in the client’s player and improves the playback smoothness for QoE. In following discussion, we demonstrate that the proposed scheme is workable via a series of experiments.
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Because only content delivery strategy and chunk scheduling mechanism are modified, our proposed scheme can be workable in any P2P live streaming system and suitable for any P2P overlay. Not only the scalability of IPTV system is promoting, but also the QoE performance is increased efficiently in the scheme. Our proposed scheme can efficiently utilize the system bandwidth for urgent situation (i.e., cannot display the media content) and avoid the disappearance of important data, deliver the real-time and large-size multimedia data, be appropriate for asymmetrical and heterogeneous network, and improve the playback smoothness.
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