Research On Opportunistic Network Video Blocking And Scheduling Strategies For Mobile Learning

With the development of mobile learning applications and wireless communication technologies, campus mobile learning based on mobile devices is becoming more and more popular to students. Mobile learning is a kind of new learning style which user can learn without restricting by time and place. However, the heavy data traffic causes an expensive cost and users in remote areas cannot utilize cellular networks for mobile learning, both of which have become the tough problems to be solved. Therefore, we consider using delay tolerance and low cost of opportunistic networks to handle this challenge. Opportunistic network is a kind of networks which employs "store-carry-forward" routing strategy. Furthermore, multimedia video transmission in opportunistic networks has been a hot topic. For the video transmission applications in opportunistic networks, video data scheduling strategies have very important effects on the experience of users watching the video. Most of existing studies on data scheduling strategies only focus on improving data delivery rate or reducing the data delay instead of considering the impact of special video coding structure on scheduling performance. This paper studies a mobile learning scene on the real campus map where students share videos via opportunistic networks, and proposes a scheduling strategy based on the importance of multimedia video frames.In the process of forwarding multimedia data, the data usually cannot be delivered successfully with one transmission, because the communication link between two nodes may be broken intermittently. Therefore, we need to slice the multimedia data into data fragments, and adopt a suitable data scheduling strategy to forward these data fragments in terms of video sharing, for a better campus mobile learning.The main contributions of this paper can be generalized as follows:(1)This paper puts forward a method to determine the video data fragment size. In order to forward multimedia messages completely and quickly in a limited time, nodes slice messages into several fragments and send these fragments separately in opportunistic networks. We mainly study the rule of fragments size effect on the performance of multimedia messages forwarding, and then put forward a method to determine the reasonable scope of the fragments size and gave an experience value. Then, we analyze the delay and message deliver radio under the Random Walk model of four classic routing schemes in ONE environment. The results show that the fragment size have positive effects on data forwarding.(2)This paper simulates a mobile learning scenario on the real campus map where the users share videos based on opportunistic networks and give full consideration of the node mobility, the authenticity of the scene and the applicability of the real application. In this real campus environment, where students can carry out mobile learning via intelligent wireless communication equipment at anytime and anywhere, and show the effectiveness of the scenario model through the experimental simulation.At the same time, due to the destination node receives only a part of video in opportunistic network within limited time, but the existing objective evaluation of video——Peak Signal to Noise Ratio need the compete video, so it does not apply to opportunistic network. This paper propose a suitable video objective evaluation for opportunistic network indexes:Jitter, Jitter is a GOP decoding rate caused by the failed delivered packets within TTL, which is because that packets have different delays since they leave the source nodes.(3)This paper designs a video transmission scheduling algorithm. In a campus mobile learning scenario, users usually hope to receive more video contents in a short period of time. In other words, the video may not have high quality formats, but offer more pictures seen by these users. In this paper, we combine video encoding, video rating index and users'need, and propose a scheduling strategy:Video IPB Frame Importance Scheduling, IPB-Frame, which is based on the importance of multimedia video frames. Through this video scheduling strategy, users can quickly get videos with high decoding rate and low Jitter from the scene. Furthermore, we verify the correctness of the proposed strategy and the efficiency of video transmission on the campus scenario through simulation experiments and users'subjective assessment of video.