发表时间:2014-08-08 阅读次数:997次

Converged networks

With diminishing returns in infrastructure-based investments,   the next wave for mobile data tsunami cannot always be tackled with infrastructure and bandwidth expansions. Upon a closer examination at the wireless traffic trend, it is observed that despite of their massive numbers, the amount of "unique" media content does not actually increase exponentially. In addition, even unique multimedia contents are not consumed with the same frequency, at least statistically. Studies have revealed that

  • 80% of the wireless traffic is from videos , many with applications that personalizes the viewing experience. In particular, personalized viewing experience can be achieved through content pushing/caching and time-shifting.
  • Only a small percentage, 5-10%, of popular contents are consumed by the majority of the mobile users, despite the large temporal variability in the content consumption time.

  

  

In light of the fact that the mobile media contents are highly diversified, a dramatic increase in mobile content deliverability can be achieved by exploiting the so-called content diversity (at application level) and network diversity (at infrastructure level), via approaches that take advantage of the computation and caching capabilities within the wireless networks.

The so-called converged network, which combines broadcasting with cellular, provides a highly efficient and practical means to simultaneously capture the content and network diversity gains.   The basic diagram of the converged network is depicted in Figure below. The network consists of two parts: a wireless broadcasting system and a cellular system. In particular, the converged network is capable of not only delivering the contents of high interest to all the users simultaneously, but also accommodating on-demand requests through unicasting, and thus significantly improves the network capacity. This strategy not only offloads the multimedia traffics from the cellular network, but also improves the user experience by eliminating download waiting time.

  

  

A number of topics are currently being investigated under the framework of converged networks. Among them:

  1. Content capacity: Despite the various schemes that exploit the content characteristics in wireless delivery, the content diversity has not been quantified under a unified framework, even under the simplest multiuser scenario. We are studying a novel information-theoretical formulation for the content delivery problem. In particular, the notion of wireless content rate is established, which, in contrast to the bit rate of a wireless unicast system, characterizes a direct relation between the content diversity and the content delivery capability of a wireless system.
  2. Pushed-based converged networks: we contribute to the design and theoretical understanding of push-based content delivery in a converged broadcasting and cellular network. Specifically, we are interested in analyzing the scheme in which the most popular contents are pushed through broadcasting to alleviate the cellular data bottleneck. To evaluate the performance gains of the converged network, we first develop a mathematic framework to model the converged network, the multimedia content characteristics and the mobile user behaviors. The improvement of the network capacity is then derived and quantified theoretically.
  3. Priority encoding for content diversity:Instead of broadcasting the popular contents individually, the content objects can be jointly encoded to save the wireless bandwidth. We are investigating the PET principle in wireless content delivery, in which intelligent encoding and user-end caching is employed based on the content degree-of-interests.
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