As audio and video applications have proliferated on the Internet, caching multimedia objects in transcoding proxies has become an important technology for adapting the same multimedia object to meet diverse needs of various mobile appliances. In this paper, the problem of caching multimedia objects in transcoding proxies, i.e., determining the proper versions of the same multimedia object to be cached at selective nodes in a network such that the specified objective is achieved, is addressed. First, a novel model, which is formulated as an optimization problem by combining both transcoding cost and transmission cost in a cooperative way, is presented. Second, an optimal solution is derived for computing the optimal locations, which is also extended to solve the problem of optimally deciding the locations for placing a fixed number of versions of the same multimedia object in a network since caching more objects will generate great overhead as well. Finally, the performance of the proposed model is evaluated on different performance metrics through extensive simulation experiments.

Transparent data replication is a promising technique for improving the system performance of a large distributed network. Transcoding is an important technology which adapts the same multimedia object to diverse mobile appliances; thus, users' requests for a specified version of a multimedia object could be served by a more detailed version cached according to transcoding. Therefore, it is articularly of theoretical and practical necessity to determine the proper version to be cached at each node such that the specified objective is achieved. In this paper, we address the problem of multimedia object placement for transparent data replication. The performance objective is to inimize the total access cost by considering both transmission cost and transcoding cost. We present optimal solutions for different cases for this problem. The performance of the proposed solutions is evaluated with a set of carefully designed simulation experiments for various performance metrics ver a wide range of system parameters. The simulation results show that our solution consistently and significantly outperforms comparison solutions in terms of all the performance metrics considered.

Web caching is an important technology for improving the scalability of Web services. One of the key problems in coordinated enroute Web caching is to compute the locations for storing copies of an object among the enroute caches so that some specified objectives are achieved. In this article, we address this problem for tree networks, and formulate it as a maximization problem. We consider this problem for both unconstrained and constrained cases. The constrained case includes constraints on the cost gain per node and on the number of object copies to be placed. We present dynamic programming-based solutions to this problem for different cases and theoretically show that the solutions are either optimal or convergent to optimal solutions. We derive efficient algorithms that produce these solutions. Based on our mathematical model, we also present a solution to coordinated enroute Web caching for autonomous systems as a natural extension of the solution for tree networks. We implement our algorithms and evaluate our model on different performance metrics through extensive simulation experiments. The implementation results show

In this paper, we address present an optimal solution for the problem of multimedia object placement for hybrid transparent data replication. The performance objective is to minimize the total access cost by considering both transmission cost and transcoding cost. The performance of the proposed solution is evaluated with a set of carefully designed simulation experiments for various performance metrics over a wide range of system parameters. The simulation results show that our solution consistently and significantly outperforms comparison solutions in terms of all the performance metrics considered.

Transcoding proxy caching is an important technology for improving the services over Internet, especially in the environment of mobile computing systems. In this paper, we address cooperative determination on cache replacement candidates for transcoding proxies. An original model which determines cache replacement candidates on all candidate nodes in a coordinated fashion with the objective of minimizing the total cost loss is proposed. We formulate this problem as an optimization problem and present a low-cost optimal solution for deciding cache replacement candidates.