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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 particularly 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 minimize 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 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

In this paper, we address the problem of cache replacement for transcoding proxy caching. Transcoding proxy is a proxy that has the functionality of transcoding a multimedia object into an appropriate format or resolution for each client. We first propose an effective cache replacement algorithm for transcoding proxy. In general, when a new object is to be cached, cache replacement algorithms evict some of the cached objects with the least profit to accommodate the new object. Our algorithm takes into account of the inter-relationships among different versions of the same multimedia object, and selects the versions to replace according to their aggregate profit which usually differs from simple summation of their individual profits as assumed in the existing algorithms. It also considers cache consistency, which is not considered in the existing algorithms. We then present a complexity analysis to show the efficiency of our algorithm. Finally, we give extensive simulation results to compare the performance of our algorithm with some existing algorithms. The results show that our algorithm outperforms others in terms of various performance metrics.

Transcoding is a promising technology that allows systems to effect a quality-versus-size tradeoff on multimedia objects. As audio and video applications have proliferated on the Internet, caching in transcoding proxies has become an important technique for improving network performance, especially in mobile networks. This article addresses the problem of coordinated enroute multimedia object caching in transcoding proxies for tree networks. We formulate this problem as an optimization problem based on our proposed model, in which multimedia object caching decisions are made on all enroute caches along the routing path by integrating both object placement and replacement policies and cache status information along the routing path of a request is used to determine the optimal locations for caching multiple versions of the same multimedia object. We propose an optimal solution using dynamic programming to compute the optimal locations. We also extend this solution to solve the same problem for several constrained cases, including constraints on the cost gain per node and on the number of versions to be placed. Our model is evaluated on different performance metrics through extensive simulation experiments. The implementation results show that our model significantly outperforms existing models that consider Web caching in transcoding proxies either on a single path or at individual nodes.

Multimedia object caching, by which the same multimedia object can be adapted to diverse mobile appliances through the technique of transcoding, is an important technology for improving the scalability of Web services, especially in the environment of mobile networks. In this paper, we address the cache replacement problem for multimedia object caching by exploring the aggregate effect of caching multiple versions of the same multimedia object. First, we present an optimal solution for calculating the minimal access cost of caching multiple versions of the same multimedia object. Second, based on this solution, we propose an effective cache replacement algorithm for multimedia object caching. Finally, we evaluate the performance of the proposed solution with a set of simulation experiments for various performance metrics over a wide range of system parameters.

Cache replacement in transcoding proxies is an important issue that affects the network performance. In this paper, we address the problem of coordinated multimedia object replacement in transcoding proxies for tree networks. First, we formulate this problem as an optimization problem. Second, we present an optimal solution for this problem. Finally, we conduct simulation experiments to evaluate the performance of our solution by comparison with some existing solutions. The simulation results show that our solution outperforms the existing solutions.

Web caching is an important technology for reducing Internet access latency, alleviating network traffic, and spreading server load. An important issue that affects the performance of web caching is object caching, which is used to distribute copies of the same object diversely over the Internet. In this paper, we present an overview of the state-of-art techniques for object caching over the Internet. We discuss several cases of object caching in the literature.

In this paper, we address the problem of cache replacement for transcoding proxy caching. First, an efficient cache replacement algorithm is proposed. Our algorithm considers both the aggregate effect of caching multiple versions of the same multimedia object and cache consistency. Second, a complexity analysis is presented to show the efficiency of our algorithm. Finally, some preliminary simulation experiments are conducted to compare the performance of our algorithm with some existing algorithms. The results show that our algorithm outperforms others in terms of the various performance metrics.

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.

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 of particularly theoretical and practical necessity to determine the proper versions to be cached at a node such that the specified objective is achieved. In this paper, we address the problem of multimedia object placement. The performance objective is to minimize the total access cost by considering both transmission cost and transcoding cost. We present an optimal dynamic programming-based solution for this problem. The performance of the proposed solutions 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.

Multimedia object caching, by which the same multimedia object can be adapted to diverse mobile appliances through the technique of transcoding, is an important technology for improving the scalability of Web services, especially in the environment of mobile networks. The performance of multimedia object caching mainly depends on how the objects are selected to be removed for a new object (multimedia object replacement) and where the different versions of a multimedia object are placed (multimedia object placement). In this paper, we address the problem of cache replacement for multimedia object caching. We first propose an optimal solution for this problem. 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.

Web caching, especially proxy caching, is an important technology for improving the efficiency of web content delivery. With the rapid growth of audio and video applications on the internet, caching media objects in transcoding proxies has become an important research topic in recent years. In this paper, we address the problem of optimally determining the locations for placing multiple versions of media objects in a network such that the objective specified is achieved. We present an original model, which makes caching decisions on all the en-route caches along the routing path in a coordinated way by integrating both media object placement and replacement policies, for this problem. We formulate this problem as an optimization problem and the optimal locations are obtained using a low-cost dynamic programming-based algorithm. We implement our algorithms and evaluate our model on different performance metrics through extensive simulation experiments. The implementation results show that our model significantly outperforms existing algorithms that consider media object placement or replacement at individual nodes only.

This paper addresses the problem of transcoding proxy placement for coordinated en-route Web caching for tree networks. We propose a model for this problem by considering all the nodes among the network in a coordinated way and formulate this problem as an optimization problem. We implement our dynamic programming-based algorithm and evaluate our model on different performance metrics through extensive simulation experiments. The implementation results show that our model outperforms the placement model for linear topology.