Wednesday, 23 July 2014
Cooperative Caching for Efficient Data Access in Disruption Tolerant Networks
COOPERATIVE CACHING FOR EFFICIENT DATA ACCESS IN DISRUPTION TOLERANT NETWORKS
Disruption tolerant networks (DTNs) are characterized by low node density, unpredictable node mobility, and lack of global network information. Most of current research efforts in DTNs focus on data forwarding, but only limited work has been done on providing efficient data access to mobile users. In this paper, we propose a novel approach to support cooperative caching in DTNs, which enables the sharing and coordination of cached data among multiple nodes and reduces data access delay. Our basic idea is to intentionally cache data at a set of network central locations (NCLs), which can be easily accessed by other nodes in the network. We propose an efficient scheme that ensures appropriate NCL selection based on a probabilistic selection metric and coordinates multiple caching nodes to optimize the tradeoff between data accessibility and caching overhead. Extensive trace-driven simulations show that our approach significantly improves data access performance compared to existing schemes.
Although forwarding schemes have been proposed in DTNs there is limited research on providing efficient data access to mobile users, despite the importance of data accessibility in many mobile applications. For example, it is desirable that smartphone users can find interesting digital content from their nearby peers. In vehicular ad-hoc networks (VANETs), the availability of live traffic information will be beneficial for vehicles to avoid traffic delays. In these applications, data are only requested by mobile users whenever needed, and requesters do not know data locations in advance. The destination of data is, hence, unknown when data are generated. This communication paradigm differs from publish/subscribe systems in which data are forwarded by broker nodes to users according to their data subscriptions. Appropriate network design is needed to ensure that data can be promptly accessed by requesters in such cases.
DISADVANTAGES OF EXISTING SYSTEM:
· It makes difficult to determine appropriate caching locations for reducing data access delay.
· It is hard to optimize the tradeoff between data accessibility and caching overhead.
DISRUPTION tolerant networks (DTNs)  consist of mobile devices that contact each other opportunistically. Due to the low node density and unpredictable node mobility, only intermittent network connectivity exists in DTNs, and the subsequent difficulty of maintaining end-to end communication links makes it necessary to use “carry and- forward” methods for data transmission.
The basic idea is to intentionally cache data at a set of network central locations (NCLs).
We propose a novel scheme to address the afore mentioned challenges and to efficiently support cooperative caching in DTNs. Our basic idea is to intentionally cache data at a set of network central locations (NCLs), each of which corresponds to a group of mobile nodes being easily accessed by other nodes in the network. Each NCL is represented by a central node, which has high popularity in the network and is prioritized for caching data. Due to the limited caching buffer of central nodes, multiple nodes near a central node may be involved for caching, and we ensure that popular data are always cached nearer to the central nodes via dynamic cache replacement based on query history. Our detailed contributions are listed as follows:
· We develop an efficient approach to NCL selection in DTNs based on a probabilistic selection metric. The selected NCLs achieve high chances for prompt response to user queries with low overhead in network storage and transmission.
· We propose a data access scheme to probabilistically coordinate multiple caching nodes for responding to user queries. We furthermore optimize the tradeoff between data accessibility and caching overhead, to minimize the average number of cached data copies in the network.
· We propose a utility-based cache replacement scheme to dynamically adjust cache locations based on query history, and our scheme achieves good tradeoff between the data accessibility and access delay.
ADVANTAGES OF PROPOSED SYSTEM:
· Popular data are always cached nearer to the central nodes via dynamic cache replacement.
· It is an efficient technique.
ü Speed - 1.1 Ghz
ü RAM - 512 MB(min)
ü Hard Disk - 40 GB
ü Key Board - Standard Windows Keyboard
ü Mouse - Two or Three Button Mouse
ü Monitor - LCD/LED
• Operating system : Windows XP
• Coding Language : Java
• Data Base : MySQL
• Tool : Net Beans IDE
Wei Gao, Guohong Cao, Arun Iyengar and Mudhakar Srivatsa, “Cooperative Caching for Efficient Data Access in Disruption Tolerant Networks” IEEE TRANSACTIONS ON MOBILE COMPUTING, VOL. 13, NO. 3, MARCH 2014