Cooperative Caching in Wireless Multimedia Sensor Networks

Abstract

The recent advances in miniaturization and the creation of low-power circuits, combined with small-sized batteries have made the development of wireless sensor networks a working reality. Lately, the production of cheap complementary metal-oxide semiconductor cameras and microphones, which are able to capture rich multimedia content, gave birth to what is called Wireless Multimedia Sensor Networks (WMSNs). WMSNs will boost the capabilities of current wireless sensor networks, and will fuel several novel applications, like multimedia surveillance sensor networks. WMSNs introduce several new research challenges, mainly related to mechanisms to deliver applicationlevel Quality-of-Service (e.g., latency minimization). To address this goal in an environment with extreme resource constraints, with variable channel capacity and with requirements for multimedia in-network processing, the caching of multimedia data, exploiting the cooperation among sensor nodes is vital. This article presents a cooperative caching solution particularly suitable for WMSNs. The proposed caching solution exploits sensor nodes which reside in "positions" of the network that allow them to forward packets or communicate decisions within short latency. These socalled "mediator" nodes are selected dynamically, so as to avoid the creation of hot-spots in the communication and the depletion of their energy. The mediators are not more powerful than the rest of the nodes, but they have some special role in implementing the cooperation among the sensors. The proposed cooperative caching protocol includes components for locating cached data as well as for implementing data purging out of the sensor caches. The proposed solution is evaluated extensively in an advanced simulation environment, and it is compared to the state-of-the-art cooperative caching algorithm for mobile ad hoc networks. The results confirm that the proposed caching mechanism prevails over its competitor.

Wireless Multimedia Sensor Networks: Current Trends and Future Directions

“…However, there is an overhead of using the limited buffer space at the intermediate node for caching packets for other nodes, as well as performing timely storage and flushing operations on the buffer. Therefore, this rises the need for in-network storage mechanism [ 59 ] or collaboration-based distributed cache points over the network [ 60 ]. Some mechanisms as in DWT-Reliable [ 61 ] and MMDR [ 62 ] provide reliability for multimedia streaming transmission in WMSN by exploiting the source video coding techniques by which the source traffic can be splitted into multiple streams.…”

The new challenge: mobile multimedia sensor networks

“…• Cooperative caching issue Dimokas et al (2008). This is a problem of letting small sensor nodes to collaborate with each other to cache multimedia data in network to satisfy some application-level Quality-of-Services.…”

“…• Data replication issue. This issue is an extended research problem of both data replication issue Hara et al (2006) in wireless mobile sensor networks and cooperative caching issue Dimokas et al (2008) in wireless multimedia sensor networks. In this problem, multimedia data (e.g., images) of mobile source nodes are cached in a large number of small scalar sensor nodes, by having data replication of pieces of multimedia data.…”

Multi-Constrained Routing Algorithm for Multimedia Communications in Wireless Sensor Networks

“…Here we may take these landmarks as sink nodes (multiple sinks are used to improve the positioning precision of source nodes). We also assume that these sink nodes have known their respective hop-counts to some source node, e.g., the node s (6,7,4,3), where the numbers between the pair of parentheses form the logical coordinate vector of node s. Each of elements in this vector in order represents the respective hop-count from each sink to node s. The serial number of each element is the ID of its corresponding landmark (sink node). So the actual coordinate value of source node relative to these sinks can be computed in the following manner:…”

“…For multimedia applications, routing protocols should aim at providing timeliness and reliability services for them, and manage to balance the energy consumption in sensor nodes [5]. Additionally, routing protocols designed for multimedia communications are supposed to have better capacities of message suppression and data aggregation than common applications, because of more data redundancies in multimedia applications [6]. Therefore, routing algorithms working in multimedia sensor networks should be able to not only provide QoS services for multimedia communications but also suffice for other communication requirements in WSN (e.g., optimal energy consumption, localization, message suppression and data aggregation etc).…”