SPIN-IT: the PRISM project network protocol for image retrieval

The PRISM project was created to explore technologies for sharing pictures in a wireless network of imaging devices, including image discovery techniques, data routing, source and channel coding, and techniques for image mosaicing and image fusion (i.e., super-resolution). Through the PRISM project, we have developed a routing protocol for wireless ad hoc networks that supports efficient image retrieval based on metadata queries. In digital photography, metadata describes captured information about an image and provides the key element needed for advanced techniques for sharing pictures. Using metadata, devices connected to a wireless network can advertise data availability and query for desired data. These devices will, however, operate within a constrained environment - energy resources may often be limited, computational power may be minimal, and the wireless network bandwidth and range will likely be constrained. Our goal was to find an efficient way to utilize metadata to retrieve images in a wireless network of imaging devices while conserving energy and bandwidth. Building on the SPIN protocol for metadata negotiation, we designed SPIN-IT (Sensor Protocols for Information via Negotiation Image Transfer), a protocol where wireless imaging devices use metadata queries to retrieve desired pictures. This protocol provides low bandwidth query-based communication prior to the transfer of image data to set up routes to desired data rather than routes to specific nodes, making SPIN-IT a data-centric routing protocol. However, the advantage of a centralized approach is that the overhead and delay in finding the location of desired data is reduced. We simulated both SPIN-IT and the centralized model using the discrete event simulator ns, and we measured the delay and overhead incurred by each REQ for the different approaches. We describe the results of these initial experiments that determine when SPIN-IT is an efficient protocol for image retrieval in a wireless network.