Directed Diffusion

sensor networks

• small and cheap nodes
• addition of sensing capability
• can coordinate to perform distributed sensing of environmental phenomena
• enable low maintenance sensing in more benign, but less accessible, environments

2 categories of sensor networks today

• large, complex sensor systems usually deployed very far away from the phenomena to be sensed, and employ complex signal processing algorithms to separate targets from environmental noise
• a carefully engineered network of sensors is deployed in the field, but individual sensors do not posses computation capability, instead transmitting time series of the sensed phenomena to one er more nodes which perform the data reduction and filtering

expected architectures

• a matchbox sized form factor
• battery power source
• power-conserving processor clocked at several 100 Mhz
• program and data memory amounting to several tens of Mbytes
• a radio modem
• analog-to ­digital conversion system on such nodes
• a sensor node may possess a GPS receiver

directed diffusion

• consists of several elements
• data is named using attribute-value pairs
• a sensing task is disseminated throughout the sensor network as an interest for named data
• this dissemination sets up gradients within the network designed to "draw" events
• events start flowing towards the originators of interests along multiple paths
• sensor network reinforces one, or a small number of these paths

interests and gradients

• an interest is injected into the network at some (possibly arbitrary) node in the network (sink)
• for each active task, the sink periodically broadcasts an interest message to each of its neighbors
• the initial interest contains a larger interval attribute
• this initial interest may be thought of as exploratory