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Environmental data collection applications typically use tree‐based routing topologies where each
routing tree is rooted at high‐capability nodes that sink data. Data is periodically transmitted from
child node to parent node up the tree‐structure until it reaches the sink. With tree‐based data
collection each node is responsible for forwarding the data of all its descendants. Nodes with a large
number of descendants transmit significantly more data than leaf nodes. These nodes can quickly
become energy bottlenecks. Once the network is configured, each node periodically samples its
sensors and transmits its data up the routing tree and back to the base station. For many scenarios,
the interval between these transmissions can be on the order of minutes. Typical reporting periods
are expected to be between 1 and 15 minutes; while it is possible for networks to have significantly
higher reporting rates. The typical environment parameters being monitored, such as temperature,
light intensity, and humidity, do not change quickly enough to require higher reporting rates.
In addition to large sample intervals, environmental monitoring applications do not have strict
latency requirements. Data samples can be delayed inside the network for moderate periods of time
without significantly affecting application performance. In general the data is collected for future
analysis, not for real‐time operation.
The most important characteristics of the environmental monitoring requirements are long lifetime,
precise synchronization, low data rates and relatively static topologies. Additionally it is not essential
that the data be transmitted in real‐time back to the central collection point. The data transmissions
can be delayed inside the network as necessary in order to improve network efficiency.

Figure 31 – Environmental Data Collection

252 ITU‐T's Technical Reports and Specifications