Many design aspects affect energy consumption, ranging from the hardware components, operations of the sensors, the communication protocols, the application algorithms, and the application duty cycle.
B (node 9) was chosen as the network DAG root because of its application duty cycle.
β·|δ k,n | is the sleeping offset and represents the time the node will wake up before the start of the next application duty cycle.
The nodes alternate between wake and sleep states, and the amount of time spent in each phase is determined by the application duty cycle.
According to our application-driven concept, synchronization is achieved between the nodes that run the same applications or between the nodes that have the same application duty cycle, by considering their duty cycles.
The time the nodes are sleeping (T OFF) is defined as T Cycle−T ON where T Cycle is the application duty cycle time and T ON is the time the nodes are awaked during each duty cycle.
In our proposal, the subset of nodes running the same application forms a "subnetwork" with multi-hop connectivity and application packets carry out also information about the application duty cycle (T CYCLE and T ON) that is used to create and maintain the DAGs in which not only the nodes running the same application but also the nodes having the same application duty cycle can be "grouped".
As such, the synchronization algorithm takes advantage of the application query packets that are sent by the sink nodes once in every application duty cycle to maintain the sensor nodes synchronized.
Each query time reception is affected by those different network delays, and the sensor nodes upon their reception will adjust their sleep time in order to try to wake up at same time on the next application duty cycle.
The novelty of our contribution comes from (1) the adaptation of the well-known exponentially weighted moving average technique to wireless mesh network scenarios and (2) using this mechanism to control the behavior of sensor nodes so that they become synchronized in relevant time instants which are defined by their application duty cycles.
§ 301.3 Application for duty-free entry of scientific instruments.
