Energy Usage in Sensor Nodes

Data transmission and reception, and sensing are the prime cosumers of power in a sensor node . In other words Transceiver, Controller, Sensors and to some extent the memory are the components that feed on the avaialable energy in a sensor node.

Transceiver is costliest in terms energy usage. A bit transmitted or received is equal to 1500-2700 instructions being executed. Hence it is adviceable to put sensor nodes(transceivers) to sleep when not is use. There are three states, sleep state, operational state and idle sate. Operational state consumes the max, Idle state being next and sleep state consumes the least.. The energy required to change state from sleep to active is considerable, so one has decide on when a sensor node should sleep and when should it be awake.

The energy cosumption of each component is described below
Microcontroller: The MSP430 family features a wider range of operation modes: One fully operational mode, which consumes about 1.2 mW (all power values given at 1 MHz and 3 V). There are four sleep modes in total. The deepest sleep mode, LPM4, only consumes 0.3 μW, but the controller is only woken up by external interrupts in this mode. In the next higher mode, LPM3, a clock is also still running, which can be used for scheduled wake ups, and still consumes only about 6 μW.
Memory: The main consumer in memory is the Flash Memory. Reading, Writing and Erasing flash memory all consume energy. Among them writing consumes the most energy.
Transreceiver: Energy is consumed in transreceiver during transmission, reception, start up (switch off to switch on). The following example explains the energy consumption pattern. µAMPS -1 consumes 279mW for reception, 151 mW for transmission and 58.7mW for start up.
Sensors: Predicting power consumption of sensors is not easy task, as variety of sensors consume different amount of energy. Passive sensors consume very less energy and the energy consumed by them is negligible compared to other energy consumption however active sensors consume considerable amount of energy.