= Solution
A <wireless sensor node> combines a sensor, signal conditioning and conversion, a processor, a radio and a power subsystem. It can use a <battery>, a wired supply where practical, or local harvesting such as light, vibration or a thermal gradient, usually with a storage <capacitor>, <supercapacitor> or rechargeable <battery> to bridge interruptions. Harvested power must meet the time-averaged demand and storage must supply peak radio current.
Reduce power by <duty cycling> the sensor, processor and radio; use a low-leakage sleep mode and switch off unused peripherals. Buffer and batch data, transmit fewer unnecessary bits, use event-triggered acquisition when it meets the application, and reduce retries with a reliable link and an appropriate transmit-power level. Include wake-up, sensing, processing and communication <energy> in the budget: reducing payload alone may not reduce a radio dominated by startup overhead.
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