# Energy Consumption Analysis of LPWAN Technologies and Lifetime Estimation for IoT Application
## 3 Generic Energy Consumption Paradigm  
The energy consumption paradigm is discussed in this section and demonstrated using Figure 3. The autonomy of sensing and sending the data from a sensor node is a composite of divergent power consuming elements. In most of the sensor units, battery is the only source of power. Thereby, it is paramount to consider each element accountable for power consumption to calculate energy efficiency and its battery lifetime. The sensor unit has different operating modes imparting energy dissipation for the LPWAN based wireless communication. Broadly, this can be divided into two modes: _Non-active and Active period_. Non-active period constitutes of sleep and idle mode during which most of the peripherals of the sensor node are not performing any task. In the same context, the device moves to active mode where the processing happens, message packet is formed, and eventually data is transmitted using the LPWAN radio. The total energy spent by the end sensor node is the aggregated value of energy spent during sleep and energy spent during the active period. Energy spent during sleep is calculated by the total power consumed during the sleep period. Energy spent during an active period is the total energy spent during _Device wakeup_ (warming up the micro-controller and initializing the end-device); _Sensor processing_ (fetching the sensor value, this involves reading, parsing the sensor values and time involved for this activity); _Data processing_ (processing the data and preparing packet frame); _Transceiver pre-processing_ (transmitting the packet to transceiver which involves activating the radio for transmission mode); _Radio transmission_ (utilizing radio for packet transmission, this depends upon LPWAN protocol, size of the payload and time-period for which radio is used); _Wait/Rx_ (energy spent during the receive window or wait period to receive the acknowledgement); and lastly _post processing_ (energy spent to stop all the aforementioned activity and going back to sleep again). Along with the energy consumed in the active period, the total energy spent is affected by three other major factors-battery used, firmware, and hardware. The impact of battery over the energy consumption by the end-device is discussed in Section 6. For each LPWAN protocol, there are a lot of hardware and firmware production partners with respective design detailing. Thus, the energy consumption may vary for each device. From a hardware perspective, the Printed Circuit Board (PCB) design, external hardwares such as Real Time Clock (RTC), internal frequency of the Micro-controller Unit (MCU), efficiency to handle number of instructions and other factors such as interrupt service routines impact the total energy consumption of the node. Different elements of the node active period depend upon the hardware efficiency such as processing of the sensor data and creating the packet for transmission. Also, on the other side firmware can alter the efficiency of handling the hardware by the inclusion of a timer, polling, software-based interrupts, and likewise approach. Thereby, it is essential to measure the energy consumption while excluding all the aforementioned factors to the nearest utilization point.