*2.2. Energy and Power Consumption*

There are challenges to solve in IoT, for instance, the amount of energy that each accessory requires and the coexistence of thousands of wireless devices that may use different technologies for communicating [13]. In particular, coexistence is a severe threat to IoT, since the devices that are trying to communicate may collide with each other resulting in data lost, rendering the sensors useless. While there is substantial work on coexistence for Bluetooth, WiFi, and IEEE 802.15.14 standards [14], the forecast includes thousands of devices in a narrow range. This also considers the application of IoT to manufacturing and much more, which is called Industrial Internet of Things (IIoT), and it is based on the possibility of creating large-scale deployments. Consequently, some approaches include using a modified Medium Access Control (MAC) protocol. Nevertheless, there are multiple limitations as described by [15].

Another challenge of IoT is power consumption, in this sense, Mahmoud and Mohamad [16], have presented a study of wireless technologies for IoT applications. Their study was focused on the importance of using low-power wireless techniques by introducing a comparative between different low-power wireless communication techniques such as ZigBee, Low-Power WiFi, 6LowPAN, and LPWA.
