ABSTRACT
In the Internet of Things, a large number of sensors will be installed anywhere and everywhere on the human body or in our environment. They will collect a range of physical and environmental information which will be sent to the internet via some sort of connectivity path. Intermittent operation is one of the key techniques for low power VLSI systems including radio, which suggests the use of energy-efficient Time Division Multiple Access protocols such as IEEE 802.11. This chapter introduces state-of-theart techniques for clock generation and compares a crystal oscillator and RC oscillator. Relaxation oscillators remain of high interest in research as their variability is related to capacitance which is small in the CMOS process, they have a resistor which is easy to trim and their mobility which is mostly temperature-sensitive. A crystal oscillator is widely used because it demonstrates high accuracy and its power consumption is extremely low.
