r simply a wearable refers to a device that can be worn on the body. This rapid rise in popularity was spurred, in part, by technological innovation. Emerging system on chip (SoC) and system in package (SiP) have scaled down the printed circuit board (PCB) size, decreased power consumption, and most importantly, have made it possible to design wearables in a variety of desired shapes (Figure 1.4). Wearable devices provide easier access to information and convenience for their users. They have varying form factors, from low-end health and fitness trackers to high-end virtual reality (VR) devices, augmented reality (AR) helmets, and smart watches. These devices can collect data on heart rates, steps, locations, surrounding buildings, sleeping 1 Introduction to 5G and Beyond Network VR/AR helmets Smart Headphones glasses Fitness Smart trackers clothing Medical Watches sensors Smart shoes Figure 1.4 Wearable devices may have varying forms, from small medical sensors to entertainment helmets. cycles, and even brain waves. Yet computing limitations continue to hinder wearables' ability to process data locally. As a result, most devices choose to offload their collected data to other powerful devices or to the clouds. This necessary communication plays a key role in wearable devices. Different applications provided by different wearables may have varying communication requirements. For example, while medical sensors have stringent requirements on latency and reliability, they have a low data rate need. On the other hand, AR/VR devices need both high throughput and low latency for a better user experience. Wearable devices may not be able to take full advantage of current communication archi- tecture, due to their potential cost and hardware complexity. On the other hand, wearable devices have succeeded in becoming more and more involved in everyday activities requir- ing voice, image, and video inputs. Human beings are generally sensitive to an approximate 100 ms audible delay and can catch visual delays of less than 10