This course provides an in-depth coverage of modern mobile air-interfaces, focusing mainly on the fourth (4G) and fifth generation (5G) of cellular networks. Following the introduction to multicarrier transmission, the key elements of layer 1, 2, and 3 of air interfaces of the 4G and 5G systems are covered in detail. Frequency division duplex and time division duplex solutions are compared and contrasted, and the differences between two main frequency ranges (i.e., below and above 6 GHz) are highlighted. Finally, the last segment of the course covers some more advanced topics, such as carrier aggregation, dual connectivity, massive machine type communication, and ultra-reliable low latency communication. Students will get the latest updates from the 3GPP standardization process as they become available, and study the impact of these changes on the performance improvement of mobile networks. Additionally, students will be exposed to practical problems that operators and infrastructure vendors are facing on daily basis. Two course projects will help students to supplement the learning material within the area of their own interest. Also, guest lecturers from major infrastructure vendors and operators will be invited to complement the lecture material.