This document provides an introduction to 4th generation (4G) wireless networks. It discusses the history and evolution of previous mobile technologies (1G, 2G, 3G). 4G aims to provide higher data rates, seamless coverage, and support for multimedia services through an all-IP based network. The document outlines some key design objectives and technologies for 4G including addressing issues like heterogeneous networks, mobility management, quality of service, and security. It also discusses applications and challenges of 4G such as billing across multiple operators and reconfigurable terminal technology.