Multiple antennas based wireless security enhancement in multiple access systems

Abstract

Wireless communication systems have evolved into various types of networks such as Long-Term Evolution (LTE) in cellular networks and Wi-Fi in wireless local area networks (WLAN) over the past decades. Wireless communications now become one of the most important factors and inevitable part of our daily life. Moreover, as the wireless communication techniques have been broadly utilized for our convenient life, wireless security threats have increased. Recently, physical layer security has attracted much attention in wireless communications since it guarantees the information-theoretic security against eavesdropping attacks. Although a lot of topics related to physical layer security have been investigated, issues in multiuser environments have been relatively less highlighted than those in single-user networks since the multiuser environment requires additional user scheduling process and it makes problems more complicated. In addition, there is still a significant gap between theoretical and practical perspectives on wireless security. Thus, it would be an important and challenging research topic to study wireless security issues from theory to practice. In this dissertation, we investigate wireless security enhancements in multiple access systems based on the notion of information-theoretic security such as multiuser diversity, artificial noise and multiple antenna techniques, and apply them to protect each user's physical layer identity against an implementable attack in a practical cellular system.