ABSTRACT
Contents Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 10.2 Last Mile Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
10.2.1 Choosing Wireless as a Last Mile Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 10.2.2 Importance of Last Mile for Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
10.3 Physical Layer Security Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 10.3.1 Properties of Wireless Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 10.3.2 Attacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
10.3.2.1 Secrecy Attacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 10.3.2.2 Authentication Attacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 10.3.2.3 Data Integrity Attacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 10.3.2.4 Robustness Attacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
10.3.3 Performance Metrics of Physical Layer Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 10.3.3.1 Information Theoretical Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 10.3.3.2 Quality of Service-Related Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
10.4 Current Physical Layer Security Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 10.4.1 Network Security Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 10.4.2 Encryption Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 10.4.3 Spread Spectrum-Based Eavesdropping Mitigation Techniques . . . . . . . . . . . . . . . 246
10.5 Future Physical Layer Security Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 10.5.1 Signaling-Based Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
10.5.1.1 Beamforming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 10.5.1.2 Artificial Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 10.5.1.3 Interference Shaping-Based Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
10.5.2 Filter-Based Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 10.5.2.1 Single-Carrier Online Eavesdropping Mitigation Techniques . . . . . . 250 10.5.2.2 Multicarrier Techniques: FBMC Filter Hopping. . . . . . . . . . . . . . . . . . . . 251
10.5.3 Physical Layer Key Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254 10.5.4 Considerations on Implementation in Future Mobile Networks . . . . . . . . . . . . . . 256
10.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
Abstract Mobile networks have become very widely used in recent years, with expanding possibilities for usage ranging from personal life to business needs. This increased usage has brought more security problems and the importance of maintaining security has been also raised. Mobile networks consist of two main parts, including wired backhaul and wireless last mile. Wired backhaul is the part between base station and the core network. It is a highly reliable network with high data rates. Security in this part is very important. In its cable-based physical layer-the part where physical signals are carried-data are hard to acquire, as physical protection of cables and devices is possible. The last mile is the last part where the user is served. This link has to be wireless for the mobility of users. Wireless medium has an open nature; hence, wireless links are more vulnerable to physical layer attacks compared to their wired counterparts. In this chapter, a general understanding will be given on why wireless technologies are often chosen as a last mile technology and why maintaining security is a challenge. Moreover, the current and future solutions to protect the wireless last mile from physical layer attacks will be explained.
