Abstract: With the popularization of 5G technology, the Internet of Things (IoT) has developed unprecedentedly, and physical layer security authentication technologies for IoT devices have gradually garnered attention. This article focuses on electronic fingerprint technology, analyzing its possible future development directions from two aspects: artificially increasing signal features and further exploring inherent signal features. It also lists representative research achievements from the past three years based on literature, elaborates on their research methods, and discusses potential issues.
1. Introduction
1.1 Background of Electronic Fingerprint Research With the rapid development of 5G technology, broader communication capabilities and more flexible resource allocation strategies have greatly accelerated the popularization of the Internet of Things (IoT). Research indicates that the number of globally connected IoT devices has exceeded 1.23 billion and is expected to reach 2.7 billion by 2025. In the context of an interconnected world, security risks have become more pronounced: due to the nature of IoT network deployment, terminal devices do not always possess sufficient computing power and storage capacity to support complex dynamic encryption protocols in order to maintain low overhead. Therefore, to reduce and avoid risks, physical layer security authentication strategies have become a necessary choice. Physical layer security authentication technology is a means of verifying the security and compliance of physical devices and communication media. During wireless communication, devices register unique physical layer characteristics at the base station (or access point), which are more difficult for attackers to clone or intercept compared to keys; at the same time, physical layer authentication does not require terminal devices to perform software-level configurations, thus lowering performance requirements and making it more suitable for large-scale IoT application scenarios. Just as humans have unique biological fingerprint characteristics, this unique authentication identifier in networks is called an electronic fingerprint, with radio frequency fingerprint (RFF) being a representative example. 1.2 Generation of Radio Frequency Fingerprints In general, the transmitter of a wireless communication system can be simplified as follows: user information from the upper layers is encapsulated through the IP layer and MAC layer, then passed down to the physical layer, where the encoded digital signal is converted into an analog signal by a Digital Analog Converter (DAC); through a Local Oscillator (LO), the baseband signal is converted into a radio frequency signal; the radio frequency signal is amplified by a Power Amplifier (PA) and then filtered through a shaping filter, finally transmitted via a compatible antenna, as shown in Figure 1. Theoretically, the hardware in the above process should not affect the communication signal, but in practice, due to limitations in production technology, the analog circuits of devices will inevitably introduce random errors, such as non-linearity from the DAC, signal IQ gain imbalance caused by mixers, non-linear portions of the PA operating region, and slight differences caused by clock jitter, etc. [2]. These differences do not affect communication quality but will still be reflected in the signal. Radio frequency fingerprint technology utilizes the