RUDN University mathematicians modeled a network with simultaneous signal distribution and physical layer security

RUDN University mathematicians with colleagues from Portugal, Saudi Arabia and Sri Lanka for the first time investigated a wireless network model with NOMA and PLNC technologies . It allows serving a large number of users at once, while ensuring security. The results are published in IEEE access.

For more efficient operation of wireless networks, the NOMA technology was introduced (Non-Orthogonal Multiple Access). Its essence is that the station serves several users at the same time, and using the same frequency bands. The base station sends superimposed signals to two users simultaneously. The device that turned out to be closer to the station subtracts the part of the signal that does not belong to it and decodes only its own. The device that turned out to be further perceives the signal of a first user as noise and detects only its own signal. The problem with this approach is security. It is necessary to ensure that an attacker cannot read someone else’s signal instead of a first user. To do this, it is proposed to use the so-called physical layer network coding (PLNC). However, this combination has only been studied for a small number of users. RUDN University mathematicians with colleagues from Portugal, Saudi Arabia and Sri Lanka for the first time modeled the NOMA – PLNC network with any number of users.

“NOMA allows many users to share the same block of time and frequency resources. In everyday life, people often use mobile applications to exchange some sensitive messages – bank details, medical data, command messages in military services. Therefore, it is important to ensure the security of the network. To solve these problems, a new idea of security at the physical layer is proposed,” said Ammar Muthanna, PhD, Director of the Research Center for Wireless 5G Networks Simulation of RUDN University.

Mathematicians proposed a model in which the base station serves any number of pairs of users. A pair means two devices located in the near and far zone from the station. The system also has a listening device, or interceptor. The network is built on the principle of NOMA and PLNC coding. At the first stage, all devices send signals to the base station, which splits them into pairs and assigns timeslots. At the second stage, the station encodes the signals using PLNC and sends them out simultaneously according to the NOMA principle. 

RUDN University mathematicians not only investigated the model in computer simulation, but also obtained exact mathematical expressions for calculating network performance. By substituting specific indicators of the system, you can get exact values, for example, for the probability of a network break and the probability of information leakage. 

“Although some authors have already proposed using NOMA-PLNC schemes, the study of such a network with an arbitrary number of users remained an open question. In practice, each cell in a cellular network operates with a large number of users, so it was important to develop a suitable cellular network model with any number of users,” said Ammar Muthanna, PhD, Director of the Research Center for Wireless 5G Networks Simulation of RUDN University.