Ambient Backscatter Communication Based Cooperative Relaying for Heterogeneous Cognitive Radio Networks

In this paper, a new network model is pro-posed to improve the performance of the secondary channel in cognitive radio networks (CRNs) based ambient backscat-ter communication systems. This model is considered as a cooperative system with multi-secondary transmitter (ST) and multi-relay. The ST backscatters data to both the sec-ondary receiver (SR) and relay. Also it harvests energy from the signal emitted by the primary transmitter (PT) during the busy period. The relay activated by the ST user for-wards the information from ST to SR. During the idle period, the PT broadcast is interrupted and ST also performs ac-tive data transmission using the energy it has harvested. We aim to maximize the number of data transmitted to the SR. Therefore, how long the ST will perform backscattering, en-ergy harvesting and active data transmission is a problem to be solved. In such cooperative systems with multiple users, the solution of the problem becomes more complex. There-fore, the system model has been mathematically modeled and transformed into an optimization problem, considering that users are transmitting data using time division multiple ac-cess (TDMA) and non-orthogonal multiple access (NOMA) techniques. Numerical results showed that higher data rates were achieved in NOMA. Additionally, It has been seen that the proposed model performs better when compared to the existing approaches in the literature, where the ST can only harvest energy and transmit data actively or only transmit data with ambient backscatter communication.