Abstract:

This paper investigates the design and performance optimization of transmission schemes in symbiotic radio systems empowered by intelligent reflection surfaces.In a system,the intelligent reflection surface helps the communication between the base station and the primary user.At the same time,the intelligent reflection surface acts as a backscatter device to generate secondary signals and transmit information to the secondary user by reflecting the signals transmitted by the base station.The intelligent reflection surface uses on-off keying to modulate the reflected signals by controlling the reflection units of the intelligent reflection surface.The secondary user uses energy detection to detect secondary symbols.Under the condition of ensuring the minimum transmission rate of the main transmission,the base station beamforming vector and the phase shift matrix of the intelligent reflection surface are jointly optimized to minimize the error probability of the secondary transmission.The original optimization problem is non-convex,and is transformed into two convex sub-problems by using semidefinite relaxation.The solution to the original problem is obtained by solving the two sub-problems alternatively.Finally,the computer simulation is performed to verify the theoretical analysis of the detection error probability and to evaluate the performance of the proposed scheme.The simulation results show that compared with the benchmark schemes,the proposed scheme not only improves the performance of the primary transmission system but also achieves a significantly lower bit error rate in the secondary transmission with a significantly higher bit error rate reduction rate as the transmit power,number of antennas,and number of reflective elements in the intelligent reflection surface increase.

Key words: intelligent reflection surface, symbiotic radio, bit error rate, beamforming