核心概念
The proposed modulation scheme divides the RIS phase-shift matrix into symbol-invariant and symbol-varying components to address the ambiguity problem in RIS-assisted symbiotic radio systems, and the optimal design of these components is derived to improve the BER performance of both primary and secondary transmissions.
要約
The paper proposes a novel modulation scheme for RIS-assisted symbiotic radio (SR) systems to address the ambiguity problem. The key idea is to divide the RIS phase-shift matrix into two components: the symbol-invariant component used to assist the primary transmission, and the symbol-varying component used to carry the secondary signal.
To optimize these two components, the authors focus on the detection of the composite signal formed by the primary and secondary signals, and formulate a problem to minimize the bit error rate (BER) of the composite signal. By solving this problem, they derive the closed-form solution of the optimal symbol-invariant and symbol-varying components, which is related to the channel strength ratio of the direct link to the reflecting link.
The proposed modulation scheme can address the ambiguity problem by regarding the symbol-invariant component as a virtual direct link, and at the same time help enhance the primary transmission when the direct link is weak. Theoretical BER performance analysis is provided, and simulation results demonstrate the superiority of the proposed scheme over conventional modulation schemes.
統計
The channel response from the primary transmitter to the cooperative receiver is denoted by hd.
The channel response from the primary transmitter to the RIS is denoted by f.
The channel response from the RIS to the cooperative receiver is denoted by hr.
The transmit power is denoted by p.
The normalized constellation sets of the primary and secondary signals are denoted by As and Ac, respectively.
引用
"To address the ambiguity problem, in this paper, we propose a novel modulation scheme for RIS-assisted SR."
"To optimize these two components, this paper aims to optimize these two components to improve both the BER performance of the primary and secondary transmissions."
"It is shown that the optimal design of the symbol-invariant and symbol-varying components is related to the channel strength ratio of the direct link to the reflecting link, which determines the energy allocated to the symbol-invariant and symbol-varying components."