Passive Beamforming And Information Transfer For Intelligent Reflecting Surface Aided Wireless Systems

Intelligent reflecting surface(IRS)is a large electromagnetic metasurface,consisting of a large number of low-cost,almost passive Reflection elements.By effectively designing the phase shifts of the reflection elements,IRS can realize the directional reflection of incident electromagnetic waves to artificially reconfigure the wireless propagation environment,thereby improving the performance of the wireless communication systems.The IRS provides a promising green communications technology.In order to realize the implementation and application,the IRS needs to have information transmission capability to keep the coordination and synchronization with its served system and to ensure its normal working states.RIS information transfer can be achieved by equipping a RIS with a dedicated radio frequency(RF)chain,but this compromises the “passive” nature of the RIS by consuming extra time/frequency resources and increases the hardware cost for RIS implementation.In order to transfer the IRS information more efficiently,this paper proposes a joint passive beamforming and information transfer(PBIT)mechanism for IRS based on spatial modulation.In the PBIT scheme,the IRS information is modulated to the“on/off” states of its reflection elements,and the receiver obtains its information by detecting weather the corresponding IRS element is activated or not.Thus,the PBIT scheme realizes the transmission of IRS information without increasing any additional hardware cost,energy consumption,or time/frequency resource.In the IRS-aided PBIT systems,the “on/off” state of each RIS element exists randomness to carry the IRS information,which leads to the optimization of RIS's phase shift stochastic program.In addition,the simultaneous transmission of the transmitters and the IRS makes the design of the receiver a bilinear signal detection problem.In response to the two problems,we propose the solutions for the signal-user single input multiple output(SIMO)PBIT systems and the multiuser SIMO PBIT systems.Specifically,in the single-user SIMO PBIT systems: for the passive beamforming design,we propose a received signal-to-noise ratio maximization algorithm by resorting to the semidefinite relaxation;for the bilinear receiver design,we design a rank-1-matrix decomposition based two-step solution.For the passive beamforming design in the multi-user SIMO PBIT system,we propose an alternating optimization algorithm based on sampling average approximation,and a simplified optimization algorithm that strikes a feasibel balance between computational complexity and performance.For the receiver design in the multi-user SIMO PBIT system,we designed a turbo detection algorithm based on message passing.We conduct numerical simulations on MATLAB software to verify the effectiveness of the proposed algorithms.The results show that the proposed optimization algorithm can significantly increase the user reachable rate,and the proposed detection algorithm can simultaneously recover the user symbols and the IRS data on a relatively accurate bit error rate.