Intelligent reflecting surface (IRS) has recently emerged as a promising technology for beyond fifth-generation (B5G) and 6G networks conceived from metamaterials that smartly tunes the signal reflections via a large number of low-cost passive reflecting elements. However, the IRS-assisted communication model and the optimization of available resources needs to be improved further for more efficient communications. This paper investigates the enhancement of received power at the user end in an IRS assisted wireless communication by jointly optimizing the phase shifts at the IRS elements and its location. Employing the conventional Friss transmission model, the relationship between the transmitted power and reflected power is established. The expression of received power incorporates the free space loss, reflection loss factor, physical dimension of the IRS panel, and radiation pattern of the transmit signal. Also, the expression of reflection coefficient of IRS panel is obtained by exploiting the existing data of radar communications. Initially exploring a single IRS element within a two-ray reflection model, we extend it to a more complex multi-ray reflection model with multiple IRS elements in 3D Cartesian space. The received power expression is derived in a more tractable form, then, it is maximized by jointly optimizing the underlying underlying variables, the IRS location and the phase shifts. To realize the joint optimization of underlying variables, first, the phase shifts of the IRS elements are optimized to achieve constructive interference of received signal components at the user. Subsequently, the location of the IRS is optimized at the obtained optimal phase shifts. Numerical insights and performance comparison reveal that joint optimization leads to a substantial 37% enhancement in received power compared to the closest competitive benchmark scheme.

翻译：智能反射面（IRS）作为一种源自超材料的前沿技术，近期在超五代（B5G）和6G网络中崭露头角，该技术通过大量低成本无源反射元件智能调控信号反射。然而，为实现更高效的通信，IRS辅助通信模型及可用资源优化仍需进一步改进。本文通过联合优化IRS元件相位偏移及其部署位置，研究了IRS辅助无线通信中用户端接收功率的增强方法。基于传统弗里尔斯传输模型，建立了发射功率与反射功率之间的数学关系。接收功率表达式综合考虑了自由空间损耗、反射损耗因子、IRS面板物理尺寸及发射信号辐射方向图。同时，利用雷达通信现有数据推导出IRS面板反射系数的表达式。本研究从两射线反射模型中单一IRS元件的分析入手，将其扩展至三维笛卡尔空间内具有多个IRS元件的更复杂多射线反射模型。在推导出更易处理的接收功率表达式后，通过联合优化底层变量（IRS位置与相位偏移）实现接收功率最大化。为实现底层变量的联合优化，首先优化IRS元件的相位偏移，使用户处接收信号分量形成相长干涉；随后在获得的最优相位偏移条件下优化IRS部署位置。数值分析与性能对比表明，相较于最优竞争基准方案，联合优化可使接收功率提升37%。