Choi Jihyun, Cantos Luiggi, Choi Jinho, Kim Yun Hee
Department of Electronic Engineering, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu, Yongin-si 17104, Gyeonggi-do, Korea.
Department of Electronics and Information Convergence Engineering, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu, Yongin-si 17104, Gyeonggi-do, Korea.
Sensors (Basel). 2022 Jun 12;22(12):4449. doi: 10.3390/s22124449.
Recently, intelligent reflecting surfaces (IRSs) have drawn huge attention as a promising solution for 6G networks to enhance diverse performance metrics in a cost-effective way. For massive connectivity toward a higher spectral efficiency, we address an intelligent reflecting surface (IRS) to an uplink nonorthogonal multiple access (NOMA) network supported by a multiantenna receiver. We maximize the sum rate of the IRS-aided NOMA network by optimizing the IRS reflection pattern under unit modulus and practical reflection. For a moderate-sized IRS, we obtain an upper bound on the optimal sum rate by solving a determinant maximization (max-det) problem after rank relaxation, which also leads to a feasible solution through Gaussian randomization. For a large number of IRS elements, we apply the iterative algorithms relying on the gradient, such as Broyden-Fletcher-Goldfarb-Shanno (BFGS) and limited-memory BFGS algorithms for which the gradient of the sum rate is derived in a computationally efficient form. The results show that the max-det approach provides a near-optimal performance under unit modulus reflection, while the gradient-based iterative algorithms exhibit merits in performance and complexity for a large-sized IRS with practical reflection.
最近，智能反射面（IRS）作为一种有前途的解决方案，能够以经济高效的方式提升6G网络的多种性能指标，从而备受关注。为了实现大规模连接以提高频谱效率，我们将智能反射面（IRS）应用于由多天线接收器支持的上行非正交多址接入（NOMA）网络。我们通过在单位模和实际反射条件下优化IRS反射模式，最大化IRS辅助NOMA网络的和速率。对于中等规模的IRS，我们通过在秩松弛后求解行列式最大化（max-det）问题，得到最优和速率的上界，这也通过高斯随机化得到一个可行解。对于大量的IRS元件，我们应用基于梯度的迭代算法，如布罗伊登-弗莱彻-戈德法布-香农（BFGS）算法和有限内存BFGS算法，其中和速率的梯度以计算高效的形式导出。结果表明，max-det方法在单位模反射下提供了接近最优的性能，而基于梯度的迭代算法在实际反射的大尺寸IRS的性能和复杂度方面表现出优势。
