A novel near-field transmission framework is proposed for dynamic metasurface antenna (DMA)-enabled non-orthogonal multiple access (NOMA) networks. The base station (BS) exploits the hybrid beamforming to communicate with multiple near users (NUs) and far users (FUs) using the NOMA principle. Based on this framework, two novel beamforming schemes are proposed. 1) For the case of the grouped users distributed in the same direction, a beam-steering scheme is developed. The metric of beam pattern error (BPE) is introduced for the characterization of the gap between the hybrid beamformers and the desired ideal beamformers, where a two-layer algorithm is proposed to minimize BPE by optimizing hybrid beamformers. Then, the optimal power allocation strategy is obtained to maximize the sum achievable rate of the network. 2) For the case of users randomly distributed, a beam-splitting scheme is proposed, where two sub-beamformers are extracted from the single beamformer to serve different users in the same group. An alternating optimization (AO) algorithm is proposed for hybrid beamformer optimization, and the optimal power allocation is also derived. Numerical results validate that: 1) the proposed beamforming schemes exhibit superior performance compared with the existing imperfect-resolution-based beamforming scheme; 2) the communication rate of the proposed transmission framework is sensitive to the imperfect distance knowledge of NUs but not to that of FUs.

翻译：针对动态超表面天线（DMA）赋能的非正交多址接入（NOMA）网络，提出了一种新颖的近场传输框架。基站（BS）利用混合波束赋形技术，基于NOMA原理与多个近端用户（NU）和远端用户（FU）进行通信。在该框架基础上，提出了两种新颖的波束赋形方案：1) 针对分组用户分布于相同方向的情况，开发了波束转向方案。引入波束模式误差（BPE）指标来表征混合波束赋形器与理想波束赋形器之间的差距，并提出一种双层算法，通过优化混合波束赋形器以最小化BPE。随后推导了最优功率分配策略，以最大化网络的总可达速率。2) 针对用户随机分布的情况，提出了波束分裂方案，从单个波束赋形器中提取两个子波束赋形器，为同一组内的不同用户提供服务。提出了交替优化（AO）算法用于混合波束赋形器优化，并推导了最优功率分配方案。数值结果验证了：1) 所提波束赋形方案相比现有基于非理想分辨率的波束赋形方案具有更优性能；2) 所提传输框架的通信速率对NU的非理想距离信息敏感，而对FU的该信息不敏感。