Orbital angular momentum (OAM) mode multiplexing has the potential to achieve high spectrum-efficiency communications at the same time and frequency by using orthogonal mode resource. However, the vortex wave hollow divergence characteristic results in the requirement of the large-scale receive antenna, which makes users hardly receive the OAM signal by size-limited equipment. To promote the OAM application in the next 6G communications, this paper proposes the cooperative OAM wireless (COW) communication scheme, which can select the cooperative users (CUs) to form the aligned antennas by size-limited user equipment. First, we derive the feasible radial radius and selective waist radius to choose the CUs in the same circle with the origin at the base station. Then, based on the locations of CUs, the waist radius is adjusted to form the receive antennas and ensure the maximum intensity for the CUs. Finally, the cooperative formation probability is derived in the closed-form solution, which can depict the feasibility of the proposed COW communication scheme. Furthermore, OAM beam steering is used to expand the feasible CU region, thus achieving higher cooperative formation probability. Simulation results demonstrate that the derived cooperative formation probability in mathematical analysis is very close to the statistical probability of cooperative formation, and the proposed COW communication scheme can obtain higher spectrum efficiency than the traditional scheme due to the effective reception of the OAM signal.

翻译：轨道角动量（OAM）模式复用利用正交模式资源，具有在相同时间和频率下实现高频谱效率通信的潜力。然而，涡旋波的空心发散特性导致需要大规模接收天线，这使得用户难以通过尺寸受限的设备接收OAM信号。为促进OAM在下一代6G通信中的应用，本文提出协作式OAM无线（COW）通信方案，该方案能够选择协作用户（CUs），通过尺寸受限的用户设备形成对齐的天线阵列。首先，我们推导了可行的径向半径和可选束腰半径，以在基站为原点的同一圆周上选择CUs。随后，基于CUs的位置调整束腰半径以形成接收天线阵列，并确保CUs处的信号强度最大化。最后，以闭合形式解推导了协作形成概率，该概率能够描述所提COW通信方案的可行性。此外，通过采用OAM波束导向来扩展可行的CU区域，从而实现更高的协作形成概率。仿真结果表明，数学分析中推导的协作形成概率与协作形成的统计概率非常接近，并且由于有效接收了OAM信号，所提出的COW通信方案相比传统方案能够获得更高的频谱效率。