In recent years, thanks to the advances in meta-materials, the concept of continuous-aperture MIMO (CAP-MIMO) is reinvestigated to achieve improved communication performance with limited antenna apertures. Unlike the classical MIMO composed of discrete antennas, CAP-MIMO has a quasi-continuous antenna surface, which is expected to generate any current distribution (i.e., pattern) and induce controllable spatial electromagnetic (EM) waves. In this way, the information is directly modulated on the EM waves, which makes it promising to approach the ultimate capacity of finite apertures. The pattern design is the key factor to determine the communication performance of CAP-MIMO, but it has not been well studied in the literature. In this paper, we develop pattern-division multiplexing (PDM) to design the patterns for CAP-MIMO. Specifically, we first study and model a typical multi-user CAP-MIMO system, which allows us to formulate the sum-rate maximization problem. Then, we develop a general PDM technique to transform the design of the continuous pattern functions to the design of their projection lengths on finite orthogonal bases, which can overcome the challenge of functional programming. Utilizing PDM, we further propose a block coordinate descent (BCD) based pattern design scheme to solve the formulated sum-rate maximization problem. Simulation results show that, the sum-rate achieved by the proposed scheme is higher than that achieved by benchmark schemes, which demonstrates the effectiveness of the developed PDM for CAP-MIMO.

翻译：近年来，得益于超材料技术的进步，连续孔径MIMO（CAP-MIMO）概念被重新研究，以在有限天线孔径下实现更优的通信性能。与由离散天线组成的经典MIMO不同，CAP-MIMO具有准连续天线表面，能够生成任意电流分布（即模式）并产生可控的空间电磁波。通过这种方式，信息直接调制在电磁波上，使其有望逼近有限孔径的极限容量。模式设计是决定CAP-MIMO通信性能的关键因素，但现有文献对此研究尚不充分。本文提出模式分割复用（PDM）技术用于CAP-MIMO的模式设计。具体而言，我们首先研究并建模典型的多用户CAP-MIMO系统，从而构建和速率最大化问题。随后，我们发展出通用的PDM技术，将连续模式函数的设计转化为其在有限正交基上的投影长度设计，从而克服函数式编程的挑战。基于PDM，我们进一步提出一种基于块坐标下降法（BCD）的模式设计方案，以求解所构建的和速率最大化问题。仿真结果表明，所提方案获得的和速率优于基准方案，验证了所开发的PDM技术在CAP-MIMO中的有效性。