Continuous-Aperture MIMO for Electromagnetic Information Theory
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In recent years, 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 continuous antenna surface, which is expected to generate any current distribution (i.e., pattern) and induce controllable spatial electromagnetic waves. In this way, the information can be modulated on the electromagnetic waves, which makes it promising to approach the ultimate capacity of finite apertures. The pattern design is the key factor to determine the system performance of CAP-MIMO, but it has not been well studied in the literature. In this paper, we propose the pattern-division multiplexing to design the patterns for CAP-MIMO. Specifically, we first derive the system model of a typical CAP-MIMO system, which allows us to formulate the capacity maximization problem. Then we propose a general pattern-division multiplexing technique to transform the design of continuous pattern functions to the design of their projection lengths on finite orthogonal bases, which is able to overcome the design challenge of continuous functions. Based on this technique, we further propose an alternating optimization based pattern design scheme to solve the formulated capacity maximization problem. Simulation results show that, the capacity achieved by the proposed scheme is about 260 that achieved by the benchmark scheme, which demonstrates the effectiveness of the proposed pattern-division multiplexing for CAP-MIMO.
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