Distance-Angle Joint Multiple Access for Far-Field MIMO-OFDM via Frequency Diverse Array

Space division multiple access (SDMA) with massive MIMO enhances system capacity through angular user differentiation but requires impractical large-scale arrays for spatial resolution in ultra-dense networks. While near-field location division multiple access (NLDMA) exploits spherical wave propagation to partition channel resources across angle and distance, extending this capability to the far-field remains challenging. This paper proposes far-field location division multiple access (FLDMA), a novel scheme integrating frequency diverse arrays (FDA) into MIMO-OFDM systems to enable two-dimensional resource partitioning. By adapting the inherent cyclic prefix (CP) of OFDM to FDA-induced propagation delays, FLDMA preserves subcarrier orthogonality while maintaining backward compatibility. A random permutation frequency offset design decouples angle-distance dependencies in steering vectors, achieving asymptotic orthogonality and inter-user interference suppression. Simulations demonstrate FLDMA’s spectral efficiency gains of 75% over SDMA in narrow-sector scenarios, scaling with user density. Notably, FLDMA asymptotically approaches the MIMO capacity upper bound in single-path channels without relying on rich scattering environments. These results position FLDMA as a scalable solution for 6G ultra-dense networks and high-frequency communications.